Energy containment structures for nuclear reactors.

Abstract

An energy absorption device is disclosed that includes a plurality of assemblies, each including a plurality of, preferably cylindrical, tubes. Each of the plurality of tubes includes a heat-absorbing material, such as ammonium carbamate. The plurality of assemblies are supported within a plurality of elongated baskets that surround the periphery of the containment vessel structure and are located in a storage room. The energy absorption device absorbs excess energy released in the event of a design-based accident.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This non-provisional application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62 / 871,898, filed July 9, 2019, entitled “USE OF HEAT ENDOSCOPIC MATERIAL IN ICE CONDENSER CONTAINERS,” the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] This application relates to safety mechanisms in nuclear reactors, and more particularly to heat absorbing materials for energy containment in the event of an accident.

[0003] Nuclear power is an established form of much-needed clean energy, provided there are no uncontained accidents that allow the escape of radioactive materials. To avoid such accidents, the nuclear industry has expended considerable effort on systems and methods to improve safety under various possible accident scenarios. One example is the development of ice condenser containments in 1965, which allows ice to absorb the substantial energy released during a loss of coolant accident (LOCA) or steam line break (SLB). The adoption of ice condenser absorbers ultimately allowed for smaller, thinner containments with lower pressure ratings (10-15 psig vs. ~50-60 psig). Simulations at the time showed an acceleration of typical behavior following a break in a pipe upon attainment of containment conditions, which previously required about 2 hours with dry containment and was reduced to about 5 minutes using ice condensers.

[0004] With reference to Figures 1-4, nuclear reactors with various containment designs are disclosed. Figure 1 shows an exemplary existing nuclear reactor including a containment structure 10 having an outer perimeter wall 12 and an inner wall 14, and a hatch door 44 for accessing the interior. A nuclear reactor 16 is contained within the inner wall 14. The nuclear reactor is surrounded by a reactor cavity 64 filled with a coolant, typically water, and covered with a removable slab 28, and a refueling cavity 22. In various embodiments, the containment structure as shown in Figure 2 includes a divider 26 that separates the steam generator 20 and the nuclear reactor 16 as a high energy system from the remainder of the containment, i.e., the upper and lower compartments. Additionally, a coolant pump 36 pumps hot water from an area above the nuclear fuel in the reactor 16 to the steam generator 20. Upper and lower spray systems 40, 42, respectively, provide an active means for reducing pressure within the containment structure 10 by removing steam from the air within the wall 14.

[0005] In various embodiments, a pipe 38 passes through the reactor cavity 64 and connects the reactor 16 to a steam generator 20 which functions as a heat exchanger.

[0006] The ice basket assembly 56 is contained in the ice storage chamber 18. The ice storage chamber 18 is disposed circumferentially within the interior wall 14 disposed around the main portion of the containment structure 10. The lower portion of the storage chamber as shown in FIG. 2 includes the recirculation sump 30, the accumulator 32, and the pipe annulus 34. The ice storage chamber 18 separates the upper and lower compartments, with all pressure-maintaining equipment disposed in the lower compartment. In the event of a break at the primary pressure boundary (e.g., reactor vessel, steam generators, coolant pumps, and associated piping at approximately 2250 absolute pressure) or at the secondary pressure boundary (e.g., steam pipes, feedwater pipes, and other components at approximately 1250 absolute pressure or less), all steam will route through the ice, thereby removing most of the energy within the structure.

[0007] Within the ice condenser system, there are numerous "doors" that the vapor must pass through on its way between the lower and upper compartments. The lower insulated inlet door 50, located below the ice, prevents hot air in the lower compartment from reaching the ice condenser. The insulated mid-deck door 52, located directly above the ice, is a trapezoidal shaped, spring-loaded panel that prevents atmospheric air in the ice storage room 18 from exchanging with the upper compartment, thereby reducing sublimation and again reducing heat load. The mid-deck door 52 is often the source of problems associated with the ice condenser, for example, additional costs (e.g., maintenance / personnel costs). The upper deck door 54 is typically made of reinforced canvas and simply serves to add an additional separation air layer between the mid-deck door 52 and the upper compartment of the containment structure 10. Notably, the air in this area is ∼2° F warmer than the ice compartment (which itself is 27° F ±5).

