• QMU could facilitate the communication of weapons system performance information to the Department of Defense (DOD) and Congress.

QMU extends the concept of classic engineering factors that compute the ratio of design load to maximum expected load. Its use brings a systematic, quantitative approach to thinking about margins, M, and uncertainties, U. Using QMU, the national security laboratories can identify the factors and uncertainties that are most important to warhead performance. Resources can then be devoted to improving reliability and confidence based on those results.

From its investigations, the committee determined that QMU offers the following benefits:

  • Its use has led to a greater emphasis on quantifying uncertainties in weapons performance to complement the national security labs’ long-standing emphasis on quantifying margins.

  • It allows performance margins to be managed as a system. This in turn allows designers to better evaluate the interconnections among components of the system and to answer quantitatively questions such as How much margin is enough? or How much uncertainty can be tolerated? QMU allows weapons designers and managers to consider trade-offs among schedule, cost, and performance. It is being used to guide investment decisions for both R&D and stockpile stewardship.

  • It enables designers to monitor aging weapons and compare designs. The confidence ratio, M/U, is most effective for assessing the performance by tracking changes in it over time. For example, determining M/U as a function of the age of gas in the gas bottle can let the designers decide when the bottle must be replaced. It should be noted that the QMU methodology is likely to evolve over time as well, possibly faster than the changes that occur in aging warheads. To the extent such changes might affect the value of time-dependent measurements, these changes need to be accounted for when using QMU to monitor aging weapons.

  • It is helping to improve communication among weapons designers, national security laboratory managers, and the three laboratories. It is also being used to explain the annual assessment process to nontechnical audiences, including senior DOE managers, senior DOD officials, Congress, and other external customers.

  • An ongoing purpose of the science campaigns of the weapons program is to reduce uncertainties. QMU is applied in a snapshot mode when stockpile assessments are made in order to quantify



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