Neutron resonance fission neutron analysis for nondestructive fissile material assay

弘中 浩太; Lee, J.; 小泉 光生; 伊藤 史哲*; 堀 順一*; 寺田 和司*; 佐野 忠史*

Nuclear Instruments and Methods in Physics Research A, 1054, p.168467_1 - 168467_5, 2023/09

https://doi.org/10.1016/j.nima.2023.168467

We propose neutron resonance fission neutron analysis (NRFNA), an active nondestructive assay (NDA) technique, to improve the capability to identify and quantify a small amount of fissile material in a sample. NRFNA uses pulsed neutrons to induce fission reactions in the sample. Fission neutrons are detected by a neutron-gamma pulse shape discrimination (PSD) scintillation detector with time-of-flight (TOF) technique. The obtained nuclide-specific resonance peaks in the neutron energy spectrum provide information to identify and quantify a fissile material in the sample. The possibility of using PSD for NRFNA was confirmed through a test experiment using a natural uranium sample. We successfully observed the resonance peaks from U(n,f) reaction and showed that NRFNA would be useful for measuring a small amount of fissile material in a sample.

Measurement of thick target neutron yield at 180 for a mercury target induced by 3-GeV protons

松田 洋樹; 岩元 大樹; 明午 伸一郎; 竹下 隼人*; 前川 藤夫

Nuclear Instruments and Methods in Physics Research B, 483, p.33 - 40, 2020/11

https://doi.org/10.1016/j.nimb.2020.09.012

大強度陽子加速器施設J-PARCにおいて、3GeV陽子入射による水銀標的から180度方向に放出される中性子のエネルギースペクトルを測定した。得られた結果は、粒子輸送計算コードPHITSによる計算結果と明らかな差異が見られ、その傾向はインジウムやニオビウムの放射化箔を用いた反応率実験の結果と一致することがわかった。鉛標的に対するGeV領域陽子入射中性子二重微分断面積の後方角におけるエネルギースペクトルの実験データとPHITSの核反応モデルを比較したところ、この差異は3GeV付近における核反応モデルによる中性子生成あるいは弾性散乱外断面積の記述に起因していることが示唆された。

Neutron resonance analysis for nuclear safeguards and security applications

Paradela, C.*; Heyse, J.*; Kopecky, S.*; Schillebeeckx, P.*; 原田 秀郎; 北谷 文人; 小泉 光生; 土屋 晴文

EPJ Web of Conferences, 146, p.09002_1 - 09002_4, 2017/09

https://doi.org/10.1051/epjconf/201714609002

Neutron-induced reactions can be used to study the properties of nuclear materials in the field of nuclear safeguards and security. The elemental and isotopic composition of these materials can be determined by using the presence of resonance structures in the reaction cross sections as fingerprints. This idea is the basis of two non-destructive analytical techniques which have been developed at the GELINA neutron time-of-flight facility of the JRC-IRMM: Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). A full quantitative validation of the NRTA technique was obtained by determining the areal densities of enriched reference samples used for safeguards applications with an accuracy better than 1%. Moreover, a combination of NRTA and NRCA has been proposed for the characterisation of particle-like debris of melted fuel formed in severe nuclear accidents. In order to deal with the problems due to the diversity in shape and size of these samples and the presence of strong absorbing matrix materials, new capabilities have been implemented in the resonance shape analysis code REFIT. They have been validated by performing a blind test in which the elemental abundance of a combined sample composed of unknown quantities of materials such as cobalt, tungsten, rhodium or gold was determined with accuracies better than 2%.

The New vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance

Wei, C.*; Chiaveri, E.*; Girod, S.*; Vlachoudis, V.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他126名*

Nuclear Instruments and Methods in Physics Research A, 799, p.90 - 98, 2015/11

https://doi.org/10.1016/j.nima.2015.07.027

At the neutron time-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beamline and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds.

