A single-shell soft-shield design method for resisting commercial aircraft impacts and a nuclear power plant

Abstract

This invention belongs to the field of nuclear power plant impact protection technology, specifically relating to a single-shell soft-protection design method and a nuclear power plant for resisting commercial aircraft impacts. The "single-shell soft-protection" concept is used to design the nuclear island building of a nuclear power plant, including a single-layer containment design and other nuclear island building designs. The advantages of this invention are: it proposes a "single-shell soft-protection" design concept, which involves software analysis of the single-layer containment and other nuclear island building designs, combined with evaluation results, to adjust the designs until the requirements are met; the design process no longer requires ensuring structural integrity, but rather achieves nuclear power plant resistance to commercial aircraft impacts by maintaining the cooling of the reactor core and spent fuel, thus eliminating the aircraft impact condition as a controlling factor in the structural design of the nuclear island building.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant impact protection technology, specifically relating to a single-shell soft-shield design method for resisting the impact of commercial large aircraft and a nuclear power plant. Background Technology

[0002] Nuclear safety regulations clearly state that the design of nuclear power plants should take into account the impact of a commercial aircraft collision, and that the design must be evaluated to prove that it can maintain reactor core cooling or containment integrity, as well as spent fuel cooling or spent fuel pool integrity.

[0003] Currently, the design of nuclear island buildings for third-generation pressurized water reactor nuclear power technologies (such as Hualong One, EPR, and AP1000) both domestically and internationally considers the impact of commercial aircraft collisions. According to regulatory guidelines, the assessment of the effects of a commercial aircraft impact on a nuclear power plant, in addition to the overall and local penetration effects on the plant's structures, also needs to consider the vibration effects of the impact and the spread of fuel fires on related mechanical and electrical equipment. Based on the assessment of these effects, the integrity of the reactor core cooling system or containment structure is demonstrated.

[0004] To ensure that nuclear power plants can maintain core cooling or containment integrity in the event of a commercial aircraft impact, the typical protection strategy for nuclear power plants is to completely block the commercial aircraft from entering the nuclear island building by setting up a separate protective layer of nearly 2 meters on the outside of the building. This ensures the integrity of the inner containment and prevents other systems that maintain core cooling from failing. Under this protection strategy, the aircraft impact scenario, as an above-design baseline scenario, becomes the control scenario for nuclear power plant structural design. The economic indicators are not high. This strategy is called "hard-hit" protection.

[0005] Currently, most third-generation pressurized water reactor nuclear power technologies, both domestically and internationally, employ a "hard-line" approach to protect against commercial aircraft impacts. For example, Chinese invention patent CN110067428 proposes a method and system for protecting nuclear power plants from commercial aircraft impacts. This method involves installing impact-resistant structures in the reactor building, spent fuel storage building, and electrical and instrumentation building. Simultaneously, two rows of redundant dedicated safety buildings and their functional support buildings are physically isolated from the impact-resistant structures. Protective structures are also installed at any openings or holes in the impact-resistant structures, thus achieving protection against the four effects of a large aircraft impact (i.e., overall stability, local penetration effect, vibration effect, and fire effect). For another example, Chinese invention patent CN110043099 proposes a simplified protection method and system for nuclear power plants against commercial aircraft impacts. This method eliminates the inner walls of the fuel building and electrical building, using only the outer shell to completely shield the aircraft, thereby ensuring the integrity of the inner containment structure, the outer walls of the fuel building, and the outer walls of the electrical building. For example, Chinese utility model CN208122396 discloses a nuclear power plant anti-aircraft impact structure, which includes a plant building enclosed by an outer wall, an arc-shaped structural wall on the upper part of the plant building, and an arc-shaped roof on the upper part of the arc-shaped structural wall. The arc-shaped configuration reduces the impact effect of an aircraft collision, thus achieving anti-aircraft impact capability. For example, Chinese invention patent CN112664012 proposes a protective armor for reinforcing a nuclear power plant building to resist aircraft impacts, and a nuclear power plant building reinforced with protective armor to resist aircraft impacts, establishing a shielding layer to resist aircraft impacts. These protection strategies, whether in terms of the protection system or the localized reinforcement structure, are essentially "hard-hitting" defense methods. Some patents slightly improve the economic efficiency of nuclear power structures, but do not substantially improve the economic benefits of nuclear power.