[0008] The ice basket assembly 56 contains ~2.6M pounds of ice that is stored in ice baskets 60. These baskets are typically 48 feet tall and 12 inches in diameter. As shown in Figures 3 and 4, the baskets 60 are housed in 24 ice storage chambers 18, each holding 81 baskets 60 and separated by support alignment grids 62 for a total of 1944 baskets in the containment structure 10. The baskets 60 include four 12 foot sections. The upper plenum 46 of the ice condenser system, shown in Figure 5, extends along the space above the ice basket assembly 56 and provides access to the baskets 60. The upper plenum 46 includes a crane 48 for lifting the baskets, air handling unit 58, and ductwork (not shown), walkways, and other mechanisms known to those skilled in the nuclear industry.

[0009] Maintenance of the 192 mid-deck doors 52 in the containment structure 10 must be checked for proper operation at least once each week. During reactor shutdowns, the baskets 60 are also inspected and the ice is weighed using a statistical process based on weighing a subset of the baskets in each quadrant. Certain nuclear plants have experienced ice melting into blocks, reducing the surface area of ​​the ice and thus the expected performance. Depending on the location, some ice baskets 60 are relatively easy to access and inspect; however, the remainder require some disassembly to access.

[0010] The ice itself is in flake form, borated so that it doubles as a neutron absorber once melted, and produced by industrial ice machines. Large cooling equipment is required to keep the space cool using ducted air in the walls and a refrigerated water / glycol combination that flows via tubes 11 that extend through plates in the floor of the structure 10. Each quadrant in the containment structure is made of a plate / glycol tube assembly that is mounted on top of porous isolation concrete and then poured during construction. This represents a lot of additional equipment to maintain and power.

[0011] Nuclear facilities using ice condenser systems have proven economical, but operators face numerous challenges and long-term maintenance costs due to the additional equipment and cooling requirements not present in "conventional" plants. Summary of the Invention

[0012] The following summary is provided to facilitate understanding of some of the innovative features unique to the disclosed embodiments and is not intended to be a complete description, although various aspects of the embodiments may be more fully understood by taking into account the entire specification, claims, abstract, and drawings taken together.

[0013] The concept replaces the ice with a sealed or vented heat sink, eliminating the need for many cumbersome components and equipment. The concept can also be implemented in new reactor designs.

[0014] For example, an apparatus for absorbing energy in a nuclear reactor containment structure in the event of a loss of coolant or a steam line rupture includes at least one assembly comprising a plurality of elongated tubes and a heat absorbing material, such as ammonium carbamate, contained within and occupying a majority of each tube.

[0015] The amount of heat-absorbing material is preferably sufficient to remove energy from the containment structure with the initial energy release resulting from the accident, to maintain the structural integrity of the containment structure, and to later remove heat during fuel reduction in the later period following blowdown, along with other nuclear safety systems.

[0016] The device may further include a plurality of support structures for holding the plurality of tubes. The plurality of tubes may be stacked one assembly on top of another.

[0017] The apparatus may include a plurality of elongated baskets, each basket holding one of the assemblies, and each basket may further include a grid for aligning the plurality of tubes in the assembly axially relative to the basket.

[0018] The tubes and assemblies may be shorter in height than the basket. In each basket, there may be multiple tubes stacked one on top of another. In certain embodiments, the height of the tubes and assemblies may be substantially the same height as the basket. Each tube may further include free space not occupied by the endothermic material to accommodate gases generated during use by the chemical reaction of the endothermic material.

[0019] In various embodiments, the tubes are sealed. In various embodiments, the tubes are vented and include a pressure relief valve fluidly connected to a portion of the tube, such as a tube cover. In various embodiments, the heat absorbing material is ammonium carbamate, and when the tubes are vented, the ammonium carbamate reaction product released at the vent acts as a buffer for sump water within the containment structure.

