Assessing Exposure to the Public from Low-Level Radioactive Waste Truck Transportation in the United States to the Nevada Test Site

The U.S. Department of Energy’s (USDOE) Nevada Test Site (NTS) is one of two regional sites in the United States where low-level radioactive waste (LLW) from approved USDOE and U.S. Department of Defense generators is disposed by shallow land burial. In fiscal year 2003, when most of the data for this study was collected, more than 91,000 m3 of LLW were transported by truck to the NTS. USDOE and U.S. Department of Transportation (USDOT) regulations ensure that radiation exposure from truck shipments is negligible. Nevertheless, particularly in rural communities, there is perceived public risk regarding cumulative exposure, especially where LLW transportation routes and main highways running through towns are one and the same. To address the issue of cumulative exposure, a stationary and automated array of four Reuter-Stokes, Model RSS-131, high-pressure ion chambers (PICs) was set up to monitor trucks transporting LLW before entering the NTS. PICs were positioned 1 m from the truck trailer at a height of 1.52 m to simulate conditions where exposure to a human being standing next to a truck carrying LLW is representative of the exposure to the chest area for a “Reference Man” [1]. The four PICs (two on each side of the vehicle pullout area) were used to investigate nonuniformity in the wasteload, which occurs when levels of gamma radiation from waste packages varies from side to side and from front to back in the truck trailer. Each PIC was calibrated both at the field site and in the laboratory to a source known to contain 189.2 μCi of 137Cs.