[0006] In addition, since the requirements for nuclear power plants to withstand commercial aircraft impacts were only in place after the 9 / 11 attacks, and nuclear power plants built before that were not designed in accordance with the relevant guidelines, it is impossible to conduct an assessment of the impact resistance of existing power plants against commercial aircraft impacts using a hard-line protection strategy. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a single-shell soft-shield design method and nuclear power plant that can withstand the impact of commercial aircraft. Instead of using the commercial aircraft impact as an out-of-design baseline event to control and influence the design of the nuclear power plant, this invention utilizes existing designs to conduct safety analysis under aircraft impact and employs arrangement methods to enable the nuclear power plant to withstand the impact of commercial aircraft.

[0008] The technical solution of the present invention is as follows:

[0009] A single-shell soft containment design method to withstand the impact of a commercial aircraft adopts the concept of "single-shell soft containment" to design a nuclear power plant nuclear island building design scheme, which includes a single-layer containment design scheme and other nuclear island building design schemes.

[0010] For the preliminary design scheme of single-layer prestressed reinforced concrete containment vessel, the impact-reachable area of ​​the aircraft was screened. For the screened area, mechanical simulation data of the single-layer containment vessel in that area was obtained. Based on the mechanical simulation data, the structural integrity, equipment integrity, and fuel infiltration of the containment vessel after impact were analyzed. The analysis results were used to determine whether the reactor core inside the containment vessel could maintain cooling after impact. If it could maintain cooling, the current design scheme was adopted; otherwise, the containment vessel design scheme was further optimized until it could maintain cooling.

[0011] For other preliminary nuclear island building design schemes, the areas accessible by aircraft impact are screened. For the screened areas, the range of physical damage, vibration impact range, and fire impact range are analyzed. The analysis results determine whether the reactor core and spent fuel can maintain cooling after impact. If they can maintain cooling, the scheme is adopted; otherwise, the design scheme is adjusted until the scheme determines that the reactor core and spent fuel can maintain cooling after impact.

[0012] The design schemes for a single-layer prestressed reinforced concrete containment capable of maintaining cooling and other nuclear island building designs capable of maintaining cooling of the reactor core and spent fuel after impact were determined to arrive at the final nuclear island building design scheme for the nuclear power plant.

[0013] A single-shell soft containment design method for resisting impacts from large commercial aircraft is used to design nuclear island building schemes for nuclear power plants. This method includes a single-layer containment design scheme and other nuclear island building schemes, and comprises the following steps:

[0014] Step 1: For the preliminary design scheme of single-layer prestressed reinforced concrete containment structure, screen the areas that can be reached by aircraft impact, and obtain the mechanical simulation data of the single-layer containment structure in the screened areas.

[0015] Step 2: Based on the mechanical simulation data obtained in Step 1, analyze the structural integrity of the containment vessel after the impact, the integrity of the equipment, and whether there is fuel leakage.

[0016] The A1 module is used to determine whether the containment structure can guarantee the integrity of the prestressed reinforced concrete structure.

[0017] The A2 module is used to determine whether there is sufficient clearance between the prestressed reinforced concrete containment vessel and the reactor structure to prevent equipment vibration damage, i.e., equipment integrity.

[0018] The A3 module calculates the amount of fuel that has entered the containment, thus determining whether there has been fuel infiltration.

[0019] If the judgment results of A1, A2, and A3 in Step 3 and Step 2 all meet the design requirements, then the safety analysis of maintaining core cooling inside the shell can be carried out. If any one or more of them do not meet the design requirements, the single-shell design scheme will be adjusted until all the output results of A1, A2, and A3 modules meet the requirements.

[0020] Step 4: Determine the physical damage assessment criteria, vibration effect assessment criteria, and fire effect assessment criteria respectively;

[0021] Step 5: Analyze the physical damage range, vibration impact range, and fire impact range of other nuclear island buildings using the obtained physical damage assessment criteria, vibration effect assessment criteria, and fire effect assessment criteria.

[0022] Step 6: For other preliminary nuclear island plant design schemes, screen the areas accessible by aircraft impact. For the screened areas, determine whether the reactor core and spent fuel can maintain cooling after an impact.

[0023] The design schemes for a single-layer prestressed reinforced concrete containment capable of maintaining cooling and other nuclear island building designs capable of maintaining cooling of the reactor core and spent fuel after impact were determined to arrive at the final nuclear island building design scheme for the nuclear power plant.

