Activities to support individual dosimetry of children in Kawamata Town.

This paper does not necessarily reflect the views of the International Commission on Radiological Protection.Kawamata Town in Date District, Fukushima Prefecture is located more than 30 km north-west of Fukushima Daiichi nuclear power plant, but on 22 April 2011, part of the Yamakiya District of Kawamata Town was designated as a planned evacuation area. The exposure of children was a concern in Kawamata Town. Based on the proposal of Kindai University, Kawamata Town Board of Education took the initiative to measure individual radiation doses with an integrated dosimeter (glass badge) for all kindergarten children, nursery school children, elementary school students, and junior high school students in the town. These measurements were continued for nearly 3 years from June 2011 until the end of March 2014. The total number of measurements was approximately 16,800 across 11-cycle measurement, with 3 months' accumulation taken as one-cycle measurement. Kindai University provided financial support for the glass badge measurement service, and cooperated in the analysis of measured values and the development of advice based on the results. The main body implementing the measurements was Kawamata Town Board of Education, and the data obtained belong to Kawamata Town. When measurements were starting to be taken, schools got involved in the collection and distribution of dosimeters after explanations were provided to principals and school nurses who were in charge of risk communication. Thanks to the efforts of the schools, the recovery rate exceeded 90%, increasing the reliability of the measurements. It was clear who needed the information - the children and their parents. Kawamata Town Board of Education summarised the cumulative dose results for each measurement and notified parents via personal reports. These were sent to parents with advice on measurement results prepared by Kindai University, and care was taken to ensure that people could understand the measured results. Further briefing sessions were held as appropriate. At the briefing sessions, at the request of Kawamata Town Board of Education, the faculty members of Kindai University explained the measurement results from a professional point of view, and a professor from the Faculty of Medicine provided individual health consultations. Kawamata Town took the lead in using specialists to gain peace of mind, and this was key to the project's success. The situation was managed by taking measurements by dosimetry, and asking experts to interpret the data and provide advice to help reassure the residents.

Report of the Japan Health Physics Society ad hoc working group for the Plutonium intake accident.

This paper describes an overview of the radiation protection response to the Plutonium intake accident that occurred at the Plutonium Fuel Facility of the Oarai Research and Development Center of the Japan Atomic Energy Agency on 6 June 2017. In the hood of the analyzing room at the Plutonium Fuel Facility five workers were checking a storage container of fast reactor nuclear fuel material. Around 11:15 a.m., vinyl bags inside the fuel material container containing Plutonium and enriched uranium burst during the inspection work. All the workers heard the bang, which caused misty dust leakage from the container. This event caused significant both skin and nasal α-contamination for three workers and just skin α-contamination for one worker. Decontamination was conducted in the shower room. Then the five workers were transferred to the Nuclear Fuel Cycle Engineering Laboratory to evaluate inhalation intake of Plutonium etc in the lungs. The maximum values of 2.2 × 104 Bq for 239Pu and 2.2 × 102 Bq for 241Am were estimated by the lung monitor. Based on these results, injection of a chelate agent was conducted for prompt excretion of Plutonium etc. The next morning, the five workers were transferred to the National Institute of Radiological Sciences for treatment including decontamination of their skin and measurement by a lung monitor. At that time no obvious energy peak was confirmed for Plutonium. The Japan Health Physics Society launched an ad-hoc working group for Plutonium intake accident around the middle of June to survey issues and to extract lessons for radiological protection. The authors, who are the members of the ad-hoc working group, here report the activity of the working group.

Methodology using a portable X-ray fluorescence device for on-site and rapid evaluation of heavy-atom contamination in wounds: a model study for application to plutonium contamination.

Workers decommissioning the Fukushima-Daiichi nuclear power plant damaged from the Great East Japan Earthquake and resulting tsunami are at risk of injury with possible contamination from radioactive heavy atoms including actinides, such as plutonium. We propose a new methodology for on-site and rapid evaluation of heavy-atom contamination in wounds using a portable X-ray fluorescence (XRF) device. In the present study, stable lead was used as the model contaminant substitute for radioactive heavy atoms. First, the wound model was developed by placing a liquid blood phantom on an epoxy resin wound phantom contaminated with lead. Next, the correlation between the concentration of contaminant and the XRF peak intensity was formulated considering the thickness of blood exiting the wound. Methods to determine the minimum detection limit (MDL) of contaminants at any maximal equivalent dose to the wound by XRF measurement were also established. For example, in this system, at a maximal equivalent dose of 16.5 mSv to the wound and blood thickness of 0.5 mm, the MDL value for lead was 1.2 ppm (3.1 nmol). The radioactivity of 239Pu corresponding to 3.1 nmol is 1.7 kBq, which is lower than the radioactivity of 239Pu contaminating puncture wounds in previous severe accidents. In conclusion, the established methodology could be beneficial for future development of a method to evaluate plutonium contamination in wounds. Highlights: Methodology for evaluation of heavy-atom contamination in a wound was established. A portable X-ray fluorescence device enables on-site, rapid and direct evaluation. This method is expected to be used for evaluation of plutonium contamination in wounds.

Design of an integrating type neutron dose monitor.

It is intended that deuterium-deuterium reaction experiments will be performed for the next phase of the large helical device (LHD) at National Institute for Fusion Science (NIFS), Toki, Japan. To protect workers against radiation, the characteristics of the radiation field at the LHD workplace should be evaluated. The neutron fluence at the workplace was calculated by means of the radiation transportation code. Since the neutron energy distribution at the workplace has a wide energy range, from thermal to fast neutrons, a neutron dose monitor had to be especially designed. The author designed an integrating type neutron dose monitor for this purpose. Since this monitor has good responses for dose evaluation in every energy range, it should be able to evaluate the dose at the LHD workplace accurately.