Development and testing of a delayed gamma-ray spectroscopy instrument utilizing Cf-252 neutrons evaluated for nuclear safeguards applications

Rodriguez, D.; Abbas, K.*; 小泉 光生; Nonneman, S.*; Rossi, F.; 高橋 時音

Nuclear Instruments and Methods in Physics Research A, 1014, p.165685_1 - 165685_10, 2021/10

https://doi.org/10.1016/j.nima.2021.165685

Under the MEXT subsidy on research for improving nuclear security related development, we designed the Delayed Gamma-ray Californium Test (DGCT) instrument. From He-3 count-rate experiments performed in collaboration with the European Commission Joint Research Centre, we show the effective neutron flux entering the sample space. Further, we show delayed gamma-ray spectra of both U and Pu samples as well as a comparison to the background from Cf activation of the environment. Finally, we make comparisons to earlier spectra obtained using PUNITA, including relative fission capability, spectral signature, and mass correlations.

Utilizing PUNITA experiments to evaluate fundamental delayed gamma-ray spectroscopy interrogation requirements for nuclear safeguards

Rodriguez, D.; 小泉 光生; Rossi, F.; 瀬谷 道夫; 高橋 時音; Bogucarska, T.*; Crochemore, J.-M.*; Pedersen, B.*; 高峰 潤

Journal of Nuclear Science and Technology, 57(8), p.975 - 988, 2020/08

https://doi.org/10.1080/00223131.2020.1742812

Present safeguards verification methods of high-radioactivity nuclear material use destructive analysis techniques since passive nondestructive techniques are incapable of determining the nuclear material content. To improve this verification process, the JAEA and EC-JRC Ispra, Italy have been collaborating to develop delayed gamma-ray spectroscopy for composition analysis of the fissile nuclides as an aspect of the MEXT subsidy for improving nuclear security and the like. Multiple experiments were performed over three years using PUNITA to interrogate U and Pu samples to determine the signature from the short-lived fission products. We observed many gamma rays useful to determine the composition of a mixed nuclear material sample. Presented here are the results of these measurements with correlations to the interrogation, mass, volume, and sample homogeneity.

Model design of a compact delayed gamma-ray moderator system using Cf for safeguards verification measurements

Rodriguez, D.; Rossi, F.; 高橋 時音; 瀬谷 道夫; 小泉 光生

Applied Radiation and Isotopes, 148, p.114 - 125, 2019/06

https://doi.org/10.1016/j.apradiso.2019.01.002

Delayed gamma-ray spectroscopy is an active-NDA technique used to determine the composition of HRNM samples by peak-ratio comparison of GRs above 3-MeV from the short-lived fission products. Filtering out the passive GRs from long-lived FPs reduces the DGS signal, so thermal neutrons are used to induce more fission events from fissile nuclides. We are developing a compact system to moderate 2-MeV neutrons that are easier to moderate than 14-MeV neutrons from DT generators. This work describes the ideal moderator optimization for a Cf source that results in cm passing through the sample space with 70% of those below 1-eV. Practical modifications resulted in 20% reductions compared to the optimized design. Evaluations of DGS signals and backgrounds conclude that only a 21-MBq Cf source is required.

Delayed gamma-ray spectroscopy inverse Monte Carlo analysis method for nuclear safeguards nondestructive assay applications

Rodriguez, D.; Rossi, F.; 瀬谷 道夫; 小泉 光生

Proceedings of 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC 2017) (Internet), 3 Pages, 2018/11

The JAEA and EC JRC are collaborating to improve the ability to quantify the uranium and plutonium content of highly radioactive and mixed nuclear material for nuclear safeguards verification. A separate program focuses on improving the capability to measure, analyze, and predict the delayed gamma-ray spectrum used to determine the nuclide ratios within a sample. Measurements performed at the JRC-Ispra are used to correlate the observed DGs to the composition that are then used to calibrate a DG Monte Carlo. The MC has the ability to predict expected DGs, provide a sensitivity analysis to optimize future measurements, and can be used to analyze a spectrum using an inverse MC technique. Analyzing MC with this IMC analysis provides a way to determine systematic uncertainty as well as statistical uncertainty when multiple measurements are not feasible. This work will describe the efforts to develop the DGSMC and how it will be utilized for current and future applications.

