Applicability of differential die-away self-interrogation technique for quantification of spontaneous fission nuclides for fuel debris at Fukushima Daiichi Nuclear Power Plants

長谷 竹晃; 相樂 洋*; 小菅 義広*; 能見 貴佳; 奥村 啓介

Journal of Nuclear Science and Technology, 60(4), p.460 - 472, 2023/04

https://doi.org/10.1080/00223131.2022.2114958

This paper provides an overview of the applicability of the Differential Die-Away Self-Interrogation (DDSI) technique for quantification of spontaneous fissile nuclides in fuel debris at the Fukushima Daiichi Nuclear Power Plants. In this research, massive fuel debris stored in a canister was evaluated, and the void space of the canister was assumed to be filled with water for wet storage and air for dry storage. The composition of fuel debris was estimated based on elements such as the inventory in the reactor core and operation history. The simulation results show that for wet storage, the DDSI technique can properly evaluate the neutron leakage multiplication and quantify spontaneous fissile nuclides with a total measurement uncertainty (TMU) of approximately 8%. For dry storage, the known-alpha technique, which was previously established, can be applied to quantify spontaneous fissile nuclides with a TMU of approximately 4%. In both cases, the largest uncertainty factor is the variation in water content in the canister. In the case of wet storage, the uncertainty could be significantly increased in cases where the fuel debris is extremely unevenly distributed in the canister.

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.

Development of active non-destructive analysis technologies for nuclear nonproliferation and security of JAEA

小泉 光生

Proceedings of 41st ESARDA Annual Meeting (Internet), p.260 - 267, 2019/05

The Japan atomic energy agency (JAEA) is developing active non-destructive analysis (NDA) technologies for nuclear nonproliferation and security under the support of the subsidiary of for "promotion of strengthening nuclear security or the like" of the Japanese government MEXT. One of the programs is "development of active neutron NDA techniques", in which four techniques are developed: i.e., Differential Die Away Analysis (DDA), Delayed Gamma-ray Analysis (DGA), Neutron Resonance Transmission Analysis (NRTA), and Prompt Gamma-ray Analysis (PGA). These techniques are used to complement each other. They would be useful for nuclear material accountancy, applicable to both low- and high-level radioactive nuclear materials (NMs), and for nuclear security purposes such as detection of NM and explosive materials. Another program is development of nuclear resonance fluorescence (NRF) technique for detection of NM hidden in a shield. This technique utilizes quasi monochromatic gamma-rays produced by laser Compton scattering (LCS) to irradiate a suspicious sample and observe NRF gamma-rays from that. Demonstration experiment of this technique will be performed soon. In this paper, the development projects are overviewed.

Application of probability generating function to the essentials of nondestructive nuclear materials assay system using neutron correlation

細馬 隆

JAEA-Research 2016-019, 53 Pages, 2017/01

JAEA-Research-2016-019.pdf:5.71MB

核物質非破壊測定システムの基礎への確率母関数の適用について研究を行った。最初に、高次の中性子相関を七重相関まで代数的に導出し、その基本的な性格を調べた。高次の中性子相関は、漏れ増倍率の増大に応じて急速に増大し、検出器の効率や設定によるが漏れ増倍率が1.3を超えると、より低次の中性子相関と交わり追い越してゆくことを見出した。続いて、高速中性子と熱中性子が共存する系において、高速中性子による核分裂数と二重相関計数率及び熱中性子による核分裂数と二重相関計数率を、代数的に導出した。従来の測定法と、differential die-away self-interrogation法によって得られるRossi-alpha結合分布と各エリアの面積比を用いれば、高速中性子と熱中性子それぞれの単位時間あたりの誘導核分裂数、ソース中性子1個あたりそれぞれの誘導核分裂数(1未満)及びそれぞれの二重相関計数率を、推定可能であることを見出した。