Environmental radiation at the EBR-II site

The present environmental radiation state of the EBR-II site has been explored through application of new and highly sensitive methods which have resolved the environmental gamma and meson components at this highly relevant LMFBR site. The external gamma-ray radiation dose rate in the immediate vicinity of EBR-II (for gamma rays of energy in excess of 220 keV) was observed to be about 6 μrad/hr. The cosmic-ray meson component contributes an additional dose rate of about 4.5 μrad/hr. These two components result in an annual external dose to man of approximately 92 mrads. Although analysis of the gamma-ray spectra and soil samples reveals that the gamma-ray component is overwhelmingly derived from naturally occurring isotopes, statistically significant amounts of 137Cs and 125Sb (fission products). were observed in soil samples collected during this site survey. In addition, sizeable variations in the observed concentrations of 125Sb, 137Cs, 238Pu, and 239Pu of these EBR-II soil samples would appear to imply a non-uniform deposition pattern. However, the observed non-uniformity could be due to either local releases of fission products or drifting of surface soil containing fallout products. While fallout is certainly a significant contribution to the measured deposition, observed patterns and correlations qualitatively suggest that very low level releases could possibly have occurred at the EBR-II site some time in the past. Quantitative conclusions cannot possibly be based upon the very limited data available from the present site survey.