Harnessing Fusion Power: Safety and Environment - Overview and Thrusts ReNeWS HFP Theme Workshop, 2-4 March 2009, UCLA Harnessing Fusion Power: Safety and Environment - Overview and Thrusts Phil Sharpe and the S&E Panel

Gaps Identified in S&E Basis for defining gaps: Imminent control of fusion power plants ensures public protection and is executed by various levels of regulation. Nuclear hazards are controlled by regulatory authorities such as the NRC in the US. Regulatory paradigm is shifting balance from “Worst-case Scenario” analyses toward the “Risk-informed” safety basis, potentially requiring a larger number of analyses in the context of probabilistic safety assessments. In terms of available energies in postulated accidents, fusion is quantifiably less hazardous than fission, thereby application fission-based regulations is overly restrictive. Engineered safety systems are applied in plant design, although level of demonstration is not yet established (even for ITER).

Gaps Identified in S&E, cont. Gap: Component Qualification Required to validate plant/DEMO design and functionality of key safety components (e.g. primary confinement boundary such as vacuum vessel and penetrations) and passive features (e.g. blowdown overpressure protection, vault inerting, etc.) Integrated component testing in a high fluence fusion environment is required for demonstration (establish fusion-specific codes and standards) Highly dependent upon detailed design.

Gaps Identified in S&E, cont. Gap: Safety Analysis and Source Term Requires computational tools and database of materials response to postulated off-normal of accident conditions Needs for some level of integrated testing in severe conditions, consistent with energy and materials inventory limits (as with ITER, e.g. ICE and EVITA, magnet arcing, dust explosion…) Dependent upon conceptual design specifications for type and quantity of materials, limits for physical processes, general component layout or configuration, and effect of periodic refurbishment (reduces inventories)

Gaps Identified in S&E, cont. Gap: Waste Management Use of low activation materials to minimize/eliminate high level waste; yet substantial quantities of low-level waste are anticipated Requires de-tritiation of materials for recycling/re-use strategies Dependence upon conceptual design… insofar as materials, fluences, and maintenance periods are considered

Overview of S&E Research Thrusts: S&E research thrusts are broad reaching and reflect the overarching nature of fusion safety and environmental issues. Identified thrusts are generally thematic rather than specifically focused initiatives. Extension of the US Fusion Safety Standard to next-step devices and DEMO plant conceptual designs; lead an effort towards an international fusion safety framework Develop recycle and clearance-based solutions to fusion’s waste stream; refine strategies of de-tritiation of materials Enhance design integration through safety in maturing designs of next-step devices and DEMO/plants Methods for monitoring/removing radioactive materials during DEMO/plant operation