[0024] Step 4 specifically includes:

[0025] Step 4.1: Determine the evaluation criteria for physical damage boundaries, and then perform physical damage range analysis on the screened areas;

[0026] The evaluation criteria for the physical damage boundary are determined as follows:

[0027] a) Determine the impact energy absorption coefficient of walls of different thicknesses in other nuclear island buildings; the thickness range is 0.1-1.5m;

[0028] b) The evaluation criteria for physical damage boundary are obtained by superimposing the impact energy absorption coefficients of different walls;

[0029] Step 4.2: Determine the evaluation criteria for vibration effects, and then analyze the vibration impact range of the selected area;

[0030] a) Determine the calculated vibration effects of other nuclear island buildings under aircraft impact;

[0031] b) Determine the evaluation criteria for vibration effects by observing the attenuation law of stress wave transmission.

[0032] Step 4.3: Determine the assessment criteria for fire effects, and then conduct a fire impact range analysis on the selected areas;

[0033] a) Determine the calculated fire effects on other nuclear island buildings under aircraft impact;

[0034] (b) Based on the analysis of pressure fire and spread fire in the nuclear island plant under aircraft impact, the assessment criteria for fire effects are given.

[0035] Step 5 specifically includes:

[0036] For other nuclear island buildings, the scope of physical damage, vibration impact, and fire impact are analyzed, and three analysis modules, B1, B2, and B3, are designed accordingly. Module B1 analyzes the scope of physical damage to the nuclear island buildings under aircraft impact; module B2 analyzes the scope of vibration impact; and module B3 analyzes the scope of fire impact.

[0037] The wall energy absorption coefficient in step 4 is obtained by aircraft impact calculation and analysis. It is characterized by the ability of the outer wall to consume energy through its own deformation under dynamic impact. Its value is 0-1, and it is obtained by the percentage of the energy consumed by the wall's own deformation in the aircraft impact energy in the physical damage boundary simulation calculation and analysis results.

[0038] The physical damage boundary assessment criterion in step 4 is to analyze and superimpose the energy absorption factors of the outer and inner walls of other nuclear island plant buildings under aircraft impact. Finally, the last wall with a value greater than 1 is taken as the physical damage boundary area of ​​the plant under the impact of a commercial aircraft.

[0039] The vibration effect calculation in step 4 refers to the simulation calculation analysis of the possible impact zone conditions of other nuclear island buildings under aircraft impact, to obtain the floor acceleration values ​​of the possible placement positions of equipment in other nuclear island buildings under different operating conditions.

[0040] The vibration effect assessment criteria in step 4 are obtained by combining the calculation results of step 4.2a) with the stress wave attenuation law to obtain the vibration safety distance of various equipment in nuclear power plants. If the distance between the equipment's location and the aircraft impact point is greater than or equal to the vibration safety distance of that type of equipment, the equipment can survive the aircraft impact condition; otherwise, the equipment will fail.

[0041] The fire effect assessment criterion in step 4 uses the physical damage boundary as the starting point of the fire. Through fireball spread analysis and in conjunction with the installation of fire doors, the fire impact boundary is finally determined, and the fire impact range of the factory building under the impact of a commercial aircraft collision is judged.

[0042] Step 6 specifically includes:

[0043] Identify all systems and equipment outside the range of physical damage, vibration, and fire, and determine whether these systems and equipment can maintain core and spent fuel cooling after the impact;

[0044] If the conditions are met, then other nuclear island plant design schemes are feasible at this time;

[0045] If the conditions are not met, then within any one or more of the three ranges of physical damage impact, vibration impact, and fire impact, select the systems and equipment related to core and spent fuel cooling for relocation adjustment, and then determine whether the adjusted systems and equipment can maintain core and spent fuel cooling after the impact; until all systems and equipment related to core and spent fuel cooling within any one or more of the impact ranges can maintain core and spent fuel cooling after the impact.

[0046] Step 1 specifically involves first establishing a detailed three-dimensional solid model of the containment for the single-shell containment design scheme, including a three-dimensional model of the plant and a three-dimensional model of the aircraft; then using LS-DYNA dynamic analysis software to obtain the calculation and analysis results.

[0047] Step 2 specifically includes:

[0048] The structural integrity of the prestressed reinforced concrete containment is assessed by whether the concrete section damage extends through the entire prestressed reinforced concrete section. The deformation and displacement results of the containment are used to assess whether there is sufficient clearance between the containment and the reactor structure to prevent vibration damage to the equipment. The results of whether the cracks in the containment impact area extend through the containment are used to assess whether a large amount of fuel oil has entered the containment and caused secondary consequences.

[0049] In step 3, the single-shell design scheme is adjusted, including increasing the thickness of the containment shell, increasing the concrete strength, increasing the reinforcement ratio, and applying new materials.