Generalized analysis method for neutron resonance transmission analysis

原田 秀郎; 木村 敦; 北谷 文人; 小泉 光生; 土屋 晴文; Becker, B.*; Kopecky, S.*; Schillebeeckx, P.*

Journal of Nuclear Science and Technology, 52(6), p.837 - 843, 2015/06

https://doi.org/10.1080/00223131.2014.982738

Neutron resonance densitometry (NRD) is a non-destructive analysis method, which can be applied to quantify special nuclear materials (SNM) in small particle-like debris of melted fuel that is formed in severe accidents of nuclear reactors such as the Fukushima Daiichi Nuclear Power Plants. NRD uses neutron resonance transmission analysis (NRTA) to quantify SNM and neutron resonance capture analysis (NRCA) to identify matrix materials and impurities. In order to generalize NRD for the characterization of arbitrary-shaped thick materials, a generalized method to analyze NRTA data has been developed. The method has been applied on data resulting from transmission through non-uniform thick samples with varying areal density of SNM up to 0.253 at/b (100 g/cm). The investigation shows that NRD could be used to quantify SNM in not only uniform samples made of small particle-like debris but also non-uniform samples made of large rock-like debris with high accuracy by utilizing the generalized analysis method for NRTA.

Experiment on angular neutron flux spectra from lead slabs bombarded by D-T neutrons

前川 洋; 大山 幸夫

Fusion Engineering and Design, 18, p.287 - 291, 1991/00

https://doi.org/10.1016/0920-3796(91)90140-L

鉛は核融合炉ブランケットの中性子増倍材として有力視されている。核データを検証するためのベンチマークデータを取得する目的で、鉛平板体系からの中性子角度束スペクトルを中性子飛行時間法で測定した。体系は直径630mm、厚さ50.6、203、405の3種類である。測定した角度は、0、12.2、24.9、41.8、66.8度である。実験結果の解析はモンテカルロコードMCNPとSNコードDOT3.5を用いて行なった。実験結果と計算結果の比較から、JEDL-3はその暫定版に比べて大幅な改善がみられた。5~11MeVのエネルギー領域で両者のスペクトルに差がある。この差を改善するためには核データファイルの非弾性散乱レベルの数の制限を増すか、複数のレベルを合体した疑似的レベルを採用する必要がある。

中性子飛行時間法による減速材体系の熱中性子スペクトルに関する研究

秋濃 藤義

JAERI-M 82-207, 180 Pages, 1982/12

JAERI-M-82-207.pdf:5.16MB

原子炉の炉心核設計において、炉心の熱中性子スペクトルを正確に把握するには、減速材の熱中性子散乱断面積の適否が主要な要因となる。そこで常温から800Cの高温黒鉛体系、および常温の軽水均質体系および軽水-天然ウラン非均質体系における0方向の角度熱中性子スペクトル測定をLINAC-TOF法で行い、計算との比較から熱中性子散乱モデル(黒鉛に対しYoung-Koppelモデル、軽水に対しHaywoodモデルを採用)の熱中性子スペクトルの記述能力を調べた。また、この熱中性子スペクトルの計算方法を用い黒鉛減速20%濃縮ウラン半均質臨界実験装置(SHE)における臨界質量、実験用可燃性毒物棒および実験用制御棒の反応度価値等の実験解析を行い、計算予測精度を明確にした。これらの実験結果は高温ガス実験炉の核設計の計算精度評価に使用された。

Development of a table-top NRTA system, 2; Monte Carlo study for Pu pellet sample measurement

Guembou Shouop C.; 土屋 晴文

no journal, , 

Neutron Resonance Transmission Analysis (NRTA) is a promising nondestructive assay technique to determine the quantities of uranium, plutonium, higher-order actinides, and fission products in spent fuel. However, existing NRTA systems are large and therefore impractical. Downsizing the NRTA system for mobility and in-situ assessment could be achieved via spontaneous fission neutron radioactive sources such as Cf, which require appropriate collimation systems. In this presentation, Monte Carlo studies assessed the capability of NM detection in small samples such as Pu pellets. Time-of-flight spectra obtained with a Pu pellet sample showed resonance dips for polyethylene containing and polyethylene containing LiF collimator types whereas those for polyethylene and air have no clear resonance dips. These results indicated that the table-top NRTA system under development can effectively detect Pu nuclides in small samples such as Pu pellets, considering PE- configuration. This research was implemented under the subsidy for nuclear security promotion of MEXT.