[0020] The heat absorbing material may be in the form of a slurry made of a liquid mixed with the heat absorbing material. The liquid may be a solvent. In various aspects, the liquid may be selected from the group consisting of water, alcohol, ethylene glycol, and propylene glycol, as well as other solvents.

[0021] In various embodiments, each tube is cylindrical. In various alternative embodiments, each tube is non-cylindrical. In various embodiments, each tube has a wall having a thickness ranging from less than 3 / 100 inch to 1 / 100 inch. Each tube may be linear or non-linear. [Brief description of the drawings]

[0022] The various features of the embodiments described herein are particularly set forth in the appended claims, but the various embodiments as to construction and method of operation, together with their advantages, may be understood in accordance with the following description taken in conjunction with the accompanying drawings, in which:

[0023] [Figure 1] FIG. 1 is a cross-sectional view of a prior art containment structure built in Finland with horizontally oriented generators, showing the ice condenser surrounding the reactor.

[0024] [Diagram 2] FIG. 1 is an elevational view of a prior art pressurized water reactor containment structure constructed in several locations in the United States, showing the arrangement of the reactor, vertically oriented steam generators, ice condenser, and related components of a conventional pressurized water reactor.

[0025] [Diagram 3] 1 shows a representative ice basket contained in a condenser.

[0026] [Figure 4] FIG. 1 is a top cross-sectional view of an exemplary containment structure showing 24 storage rooms and equipment compartments.

[0027] [Diagram 5] 1 shows the mid-deck door, the top deck door, and the upper plenum of the ice condenser showing the ice basket.

[0028] [Figure 6] FIG. 1 is a diagram of an exemplary nuclear fuel assembly including a cylindrical bundle of tubes that can be filled with heat absorbing material.

[0029] [Figure 7] FIG. 1 is a diagram of an exemplary nuclear fuel assembly including a cylindrical bundle of tubes that can be filled with a heat absorbing material, optionally showing a perforated housing.

[0030] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein illustrate various embodiments of the invention in one form and are not to be construed as limiting the scope of the invention in any manner. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Before describing the various aspects of the present disclosure in detail, it should be noted that the illustrative examples are not limited in application or use to the details of the structure and arrangement of parts shown in the accompanying drawings and description. The illustrative examples may be implemented or incorporated in other aspects, variations and modifications, and may be practiced or carried out in various ways. Furthermore, unless otherwise indicated, the terms and expressions employed herein have been selected for the purpose of describing the illustrative examples for the convenience of the reader, and not for the purpose of limitation thereof. It will also be understood that one or more of the following aspects, aspect expressions, and / or examples can be combined with any one or more of the other following aspects, aspect expressions, and / or examples.

[0032] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0033] Directional terms used herein, such as, for example but not limited to, top, bottom, left, right, lower, upward, front, rear, and variations thereof, refer to the orientation of the elements as illustrated in the accompanying drawings and are not limitations of the claims, unless expressly stated to the contrary.

[0034] The term "about" or "approximately" as used in this disclosure, unless otherwise specified, refers to an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or "approximately" means within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term "about" or "approximately" means within 50%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.05% of a given value or range.

[0035] Any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, i.e., having a minimum value of 1 or more and a maximum value of 10 or less.

[0036] To address the problems associated with using ice as an energy absorber in the event of a design-based accident, such as a loss of coolant or steam line rupture accident, a more economical and more sustainable means of absorbing energy under such accident conditions is described herein. A design-based accident as used herein is defined by the United States Nuclear Regulatory Commission as "a postulated accident which a nuclear facility must be designed and constructed to withstand without loss to systems, structures, and components necessary to ensure public health and safety."

