Speaker
Description
Technology Readiness Levels are commonly taken to indicate the “suitability” of a particular component, process, etc. that is part of a larger system. Several versions exist; all assign a simple value (usually 1 to 9) defined in terms of the point in the development and testing cycle that the particular subject has completed. Thus TRL really reflects “maturity” rather than a holistic consideration of the interaction of the component with the system throughout its lifetime.
The TRL approach omits several aspects that are particularly important for fusion:
• probability and consequences of failure
• criticality of the component/process failure
• ability to manufacture and assemble parts correctly avoiding faults during operation
• variation of component suitability through its lifetime
• reliability, maintainability and through life cost.
Fusion combines many systems that use unique technologies and processes and testing these in a representative environment requires access to a fusion reactor. Inevitably, the first plants will have to be constructed from systems that have inherent risk attached to them and some of these will be critical to the operation of the plant (both in performance and safety). Although the TRL approach gives an indication of the level of technical risk associated with a technology, it does not provide a means to rank and manage that risk. In this paper we propose the adoption of Failure Mode Effects and Criticality Analysis (FMECA) to rank these risks and present some examples of applications to fusion.
FMECA, developed in the nuclear, automotive and aerospace industries, originated in the U.S. military. For each component/process all possible failure modes are ranked according to their frequency, detection probability and severity of consequence to the system.
For fusion this technique can be used to assess overall risk and criticality associated with a combination of different components and hence to make technology selection decisions based upon impact of failure rather than the level of maturity of a particular component (the TRL approach). The formulation of the assessment is also compatible with system engineering architectures used to identify component interactions, thus can be inherently part of the design process of a fusion reactor.
Early in the design process it can be used to:
• prioritise areas where R&D can deliver most benefit
• identify non-compliance with regulations
• define key inspection criteria
• define test and maintenance plans
• identify built-in test or failure indicators
Rigorous application to drive the programme will reduce the total time and cost to develop a DEMO as emphasis is placed on change early in the programme. A probabilistic approach to failure allows analysis to be extended throughout the lifetime of the reactor, reflecting the effects of component degradation, maintenance and replacement, thus rendering FMECA far more powerful and relevant to regulators and stakeholders than the TRL approach.
One issue of adopting this method for fusion will be the availability of knowledge and data on failure modes, particularly for the novel systems, and ITER will be of significant value in providing information to inform the analysis.
| Eligible for student paper award? | No |
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