Radiation Dose to Small Mammals Inhabiting a Solid Radioactive Waste Disposal Area

Abstract

(1) Radiation dose rates received by deer mice (Peromyscus maniculatus (Wagner)) and Ord's kangaroo rats (Dipodomys ordii (Woodhouse) inhabiting a solid radioactive waste disposal area and a control area in south-eastern Idaho were determined by surgically implanting lithium-floride thermoluminescent dosimeter (TLD) packets. Fifty-three percent of the 542 and 135 TLD packets implanted in deer mice and kangaroo rats, respectively, were recovered. (2) The radiation dose rates received by animals from the radioactive waste disposal area varied from 4 to 418 000 gGy day-' (0-4-42 000 mrad day-') and were significantly (P < 0.01) higher than the dose rate of 4 gGy day-' (0-4 mrad day-') received by control animals. Doses resulted primarily from radiation from buried activation and fission products and not from radionuclides in/on tissues. (3) Ninety-six percent of the waste disposal area deer mice in the autumn-winter had radiation dose rates higher than the rates of the control animals, whereas in the spring-summer 73% of the deer mice received dose rates greater than the rates of control animals. Differences in seasonal data were probably related to increased subsurface time in autumn-winter. (4) Autumn-winter dose rates received by kangaroo rats were significantly (P < 0.05) higher than spring-summer rates and were attributed to the species entering torpor beneath the soil surface during winter. (5) Conservative comparisons between the radiation dose rates received by implanted TLD packets in individual small mammals and the potential dose rates received by individual animals on the surface of the area indicated a minimum of 49 and 20% of the deer mice and kangaroo rat populations, respectively, encountered areas of buried activation and fission waste and/or contaminated soil. (6) Data obtained provided an indirect method of measuring biological intrusion into soil covers over solid low-level radioactive waste disposal areas.