Evaluation Of Quantification Of Margins And Uncertainties Methodology For Assessing And Certifying The Reliability Of The Nuclear Stockpile PDF Download

Lawrence Livermore and Los Alamos National Laboratories have developed a common framework and key elements of a national certification methodology called Quantification of Margins and Uncertainties (QMU). A spectrum from senior managers to weapons designers has been engaged in this activity at the two laboratories for on the order of a year to codify this methodology in an overarching and integrated paper. Following is the certification paper that has evolved. In the process of writing this paper, an important outcome has been the realization that a joint Livermore/Los Alamos workshop on QMU, focusing on clearly identifying and quantifying differences between approaches between the two labs plus developing an even stronger technical foundation on methodology, will be valuable. Later in FY03, such a joint laboratory workshop will be held. One of the outcomes of this workshop will be a new version of this certification paper. A comprehensive approach to certification must include specification of problem scope, development of system baseline models, formulation of standards of performance assessment, and effective procedures for peer review and documentation. This document concentrates on the assessment and peer review aspects of the problem. In addressing these points, a central role is played by a 'watch list' for weapons derived from credible failure modes and performance gate analyses. The watch list must reflect our best assessment of factors that are critical to weapons performance. High fidelity experiments and calculations as well as full exploitation of archival test data are essential to this process. Peer review, advisory groups and red teams play an important role in confirming the validity of the watch list. The framework for certification developed by the Laboratories has many basic features in common, but some significant differences in the detailed technical implementation of the overall methodology remain. Joint certification workshops held in June and December of 2001 and continued in 2002 have proven useful in developing the methodology, and future workshops should prove useful in further refining this framework. Each laboratory developed an approach to certification with some differences in detailed implementation. The general methodology introduces specific quantitative indicators for assessing confidence in our nuclear weapon stockpile. The quantitative indicators are based upon performance margins for key operating characteristics and components of the system, and these are compared to uncertainties in these factors. These criteria can be summarized in a quantitative metric (for each such characteristic) expressed as: (i.e., confidence in warhead performance depends upon CR significantly exceeding unity for all these characteristics). These Confidence Ratios are proposed as a basis for guiding technical and programmatic decisions on stockpile actions. This methodology already has been deployed in certifying weapons undergoing current life extension programs or component remanufacture. The overall approach is an adaptation of standard engineering practice and lends itself to rigorous, quantitative, and explicit criteria for judging the robustness of weapon system and component performance at a detailed level. There are, of course, a number of approaches for assessing these Confidence Ratios. The general certification methodology was publicly presented for the first time to a meeting of Strategic Command SAG in January 2002 and met with general approval. At that meeting, the Laboratories committed to further refine and develop the methodology through the implementation process. This paper reflects the refinement and additional development to date. There will be even further refinement at a joint laboratory workshop later in FY03. A common certification methodology enables us to engage in peer reviews and evaluate nuclear weapon systems on the basis of explicit and objective metrics. The clarity provided by such metrics enables each laboratory and our common customers to understand the meaning and logic of technical and management decisions affecting stockpile performance and safety.