JP2005207814A - Nuclear fuel assembly for reactor - Google Patents

Nuclear fuel assembly for reactor Download PDF

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JP2005207814A
JP2005207814A JP2004013161A JP2004013161A JP2005207814A JP 2005207814 A JP2005207814 A JP 2005207814A JP 2004013161 A JP2004013161 A JP 2004013161A JP 2004013161 A JP2004013161 A JP 2004013161A JP 2005207814 A JP2005207814 A JP 2005207814A
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Toshihisa Shirakawa
白川利久
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a nuclear fuel assembly for a reactor which is highly economical and can enhance the safety by being less likely to become critical promptly. <P>SOLUTION: The nuclear fuel assembly containing nuclear fuel substances consists of nuclear fuel rods (131) including a quasi-external neutron source loaded with neptunium trifluoride (NpF<SB>3</SB>) or a compound (NpBe13) of neptunium and beryllium in the center of nuclear fuel pellets (44). Consequently,<SP>238</SP>Pu, transformed through the absorption of neutrons by Np emits α rays. F generates neutrons when it reacts with the α rays. A subcritical reactor with a strong external neutron source can make the output equivalent to those of the current reactors generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、原子炉に装荷せる核燃料集合体に関する。 The present invention relates to a nuclear fuel assembly that can be loaded into a nuclear reactor.

図１は沸騰水型原子炉における核燃料物質を内包する従来の核燃料集合体（３０）の概略斜視図である（特許文献1）。核燃料集合体（３０）は、多数本正方格子状に配列された核燃料物質を内封している円柱形状の核燃料棒（３１）と、それ等の上端及び下端を夫々支持する上側結合板（３２）及び下側結合板（３３）と、前記核燃料棒（３１）の高さ途中に位置して核燃料棒（３１）間の間隔を規制する数個のスペーサ（３４）と、これ等を４面で覆うチャンネルボックス（３５）とから構成される。
図２は従来の核燃料棒（３１）の概観図である。ジルカロイ製の被覆管（４１）と、この被覆管（４１）の上下開口端を気密閉塞する上部端栓（４２）及び下部端栓（４３）と、被覆管（４１）内に装填される多数個の核燃料ペレット（４４）と、スプリング（４５）とから構成されている。
現在稼動中の沸騰水型原子炉は、高価な濃縮ウランや再処理費用が高いプルトニウムの節約のために、冷却水速度を速くしたり、核燃料棒（３１）の間の主冷却材通路（３６）を広げて水領域を広げたり、漏洩水流路（２０）領域を広げたりして飽和蒸気の割合をできるだけ減らして、中性子速度の遅い中性子を利用している。
図３は従来の核燃料集合体（３０）と従来の制御棒（２２）とからなる炉心平面の部分図である。炉心の下から核燃料集合体（３０）に入ってきた水は、核燃料棒（３１）の間の主冷却材通路（３６）を通り上に流れる間に核燃料棒（３１）から熱を吸収して飽和蒸気になり、飽和蒸気と液体の水とが混在した二相流となって流れている。チャンネルボックス（３５）の間の漏洩水流路（２０）には漏洩冷却水が流れている。制御棒（２２）はチャンネルボックス（３５）の間の漏洩水流路（２０）の中を上下に動ける。制御棒（２２）は原子炉出力を制御するための中性子を吸収する性質の強い物質である炭化硼素の粉末が充填された多数本の管をステンレスで補強した構造になっている。制御棒（２２）は制御棒駆動機構によって上下に動く。
図４は制御棒（２２）が引き抜かれた運転状態における、従来の核燃料集合体（３０）からなる炉心平面の部分図である。大半の制御棒（２２）は原子炉の下に引き抜かれている。制御棒（２２）の抜けたあとは漏洩水流路（２０）の水だけとなる。
：昭61-37591、「核燃料集合体」。 FIG. 1 is a schematic perspective view of a conventional nuclear fuel assembly (30) containing nuclear fuel material in a boiling water reactor (Patent Document 1). The nuclear fuel assembly (30) includes a cylindrical nuclear fuel rod (31) enclosing a nuclear fuel material arranged in a square lattice, and an upper coupling plate (32) for supporting the upper end and the lower end thereof. ) And the lower coupling plate (33), several spacers (34) which are located in the middle of the height of the nuclear fuel rod (31) and regulate the interval between the nuclear fuel rods (31), and these are arranged on four surfaces And a channel box (35) covered with.
FIG. 2 is a schematic view of a conventional nuclear fuel rod (31). Zircaloy-coated tube (41), upper end plug (42) and lower end plug (43) for hermetically closing the upper and lower opening ends of the coated tube (41), and a large number of tubes loaded in the coated tube (41) It consists of a single nuclear fuel pellet (44) and a spring (45).
Boiling water reactors currently in operation have increased cooling water speeds and main coolant passages (36) between nuclear fuel rods (31) in order to save expensive enriched uranium and plutonium with high reprocessing costs. ) Is widened to widen the water region, or the leaked water flow channel (20) region is widened to reduce the ratio of saturated vapor as much as possible, and neutrons having a slow neutron velocity are used.
FIG. 3 is a partial view of a core plane composed of a conventional nuclear fuel assembly (30) and a conventional control rod (22). Water entering the nuclear fuel assembly (30) from below the core absorbs heat from the nuclear fuel rod (31) while flowing upward through the main coolant passage (36) between the nuclear fuel rods (31). It becomes saturated steam and flows as a two-phase flow in which saturated steam and liquid water are mixed. Leaked cooling water flows in the leaked water flow path (20) between the channel boxes (35). The control rod (22) can move up and down in the leakage water flow path (20) between the channel boxes (35). The control rod (22) has a structure in which a large number of tubes filled with boron carbide powder, which has a strong neutron absorbing property for controlling the reactor power, are reinforced with stainless steel. The control rod (22) is moved up and down by a control rod drive mechanism.
FIG. 4 is a partial plan view of a core plane composed of a conventional nuclear fuel assembly (30) in an operating state in which the control rod (22) is pulled out. Most of the control rods (22) are drawn under the reactor. After the control rod (22) comes out, only the water in the leakage water channel (20) is obtained.
: Sho 61-37591, “Nuclear Fuel Assembly”.

