Evaluation of analytical uncertainty in quantitative determination of elements; The Case of boron

墨田 岳大*; 大澤 崇人; Chiu, I.-H.; 池田 篤史

Analytica Chimica Acta, 1329, p.343256_1 - 343256_10, 2024/11

https://doi.org/10.1016/j.aca.2024.343256

The uncertainty including accuracy and precision is the most vital factor that determines the overall quality of quantitative analysis. The objectives of this study are (1) to investigate the analytical uncertainty of a prompt gamma-ray analysis (PGA), a chemical interference-free method in principle, on the quantitative analysis of boron and (2) to evaluate the applicability of inductively coupled plasma optical emission spectrometry (ICP-OES), a common technique for quantitative elemental analysis including boron. PGA provided analytical quantity that is equivalent to the true quantity. The analytical uncertainty in both methods was adequately evaluated by comparing the results from PGA and ICP-OES for a series of boron-containing materials with different physical/chemical properties and the major sources of uncertainty in both methods are specified. The evaluation concept demonstrated in this study could be beneficial to a wide range of analytical chemistry.

Cavity ionization chamber responses in the JAEA and the NMIJ high-energy photon reference fields for radiation protection

石井 隼也*; 清水 森人*; 加藤 昌弘*; 黒澤 忠弘*; 辻 智也; 吉富 寛; 谷村 嘉彦; 渡部 浩司*

Journal of Radiological Protection, 44(3), p.031516_1 - 031516_8, 2024/09

https://doi.org/10.1088/1361-6498/ad7a07

The dosimeter response should be calibrated in a reference field near the user's radiation environment. Environments around nuclear reactors and radiation therapy facilities have high-energy photons with energies exceeding that of Co gamma rays, and controlling exposure to these photons is important. The Japan Atomic Energy Agency (JAEA) and National Metrology Institute of Japan (NMIJ) have high-energy reference fields with energies above several MeV for different types of accelerators. Their reference fields have different fluence-energy distributions. In this study, the energy dependencies of the two-cavity ionization chambers, which are often used by secondary laboratories, were experimentally and computationally evaluated for each high-energy field. These results agreed well with relative expanded uncertainties ( = 2), and their capabilities for air kerma measurements in each high-energy reference field were confirmed. Therefore, the capabilities of the air-kerma measurements can be verified in the two high-energy reference fields.

Comparative study of radiation mapping technologies for nuclear disaster assessment

越智 康太郎; Barker, E.*; 中間 茂雄; Gleizes, M.*; Manach, E.*; Vincent, F.*; 眞田 幸尚

Journal of Disaster Research, 19(2), p.429 - 445, 2024/04

https://doi.org/10.20965/jdr.2024.p0429

周辺線量当量率(空間線量率)分布のマッピング技術は、各国で統一された明確な基準はない。本研究では、日本原子力研究開発機構とフランス放射線防護・原子力安全研究所が共同で、福島第一原子力発電所周辺において、歩行サーベイ、車両サーベイ、無人ヘリコプターサーベイを実施し、各機関のモニタリング手法の有効性を確認した。例えば、歩行サーベイでは、検出器で得られた計数率を空間線量率に換算する際に、ガンマ線エネルギーの異なる放射性核種からの寄与を考慮するかどうかで、両機関が測定した空間線量率の間にずれが生じることが確認された。本研究のように、各国のマッピング技術を比較し、相互にフィードバックすることで、原子力発電所事故後のゾーニングシナリオの精度を向上させることができると思われる。

