Transport of radioactive materials by jackrabbits on the Hanford reservation.

Abstract

A survey was conducted near waste disposal trenches (B-C Cribs), Hanford Reservation, south-central Washington, to learn the extent to which jackrabbits (Lepus californicus) and their predators had dispersed radioactive salts, and to relate these data with parameters, such as topography, wind direction, vegetation types, and animal behavior, that might help explain the pattern of dispersal. Animals had access to the radionuclides for an unknown duration between 1958 and 1964. In 1972–1973, 6671 circular sampling sites (1.4 m2) were surveyed in the vicinity of the B-C Cribs. Radioactive feces, urine, soil, and vegetation were distributed in all directions from the cribs, but the area to the south and southwest was more densely and uniformly contaminated. Of the ultimate sampling units surveyed in 1972, 278 or 10.6% had count rates in excess of 10,000 counts/min measured with a Geiger-Mueller counter (background count rates were less than 500 counts/min). Of these 278 circular areas, 179 or 64% were found within 0.5 km of the cribs, 23.4% were between 0.5 and 1.0 km, and the remaining 12.2% were farther away. Most feces with a count rate greater than 20,000 counts/min was found within 400 m of the cribs, but jackrabbit pellets with count rates in excess of 100,000 counts/min were found up to 1.6 km from the cribs. Assuming a circular dispersal pattern we estimated that radioactive jackrabbit pellets were distributed over 15 km2. Surveys were conducted over 3000 ha and up to 20 km from the cribs to determine whether predators of jackrabbits were also involved in spreading radioactivity. Only four sources of radioactivity associated with predator activities were found (coyote feces; three collections of bone fragments under hawk feeding stations) up to 9.7 km from the cribs. All radioactivity found during this study was well within the boundaries of the Hanford Reservation. The results show how abundant native animals can effectively transport radioactive wastes. The potential for similar occurrences on nuclear installations should be evaluated so that appropriate measures can be taken to minimize the spread of contamination.