Review of Articles Related to the Accident at Fukushima Daiichi Nuclear Power Station Published in the Japanese Journal of Health Physics: Dosimetry and Dose Assessment (Secondary Publication)

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Abstract

Introduction

The Japanese Journal of Health Physics, the journal of the Japan Health Physics Society, published many articles related to the accident at Tokyo Electric Power Company Incorporated (TEPCO)’s Fukushima Daiichi Nuclear Power Station that occurred in March 2011 [1]. Twenty-three articles were published on dosimetry and dose assessment till March 2022, and the articles are classified into (1) five special articles, (2) one original article, (3) four technical data, (4) four review articles, (5) one report, (6) three topics, and (7) Japan to the World (J to W), including five articles. This review provides an outline of these 23 articles.

Summary of Special Articles

‘On the criteria of protective action for consumption of food and drinking water’ by Inaba [2] described the process of deriving standard values for radioactive iodine and radioactive cesium among the indicators related to food and beverage intake restrictions established by the former Nuclear Safety Commission. Regarding the protective measures taken by the Ministry of Agriculture, Forestry, and Fisheries after the accident, the ministry introduced temporal allowable values of the radioactivity concentration of cesium in paddy field soil during rice planting and in roughage, which was established with cattle as a representative. These allowable values have played a major role in avoiding and reducing radiation exposure. However, it is also true that foods and drinks that contain or may contain radioactive substances cause great anxiety in many people. The article also provides suggestions for future revision.

In ‘Current status and issues of assessment of exposure to the public’ by Takahashi [3], public dose assessment was divided into dose assessment from immediately after the accident up to a certain point (dose reconstruction), dose assessment at the time of investigation, and long-term dose assessment (future prediction). The current situation and issues were described. The article described the development status of the environmental monitoring system and stated that it is important to thoroughly examine the reliability of the measured values and clarify the basis and concept of the derived models and parameters for the estimated values.

‘Results of simplified survey for thyroid internal exposure of children in Fukushima and other surveys’ by Fukushima [4] reported the results of a pediatric thyroid simple measurement survey conducted in Fukushima Prefecture after the accident, an internal radiation exposure examination using a whole-body counter, and an external radiation dose measurement for 1,727 residents of Kawamata Town (Yamakiya District), Namie Town, and Iidate Village.

‘Radiation dose estimation from foods due to the accident of TEPCO Fukushima Daiichi Nuclear Power Station’ by Yamaguchi [5] considered specific examples to explain the method of estimating the committed dose based on data of the radioactive concentration in food. Additionally, dose estimation based on total diet studies and estimation methods based on in vitro measurements and bioassays were introduced.

‘Issues on personal monitoring and dosimetry’ by Takada [6] summarized the problems with precision whole-body counter measurements performed by Tokyo Electric Power Company in cooperation with the Japan Atomic Energy Agency. This measurement was conducted on residents and workers involved in various tasks within the Fukushima Daiichi Nuclear Power Station. Issues regarding the need to standardize internal exposure dose assessments, handle measured data, communicate results to residents, and handle occupational exposure in the event of a disaster were discussed.

Summary of Original Article and Technical Data

‘Dose estimate for incineration and disposal of dehydrated sludge contaminated by radioactive cesium of high activity concentration’ by Takada and Kimura [7] provided technical information to formulate a policy to handle the treatment and burial disposal of sludge containing radioactive cesium. This was an original study that analyzed the doses of workers and the public associated with the treatment and burial disposal of waste and showed that if the concentration of radioactive cesium in sludge or incineration ash is below 8.9 Bq/g, the dose to surrounding residents can be suppressed to 1 mSv per year or less.

The four articles in the category of technical data are summarized below. ‘Committed effective dose from the oral ingestion of radio-tellurium in rice released by the Fukushima Nuclear Power Plant Accident’ by Fujiwara et al. [8] calculated the contribution of radioactive tellurium to internal exposure. The study showed the possibility that the contribution of radioactive tellurium to internal exposure in the period of approximately 1 year after the accident was not negligible relative to that of radioactive cesium.

‘Evaluation of effective dose coefficient with variation of absorption fraction in gastrointestinal system for ingestion of radiocesium’ by Pratama et al. [9] discussed changes in the intestinal absorption coefficient with changes in the ingestion dose coefficient when radioactive cesium was acutely ingested. Furthermore, the authors attempted to provide a simple calculation method for the intestinal absorption rate values for specific ingestion dose coefficients and age groups. It was reported that the intestinal absorption rate decreased significantly in adults when the ingested dose coefficient decreased, whereas no significant change was observed in children.

