A reactor core arrangement method and a reactor pressure vessel

Abstract

The application provides a reactor core arrangement method and a reactor pressure device, and the arrangement method is a reactor core arrangement method without a secondary neutron source, and specifically comprises the following steps: loading fuel assemblies and corresponding primary neutron sources in a first cycle core of a reactor; disassembling the primary neutron sources from the irradiated fuel assemblies in the first cycle core, and loading the primary neutron sources into first spent fuel assemblies to form a second cycle core start-up neutron source; disassembling the primary neutron sources from the irradiated fuel assemblies in the second cycle core, and loading the primary neutron sources into second spent fuel assemblies to form a third cycle core start-up neutron source; and disassembling the primary neutron sources from the irradiated fuel assemblies in the third cycle core, and performing a subsequent cycle of the core. The application realizes the purpose of improving the utilization rate of the primary neutron source of the reactor and canceling the setting of the secondary neutron source by reusing the primary neutron source in the first three cycles of the core and combining with the utilization of the neutrons emitted by the spent fuel assemblies in the previous cycle.

Description

Technical Field

[0001] This invention belongs to the field of nuclear reactor physical start-up neutron source design, specifically involving a reactor core arrangement method and a reactor pressure device. Background Technology

[0002] Currently, primary neutron sources are widely used in large nuclear power plants for initial reactor fuel loading and startup, while secondary neutron sources are used for subsequent fuel loading and startup counting after the core is activated in the first cycle. Primary neutron sources generate neutrons through spontaneous fission without requiring activation, but they are extremely expensive.

[0003] Secondary neutron sources have a price advantage, but their cladding is prone to damage during use, potentially leading to defects such as primary circuit contamination. However, eliminating the use of secondary neutron sources altogether could result in insufficient neutron flux. Summary of the Invention

[0004] This invention was made to solve the above-mentioned problems, and its purpose is to provide a reactor core arrangement method that eliminates the secondary neutron source, makes full use of the remaining source strength of the primary neutron source, and completely eliminates the use of the secondary neutron source.

[0005] This invention provides a reactor core arrangement method, characterized by the following steps:

[0006] The reactor core is loaded with fuel assemblies and corresponding primary neutron sources for the first cycle of the reactor. After the fuel assemblies are irradiated, the first spent fuel assembly is formed.

[0007] The primary neutron source is removed from the irradiated fuel assembly of the first cycle core and loaded into the first spent fuel assembly to form the second cycle core for the second cycle of the reactor. The first spent fuel assembly is irradiated to form the second spent fuel assembly.

[0008] The primary neutron source is removed from the irradiated fuel assembly of the second cycle core and loaded into the second spent fuel assembly to form the third cycle core for the third cycle of the reactor. The second spent fuel assembly is irradiated to form the third spent fuel assembly.

[0009] After the primary neutron source is removed from the third-cycle core, it is not reinserted into the core for subsequent core cycles.

[0010] In one embodiment of the present invention, the first spent fuel assembly and the second spent fuel assembly are both located at the core positions corresponding to the first three sets of fuel assemblies loaded into the reactor.

[0011] In one embodiment of the present invention, the primary neutron source is a Cf-252 neutron source.

[0012] In one embodiment of the present invention, there are three sets of primary neutron sources.

[0013] In one embodiment of the present invention, the fuel assembly includes actinides, which provide neutrons through their own decay.

[0014] In one embodiment of the present invention, the cycle length of the first cycle core, the second cycle core, and the third cycle core is not less than 2 years.

[0015] The present invention also provides a reactor pressure device for performing a second cycle of a reactor, characterized by including: a containment vessel;

[0016] A biological shielding layer is located inside the containment vessel. The biological shielding layer has at least one pre-set channel inside for embedding an external-source range neutron detector.

[0017] The second-cycle reactor core, located inside the biological shield, includes at least one set of primary neutron sources and at least one set of first spent fuel assemblies.

[0018] Core containment barrels are used to enclose the second-cycle core.

[0019] Among them, the primary neutron source is the primary neutron source used in the previous loop;

[0020] An embedded off-core range neutron detector is used to monitor the state of the second-cycle core.

[0021] In one embodiment of the present invention, the count rate of the off-pile source range neutron detector is not less than 2 cps.

[0022] In one embodiment of the present invention, the second cyclic core does not include a secondary neutron source.

