January 2007
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Critical Level 1 Verification & Validation Milestone Completed

An external review panel convened at ASC headquarters on December 5, 2006, to review completion evidence for a FY06 Level 1 Milestone to “deliver advanced ASC physics and engineering simulation capabilities to support the W76 and W80 LEP/certification.” Sandia’s contribution to the milestone consisted of (1) validating fire model predictions of heat flux to a weapon; (2) quantifying weapon safety margins and uncertainty in fire environments; (3) determining adequacy of arming, fuzing & firing (AF&F) assembly response predictions in a hostile blast environment. A Level 2 Milestone was completed in each of these areas. The panel concurred that the milestone had been successfully completed.

The panel summarized the significance of the milestone completion as follows: “For the first time, a quantification of margins and uncertainty (QMU) analysis of a critical nuclear safety stronglink/weaklink thermal race in an abnormal thermal environment (hydrocarbon fuel fire) can now be performed. Historically, evidence was provided with limited test data and frequently supported with subjective engineering assessments. We now have a viable QMU process that will provide additional quantifiable evidence for weapon system qualification and the ability to identify margins and uncertainties against nuclear safety requirements.

The system-level shock response to hostile endo-atmospheric blast is an environment that cannot be simulated with high fidelity in a ground test. Therefore, to support system design and qualification, a structural dynamics model was developed and validated using blast-tube test data from an instrumented reentry body and (AF&F) unit. This model successfully calculated the necessary structural responses to generate the subsystem and component-level mechanical environment specifications. The modeling provided the design engineers with higher fidelity specifications for this hostile environment than had been supplied on previous reentry systems. It was recognized that efforts need to continue to model and simulate the complete tactical environment for hostile endo-atmospheric blast.”