Robert Nelson’s article “Nuclear Bunker Busters, Mini-Nukes, and the US Nuclear Stockpile” (Physics Today, Physics Today 0031-9228 56 11 2003 32 https://doi.org/10.1063/1.1634531 November 2003, page 32 ) contributes to the national dialog about the future of nuclear options as a part of US defense strategy. 1,2 This strategy is changing substantially, and with advances in technology, conventional weapon systems are playing a more prominent role.
Nuclear weapons remain a crucial—though less central—element of the US defense posture. It is vital that the nature and roles of weapons be discussed and explored as the US moves toward a much smaller stockpile, which will ensure that the US will be able to deter changing and emerging threats. In that context, we comment on certain technical issues raised in the article.
We agree that the use of a nuclear weapon would have serious consequences and significant political impacts. Conventional options, if effective, would have clear advantages over nuclear options. However, it is essential to compare the consequences—for example, thermal effects, prompt radiation, and radioactive fallout—of alternative nuclear options.
As Nelson notes, a buried burst would produce a base surge that would be the primary nuclear effect near the center of the detonation. For example, destroying a 0.5-kbar target 150 m below the surface requires a 1-kt burst at a buried depth of 10 m. The base surge would be roughly 1.2 km, and an area of 20 km2 would receive a radiation dose of 50 rem or more from fallout after 48 hours. But what is the alternative? By comparison, without earth penetration, a surface burst of 50 kt would be required to destroy the same target, would produce first-degree burns out to a radius of 5.7 km, and would expose an area of 500 km2 to a radiation dose of 50 rem or greater from fallout after 48 hours.
Thus, an equivalent surface burst would produce 20 times as much collateral damage as a low-yield earth penetrator. Such comparisons are required if informed choices are to be made about alternate warhead options for the future US nuclear stockpile.
A “sensible strategy” for dealing with chemical or biological munitions in underground storage may be to seal them in place, as Nelson notes. Under some circumstances, this might be accomplished by conventional munitions. For more deeply buried sites, only nuclear warheads likely could produce the shock pressure necessary to collapse an underground storage facility. In addition, the US cannot rule out circumstances that require the prompt, in-place destruction of such munitions. Once again, some of the conventional options that Nelson discusses may accomplish this, although whether such warheads will be sufficiently effective to destroy agents completely and without venting remains to be seen.
Nelson says that conventional weapons currently under development and testing by the US Department of Defense will have the capability for accurate delivery and penetration into the interior of agent storage facilities before detonation. Nuclear options need to be evaluated for difficult or hardened targets, and must be assessed under the same assumptions of accurate delivery and penetrating capability.
Clearly, the detonation of a nuclear explosion in the interior of an agent storage facility would produce a thermal and radiation environment far beyond anything achievable with a conventional warhead. Such interior detonations would not dissipate their energy in heating and dispersing soil and rock, as Nelson suggests, and may be far more effective than conventional ordnance in sanitizing agent stockpiles. Again, only by making fully equivalent comparisons of the effectiveness and relative collateral damage—including nuclear effects—of the full range of conventional and nuclear options can informed choices be made.
We concur with Nelson that many options for lower-yield nuclear weapons with reduced collateral damage could, in principle, be achieved by adaptation of previously tested or existing warheads—depending on the results of thorough scientific and engineering analysis, including detailed computational modeling. The issue of nuclear testing should not be used as a stalking horse to argue against the thoughtful and informed consideration of future options for the US nuclear stockpile.
Sound technical review of all options is vital for defeating current and future threats and for the future US nuclear stockpile. We cannot emphasize that point strongly enough. Congress recently removed its prohibition of R&D on low-yield nuclear weapons, while retaining its long-standing responsibility for any deployment decisions. It is just such R&D that will help enable informed decisions about the future stockpile. And that R&D may help the US decide whether low-yield options with reduced collateral damage would actually help enhance deterrence and dissuasion and, in turn, reduce the risks to US national security as the nation moves toward a much smaller nuclear stockpile envisioned for 2012 and beyond.
This letter expresses the authors’ technical views and does not necessarily represent the views of Los Alamos National Laboratory, the University of California, the National Nuclear Security Administration, the US Department of Energy, or the federal government.