System and method for decontaminating a work area having radioactive debris

Abstract

System and methods for controlling contamination at a work area having toxic and / or radioactive debris is provided. The system comprises: a ventilation system for ventilating a volume defined by a component of a nuclear reactor. The ventilation system includes an inlet for receiving air from the volume; a ventilation system filter; and a suction blower in fluid communication with the inlet and the ventilation system filter. The suction blower forces air from the volume into the inlet and to the ventilation system filter. A controller controls a pressure within the volume to a setpoint below an exterior pressure outside the volume where the setpoint selected to maintain a velocity of air moving out of the volume below a threshold velocity. The threshold velocity prevents a capture velocity from being reached to prevent the toxic and / or radioactive debris from entering the ventilation system.

Description

SYSTEM AND METHOD FOR DECONTAMINATING A WORK AREA HAVING RADIOACTIVE DEBRISCROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

[0001] The present application claims priority to U.S. provisional patent application no. 63 / 627,397 filed on January 31 , 2024, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD

[0002] The disclosure relates generally to decommissioning a nuclear reactor, and more particularly to decontamination of a work area during decommissioning of a nuclear reactor.BACKGROUND

[0003] A nuclear reactor has a limited operational life. For example, second generation CANDUTM-type reactors (“CANada Deuterium Uranium”) are designed to operate for approximately 25 to 30 years. After this time, nuclear reactor may in some instances be decommissioned. Nuclear reactor maintenance and decommissioning processes include removal of a large number of reactor components and include various other activities, such as shutting down the reactor, preparing the vault, and installing material handling equipment and various platforms and equipment supports. The removal process can also include removing closure plugs and positioning hardware assemblies, disconnecting feeder assemblies, severing bellows, removing end fittings, releasing and removing calandria tube inserts, severing and removing pressure tubes, removing calandria tube, and removing the calandria. Many of the components that are removed may be radioactive and require special handling. In particular, components that are removed or refurbished may generate toxic and / or radioactive gas and debris, e.g. aerosolized particles which need to be collected in ventilation systems to prevent contamination of a work area. However, these ventilation systems may spread the toxic and / or radioactive gas or debris around the area of the work area due to ineffective design.SUMMARY

[0004] Systems and method for controlling radioactive and / or toxic debris or gaseous material at a work area are described in this disclosure. These systems and methods may be employed at a nuclear reactor site.

[0005] In one aspect, the disclosure describes a system for controlling contamination at a work area having at least one of toxic and / or radioactive debris. The system comprises: a ventilation system for ventilating a volume defined by a component of a nuclear reactor, the ventilation system comprising: an inlet for receiving air comprising the contamination from the volume; a ventilation system filter for filtering at least one of radioactive and toxic debris received from the volume; and a first suction blower in fluid communication with the inlet and the ventilation system filter, the first suction blower configured to force air from the volume into the inlet and to the ventilation system filter; and a controller configured to: control a pressure within the volume to a setpoint below an exterior pressure outside the volume defined by the component, the setpoint selected to maintain a velocity of air moving out of the volume below a threshold velocity, wherein when the pressure within the volume is above the setpoint, the controller sends data to at least one of the first suction blower and a flow balancing valve to increase a flow rate of air into the inlet and the ventilation system, wherein when the pressure within the volume is below setpoint, the controller sends data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air into the inlet and to the ventilation system filter.

[0006] In an embodiment, the setpoint is a range between a first pressure threshold and a second pressure threshold, wherein the controller is configured to: control the pressure within the volume within the range, wherein the first pressure threshold is greater than the second pressure threshold, wherein when the pressure within the volume is above the first pressure threshold, the controller sends data to at least one of the first suction blower and the flow balancing valve to increase the flow rate of air into the inlet and the ventilation system, wherein when the pressure within the volume is below the second pressure threshold, the controller sends data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air into the inlet and to the ventilation system filter, wherein pressure within the volume changes based on a flow rate of air entering the volume and a second flow rate of air leaving the volume, and wherein the second pressure threshold is selected to maintain the velocity of air passing out of the volume below the threshold velocity.

[0007] In an embodiment, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller isconfigured to send data to open a valve to exhaust air received from the ventilation system to a vacuum container.

[0008] In an embodiment, the system comprises: a vacuum collection system defined within the volume, the vacuum collection system comprising: a first conduit having a first end configured for coupling with at least one of a vacuum head, and a tool for refurbishing or decommissioning a nuclear reactor; a first filter for filtering radioactive debris received from the work area, the first filter coupled to a second end of the conduit, and the first filter positioned proximate to the first end to provide a desired length of the first conduit; and a second conduit coupling the first filterto a second filter for filtering radioactive debris from the work area; a second suction blower in fluid communication with the first conduit, the first filter, the second conduit, and the second filter, the second suction blower configured to force air external to the first end of the first conduit to enter the first end to move the radioactive debris from the first end to at least one of the first filter and the second filter; and an outlet in fluid communication with the first and second suction blowers for discharging the air received from the second filter. In an embodiment, when the pressure within the volume is below the setpoint, the controller sends data to the first suction blower to decrease the flow rate of air into the inlet, and to the second suction blower to decrease a flow rate of air into the first end. In another embodiment, when the pressure within the volume is below the setpoint, the controller sends data to the flow balancing valve to reduce a flow of air into at least one of inlet and the first end.

[0009] In an embodiment, the velocity of the air passing out of the volume is determined by at least one of: a velocity meter in the vacuum system, a velocity meter in the ventilation system, pressure drop across the first suction blower, and pressure drop across the second suction blower.

[0010] In an embodiment, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller is configured to send data to stop air flow from the vacuum collection system and / or reduce air flow through the first suction blower.

[0011] In an embodiment, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller isconfigured to send data to a plurality of control valves to stop air flow through the ventilation system and the vacuum collection system.

[0012] In an embodiment, when the first suction blower is in operation, a first flow path is defined by the volume, the inlet, the ventilation system filter, and the outlet, and when the second suction blower is in operation, a second flow path is defined by the first end of the first conduit, the first conduit, the first filter, the second conduit, the second filter, and the outlet.

[0013] In an embodiment, the desired length of the first conduit is in a range of 0.5-20 meters, preferably 0.5-10 meters.

[0014] In an embodiment, the outlet is at least one of a vacuum container, and a D2O recovery system.

[0015] In an embodiment, the first filter comprises radioactive shielding.

[0016] In an embodiment, the first and second filter comprises at least one of a pre-filter a High Efficiency Particulate Air (HEPA) filter, a Ultra-Low Particulate Air (ULPA) filter; and a magnetic collection system comprising magnets for collecting ferrous metals in the debris.

[0017] In an embodiment, the first filter is configured to collect a portion of the debris having a size of about at least 0.3 microns.

[0018] In an embodiment, the second filter comprises the HEPA filter, the ULPA filter; and the magnetic collection system positioned in series.

[0019] In an embodiment, the second filter is configured to collect a portion of the particles having a size of about at least 0.3-microns.

[0020] In an embodiment, the system comprising radiation sensors for sensing radiation at the first filter, the second filter and / or at the work area. In an embodiment, the controller is in communication with the radiation sensor, the controller configured to actuate an alarm when the radiation sensor increases above a threshold radiation value.

[0021] In an embodiment, the controller is in communication with a flow meter and a flow control valve for controlling a velocity of air through first end of the first conduit.

[0022] In an embodiment, the controller is in communication with pressure sensors for measuring pressure drop across at least one of the first filter and second filter, the controller configured to actuate an alarm when the pressure drop increases above a threshold pressure value.

[0023] In an embodiment, the controller in communication with the second suction blower for controlling a velocity of airthrough first end ofthe first conduit. In an embodiment, the second suction blower is fluidly connected to only the first and second filters.

[0024] In an embodiment, the system comprises a catalytic converter to convert gaseous contaminants received from the work area to liquid forms.

[0025] In an embodiment, the system comprises a heater for evaporating liquid droplets and vapour entraining radioactive and / or toxic debris.

[0026] In an embodiment, the system comprises a radiation sensor on an exhaust ofthe ventilation system, wherein when the controller receives data indicating a threshold radiation level sensed by the radiation sensor has been reached, the setpoint is raised to a minimum pressure differential (dP) below the exterior pressure outside the volume defined by the component.