[0023] In one embodiment of the present invention, the first spent fuel assembly is located in the second cycle core near the external source range neutron detector.

[0024] The role and effect of invention

[0025] According to the reactor core arrangement method and reactor pressure device of the present invention, in the second and third cycles of a large nuclear power plant reactor, the primary neutron source used in the previous cycle and the neutrons generated by the decay of actinide nuclides in the spent fuel assemblies can be combined to enable the external source range neutron detector to obtain an effective count of not less than 2 cps, thereby eliminating the need for the use of secondary neutron sources in the second and third cycle reactor cores.

[0026] Furthermore, in the fourth and subsequent cycles, as the burnup of spent fuel assemblies deepens, the neutrons emitted by the spent fuel assemblies alone can enable the external-source range neutron detector to achieve an effective count of no less than 2 cps. This eliminates the need for a secondary neutron source throughout the entire reactor lifecycle, reducing the costs of purchasing, replacing, and maintaining secondary neutron sources. It also avoids potential problems such as increased tritium emissions, increased solid waste from nuclear power plants, and contamination of the reactor's primary circuit that could result from the use of secondary neutron sources.

[0027] Furthermore, according to calculations, based on the arrangement of the present invention, there is no need to limit the burn-up depth of the irradiated components arranged near the external source range neutron detector at the start of the fuel loading, nor is it necessary to change the original component arrangement of the reactor core. It is possible to make the count rate of the external source range neutron detector meet the minimum requirement of 2 cps without increasing additional costs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the reactor pressure device in an embodiment of the present invention.

[0030] Figure 2 This is a flowchart of the reactor core arrangement method in an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures

[0032] 100-Reactor pressure device, 10-Containment vessel, 20-Bio-shielding layer, 21-External-range neutron detector, 22-Vascular, 30-Reactor core, 31-Primary neutron source, 40-Core enclosure. Detailed Implementation

[0033] The technical solutions disclosed in this invention will be described in detail below with reference to specific embodiments.

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0036] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0037] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the reactor core arrangement method and reactor pressure device 100 of the present invention.

[0038] Figure 1 This is a schematic diagram of the reactor pressure device 100 in an embodiment of the present invention.

[0039] like Figure 1 As shown, the hierarchical structure of the reactor pressure device 100 in this embodiment, from the outside to the inside, is as follows: containment 10, biological shielding layer 20, core shroud 40, and reactor core 30.

[0040] The containment vessel 10, as the outermost final safety barrier, is used to contain internal radioactive materials under extreme accident conditions, preventing their release into the environment and thus protecting the entire reactor pressure vessel 100. It is worth noting that this application does not limit the number of layers or the structure of the containment vessel 10; its design can be adaptively adjusted according to the site conditions of the nuclear power plant and the specific type, power rating, safety regulations, etc., of the reactor core 30 during operation, with the specific goal of achieving reliable containment and protection functions.

[0041] As one implementation, the containment vessel 10 may, for example but not limited to, employ a prestressed reinforced concrete structure. Specifically, its structure includes a shell body made of prestressed reinforced concrete and a sealed steel liner attached to the inner surface of the shell body. The shell body has excellent compressive and impact resistance, capable of withstanding internal high pressure and external impacts under accident conditions. The sealed steel liner ensures the overall airtightness of the containment vessel 10, and its thickness may be 6 mm to 10 mm. The material may include low-carbon steel, and a continuously sealed inner surface is formed by welding.

[0042] This application does not impose specific limitations on the shape of the containment vessel 10. The containment vessel 10 can be cylindrical dome-shaped, or other shapes that can effectively withstand internal pressure, such as spherical or ellipsoidal, depending on design requirements. Necessary equipment penetrations may also be provided on the main body of the containment vessel 10. This application does not impose specific limitations on the number or specific form of such auxiliary structures; their design is based on ensuring safety during normal operation and under accident conditions. In this application, for the sake of simplicity and clarity in the drawings, the accompanying drawings only show a schematic outline of the main body of the containment vessel 10.

