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Journal Articles

Variation of internal doses caused by differences in physical characteristics between the average Japanese and the ICRP's reference man which is based on the standard data of Caucasians in the dosimetric methodology in conformity to the 2007 Recommendations

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

Journal of Nuclear Science and Technology, 59(5), p.656 - 664, 2022/05

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

It is known that internal doses depend on the physical characteristics of an evaluation subject. Internal dose coefficients provided by the International Commission on Radiological Protection (ICRP) are evaluated using the characteristics of the standard Caucasian. It is important to grasp the variations of doses due to the differences in characteristics between Japanese and Caucasian when the dose coefficients of ICRP are applied to Japanese. This study evaluated dose coefficients using specific absorbed fraction (SAF) data based on the average adult Japanese physique which was developed by modification of the existing Japanese SAF data with additional calculations to make the existing data fit to the current dosimetric methodology of ICRP and compared them to those provided by ICRP. As a result, the discrepancies in dose coefficients were smaller than plus or minus 10% in most intake conditions. However, some intake conditions indicated varieties over 40% due to the differences in organ masses, amount of adipose tissues around the thoracic cavity, and so on. This information is useful in application of ICRP's dose coefficients to population of which physical characteristics are different from those of Caucasian. Further, the Japanese SAF data is published as an appendix of this paper.

JAEA Reports

Effective dose coefficients for internal exposure dose assessment in accordance with ICRP 2007 recommendations (Contract research)

Takahashi, Fumiaki; Manabe, Kentaro; Sato, Kaoru

JAEA-Review 2020-068, 114 Pages, 2021/03

JAEA-Review-2020-068.pdf:2.61MB

Radiation safety regulations have been currently established based on the 1990Recommendation by the International Commission on Radiological Protection (ICRP) in Japan. Meanwhile, ICRP released the 2007 Recommendation that replaces the 1990 Recommendation. Thus, the Radiation Council, which is established under the Nuclear Regulation Authority (NRA), has made discussions to incorporate the purpose of the 2007 Recommendation into Japanese regulations for radiation safety. As ICRP also has published effective dose coefficients for internal exposure assessment in accordance with the 2007recommendation, the technical standards are to be revised for the internal exposure assessment method in Japan. Currently, not all of the effective doses have been published to revise concentration limits for internal exposure protections of workers and public. The published effective dose coefficients are applied to radionuclides which are important in radiation protection for internal exposure of a worker. Thus, we review new effective dose coefficients as well as basic dosimetry models and data based upon Occupational Intakes of Radionuclides (OIR) parts 2, 3 and 4 that have been published from 2016 to 2019 by ICRP. In addition, issues are sorted out to provide information for revision of the technical standards for internal exposure assessment based on the 2007 Recommendations in future.

JAEA Reports

Internal dose coefficients for various gastrointestinal absorption fractions (Contract research)

Hirouchi, Jun; Tokashiki, Yuji*; Takahara, Shogo; Manabe, Kentaro

JAEA-Research 2021-001, 284 Pages, 2021/03

JAEA-Research-2021-001.pdf:4.23MB

Doses to the public are calculated with internal dose coefficients based on the publications of the International Commission on Radiological Protection (ICRP) in OSCAAR, which is a level 3 Probabilistic Risk Assessment code developed by Japan Atomic Energy Agency (JAEA). The gastrointestinal absorption fraction, $$f_{1}$$, which is one of parameters of internal dose coefficient, is given the recommended value. However, although it has been reported that $$f_{1}$$ has uncertainty, the uncertainty analysis of $$f_{1}$$ has been performed on few radionuclides. In this report, to evaluate the influence of uncertainty of $$f_{1}$$ on the internal dose, we calculated the internal dose coefficient with various $$f_{1}$$, and derive the relationship between the coefficient and $$f_{1}$$. As a result, we indicate that the relationships are expressed by a linear function for radionuclides with a half-life of more than 0.5 days and are expressed by a cubic function for radionuclides with a half-life of less than 0.5 days.

