Global environmental transfer of 129I

Abstract

129I is released to the environment via natural production due to cosmic interaction in the upper atmosphere; past nuclear weapon tests and routine releases from nuclear power plants (NPP) and fuel reprocessing plants (FRP). In this study, a compartmental model is used to estimate the transfer of 129I through various environmental segments like ocean atmosphere, land atmosphere, terrestrial biosphere, ocean mixed layer, surface soil, deep ocean, ocean sediment, shallow subsurface soil and deep subsurface soil due to its release in any one or more compartments. Due to NPP and FRP releases into the land atmosphere for a period of 1000y, the highest inventory of 129I is observed in the surface soil up to a period of 3000y; afterwards the deep ocean shows the highest inventory. The lowest inventory is found in the ocean sediment up to a period of 200y; followed by the ocean atmosphere up to a period of 1250y; afterwards the land atmosphere shows the lowest inventory. The maximum annual effective dose to the world population due to releases of 129I from NPP and FRP for a period of 100y is estimated as 4.14×10−6mSv/y. If the release period is 1000y, the annual effective dose increases to 1.05×10−5mSv/y and for an infinite period of release, it is estimated as 1.5×10−4mSv/y. The model results are verified by comparing the effective dose per TBq release of 129I at different time periods with those reported by different international agencies and good matching is observed among the values.