Standards Development

Scope

This International Standard specifies the criteria for structural safety assessment via elastic analysis for in-vessel components of fusion reactor, which include divertor, blanket, limiter and diagnostic components located inside of vacuum vessel. The structural design criteria in this standard includes static stress evaluation rules and fatigue life evaluation rules.

Purpose

The in-vessel components are located in the vacuum vessel of fusion reactors, and will be activated with high energy neutrons produced by fusion reaction. The in-vessel components have to withstand not only the steady-state loads but also the transient loads during normal and off-normal operation, especially the radiant heat load from the high-temperature plasma. Then, the typical characteristic is that the stress generated in the in-vessel components are dominated by thermal stress induced by heat loads which is secondary stress and supplemented by primary stress induced by mechanical loads. Steady state and transient heat loads are the key design driving loads.

Since the heat load only come from the plasma side, it will induce a very uneven temperature distribution within the component. The maximum temperature gradient will up to 100 ~ 1000 /mm in the near wall of the component in the plasma side. On the other hand, the components need to withstand irregular cyclic heat loads during operation which will influence their fatigue lifetime. Meanwhile, the components have special structure characteristic, such as long tube with thin wall thickness, etc.

Considering the load feature and unique structure of the components, the existing standards can not fully cover the criteria required for structural safety assessment for the in-vessel components of fusion reactors. And once the structure failures of the in-vessel components occur, the reactor must shut down and remote handling technology should be adopted in the maintenance, which will directly affect the operation and maintenance plan for the fusion reactor.

Therefore, it is necessary to develop the appropriate structural safety assessment criteria. For this situation, this proposal provides stress assessment and structural design criteria for the in-vessel components via elastic analysis, which can improve the safety, availability, reliability of the design for in-vessel components.