[0027] In an embodiment, the component is a vault of a nuclear reactor, a calandria vessel, a reactivity mechanisms deck, or a calandria relief duct.

[0028] Embodiments may include combinations of the above features.

[0029] In another aspect, the disclosure describes a method for controlling contamination at a work area having at least one of toxic and / or radioactive debris. The method comprises: providing a system of according to this disclosure; receiving data indicative of the pressure within the volume and the velocity of air moving out of the volume; sending data to at least one ofthe first suction blower and the flow balancing valve to increase the flow rate of air from the volume into the inlet and to the ventilation system filter if the pressure within the volume is above the setpoint and if the velocity of air moving out of the volume is below the threshold velocity, sending data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air from the volume into the inlet and to the ventilation system filter if the velocity of air moving out of the volume is above the threshold velocity.

[0030] In an embodiment, the method comprises: providing the system according to this disclosure comprising: a vacuum collection system defined within the volume, the vacuum collection system comprising: a first conduit having a first end configured for coupling with at least one of a vacuum head, and a tool for refurbishing or decommissioning a nuclear reactor; a first filter for filtering radioactive debris received from the work area, the first filter coupled to a second end of the conduit, and the first filter positioned proximate to the first end to provide a desired length of the first conduit; and a second conduit coupling the first filterto a second filter for filtering radioactive debris from the work area; and a second suction blower in fluid communication with the first conduit, the first filter, the second conduit, and the second filter, the second suction blower configured to force air external to the first end of the first conduit to enter the first end to move the radioactive debris from the first end to at least one of the first filter and the second filter; and an outlet in fluid communication with the first and second suction blowers for discharging the air received from the second filter; the method further comprising: suctioning the debris from the work area through the first end of the first conduit and the inlet; filtering the debris from the air with the first and second filters, and the ventilation system filter; and discharging the air.

[0031] In an embodiment, the method comprises: receiving data indicative of the pressure within the volume and the velocity of air moving out of the volume; sending data to at least one of the first suction blower and the flow balancing valve to increase the flow rate of air from the volume into the inlet and to the ventilation system filter if the pressure within the volume is above the setpoint and if the velocity of air moving out of the volume is below the threshold velocity, sending data to at least one of the first suction blower, the flow balancing valve, and the second suction blower to decrease the flow rate of air from the volume into at least one of the ventilation system and the vacuum collection system if the velocity of air moving out of the volume is above the threshold velocity.

[0032] In an embodiment, the threshold velocity is set based on an observed velocity of air moving into the ventilation system and vacuum collection system when there is no observed migration of the at least one toxic and / or radioactive debris.

[0033] In an embodiment, the threshold velocity is set based on calculated velocity to minimize contamination transport, the threshold velocity value determined based onvapour percentage, pressure, temperature, cross-sectional area of at least one opening to the volume, the opening defined by the component of the nuclear reactor.

[0034] In an embodiment, the threshold velocity is set based on a measured velocity of air exiting a combined outlet of the ventilation system and vacuum collection system when the radiation detected in at least one of the volume the vacuum collection system, and the ventilation system is equal to or less than a threshold radiation value.

[0035] In an embodiment, the setpoint is in a range of 2 to 6 psi below the exterior pressure outside the volume, and the threshold velocity is the velocity of air moving out of the volume when the pressure is below 6 psi.

[0036] In an embodiment, the velocity of air moving out of the volume is determined by at least one of: the pressure drop across the first suction blower, a flow meter, and a velocity meter.

[0037] In an embodiment, the method comprises sensing radiation emitted from at least one of the first filter, the second filter, and the work area, and actuating an alarm when the radiation increases above a threshold radiation value.

[0038] In an embodiment, the method comprises replacing the first filter with a third filter when the radiation increases above the threshold radiation value at the first filter.

[0039] In an embodiment, the method comprises replacing the second filter with a fourth filter when the radiation increases above the threshold radiation value at the second filter.

[0040] In an embodiment, the method comprises controlling a velocity of air through the first end of the first conduit to a velocity for minimizing contamination transport.

[0041] In an embodiment, the method comprises measuring pressure drop across at least one of the first filter and second filter, and actuating an alarm when the pressure drop increases above a threshold pressure value. In an embodiment, the method comprises replacing the first filter with a third filter when the pressure drop increases above the threshold pressure value across the first filter. In another embodiment, the method comprises replacing the second filter with a fourth filter when the pressure drop increases above the threshold pressure value across the second filter.

[0042] Embodiments may include combinations of the above features.

[0043] Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.DESCRIPTION OF THE DRAWINGS

[0044] Reference is now made to the accompanying drawings, in which:

[0045] FIG. 1 is a perspective view of a CANDUTM-type reactor.

[0046] FIG. 2A is a cutaway view of a CANDUTM-type nuclear reactor fuel channel assembly.

[0047] FIG. 2B is a perspective view of a platform, work table and a calandria tube insert removal tool adjacent a face of the CANDUTM-type reactor, according to an embodiment.

[0048] FIG. 3 is a schematic view of an example cutting tool inserted into a calandria vessel of the reactor shown in FIG. 1.

[0049] FIG. 4 is a schematic view of an example system for decontaminating a work area having radioactive debris.

[0050] FIG. 5 is a schematic view of an example air cleaner system connected to the system shown in FIG. 4.

[0051] FIG. 6 is a schematic flowchart of an example method for decontaminating a work area having radioactive debris.

[0052] FIG. 7 is a schematic flowchart of an example control system for decontaminating a work area having radioactive debris.DETAILED DESCRIPTION

[0053] Before any embodiments are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0054] During decommissioning and / or maintenance activities at a nuclear reactor site, many of components that are removed may be radioactive and require special handling, and may have potentially mobile contamination in the form of gas, liquid (vapour), and solids (dust). Mobile contamination may be a concern both in that it may be already toxicor radioactive, but it may also be activated by future events forming a future hazard. Ventilation system design for these environment is complex given the systems have to control spread of contamination from a work area, including of gaseous products that may be off gassing from systems, structures or components being worked on. In particular, the varying forms and amounts of contaminants to control, along with the challenges in detection, and the typical variable opening sizes and dimensions into environments, e.g. vessels, pipes, and / or reactors whose atmosphere is desired to be controlled make decontamination control a complex challenge. This disclosure relates to both overall envelope control of the atmosphere for a volume defined by a component of a nuclear reactor to be ventilated for decontamination control, local control of potential sources of contamination within the space, and control and cleaning of the inlet to and exhaust from the volume. Legacy systems often create significant local air velocities when inlet leakage gaps are small and significant air currents when inlet leakage gaps are large which mobilises and spreads particulate.

[0055] A commonly relied upon part of ventilation systems in an environment comprising radioactive and / or toxic materials, is that the ventilation system uses vacuum pressure to prevent contamination from being released from work areas, or in some cases areas of a nuclear reactor station undergoing refurbishment or decommissioning. Ventilation is also expected to control movement of debris or gaseous particles within the area. For normal operation it may be straightforward to size ventilation systems to control air movement out of contaminated spaces by keeping the spaces at a lower pressure than surrounding spaces by extracting and filtering air to cover leakage gaps into the area and as part of the exhaust dealing with potential contaminants that may be produced or have existed in that area. However, such a negative pressure setup may result in contaminants being drawn into or spread around a larger area that may cause further difficulties accessing and decontaminating the larger areas. This problem has been experienced in nuclear retube and decommissioning operations.

[0056] DEFINITIONS

[0057] Although terms such as “maximize”, “minimize” and “optimize” may be used in the present disclosure, it should be understood that such term may be used to refer to improvements, tuning and refinements which may not be strictly limited to maximal, minimal or optimal.

[0058] The term “connected” or "coupled to" may include both direct coupling (in which two elements that are coupled to each other and contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

[0059] The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

[0060] Terms such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges. In the same manner, all ratios recited herein also include all sub-ratios falling within the broader ratio.

[0061] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0062] The term "about" can refer to a variation oft 5%, ± 10%, ± 20%, or± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" can include one or two integers greater than and / or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

[0063] The term “component of a nuclear reactor” as used herein refers to parts of a nuclear reactor building that may be contaminated by radioactive and / or toxic materials, such as a nuclear reactor vault, calandria, reactivity mechanisms deck, fuel building, reactor building, etc.