Development of delayed gamma-ray spectroscopy for nuclear material analysis

Rodriguez, D.; Rossi, F.; 高橋 時音; 瀬谷 道夫; 小泉 光生; Crochemore, J. M.*; Varasano, G.*; Bogucarska, T.*; Abbas, K.*; Pedersen, B.*

Proceedings of INMM 59th Annual Meeting (Internet), 7 Pages, 2018/07

DGS has great potential for HRNM, since it determines fissile nuclide compositions by correlating the observed DG spectrum to the unique FY of the individual nuclides. Experiments were performed with LRNM using both PUNITA and a JAEA designed Cf-shuffler tested in PERLA. The data was analyzed using an inverse MC method that both determines DG peak intensity correlations and provides an evaluation of the uncertainty of the measurements. The results were used to verify DG signatures for varying fissile compositions, total fissile content, and DGS interrogation timing patterns. Future development will focus on measuring HRNM and designing a compact system by evaluating different neutron sources, moderating materials, and detection capabilities. This presentation summarizes the JAEA/JRC DGS program to date and the future direction of this collaborative work performed using the MEXT subsidy for the promotion of strengthening nuclear security.

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%.

IAEA保障措置技術及び人材育成に対するJAEAの貢献

直井 洋介; 小田 哲三; 富川 裕文

日本原子力学会誌ATOMO, 58(9), p.536 - 541, 2016/09

日本は1955年に制定された原子力基本法に従い、原子力の研究開発、原子力エネルギーの利用を平和目的に限って推進してきた。平和目的に限られていることを担保するため、事業者は計量管理を行い、IAEAと保障措置協定を締結する以前は二国間原子力協定(日米,日仏,日加等)に基づき報告を行い、1977年のIAEAとの保障措置協定を締結後は国内法が改定され、それに基づき計量管理及びその報告が行われてきた。1999年には追加議定書を締結して新たな義務を負うIAEAの保障措置活動に対応してきており、これまでわが国の原子力活動についての申告の正確性と完全性がIAEAによって検認されてきている。2004年には、核物質の転用や未申告の活動はないとの「拡大結論」を得て以降、これまで毎年この拡大結論を得てきている。本報告では、原子力機構がこれまで取り組んできたIAEAの保障措置に必要な技術開発や人材育成への協力などIAEA保障措置活動への貢献について報告する。

Uranium particle identification with SEM-EDX for isotopic analysis by secondary ion mass spectrometry

江坂 文孝; 間柄 正明

Mass Spectrometry Letters, 7(2), p.41 - 44, 2016/06

https://doi.org/10.5478/MSL.2016.7.2.41

保障措置環境試料中の個別ウラン粒子の分析(パーティクル分析)は、二次イオン質量分析(SIMS)法などにより行われている。この際、あらかじめ試料中に含まれる多くの粒子からウランを含む粒子を特定する必要があり、これまで分析の律速になっていた。本研究では、走査型電子顕微鏡の反射電子像を利用した自動分析により効率的にウラン粒子を特定し、SIMS法により同位体比分析を行う方法について検討した。本検討により分析条件の最適化を行った結果、1000倍の倍率で反射電子像を観測することにより、直径1m程度のウラン粒子を効率的に特定できることが確かめられた。

The States of the art of the nondestructive assay of spent nuclear fuel assemblies; A Critical review of the Spent Fuel NDA Project of the U.S. Department of Energy's Next Generation Safeguards Initiative

Bolind, A. M.*; 瀬谷 道夫

JAEA-Review 2015-027, 233 Pages, 2015/12

JAEA-Review-2015-027.pdf:30.21MB

米国エネルギー省/国家安全保障庁の次世代保障措置イニシアティブ(NGSI)での「使用済み燃料非破壊測定プロジェクト」で検討されている14の最新の使用済み燃料集合体非破壊測定(NDA)技術手法に関する調査研究成果を報告するとともに、このNDAの精度の観点からの議論と批評を行う。この報告書では、現在提案されているNDA方法に関する主たる問題である測定結果の大きな曖昧さ(誤差)が、第一義的には独立な測定手法で行っていないことから発生していることを示す。この報告書では筆者らは、NDA結果を改善するためには、NDAの物理量が3次元構成となっているため、少なくとも3つの独立したNDA手法が必要であることを示す。

Utilizing delayed rays for fissionable material measurement in NDA

Rodriguez, D.; 高峰 潤; 小泉 光生; 瀬谷 道夫

Proceedings of 37th ESARDA Annual Meeting (Internet), p.831 - 836, 2015/08

パルス中性子源を用いる非破壊測定装置がJAEAとJRC(ITU及びIRMM)との共同で設計される予定である。このシステムは中性子共鳴透過分析法、時間差ダイアウェイ法、即発・遅発線スペクトル分析法の組合せを利用する予定である。遅発線スペクトル分析法は核分裂性核種の比を比較的高い精度で決めることができる方法である。このシステムはMOX中あるいは高自発中性子・線放射核物質(溶融燃料を含む)の核種組成比を有効に決定することができ、保障措置に適用できるものである。また、このシステムは透過力の強い高エネルギーの遅発線を検知することで核セキュリティ分野へも適用が可能である。この論文では、この非破壊装置の遅発線スペクトル分析法部分の初期状況について、また、対象核物質の高精度組成分析を行う上で他の方法と連携してどのように使われるか、について記述する。