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Am gamma calibration field based on international standards and its conversion coefficients辻 智也; 吉富 寛; 古渡 意彦*; 谷村 嘉彦
Radiation Protection Dosimetry, 200(15), p.1416 - 1424, 2024/09
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)A Am gamma (
)-ray calibration field that meets the requirements for a -ray reference field as specified in the ISO 4037 standard series was established in the Facility of Radiation Standards of the Japan Atomic Energy Agency. The reference air kerma rates were measured using a reference ionization chamber (IC) calibrated by the N-80 quality X-ray calibration field of the national metrology standard in Japan and with a correction to account for differences in photon energy due to the calibration field. Conversion coefficients for the Am -ray calibration field, including those not listed in the ISO 4037 standard series, were calculated based on the measured -ray fluence rate spectra.
(0.07) for extremity dose monitoring of medical personnel古渡 意彦*; 吉富 寛; 永元 啓介*; 中上 晃一*; 盛武 敬*; 欅田 尚樹*
Radiation Protection Dosimetry, 199(15-16), p.1807 - 1812, 2023/10
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)An additional individual monitoring using ring badge must be made, when inhomogenous exposure around radiation workers' extremity were critical for radiation workers. The RPLD, the GD-302M and the GD-352M have a dimension of 13.0 mm in length and 2.8 mm in diameter for outer casing and will also be a promising candidate for individual monitoring of the extremities of medical personnel. We investigated the applicability of this commercially available RPLDs to extremity dose monitoring by performing a characterization of the dosemeters by experiments and Monte Carlo (MC) calculations. The results shows that the energy response of GD-352M fully meets the IEC requirement between 20 keV and 200 keV. We also found that no significant angular dependence of responses for each model was observed and orientation of irradiation hardly affected the response. In conclusion, we demonstrated the applicability of a small RPLD to the extremity monitoring in terms of (0.07) for medical personnel.
古渡 意彦*; 窪田 卓見*; 吉富 寛; 欅田 尚樹*
Radiation Protection Dosimetry, 199(11), p.1239 - 1247, 2023/07
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)We performed an experimental investigation on occupational exposure of the eye lens and the extremity of radiation workers engaged in handling of highly activated materials in a small research accelerator facility. Using a simplified physical phantom to simulate the relevant inhomogeneous radiation exposure situations, the personal dose equivalents obtained at the eye lens and the extremities of radiation workers handling heavily radioactive converters were measured together with the dose measured by personal dosemeters worn on their trunk. Results of a mockup experiments and the Monte Carlo calculations suggest that the quantitative estimation of the eye lens doses can be estimated from the trunk dose, while the extremity doses vary considerably from the dose readings from the trunk, depending on the use of simple point-source or volume source geometry.
古渡 意彦*; 永元 啓介*; 中上 晃一*; 吉富 寛; 盛武 敬*; 欅田 尚樹*
Radiation Protection Dosimetry, 198(17), p.1303 - 1312, 2022/10
被引用回数：2 パーセンタイル：38.50(Environmental Sciences)We demonstrate a practical calibration method and its applicability for a commercially available radiophotoluminescence dosemeter (RPLD, GD-352M) to eye lens dose monitoring, by performing the calibration in accord with the ISO recommendations. The calibration was then verified through a series of experiments. For verification of the derived calibration factor (1.21 
0.04, 
= 1) of the RPLD, we performed standard irradiations in the X-ray reference fields and the mockup measurements in the actual radiation fields in a hospital. The commercially available dosemeters, DOSIRIS was also put on the ISO cylinder phantom and the RANDO phantom together with the GD-352M in the verification experiments. The personal dose equivalents 
(3) obtained from the GD-352M and those obtained from the DOSIRIS were in good agreement with each other. Our results demonstrate the proper calibration of a commercially available RPLD that is applicable to the additional monitoring of the lens of the eyes for medical personnel.