[0043] like Figure 1 As shown, the biological shielding layer 20 is located inside the containment vessel 10, and the reactor core 30 is located inside the biological shielding layer 20. The biological shielding layer 20 has three pre-set channels 22, which are used to embed three external-source range neutron detectors 21. The core function of the biological shielding layer 20 is to shield radioactive materials leaking from the reactor core 30, reducing the radiation dose to a safe level to protect external personnel, equipment, and the environment. It also provides a precise installation and measurement environment for the embedded external-source range neutron detectors 21. These radioactive materials include, but are not limited to, neutrons and gamma rays. The biological shielding layer 20, the external-source range neutron detectors 21, and the reactor core 30 together constitute a functional unit. The pre-set channels 22 pass through the biological shielding layer 20 and point towards the internal reactor core 30, thereby enabling monitoring of the neutron state of the reactor core 30 during fuel loading and startup.

[0044] This application does not limit the specific structure of the biological shielding layer 20. In one embodiment, a multi-layer composite structure can be adopted, for example, using boron-containing material to absorb neutrons on the inner side and high-density concrete to shield gamma rays on the outer side. The gap between the diameter of the pre-set channel 22 inside the biological shielding layer 20 and the outer diameter of the external source range neutron detector 21 is controlled at 0.5~1mm. The above are only examples of some embodiments of the biological shielding layer 20. This invention does not limit its material formulation, specific thickness, channel design and internal structure. Different design parameters can be adopted according to the actual spatial layout and maintenance requirements of the reactor pressure device 100.

[0045] The neutron detection process is extremely sensitive to geometric position. Even a small deviation in position can lead to a significant change in the count rate. Therefore, the off-pile range neutron detector 21 needs to have a reliable circumferential support structure.

[0046] A smaller gap ensures that the external-source range neutron detector 21 can accurately return to its designed position and orientation after each maintenance and installation during use, ensuring the consistency and comparability of monitoring data. It also prevents shaking or displacement due to long-term operation or unexpected events such as earthquakes, avoiding data deviation caused by positional changes. However, since the external-source range neutron detector 21 may experience thermal expansion during use, in one embodiment, a gap of 0.5~1mm is selected to achieve better balance and ensure smooth maintenance or replacement during use.

[0047] This invention does not impose a single limitation on the specific structure and performance parameters of the external-source range neutron detector 21. As an example, in one embodiment, the external-source range neutron detector 21 includes a sealed metal casing filled with working gas. Electrodes are disposed inside the sealed metal casing as collecting electrodes. The geometry of the sealed metal casing can be cylindrical, spherical, or other shapes, and its specific dimensions can be designed according to detection efficiency and space constraints. The performance parameters of the external-source range neutron detector 21, such as energy response range, detection efficiency, background count rate, and operating voltage, are based on meeting the signal-to-noise ratio requirement of a minimum count rate of 2 cps, and can also be adjusted according to monitoring requirements.

[0048] In this invention, the effective counting of the external-source range neutron detector 21 is achieved by optimizing the neutron source configuration inside the reactor core 30. Specifically, based on the reuse of the primary neutron source 31, and combined with the use of spent fuel assemblies generated in the previous cycle, it is ensured that a sufficient number of neutrons always reach the external-source range neutron detector 21 during the fuel loading and startup processes of each cycle, so that its count rate always meets safety requirements.

[0049] The monitoring principle of the external-source range neutron detector 21 is as follows: When the reactor core 30 is in a subcritical state, neutrons produced by the primary neutron source 31 and actinide nuclides in the spent fuel assemblies within the reactor core 30, after penetrating the biological shielding layer 20, can be captured by the gas inside the external-source range neutron detector 21, such as He-3 or BF3, and trigger a nuclear reaction, generating an electrical pulse signal. The external-source range neutron detector 21 obtains the count rate (cps) by counting the number of pulses per second. This count rate is strongly positively correlated with the effective neutron source within the reactor core 30, thereby enabling the monitoring of the reactor core 30.

[0050] In this embodiment, the count rate of the external source range neutron detector 21 is considered valid when it is not less than 2 cps.

[0051] In this embodiment, the simulation calculation of the reactor core 30 and the performance test results of the external source range neutron detector 21 are combined. The influence of factors such as neutron attenuation in the biological shielding layer 20 and neutron scattering in the pore 22 is also considered to ensure that the net count rate of the external source range neutron detector 21 can still meet the safety monitoring requirements under any conditions, and sufficient safety margin is reserved. The count rate threshold of the external source range neutron detector 21 is determined to be no less than 2 cps.

