— The US has selected the design for a controversial new nuclear warhead to replace the Cold War era weapons currently deployed in its submarines.
The National Nuclear Security Agency (NNSA) says the goal is to replace ageing bombs with newer versions specifically designed to have long operational lifetimes, as well as enhanced security.
However, critics say the existing bombs are good enough, and that developing new warheads gives entirely the wrong message at a time when the US is trying to control nuclear proliferation (see earlier commentary by Lawrence Krauss: We are closer to Armageddon). Questions also remain about whether or not the new warhead will require nuclear tests.
Existing US nuclear bombs date from the Cold War, and are typically over two decades old. Although the US has been dismantling old warheads, NNSA says the current administration wants to replace some of these with new ones to provide "a credible nuclear deterrent with the smallest nuclear weapons stockpile needed".
To remain usable, old warheads must be periodically overhauled, but NNSA worries that "small changes accumulate during refurbishments that take a weapon farther away from the original designs that were confirmed by underground nuclear testing". The new "Reliable Replacement Warhead" will instead be designed for better long-term maintenance.
The RRW will also replace conventional high explosives with less-sensitive material, reducing the chances of an accidental detonation> And it will eliminate hazardous materials such as beryllium to make manufacturing and reprocessing safer.
The agency said it chose the design presented by the Lawrence Livermore National Laboratory in California because it had "higher confidence in the ability to certify the Livermore design without underground nuclear testing". That would make it the first US nuclear weapon designed entirely without full-scale tests. The National Ignition Facility being built at Livermore could perform laboratory-scale tests to validate the design.
Rate of deterioration
Yet outsiders doubt the vital plutonium "pits" of ageing warheads are deteriorating at a dangerous rate. In 2006, the JASON defence study group concluded that most plutonium components of most bombs "have credible lifetimes of at least 100 years", and that the lifetimes of others could probably be extended (read the report (pdf format)). Earlier Pentagon studies had estimated lifetimes at 45 to 60 years, implying Cold War era weapons would become unreliable in another decade or two.
Another troubling issue is nuclear testing. The US conducted its last underground nuclear test in 1992, but it refused to ratify the Comprehensive Nuclear Test Ban Treaty. Although NNSA maintains the new design is close enough to older bombs that it will not require testing, others insist that nuclear tests are the only way to validate a new design.
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