‘Evaluation of external exposure of workers engaging demolition works near the Fukushima Daiichi Nuclear Power Plants’ by Yamamoto et al. [10] investigated the external exposure of workers engaged in the demolition work of damaged buildings. The article showed that the exposure was the same as or less than the external exposure dose to workers engaged in decontamination work.

In ‘Studies on total beta measurements at Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company with EGS5’ by Hirayama [11], the Monte Carlo calculation code EGS5 was used to examine the total beta radioactivity measurements carried out at Fukushima Daiichi Nuclear Power Station. The article summarized the critical aspects of conducting total beta radioactivity measurements at the Fukushima Daiichi Nuclear Power Station by verifying the measurement results from TEPCO.

Summary of Review Articles

In ‘Application of cost-benefit analysis to the regulation of foodstuffs contaminated with radioactive substances’ by Oka [12], the authors discussed the application of cost-benefit analysis to decision-making in the regulation of food contaminated with radioactive substances. Following the discussion of the limitations of cost-benefit analysis, future challenges and possibilities were discussed. In ‘Radiation protection of workers for decontamination pilot project in contaminated area of Fukushima Prefecture’ by Asano [13], in order to obtain the necessary information to proceed with decontamination work after the accident, the decontamination effects and radiation control associated with the decontamination work were examined in the model area. A more detailed report of this study is available on the website [14]. In the references of this article, the uniform resource locator (URL) information of the original article has been updated. ‘Progress in estimation of dose due to the Fukushima Daiichi Nuclear Power Plant Accident’ by Ishikawa [15] provided an overview of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013 report [16] that reported the doses resulting from the accident at the Fukushima Daiichi Nuclear Power Station. A comparatively recent measurement result, which was not reflected in the UNSCEAR report, was cited, and both results were compared. It was shown that the internal exposure was lower in the recent measurement. ‘Issues behind radiation management of workers at Fukushima Nuclear Power Plant of Tokyo Electric Power Company: from the viewpoint of radiation exposure of the ocular lens and the biological effects to the lens’ by Hayashida et al. [17] discussed the investigation of lens opacification of emergency workers on the site of the Fukushima Daiichi Nuclear Power Station. The article also focused on radiation management of the equivalent dose for the lens of the eye against the background of reviewing the dose limit of the lens, which was a subject of interest when the article was published in 2017.

Summary of Report, Topics, and J to W

‘External dose estimation in an early stage after the Fukushima Daiichi Nuclear Power Plant Accident: lessons learned from behavior surveys using self-administered questionnaires’ by Ishikawa et al. [18] reported on a self-reported basic questionnaire survey of the Fukushima Prefecture Health Management Survey. In the survey, the behaviors during the 4 months after the Fukushima Nuclear Power Station accident were recorded and answered. The article highlighted the problem of computerization of many handwritten questionnaires, the increase in the response rate, and the ways to address such problems.

The three articles [19–21] were all published in conferences on internal exposure. The two articles by Yoshii [19], and by Miyazaki and Ohtsuru [20], are related to conferences held within 1 year after the accident, focusing on measurement methods and operational issues for whole-body counters. The article by Satou [21] discusses the symposium on internal exposure dose assessment held in 2018, focusing on insoluble particles (commonly known as cesium balls).

Three of the five J to W articles [22–24] were reprinted from the ‘Japan Atomic Energy Agency (JAEA) R&D Review,’ which is the annual publication published by JAEA. Two articles addressed the external exposure of residents in Fukushima Prefecture, and one article reported on three-dimensional visualization technology of the radiation contamination situation in the working environment of the Fukushima Daiichi Nuclear Power Station. ‘The internal exposure of the thyroid to radioiodine from the Fukushima Nuclear Accident’ by Sorimachi and Tokonami [25] and ‘Radioactive concentration of food caused by Fukushima Nuclear Power Plant disaster and new radiological standards for foodstuffs in the existing exposure situation in Japan after a severe nuclear accident’ by Yamaguchi [26] were based on the special articles ‘Results of simplified survey for thyroid internal exposure of children in Fukushima and other surveys’ by Fukushima [4] and ‘Radiation dose estimation from foods due to the accident of TEPCO Fukushima Daiichi Nuclear Power Station’ by Yamaguchi [5], respectively, which were also featured in ‘Summary of special articles,’ with additions and reports in English.

Conclusion

This paper presents an overview of 23 articles on dosimetry and dose assessment published in the Japanese Journal of Health Physics till March 2022. The subject of most articles was individual exposure. The social need to determine individual exposure doses in previously unknown situations is apparent. Among individual doses, many studies have focused on public exposure. In the early period after the accident, most articles studied internal exposure. Regarding external exposure, many articles used the collected data to estimate the exposure values at that time. The dosimetry data and dose evaluation methods reported in these articles are valuable for monitoring radiation during accidents in the future.

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