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Design Risk Analysis Comparison Between Low-Activation Composite and Aluminum Alloy Target Chamber for the National Ignition Facility

Holger H. Streckert, Robert W. Schleicher

Fusion Science and Technology

Volume 31 / Number 1 / January 1997 / Pages 26-34


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The baseline design for the target chamber for the National Ignition Facility (NIF) consists of an aluminum alloy spherical shell. A low-activation composite chamber (e.g., carbon fiber/epoxy) has important advantages such as enhanced environmental and safety characteristics, improved chamber accessibility due to reduced neutron-induced radioactivity, and elimination of the concrete shield. However, it is critical to determine the design and manufacturing risk for the first application. The replacement of such a critical component requires a detailed development risk assessment. A semiquantitative approach to risk assessment has been applied to this problem based on failure modes, effects, and criticality analysis. This analysis consists of a systematic method for organizing the collective judgment of the designers to identify failure modes, estimate probabilities, judge the severity of the consequence, and illustrate risk in a matrix representation. The two chamber designs are reduced to functional components where separate failure mode and effects analyses and criticality analyses are applied and incorporated into sets of worksheets. Criticality matrices are subsequently constructed from the worksheets. The results of the analyses indicate that the composite chamber has a reasonably high probability of success in the NIF application. The aluminum alloy chamber, however, represents a lower risk, partially based on a more mature technology.

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