A neutron source device for a long-life nuclear reactor and a method of using the same

Abstract

The present invention discloses a long-life neutron source device for a nuclear reactor and a method for using the device, wherein the device comprises a neutron source assembly capable of sealingly installing a long-life neutron source, wherein the neutron source assembly is connected to a reactor control rod drive mechanism, and the neutron source assembly is inserted into or withdrawn from a reactor core through the reactor control rod drive mechanism; the long-life neutron source can be an americium beryllium source or a plutonium beryllium source. The present invention can significantly reduce the consumption of neutron source materials during reactor operation, maintain the long-life characteristics of the neutron source materials, and thus can be reused by one or more units, thereby avoiding the engineering cost and engineering progress uncertainty of a one-time neutron source material procurement faced by each newly built nuclear power plant unit in China.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear reactor fuel, and particularly relates to the technical field of reactor neutron sources. Background Art

[0002] There are two starting methods for the pressurized water reactor nuclear power plants in operation and under construction in China, with and without external neutron sources. Except for the pressurized water reactor designed by Russia, which is designed for starting without external neutron sources, all other pressurized water reactor nuclear power plants designed in China, the United States or France are designed for starting with external neutron sources.

[0003] For the design of reactors with external neutron sources, the role of the neutron source is to provide a basic neutron counting level during the process of loading the reactor to criticality, so as to ensure that the source range detector can operate normally and respond to the core proliferation neutrons, overcome the blind spot of the source range detector, and ensure that the reactor has sufficient neutron counting rate in the subcritical state to carry out criticality safety supervision and ensure the safe start-up of the reactor. Among them, the primary neutron source (also called the primary neutron source) uses materials that can emit neutrons and is used for the first startup of the nuclear power plant. After the first cycle of use, it is unloaded from the core and no longer used; the secondary neutron source (also called the secondary neutron source) generally uses antimony-beryllium (Sb-Be) source, which does not emit neutrons when not irradiated, is put into the pile during the first cycle of loading, and is used for the second and subsequent cycles after irradiation and activation in the pile.

[0004] The primary neutron source currently used in nuclear power plants is a nuclide that can spontaneously fission and emit neutrons, and most of them use californium sources, which use the nuclides that can spontaneously fission and emit neutrons. 252 In recent years, several disadvantages of using this neutron source have become apparent:

[0005] 1) 252 The half-life of Cf is about 2.635 years, and it can generally only be used for the startup of one unit;

[0006] 2) 252 Cf production depends on ultra-high flux reactors, and China does not have the production conditions;

[0007] 3) 252 Cf International procurement costs continue to increase, leading to higher construction costs for nuclear power plants;

[0008] 4) Affected by the international situation and Russia 252 Cf capacity contraction, difficult to guarantee 252 The adequacy and progress of Cf neutron source supply bring uncertainty to the progress of nuclear power plant construction.

[0009] At present, most of my country's nuclear power plants adopt a reactor design with an external neutron source. It is expected that for a long period of time, the domestic mainstream pressurized water reactor models such as CAP1400, CAP1000, Hualong One and CPR1000 will still face the common problem of primary neutron source supply, which is also one of the "bottleneck" problems in my country's independent nuclear power technology construction and export.

[0010] In order to solve the problem of primary neutron source supply, the present invention proposes a method of using neutron source materials with a long half-life to make long-life neutron sources, which can be reused in multiple nuclear power plant units. After adopting this technology, domestic newly built nuclear power units will no longer rely on purchasing from abroad for a long time. 252 Cf, to achieve the goal of reducing project cost and ensuring project progress. Summary of the invention

[0011] The purpose of the present invention is to provide a long-life neutron source device that can be reused in a nuclear power plant and a method of use, which can eliminate the long-term dependence on foreign supply of neutron source materials, reduce the cost of nuclear power construction projects, and ensure the progress of project construction.

[0012] To achieve the above-mentioned object, the present invention provides a long-lived neutron source device for a nuclear reactor, the device comprising a neutron source assembly capable of sealingly installing a long-lived neutron source, the neutron source assembly being connected to a reactor control rod drive mechanism, the neutron source assembly being inserted into or withdrawn from a reactor core through the reactor control rod drive mechanism; the long-lived neutron source can be selected from an americium beryllium source or a plutonium beryllium source.

[0013] Preferably, the long-lived neutron sources are respectively 241 Am and 238 The bombardment of alpha particles produced by the alpha decay of Pu 9 Be emits neutrons.

