Device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit

Abstract

The present invention belongs to the technical field of reactor pressure vessels, and particularly relates to a device for measuring the out-of-core neutron fluence of a reactor pressure vessel of a nuclear power unit. The present invention includes an upper fixing component, a detector sheet box, a middle bead chain, and a lower weight component. The upper fixing component is installed on a platform. The upper fixing component includes two semi-circular ring structures. The inner diameter of the formed ring is larger than the outer diameter of the channel steel lining, and the outer diameter of the ring is smaller than the inscribed circle diameter of the three cover plate supports. The bottom end of the upper fixing component is located at the upper end face of the channel. The middle bead chain is installed inside the upper fixing component. A number of detector sheet boxes are connected to the lower part of the middle bead chain, and the lowermost end of the middle bead chain is connected to the lower weight component. The present invention can measure information such as neutron fluence and neutron energy spectrum, and obtain reliable neutron fluence data of the reactor pressure vessel, so as to accurately evaluate the irradiated damage state of the reactor pressure vessel materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of reactor pressure vessels, and particularly relates to a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit. Background Art

[0002] During the operation of a nuclear power plant, it is necessary to monitor the fast neutron fluence endured by the materials of the reactor pressure vessel. Usually, irradiated surveillance specimens placed inside the pressure vessel are used to achieve this purpose. The ex-core neutron dose measurement technology for the outside of the reactor pressure vessel can be used as an effective supplement to in-core irradiation surveillance.

[0003] The ex-core neutron fluence measurement technology requires fixing neutron activation detector foils at specific positions outside the pressure vessel. By monitoring the neutron fluence at these positions, the fast neutron fluence and neutron energy spectrum are deduced. The deduced results are compared with the theoretical calculated values to verify the accuracy of the theoretical calculation results of the neutron fluence in the pressure vessel.

[0004] In order to fix the neutron activation detector foils at the monitoring positions that can represent the neutron fluence data of the reactor pressure vessel, a special device must be designed according to the characteristics such as the relevant structural dimensions of the unit to achieve the positioning of the detector foils. For VVER-1000 nuclear power units, the main structure of the channels available for fixing the ex-core neutron detector foils is as Figure 1 shown.

[0005] The channels are located outside the reactor pressure vessel and are evenly distributed in the circumferential direction of the pressure vessel, with a total of 30. As Figure 1 shown, the main structure includes several parts such as channel covers, channel steel linings, channel steel sleeves, and cover supports. The channel steel sleeves, steel linings, and the circle passing through the centers of the three cover supports are concentric circles, and the central angles of the three cover supports are 120 degrees.

[0006] The present invention designs a support hardware system for ex-core neutron fluence measurement for VVER-1000 nuclear power units. The neutron activation detector foils are lowered from the gap between the channel steel sleeve and the steel lining, and the installation and fixation of the measuring device are realized by using the inherent structure of the channels. Summary of the Invention

[0007] The purpose of the present invention is to provide a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit, which can fix the neutron activation detector foils at specific positions outside the reactor pressure vessel of VVER-1000 nuclear power units, measure the neutron fluence, neutron energy spectrum and other information at this position to verify the accuracy of the theoretical calculation results of the spatial distribution of the reactor neutron fluence, and obtain reliable neutron fluence data of the reactor pressure vessel, so as to achieve an accurate evaluation of the irradiated damage state of the reactor pressure vessel materials.

[0008] Technical solution adopted by the present invention:

[0009] A device for measuring the neutron fluence outside the reactor pressure vessel of a nuclear power unit, comprising an upper fixing component, a detector sheet box, a middle bead chain, and a lower counterweight component. The upper fixing component is installed on a platform. The upper fixing component includes two semi-circular ring structures. The inner diameter of the formed ring is larger than the outer diameter of the channel steel lining, and the outer diameter of the ring is smaller than the inscribed circle diameter of the three cover plates. The bottom end of the upper fixing component is located on the upper end face of the channel. The middle bead chain is installed inside the upper fixing component. Several detector sheet boxes are connected to the lower part of the middle bead chain, and the lowermost end of the middle bead chain is connected to the lower counterweight component.

[0010] The upper fixing component includes an inner semi-circular ring structure and an outer semi-circular ring structure. The inner semi-circular ring structure includes a 90° positioning hinge, a threaded joint, and a butterfly buckle. The 90° positioning hinge and the threaded joint are fixedly installed inside the inner semi-circular ring structure, and the butterfly buckle is installed at the outer edge of the inner semi-circular ring structure. The outer semi-circular ring structure includes a butterfly lock and a positioning mark. The butterfly lock is installed at the outer edge of the outer semi-circular ring structure, corresponding to the position of the butterfly buckle, and the positioning mark is installed outside the outer semi-circular ring structure. The two semi-circular rings are connected by a butterfly lock buckle to form a ring after connection.