[0037] The proposed energy absorber comprises an assembly 100 of a plurality of tubes 70, preferably cylindrical, each of which contains a heat absorbing material. The assembly 100 may include a tube support structure 76 as an exemplary means for fastening the plurality of tubes 70 together. The assembly of tubes 70 may fit into an existing basket 60. In many cases, the same basket 60 may be used, especially if an existing ice system is being replaced by the heat absorbing energy absorbing assembly. Alternatively, the basket 60 may be replaced by a tube bundle designed to fasten to an existing alignment grid structure 62. Any suitable support structure for holding the tubes 70 in place is sufficient. The energy absorber assembly 100 completely replaces the function of the existing ice in absorbing energy during many energy releases. The mid-deck door 52 and all cooling, refrigeration, and air handling equipment are removed, simplifying the structure.

[0038] 6 and 7, an exemplary assembly 100 is shown. With reference to FIG. 6, the tubes 70 are grouped along spokes 78 of a support structure, which may include a stabilizing grid 72. In FIG. 7, each tube 70 is held by a support structure 76, and multiple support structures 76 are joined by different designs of stabilizing grids 72 connected to a surrounding holder 80. In certain embodiments, the tubes may be placed in an existing basket 60. In certain embodiments, the existing basket may be replaced with a perforated housing 74, and the support structure 76 and the tubes 70 may be contained in the housing 74 having holes 66. The tubes 70 may be sealed or vented with any suitable pressure relief valve 68 (only some are shown in black box form for illustrative purposes). Those skilled in the art will recognize that all or a portion of the tubes may be vented with any suitable means for venting, or none of the tubes may be vented, and the vent or relief valve may be located elsewhere on the tubes 70. In a particular example, one or more of the tubes 70 includes a burst disk.

[0039] Cylindrical tubes 70 are preferred because they can be made of any desired material, maintain their strength under pressure (both external and internal), and are well understood for heat transfer applications. However, one skilled in the art will appreciate that other configurations for tubes 70 can be used, with appropriate adjustments to materials and dimensions to accommodate the pressure and temperature exposures expected during use in a nuclear reactor, particularly under accident scenarios. Similarly, housing 74 may be cylindrical or have any other cross-sectional configuration that accommodates multiple tubes 70 in a desired energy absorber assembly 100 in containment structure 10. Tubes 70 may be formed from carbon steel, stainless steel, or other nuclear-qualified materials that have sufficient heat transfer and corrosion resistance to meet design requirements. In various aspects, tubes 70 may include surface treatments, fins 24, and non-linear designs to improve condensation performance.

[0040] A bundle of tubes 70 may be loaded axially into the basket 60 from above the basket. The tubes 70 are less in height than the basket 60. In various embodiments, the tubes 70 may be sized to allow multiple tubes 70 to be stacked within the basket 60, one tube above another. Alternatively, the tubes 70 may be substantially the same height as the basket 60, allowing some space to be located within the basket opening and not extend above the basket opening, such that spokes 78 may be attached to the top or end of the assembly 100, as shown in FIG. 6. In certain embodiments, the tubes 70 may extend beyond the basket opening, as shown in FIG. 7. In various embodiments, the tubes 70 are designed to structurally withstand stacking and other loads required to avoid damage to the tubes or the alignment grid 62.

[0041] The endothermic material is placed inside the tubes 70. Since chemical reaction rates are affected by pressure, consideration is given in manufacturing to factors such as the initial fill volume, free volume, and pressure resistance of the tube material. Initial calculations indicate that the amount of endothermic material required for total energy removal in the containment structure 10 for ice is likely to be less than the amount required to meet the initial blowdown transient energy absorption requirements.

[0042] The expected pressure within the tube 70 during operation is not critical. The tube wall thickness should be thick enough to withstand the pressure of the chemical reaction within the tube, but thin enough to allow heat to pass through the tube. At this point, it is not possible to say exactly how high the pressure will reach, but it is likely to be in the 10s to low 100s of psi. As such, thin-walled tubes (e.g., less than 3 / 100 inch to about 1 / 100 inch thick) can be useful. In at least one example, the thin-walled tubes have thicknesses selected from, for example, a range of 2 / 100 inch to about 5 / 1000 inch, or, for example, a range of 5 / 100 inch to about 1 / 1000 inch. Thin-walled tubes 70 are beneficial because they allow for an increased volume of heat-absorbing material in the tube, reducing structural weight, tube cost, and temperature loss through the wall. Temperature is an important factor in transferring heat into the heat-absorbing material to drive the reaction.

