During the Cold War, the United States designed, built, tested, and deployed numerous nuclear warheads of various designs. The results of nuclear tests of the nuclear explosive packages (NEPs) of these warheads provided the ultimate validation of the design procedures, weapon design codes, and designer judgment. Formal design competitions between teams from Los Alamos National Laboratory (LANL) and Lawrence Livermore National Laboratory (LLNL)—each supported by separate branches of Sandia National Laboratories (SNL) for the non-nuclear components and integration with the delivery system—were routinely held. Extensive peer reviews of the types in use today were less frequent and less formal during that era, primarily because of the availability of nuclear explosion testing.
Following the moratorium on nuclear explosion testing that began in 1992, all three National Nuclear Security Administration (NNSA) laboratories intensified their use of technical questioning, collaborative and competitive reviews, tests of components and subsystems, and modeling and simulation to regularly check their work and ensure that a range of perspectives is brought to bear so as to improve quality and uncover any problems. The laboratories have also strengthened their technical evaluation and peer review processes both to ensure the safety, security, and effectiveness of the nuclear stockpile and to help maintain associated science and engineering design and innovation capabilities in the laboratories. Although not a substitute for weapons tests, peer review has become an increasingly important practice at the three NNSA laboratories as a
means of mitigating the risks that the nation’s nuclear weapons will fail to perform as expected if needed.
After an assessment of peer review and design competition, the committee reached four conclusions:
Conclusion 1.1: In the main, peer review processes used by all three NNSA laboratories are healthy and robust, providing benefits such as increasing confidence in weapon assessment and certification, improving our understanding of weapons physics, addressing weapon aging issues, and identifying lower-cost approaches to Life-Extension Programs.
Conclusion 1.2: Incentives for peer review at the NNSA laboratories are abundantly evident.
- Peer review reduces the risk of overlooking a technical option, of relying on suboptimal data or methods, or of simply making an embarrassing mistake, and thereby supports the ingrained culture at all three laboratories, which sets a high standard for quality.
- Peer review is visibly valued by laboratory management.
Conclusion 1.3: SNL and the NEP design laboratories (LANL and LLNL) have taken somewhat different approaches to peer review, owing in large part to SNL’s ability to test non-nuclear components and systems.
- With only archival nuclear explosion test data available, LANL and LLNL rely on vigorous, deep-dive reviews by true competitive peers and other subject-matter experts to critique the results of calculations and subcritical experiments relating to NEP performance.
- With testing data available to verify the performance of components and systems and to validate modeling and simulation tools, peer review at SNL is driven more by the need to assure cost-effective performance of stockpile hardware under all anticipated conditions and by budget pressures to reduce the number of expensive tests.
Conclusion 1.4: All three NNSA laboratories have opportunities to improve their processes for peer review:
- With the exception of major reviews associated with the Annual Assessment Report or Life-Extension Programs, LLNL and LANL lack written guidance for conducting peer reviews to determine in general when a review is needed, how the review is to be conducted, who should participate in the review, or how to address review findings.
- SNL has developed useful written guidance for conducting peer reviews; however, during its visit to SNL and its probing of the presentations made, the committee determined that SNL could profitably make greater use of outside experts in its peer reviews, as called for in its written guidance.
These conclusions led the committee to the following recommendation:
Recommendation 1: The nuclear weapons laboratories should improve their peer review processes in the following ways:
- Los Alamos National Laboratory and Lawrence Livermore National Laboratory should ensure they have short, written guidance for a graded approach to peer review, the rigor of which is appropriate to the stage of work and range of technical activities being reviewed.
- Sandia National Laboratories should strengthen and broaden its use of outside experts on its peer review teams, as articulated in written guidance that Sandia recently finalized.
In the area of design competition, the committee reached one conclusion and one recommendation:
Conclusion 2: The innovations produced by design competitions during the Cold War, as well as the increased confidence in the safety and reliability of stockpile weapons resulting from current assessment processes such as the Independent Nuclear Weapons Assessment Process (INWAP), illustrate the value of having independent teams, using different approaches and methods, addressing common problems.
Recommendation 2: Los Alamos National Laboratory and Lawrence Livermore National Laboratory should continue to maintain independent design capabilities, using different approaches and methods, to enable independent peer review of critical technical issues. Sandia National Laboratories should likewise carry out, for high-priority issues, competitive designs with independent teams that
use different approaches, followed by peer reviews of components, subsystems, and full systems, as discussed in Recommendation 1.