[0050] The increase in containment thickness is in increments of 0.05-0.1m; the increase in concrete strength is in increments of 5 MPa; the increase in reinforcement ratio is in increments of 0.05-0.1%; and the new material refers to UPHC or ECC concrete.

[0051] If the relevant systems and equipment cannot guarantee the core cooling function in step 6, then the reactor is considered unviable. The specific determination process is as follows:

[0052] Using the acceleration time history curve as an external load, a fine finite element simulation analysis was performed using finite element analysis software to determine whether the equipment was viable.

[0053] If all are determined to be alive, then the process ends;

[0054] If the reactor still does not survive, further measures are taken to add vibration damping and energy absorption devices or optimize the equipment system layout. Then, the core cooling analysis is repeated until the core cooling function is met, and the process ends.

[0055] A single-shell soft-shield nuclear power plant designed to withstand the impact of a commercial aircraft, wherein the containment vessel and other nuclear island building structures of the nuclear power plant adopt the design scheme described above.

[0056] The nuclear power plant's nuclear island building includes a single-layer containment reactor building and other nuclear island buildings.

[0057] A single-layer containment structure with prestressed reinforced concrete is used to withstand the impact of a large commercial aircraft. In the impact zone, the single-layer containment remains intact and maintains the core cooling function.

[0058] The arrangement of nuclear safety-related systems and equipment ensures that the reactor core and spent fuel remain cooled under the physical damage boundary, vibration damage boundary, and fire-affected area under aircraft impact.

[0059] The arrangement of nuclear safety-related systems and equipment ensures that the reactor core and spent fuel remain cooled under the physical damage boundary, vibration damage boundary, and fire-affected area under aircraft impact.

[0060] The beneficial effects of this invention are as follows:

[0061] (1) This invention proposes the design concept of "single-shell soft protection", which involves software analysis of the design schemes of single-layer containment and other nuclear island buildings, and adjustment of the schemes based on the evaluation results until the evaluation requirements are met. The design process no longer requires ensuring the integrity of the structure, but rather achieves the nuclear power plant's resistance to commercial aircraft impacts by maintaining the cooling of the reactor core and spent fuel, so that the aircraft impact condition is no longer the controlling condition for the structural design of the nuclear island building. The so-called "single-shell" refers to the single-layer prestressed reinforced concrete containment for the reactor building of the nuclear power plant. The so-called "soft protection" refers to the analysis and evaluation of the design schemes of single-layer containment and other nuclear island buildings through calculation software.

[0062] (2) After the outer containment structure is removed, the outer wall of the nuclear island is thinned and the special equipment for aircraft impact resistance is reduced, which reduces the cost and improves the economic efficiency of my country's nuclear power technology.

[0063] (3) Eliminating the outer containment layer will greatly reduce the difficulty of construction and shorten the construction period;

[0064] (4) The design proposed in this invention is a protective design for large aircraft impacts. It comprehensively considers the damage, vibration and fuel effects caused by aircraft impacts. It not only substantially achieves system protection for nuclear power plants against commercial large aircraft, but also has the ability to assess the impact resistance of in-service nuclear power plants against aircraft impacts, and can provide targeted suggestions, reduce public doubts, and has social benefits. Attached Figure Description

[0065] Figure 1 Flowchart for analyzing a new method of single-shell soft-shield design;

[0066] Figure 2 This is a schematic diagram of the physical damage boundary and fire extent in section 2a.

[0067] Figure 3 This is a schematic diagram showing the vibration safety distance location for equipment 2b.

[0068] Figure 4 This is a schematic diagram of a single-shell soft-shield nuclear power plant designed to withstand the impact of a commercial aircraft, as provided by the present invention.

[0069] In the diagram: 1 Single-layer containment reactor building, 2 Other nuclear island buildings, 3 Core cooling first related equipment, 4 Nuclear island building exterior wall, 5 Nuclear island building partition wall, 6 Fire boundary wall, 7 Fireball caused by aircraft impact. Detailed Implementation

[0070] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described in the present invention are merely illustrative and not intended to limit the scope of the invention.

[0071] The technical problem to be solved by this invention is to form a new protection method against the impact of commercial aircraft through the design scheme of the containment vessel and nuclear island plant. This method greatly improves the economic efficiency while ensuring the safety of nuclear power plants. Furthermore, this method can be used to conduct aircraft impact assessments on existing power plants and to make partial modifications to existing power plants based on the assessment results to meet the requirements for impact resistance to commercial aircraft.