[0052] The core shroud 40 directly encloses the reactor core 30. This invention does not impose a single limitation on the specific material and thickness of the core shroud 40. As one embodiment, a zirconium alloy can be used. For example, a Zr-4 alloy with a thickness of 0.8~1.2 mm can be used, which has good neutron permeability, corrosion resistance, and mechanical strength, effectively preventing the leakage of fission products. The internal and external surface treatments of the core shroud 40 can be adjusted according to actual requirements. In one embodiment, a graphite or ceramic-based coating can be applied to the inner wall of the core shroud 40 to reduce the interaction between the reactor core 30 and the core shroud 40.

[0053] In this invention, during the first cycle, the reactor core 30 is loaded with fuel assemblies and a primary neutron source 31. The neutrons generated by the spontaneous fission of the primary neutron source 31 are used to effectively monitor the fuel loading and startup process of the reactor core 30 through an external source range neutron detector 21.

[0054] After the first cycle, the reactor core 30 uses the remaining source strength of the primary neutron source 31 and the neutrons provided by the decay of actinide nuclides in the fuel assemblies to enable the external source range neutron detector 21 to obtain an effective count, thus ensuring the effective monitoring of the core subcriticality throughout the entire fuel loading process.

[0055] In subsequent cycles, although the source strength of the primary neutron source 31 continues to decrease due to decay, the neutron source strength gradually increases as the burn-up depth of the in-reactor components gradually increases, and overall it can meet the count rate requirements of the off-reactor range neutron detector 21.

[0056] The reactor core 30 is selected from the first cycle core, the second cycle core, the third cycle core, and the subsequent cycle refueling core in different cycles.

[0057] Figure 2 This is a flowchart of the reactor core arrangement method in an embodiment of the present invention.

[0058] like Figure 2 As shown, when the reactor pressure device 100 is used for the first cycle of the reactor, the reactor core 30 is the first cycle core.

[0059] At this time, the first cycle core follows Figure 2 The arrangement is carried out in step S1: fuel assemblies and corresponding primary neutron sources 31 are loaded into the reactor core during the first cycle of the reactor, and the first cycle of the core is carried out. After the fuel assemblies are irradiated, the first spent fuel assembly is formed.

[0060] The fuel assembly includes actinides, which provide neutrons through their own decay.

[0061] When the reactor pressure device 100 is used for the second cycle of the reactor, the reactor core 30 is the second cycle core.

[0062] At this time, the second cycle core follows Figure 2 The arrangement is carried out in step S2: the primary neutron source 31 is removed from the irradiated fuel assembly of the first cycle core and installed into the first spent fuel assembly at that location to form the second cycle core, and the second cycle of the reactor is carried out. The first spent fuel assembly is irradiated to form the second spent fuel assembly.

[0063] In one embodiment, the first spent fuel assembly is positioned at the core location corresponding to the first three sets of fuel assemblies, close to the position of the external source range neutron detector 21.

[0064] Specifically, during the refueling process of replacing the reactor core 30 with the core of the second cycle at the end of the first cycle, this embodiment does not restrict the selection of the fuel assembly burn-out depth at different core positions during refueling. It can be that the first spent fuel assembly with higher burn-out is loaded into the core position corresponding to the first three sets of fuel assemblies to be loaded into the reactor core, or it can be randomly loaded into the reactor core. According to calculations, using the arrangement method of the present invention, different loading methods can achieve the effect of making the external source range neutron detector 21 obtain the lowest count.

[0065] This approach not only enables the reuse of the original primary neutron source 31, but also optimizes the neutron flux distribution by selecting its specific placement position in the reactor core 30, thereby improving the stability and reliability of the response of the external source range neutron detector 21 during the startup phase and further enhancing the safety of reactor startup.

[0066] When the reactor pressure device 100 is used for the third cycle of the reactor, the reactor core 30 is the third cycle core.

[0067] At this time, the third cycle core follows Figure 2 The arrangement is carried out in step S3: the primary neutron source 31 is removed from the irradiated fuel assembly of the second cycle core and installed into the second spent fuel assembly to form the third cycle core, and the third cycle of the reactor is carried out. The second spent fuel assembly is irradiated to form the third spent fuel assembly.

[0068] In one embodiment, the second spent fuel assembly is positioned at the core location corresponding to the first three sets of fuel assemblies, close to the position of the external source range neutron detector 21.