[0043] In existing nuclear plants, the ice condenser plant melts a large amount of water during an accident. This borated melt water becomes part of the sump volume. The energy absorber assembly 100 described herein does not release water. Thus, appropriate modifications to the volume of the refueling water storage tank (a large tank (not shown) typically located outside the containment structure designed to provide water during the initial stages of an accident) and the timing of the injection pump switching from the refueling water storage tank to the sump 30 as the water source can be modified in various aspects. In various aspects, one or both of a larger or additional refueling water storage tank and a source of chemical buffer to counteract the acidity of the boron absorber can be provided. Currently, sodium tetraborate is the form of boron used in ice and is inherently buffered. However, the refueling water storage tank water does not use this form of boron and some means of buffering must be provided.

[0044] In various embodiments, the endothermic material used in tube 70 includes a compound capable of undergoing thermal decomposition. In various embodiments, the endothermic material used in tube 70 is selected from chemicals that are relatively inexpensive, capable of removing large amounts of energy in the event of an accident, remain stable at operational containment temperatures, are sufficiently safe, are compatible with nuclear materials (both as reactants and products), and operate at the desired temperatures required to enable operation of the energy absorbing function.

[0045] An exemplary endothermic material is ammonium carbamate (NH4(H2NCO2)) (AC). AC absorbs energy through an endothermic chemical reaction in the range of temperatures (approximately 10-60°C, relative to pressure) that are useful for condensation in the ice condenser storage chamber. Its volumetric energy removal is approximately 2760 MJ / m 3 , which is nearly nine times that of ice. The products of the reaction are carbon dioxide (CO2) and ammonia (NH3), neither of which are harmful, and both of which are already present in the reactor 16 and the primary side of the containment structure 10, meeting material safety and compatibility requirements.

[0046] When the AC is heated, CO2 and NH3 gases are formed in equilibrium with the solids as a function of pressure and temperature. When the vapor is released into the containment vessel, heat is generated through the AC holder, condensing the vapor and initiating the decomposition of the AC inside the holder. In an embodiment without venting the tube, the CO2 and NH3 gases remain in the tube. The pressure increase is not enough to cause any leaks in the tube.

[0047] At this time, ammonium carbamate is the preferred endothermic material. It appears to perform adequately, is relatively inexpensive, has good reaction products, can be made stable in the desired temperature range of 80-120° F., and is easily procured. Any other suitable endothermic material may be used that has the desired qualities, most importantly energy absorption capacity, stability during normal operating conditions, and safety.

[0048] Filling the tubes with the heat absorbing material can be facilitated by the use of a slurry. In various embodiments, a slurry of ammonium carbamate is mixed with a liquid. Candidates for the liquid can include propylene glycol or ethylene glycol, alcohol, and water. The slurry is used to fill most, if not all, of the space in each tube 70. Some free space can remain after filling to accommodate gases that are generated during use. The pressure within the filled or partially filled tube 70 can be adjusted by backfilling the tube with a non-reactive gas such as argon or conversely by evacuating. The tube 70 is then covered. In various embodiments, the covered tube 70 is sealed against any leaks. In various embodiments, the covered tube 70 can be vented, for example, by means of a pressure relief valve, which can be connected to the tube cover in a suitable known manner.

[0049] The surface area of ​​the tubes 70, rather than the chemical kinetics of the endothermic material, appears to be the driving factor for condensation performance. The coupling relationship between the tubes and the endothermic chemistry must be understood to perform performance estimation. The tube diameter, number, wall thickness, and assumed free volume fraction ultimately determine the volume of chemical contained. However, the chemical volume, tube diameter, amount reacted, and temperature affect the chemical kinetics and therefore the energy removed per tube area. These parameters vary along the length of the tube and with time during the transient. These complex interactions can be modeled along with a two-stage flow calculation in a nodal method to estimate the condenser performance achieved by a given configuration. The nuclear safety code GOTHIC can be useful for these calculations. Previous work using GOTHIC indicates that the amount of endothermic material can be 3-4 times the amount required to simply match the amount of energy ice can remove. Increases in total energy removed of 300-400% can be realized. These calculations showed that the ammonium carbamate chemistry performed well and enhanced many of the benefits of the slurry for ease of packing.

