Advanced disposal systems for transuranic waste: Preliminary disposal criteria for plutonium-239 at hanford

Abstract

An evaluation of the feasibility and potential application of advanced disposal systems is being conducted for defense transuranic (TRU) wastes at the Hanford site. The advanced waste disposal options include those developed to provide “greater confinement” than provided by shallow-land burial. An example systems analysis is discussed with assumed performance objectives and various Hanford-specific disposal conditions, waste forms, site characteristics, and engineered barriers. Preliminary waste disposal criteria for 239Pu are determined by applying the allowable residual contamination level (ARCL) method. This method is based on compliance with a radiation dose rate limit through a site-specific analysis of the potential for radiation exposure to individuals. A 10,000-year environmental performance period is assumed, and the dose rate limit for human intrusion is assumed to be 500 mrem/yr to any exposed individual. Preliminary waste disposal criteria derived by this method for 239Pu in soils at the Hanford Site are 0.5 nCi/g in soils between the surface and a depth of 1 m, 2200 nCi/g of soil at a depth of 5 m, and 10,000 nCi/g of soil at depths 10 m and below. These waste disposal criteria are based on exposure scenarios that reflect the dependence of exposure versus burial depth.