Implications of Plutonium Isotopic Separation on Closed Fuel Cycles and Repository Design

Advances in laser enrichment may enable relatively low-cost plutonium isotopic separation creating a new unexplored dimension in fuel cycle options. This may have large impacts on light water reactor (LWR) closed fuel cycles and waste management. If ²⁴⁰Pu is removed before recycling plutonium as mixed-oxide (MOX) fuel, it would dramatically reduce the buildup of higher plutonium isotopes, americium, and curium. Plutonium-240 is a fertile material and thus can be replaced by ²³⁸U. Eliminating the higher plutonium isotopes in MOX fuel increases the Doppler feedback, simplifies reactor control, and allows infinite recycle of MOX plutonium in LWRs. Reducing production of ²⁴¹Pu by removal of ²⁴⁰Pu reduces production of ²⁴¹Am—the primary heat generator in spent nuclear fuel after several decades. Reducing heat-generating ²⁴¹Am would reduce repository size, cost, and waste toxicity. Avoiding ²⁴¹Am avoids its decay product ²³⁷Np, a nuclide that partly controls long-term oxidizing repository performance. The ²⁴⁰Pu could be added to the high-level waste for disposal. Some of these benefits also apply to plutonium recycled into fast reactors. However, the benefits are fewer because in a fast neutron spectrum, ²⁴⁰Pu is both a fissile material and a fertile material. There would be incentives to separate ²⁴²Pu and dispose of it as a waste.