[0050] In various embodiments, the energy absorber assemblies described herein, compared to existing ice condenser designs, replace the ice with an endothermic chemical energy absorber such as ammonium carbamate, and / or directly replace the ice or ice and ice basket 60 with a cylindrical assembly of thin-walled tubes 70 containing endothermic material energy absorbers (e.g., with inner diameters ranging from 0.25-0.625 inches with a triangular pitch of 1.25-1.5). In various embodiments, the energy absorber assemblies described herein use sealed tubes 70 with some free volume to tailor chemical performance, significantly simplifying concerns related to chemical products interfering with safety features / systems previously analyzed. In various embodiments, the energy absorber assemblies described herein use chemical slurries as a means to increase performance and facilitate tube filling. In various embodiments, the energy absorber assemblies described herein allow for the elimination of cooling and ice making systems within the power plant and / or allow for the elimination of mid-deck doors.

[0051] In various embodiments, the energy absorber assemblies described herein provide improved energy absorption relative to the original ice, adding a safety margin to the plant's ability to withstand beyond design-based conditions. In certain embodiments, sump water not produced through ice melt is replaced by modifying switchover times between the refueling water storage tank and the sump for the safety pumps, additional technical specification volumetric requirements on the refueling water storage tank (which may define additional tanks), and / or using potentially additional means to deliver sodium tetraborate and / or suitable buffers / boron forms to maintain desired sump chemistry.

[0052] Employment of the energy absorber assemblies described herein results in one or more benefits over existing ice condenser power plants, such as, for example, elimination of the need for additional cavity cooling and therefore systems, elimination of the glycol system that cools the ice store floor and has a dedicated chiller, elimination of sublimation and the need for ice weighing / refilling during outages (major outage operations), elimination of mid-deck doors, elimination of weekly containment intrusions at power up to inspect the mid-deck doors (lower dose), minimization of outage costs, duration, and personnel needs, elimination of ice melting concerns in some plants, and improved safety margins beyond design-based events.

[0053] Various aspects of the subject matter described herein are illustrated in the following examples.

[0054] (Example 1) - An apparatus for absorbing energy in a nuclear reactor containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; and a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes, the heat absorbing material being configured to undergo an endothermic reaction within the plurality of elongated tubes.

[0055] (Example 2) - The apparatus of Example 1, further comprising a support structure for holding the plurality of elongated tubes.

[0056] (Example 3) - The apparatus of Example 1 or Example 2, wherein the plurality of elongated tubes stack one assembly onto another assembly.

[0057] (Example 4) - An apparatus described in any one of Examples 1 to 3, wherein each of the plurality of elongated tubes further comprises a free space not occupied by the endothermic material, the free space being for accommodating gas produced during use by a chemical reaction of the endothermic material.

[0058] (Example 5) - The device of any one of Examples 1 to 4, wherein the plurality of elongated tubes are sealed.

[0059] (Example 6) - The apparatus of any one of Examples 1 to 4, wherein the plurality of elongated tubes are vented and further comprise a pressure relief valve.

[0060] Example 7 - The apparatus of any one of Examples 1 to 4, wherein the endothermic material is ammonium carbamate.

[0061] Example 8 - The apparatus of Example 7, wherein the plurality of elongated tubes are vented and the ammonium carbamate reaction product is released by venting as a buffer for sump water within a containment structure.

[0062] Example 9 - The apparatus of any one of Examples 1 to 8, wherein the endothermic material is in the form of a slurry.

[0063] Example 10 - The apparatus of example 9, wherein the slurry comprises a liquid mixed with ammonium carbamate.

[0064] (Example 11) - The device of Example 10, wherein the liquid is a solvent.