[0072] (1) The outer protective layer blocking commercial aircraft is removed, and the double-layer containment building of the nuclear island is adjusted to a single-layer containment building. No redundant system is added separately for commercial aircraft collisions.

[0073] (2) The reactor building is designed with a “single shell” (single-layer prestressed reinforced concrete containment) to demonstrate that aircraft will not enter the nuclear reactor to ensure structural integrity, equipment will not be damaged by vibration, and a large amount of fuel will not enter the containment in case of fire.

[0074] (3) Instead of adding redundant core cooling systems, the structure, vibration and fire effects of other nuclear island buildings are demonstrated and adjusted through the "soft defense" method, so that they can withstand the impact of commercial aircraft.

[0075] A single-shell soft-shield design method for resisting impacts from large commercial aircraft includes the following steps:

[0076] Step 1: Perform mechanical response simulation calculation and analysis on the containment vessel to obtain the calculation results of the containment vessel under the impact condition of a commercial large aircraft;

[0077] Step 2: Based on the calculation and analysis results of Step 1 above, conduct a response assessment of the containment mechanics to determine whether the containment can ensure the integrity of the prestressed reinforced concrete structure, whether there is sufficient spacing between the prestressed reinforced concrete containment and the reactor structure to prevent equipment vibration damage, and whether a large amount of fuel oil will enter the containment.

[0078] Step 3: If the above analysis results all meet the requirements, the next step of maintaining core cooling safety analysis can be carried out. If the requirements are not met, the single-shell design scheme is adjusted, and steps 1, 2, and 3 are executed until the requirements are met.

[0079] Step 4: Conduct simulation calculations and analyses of the physical damage boundaries of other nuclear island buildings under aircraft impact to obtain the energy absorption coefficients of walls with different thicknesses;

[0080] Step 5: Assessment criteria for the physical damage boundary of the nuclear island plant under aircraft impact by obtaining system energy;

[0081] Step 6: Perform vibration effect calculations on other nuclear island buildings under aircraft impact, and obtain the calculation results of the vibration effect of nuclear island buildings under aircraft impact;

[0082] Step 7: Evaluation criteria for vibration effects obtained by studying the attenuation law of stress wave transmission in the nuclear island plant under aircraft impact.

[0083] Step 8: Calculate the fire effects of other nuclear island buildings under aircraft impact and obtain the calculation results of the fire effects of other nuclear island buildings;

[0084] Step 9 provides an assessment criterion for the fire effect by analyzing the pressure fire and spread fire in the nuclear island plant under the impact of an aircraft.

[0085] Step 10 uses the physical damage assessment criteria, vibration effect assessment criteria, and fire effect assessment criteria from steps 5, 7, and 9 to determine the extent of physical damage, vibration impact, and fire impact on the nuclear island building under aircraft impact. Systems and equipment outside these three impact ranges are deemed to be able to maintain their functionality.

[0086] Step 11 involves conducting a safety analysis of the arrangement of nuclear safety-related systems and equipment to maintain core cooling.

[0087] Step 12: If Step 11 fails to meet the requirements for maintaining core cooling, conduct a detailed analysis of the equipment that failed the test. If it still fails, adjust and optimize the positions of the relevant systems and equipment, and conduct another safety analysis to maintain core cooling until the requirements are met.

[0088] The aforementioned nuclear power plant core cooling system equipment can ensure core cooling function under aircraft impact conditions;

[0089] Example 1:

[0090] (1) For the single-shell design scheme of the containment, firstly, for possible aircraft impact conditions, a refined finite element analysis model is established, including a three-dimensional model of the factory and a three-dimensional model of the aircraft. The LS-DYNA dynamic analysis software is used to perform dynamic impact simulation analysis on the containment under various aircraft impact conditions.

[0091] (2) By judging the damage state of concrete under various impact conditions, such as whether the concrete forms through-damage, it is confirmed whether the structural integrity of the prestressed reinforced concrete containment can be guaranteed. Then, by checking whether there is enough distance between the prestressed reinforced concrete containment and the internal structure of the reactor, it is determined whether the reactor core can maintain its function under aircraft impact conditions. Finally, the crack development after impact damage conditions is obtained by numerical simulation to determine the fuel crack penetration and assess whether fuel has entered the containment.

[0092] (3) Based on the above structural, vibration and fire analysis results, conduct a core cooling analysis on the containment to determine whether the core cooling function can be maintained under the current design scheme. If yes, the containment-related analysis ends and the containment's resistance to aircraft impact can be guaranteed. If the core cooling function cannot be maintained, the original design scheme needs to be improved, such as increasing the containment thickness, increasing the concrete strength, increasing the reinforcement ratio and applying new materials. Continue to conduct (1) analysis until the core cooling function can be maintained and the process ends.