原子力発電所が多くなり、より一層の安全性が求められている。沸騰水型原子炉では冷却材喪失事故（LOCA）時にも炉心下部に大量の水を擁している為蒸発した蒸気による長時間の炉心冷却が期待できるのは元より、最近の沸騰水型原子炉はインターナルポンプの採用や緊急時炉心冷却システム（ECCS）の改良強化により冷却材喪失事故（LOCA）が生じ難くなっている。制御棒（２２）の駆動方式に関しては電動式により上下に微小な動きにより実効増倍係数（keff）の微調整が可能となり、出力が緩やかに調節できるため核燃料棒の健全性が高まっている。
したがって、急激な反応度事故への対策が十分に図れれば安全性が格段に増す。特に、急激な出力上昇により爆発的な原子炉崩壊の恐れを少なくするために原子炉の炉心を即発臨界になり難くすればよい。 The number of nuclear power plants is increasing, and further safety is required. Boiling water reactors have a large amount of water in the lower part of the core even during a loss of coolant accident (LOCA), so long-term core cooling with vaporized steam can be expected, as well as recent boiling water reactors. Has become less likely to cause a loss of coolant accident (LOCA) due to the adoption of an internal pump and improved and strengthened emergency core cooling system (ECCS). Regarding the drive system of the control rod (22), the effective multiplication factor (keff) can be finely adjusted by a small movement up and down by an electric method, and the output can be adjusted gently, so that the soundness of the nuclear fuel rod is increased.
Therefore, safety can be greatly increased if sufficient countermeasures are taken for sudden reactivity accidents. In particular, in order to reduce the risk of explosive reactor collapse due to a rapid increase in power, it is only necessary to make the core of the reactor difficult to be promptly critical.