[0065] (Example 12) - The device of example 10 or example 11, wherein the liquid is selected from the group consisting of water, alcohol, ethylene glycol, and propylene glycol.

[0066] (Example 13) - A device described in any one of Examples 1 to 12, wherein at least one of the plurality of elongated tubes is cylindrical in shape.

[0067] (Example 14) - The device of any one of Examples 1 to 13, wherein at least one of the plurality of elongated tubes is non-cylindrical.

[0068] (Example 15) - An apparatus as described in any one of Examples 1 to 14, wherein each of the plurality of elongated tubes has a wall having a thickness ranging from less than 3 / 100 inch to 1 / 100 inch.

[0069] (Example 16) - The apparatus of any of Examples 1 to 15, wherein the amount of heat absorbing material is sufficient to remove energy from the containment structure upon initial energy release resulting from an accident and to later remove heat during fuel reduction.

[0070] (Example 17) - The device of any one of Examples 1 to 16, wherein the plurality of elongated tubes have fins.

[0071] (Example 18) - The apparatus of any one of Examples 1 to 17, wherein the plurality of elongated tubes have a non-linear configuration to improve condensation performance.

[0072] (Example 19) - An apparatus for absorbing energy in a nuclear reactor containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; and a compound configured to undergo thermal decomposition within the plurality of elongated tubes, the plurality of elongated tubes being at least partially occupied by the compound.

[0073] (Example 20) - The device of Example 19, further comprising a support structure for holding the plurality of elongated tubes.

[0074] As one of ordinary skill in the art will recognize, the terms used herein in general, and in the appended claims in particular (e.g., the body of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but not limited to," etc.). As one of ordinary skill in the art will further appreciate, where a specific number is intended in an introduced claim recitation, such intent will be expressly recited in the claim, and in the absence of such recitation, such intent does not exist. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases, when introducing claim matter with the indefinite article "a" or "an," should not be construed as suggesting that any particular claim that includes such introduced claim matter is limited to claims that include only one such matter, even if the same claim contains the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should typically be construed to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim matter.

[0075] In addition, even when specific numbers are explicitly recited in an introduced claim recitation, one of ordinary skill in the art would recognize that such recitations should typically be interpreted to mean at least the recitation number (e.g., the unqualified recitation "two recitations" without any other qualifiers typically means at least two recitations or more than two recitations). Furthermore, in instances where a notation approximating "at least one of A, B, and C, etc." is used, such syntax is generally intended in the sense that one of ordinary skill in the art would understand the notation (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or all of A, B, and C, etc.). In instances where a notation approximating "at least one of A, B, or C, etc." is used, such syntax is generally intended in the sense that one of skill in the art would understand the notation (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or all of A, B, and C, etc.). Furthermore, as would be understood by one of skill in the art, disjunctive words and / or phrases, typically presenting two or more terms to be chosen, should be understood to contemplate the possibility of including one of those terms, either of those terms, or both of those terms, unless the context otherwise requires, whether in the description, claims, or drawings.For example, the phrase "A or B" will typically be understood to include the possibilities of "A," "B," or "A and B."

[0076] With respect to the scope of the appended claims, as one of ordinary skill in the art would recognize, the operations described herein may generally be performed in any order. Also, while various operational flow diagrams are presented in a sequence, it should be understood that various operations may be performed in orders other than those illustrated, or may be performed in parallel. Examples of such alternative orderings may include overlapping, interleaved, interrupted, reordered, progressive, preliminary, supplemental, simultaneous, reverse, or other variant orderings, unless the context otherwise requires. Moreover, terms such as "responsive to," "related to," or other past tense adjectives are generally not intended to exclude such variants, unless the context otherwise requires.

