2014 Volume 3 Issue 2 Pages 54-55
Introduction
Anthropogenic radionuclides of plutonium (Pu) have been released into the environment because of atmospheric nuclear weapons testing. In addition, Pu can be used as fuel after reprocessing the spent nuclear fuel. Therefore, Japan plans to reprocess nuclear fuel; hence, it is important to investigate the behavior of Pu in the environment. The purpose of this study was to review the existing literature related to the fate of Pu in the environment and to estimate the internal exposure dose of residents living near the Sellafield reprocessing plant. In particular, the study focused on internal radiation exposure based on the consumption of seafood.
Sources of Pu in the environment
The principal source of Pu in the environment is the fallout caused by atmospheric nuclear weapons testing. Pu can be released from other sources including nuclear fuel reprocessing plants, falling satellites, accidents during nuclear weapon transportation, and during nuclear facilities accidents. Pu has been distributed throughout the world because of atmospheric nuclear testing. Other sources have a more localized affect and can be distinguished according to the differences of 240Pu/239Pu atom ratios.
Estimating internal radiation dose from the Sellafield reprocessing plant
The Sellafield site consists of various nuclear facilities that have discharged radioactive materials into the Irish Sea since the 1950s. Discharge of Pu from reprocessing plant operations and the total discharge amounts of 239, 240Pu and 238Pu were 587 TBq and 144 TBq, respectively. The environmental monitoring of radionuclide levels around the Sellafield reprocessing plant was performed by a U.K. government agency. The present study estimates the internal exposure dose of residents by determining Pu concentrations in seafood and the average yearly seafood consumption of residents. Figure 1 shows that the internal radiation dose from Pu was up to 10 mSv in the late 1970s, which was approximately 1/10 lower than the internal radiation dose from 137Cs. Moreover, the global average dose was 290 mSv. Thus, the internal radiation dose from Pu near the Sellafield reprocessing plant was considerably lower than that from other sources such as 137Cs and the global average.