連携計測による線源探査ロボットシステムの開発研究(委託研究); 令和4年度英知を結集した原子力科学技術・人材育成推進事業

廃炉環境国際共同研究センター; 東北大学*

JAEA-Review 2023-030, 80 Pages, 2024/03

JAEA-Review-2023-030.pdf:4.96MB

日本原子力研究開発機構(JAEA)廃炉環境国際共同研究センター(CLADS)では、令和4年度英知を結集した原子力科学技術・人材育成推進事業(以下、「本事業」という)を実施している。本事業は、東京電力ホールディングス株式会社福島第一原子力発電所の廃炉等をはじめとした原子力分野の課題解決に貢献するため、国内外の英知を結集し、様々な分野の知見や経験を、従前の機関や分野の壁を越えて緊密に融合・連携させた基礎的・基盤的研究及び人材育成を推進することを目的としている。平成30年度の新規採択課題から実施主体を文部科学省からJAEAに移行することで、JAEAとアカデミアとの連携を強化し、廃炉に資する中長期的な研究開発・人材育成をより安定的かつ継続的に実施する体制を構築した。本研究は、令和3年度に採択された研究課題のうち、「連携計測による線源探査ロボットシステムの開発研究」の令和4年度分の研究成果について取りまとめたものである。本研究は、ガンマ線の飛来方向を検出可能な検出器を開発し、これを搭載した複数のロボットの連携により、単一センサーでは得られない広視野・迅速・安価な放射線源探査を実現するロボットシステム(Cooperative Operation Robot system for RAdiation Source Exploration: CORRASE、コラッセ)を開発することを目的とする。東京電力ホールディングス(株)福島第一原子力発電所の現場への投入に資することを目的として、線源探査を行う小型ロボットに放射線計測機器を搭載したシステムを3年間の計画終了時に完成させるための研究を行う。令和4年度は以下の成果を得た。多面体型とコーデットキューブ型のガンマ線イメージャーの製作を行い、点線源の位置推定に成功した。LiDARを用いた周囲環境測定結果に基づく環境地図作成システムの開発および環境地図上に放射線源分布推定結果を融合して表示するシステムの開発を行った。環境地図と粗い放射線源分布推定結果に基づき、検出器の特性に応じて複数台のロボットが指定した箇所の詳細な測定を行うための観測地点計画手法の開発を行った。小型ロボットに搭載する放射線測定器の評価のために検出器姿勢自動制御システムを製作した。また、多面体型検出器による線源探査のシミュレーションを行った。複数の線源がある場合でもほぼ線源位置を特定することができた。

Feasibility of using BeO rods as secondary neutron sources in the long-life fuel cycle high-temperature gas-cooled reactor

Ho, H. Q.; 石井 俊晃; 長住 達; 小野 正人; 島崎 洋祐; 石塚 悦男; 澤畑 洋明; 後藤 実; Simanullang, I. L.*; 藤本 望*; et al.

Nuclear Engineering and Design, 417, p.112795_1 - 112795_6, 2024/02

https://doi.org/10.1016/j.nucengdes.2023.112795

External sources of neutron provide stable and sufficient neutron for initial startup of a nuclear reactor. They also provide signals for neutron detectors to monitor the safety of reactor during shutdown. In the high temperature engineering test reactor, Cf is used as the external neutron source. However, the Cf sources must be renewed every approximately 7 years because of its relatively short half-life of 2.6 years. The renewal of Cf sources requires a high cost and a very complicated procedure. This study investigated the feasibility of using BeO rods as the secondary neutron sources to avoid renewing the Cf neutron sources periodically. The BeO rods could exist in the reactor for a long time so that if the reactor operates long enough, the neutron flux at the wide-range monitoring detectors remains significant even if the reactor is shutdown for as long as 5 years. The results of this study indicated that using BeO rods as the secondary neutron sources would be an attractive option for the future HTGR design with a long-life fuel cycle.

Feasibility study of reactor radiation photon spectroscopy in Fugen for nuclear decommissioning

冠城 雅晃; 宮本 勇太; 森 教匡; 岩井 紘基; 手塚 将志; 黒澤 俊介*; 田川 明広; 高崎 浩司

Journal of Nuclear Science and Technology, 9 Pages, 2024/00

https://doi.org/10.1080/00223131.2024.2417786

Nuclear decommissioning has recently accelerated, particularly following the accident at Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Holdings. -ray/X-ray (radiation photon) spectroscopy provides information on the types of radionuclides with radiation photon emissions. Radiation photon spectroscopy in a control rod guide tube positioned at the center of Fugen was conducted. Fugen is a prototype advanced thermal reactor with 165 MWe electric power generation that is being decommissioned. The dose rates measured in a control rod guide tube positioned at the center of the reactor were 4.19.1 Gy/h. The dose rate considerably increased at a position close to a tank that contained Co caused by the radioactivation of stainless steel. Radiation photon spectroscopy was performed without radiation shielding, identifying Co with an energy resolution better than 5.4% at 1333 keV and Nb with an energy resolution better than 5.9% at 871 keV.