[0064] Aspects of various embodiments are described through reference to the drawings.

[0065] FIG. 1 is a perspective of a reactor core of a CANDUTM-type reactor6. The reactor core is typically contained within a vault that is sealed with an air lock for radiation control and shielding. Although aspects are described with particular reference to the CANDU™- type reactor 6 for convenience, the disclosure is not limited to CANDUTM-type reactors, and may be useful outside this particular field as well. A generally cylindrical vessel,known as the calandria vessel 10 of the CANDUTM-type reactor 6, contains a heavy-water moderator. The calandria vessel 10 has an annular shell 14 and a tube sheet 18 at a first end 22 and a second end 24. The tube sheets 18 include a plurality of apertures (referred to herein as bores 19) that each accept a fuel channel assembly 28. As shown in FIG. 1 , a number of fuel channel assemblies 28 pass through the tube sheets 18 of calandria vessel 10 from the first end 22 to the second end 24.

[0066] As in the illustrated embodiment of Figs. 1 and 2A, in some embodiments the reactor core is provided with two walls at each end 22, 24 of the reactor core: an inner wall defined by the tube sheet 18 at each end 22, 24 of the reactor core, and an outer wall 64 (often referred to as a “end shield”) located a distance outboard from the tube sheet 18 at each end 22, 24 of the reactor core. A lattice tube 65 spans the distance between the tube sheet 18 and the end shield 64 at each pair of bores 19 (i.e., in the tube sheet 18 and the end shield 64, respectively).

[0067] FIG. 2A is a cutaway view of one fuel channel assembly 28 of the reactor core illustrated in FIG. 1 . As illustrated in FIG. 2A, each fuel channel assembly 28 includes a calandria tube (“CT”) 32 surrounding other components of the fuel channel assembly 28. The CTs 32 each span the distance between the tube sheets 18. Also, the opposite ends of each CT 32 are received within and sealed to respective bores 19 in the tube sheets 18. In some embodiments, a rolled joint insert, for example calandria tube insert 34, is used to secure the CT 32 to the tube sheet 18 within the bores 19. A pressure tube (“PT”) 36 forms an inner wall of the fuel channel assembly 28. The PT 36 provides a conduit for reactor coolant and fuel bundles or assemblies 40. The PT 36, for example, generally holds two or more fuel assemblies 40, and acts as a conduit for reactor coolant that passes through each fuel assembly 40. An annulus space 44 is defined by a gap between each PT 36 and its corresponding CT 32. The annulus space 44 is normally filled with a circulating gas, such as dry carbon dioxide, helium, nitrogen, air, or mixtures thereof. One or more annulus spacers or garter springs 48 are disposed between the CT 32 and PT 36. The annulus spacers 48 maintain the gap between the PT 36 and the corresponding CT 32, while allowing passage of annulus gas through and around the annulus spacers 48.

[0068] As also shown in FIG. 2A, each end of each fuel channel assembly 28 is provided with an end fitting assembly 50 located outside of the corresponding tube sheet 18. Eachend fitting assembly 50 includes an end fitting body 57 and an end fitting liner 58. At the terminal end of each end fitting assembly 50 is a closure plug 52. Each end fitting assembly 50 connects to a feeder assembly 54. The feeder assemblies 54 feed reactor coolant into or remove reactor coolant from the PTs 36 via feeder tubes 59 (FIG. 1). In particular, for a single fuel channel assembly 28, the feeder assembly 54 on one end of the fuel channel assembly 28 acts as an inlet feeder, and the feeder assembly 54 on the opposite end of the fuel channel assembly 28 acts as an outlet feeder. As shown in FIG. 2A, the feeder assemblies 54 can be attached to the end fitting assemblies 50 using a coupling assembly 56 including a number of screws, washers, seals, and / or other types of connectors. The lattice tube 65 (described above) encases the connection between the end fitting assembly 50 and the PT 36 containing the fuel assemblies 40. Shielding ball bearings 66 and cooling water surround the exterior of the lattice tubes 65, which provides additional radiation shielding.

[0069] A positioning hardware assembly 60 and bellows 62 are also coupled to each end fitting assembly 50. The bellows 62 allows the fuel channel assemblies 28 to move axially - a capability that can be important where fuel channel assemblies 28 experience changes in length over time, which is common in many reactors. The positioning hardware assemblies 60 can be used to set an end of a fuel channel assembly 28 in either a locked configuration that fixes the axial position, or an unlocked configuration. The positioning hardware assemblies 60 are also coupled to the end shield 64. The illustrated positioning hardware assemblies 60 each include a rod having an end that is received in a bore of the respective end shield 64. In some embodiments, the rod end and the bore in the end shield 64 are threaded. Again, it should be understood that although a CANDUTM-type reactor is illustrated in FIGS. 1-2A, the invention may also apply to other types of reactors, including reactors having components that are similar to those illustrated in FIGS. 1-2A.

[0070] FIG. 2B illustrates one embodiment of a heavy work table (“HWT”) 96 installed on a retube tooling platform (“RTP”) 95 adjacent the end 24 of the nuclear reactor. A similar HWT can be installed adjacent the end 22 of the nuclear reactor. The HWT 96 and any tools mounted on the HWT are controlled by a control station (not shown).

[0071] As shown in FIG. 3, calandria cutting tool 100 may be mounted on the HWT 96 and is positioned to remove calandria tube inserts 34 from tube sheet 18 at the end 24.The control of the position of the calandria cutting tool 100 with respect to the end shield 64 and operation of the tool 100 may occur from the control station. Specifically, the operator can control the height of the RTP 95 along axis Y, the location of the cutting tool 100 on the HWT 96 along axis X and the pitch with respect to the end shield 64 to orient axis Z to be perpendicular to the end shield 64. In some embodiments, the height of RTP 95 may be adjusted by ball screws, for example, by way of one ball screw at each corner of RTP 95.

[0072] When the cutting tool 100 is aligned with the selected opening in the end shield 64, the operator can insert the calandria cutting tool 100 into the appropriate fuel channel along axis Z. The cutting tool 100 can include any number of suitable sensors and / or cameras to verify that the cutting tool 100 is properly aligned with the respective opening in the end shield 64. Once inserted, cutting tool 100 may commence cutting operations as described below. Due to the high radiation fields in calandria vessel 10, cutting operations may be performed remotely. As such, a controller 2001 may be provided for controlling the movement cutting tool 100, worktable 96, platform 95, gripper 103, moveable contamination barrier 104, etc. Controller 2001 may also be coupled to sensors, flow controllers, and suction blowers of the ventilation systems for decontaminating work areas according to this disclosure. Example work areas may include cutting tool 100, worktable 96, etc.

[0073] FIG. 3 illustrates a schematic view of cutting tool 100 inserted into calandria vessel 10. Calandria 10 comprises an A-face opposing a C-face, each having an end shield 64. Lateral sides of calandria 10 are referred to as D-face and B-face (no shown). As shown in FIG. 3, cutting tool 100 may be position on worktable 96 on platform 95. Crane 101 may be provided for handling of segmented calandria vessel 10 pieces and may be installed on the Reactivity Mechanisms (RM) Deck 102. A gripper 103 may extend from RM Deck 102 which can be deployed inside calandria vault 1 1 to grip segmented portions of calandria vessel 10. Calandria vault 1 1 may also be referred to as a shield tank or shield vault. Gripper 103 may extend into vault 11 through holes cut in the vault 1 1 to permit access to calandria 10. In some embodiment, gripper 103 may extend into vault 11 and calandria vessel 10 through ports in reactivity mechanism deck 102 which allow vertical access to calandria vessel 10. In an example the ports may include the viewing port, liquid zone control unit port, flux detector port, liquid injection shut down nozzle,reactivity control unit nozzles, etc. Cutting calandria vessel 10 inside vault 11 may allow containment of debris and / or cutting by-products, such as dust and particles, from migrating outside vault 11. During operation of cutting tool 100, the interior of vault 11 may be kept at vacuum pressure relative to the exterior of vault 11 , e.g. by an active ventilation system (not shown).