[0069] When the reactor pressure device 100 is used for the fourth and subsequent cycles of the reactor, the reactor core 30 is the refueling core for the subsequent cycles.

[0070] At this point, subsequent refueling of the core proceeds according to... Figure 2 The arrangement is carried out in step S4: after the primary neutron source 31 is removed from the third cycle core, it is not put back into the core, and the core is cycled in the next step.

[0071] In one implementation, such as Figure 1 As shown, the primary neutron source 31 consists of three sets of Cf-252 neutron sources, with each cycle lasting 2 years.

[0072] During the initial cycle, the source strength of the Cf-252 neutron source in the initial cycle core during reactor startup was 4.50 × 10⁻⁶. 8 ~5.50×10 8 n / s.

[0073] At the start of the second cycle, the residual source strength of the Cf-252 neutron source was 2.76 × 10⁻⁶. 8 ~3.35×10 8 n / s. The burnup depth of the first spent fuel assembly is 10000~12800 MWd / tU, corresponding to a neutron source intensity of 4.0×10⁻⁶. 6 ~7.5×10 6 n / s.

[0074] Calculations and evaluations indicate that during the second cycle, inserting Cf-252 neutron sources previously used in the first cycle core into the first three fuel assemblies, while also considering neutrons generated by the decay of actinide nuclides in the first spent fuel assembly, will result in a count rate of approximately 6.5–6.9 cps for the external-source range neutron detector 21 after reactor insertion. At this point, the neutron contribution from the first spent fuel assembly will be 1.8–2.2%. The count rate of the external-source range neutron detector 21 meets the minimum requirement of 2 cps. In subsequent cycles, the count rate will gradually increase as the number of spent fuel assemblies increases.

[0075] At the start of the third cycle, the residual source strength of the Cf-252 neutron source was 1.65 × 10⁻⁶. 8 ~1.85×10 8 The burnup depth of the second spent fuel assembly is 25000~32800 MWd / tU, corresponding to a neutron source intensity of 1.2×10⁻⁶ m / s. 8 ~2.5×10 8 n / s.

[0076] Calculations and evaluations indicate that during the third cycle, inserting Cf-252 neutron sources previously used in the second cycle core into the first three fuel assemblies, while also considering neutrons generated by the decay of actinide nuclides in the second spent fuel assembly, will result in a count rate of approximately 7.2–8.8 cps for the external-source range neutron detector 21 after insertion. At this point, the neutron contribution from the second spent fuel assembly will be 43.4–50.0%. The count rate of the external-source range neutron detector 21 meets the minimum requirement of 2 cps. In subsequent cycles, the count rate will gradually increase as the number of spent fuel assemblies increases.

[0077] At the start of the fourth cycle, the burnup depth of the third spent fuel assembly was 35,000–48,200 MWd / tU, corresponding to a neutron source intensity of 2.5 × 10⁻⁶. 8 ~4.5×10 8 n / s.

[0078] Calculations and evaluations show that, during the fourth cycle, without considering the use of the Cf-252 neutron source, relying solely on the neutrons generated by the decay of actinide nuclides in the third spent fuel assembly, the count rate of the external source range neutron detector 21 after reactor loading is 5.5~5.9 cps, which meets the minimum requirement of 2 cps. As the number of spent fuel assemblies increases during subsequent fuel loading, the count rate will gradually increase.

[0079] The theoretical basis for eliminating the secondary neutron source is that the neutrons generated by the decay of actinide nuclides in the spent fuel assembly after a certain burn-out are effectively counted by the external source range neutron detector 21, and the deeper the fuel assembly burns out, the stronger the neutron source.

[0080] Based on the above results, it can be determined that subsequent cycles can meet the count rate requirements by relying solely on the neutron contribution from the spent fuel assembly without using the Cf-252 neutron source. The method of this invention can achieve the goal of eliminating the reactor secondary neutron source.

[0081] According to the arrangement of the present invention, without changing the burning depth of other fuel components, by simply reusing the primary neutron source 31 and utilizing spent fuel components, it is possible to ensure sufficient neutron source strength in the initial stage of fuel loading from the second cycle onwards, thus achieving seamless connection of safety monitoring.

[0082] This method has a "self-growing" characteristic: as the power plant operates, the burnup of spent fuel deepens and its contribution increases, and it can naturally transition to a state in which no external neutron source is needed in the later stages. The scheme has internal logical consistency and high safety redundancy.

