Possible effects of ionizing radiation upon marine life and some implications of postulated accidental releases of radioactivity

Ionizing radiation will have both somatic and genetic effects upon the exposed populations. Somatic changes, i.e., effects produced directly in the irradiated organism, will result in the death of the irradiated species by a variety of natural mechanisms. Genetic effects, however, are more subtle and may sometimes be viewed as beneficial; however, the benefits accruing to subsequent generations have yet to be demonstrated for marine species.Two models for predicting the impact of radioactivity in the food chain upon man are reviewed here: (a) the critical pathway concept, and (b) the specific activity approach. The specific activity method was used by Aten in 1961 to obtain estimates of the maximum permissible concentrations of biologically important radionuclides in seawater (MPC)s.In an accident situation involving the release of radioactivity from a light-water power reactor to the ocean, the most important radionuclides on the basis of the type of radiations emitted, quantity produced, half-life, and biological significance are the fission products 90Sr, 137Cs, 239Pu, and the activation products 65Zn, 54Fe, and 95Zr.The specific activity approach as applied to three classes of accidental radioactive releases to the sea can be used to determine the sensitive nuclide for each release and to estimate the relative degree of seriousness of each release by calculating the volume of seawater needed to dilute each spill to the (MPC)S of the critical nuclide. Estimates made for three types of accidental releases at sea yield the following data: 1. primary coolant release: 137Cs critical nuclide, 33-km3 dilution volume needed for 101-Ci total release2. shipping cask loss: 90Sr critical nuclide, 66- × 102-km3 dilution volume needed for 107-Ci total release3. core inventory release (75%): 90Sr critical nuclide, 105-km3 dilution volume for 109-Ci total release.It was found that the 104-107-109 total release relation among accidents was not maintained in the dilution to (MPC)s.