[0011] The 90° positioning hinge is opened and supported on the channel casing to ensure the accurate fixation of the two semi-circular rings.

[0012] The threaded joint is connected to the middle bead chain.

[0013] By positioning this mark, the position of the threaded joint is located, that is, the circumferential position of the middle bead chain is located.

[0014] The position of the detector sheet box corresponds to the position to be measured.

[0015] The lower counterweight component ensures the stability of the middle bead chain during installation and ensures that the middle bead chain is vertically placed along the gap between the channel casing and the channel lining.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) The present invention provides a device for measuring the neutron fluence outside the reactor pressure vessel of a nuclear power unit, with a simple structure, accurate size control, and ensuring the accuracy of the installation position by controlling a small number of positions;

[0018] (2) The present invention provides a device for measuring the neutron fluence outside the reactor pressure vessel of a nuclear power unit, which uses quick snap connections to achieve quick installation and replacement;

[0019] (3) The present invention provides a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit. All the materials used are common materials in nuclear power plants and will not introduce safety risks to the nuclear power plant;

[0020] (4) The present invention provides a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit. By means of the inherent structure of the power plant, positioning marks are designed and installed to ensure that the installation position is strictly consistent with the planned installation position;

[0021] (5) The present invention provides a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit. Welding fixation and threaded connection are adopted, and there are no loose parts. During the installation and monitoring processes, no components will fall off and no foreign objects will be formed, ensuring that no safety hazards will be formed. Description of the Drawings

[0022] Figure 1 It is a three-dimensional view of the upper structure of the ionization chamber duct for a VVER-1000 unit;

[0023] Figure 2 It is a schematic installation view of a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit provided by the present invention;

[0024] Figure 3 It is a schematic view of the inner half-ring structure of the upper fixing assembly;

[0025] Figure 4 It is a schematic view of the outer half-ring structure of the upper fixing assembly;

[0026] In the figure: 1 - cover plate support; 2 - gap between the casing and the lining; 3 - duct cover plate; 4 - duct casing; 5 - platform; 6 - duct steel lining; 7 - upper fixing assembly; 8 - detector cassette; 9 - middle stainless steel bead chain; 10 - lower counterweight component; 11 - 90° positioning hinge; 12 - threaded joint; 13 - butterfly buckle; 14 - butterfly lock; 15 - positioning mark. Detailed Embodiment

[0027] The following further elaborates in detail on a device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit provided by the present invention in conjunction with the drawings and specific embodiments.

[0028] The results of the neutron activation detector foils in the reactor pressure vessel need to be compared with the results of the theoretical calculation of neutron fluence to verify the accuracy of the theoretical calculation results. The neutron fluence at different positions in the space around the reactor varies significantly. Therefore, the installation position of the neutron activation detector foils must be exactly the same as the planned installation position to ensure the reliability of the comparison results. At the same time, the installation position is in a key area of the nuclear power plant. It is necessary to ensure that the detector foils and the supporting hardware will not be damaged or dropped during installation and monitoring, so as not to form foreign objects that endanger the safety of the unit. In addition, the installation position is close to the core, and the environmental dose rate is high. It is necessary to control the on-site working time of the installation and replacement personnel and control the personnel dose.

[0029] As Figure 2 shown, a device for measuring the ex-core neutron fluence of the reactor pressure vessel of a nuclear power unit provided by the present invention includes an upper fixing component 7, a detector foil box 8, a middle bead chain 9, and a lower counterweight component 10. The upper fixing component 7 is installed on the platform 5.

[0030] The upper fixing component 7 includes two semi-circular ring structures. The inner diameter of the formed ring is larger than the outer diameter of the channel steel lining 6, and the outer diameter of the ring is smaller than the inscribed circle diameter of the three cover plates supports 1. It includes an inner semi-ring structure and an outer semi-ring structure. Among them, as Figure 3 shown, the inner semi-ring structure includes a 90° positioning hinge 11, a threaded joint 12, and a butterfly buckle 13. The 90° positioning hinge 11 and the threaded joint 12 are fixedly installed inside the inner semi-ring structure, and the butterfly buckle 13 is installed at the outer edge of the inner semi-ring structure; as Figure 4 shown, the outer semi-ring structure includes a butterfly lock 14 and a positioning mark 15. The butterfly lock 14 is installed at the outer edge of the outer semi-ring structure, corresponding to the position of the butterfly buckle 13, and the positioning mark 15 is installed outside the outer semi-ring structure; the two semi-rings are connected by a butterfly lock buckle to form a ring after connection.