図５は本発明の准外部中性子源入り核燃料棒（１３１）の概観図である。核燃料棒に内蔵せる核燃料ペレット（４４）の中心にネプツニウム（Np）とフッ素（F）の化合物である三フッ化ネプツニウム(NｐF３)（１４４）を装荷した。
図６は准外部中性子源入り核燃料棒（１３１）からなる本発明の准外部中性子源入り核燃料集合体（１３０）と従来の制御棒（２２）とからなる炉心平面の部分図である。
なお、NpF3の融点は絶対温度で約１６００Kであるが、自分自身の核分裂作用は弱いため高温になりにくい。図５では核燃料ペレット（４４）の中心にNｐF３を装荷したが、核燃料ペレット（４４）の外周部に装荷した場合には沸騰水型原子炉の冷却水温度は５６０Kであるから全く問題にならない。 FIG. 5 is a schematic view of a nuclear fuel rod (131) with an quasi-external neutron source of the present invention. Neptunium trifluoride (NpF 3 ) (144), which is a compound of neptunium (Np) and fluorine (F), was loaded at the center of the nuclear fuel pellet (44) to be incorporated in the nuclear fuel rod.
FIG. 6 is a partial plan view of a core plane composed of a nuclear fuel assembly (130) containing an quasi-external neutron source according to the present invention comprising a nuclear fuel rod (131) containing an quasi-external neutron source and a conventional control rod (22).
The melting point of NpF 3 is about 1600K in absolute temperature, but its own fission action is weak, so it is difficult to reach high temperature. In FIG. 5, NpF 3 is loaded at the center of the nuclear fuel pellet (44). However, when loaded on the outer periphery of the nuclear fuel pellet (44), there is no problem because the cooling water temperature of the boiling water reactor is 560K. .

一般に、原子炉は臨界状態で運転される。しかし、臨界未満の炉心でも発生する中性子の総数は外部中性子源からの中性子に比例して多くなるため、本発明の准外部中性子源入り核燃料集合体（１３０）からなる炉心では臨界未満であっても大きな出力を得ることができる。
強力な外部中性子源の補助の元ではｋeffが１．０よりも小さい臨界未満でも所用の出力を得ることができるため、装荷せる核分裂性物質も少なくてすみ経済性も高い。核分裂性物質が少ないと転換比も向上し運転期間を延長することもできる。更に、反応を制御する制御棒の能力が低くても済むため安全性と経済性が高い。
通常時出力運転でも臨界未満であるため、反応度変動を小さくすれば即発臨界になりにくくなり、爆発的事故を起こし難い。したがって、環境への放射能放出が極めて少なく、原子炉の基数が増えても環境を汚染する割合が十分小さい。
燃焼末期の燃料では、核分裂生成物やプルトニウムからの崩壊熱が約２０％あるから核分裂による発熱は所要の８０％程度でよいが、その上本発明では外部中性子源による中性子の補填を受けるため出力ミスマッチは非常に小さなものとなり核燃料棒に対する安全余裕が増加する。燃焼期間も長くなるため経済性がます。
本発明の准外部中性子源入り核燃料集合体（１３１）は、成型加工時には中性子の発生が殆どないため従来と同等の中性子遮蔽および臨界管理を実施すればよい。 Generally, a nuclear reactor is operated in a critical state. However, since the total number of neutrons generated in the subcritical core increases in proportion to the neutrons from the external neutron source, the core consisting of the nuclear fuel assembly (130) containing the quasi-external neutron source of the present invention is subcritical. Can also obtain a large output.
With the aid of a powerful external neutron source, the required output can be obtained even when the keff is less than 1.0, which is less than the critical value, so that less fissile material can be loaded and the economy is high. If the amount of fissile material is small, the conversion ratio can be improved and the operation period can be extended. Furthermore, since the ability of the control rod for controlling the reaction is low, safety and economy are high.
Even under normal power operation, the criticality is less than critical. Therefore, if the change in reactivity is reduced, it becomes difficult to become prompt criticality and hardly cause an explosive accident. Therefore, radioactive release to the environment is extremely small, and even if the number of reactors increases, the rate of polluting the environment is sufficiently small.
In the end-of-combustion fuel, the decay heat from the fission products and plutonium is about 20%, so the heat generated by the fission may be about 80% as required. The mismatch becomes very small and the safety margin for the nuclear fuel rod increases. Economical because of longer combustion period.
Since the nuclear fuel assembly (131) containing the quasi-external neutron source of the present invention generates almost no neutrons during the molding process, neutron shielding and criticality management equivalent to those of the prior art may be performed.

急激な出力上昇により爆発的な原子炉崩壊の恐れを少なくするために原子炉の炉心を即発臨界になり難くい炉心を提供した。   In order to reduce the risk of explosive reactor collapse due to a sudden increase in power, a reactor core that is unlikely to be promptly critical was provided.