[0083] Subsequent cycles of canceling the loading and startup of the secondary neutron source can achieve benefits such as reducing tritium emissions, avoiding the risk of secondary neutron source rupture, reducing solid waste generation, and lowering component procurement costs.

[0084] The elimination of the secondary neutron source directly saved on its procurement and maintenance costs. Meanwhile, the reuse of the primary neutron source 31 significantly improved the utilization rate of the Cf-252 neutron source, allowing it to be reused across multiple cycles instead of just in the first cycle, thus amortizing the cost per cycle. This significantly reduced the economic cost of the nuclear reaction process without requiring changes to other hardware.

[0085] Damage to the cladding of the secondary neutron source could lead to contamination of the primary circuit with radioactive antimony Sb-122 and Sb-124, increasing the radiation dose to overhaul personnel. Furthermore, if the cladding is damaged, stainless steel fragments could enter the primary circuit, abrading the core shroud and causing damage to other neutron source components. The decommissioning of the secondary neutron source fundamentally avoids these risks and completely eliminates potential serious accident hazards.

[0086] Since the Sb-Be pellets in the secondary neutron source are activated by neutrons in reactor core 30 to produce tritium, which is the main source of tritium in the primary loop, eliminating the secondary neutron source can reduce primary loop tritium emissions by about 25%, significantly reducing environmental emissions and radiation dose to personnel.

[0087] The secondary neutron source has a short half-life, typically only 58 to 62 days. During subsequent cycles, if the reactor shutdown time is too long due to refueling or equipment maintenance, the secondary neutron source will decay and reduce its source strength, which may result in the external source range neutron detector 21 being unable to obtain an effective count. This time window will bring significant technical management pressure to reactor shutdown for refueling and maintenance. The elimination of the secondary neutron source avoids the operational pressure caused by this factor and greatly simplifies the fuel management and source term management process.

[0088] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0089] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for arranging a reactor core, characterized in that, Includes the following steps: In the first cycle of the reactor core, fuel assemblies and corresponding primary neutron sources are loaded and the first core cycle is performed. After the fuel assemblies are irradiated, they form the first spent fuel assembly. The primary neutron source is removed from the first cycle core and installed into the first spent fuel assembly to form the second cycle core, and the second cycle of the reactor is carried out. The first spent fuel assembly is irradiated to form the second spent fuel assembly. The primary neutron source is removed from the second cycle core and installed into the second spent fuel assembly to form the third cycle core, and the third cycle of the reactor is carried out. The second spent fuel assembly is irradiated to form the third spent fuel assembly. After the primary neutron source is removed from the third-cycle core, it is not reinserted into the core for subsequent core cycles. The first spent fuel assembly and the second spent fuel assembly are both located in the core positions corresponding to the fuel assemblies of the first three groups that were loaded into the reactor.

2. The reactor core arrangement method according to claim 1, characterized in that: The primary neutron source is the Cf-252 neutron source.

3. The reactor core arrangement method according to claim 1, characterized in that: The primary neutron sources consist of three groups.

4. The reactor core arrangement method according to claim 1, characterized in that: The fuel assembly includes actinides, which provide neutrons through their own decay.

5. The reactor core arrangement method according to claim 1, characterized in that: The cycle length of the first cycle core, the second cycle core, and the third cycle core is no less than 2 years.

6. A reactor pressure device for implementing the reactor core arrangement method as described in any one of claims 1 to 5, characterized in that, include: Containment vessel; A biological shielding layer is disposed inside the containment vessel. The biological shielding layer has at least one pre-set channel inside, which is used to embed an external source range neutron detector. The second cycle core, located inside the biological shielding layer, includes at least one set of primary neutron sources and at least one set of first spent fuel assemblies; Core containment barrel, used to enclose the second cycle core. The primary neutron source is the same primary neutron source used in the previous cycle; The external source range neutron detector is used to monitor the state of the second cycle reactor core.

7. The reactor pressure device according to claim 6, characterized in that: The count rate of the off-pile source range neutron detector is not less than 2 cps.

8. The reactor pressure device according to claim 6, characterized in that: The second-cycle core does not include a secondary neutron source.

9. The reactor pressure device according to claim 6, characterized in that: The first spent fuel assembly is located in the second cycle core near the external source range neutron detector.

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