Delayed gamma-ray spectroscopy for mixed nuclear material safeguards verification

Rodriguez, D.; 赤松 駿介*; Rossi, F.; 鈴木 敏*; 高橋 時音

第44回日本核物質管理学会年次大会会議論文集(インターネット), 4 Pages, 2023/12

Under the MEXT subsidy for improving nuclear material security related activities, we present the latest JAEA/ISCN delayed gamma-ray instrument, FSAI; preliminary characterization results; and the experimental and analysis development activities planned using it.

Development of a DDA+PGA-combined non-destructive active interrogation system in "Active-N"

古高 和禎; 大図 章; 藤 暢輔

Nuclear Engineering and Technology, 55(11), p.4002 - 4018, 2023/11

https://doi.org/10.1016/j.net.2023.07.015

An integrated neutron interrogation system has been developed for non-destructive assay of highly radioactive special nuclear materials, to accumulate knowledge of the method through developing and using it. The system combines a differential die-away (DDA) measurement system for the quantification of nuclear materials and a prompt gamma-ray analysis (PGA) system for the detection of neutron poisons which disturb the DDA measurements; a common D-T neutron generator is used. A special care has been taken for the selection of materials to reduce the background gamma rays produced by the interrogation neutrons. A series of measurements were performed to test the basic performance of the system. The results show that the DDA system can quantify plutonium of as small as 20~mg and it is not affected by intense neutron background up to 4.2~TBq and gamma ray of 2.2~TBq. As a result of the designing of the combined system as a whole, the gamma-ray background counting rate at the PGA detector was reduced down to s even with the use of the D-T neutron generator. The test measurements show that the PGA system is capable of detecting less than 1~g of boron compound and about 100~g of gadolinium compound in~30 min. This research was implemented under the subsidy for nuclear security promotion of MEXT.

Identification of depth location of a radiation source by measurement from only one direction using a Compton camera

佐藤 優樹

Applied Radiation and Isotopes, 195, p.110739_1 - 110739_9, 2023/05

https://doi.org/10.1016/j.apradiso.2023.110739

In the decommissioning work environment of a nuclear power plant, it is essential to accurately identify the location of radiation sources to reduce worker doses and develop decontamination plans. In this regard, gamma-ray imagers are promising devices in the visualization of the location of radiation sources. However, they can only estimate the direction in which the radiation source is located and not the distance to the source. A previous study has reported a method to identify the three-dimensional coordinates of the radiation source by measuring from multiple viewpoints with a gamma-ray imager. In some cases, the many pieces of object located at the actual decommissioning site limit the accessible area, making it difficult to measure the target area from multiple viewpoints. Thus, the present study devised and demonstrated a method of estimating the distance to the radiation source by measuring from only one direction using a Compton camera, a type of gamma-ray imager. The proposed method considered the reconstructed image intensity to be proportional to the inverse square of the distance to radiation source. This approach will be useful in accurately locating radiation sources in environments with limited workable areas, such as the broken reactor buildings inside the Fukushima Daiichi Nuclear Power Station.

JAEA/ISCN delayed gamma-ray spectroscopy inverse Monte Carlo development status

Rodriguez, D.; Rossi, F.

Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 9 Pages, 2023/05

Under the MEXT subsidy for the improvement of nuclear security related activities, we will present on the current and future progress of the delayed gamma-ray spectroscopic analysis development. We highlight a paper soon to be released and the plan for finalizing the project goal.