[0074] As cutting tool 100 cuts / segments components of calandria vessel 10, gripper 103 may couple to the segmented components and move them to waste collection container 106. Remotely controlled demolition robots (not shown) may also be positioned inside the calandria vault 11 to assist in handling of the segmented portion of calandria vessel10. Holes may also be cut by cutting tool 100 in calandria vessel 10 for handling segmented pieces of calandria vessel 10. Cutting tool 100 may cut calandria vessel 10 using cutting techniques such as plasma arc, laser, waterjet, milling, etc.

[0075] In an embodiment, contamination barriers 104, such as a movable shielding wall or shielding door, may be installed to shield a bottom portion of the calandria vault 11 after it is opened. Contamination barrier 104 may be made from a material that reduces or prevents radioactivity from passing through the barrier. Barrier 104 may be installed prior to demolishing process. When necessary (during removal of segmented portion of calandria vessel 10 from inside calandria vault 11 ), to isolate the operating area, existing shielding walls between Fueling Machine (FM) Maintenance rooms and Transfer corridor could be activated. As an alternative, large shielding doors between FM Room and FM Maintenance rooms could be activated. In an embodiment, before the calandria vault 11 is drained, shielding walls 104 may be installed.

[0076] To access the inside of calandria vault 11 , a wall of calandria vault 11 may be removed. Barrier 104 may be installed prior to demolishing of the wall of calandria vault11.

[0077] As described above, platform 95 may be installed on both reactor faces to provide Y-direction movements for the tools installed on it. Worktable 96 may be installed on the platform 95 to provide X-direction movements for the tools installed on it.

[0078] A waste collection trolley 105 may be positioned inside vault 11 underneath of calandria 10. Waste collection containers 106, such as waste transfer flasks, may be positioned on trolley 105 to collect segmented pieces. During segmenting of calandria10, barrier 104 may be positioned to close the opening in vault 11 . When container 106 is full, barrier 104 may be moved / opened such that container 106 may be moved out to a segmentation room, where waste may be further segmented, assayed, and packed.

[0079] FIGs. 4 and 5 shows schematic diagrams illustrating a system 1 for controlling contamination a work area having at least one of toxic and / or radioactive debris. As shown in FIG. 5, system 1 comprises a ventilation system 500 for ventilating a volume 502 defined by a component of a nuclear reactor. Ventilation system 500 comprises an inlet 501 a, 501 b, 501 c for receiving air comprising the contamination from volume 502 which is in fluid communication with a ventilation system filter 503 for filtering radioactive and / or toxic debris received from volume 502. A first suction blower 513 is in fluid communication with the inlet 501 a, 501 b, 501 c and the ventilation system filter 503. First suction blower 513 may be configured to force air from volume 502 into inlet 501 a, 501 b, 501 c and to ventilation system filter 503.

[0080] System 1 may comprise a controller 2001 configured to: control a pressure within the volume to a setpoint below an exterior pressure outside volume 502 defined by a component of the nuclear reactor. The setpoint may be selected to maintain a velocity of air moving out of volume 502 below a threshold velocity. In an example, the threshold velocity may be set based on an observed velocity of air moving into the ventilation system and vacuum collection system when there is no observed migration of the at least one toxic and / or radioactive debris. The observed velocity may be a velocity measured by sensor(s). In an embodiment, the threshold velocity is the measured velocity of air exiting volume 502, e.g. measured on the outlets of systems 400, 500, when the radiation detected in at least one of volume 502, air in vacuum collection system 400, and air in ventilation system 500 is equal to or less than a threshold radiation value. In another embodiment, the threshold velocity is the measured velocity of air entering volume 502, e.g. measured on the air inputs to systems 400, 500, when the radiation detected in at least one of volume 502, air in vacuum collection system 400, and air in ventilation system 500 is equal to or less than a threshold radiation value. When the pressure within volume 502 is above the setpoint, controller 2001 may send data to at least one of the first suction blower 513 and a flow balancing valve, e.g. flow control valves 410, to increase a flow rate of air into the inlet 501 a, 501 b, 501 c and the ventilation system 500. When the pressure within the volume is below the setpoint, controller 2001 sends data to at leastone of first suction blower 513 and flow balancing valves, e.g. flow control valves 410, to decrease the flow rate of air into inlet 501 a, 501 b, 501 c and to the ventilation system filter 503.

[0081] In an embodiment of system 1 , the setpoint is a range between a first pressure threshold and a second pressure threshold, where the controller is configured to: control the pressure within volume 502 within the range. In an example, the first pressure threshold is greater than the second pressure threshold such that the first pressure threshold operates as a high pressure limit and the second pressure threshold operates as the low pressure limit. Both the first pressure threshold and the second pressure threshold are below the pressure exterior to volume 502. Controller 2001 may be configured to control the pressure within volume 2001 within the range between the first pressure threshold and a second pressure threshold. When the pressure within volume 502 is above the first pressure threshold (i.e. the high pressure limit), controller 2001 may send data to at least one of first suction blower 513 and flow balancing valve(s), e.g. flow control valves 410, to increase the flow rate of air into inlet 501 a, 501 b, 501 c and ventilation system 500. When the pressure within volume 502 is below the second pressure threshold, controller 2001 may send data to at least one of first suction blower 513 and the flow balancing valve, e.g. flow control valves 410, to decrease the flow rate of air into inlet 501 a, 501 b, 501 c and to ventilation system filter 503. Pressure within volume 502 may change based on a flow rate of air entering volume 502 and a flow rate of air leaving the volume 502. Air may enter the volume through open doors and access points, openings cut into the component defining the volume during decommissioning or maintenance work, or pipes and / or channel connecting the volume to an exterior environment. Flow rate of air leaving volume 502 may increase, for example, when the flow of air passing through the suction blowers 413, 513 increases. Suction blowers 413, 513 may have variable frequency drives to change suction by increasing or decreasing fan speeds. For example, if the flow rate of air entering the volume increases, the setpoint, i.e. the first pressure threshold, may be exceeded causing suction blower 513 to increase the flow of air out of volume 502 which in turn increases the velocity of air moving into inlet 501 a, 501 b, 501 c. As velocity of air moving into ventilation system 500 increases, velocity draft formation may entrain debris, such as metallic powder caused by cutting and / or maintenance activities on the nuclear reactor, which can be pulled into ventilationsystem 500 and / or accumulate debris within volume 502 to be potentially activated later. Additionally, as the velocity of air moving out of volume 502 increases, the velocity of air entering volume 502 may increase causing velocity draft formation that may entrain debris from outside of volume 502 moving it into volume 502. In an example, air may flow through feeder tube(s) 59, e.g. when the feeder tube 59 is disconnected from the reactor boiler system (not shown), which may cause air from outside volume 502 to enter the feeder tube(s) 59 and mobilize radioactive debris contaminated with alpha radiation from feeder tube(s) 59 to enter volume 502. This airpath coming into volume 502, e.g. defined by the vault, from the feeder tubes may be problematic as debris contaminated with alpha radiation may be difficult to detect. In some examples, alpha radiation is harder to detect than gamma radiation. Accumulation of debris within volume 502 may subsequently compromise reactor performance and cause safety risks during subsequent maintenance activities when the debris becomes radioactively activated during operation of the nuclear reactor. To mitigate against debris accumulation, the second pressure threshold may be selected to maintain the velocity of air passing out of the volume below a threshold velocity.

[0082] In an embodiment, when controller 2001 receives data that radioactivity measured by a sensor 509, which may be positioned on an exhaust line, is above a threshold radiation level, controller 2001 may be configured to send data to open valve 506 to exhaust air received from ventilation system 500 to a vacuum container, e.g. a vessel configured to operate at a vacuum pressure to receive air contamination with radioactive debris.

[0083] In another embodiment, when controller 2001 receives data that radioactivity measured by a sensor 509 indicating a threshold radiation level sensed by the radiation sensor has been reached, the setpoint, i.e. the first pressure threshold, may be raised to a minimum differential pressure (dP) below the exterior pressure outside the volume 502 defined by the component. Controller 2001 may also cause blower 413 to stop air flow to outlet 406. These actions may reduce the amount of air entering systems 400, 500 while maintaining vacuum pressure within volume 502. Action may then be taken by operators to determine the source of radiation sensed by sensor 509. In another embodiment, when controller 2001 receives data that radioactivity measured by a sensor 509 indicating a threshold radiation level sensed by the radiation sensor has beenreached, controller 2001 may cause blower 413 to stop airflow to outlet 406, close control valves 410 on both vacuum collection system 400 and ventilation system 500 to stop (or minimize) air flow through volume 502 to allow operators to determine the source of radiation sensed by sensor 509.