古渡 意彦; 谷村 嘉彦; Kessler, P.*; Neumaier, S.*; R
ttger, A.*
Radioisotopes, 70(1), p.1 - 18, 2021/01
For proper environmental radiation monitoring, a method to simultaneously determine ambient dose equivalent rate and radioactivity concentration in the air by using a newly developed scintillation spectrometer, namely a CeBr
spectrometer was investigated. The performance of the proposed method, including energy dependence and linearity of the spectrometer, was verified by a series of measurements, conducted according to the procedure of inter-comparison of detectors used for early warning network performed by the European Radiation Dosimetry Group (EURADOS). Measurement results show that the proposed method is suitable for environmental monitoring purposes. After thorough tests, the activity concentration in air was determined in the laboratory by using a point-like sealed 
Ba source to mimic a radioactive cloud containing 
I and Xe. The photon fluence rate was obtained from the pulse height distribution by using the unfolding method, and the activity concentration in air for radioisotopes of interest, mainly Xe, was estimated from the obtained photon fluence rate by applying the conversion coefficient evaluated via a Monte Carlo calculation. The results additionally show that the method presented in this study is reliable and suitable for the environmental radiation measurement.
scintillation spectrometer due to terrestrial gamma ray components; Application in environmental radiation monitoring古渡 意彦; 谷村 嘉彦; Kessler, P.*; Rttger, A.*
Radiation Measurements, 138, p.106431_1 - 106431_6, 2020/11
被引用回数：1 パーセンタイル：10.11(Nuclear Science & Technology)In radiological emergency, timely and reliable radiological information such as dose rate or radioactive concentrations due to artificial radionuclides is indispensable to protect general public and the first responder of the situation. The authors have investigated the method for effectively identifying and determining the radioactivity concentration using a scintillation spectrometer. In this study, the authors demonstrate how influence of terrestrial background (BG) component on measured pulse height spectrum can be minimized to obtain the peaks from gamma rays emitted by artificial radioactivity. In some cases of radiological emergency monitoring, subtraction of BG components was probe to be difficult, because the prior measurement of BG component at the place to be monitored is compulsory. By removing the BG component appropriately from measured pulse height spectrum without any prior BG measurement, the effective minimum detection limit of the spectrometer would be declined.
Cf neutron source with the spherical protection case古渡 意彦; 西野 翔; Romallosa, K. M. D.*; 吉富 寛; 谷村 嘉彦; 大石 哲也
Radiation Protection Dosimetry, 189(4), p.436 - 443, 2020/05
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)円筒形密封中性子線源に球形ステンレス製保護ケースを取り付け、中性子線源からの中性子の非等方放出について実験的に導出した。事前のモンテカルロシミュレーションで幅広い範囲で中性子放出が一定となることを検証したが、可搬型ロングカウンタによる測定でも確認することができた。予備測定及び線源への衝撃等を考慮し、われわれは更新した線源移動装置で保持できるよう中性子線源保護ケースをデザインした。実験で得られた非等方係数
(90)は、1.0020.002であり、55度から125度の幅広い範囲で、一様な中性子放出が得られることが明らかとなった。
Am and 
Sr/Y sources in terms of the eye lens monitoring in the nuclear facilities吉富 寛; 古渡 意彦
Radiation Protection Dosimetry, 188(2), p.191 - 198, 2020/02
被引用回数：2 パーセンタイル：20.42(Environmental Sciences)This paper highlights the issues of exposure inhomogeneity that are relative to eye lens monitoring for low-energy photons from Am and beta-rays from Sr/Y including a personal protective equipment because eye lens exposure has been concerned more than before due to the proposed reduction of relevant dose limit. These nuclides are common sources in the nuclear industry, which are particularly of concern. Our previous study presented a quantitative estimation of exposure inhomogeneity, which was applied to simple but typical exposure situations to the radionuclides. For the present study, exposure inhomogeneity of Am was approximately within a factor of 1.6, implying a rather homogeneous situation than expected. Regarding Sr/Y exposure, estimation from both (10) and (0.07) on trunk would lead to an over- or underestimation by a factor of more than ten. In contrast, (3) measurement on trunk will improve by up to a factor of two. With respect to the personal protective equipment, lead apron and protective glasses are effective for the 60-keV photons for both anterior-posterior (AP) and rotational (ROT) irradiations, while a full-face respirator can reduce the eye lens dose by approximately 17% for Sr/Y betas. As a whole, this study demonstrated that the effect of protective equipment can be effectively incorporated into the homogeneity evaluation.
