Assessing Potential Exposure from Truck Transport of Low-level Radioactive Waste to the Nevada Test Site

This study has shown that, based upon measurements from industry standard radiation detection instruments, such as the RS model RSS-131 PICs in a controlled configuration, a person may be exposed to gamma radiation above background when in close proximity to some LLW trucks. However, in approximately half (47.7 percent) the population of trucks measured in this study, a person would receive no exposure above background at a distance of 1.0 m (3.3 ft) away from a LLW truck. An additional 206 trucks had net exposures greater than zero, but equal to or less than 1 (micro)R/h. Finally, nearly 80 percent of the population of trucks (802 of 1,012) had net exposures less than or equal to 10 (micro)R/h. Although there are no shipping or exposure standards at 1.0 m (3.3 ft) distance, one relevant point of comparison is the DOT shipping standard of 10 mrem/h at 2.0 m (6.6 ft) distance. Assuming a one-to-one correspondence between Roentgens and Rems, then 903 trucks (89.2 percent of the trucks measured) were no greater than one percent of the DOT standard at 1.0 m (3.3 ft). Had the distance at which the trucks been measured increased to 2.0 m (6.6 ft), the net exposure would be even less because of the increase in distance between the truck and the receptor. However, based on the empirical data from this study, the rate of decrease may be slower than for either a point or line source as was done for previous studies (Gertz, 2001; Davis et al., 2001). The highest net exposure value at 1.0 m (3.3 ft) distance, 11.9 mR/h, came from the only truck with a value greater than 10 mR/h at 1.0 m (3.3 ft) distance