Journal Articles

Organ absorbed dose estimation reflecting specific organ masses with simple scaling of reference doses using the organ masses

Manabe, Kentaro; Koyama, Shuji*

Radiation Protection Dosimetry, 189(4), p.489 - 496, 2020/05

AA2019-0343.pdf:0.67MB

 Times Cited Count:1 Percentile:12.47(Environmental Sciences)

It is important for radiation protection in diagnostic nuclear medicine to estimate organ absorbed doses in consideration of person-specific parameters. This study proposes a straightforward method for estimating organ doses which reflect an individual organ masses by scaling the reference doses based on the reference human models using the inverse ratio of the individual masses to the reference organ masses. The method was tested for the administration cases of $$^{rm 99m}$$Tc-labelled colloids and $$^{123}$$I-labelled sodium iodine to confirm the effectiveness of the method. The discrepancies of the doses estimated by the method were sufficiently small in terms of solid organs.

Journal Articles

Development of a function calculating internal dose coefficients based on ICRP 2007 Recommendations

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

BIO Web of Conferences (Internet), 14, p.03011_1 - 03011_2, 2019/05

 Times Cited Count:0 Percentile:0.21

Dose coefficients, which are committed effective dose per unit intake of radionuclides, are fundamental amounts for dose estimation and protection standards against internal exposures. In this study, we built a calculation function of dose coefficients using the latest dosimetric models and data as a part of development of internal dosimetry code in accordance with 2007 Recommendations of the International Commission of Radiological Protection (ICRP). Quality of the function was assured by comparing the results generated by the function to values recorded in a database of dose coefficients for workers provided by ICRP. In the presentation, we will report the results of quality assurance and the future plans of code development.

Journal Articles

Estimating internal dose coefficients of short-lived radionuclides in accordance with ICRP 2007 Recommendations

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

Journal of Nuclear Science and Technology, 56(5), p.385 - 393, 2019/05

 Times Cited Count:3 Percentile:32.21(Nuclear Science & Technology)

At high energy accelerator facilities, various radionuclides are produced by nuclear reactions of high energy particles with structure and/or ambient air of the facilities. Consequently, the radionuclides are potential sources of internal exposure for works of the facilities. However, the International Commission on Radiological Protection (ICRP) do not provide dose coefficients, which are committed effective doses per intake, for the short-lived radionuclides whose half-lives are shorter than 10 minutes in accordance with the ICRP 2007 Recommendations. Then, we estimated the dose coefficients for inhalation and ingestion of these short-lived radionuclides in accordance with the ICRP 2007 Recommendations. In addition, we compared the dose coefficients with those in accordance with the ICRP 1990 Recommendations. As a result, a decreasing tendency was shown in the dose coefficients for inhalation cases; an increasing tendency was observed in those for ingestion cases. It was found that these changes in dose coefficients were mainly caused by the revision of the dose calculation procedures, alimentary tract models. The result of this study will be useful for planning of radiation protection at the high energy facilities.

Journal Articles

Development of a stochastic biokinetic method and its application to internal dose estimation for insoluble cesium-bearing particles

Manabe, Kentaro; Matsumoto, Masaki*

Journal of Nuclear Science and Technology, 56(1), p.78 - 86, 2019/01

 Times Cited Count:6 Percentile:62.49(Nuclear Science & Technology)

If an insoluble cesium-bearing particle is incorporated into the human body, the radioactivity will move as a single particle. In this case, it is impossible to estimate the number of disintegrations by considering the average behavior of countless nuclei. Then, a method was developed to simulate the behavior of the particle stochastically; and a biokinetic model was constructed to consider the characteristics of insoluble particles. Combination of the method and the model enables to estimate the number of disintegrations, and consequently the internal doses considering the stochastic behavior of the single cesium particle. We evaluated a probability density function of committed equivalent and effective doses and its 99th percentile value and arithmetic mean by repeating the above described procedure, and compared them to the reference values based on the existing models. As a result, the 99th percentile value of committed effective doses was 70 times the reference value when the number of incorporated particles was one, and consequently the dose level was quite low. When the exposure level is 1 mSv in committed effective dose, the uncertainty originating in the insolubility of cesium particles was negligibly small.