古渡 意彦; 吉富 寛; 西野 翔; 谷村 嘉彦; 大石 哲也; Kessler, P.*; Neumaier, S.*; Rttger, A.*
Radiation Protection Dosimetry, 186(4), P. 538, 2019/12
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)原著論文の表5(B)中の単位について、nSv h
とすべきところ
Sv hと記載するミスがあったため、訂正する。
古渡 意彦; 吉富 寛; 西野 翔; 谷村 嘉彦; 大石 哲也; Kessler, P.*; Neumaier, S.*; Rttger, A.*
Radiation Protection Dosimetry, 187(1), p.61 - 68, 2019/12
被引用回数：2 パーセンタイル：19.31(Environmental Sciences)A low dose rate Cs gamma ray calibration field that fully satisfies the requirement of the ISO 4037 series was established in the Facility of Radiation Standards in Japan Atomic Energy Agency. Two different methods were employed to determine the reference air kerma rate, namely a conventional ionization chamber and a G(E) function method used a newly developed scintillation spectrometer. To fulfill the requirement of the ISO 4037 and suppress scattering of Cs gamma ray within the room as far as possible, a suitable lead collimator was introduced to limit the irradiation area at test points and placed at the middle height in an irradiation room with a grating floor. From measured results evaluated reference air kerma rates between 1.0 m and 3.0 m from the center of the source, gamma ray scattering from the room structures was found to be negligible. The resulting Cs gamma ray calibration field could provide ambient dose equivalent rates of 0.7-7.2 Sv h for use with environmental radiation monitoring devices.
古渡 意彦; 吉富 寛
Radioisotopes, 68(9), p.595 - 603, 2019/09
The recommended annual limit of equivalent dose to the lens of the eye has decreased to 20 mSv y from the current limit of 150 mSv y. In terms of occupational exposure to radiation workers, exposure inhomogeneity plays an important role when estimating the eye lens dose from readings of dosimeters worn by workers on their trunk. The authors focused on homogeneous exposure situations that radiation workers may encounter in nuclear and accelerator facilities. Moreover, the authors investigated how radiation workers are exposed non-homogeneously in homogeneous exposure scenarios, where radiation workers may usually be encountered, regardless of their radiation works. In our previous study, we proposed a methodology to quantitatively evaluate the inhomogeneity of exposure. The homogeneity of exposure was evaluated by performing Monte Carlo calculations with a mathematical phantom under the isotropic and rotational irradiation geometries due to gamma and beta rays. (3)
/(10)
exceeded 1.0 even in the case of homogeneous exposure to gamma rays. Even in the homogeneous exposure scenarios, the (3) might exceed the revised annual dose limit for radiation workers who are exposed close to annual dose limit.