The Reliable Replacement Warhead (RRW) design study produced innovative designs by competing teams at LANL/SNL-New Mexico and LLNL/SNL-California.1 However, the manner in which the study was conducted led to deep resentments at the laboratories.
Conclusion 3: Although the RRW design study succeeded in producing innovative weapon designs by the competing teams, its value was reduced because technical experts from the competing laboratories were not given the opportunity to critique one another’s ideas through interlaboratory peer review or to address criticisms at the science and engineering level before the final designs were formally presented to NNSA and potential end users.
Recommendation 3: To guide future design studies and design competitions, the National Nuclear Security Administration (NNSA) should provide a formal written statement articulating the design requirements and objectives, along with the selection criteria, in advance of any authorized work. NNSA should also ensure that interlaboratory peer review takes place and that competitors have an opportunity to address criticisms at the science and engineering level before the results are formally presented to stakeholders outside NNSA.
Finally, the committee is deeply concerned about the state of design competition at all three laboratories. There have been no full2 design competitions for NEPs since the 1992 moratorium on the testing of nuclear explosions. The Department of Defense (DOD) has not asked for any fundamentally new warhead designs, and for a considerable time Congress limited work on new designs.
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1 The Reliable Replacement Warhead design study was intended to generate competitive designs for a highly reliable warhead with enhanced surety. In addition, the competition aimed for a design that could be manufactured relatively easily with currently available materials, eliminating some potentially hazardous materials that had been used previously. Finally, it was necessary that the weapon as designed could be certified without nuclear explosion testing.
2 By “full design competition” the committee means competitions that integrate the full end-to-end design process, including design of the integrated NEP—from conceiving of a novel design to address a threat, through production of an engineering prototype, a step that provides essential feedback about the practicality of a design. Full design competition would not include nuclear explosion testing.
Design competitions, and the subsequent testing of components, subsystems, and systems (within the limits of national policy and agreements) are critical to developing the next generation of nuclear weapons designers with expertise that goes beyond analysis and modeling. Although it was considered too expensive for every design competition to result in the production of a prototype during the Cold War, those that did provided the feedback that designers needed to stay at the cutting edge. The number of the NEP laboratories’ science and engineering personnel with hands-on experience in nuclear weapons design and nuclear explosion testing continues to decrease and will reach zero in the next decade or so. Once this experience is lost, it could limit the nation’s strategic options, and it will be difficult to reestablish.
Looking to the future, maintaining nuclear weapons design skills at the NEP laboratories—as well as production skills within the NNSA complex—is essential to achieve three objectives:
- Maintaining a credible nuclear deterrent workforce that is capable of designing and building weapons to meet evolving threats;
- Understanding the status and direction of foreign nuclear weapon programs, and thus strengthening the nonproliferation regime; and,
- Determining the best and most cost-effective approaches to resolving problems that arise during stockpile weapon surveillance and life extension programs.
To avoid the potential of losing a capability that could be essential for responding to evolving threats, the NNSA complex needs a means of exercising, on a regular and ongoing basis, the full suite of nuclear weapons design, development, and engineering capabilities through true design competitions. Thus, the committee makes the following conclusion and recommendation.
Conclusion 4: In contrast to the robust state of peer review at the NNSA laboratories, the state of design competition is not robust.
- There have been no full NEP design competitions since the 1992 nuclear explosion testing moratorium. Recent design studies have been good analysis and modeling exercises, but they did not result in actual engineering and fabrication of components and systems; thus, they did not exercise the complete set of skills required in the NNSA complex to design nuclear weapons that would be an effective deterrent, nor was the credibility of any design assessed by fabricating a device or by non-nuclear testing.
- At SNL, the need to continually replace aging or obsolete nonnuclear components in stockpile weapons, as well as the large Life-Extension Programs for the W76 and B61, have indeed exercised designers’ skills. However, these exercises do not stimulate the full creativity and innovation that result from a true blank slate design competition that includes engineering and building a prototype.
Recommendation 4: In order to exercise the full set of design skills necessary for an effective nuclear deterrent, the National Nuclear Security Administration should develop and propose the first in what the committee envisions as a series of design competitions that include designing, engineering, building, and non-nuclear testing of a prototype. The non-nuclear components produced by Sandia should be integrated into the design and fabrication of the prototype. This should be done with the clear understanding that this prototype would not enter the stockpile.
Implementation of the committee’s four recommendations would help develop and maintain the most important asset—a competent workforce with demonstrated skills and judgment—and instill confidence by all stakeholders (including adversaries) in the ability of this workforce to maintain the nuclear deterrent.