Journal Articles

Impressions of Health Physics Seminar 2016

Manabe, Kentaro

Hoken Butsuri, 52(1), p.35 - 38, 2017/03

Health Physics Seminar 2016 was held at the Osaka Science & Technology Center with 150 participants on Nov. 2, 2016. The seminar was consisted of three themes: "current movements of protection and operational quantities", "future risk communications inspired by the Fukushima accident", and "effects of low dose radiation on human". Eminent specialists gave lectures about the news in their particular fields and suggestions to problems. In addition, a special lecture entitled "recent movements of issues about Act on Prevention of Radiation Hazards due to Radioisotopes, etc." was given by a specialist of the Secretariat of Nuclear Regulation Authority. This lecture introduced the examples of trouble incidents, reports on implementation status of inspections, results of Integrated Regulatory Review Service by IAEA, etc. There were vigorous questioning and discussions through the seminar. This document reported the summary of the lectures and discussions, and the author's impressions of the seminar.

JAEA Reports

Assessment of specific absorbed fractions for photons and electrons using average adult Japanese female phantom

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

JAEA-Data/Code 2016-013, 48 Pages, 2016/12

JAEA-Data-Code-2016-013.pdf:1.3MB
JAEA-Data-Code-2016-013-appendix(CD-ROM).zip:0.47MB

In the 2007 Recommendations of the International Commission on Radiological Protection (ICRP), an effective dose is defined as a sum of equivalent doses which are calculated by using male and female reference phantoms based on Caucasian physiological data and averaged over the sexes by tissue weighting factors. Specific absorbed fractions (SAFs), which are essential for internal dosimetry, depend on the body weight and organ masses of phantoms. Then, the dose coefficients, which are committed effective doses per unit intake of radionuclides, developed by ICRP on the basis of the 2007 Recommendations reflect the physical characteristics of Caucasians and are averaged over the sexes. Meanwhile, the physiques of adult Japanese are generally smaller than those of adult Caucasians, and organ masses are also different from each other. Knowledge of the influence of race differences on dose coefficients is important to apply the sex averaged dose coefficients of ICRP to the Japanese system of radiation protection. In this study, SAFs for 25 kinds of mono-energetic electrons and photons ranging from 10 keV to 10 MeV were calculated about the combinations of 67 source regions and 42 target organs using the average adult Japanese female phantom, JF-103, incorporated with a general purpose radiation transport code, MCNPX 2.6.0. The data of this report and the previously published data of JM-103 are applicable to evaluate sex-specific and sex-averaged dose coefficients reflecting the physical characteristics of the average adult Japanese for intakes of all radionuclides not to emit other than photons and electrons.

JAEA Reports

Assessment of specific absorbed fractions for photons and electrons using average adult Japanese male phantom

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

JAEA-Data/Code 2014-017, 60 Pages, 2014/10

JAEA-Data-Code-2014-017.pdf:15.4MB
JAEA-Data-Code-2014-017-appendix(CD-ROM).zip:0.62MB

International Commission on Radiological Protection (ICRP) determined reference phantoms based on physique and organ masses (physical characteristics) of Caucasian for dose assessment in the 2007 Recommendations. In internal dosimetry, the reference phantoms are used for calculation of specific absorbed fractions (SAFs). On the other hand, adult Japanese have smaller build than adult Caucasian, and organ masses are different from each other. SAFs depend on physical characteristics. Therefore, differences in physical characteristics between both races can influence dose coefficients. Then, SAFs of average adult Japanese male phantom, JM-103, were calculated by incorporating JM-103 into the general purpose radiation transport code, MCNPX2.6.0, and electron and photon SAFs were evaluated for 25 energies from 10 keV to 10 MeV and for combinations of 67 source regions and 41 target organs. The effect of the difference in build and organ masses between adult Japanese and Caucasian on SAFs was also examined by comparison between the calculated SAFs in this study and SAFs of the reference adult male phantom of ICRP. The SAFs of JM-103 calculated in this study are basic data for assessment of influence of difference in physical characteristics between the races on dose coefficients.