[0093] (4) For potential impact scenarios of other nuclear island buildings, the energy absorption factors of the outer and inner walls of the nuclear island buildings under aircraft impact conditions are analyzed and superimposed according to the physical damage assessment criteria in this invention. The physical damage boundary range is confirmed based on the criterion that the last wall with a superposition value greater than 1 is the physical damage boundary region of the building under the impact of a commercial large aircraft. Figure 2 The physical damage boundary range is shown.

[0094] (5) For potential impact scenarios in other nuclear island buildings, vibration analysis safety distances for various equipment are used to determine whether the core cooling equipment would survive an aircraft impact. The specific method involves using the impact location as the starting analysis point, comparing the safety distance of each piece of equipment from the impact point with its vibration safety distance, based on the path distance of each piece of equipment to the impact point under aircraft impact conditions. Figure 3 A schematic analysis is performed. The path distance between the device and the impact point is D. If D is greater than the vibration safety distance for this type of device, the device is considered to be alive. If D is less than the vibration safety distance for this type, the device is considered not to be alive.

[0095] (6) Finally, using the physical damage boundary as the starting point of the fire, and through fireball spread analysis combined with the installation of fire doors, the impact boundary of the fire was ultimately determined, and the fire impact range of the factory building under the impact of a commercial aircraft collision was assessed. Figure 2 The fire boundary range is shown.

[0096] (7) Based on the calculation results of physical damage boundary, vibration effect and fire impact area in steps (4), (5) and (6) above, conduct a containment analysis on whether to maintain the reactor core according to the arrangement of equipment, instruments and other items that can survive after the above analysis, and evaluate whether at least one reactor core cooling function sequence can be maintained under aircraft impact conditions. If reactor core cooling can be guaranteed, then the analysis process ends.

[0097] (8) If the core cooling function cannot be guaranteed, then first perform a fine finite element simulation analysis on the relevant equipment systems that cannot survive under the action of acceleration time history curves, and determine whether the equipment survives under the fine analysis. If it is determined that all survive, then end the process.

[0098] (9) If the equipment still does not survive in the core cooling sequence in step (8) above, further add vibration damping and energy absorption devices to the equipment or optimize the equipment system layout, and then re-perform the core cooling analysis until the core cooling function is met, and then end the process.

[0099] like Figure 4 As shown, a nuclear power plant designed to withstand the impact of a large commercial aircraft using a single-shell soft protection method includes a single-layer containment reactor building 1, other nuclear island buildings 2, core cooling related equipment, nuclear island building exterior wall 4, nuclear island building partition wall 5, and fire boundary wall 6.

[0100] Single-layer containment reactor building 1: The outer containment is eliminated, and a single-layer prestressed reinforced concrete structure is used to withstand the impact of a commercial aircraft. At the location where the aircraft may hit, such as impact point 1, the single-layer containment can still maintain its integrity and ensure the core cooling function.

[0101] Other nuclear island building 2: The physical damage boundary (physical damage range), vibration damage boundary and fire-affected area under aircraft impact can be ensured by the reasonable arrangement of nuclear safety related systems and equipment, so as to ensure the cooling of the reactor core and spent fuel under aircraft impact.

[0102] The design concept for the outer wall of the nuclear island plant has been changed from being entirely protected by the outer wall to being composed of a physical damage boundary formed by both the outer wall and the inner wall.

[0103] The nuclear island plant building has partition wall 5. Assuming the physical damage boundary is controlled at wall 5, walls 4 and 5 work together to dissipate energy and prevent aircraft from entering the plant. If wall 5 cannot stop the aircraft, more partition walls can be added to achieve the same energy dissipation effect.

[0104] Fire boundary wall 6: The fire spread from the aircraft impact is controlled within the boundary of fire boundary wall 6 to ensure that the interior of the wall is not affected. Fireball 7 caused by the aircraft impact: The fireball spread is controlled within fire boundary wall 6.

[0105] Figure 4 A schematic diagram of a nuclear power plant designed according to the "single-shell soft protection" concept is presented. This is only shown as one embodiment of the present invention and does not represent all the contents of the present invention.

[0106] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and equivalents, this invention is also intended to include them.