[0084] FIG. 4 shows a schematic diagram illustrating an embodiment of system 1 for controlling contamination at a work area 401 a-401 c having at least one of toxic and / or radioactive debris. Example work areas include work areas at hand held cleaning tool 401 a, retube tool and / or calandria insert removal tool 401 b, volume reduction machine 401 c, feeder platform, reactor building floor, platform 95, worktable 96, etc., each defined by a component of the nuclear reactors, such a the nuclear reactor vault, calandria, calandria relieve ducts, etc.. During maintenance and / or refurbishment activities for nuclear reactors, liquids or gases in the various components of the nuclear reactor may be replaced with air using ventilation-based containment systems set up to control contamination ingress and egress. This replacement may be challenging for volumes in the nuclear reactor that are configured for receiving heavy water as radioactive isotopes which may exist in both gaseous and vapour forms and may have been absorbed into the walls of the structure receiving the heavy water such that the radioactive isotopes may off-gas or defuse out of the structure. Some of these contaminants may need to be changed in form to remove them, e.g. changing from gaseous into liquid phase. To keep operators safe from toxic and / or radioactive debris, a ventilation system 500, and optionally a vacuum suction system 400 within the ventilation system 500, may ventilate volume 502 defined by the component of the nuclear reactor being maintained, refurbished, or decommissioned.

[0085] As shown in FIG. 4, in an embodiment, system 1 may also comprise a vacuum collection system 400. A portion of vacuum collection system 400 may be defined within volume 502 which is defined by a component of a nuclear reactor. Vacuum collection system 400 may comprise a first conduit 402 having a first end 402-1 configured for coupling with a tool at a work areas. Example tools include hand held cleaning tool, e.g. a vacuum head; a tool for refurbishing or decommissioning a nuclear reactor, such a retube tool 401 b or a volume reduction machine 401 c; or other tools such as a calandria tube insert release of remove tool. Example volume reduction machines are described in International Patent Application No. PCT / CA2018 / 050671 (published as WO2018 / 232497A1), and International Patent Application No. PCT / CA2018 / 050671 (Published As WO2018 / 232497), the entire contents of which are hereby incorporated by reference. Example Calandria tube insert release and removal tools are described in International Patent Application No. PCT / CA2018 / 050770 (Published as WO 2018 / 232526A1), the entire contents of which are hereby incorporated by reference.

[0086] System 400 may also comprise a first filter 403 for filtering radioactive debris received from the work areas. First filter 403 may be coupled to a second end 402-2 of the conduit. The first filter 403 may be positioned proximate to first end 402-1 to provide a desired length of the first conduit 402. In an embodiment, first filter 403 is configured to collect a portion of the debris having a size of about at least 0.3 microns. In an example, first filter 403 may be about a 16-gallon drums filter of about 16 inch diameter and 20 inch height. First filter 403 may be placed proximate to the work area, e.g. less than or equal to 30 meters, to minimize the length of the first conduit to limit the length of tubing which transports air comprising unfiltered entrained radioactive debris. If the conduit containing unfiltered entrained radioactive debris or toxic material leaks or ruptures, the debris may potentially spread over a large area if the conduit is long. In addition the debris may settle out in the conduit causing both concentration of radiative sources, and potentially impacting passage through the conduit. Minimizing the length of the first conduit by positioning first filter 403 proximate to a work area may mitigate against leaks, and minimize a potential area affected by a leak, should one occur. In an embodiment, a desired length of first conduit 402 is in a range of 0.5 -20 meters, 0.5-10 meter, and / or 0.5-5 meters. In an embodiment, first filter 403 comprises radioactive shielding.

[0087] System 400 may also comprise a second conduit 405 coupling the first filter 403 to a second filter 404 for filtering radioactive debris from the work area. Second filter 404 may be configured to collect a portion of the debris having a size of about at least 0.12- microns, preferably 0.3-microns. Examiner second filters may be shielded in-line filter assemblies may be about a 65 gallon drum filter having about a 22 inch diameter and 40 inch height. Suction blower 413 may be in fluid communication with first conduit 402, first filter 403, second conduit 405, and second filter 404, to force air external to the first end 402-1 of first conduit 402 to enter the first end 402-1 to move the radioactive debris from the first end to at least one of first filter 403 and second filter 404 where the debris may be separate from the air. Suction blower is configured to provide suction at first end 402-1 to receive debris such as particles and other by-products from cutting, crushing, and dismantling components of a nuclear reactor. In an example, suction blower 413 may provide a suction of at least 15 inch water gauge pressure, preferably about 24 inch water gauge pressure at first end 402-1 .

[0088] In an embodiment, the first and second filters may each comprise at least one of a pre-filter, a High Efficiency Particulate Air (HEPA) filter, a Ultra-Low Particulate Air (ULPA) filter; a magnetic collection system comprising magnets for collecting ferrous metals in the debris. First filter 403 may be sized to be mobilized onto a platform 95, worktable 96, or tool 100. Second filter 404 may have a greater volume and capacity than first filter as it may receive debris from multiple work areas. In an example, second filter 404 may comprise a pre-filter a HEPA filter, ULPA filter; and the magnetic collection system positioned in series.

[0089] An outlet 406 of system 400 may be in fluid communication with the suction blower 413 for discharging the air received from second filter 404. In example, outlet 406 is at least one of a ventilation system of the nuclear reactor building, and a D2O vapour recovery system. Additional filters may be positioned between outlet 406 and first end 402-1 . As shown in FIGs. 4 and 5, suction blower(s) 413, 513 may comprise pre-filters 407 and / or HEPA filters 408 to further filter the debris from the air as it move to outlet 406. When suction blower 413 is in operation, a flow path may be defined by first end 402-1 of first conduit 402, first conduit 402, first filter 403, second conduit 405, second filter 404, and outlet 406. When suction blower 513 is in operation, another flow path may be defined by volume 502, inlet 501 a, b, c, ventilation system filter 503, and outlet 406.

[0090] System 400 may also comprise radiation sensors 409 for sensing radiation at first filter 403, second filter 404, and / or at work area 401 a-401 f. Radiation sensors at first filter 403 and second filter 404 may measure radiation emitted from radioactive debris within the respective filter(s) which may be used to decide when the filter needs to be replaced to keep radiation emission below a desired value. Controller 2001 may be provided in communication with the radiation sensor(s) on the first filter 403, second filter 404, and / or at work area 401 a-401f, where controller 2001 is configured to actuate an alarm when the radiation sensor(s) increase above a threshold radiation value. When the threshold radiation value is reached, first filter 403 and / or second filter 404 may be replaced, orthework area 401 a-401f may be cleared of personnel and cleaned until the radiation level is reduced to a desired value.

[0091] System 400 may be used to keep a tool or pressure vessel at a lower pressure than the surrounding atmosphere, referred to herein as “vacuum pressure”, to prevent migration of radiative debris outside of the tool or pressure vessel. This may both control active particles and ionized gas created in the vessel. Historically, ventilation systems providing vacuum pressure were sized based on a maximum opening size of the tool or pressure vessel, and equipment having smaller openings sizes had higher local air velocities which increases mobilized debris such as particles, dust, and lighter objects which are suctioned in the ventilation system. This may result in radioactive activity and foreign material transport to areas within the tool, pressure vessel, or ventilation system that are harder to access and / or clean. At an overall level, controller 2001 may control ventilation differential pressure controlled through techniques like blower or bypass control and includes controlled addition of air to cover local ventilation removal at worksites with local debris removal. At a work area, contamination transport may be focused on debris of a desired size and / or weight, the capture velocity of the air entering system 400 may be controlled to a desired velocity value to limit local velocity changes on or around work areas, e.g. retube machines 401 and the reactor components coupled to the machine such as lattice tubes, to minimize contamination transport of undesired debris. In an example, the capture velocity may be in a range of 100-200 feet per minute (fpm). It also may be structured to locally remove gaseous contaminants like tritium coming off equipment that has been exposed to heavy water. In an embodiment, system 400 may comprises controller 2001 in communication with flow meter(s) and a flow control valve 410 for controlling a velocity of air through first end 402-1 of first conduit 402.

