Major Sources of Tritium in the Environment and Radiation Dose Assessment Result Survey Caused by the Discharge of Tritium

Abstract

[Introduction] Tritium is a radioactive isotope of hydrogen. It is one of the radionuclides that is released into the environment from nuclear facilities. However, establishing separation techniques to quantify such radionuclides is difficult. The tsunami that occurred following the March 11. 2011 Great East Japan Earthquake damaged the Tokyo Electric Power Company Fukushima power plant. Tritiated water has continued to accumulate at the power plant site. Appropriate processing methods for this tritiated water are also problematic. It is very concerned about tritium.

This study focuses on the nature and behavior of tritium in the environment and its influence on the human body. The objective is to improve scientific expertise related to tritium.

[Major sources of tritium in the environment]

Tritium occurs naturally in the environment. Other sources of tritium in the environment are nuclear weapons testing, nuclear facilities, medical and industrial applications, and scientific research. In this study, tritium of nuclear experiment origin, the largest contribution among them, and the tritium due to the nuclear facility that has been growing current interest was investigated and was organized the contents.

[Tritium dose assessment results survey] Tritium dose assessment survey focused on tritium from artificial origins. The results were compared and discussed. Given assumed conditions and the focus on the influence on the human body, the numerical value of the dose was compared. The following sources of tritium were assessed:

・Nuclear weapons testing (atmospheric nuclear weapons testing)

・Nuclear power plant (under normal conditions)

・Rokkasho reprocessing facility (under normal conditions)

・Sellafield reprocessing facility (under normal conditions)

・Chernobyl nuclear power plant accident

・Tokyo Electric Power Company Fukushima nuclear power plant accident

The global average annual effective dose of tritium from nuclear weapons testing is approximately 10 μSv / year at most; the impact on people is very small. The concentration of tritium in stagnant water at the Tokyo Electric Power Company Fukushima nuclear power plant was surveyed in published reports. In addition, exposure dose of the general adult public who drinks tritiated water of the regulated concentration limits over a period of one year was calculated. The calculated result was 6.5×10² μSv / year, which is less than the effective dose limit of 1 mSv / year prescribed by Japanese law. The influence of tritium from the other sources was also confirmed to be sufficiently low.