Journal Articles

Microdosimetric analysis confirms similar biological effectiveness of external exposure to $$gamma$$-rays and internal exposure to $$^{137}$$Cs, $$^{134}$$Cs, and $$^{131}$$I

Sato, Tatsuhiko; Manabe, Kentaro; Hamada, Nobuyuki*

PLOS ONE (Internet), 9(6), p.e99831_1 - e99831_10, 2014/06

 Times Cited Count:7 Percentile:33.82(Multidisciplinary Sciences)

The RBEs of the internal exposure to $$^{137}$$Cs, $$^{134}$$Cs and $$^{131}I$$ were evaluated on the basis of the microdosimetric analysis.

Journal Articles

Comparison of internal doses calculated using the specific absorbed fractions of the average adult Japanese male phantom with those of the reference computational phantom-adult male of ICRP publication 110

Manabe, Kentaro; Sato, Kaoru; Endo, Akira

Physics in Medicine & Biology, 59(5), p.1255 - 1270, 2014/03

 Times Cited Count:5 Percentile:24.58(Engineering, Biomedical)

The International Commission on Radiological Protection (ICRP) decided to use reference phantoms based on physical characteristics of basic Caucasian in evaluation of effective doses in the ICRP 2007 Recommendations. Specific absorbed fractions (SAFs), which are essential data for internal dosimetry, depend on physical characteristics of a phantom used in calculating the SAFs. The body size and amount of adipose tissue of adult Japanese are generally smaller than that of Caucasian. Then, we studied the effects of differences in physical characteristics on internal doses. The electron and photon SAFs of the average adult Japanese male phantom (JM-103) were calculated with the Monte Carlo method, MCNPX. The electron SAFs of the ICRP reference computational phantom-adult male (RCP-AM) were taken from published data. The photon SAFs of the RCP-AM were calculated in the same way as JM-103. Then, the values corresponding to effective dose coefficients for intakes of radionuclides were calculated using the SAFs of these phantoms. As a result of a comparison for 2894 cases of 923 radionuclides, the maximum discrepancy in the effective dose coefficients between the JM-103 and RCP-AM was about 40%. However, the discrepancies were smaller than 10% in 97% of all cases. Information obtained in this study is helpful in applying the dose coefficients of the ICRP to races other than Caucasian.

Journal Articles

Application of average adult Japanese voxel phantoms to evaluation of photon specific absorbed fractions

Sato, Kaoru; Manabe, Kentaro; Endo, Akira

Radioisotopes, 61(6), p.315 - 320, 2012/06

Average adult Japanese male (JM-103) and female (JF-103) voxel phantoms have been developed by modifying the previously constructed JM and JF phantoms at JAEA. The phantoms have the following new features: (1) The heights and weights were adjusted to the Japanese averages; (2) The organ and tissue masses were adjusted to the Japanese averages within 10%; (3) Several organs and tissues were newly modeled for dose assessments based on tissue weighting factors of the 2007 Recommendations of ICRP. Photon SAFs of JM-103 and JF-103 phantoms were calculated, and were compared with those of other adult Japanese phantoms developed at JAEA. It was found that SAFs calculated using these phantoms were strongly dependent on the ogan masses. Therefore, it was concluded that SAFs of JM-103 and JF-103 represent those of average adult Japanese and that the two phantoms are applied to dose assessment for adult Japanese on the basis of the 2007 Recommendations.

