Engineered product storage under the advanced fuel cycle initiative. Part II: Conceptual storage scenarios

The Advanced Fuel Cycle Initiative (AFCI) of the US Department of Energy stresses waste minimization within an integrated nuclear fuel cycle. In one possible future fuel cycle scenario, the radionuclides 244Cm and 241Am are placed in decay storage until a capability for fast-spectrum transmutation is available. We discuss the scale of hypothetical wet and dry storage facilities for cesium/strontium and americium/curium products. Because of the extended storage period for cesium/strontium products, underground storage appears to be the option most acceptable to regulatory policy. Several underground designs are discussed. To reduce the required underground storage space, we recommend a pre-staging period where the cesium/strontium products are cooled in a small pool for 30–50 years. Americium and curium products would require storage for not more than approximately 50 years. For this reason, and because of the high thermal power density, pool storage appears to be the best option for americium and curium.