NｐF３は中性子もアルファ線（α線）も放出しないが運転が続くにつれてNｐF３のネプツニウム（Np）が中性子を吸収してプルトニウム２３８（238Pu）に変換されていく。238Puはα線を多量に放出する。NｐF３のフッ素（F）はα線と反応すると中性子を放出する。NｐF３は燃焼により外部中性子源になるため准外部中性子源と呼ぶことにした。
原子炉を出力運転し続けるためには原則として原子炉は臨界でなければならない。しかし、外部中性子源があれば原子炉が臨界未満であっても原子炉を出力運転し続けることは可能である。以下にその仕組みを説明する。 NpF 3 does not emit neutrons or alpha rays (α rays), but as the operation continues, NpF 3 Neptunium (Np) absorbs neutrons and is converted to plutonium 238 ( 238 Pu). 238 Pu emits a lot of alpha rays. Fluorine (F) in NpF 3 emits neutrons when it reacts with α rays. Since NpF 3 becomes an external neutron source by combustion, it was called a quasi-external neutron source.
In principle, the reactor must be critical to keep the reactor operating at power. However, if there is an external neutron source, it is possible to continue the power operation of the reactor even if the reactor is subcritical. The mechanism is described below.

式１
N = S×keff×L /（１−keff ） Formula 1
N = S × keff × L / (1−keff)

上記の数式１において、Nは炉心中の全中性子数（単位：中性子数/sec）、keffは実効増倍係数で１．０未満、Sは炉心中の全外部中性子源（単位：中性子数/sec）、Lは平均中性子寿命（単位：sec）である。 In the above Equation 1, N is the total number of neutrons in the core (unit: number of neutrons / sec), keff is an effective multiplication factor of less than 1.0, and S is the total external neutron source in the core (unit: number of neutrons / sec), L is the average neutron lifetime (unit: sec).

式２
Φ＝ N×ｖ / Ｖ Formula 2
Φ = N × v / V

上記の数式２において、Φは中性子束（単位：数/(sec・ｃｍ2）)、Nは炉心中の全中性子数（単位：中性子数/sec）、ｖは炉心内の中性子平均速度（単位：ｃｍ/sec）、Ｖは炉心全体積（単位：ｃｍ3）である。 In Equation 2, Φ is the neutron flux (unit: number / (sec · cm 2 )), N is the total number of neutrons in the core (unit: number of neutrons / sec), and v is the average neutron velocity (unit: unit). : Cm / sec), and V is the entire core volume (unit: cm 3 ).