Journal Articles

Impact of a revision of nuclear decay data on internal dose coefficients for workers

Manabe, Kentaro; Endo, Akira

Radioisotopes, 60(9), p.375 - 384, 2011/09

The impact of revisions of nuclear decay data on internal dose coefficients for workers was studied using revised data of ICRP Publication 107 (ICRP107) and existing data of ICRP Publication 38 (ICRP38). At first, two sets of ingestion dose coefficients for workers based on ICRP107 and ICRP38 were calculated using the dose and risk calculation software DCAL for 876 chemical forms of 774 nuclides. Ingestion dose coefficients based on ICRP107 increased by over 10% compared with those based on ICRP38 in 61 chemical forms, and decreased by over 10% in 28 chemical forms. It was revealed that the differences in ingestion dose coefficients mainly originated from the revision of energy data as is the case in inhalation dose coefficients. And, the revisions of the proportion of energy of electrons to that of photons, decay modes and half-lives also resulted in changes in the dose coefficients. Then, the extent and causes of changes in ingestion and inhalation dose coefficients were also compared with each other in light of our previous work concerning inhalation dose coefficients. As a result of comparing the dose coefficients for ingestion and inhalation, it was found that the change in proportion of energy of electrons to that of photons impacted on dose coefficients in ingestion more significantly than in inhalation. On the other hand, the change in shape of $$beta$$ energy spectrum, which was one of the causes of change in inhalation dose coefficients, did not impact on ingestion dose coefficients.

JAEA Reports

Calculation of dose coefficients and concentration limits based on tissue weighting factors, et al. revised in the ICRP 2007 Recommendations (Contract research)

Manabe, Kentaro; Endo, Akira

JAEA-Data/Code 2010-020, 148 Pages, 2010/11

JAEA-Data-Code-2010-020.pdf:1.57MB
JAEA-Data-Code-2010-020(errata).pdf:0.11MB

The dose coefficients and concentration limits provided by laws and their relevant public notices in Japan are based on the 1990 Recommendations of the International Commission on Radiological Protection (ICRP). In 2007, the ICRP published the new Recommendations which supersede the 1990 Recommendations. The 2007 Recommendations update tissue and radiation weighting factors to estimate equivalent and effective doses. Therefore, it is important to clarify the impact of these revisions on dose coefficients et al. in adopting the 2007 Recommendations for the system of radiation protection. In this study, dose coefficients et al. have been calculated using the revised tissue weighting factors and compared with those based on the 1990 Recommendations. For most nuclides, the dose coefficients calculated using weighting factors of the 2007 Recommendations decrease for inhalation and remain the same for ingestion. It was identified that the difference in dose coefficients is mainly due to the change in the procedure for calculating equivalent dose rather than the update of the weighting factors.

Journal Articles

Influence of water concentrations to chemical forms of tritium generated in mercury through a nuclear reaction

Manabe, Kentaro; Yokoyama, Sumi

Applied Radiation and Isotopes, 68(3), p.418 - 421, 2010/03

 Times Cited Count:0 Percentile:0.01(Chemistry, Inorganic & Nuclear)

Influence of water content to chemical forms of tritium generated in mercury was evaluated for assessment of potential internal exposure in the Japan Spallation Neutron Source (JSNS) using a mercury target. In order to simulate the condition of tritium production in the mercury target, mercury samples containing a small amount of metallic lithium as a source of tritium and water were irradiated with a thermal neutron beam. It was found that the ratio of HTO to the sum of HTO and HT increased with the water content in the mercury samples.

Journal Articles

Impact of the new nuclear decay data of ICRP Publication 107 on inhalation dose coefficients for workers

Manabe, Kentaro; Endo, Akira; Eckerman, K. F.*

Radiation Protection Dosimetry, 138(3), p.245 - 250, 2010/03

 Times Cited Count:1 Percentile:10.01(Environmental Sciences)

The impact a revision of nuclear decay data had on dose coefficients was studied using data newly published in ICRP Publication 107 (ICRP107) and existing data from ICRP Publication 38 (ICRP38). Committed effective dose coefficients for occupational inhalation of radionuclides were calculated using two sets of decay data with the Dose and Risk Calculation software DCAL for 90 elements, 774 nuclides, 1572 cases. The dose coefficients based on ICRP107 increased by over 10% to those based on ICRP38 in 98 cases, and decreased by over 10% in 54 cases. It was found that the differences in dose coefficients mainly originated from the radiation energy emitted per nuclear transformation having revised. In addition, revisions of the half-lives, radiation types and decay modes also resulted in changes in the dose coefficients.