[0092] Differential pressure across filters 403, 404, 407 may also be monitored to determine if the filters are full of debris and need to be replaced. If pressure drop across filters 403, 404 increases then the velocity of air at corresponding first end 402-1 may decrease reducing the effectiveness of the suction to receive debris. Further, flow through adjacent branches may increase leading to higher capture velocities and migration of larger size / weight debris at the work area. In an embodiment, controller 2001 may also be in communication with pressure sensors 411 , e.g. pressure differentialsensors / indicators (DPI), for measuring pressure drop across at least one of the first filter and second filter. Controller 2001 may be configured to actuate an alarm when the pressure drop across the filter increases above a threshold pressure value. In another embodiment, controller 2001 may be communication with suction blower 413 for controlling a velocity of air through first end 402-1 of first conduit 402. Controller 2001 may increase or decrease the suction pressure to change the capture velocity through first end 402-1 . In an example, suction blower 413 may be fluidly connected to only the first and second filters such that an increase or decrease in suction pressure only impacts a capture velocity at one first end 402-1 of conduit 402.

[0093] Controller 2001 may be configured to monitor and / or control the pressure and velocity of air entering the ventilation system 500 and vacuum collection system 400. In an aspect, pressure within volume 502 may decrease when both ventilation system 500 and vacuum collection system 400 are operating and withdrawing air from the volume independently. To stabilize pressure within volume 502, controller 2001 may regulate the flow of air withdrawn by ventilation system 500 and vacuum collection system 400 to mitigate against migration of debris into volume 502. In an embodiment, when the pressure within volume 502 is below a setpoint, controller 2001 may send data to suction blower 513 to decrease the flow rate of air into inlet 501 a,b,c, and to suction blower 413 to decrease a flow rate of air into the first end 402-1 . In another embodiment, when the pressure within volume 502 is below the setpoint, controller 2001 may send data to the flow balancing valve, e.g. flow control valve 410, to reduce a flow of air into at least one of inlet 501 a, b, c, and the first end 402-1 . The setpoint may be set based on a velocity of air moving through the ventilation system 500 and / or vacuum collection system 400. In an embodiment, the velocity of the air passing out of the volume is determined by at least one of a velocity meter in the vacuum system and the ventilation system, pressure drop across the first suction blower 513, and pressure drop across the second suction blower 413.

[0094] In an embodiment, when the controller 2001 receives data that radioactivity measured by a sensor 509 in an exhaust line, e.g. outlet 406, is above a threshold radiation level, controller 2001 may be configured to send data to stop air flow from the vacuum collection system 400 and / or reduce air flow through the suction blower 513. This control strategy may act as a safeguard in the event of filter failure. Suction blower513 may continue operating at a reduced rate to maintain a negative pressure within volume 502 relative to the exterior pressure of volume 502 defined by the component of the nuclear reactor.

[0095] In an embodiment, vacuum collection system 400 and / or ventilation system 500 may comprise a catalytic converter 450, 550 to convert gaseous contaminants received from the work area to liquid forms. Example contaminants include tritium and vapour phase isotopes. Reacting the tritium and vapour phase isotopes into the liquid phase may allow the isotopes to be collected and mitigate against spread of the isotopes through the system 1 to the exhaust or potential leaks in the system. Example isotopes that may exist in the vapour phase include isotopes of iodine, carbon 14, and tritium. Example catalysts for the catalytic converter may include platinum catalyst. In an embodiment, heat and an oxygen source may be provided for oxidization of isotopes in gas phase to the liquid phase. In example, heat may be provided by a heater 451 , 551 to provide energy for the oxidation of the isotopes. Heater 451 , 551 may be positioned upstream of catalytic converter 450, 550 as shown in FIGs. 4 and 5. Heater 451 , 551 may also evaporate liquid droplets in the air which may contain particles of debris and / or contamination from the work area. By heating the liquid droplets, heater 451 , 551 may knock-out the aerosolized debris and / or contamination for collection. Heater 451 , 551 may also evaporate liquid to leave residual contaminants such as tritium and other vapour phase isotopes. Tritium is a hydrogen isotope and primarily exists in solution in water or as a hydride. Heater 451 , 551 may remove tritium in water vapour. Gas-phase tritium may be separated from the gas phase by catalytic converters 450, 550.

[0096] FIG. 6 shows a schematic diagram illustrating a method 1000 for decontaminating a work area having radioactive and / or toxic debris. As described above, method 1000 may be performed by controller 2001 and system 1 .

[0097] At 1002, the method comprises providing a system according to this disclosure, e.g. system 1 described above.

[0098] At 1004, the method comprises receiving data indicative of the pressure within the volume defined by a component of a nuclear reactor and the velocity of air moving out of the volume.

[0099] At 1006, the method comprises sending data to at least one of a first suction blower and a flow balancing valve to increase the flow rate of air from the volume into the inlet of the ventilation system and to the ventilation system filter if the pressure within the volume is above the setpoint and if the velocity of air moving out of the volume is below the threshold velocity. The threshold velocity may be determined based on a capture velocity of radioactive debris and / or toxic materials in the volume to prevent and / or minimize migration of the radioactive debris and / or toxic materials into the ventilation system.

[0100] At 1008, the method comprises sending data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air from the volume into the inlet and to the ventilation system filter if the velocity of air moving out of the volume is above the threshold velocity.

[0101] In an embodiment, when vacuum collection system 400 is provided, the method comprises suctioning the debris from the work area through the first end of the first conduit. In an embodiment, the method comprises controlling a velocity of air through the first end of the first conduit to a desired capture velocity for transport debris having a desired size and / or weight. Accordingly, collection of radioactive debris and / or toxic material may be biased toward vacuum collection system 400; while preventing or minimizing the debris and / or toxic material from being captured by the ventilation system 500. First and second filters, and ventilation system filters may filter the air passing through vacuum collection system 400 and ventilation system 500 respectively, prior to discharging the filtered air. In an embodiment, pressure drop across at least one of the first filter and second filter may be measured, and an alarm actuated when the pressure drop increases above a threshold pressure value. Pressure drop across the filters may be used to indicate when they are full. The first filter may be replaced with another filter when the pressure drop increases above the threshold pressure value across the first filter; and the second filter may be replaced with another filter when the pressure drop increases above the threshold pressure value across the second filter. The first filter may also be replaced when a measured radiation value increases above a threshold radiation value for the first filter.

[0102] In an embodiment, when vacuum collection system 400 is provided, method 1000 comprises receiving data indicative of the pressure within volume 502 and the velocity ofair moving out of the volume. Controller 2001 may send data to at least one of the first suction blower 513 and flow balancing valve 410 to increase the flow rate of air from volume 502 into inlet 501 a,b,c and to the ventilation system filter 503 if the pressure within volume 502 is above the pressure setpoint and if the velocity of air moving out of the volume is below the threshold velocity, e.g. the value set to prevent a capture velocity being reached so that radioactive debris and / or toxic materials in the volume are prevented and / or minimized from migrating into the ventilation system or moving within volume 502. Controller 2001 may also send data to at least one of the suction blower 513, flow balancing valve 410, and suction blower 413 to decrease the flow rate of air from volume 502 into at least one of the ventilation system 500 and the vacuum collection system 400 if the velocity of air moving out of the volume is above the threshold velocity.

[0103] In an embodiment, method 1000 may comprise sensing radiation emitted from at least one of the first filter, the second filter, and the work area, and actuating an alarm when the radiation increases above a threshold radiation value. The radiation may be sensed by sensor 409.

[0104] In an embodiment, method 1000 may comprise replacing the first filter with a third filter when the radiation increases above the threshold radiation value at the first filter. In another embodiment, method 1000 comprises replacing the second filter with a fourth filter when the radiation increases above the threshold radiation value at the second filter.

[0105] CONTROLLER

[0106] FIG. 7 shows a generalized schematic view of example system 2000 for decontaminating a work area having radioactive and / or toxic debris. System 2000 may comprise controller 2001 , described herein. Controller 2001 includes a processor 2002 configured to implement processor readable instructions that, when executed, configure the processor 2002 to conduct operations described herein. The processor 2002 may be a microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), or combinations thereof. Controller 2001 may include a communication interface 2004 to communicate with other computing or sensor devices, to access or connect to network resources, or to perform other computing applications by connecting to a network (or multiple networks) capable of carrying data.In some examples, the communication interface 2004 may include one or more busses, interconnects, wires, circuits, and / or any other connection and / or control circuit, or combination thereof. The communication interface 2004 may provide an interface for communicating data between the system 2000 and a display 2015.

