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ReNeWS HFP Theme Workshop, 2-4 March 2009, UCLA. Harnessing Fusion Power:. Safety and Environment Thrusts - Extension of the Fusion Safety Standard and Design Integration Through Safety. Phil Sharpe, Lee Cadwallader - INL. Extension of the Fusion Safety Standard.
Harnessing Fusion Power:
Safety and Environment Thrusts -
Extension of the Fusion Safety Standard
Design IntegrationThrough Safety
Phil Sharpe, Lee Cadwallader - INL
As designs progress for next-step fusion facilities and DEMO power plants, evaluation of and improvement to the safety basis should occur to satisfy requirements established US Fusion Safety Standard (FSS):
Historical perspective - the safety basis of ITER was established under these requirements, and are presently under review by the French regulatory authority.
Two additional requirements were developed aside from DOE policy:
The FSS purposely describes a series of Functional Safety Requirements, i.e. they tell what must be done but not how they are to be accomplished.
Fusion is not a mature technology compared to other nuclear technologies, and flexibility in this non-prescriptive safety approach allows innovation without overly constraining the technology as is develops.
The requirements (Vol. 1) establish from a regulatory perspective the design and operational envelopes with respect to:
Primarily in the safety assessment and V&V processes…
These items require a sufficiently mature design to allow focus on the relevant materials and interactions -
Safety assessment follows design,and provides feedback through safety integration.
MELCOR simulations for postulated accidents events
Be-steam reactivity measurements of H2 generation
EVITA Thermal fluids benchmarking experiment
Model Comparison to Test Results
Although ITER is being licensed in France as an experimental nuclear facility (similar to reprocessing facilities), the US is the only nation with an established Fusion Safety Standard. No other nation as yet has fusion-specific regulations.
As more countries begin pursuit of fusion power, strong motivation exists to develop an authoritative International Fusion Safety Framework* to ensure consistency in the safety approach. The future of fusion depends on safe, responsible operation of ALL fusion facilities worldwide.
The US should leverage its experience and seize the opportunity to lead development of an international fusion safety framework in coordination with the International Atomic Energy Agency (IAEA).
* - the term ‘framework’ is specifically applied here to indicate an evolving set of requirements, only to become a ‘standard’ after applying the IAEA protocol
A key element of implementing the safety basis
Although design leads safety, experience with ITER has shown that early implementation of safety features into the design is key to moving towards building and operating a particular design within regulatory constraints.
The basic process of safety design integration was safety professionals learning about the system designs: reading design reports and attending system design meetings. This allowed the safety personnel to become familiar with each system design and facilitated working with the design personnel. Safety personnel would require information from the design teams and would help evaluate design alternatives, or would offer design suggestions to the system design teams.
An important design integration issues for ITER was selection of the VV as the first confinement boundary:
This issue is not unique to ITER, but all fusion nuclear facilities must define and maintain the first confinement boundary.
An second issue for ITER safety in design integration was consideration of spatial positioning of equipment of ‘plant layout’:
Safety assessment follows design,and provides feedbackthrough safety integration.