吉富 寛; 古渡 意彦; 萩原 雅之*; 長畔 誠司*; 中村 一*
Radiation Protection Dosimetry, 184(2), p.179 - 188, 2019/08
被引用回数：2 パーセンタイル：19.31(Environmental Sciences)To manage the equivalent doses for radiation workers, exposure inhomogeneity is an important factor in the decision-making process related to protection measures and additional monitoring. Our previous study proposed the methodology to evaluate the inhomogeneity of exposure quantitatively. In this study, we applied proposed method to five different types of actual exposure situations in the nuclear industry. Two of them were conventionally characterized as homogeneous exposure, but the other three as inhomogeneous exposure. The evaluation of homogeneity exposure was conducted using Monte Carlo calculations with two simplified models, which were then verified with phantom experiments. Consequently, all of the evaluations reproduced the experimental results, implying that our proposed method would be applicable for actual work conditions in the nuclear industry. Furthermore, the two presumed homogeneous exposure situations were found to be rather inhomogeneous because of the contribution of positrons and the limited source region. The investigation also implies that obtaining the information on the most probable posture of the exposed worker, as well as the existence of the weekly penetrating radiation such as 
ray as a main source of exposure would be the key for more precise estimation.
scintillation detector coupled with lead shielding古渡 意彦; 谷村 嘉彦
JPS Conference Proceedings (Internet), 24, p.011037_1 - 011037_7, 2019/01
Authors attempted to apply a CeBr scintillation detector coupled with an appropriate lead shield to in-situ environmental radioactivity measurement for evaluation of surface contamination density on soil in heavily contaminated areas. Contamination by a vast amount of radioactive materials released due to the nuclear accident at the Fukushima Daiichi Nuclear Power Plant still remains. Both decontamination and remediation works have been recognized a challenging practice. Particularly, methodologies for confirmation of decontamination effect in heavily contaminated areas have been being intensively developed. This study preliminary investigates an adaptability of a shielded CeBr scintillation detector for environmental radioactivity measurement. An appropriate shielding to spectrometer would allow to limit the area to be monitored and consequently lead to expand the upper detection limit of surface contamination density on soil. In this study, determination of surface contamination density for 
Cs and 
Cs was focused. Suitable design of shielded CeBr detector was investigated so that in-situ environmental radioactivity measurement could be performed even in higher dose rate areas.
谷村 嘉彦; 西野 翔; 吉富 寛; 古渡 意彦; 大石 哲也
Progress in Nuclear Science and Technology (Internet), 6, p.134 - 138, 2019/01
福島第一原子力発電所事故のような原子力災害時においては、様々な放射性物質が環境中に放出され、線量を増加させることが考えられる。線スペクトルを測定し、核種を同定することは外部被ばくと内部被ばくの両方に対する放射線防護上重要である。そこで、市販のCdZnTeスペクトロメータを選び、線入射角度依存性と使用可能な線量率範囲をFRSの校正場で試験した。その結果、全体の85%をカバーできる135
において感度低下は15%以下であり、200Gy/h以下の空気カーマ率の場においてスペクトルが測定できることがわかった。
and SrI
(Eu) scintillation detectors for environmental monitoring古渡 意彦; 谷村 嘉彦; Kessler, P.*; Neumaier, S.*; Roettger, A.*
Progress in Nuclear Science and Technology (Internet), 6, p.81 - 85, 2019/01
The simultaneous evaluation of dose rate and radioactivity using newly developed scintillation detectors, i.e. CeBr and SrI(Eu) was investigated for environmental radiation measurement in emergency situation. Energy dependence and linearity tests of both detectors were conducted in a low background laboratory operated by the German metrological institute and found to be applicable to environmental monitoring purposes. As a result of environmental ray measurements in normal condition, evaluated air kerma rate and radioactivity in/on soil for Cs, Cs and 
K seemed consistent. Results also support that methods developed in the study are reliable and applicable to the environmental radiation measurement.
古渡 意彦; 吉富 寛; 大石 哲也; 吉澤 道夫
Progress in Nuclear Science and Technology (Internet), 6, p.86 - 90, 2019/01
This work presents a framework of decision-making for additional monitoring of eye lens dose for radiation workers in reflect to the reduction of the annual dose limit of the eye lens dose. Based on a quantitative scheme to systematically estimate (non-) homogeneity of exposure, the proposed "homogeneity index (HI)" is introduced as a criterion of condition branching for decision making of additional monitoring of eye lens dose.