[0107] Controller 2001 may also comprise connections for communicating with any of tool 100, worktable 96, platform 95, radiation sensor 409, flow controller 410, pressure sensor 411 , and / or suction blower 413 according to this disclosure to transmit setpoint(s) or receive data such as radiation, pressure, among other data.

[0108] Controller 2001 may be coupled to a data system 2014 for storing system data and / or may be configured to communicate with cloud services such as iCloud, Dropbox, Google clouds, or any other digital data servers. Data system 2014 may also comprises a universal asynchronous receiver-transmitter (UART) to allow communication with other devices, e.g. a smartphone or a computer, for transmitting data for analysis and / or storage. UART may include or be coupled to a wireless transceiver for wireless communication with such other devices, e.g., by way of infra-red, Bluetooth, Wi-Fi, or the like. Network 2500 may include any wired or wireless communication path, such as an electrical circuit. In some embodiments, the network 2500 may include one or more busses, interconnects, wires, circuits, and / or any other connection and / or control circuit, or a combination thereof. In some embodiments, the network 2500 may include a wired or a wireless wide area network (WAN), local area network (LAN), a combination thereof, or the like. In some embodiments, the network 2500 may include a Bluetooth® network, a Bluetooth® low energy network, a short-range communication network, or the like.

[0109] Controller 2001 may include memory 2006. The memory 2006 may include one or a combination of computer memory, such as static random-access memory (SRAM), random-access memory (RAM), read-only memory (ROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

[0110] The memory 2006 may store an application 2012 including processor readable instructions for conducting operations described herein. In some examples, theapplication 2012 may include operations for controlling a system for decontaminating a work area having radioactive debris according this disclosure.

[0111] In an embodiment, application 2012 may include operations for receiving data indicative of the pressure within volume 502 and the velocity of air moving out of volume 502. The velocity of air may be measured at a sensor 414, 514, e.g. a flow meter or velocity meter, and / or based on the pressure drop blowers 413, 513, or other calculations such as Bernoulli principles using pressure drop, density of air, and the size of the conduit(s) to determine the velocity of air moving through vacuum collection system 400 and / or ventilation system 500. Application 2012 may send data to at least one of suction blower 513 and flow balancing valve 410 to increase the flow rate of air from volume 502 into inlet 501 a,b,c and to ventilation system filter 503 if the pressure within volume 502 is above pressure setpoint forthe volume and if the velocity of air moving out of volume 502 is below the threshold velocity. The setpoint may be selected to provide vacuum pressure, i.e. control the pressure within the volume below the exterior pressure outside the volume defined by the component. The setpoint may be in a range of 2 to 6 psi water gauge below the exterior pressure outside the volume 502, and the threshold velocity may be the velocity of air moving out of the volume when the pressure is below 6 psi water gauge, i.e. the lower portion of the range limit. Application 2012 may send data to at least one of suction blower 513 and flow balancing valve 410 to decrease the flow rate of air from volume 502 into inlet 501 a,b,c and to ventilation system filter 503 if the velocity of air moving out of the volume is above the threshold velocity.

[0112] In an embodiment, where system 1 comprises vacuum collection system 400, application 2012 may include operations for suctioning the debris from the work area 401 a,b,c through first end 402-1 , of the first conduit 402 and the inlet 501 a,b,c by operating blowers 413, 513 and / or control valves 410. Debris from the air may be filtered with the first and second filters 403, 404, and ventilation system filter 503. Air may be discharged, e.g. through outlet 406.

[0113] In an embodiment, application 2012 may include operations for receiving data indicative of the pressure within volume 502 and the velocity of air moving out of the volume. Application 2012 may send data to at least one of first suction blower 513 and flow balancing valve 410 to increase the flow rate of air from volume 502 into inlet 501 a,b,c, and to ventilation system filter 502 if the pressure within the volume is abovethe setpoint and if the velocity of air moving out of the volume is below a threshold velocity. Application 2012 may send data to at least one of suction blower 513 , flow balancing valve 410, and suction blower 413 to decrease the flow rate of air from the volume 502 into at least one of ventilation system 500 and vacuum collection system 400 if the velocity of air moving out of volume 502 is above the threshold velocity.

[0114] In an embodiment, the threshold velocity of application 2012 may be set by an operator based on an observed velocity of air moving into ventilation system 500 and vacuum collection system 400 when there is no observed migration of the at least one toxic and / or radioactive debris. In another embodiment, the threshold velocity may be set based on a calculation to minimize contamination transport, where the threshold velocity value determined based on vapour percentage, pressure, temperature, cross- sectional area of at least one opening to the volume, the opening defined by the component of the nuclear reactor. In another embodiment, the threshold velocity is set based on a measured velocity of air exiting a combined outlet of the ventilation system and vacuum collection system when the radiation detected in at least one of the volume the vacuum collection system, and the ventilation system is equal to or less than a threshold radiation value.

[0115] In an embodiment, application 2012 may determine the velocity of air moving out of volume 502 by at least one of the pressure drop across the first suction blower 513, a flow meter, and / or a velocity meter 414, 514.

[0116] In an embodiment, application 2012 may include operations for sensing radiation emitted from at least one of first filter 403, second filter 404, ventilation system filter 503, and the work area 401 a,b,c, and actuating an alarm when the radiation increases above a threshold radiation value. First filter 403 and / or second filter 404 may be replaced with another filter when the radiation increases above the threshold radiation value at the first filter 403.

[0117] In another embodiment, application 2012 may include operations for actuating a flow control valve 410 to increase or decrease a velocity of air through first end 402-1 of the first conduit 402 to a desired velocity. In an example, the desired velocity is a desired capture velocity.

[0118] In another embodiment, application 2012 may include operations for receiving pressure drop data across at least one of first filter and second filter, and actuating an alarm when the pressure drop increases above a threshold pressure value.

[0119] In another embodiment, application 2012 may include operations for actuating a suction blower to control a velocity of air through first end of the first conduit to a desired velocity. In an example, the desired velocity is a desired capture velocity.

[0120] Alternate embodiments

[0121] The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The present disclosure is intended to cover and embrace all suitable changes in technology. Modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. Also, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[0122] As can be understood, the detailed embodiments described above and illustrated are intended to be examples only. The invention is defined by the appended claims.

[0123] The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.

Claims

WHAT IS CLAIMED IS:1 . A system for controlling contamination at a work area having at least one of toxic and / or radioactive debris, the system comprising: a ventilation system for ventilating a volume defined by a component of a nuclear reactor, the ventilation system comprising: an inlet for receiving air comprising the contamination from the volume; a ventilation system filter for filtering at least one of radioactive and toxic debris received from the volume; and a first suction blower in fluid communication with the inlet and the ventilation system filter, the first suction blower configured to force air from the volume into the inlet and to the ventilation system filter; and a controller configured to: control a pressure within the volume to a setpoint below an exterior pressure outside the volume defined by the component, the setpoint selected to maintain a velocity of air moving out of the volume below a threshold velocity, wherein when the pressure within the volume is above the setpoint, the controller sends data to at least one of the first suction blower and a flow balancing valve to increase a flow rate of air into the inlet and the ventilation system, wherein when the pressure within the volume is below setpoint, the controller sends data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air into the inlet and to the ventilation system filter.

2. The system of claim 1 , wherein the setpoint is a range between a first pressure threshold and a second pressure threshold, wherein the controller is configured to: control the pressure within the volume within the range, wherein the first pressure threshold is greater than the second pressure threshold, wherein when the pressure within the volume is above the first pressure threshold, the controller sends data to at least one of the first suction blower andthe flow balancing valve to increase the flow rate of air into the inlet and the ventilation system, wherein when the pressure within the volume is below the second pressure threshold, the controller sends data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air into the inlet and to the ventilation system filter, wherein pressure within the volume changes based on a flow rate of air entering the volume and a second flow rate of air leaving the volume, and wherein the second pressure threshold is selected to maintain the velocity of air passing out of the volume below the threshold velocity.

3. The system of any one of claims 1 -2 wherein, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller is configured to send data to open a valve to exhaust air received from the ventilation system to a vacuum container.

