Reduced Activation Alloy Development for Fusion

Abstract

Developing materials that resist degradation when exposed to neutrons is a key element in international programs to demonstrate the engineering and economic viability of fusion power. An additional requirement is that these materials exhibit low-induced long-lived radioactivity in order to enhance fusion power's environmental (and economic) attractiveness. This article briefly overviews current efforts to develop reduced activation structural alloys for fusion reactor applications.A specific objective of the U.S. Fusion Materials Program is that all reactor components will meet the requirements for near-surface burial. Presently, this is interpreted to mean that all radioactive waste should satisfy Part 61 of Title 10 of the U.S. Code of Federal Regulations (10CFR61), prepared by the Nuclear Regulatory Commission (NRC). Specific activity limits are placed on particular long-lived radionuclides, which, when combined with activation calculations for conceptual fusion devices, place constraints on material compositions. Regulation 10CFR61 was prepared to cover low-level waste produced by the fission reactor industry; it has been necessary to extend it, in principle, to include additional radionuclides. Unlike anticipated waste from a fusion industry, only a small fraction of the fission waste stream is activated metals; hence, the applicability of the regulation is questionable. Further analysis of the probable disposal method for fusion wastes is needed, along with consideration of maintenance and decommissioning scenarios.