古渡 意彦; Zutz, H.*; Hupe, O.*
Radiation Protection Dosimetry, 178(1), p.48 - 56, 2018/01
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)高エネルギー線校正場における、基準空気カーマ率の直接測定においては、電離箱式空気カーマ率計の壁による入射線の散乱及び吸収を考慮した補正係数を導入する必要がある。しかしながら、空気カーマ率決定法を提供する国際規格ISO4037-2では補正係数が提供されていない。そこで、EGS5を用いて計算シミュレーションにより補正係数を評価する手法を開発した。得られた補正係数は、ドイツ連邦物理工学研究所(PTB)及び原子力機構で実験的に検証され、その妥当性が検証された。
吉富 寛; 萩原 雅之*; 古渡 意彦; 西野 翔; 佐波 俊哉*; 岩瀬 広*
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1188 - 1195, 2017/11
放射線業務従事者の眼の水晶体や末端部の等価線量については、線量限度を超えていないことを確認するため、適切に評価される必要がある。さらに近年、眼の水晶体に係る線量限度引き下げがICRPにより勧告されたこと、高放射化物等の取り扱いによる末端部被ばくが懸念されることなどから、より妥当な評価が要求されている。これらの部位は体幹部から離れた位置にあることから、場の不均等性によって大きく影響を受けるが、原子力・学術分野で、その不均等性を判断するための仕組みが十分であるとは言えない。本研究では、計算と実験を組み合わせて、不均等性を判断する枠組みを提案した。新たに提案した不均等性を表す指標を数学ファントムを用いたモンテカルロ計算により求め、その妥当性をベンチマーク実験により検証した。さらに、線源条件などのパラメータを変化させたいくつかのケースについて不均等性を調べ、水晶体被ばくにおいて不均等性を判断する上で考慮すべき因子を明らかにした。一連の実験と計算により、本指標の有用性と信頼性を確認することができた。
古渡 意彦; 吉富 寛; 西野 翔; 谷村 嘉彦; 大石 哲也; 吉澤 道夫
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1230 - 1238, 2017/11
放射線モニタリングにおいては、正当な線量測定結果が妥当な意思決定に不可欠であり、線量計を正しく構成することで、それは達成できる。日本原子力研究開発機構放射線標準施設棟(以下、「FRS」という。)では、X線、線、ベータ線、中性子校正場を整備し、年間30,000台以上の線量計の国内外からの校正依頼に応じている。広範な種類の放射線校正場を整備するFRSを特徴づけるものとして、熱中性子領域(0.025eV)から20MeVまで幅広く整備された中性子校正場があり、一つの施設で国際規格の要求する性能試験を完結できることから、中性子線量計開発に大きく貢献している。近年の研究成果として、実際の作業環境で測定される、8桁以上の幅広いエネルギー分布を有する中性子場において、線量計による妥当な線量評価に資するため、Am-Be線源と黒鉛パイルを用いた作業環境模擬中性子校正場を完成させ、提供している。また、アジア地域の二次標準校正場と継続して実施している放射線校正場に関する相互比較試験についても紹介する。
西野 翔; 星 勝也; 辻村 憲雄; 古渡 意彦; 吉田 忠義
Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1258 - 1263, 2017/11
連続中性子場における線量計の応答特性を理解するために、日本原子力研究開発機構の放射線標準施設棟(FRS)及び計測機器校正施設(ICF)に整備された種々の作業環境模擬中性子校正場において、形状・検出方式の異なる4種類の中性子サーベイメータの特性試験を実施した。その結果、1MeV以下のエネルギー領域にのみ中性子フルエンス分布をもつ校正場においては、いずれのサーベイメータも、中性子線量を大きく過大または過小評価することが分かった。本発表では、場の中性子スペクトルと線量計応答の関係を示し、中性子線量計の校正のあり方について議論を行う。