[0077] It is worth noting that any reference to "one aspect," "an aspect," "an exemplification," "one example," or the like means that a particular feature, structure, or characteristic described in connection with that aspect is included in at least one aspect. Thus, the appearances of the phrases "in one aspect," "in an aspect," "in an example," and "in one example" in various places throughout this specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

[0078] Any patent applications, patents, non-patent publications, or other disclosure material referenced in this specification and / or listed in any Application Data Sheets is incorporated herein by reference to the extent that the incorporated material is not inconsistent with this specification. As such, and to the extent necessary, the disclosure expressly set forth in this specification takes precedence over any conflicting material incorporated herein by reference. Any material, or portions thereof, that is said to be incorporated herein by reference but that conflicts with existing definitions, statements, or other disclosure material set forth herein, is incorporated only to the extent that no conflict occurs between the incorporated material and the existing disclosure material.

[0079] The terms "comprise" (also any form of comprise, e.g., "comprises" and "comprising"), "have" (also any form of have, e.g., "has" and "having"), "include" (also any form of include, e.g., "includes" and "including"), and "contain" (also any form of contain, e.g., "contains" and "containing") are open-ended linking verbs. As a result, a system that "comprises", "has", "contains", or "containing" one or more elements may possess those one or more elements, but is not limited to possessing only those one or more elements. Similarly, an element of a system, device, or apparatus that "comprises", "has", "contains", or "containing" one or more features may possess those one or more features, but is not limited to possessing only those one or more features.

[0080] In summary, numerous benefits resulting from the use of the concepts described herein have been described. The foregoing description of one or more forms has been presented for purposes of illustration and description. It is not intended to be exhaustive or to be limited to the precise form disclosed. Modifications or variations are possible in light of the above teachings. One or more forms have been selected and described in order to illustrate the principles and practical applications, thereby enabling those skilled in the art to utilize various forms, with various modifications, as suitable for the particular applications contemplated. It is intended that the claims submitted herewith will define the overall scope.

Claims

1. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; The apparatus further comprises: a support structure for holding the plurality of elongated tubes; a plurality of said assemblies; The apparatus, wherein the assemblies are stacked in an axial direction of the elongated tubes, with the elongated tubes of one assembly stacked on top of the elongated tubes of another assembly.

2. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; Each of the plurality of elongated tubes further comprises a free space not occupied by the heat absorbing material, the free space being for accommodating gas produced in use by a chemical reaction of the heat absorbing material.

3. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; The apparatus of claim 2, wherein the plurality of elongated tubes are sealed.

4. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; the plurality of elongated tubes are vented; The apparatus, wherein the plurality of elongated tubes further comprise a pressure relief valve.

5. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; The apparatus, wherein the endothermic material is ammonium carbamate.

6. 6. The apparatus of claim 5, wherein when the plurality of elongated tubes are vented and the ammonium carbamate reaction product is released, the released ammonium carbamate reaction product acts as a buffer for sump water within a containment structure.

7. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; The apparatus, wherein the heat absorbing material is in the form of a slurry.

8. 8. The apparatus of claim 7, wherein the slurry comprises a liquid mixed with ammonium carbamate.

9. The apparatus of claim 8 , wherein the liquid is a solvent.

10. 10. The device of claim 8 or 9, wherein the liquid is selected from the group consisting of water, alcohol, ethylene glycol, and propylene glycol.

11. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a heat absorbing material contained within each of the plurality of elongated tubes and occupying a majority of each of the plurality of elongated tubes; the heat absorbing material is configured to undergo an endothermic reaction within the plurality of elongated tubes; The apparatus, wherein each of the plurality of elongated tubes has a wall having a thickness ranging from less than 3 / 100 inch to 1 / 100 inch.

12. The apparatus of claim 1 , wherein at least one of the plurality of elongated tubes is cylindrical in shape.

13. The apparatus of claim 1 , wherein at least one of the plurality of elongated tubes is non-cylindrical in shape.

14. The apparatus of claim 1 , wherein the plurality of elongated tubes have fins.

15. 1. An apparatus for absorbing energy in a nuclear containment structure, comprising: at least one assembly comprising a plurality of elongated tubes; a compound configured to undergo thermal decomposition within the plurality of elongated tubes; The plurality of elongated tubes are at least partially occupied by the compound.

16. The apparatus further comprises: The apparatus of claim 15 , further comprising a support structure for holding the plurality of elongated tubes.

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