JAEA Reports

Research on release of tritium and iodine formed in mercury to gas-phase

Yokoyama, Sumi; Manabe, Kentaro

JAEA-Research 2008-057, 29 Pages, 2008/06

JAEA-Research-2008-057.pdf:3.24MB

At Material and Life Science facility of J-PARC, a mercury target as spallation neutron source is used. In the mercury target, airborne radionuclides such as tritium and iodine are formed by spallation reaction with high energy and intensity proton beam. There is possibility that the airborne radionuclides leaked from the target vessel to the air of the facilities may cause internal exposure. However, there is insufficient information about these chemical forms and behavior in mercury to estimate internal doses. We clarified chemical forms and release rates of tritium and iodine from mercury by experiments and discussed from the viewpoint of internal radiation protection. In this study, we found that most tritium formed in mercury is released to the gas-phase as HTO, while iodine is not released under the condition of gas phase in the mercury target.

Journal Articles

Ratio of tritiated water and hydrogen generated in mercury through a nuclear reaction

Manabe, Kentaro; Yokoyama, Sumi

Applied Radiation and Isotopes, 66(2), p.122 - 125, 2008/02

 Times Cited Count:1 Percentile:10.12(Chemistry, Inorganic & Nuclear)

Tritium will be generated in a mercury target of a spallation neutron source in accelerator facilities. The air in the facilities may be contaminated by tritium when tritium leaks to the air from the target. The chemical form of tritium is necessary information to estimate internal doses because the dose coefficient of tritium extremely depends on its chemical form. We simulated the tritium generation in a mercury target by thermal neutron irradiation of liquid lithium amalgam to examine the ratio of tritiated water (HTO) and tritiated hydrogen (HT). The ratio of HTO and HT generated in lithium amalgam was 4:6 under this experimental condition.

Journal Articles

Ratio of aerosol and gases of radioactive chlorine and particle size distribution of aerosol formed by high-energy proton irradiation

Yokoyama, Sumi; Sato, Kaoru; Manabe, Kentaro; Noguchi, Hiroshi; Kaneko, Hirohisa; Oki, Yuichi*; Iida, Takao*; Tanaka, Susumu*

Radiation Protection Dosimetry, 127(1-4), p.392 - 397, 2007/11

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

To estimate internal doses due to the inhalation of radionuclides produced by the nuclear spallation of the air nuclei in high-energy proton accelerator facilities, the physicochemical properties of radionuclides are very important. However, there is not enough information of the properties for airborne radioactive chlorine formed from argon gas in the air of a high-energy proton irradiation field. Thus we have measured the ratio of aerosol and gases of radioactive chlorine which are formed by irradiating argon gas-added air with a 48 MeV proton beam. In addition, the particle size distribution and chemical form of non-radioactive aerosol were examined. It was found that Cl-38 and Cl-39 exist as aerosol, acidic and non-acidic gases. The percentages of Cl-38 and Cl-39 aerosols are more than 70%. In total radioactive chlorine gas, about 30% and 70% are acidic and non-acidic gases, respectively. The concentration of non-radioactive aerosol had a peak at an aerodynamic diameter of 20-30 nm in the early irradiation period. The particle size of non-radioactive aerosol shifted to larger with time. After 10 min, the aerosols grew very slowly and many of the non-radioactive aerosols were distributed widely under 200 nm. This suggests that the diameter of the radioactive chlorine aerosol formed by the attachment of the radioactive chlorine to the non-radioactive aerosol around a beam line of the accelerator is much smaller than the default value adopted in ICRP Publication 66.

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