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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

Internal doses from radionuclides and their health effects following the Fukushima accident

Ishikawa, Tetsuo*; Matsumoto, Masaki*; Sato, Tatsuhiko; Yamaguchi, Ichiro*; Kai, Michiaki*

Journal of Radiological Protection, 38(4), p.1253 - 1268, 2018/12

 Times Cited Count:7 Percentile:58.44(Environmental Sciences)

The current knowledge on internal dose estimation and its health effect were reviewed in this paper. The goals were to discuss the uncertainty of current dose coefficients, to compare the effects of external and internal exposures, and to review recent epidemiological studies. Radionuclides focused on in this study were caesium-137 ($$^{137}$$Cs), caesium-134 ($$^{134}$$Cs), and iodine-131 ($$^{131}$$I), which primarily contributed to internal effective thyroid doses after the Fukushima Dai-ichi Nuclear Power Station accident. Current knowledge suggests that the risk of internal exposure could be generally the same as or less than that of external exposure, when they are compared at the same effective dose.

JAEA Reports

Development of accident diagnosis and prediction system for research reactor; A Pilot system of early fault detection expert system to reduce scram frequency

Yokobayashi, Masao; Matsumoto, Kiyoshi; Murayama, Yoji; Kaminaga, Masanori; Kosaka, Atsuo

JAERI-M 90-207, 26 Pages, 1990/11

JAERI-M-90-207.pdf:0.58MB

no abstracts in English

JAEA Reports

IDAS-RR, an Incident data base system for research reactors; Users manual

Matsumoto, Kiyoshi; Kosaka, Atsuo; Kaminaga, Masanori; Murayama, Yoji; Onishi, Nobuaki; *

JAERI-M 90-055, 232 Pages, 1990/03

JAERI-M-90-055.pdf:5.32MB

no abstracts in English

Oral presentation

Modeling of internal dose from an insoluble cesium

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

If an insoluble particle bearing radioactive cesium is incorporated into the human body, the radioactive nuclei included in the particle will move as a single particulate material without being distributed throughout the body by dissolving to blood or tissue fluid like soluble cesium. Because commonly applied methods for estimation of the numbers of decays are designed for the average behavior of large number of nuclei, the existing methods cannot be applied for insoluble cesium particles. In this study, we developed a method simulating a stochastic movement of a single particle in the body, and constructed an improved biokinetic model for insoluble particles. This method enables to estimate the numbers of decays considering the stochastic movement of the particle, and organ absorbed doses by combining the numbers of decays and corresponding S values. Repetitive execution of this procedure makes it possible to evaluate a probability density function of exposure dose.

Oral presentation

Internal dose estimation considering the characteristics of insoluble caesium-bearing particles

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

If an insoluble cesium-bearing particle is incorporated into the body, the radioactivity in the particle will move stochastically in the state of a cluster without diffusion to the blood or tissue fluid. A deterministic method is applied to estimate internal doses for generic radioactive aerosols, but the deterministic method cannot be applicable to insoluble cesium-bearing particles. We established a stochastic method to estimate probability density functions of internal doses for intakes of insoluble particles by simulating the stochastic behavior of the particles. In this presentation, we will show the result of the probability density function of doses for particles having a typical size (diameter: 2 $$mu$$m). In addition, we will describe the parameters that affect probability density functions of doses, and future issues.

Oral presentation

Internal dose estimation for inhalation of insoluble particles

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

It is expected that radioactivity included in matrix of an insoluble particle incorporated into the body will move stochastically as a single particulate material without dissolving to blood or tissue fluid. Therefore, a deterministic dosimetric method which is commonly used and is designed for the average behavior of large number of nuclei cannot be applied for estimation of uncertainty of internal doses depending on the stochastic movements of insoluble particles. The authors developed a method simulating a stochastic movement of insoluble materials inhaled into the body, and this method enables to estimate the probability density function (PDF) of internal doses from the particles. In this presentation, results and interpretation of PDFs will be reported in case of inhalation of typical insoluble cesium bearing particles. In addition, the difference will also be discussed between the pdf and a dose estimated by a commonly used method.

Oral presentation

Particle diameter dependence of internal doses due to inhalation of insoluble cesium particles

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

When an insoluble cesium-bearing particle which has high specific activity is inhaled into the human body, the activity will move stochastically in the state of a sphere without dissolving in the blood or tissue fluid. We have developed a stochastic biokinetic method to evaluate the stochastic behavior of the particle in the body and estimated the probability distribution of exposure doses from a typical cesium-bearing particle whose diameter is 2 $$mu$$m. In this study, we analyzed particle diameter dependence of dose distribution due to inhalation of the particle with considering that the activity in a particle and the deposition probability to the regions of the respiratory tract change with the diameter. As a result, the maximal values of 99%ile values and arithmetic means were observed at 3.0 $$mu$$m and 3.5 $$mu$$m, respectively.

Oral presentation

Features of internal exposure to insoluble particles having high specific activity

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

Insoluble particles containing high specific activity of cesium were found after the accident of TEPCO's Fukushima Daiichi Nuclear Power Station. It is expected that activities in the particle will not dissolve into blood or tissue fluid due to the insolubility and will move in the body as a single particulate material when the particle is inhaled. Therefore, internal doses due to the particle inhalation depend on the stochastic path of the particle in the body. An existing methodology for internal dose estimation is not designed for the case that the doses depend on the individual path. The authors developed a stochastic biokinetic method to estimate the internal doses due to the particle. This method enables to obtain a probability density function of the doses. This presentation reviews the outline of the SB method, and the topics and ongoing tasks regarding internal dose estimation for intake of insoluble particles.

Oral presentation

Internal dose estimation for inhalation of CsMP

Manabe, Kentaro; Matsumoto, Masaki*

no journal, , 

When insoluble particles containing radiocesium, CsMP, are incorporated into the body, the radioactivity contained in CsMP does not dissolve in blood or tissue fluid, but migrates through the body in particle form. Since the kinetic behavior of CsMPs in the body is stochastic, the internal dose due to CsMPs is expected to depend on the migration path and to have uncertainty. Therefore, we developed a dose estimation method that simulates the stochastic behavior of insoluble particles such as CsMPs, and evaluated the probability distribution of the effective internal dose due to inhalation of a typical CsMP with a particle size of 2 $$mu$$m. As a result, the ratio of the 99th percentile value to the arithmetic mean of the effective dose distribution for the inhalation of one CsMP was found to be 19, with a very large uncertainty. However, the uncertainty decreased with the increment of the number of simultaneously inhaled CsMPs, and the arithmetic mean of the effective dose was found to be 0.12 mSv and the ratio 1.6 for 10$$^{3}$$ CsMPs inhaled at the same time.

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