[0014] The present invention also provides a method for using a long-life neutron source device for a nuclear reactor, wherein the long-life neutron source is sealed and packaged in the neutron source assembly, and the neutron source assembly is connected to the reactor control rod drive mechanism;

[0015] When starting the reactor: the neutron source assembly is inserted into the reactor core through the reactor control rod drive mechanism, and after the count rate detected by the off-core detector is normal, the reactor control rod drive mechanism lifts the neutron source assembly out of the reactor core.

[0016] Preferably, after the neutron source assembly is unloaded from the reactor core, it can be used for starting up a reactor in a subsequent cycle of the same unit, or starting up a reactor in another unit.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. Through the use of the present invention, the consumption of neutron source materials during reactor operation can be significantly reduced, and the long life characteristics of the neutron source materials can be maintained, so that one or more units can be reused, thereby avoiding the engineering cost and engineering progress uncertainty of the one-time procurement of neutron source materials faced by each newly built nuclear power plant unit in the country.

[0019] 2. The use of the present invention is easy to implement in existing reactor designs, such as using a control rod drive mechanism to insert and withdraw a neutron source, with little requirement for changing the original design.

[0020] 3. With the commonly used 252 Compared with Cf, the neutron source materials used in the present invention are generally easier to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Insert core schematic for neutron source assembly;

[0022] Figure 2 A core schematic is proposed for the neutron source assembly. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The present invention provides a method for reusing a long-life neutron source in a nuclear power plant, comprising a long-life neutron source, a neutron source assembly connected to a reactor control rod driving mechanism, and an operation mode of the neutron source in a reactor of the nuclear power plant.

[0025] As a preferred embodiment of the present invention, the neutron emitting material of the long-lived neutron source can be selected from an americium beryllium source or a plutonium beryllium source, respectively. 241 Am and 238 The bombardment of alpha particles produced by the alpha decay of Pu 9 Be emits neutrons. In the absence of external irradiation, 241 Am and 238 Both types of Pu nuclides disappear mainly through α decay, with half-lives of 433 years and 86 years respectively, which can meet the neutron source intensity requirements for reactor startup within decades.

[0026] Under the reactor operating environment, the neutron-emitting materials of the long-lived neutron source may be consumed due to the high neutron flux rate environment. In order to avoid this situation, the neutron source assembly is moved out of the core fuel active area after the reactor is started and before the power is increased, thereby significantly reducing its consumption level.

[0027] After the reactor is shut down, the long-lived neutron source can continue to be used as the neutron source for subsequent startup of the same unit, or it can be transferred to other units as a startup neutron source, thus achieving reuse.

[0028] The preferred neutron emitting material of the present invention is much easier to produce by high flux irradiation than 252 Cf is also widely used in domestic and foreign industries, and due to its long half-life, it has a certain reserve in domestic and foreign nuclear industrial systems. Therefore, it is conducive to its application in nuclear power plants in terms of preparation cost and progress requirements.

[0029] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and variations. The above embodiments or implementations are merely illustrative of the present invention, and the present invention may also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described implementations should be considered illustrative rather than restrictive in any respect. The scope of the present invention should be described by the appended claims, and any changes equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A method for using a long-life neutron source device for a nuclear reactor, characterized in that: The long-life neutron source is sealed and packaged in a neutron source assembly, and the neutron source assembly is connected to the reactor control rod drive mechanism; When starting the reactor: the neutron source assembly is inserted into the reactor core through the reactor control rod drive mechanism, and after the reactor is started and before the power is increased, the reactor control rod drive mechanism takes the neutron source assembly out of the reactor core; The invention is applied to a long-life neutron source device for a nuclear reactor, the device comprising a neutron source assembly capable of sealingly installing the long-life neutron source, the neutron source assembly being connected to a reactor control rod drive mechanism, the neutron source assembly being inserted into or taken out of a reactor core through the reactor control rod drive mechanism; the long-life neutron source comprising an americium beryllium source or a plutonium beryllium source; The long-lived neutron source emits neutrons by bombarding 9Be with α particles generated by α decay of 241Am and 238Pu; Without external irradiation, the two nuclides 241Am and 238Pu disappear through α decay, with half-lives of 433 and 86 years respectively; The difficulty of producing the americium beryllium source or the plutonium beryllium source through high-flux irradiation is much lower than that of 252Cf.

2. The method for using a long-life neutron source device for a nuclear reactor as claimed in claim 1, characterized in that: After being unloaded from the reactor core, the neutron source assembly can be used for starting a subsequent cycle of the same unit, or starting a reactor of another unit.

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