Claims

1. A single-shell soft containment design method for resisting impacts from large commercial aircraft, used to design and form a nuclear power plant nuclear island building design scheme, comprising a single-layer containment design scheme and other nuclear island building design schemes, characterized in that, Includes the following steps: Step 1: For the preliminary design scheme of single-layer prestressed reinforced concrete containment structure, screen the areas that can be reached by aircraft impact, and obtain the mechanical simulation data of the single-layer containment structure in the screened areas. Step 2: Based on the mechanical simulation data obtained in Step 1, analyze the structural integrity of the containment vessel after the impact, the equipment integrity, and whether there is fuel leakage. The A1 module is used to determine whether the containment structure can guarantee the integrity of the prestressed reinforced concrete structure. The A2 module is used to determine whether there is sufficient clearance between the prestressed reinforced concrete containment vessel and the reactor structure to prevent equipment vibration damage, i.e., equipment integrity. The A3 module calculates the amount of fuel that has entered the containment, thus determining whether there has been fuel infiltration. If the judgment results of A1, A2, and A3 in Step 3 and Step 2 all meet the design requirements, then the safety analysis of maintaining core cooling inside the shell can be carried out. If any one or more of them do not meet the design requirements, the single-shell design scheme will be adjusted until all the output results of A1, A2, and A3 modules meet the requirements. Step 4: Determine the physical damage assessment criteria, vibration effect assessment criteria, and fire effect assessment criteria respectively; Step 5: Analyze the physical damage range, vibration impact range, and fire impact range of other nuclear island buildings using the obtained physical damage assessment criteria, vibration effect assessment criteria, and fire effect assessment criteria. Step 6: For other preliminary nuclear island plant design schemes, screen the areas accessible by aircraft impact. For the screened areas, determine whether the reactor core and spent fuel can maintain cooling after an impact. The design schemes for a single-layer prestressed reinforced concrete containment capable of maintaining cooling and other nuclear island building designs capable of maintaining cooling of the reactor core and spent fuel after impact were determined to arrive at the final nuclear island building design scheme for the nuclear power plant.

2. The single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that, Step 4 specifically includes: Step 4.1: Determine the evaluation criteria for physical damage boundaries, and then perform physical damage range analysis on the screened areas; The evaluation criteria for the physical damage boundary are determined as follows: a) Determine the impact energy absorption coefficient of walls of different thicknesses in other nuclear island buildings; the thickness range is 0.1-1.5m; b) The evaluation criteria for physical damage boundary are obtained by superimposing the impact energy absorption coefficients of different walls; Step 4.2: Determine the evaluation criteria for vibration effects, and then analyze the vibration impact range of the selected area; a) Determine the calculated vibration effects of other nuclear island buildings under aircraft impact; b) Determine the evaluation criteria for vibration effects by observing the attenuation law of stress wave transmission. Step 4.3: Determine the assessment criteria for fire effects, and then conduct a fire impact range analysis on the selected areas; a) Determine the calculated fire effects on other nuclear island buildings under aircraft impact; (b) Based on the analysis of pressure fire and spread fire in the nuclear island plant under aircraft impact, the assessment criteria for fire effects are given.

3. The single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that, Step 5 specifically includes: For other nuclear island buildings, the scope of physical damage, vibration impact, and fire impact are analyzed, and three analysis modules, B1, B2, and B3, are designed accordingly. Module B1 analyzes the scope of physical damage to the nuclear island buildings under aircraft impact; module B2 analyzes the scope of vibration impact; and module B3 analyzes the scope of fire impact.

4. The single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 2, characterized in that: The wall energy absorption coefficient in step 4 is obtained by aircraft impact calculation and analysis. It is characterized by the ability of the outer wall to consume energy through its own deformation under dynamic impact. Its value is 0-1, and it is obtained by the percentage of the energy consumed by the wall's own deformation in the aircraft impact energy in the physical damage boundary simulation calculation and analysis results.

5. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 4, characterized in that: The physical damage boundary assessment criterion in step 4 is to analyze and superimpose the energy absorption factors of the outer and inner walls of other nuclear island plant buildings under aircraft impact. Finally, the last wall with a value greater than 1 is taken as the physical damage boundary area of ​​the plant under the impact of a commercial aircraft.

6. The single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 2, characterized in that: The vibration effect calculation in step 4 refers to the simulation calculation analysis of the possible impact zone conditions of other nuclear island buildings under aircraft impact, to obtain the floor acceleration values ​​of the possible placement positions of equipment in other nuclear island buildings under different operating conditions.

7. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 6, characterized in that: The vibration effect assessment criteria in step 4 are obtained by combining the calculation results of step 4.2a) with the stress wave attenuation law to obtain the vibration safety distance of various equipment in nuclear power plants. If the distance between the equipment's location and the aircraft impact point is greater than or equal to the vibration safety distance of that type of equipment, the equipment can survive the aircraft impact condition; otherwise, the equipment will fail.

8. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 2, characterized in that: The fire effect assessment criterion in step 4 uses the physical damage boundary as the starting point of the fire. Through fireball spread analysis and in conjunction with the installation of fire doors, the fire impact boundary is finally determined, and the fire impact range of the factory building under the impact of a commercial aircraft collision is judged.

9. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that, Step 6 specifically includes: Identify all systems and equipment outside the range of physical damage, vibration, and fire, and determine whether these systems and equipment can maintain core and spent fuel cooling after the impact; If the conditions are met, then other nuclear island plant design schemes are feasible at this time; If the conditions are not met, then within any one or more of the three ranges of physical damage impact, vibration impact, and fire impact, select the systems and equipment related to core and spent fuel cooling for relocation adjustment, and then determine whether the adjusted systems and equipment can maintain core and spent fuel cooling after the impact; until all systems and equipment related to core and spent fuel cooling within any one or more of the impact ranges can maintain core and spent fuel cooling after the impact.

10. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that: Step 1 specifically involves first establishing a detailed three-dimensional solid model of the containment for the single-shell containment design scheme, including a three-dimensional model of the plant and a three-dimensional model of the aircraft; then using LS-DYNA dynamic analysis software to obtain the calculation and analysis results.

11. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that, Step 2 specifically includes: The structural integrity of the prestressed reinforced concrete containment is assessed by whether the concrete section damage extends through the entire prestressed reinforced concrete section. The deformation and displacement results of the containment are used to assess whether there is sufficient clearance between the containment and the reactor structure to prevent vibration damage to the equipment. The results of whether the cracks in the containment impact area extend through the containment are used to assess whether a large amount of fuel oil has entered the containment and caused secondary consequences.

12. The single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that: In step 3, the single-shell design scheme is adjusted, including increasing the thickness of the containment shell, increasing the concrete strength, increasing the reinforcement ratio, and applying new materials.

13. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 12, characterized in that: The increase in containment thickness is in increments of 0.05-0.1m; the increase in concrete strength is in increments of 5 MPa; the increase in reinforcement ratio is in increments of 0.05-0.1%; and the new material refers to UPHC or ECC concrete.

14. A single-shell soft-shield design method for resisting impacts from commercial large aircraft as described in claim 1, characterized in that, If the relevant systems and equipment cannot guarantee the core cooling function in step 6, then the reactor is considered unviable. The specific determination process is as follows: Using the acceleration time history curve as an external load, a fine finite element simulation analysis was performed using finite element analysis software to determine whether the equipment was viable. If all are determined to be alive, then the process ends; If the reactor still does not survive, further measures are taken to add vibration damping and energy absorption devices or optimize the equipment system layout. Then, the core cooling analysis is repeated until the core cooling function is met, and the process ends.

15. A single-shell soft-shield nuclear power plant designed to withstand the impact of a large commercial aircraft, characterized in that: The design scheme for the containment vessel and other nuclear island buildings of the nuclear power plant adopts any one of the design methods as described in claims 10-14.

16. A single-shell soft-shield nuclear power plant designed to withstand the impact of a commercial large aircraft as described in claim 15, characterized in that: The nuclear power plant's nuclear island building includes a single-layer containment reactor building and other nuclear island buildings.

17. A single-shell soft-shield nuclear power plant designed to withstand the impact of a large commercial aircraft as described in claim 16, characterized in that: A single-layer containment structure with prestressed reinforced concrete is used to withstand the impact of a large commercial aircraft. In the impact zone, the single-layer containment remains intact and maintains the core cooling function.

18. A single-shell soft-shield nuclear power plant designed to withstand the impact of a commercial large aircraft as described in claim 15, characterized in that: The arrangement of nuclear safety-related systems and equipment ensures that the reactor core and spent fuel remain cooled under the physical damage boundary, vibration damage boundary, and fire-affected area under aircraft impact.

19. A nuclear power plant with a single-shell soft-shield design for resisting impacts from large commercial aircraft as described in claim 15, characterized in that: The arrangement of nuclear safety-related systems and equipment ensures that the reactor core and spent fuel remain cooled under the physical damage boundary, vibration damage boundary, and fire-affected area under aircraft impact.

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