現行沸騰水型原子炉並みの出力を得るためには、Φは１０の１３乗程度である。可能な限りSを大きくしてｋeffを１．０に近づければΦを１０の１３乗程度にできる。
原子炉一般において、ｋeffは小さい程安全性が高い。大きなSの補助の元ではｋeffが１．０よりも小さい臨界未満で現行沸騰水型原子炉並みの出力を得ることができる。
運転を続けるにつれて238Puが増加するためｋeffの小さくなる燃焼末期においてSが大きくなるためΦへの寄与が大きくなる。更に、238Puは239Pu程ではないがウラン２３８（238U）やNpよりも核分裂する割合が高い。
Fはα線により中性子を放出することの他に、軽いために中性子速度を減速させる作用がある。したがって、ボイド反応度係数が若干正になり易い場合にもボイド割合が急に増加するような事故が生じても炉心内の速い中性子の割合が急に増加するのを緩和する作用があるため、燃料棒温度を過度に上昇させる事故を緩和する。プルトニウムを有効に燃焼させるために、核燃料ペレット（４４）としてＭＯＸを使った稠密格子の核燃料集合体はボイド反応度係数が小さく時には正になることもあるため特に有効である。
０．００００１程度の微妙なkeff調節には、炉心の最外側の制御棒（２２）を電動により微細に調節することができる。その他、原子炉起動時に挿入されて運転時には炉心の下に引き抜かれる外部中性子源入り棒を出力運転中に炉心に出し入れすることによりkeffを変えることなく出力調節に利用できる。また、制御棒（２２）の数本に中性子吸収物質を装荷する代わりにNpF3を装荷すると運転期間に連れて強くなる外部中性子源となり、keffを変えることなく出力調節に利用できる。 In order to obtain the output equivalent to that of the current boiling water reactor, Φ is about 10 13. If S is increased as much as possible and keff is brought close to 1.0, Φ can be set to about 10 13.
In general nuclear reactors, the smaller the keff, the higher the safety. Under the aid of a large S, keff is less than 1.0, which is less than the criticality, and an output equivalent to that of the current boiling water reactor can be obtained.
Since 238 Pu increases as the operation continues, S increases at the end of combustion when keff decreases, and the contribution to Φ increases. Furthermore, although 238 Pu is not as high as 239 Pu, it has a higher rate of fission than uranium 238 ( 238 U) or Np.
In addition to emitting neutrons by alpha rays, F has the effect of slowing down the neutron velocity because it is light. Therefore, even if the void reactivity coefficient tends to be slightly positive, even if an accident that the void ratio suddenly increases occurs, it has the effect of mitigating the rapid increase in the ratio of fast neutrons in the core, Mitigates accidents that cause excessive fuel rod temperatures. In order to burn plutonium effectively, a dense lattice nuclear fuel assembly using MOX as nuclear fuel pellets (44) is particularly effective because the void reactivity coefficient is small and sometimes positive.
For the delicate keff adjustment of about 0.00001, the outermost control rod (22) of the core can be finely adjusted electrically. In addition, an external neutron source containing rod inserted at the time of reactor start-up and pulled out under the core during operation can be used for power adjustment without changing keff by taking it into and out of the core during power operation. Moreover, when NpF 3 is loaded instead of loading neutron absorbing material on several control rods (22), it becomes an external neutron source that becomes stronger with the operation period, and can be used for output adjustment without changing keff.

図７は、核燃料集合体に装荷せる核燃料棒（３１）の数本を三フッ化ネプツニウム(NｐF３)だけを充填せる准外部中性子源棒（２３１）とした局所准外部中性子源核燃料集合体（２３０）と従来の制御棒（２２）とからなる炉心平面の部分図である。
製造並びに再処理において核燃料棒（３１）と准外部中性子源棒（２３１）を別々に取り扱うことができ易くなり、放射線遮蔽管理が容易になりコスト低下を図ることができる。 FIG. 7 shows a local quasi-external neutron source nuclear fuel assembly in which several nuclear fuel rods (31) loaded on the nuclear fuel assembly are quasi-external neutron source rods (231) filled only with neptunium trifluoride (NpF 3 ) ( 230) and a partial plan view of the core plane composed of the conventional control rod (22).
In the production and reprocessing, the nuclear fuel rod (31) and the quasi-external neutron source rod (231) can be easily handled separately, radiation shielding management is facilitated, and the cost can be reduced.

ネプツニウム（Np）とベリリウム（Be）の化合物（NpBe13）をNｐF３の代わりに、核燃料ペレット（４４）の中心または外周に装荷すると、少ないNpでも強力な外部中性子源となる。Npから変換した238Puの周りを１３個のBeが取り囲むようになっているため、238Puから放出されるα線は効率よく中性子を発生させることができる。更に、Beは高速ガンマ（γ）線と反応すると中性子を放出するため燃焼初期で238Puが蓄積されていなくても強力な外部中性子源になる。 If a compound of neptunium (Np) and beryllium (Be) (NpBe 13 ) is loaded instead of NpF 3 at the center or outer periphery of the nuclear fuel pellet (44), even a small Np becomes a powerful external neutron source. Since 13 Bes surround 238 Pu converted from Np, alpha rays emitted from 238 Pu can efficiently generate neutrons. In addition, Be reacts with fast gamma (γ) rays and emits neutrons, so it becomes a powerful external neutron source even if 238 Pu is not accumulated at the beginning of combustion.

現行沸騰水型原子炉の原子炉を変更することなく、核燃料集合体の若干の変更により、処分し難いネプツニウムを有効に利用できる。 Neptunium, which is difficult to dispose of, can be used effectively by changing the nuclear fuel assembly slightly without changing the current boiling water reactor.

