Analysis of Metabolism and Effective Half-life for Radiation Workers’ Tritium Intake at Pressurized Heavy Water Reactors

Tritium is the one of the dominant contributors to the workers of Pressurized Heavy Water Reactors’ (PHWRs) internal radiation exposure. This nuclide is likely to be released in work places as tritiated water vapor (HTO) from the primary system and can get relatively easily absorbed into the body of workers by inhalation. Inhaled tritium usually reaches the equilibrium of concentration after approximately 2 hours inside the body and is then excreted from the body with an effective half-life of 10 days. Because the tritium inside the body is transported within the body, the whole body can be exposed to radiation. Internal radiation exposure at PHWRs accounts for approximately 20-40 % of the total radiation exposure, where most of the internal radiation exposure is attributed to tritium. Thus, tritium is an important nuclide that needs to be necessarily monitored for radiation management safety. In this study, metabolism for tritium was established by using its excretion rate results in urine samples of workers at PHWRs. An effective half-life, a key parameter that estimates the radiation exposure, was derived from these results. As a result, it was found that the effective half-life for workers at Korean Nuclear Power Plants (NPPs) was 7.43 2.22 days, which is shorter than that of International Commission on Radiological Protection guides.