[0031] When installing, open the 90° positioning hinge and support it on the channel casing 4, which can ensure the accurate fixation of the two semi-rings. The above design can ensure that the upper fixing component is installed between the channel steel lining 6 and the three cover plates supports 1 to achieve radial positioning.

[0032] The threaded joint 12 is connected to the middle bead chain 9. When installing, by positioning the mark 15, the position of the threaded joint 12 can be accurately positioned, that is, the circumferential position of the middle bead chain is accurately positioned.

[0033] The bottom end of the upper fixing component 7 is located at the upper end face of the channel. By precisely controlling the distance between the bottom of the threaded joint 12 and the bottom end of the upper fixing component 7 by welding, the accuracy of the elevation data of the top end of the middle bead chain 9 can be ensured.

[0034] A number of detection chip boxes 8 are connected to the lower part of the middle bead chain 9, and the positions of the detection chip boxes 8 correspond to the positions to be measured. The lowermost end of the middle bead chain 9 is connected with a lower counterweight component 10.

[0035] The lower counterweight component 10 ensures the stability of the middle bead chain 9 during installation, ensuring that the middle bead chain 9 is vertically placed along the gap between the hole duct casing 4 and the hole duct lining 6. At the same time, it also ensures that the middle bead chain 9 will not undergo obvious displacement due to external vibrations or other reasons during monitoring.

[0036] The specific implementation method is as follows:

[0037] Rotate to open the threaded joint 12 on the inner half ring of the upper fixing component, connect the one-way joint at the upper end of the middle stainless steel bead chain to this threaded joint, and then tighten the thread. Connect the steel wire rope to the one-way joint at the lower end of the middle bead chain through the through hole of the lower counterweight component 10. Complete the assembly of the installation hardware.

[0038] Vertically place the assembled hardware along the hole duct gap, with the counterweight component 10 at the lowermost end, and place the inner half ring of the upper fixing component at the uppermost end into the gap between the steel lining and the three cover plate supports.

[0039] Adjust the position of the inner half ring so that the outer half ring can be easily installed, and then pull the 90-degree positioning hinge 11 to the 90-degree position and press it against the outer wall of the hole duct casing.

[0040] Place the outer half ring 5 of the upper fixing component into the gap between the steel lining and the three cover plate supports, adjust the positions of the two half rings so that their interfaces are aligned to form a circular ring. Ensure that the positioning mark 15 on the positioning outer half ring is at the center of the half ring. Connect the two half rings with a butterfly lock to complete the upper fixing. Thus, the installation of the entire support hardware device is completed.

[0041] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit, characterized in that, it includes an upper fixing component, a detector sheet box, a middle bead chain, and a lower counterweight component. The upper fixing component is installed on a platform. The upper fixing component includes two semi-circular ring structures. The inner diameter of the formed ring is larger than the outer diameter of the channel steel lining, and the outer diameter of the ring is smaller than the inscribed circle diameter of the three cover plates. The bottom end of the upper fixing component is located on the upper end face of the channel. The middle bead chain is installed inside the upper fixing component. Several detector sheet boxes are connected to the lower part of the middle bead chain, and the lowermost end of the middle bead chain is connected to the lower counterweight component; the upper fixing component includes an inner semi-circular ring structure and an outer semi-circular ring structure. The inner semi-circular ring structure includes a 90° positioning hinge, a threaded joint, and a butterfly buckle. The 90° positioning hinge and the threaded joint are fixedly installed inside the inner semi-circular ring structure, and the butterfly buckle is installed at the outer edge of the inner semi-circular ring structure; the outer semi-circular ring structure includes a butterfly lock and a positioning mark. The butterfly lock is installed at the outer edge of the outer semi-circular ring structure, corresponding to the position of the butterfly buckle, and the positioning mark is installed on the outside of the outer semi-circular ring structure; the two semi-circular rings are connected by a butterfly lock buckle, and a ring is formed after connection; the 90° positioning hinge is opened and supported on the channel casing to ensure the accurate fixation of the two semi-circular rings; the threaded joint is connected to the middle bead chain.

2. The device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit according to claim 1, characterized in that, by positioning this mark, the position of the threaded joint is positioned, that is, the circumferential position of the middle bead chain is positioned.

3. The device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit according to claim 1, characterized in that, the position of the detector sheet box corresponds to the position to be measured.

4. The device for measuring the ex-core neutron fluence of a reactor pressure vessel in a nuclear power unit according to claim 1, characterized in that, the lower counterweight component ensures the stability of the middle bead chain during installation and ensures that the middle bead chain is vertically inserted along the gap between the channel casing and the channel lining.

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