従来の核燃料集合体（３０）の概観斜視図。FIG. 3 is an overview perspective view of a conventional nuclear fuel assembly (30). 従来の核燃料棒（３１）の概観図。Overview of a conventional nuclear fuel rod (31). 従来の核燃料集合体（３０）と制御棒（２２）とからなる炉心平面の部分図。FIG. 3 is a partial plan view of a reactor core composed of a conventional nuclear fuel assembly (30) and a control rod (22). 制御棒（２２）が引き抜かれた運転時における、従来の核燃料集合体（３０）からなる炉心平面の部分図。FIG. 6 is a partial plan view of a core plane composed of a conventional nuclear fuel assembly (30) during operation in which a control rod (22) is pulled out. 本発明の准外部中性子源入り核燃料棒（１３１）の概観図。FIG. 3 is a schematic view of a nuclear fuel rod (131) with an quasi-external neutron source of the present invention. 本発明の准外部中性子源入り核燃料集合体（１３０）と制御棒（２２）とからなる炉心平面の部分図。FIG. 3 is a partial plan view of a core plane composed of a nuclear fuel assembly (130) with a quasi-external neutron source and a control rod (22) according to the present invention. 本発明の局所准外部中性子源核燃料集合体（２３０）と制御棒（２２）とからなる炉心平面の部分図。The partial figure of the core plane which consists of a local quasi-external neutron source nuclear fuel assembly (230) and a control rod (22) of the present invention.

符号の説明Explanation of symbols

２０は漏洩水流路。
２２は制御棒。
３０は核燃料集合体。
３１は核燃料棒。
３２は上側結合板。
３３は下側結合板。
３４はスペーサ。
３５はチャンネルボックス。
３６は主冷却材通路。
４１は被覆管。
４２は上部端栓。
４３は下部端栓。
４４は核燃料ペレット。
４５はスプリング。
１３０は准外部中性子源入り核燃料集合体。
１３１は准外部中性子源入り核燃料棒。
１４４は三フッ化ネプツニウム（ＮｐＦ3）
２３０は局所准外部中性子源核燃料集合体。
２３１は准外部中性子源棒。
20 is a leakage water flow path.
22 is a control rod.
30 is a nuclear fuel assembly.
31 is a nuclear fuel rod.
32 is an upper coupling plate.
33 is a lower coupling plate.
34 is a spacer.
35 is a channel box.
36 is a main coolant passage.
41 is a cladding tube.
42 is an upper end plug.
43 is a lower end plug.
44 is a nuclear fuel pellet.
45 is a spring.
130 is a nuclear fuel assembly containing an associate external neutron source.
131 is a nuclear fuel rod with an associate external neutron source.
144 is neptunium trifluoride (NpF 3 )
230 is a local quasi-external neutron source nuclear fuel assembly.
231 is an associate external neutron source rod.

Claims (2)

核燃料物質を内蔵せる核燃料集合体において、核燃料ペレット（４４）の中心に三フッ化ネプツニウム(NｐF３)またはネプツニウムとベリリウムの化合物（NpBe13）を装荷した准外部中性子源入り核燃料棒（１３１）からなることを特徴とする准外部中性子源入り核燃料集合体（１３０）。 In a nuclear fuel assembly containing nuclear fuel material, from a nuclear fuel rod (131) with a quasi-external neutron source loaded with neptunium trifluoride (NpF 3 ) or a compound of neptunium and beryllium (NpBe 13 ) at the center of the nuclear fuel pellet (44) A nuclear fuel assembly (130) containing an associate external neutron source. 核燃料物質を内蔵せる核燃料集合体において核燃料棒の数本をNｐF３またはNpBe13だけを充填せる准外部中性子源棒（２３１）としたことを特徴とせる局所准外部中性子源核燃料集合体（２３０）。
Local quasi-external neutron source nuclear fuel assembly (230), characterized in that in the nuclear fuel assembly containing nuclear fuel material, several nuclear fuel rods are quasi-external neutron source rods (231) filled with only NpF 3 or NpBe 13 .
JP2004013161A 2004-01-21 2004-01-21 Nuclear fuel assembly for reactor Pending JP2005207814A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109637689A (en) * 2018-10-23 2019-04-16 中广核研究院有限公司 The production method in small cores pile neutron source

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109637689A (en) * 2018-10-23 2019-04-16 中广核研究院有限公司 The production method in small cores pile neutron source

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