4. The system of any one of claims 1-3 comprising: a vacuum collection system defined within the volume, the vacuum collection system comprising: a first conduit having a first end configured for coupling with at least one of a vacuum head, and a tool for refurbishing or decommissioning a nuclear reactor; a first filter for filtering radioactive debris received from the work area, the first filter coupled to a second end of the conduit, and the first filter positioned proximate to the first end to provide a desired length of the first conduit; and a second conduit coupling the first filter to a second filter for filtering radioactive debris from the work area; a second suction blower in fluid communication with the first conduit, the first filter, the second conduit, and the second filter, the second suction blower configured to force air external to the first end of the first conduit to enter the first end to move the radioactive debris from the first end to at least one of the first filter and the second filter; andan outlet in fluid communication with the first and second suction blowers for discharging the air received from the second filter.

5. The system of claim 4, wherein when the pressure within the volume is below the setpoint, the controller sends data to the first suction blower to decrease the flow rate of air into the inlet, and to the second suction blower to decrease a flow rate of air into the first end.

6. The system of claim 4, wherein when the pressure within the volume is below the setpoint, the controller sends data to the flow balancing valve to reduce a flow of air into at least one of inlet and the first end.

7. The system of any one of claims 4-6, wherein the velocity of the air passing out of the volume is determined by at least one of: a velocity meter in the vacuum system, a velocity meter in the ventilation system, pressure drop across the first suction blower, and pressure drop across the second suction blower.

8. The system of any one of claims 4-7, wherein, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller is configured to send data to stop air flow from the vacuum collection system and / or reduce air flow through the first suction blower.

9. The system of any one of claims 4-8, wherein, when the controller receives data that radioactivity measured by a sensor in an exhaust line is above a threshold radiation level, the controller is configured to send data to a plurality of control valves to stop air flow through the ventilation system and the vacuum collection system.

10. The system of any one of claims 4-9, wherein: when the first suction blower is in operation, a first flow path is defined by the volume, the inlet, the ventilation system filter, and the outlet, and when the second suction blower is in operation, a second flow path is defined by the first end of the first conduit, the first conduit, the first filter, the second conduit, the second filter, and the outlet.

11. The system of any one of claims 4-10, wherein the desired length of the first conduit is in a range of 0.5 -20 meters, preferably 0.5-10 meters.

12. The system of any one of claims 4-11 , wherein the outlet is at least one of a vacuum container, and a D2O recovery system.

13. The system of claim 4-12, wherein the first filter comprises radioactive shielding.

14. The system of claim 4-13, wherein the first and second filter comprises at least one of a pre-filter a High Efficiency Particulate Air (HEPA) filter, a Ultra-Low Particulate Air (ULPA) filter; and a magnetic collection system comprising magnets for collecting ferrous metals in the debris.

15. The system of any one of claims 4-14, wherein the first filter is configured to collect a portion of the debris having a size of about at least 0.3 microns.

16. The system of claim 14, wherein the second filter comprises the HEPA filter, the ULPA filter; and the magnetic collection system positioned in series.

17. The system of any one of claims 4-16, wherein the second filter is configured to collect a portion of the particles having a size of about at least 0.3-microns.

18. The system of any one of claims 4-17, wherein the system comprising radiation sensors for sensing radiation at the first filter, the second filter and / or at the work area.

19. The system of claim 18, wherein the controller is in communication with the radiation sensor, the controller configured to actuate an alarm when the radiation sensor increases above a threshold radiation value.

20. The system of any one of claims 4-18, wherein the controller is in communication with a flow meter and a flow control valve for controlling a velocity of air through first end of the first conduit.21 . The system of any one of claims 4-20, wherein the controller is in communication with pressure sensors for measuring pressure drop across at least one of the first filter and second filter, the controller configured to actuate an alarm when the pressure drop increases above a threshold pressure value.

22. The system of any one of claims 4-21 , wherein the controller in communication with the second suction blower for controlling a velocity of air through first end of the first conduit.

23. The system of claim 22, wherein the second suction blower is fluidly connected to only the first and second filters.

24. The system of any one of claims 1 to 23 comprising a catalytic converter to convert gaseous contaminants received from the work area to liquid forms.

25. The system of any one of claims 1 to 24 comprising a heater for evaporating liquid droplets and vapour entraining radioactive and / or toxic debris.

26. The system of any one of claims 1 to 25 comprising a radiation sensor on an exhaust of the ventilation system, wherein when the controller receives data indicating a threshold radiation level sensed by the radiation sensor has been reached, the setpoint is raised to a minimum differential pressure (dP) below the exterior pressure outside the volume defined by the component.

27. The system of any one of claims 1 -27, wherein the component is a vault of a nuclear reactor, a calandria vessel, a reactivity mechanisms deck, or a calandria relief duct.

28. A method for controlling contamination at a work area having at least one of toxic and / or radioactive debris, the method comprising: providing a system of claim 1 ; receiving data indicative of the pressure within the volume and the velocity of air moving out of the volume; sending data to at least one of the first suction blower and the flow balancing valve to increase the flow rate of air from the volume into the inlet and to the ventilation system filter if the pressure within the volume is above the setpoint and if the velocity of air moving out of the volume is below the threshold velocity, sending data to at least one of the first suction blower and the flow balancing valve to decrease the flow rate of air from the volume into the inlet and to the ventilation system filter if the velocity of air moving out of the volume is above the threshold velocity.

29. The method of claim 28 comprising: providing the system of claim 4;suctioning the debris from the work area through the first end of the first conduit and the inlet; filtering the debris from the air with the first and second filters, and the ventilation system filter; and discharging the air.

30. The method of claim 29, comprising receiving data indicative of the pressure within the volume and the velocity of air moving out of the volume; sending data to at least one of the first suction blower and the flow balancing valve to increase the flow rate of air from the volume into the inlet and to the ventilation system filter if the pressure within the volume is above the setpoint and if the velocity of air moving out of the volume is below the threshold velocity, sending data to at least one of the first suction blower, the flow balancing valve, and the second suction blower to decrease the flow rate of air from the volume into at least one of the ventilation system and the vacuum collection system if the velocity of air moving out of the volume is above the threshold velocity.31 . The method of claim 28 or 30, wherein the threshold velocity is set based on an observed velocity of air moving into the ventilation system and vacuum collection system when there is no observed migration of the at least one toxic and / or radioactive debris.

32. The method of claim 28 or 30, wherein the threshold velocity is set based on calculated velocity to minimize contamination transport, the threshold velocity value determined based on vapour percentage, pressure, temperature, cross-sectional area of at least one opening to the volume, the opening defined by the component of the nuclear reactor.

33. The method of claim 28 or 30, wherein the threshold velocity is set based on a measured velocity of air exiting a combined outlet of the ventilation system and vacuum collection system when the radiation detected in at least one of the volume the vacuum collection system, and the ventilation system is equal to or less than a threshold radiation value.

34. The method of claim 28 or 30, wherein the setpoint is in a range of 2 to 6 psi below the exterior pressure outside the volume, and the threshold velocity is the velocity of air moving out of the volume when the pressure is below 6 psi.

35. The method of any one of claims 28-34, wherein the velocity of air moving out of the volume is determined by at least one of: the pressure drop across the first suction blower, a flow meter, and a velocity meter.

36. The method of claim 29 comprising sensing radiation emitted from at least one of the first filter, the second filter, and the work area, and actuating an alarm when the radiation increases above a threshold radiation value.

37. The method of claim 29 comprising replacing the first filter with a third filter when the radiation increases above the threshold radiation value at the first filter.

38. The method of claim 29 comprising replacing the second filter with a fourth filter when the radiation increases above the threshold radiation value at the second filter.

39. The method of any one of claims 28-38, comprising controlling a velocity of air through the first end of the first conduit to a velocity for minimizing contamination transport.

40. The method of any one of claims 28-39, comprising measuring pressure drop across at least one of the first filter and second filter, and actuating an alarm when the pressure drop increases above a threshold pressure value.41 . The method of claim 40, comprising replacing the first filter with a third filter when the pressure drop increases above the threshold pressure value across the first filter.

42. The method of claim 40, comprising replacing the second filter with a fourth filter when the pressure drop increases above the threshold pressure value across the second filter.

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