U.S. Department of Energy Development of Unacceptable Radiological Consequence Thresholds for Nuclear and Radiological Materials under the 2016 Design Basis Threat Policy

The United States Department of Energy (DOE) has responsibility under the U.S. Atomic Energy Act for the establishment of policies for the physical protection of nuclear material, other radioactive material, associated facilities, or associated activities under its purview. Protection against radiological sabotage is based on a graded approach, and the DOE’s current policy defines two unacceptable radiological consequence (URC) thresholds, the first a threshold based on potential radiological consequences within the boundary of a nuclear facility, and the second based on potential radiological consequences beyond the boundary of a nuclear facility. A basic premise of the DOE nuclear security effort was that the goal of nuclear terrorism is to cause as much harm as possible, which means the goal of a radiological sabotage act is to cause immediate injuries or death to people rather than subject them to long term chronic health effects. The approach taken by DOE was to develop a trigger dose, defined as both a total dose and a dose rate, based on radiation levels that would cause immediate and acute injuries or death to exposed humans. The development of trigger dose levels allowed the DOE to establish URC thresholds in order to apply graded physical protection against radiological sabotage for nuclear material, other radioactive material, associated facilities, or associated activities. This threshold is used to establish physical protection levels to protect against radiological sabotage acts that have the potential to exceed trigger dose levels for personnel on a nuclear facility, and a threshold for more severe radiological sabotage acts that result in the potential to exceed trigger dose levels to the public beyond the boundaries of a nuclear facility. It also allowed the development of lethal dose tables, an inventory table that lists quantities of radionuclides that, if dispersed at ground level under neutral meteorological conditions, will deliver a potential dose that exceeds trigger dose levels at defined distances. The lethal dose tables allow radioactive material to be screened without consideration of other mitigating factors, if the total quantity does not have the potential to exceed trigger dose levels from an act of radiological sabotage.