The non-proliferation regime is once again threatened by the contentious issue of Reliable Replacement Warhead (RRW) development by the US. The US Department of Energy has proposed the development of a new generation of nuclear weapons that seeks to demonstrate the feasibility of developing reliable replacement components which are producible and certifiable for the existing US nuclear arsenal. The objective of the RRW programme is to improve the reliability, safety and security of the US nuclear weapons stockpile, achieve reductions in the size of the arsenal and reduce the need for underground nuclear testing.

The origin of the RRW programme can be traced to 2004 when the National Nuclear Security Administration's (NNSA) efforts to launch a new round of nuclear weapons were thwarted by the US Congress. Thereafter in May 2005, two nuclear design laboratories - Los Alamos and Lawrence Livermore - began an 18-month RRW study to produce the first RRW warhead for replacing the W76 submarine launched ballistic missile warhead. The RRW study has generated substantial concerns as it is perceived to be an opportunity to expand from a programme of warhead refurbishment to one of warhead replacement with higher margins. As a world leader, the US decision over nuclear issues portends far-reaching implications for the global non-proliferation system.

The RRW programme has given rise to certain fundamental issues and concerns. First, is there any need for new replacement warheads? RRW advocates have argued that since the US halted nuclear weapons production and underground testing with the end of Cold War, the existing US nuclear stockpile consists of warheads that are almost 40 years old - with doubts about the reliability of plutonium there is a need for replacement warheads. However, JASON, an independent panel of scientists and engineers has concluded that plutonium components - known as pits - have lifetimes of a minimum of 85 years and so US nuclear weapons will remain highly reliable for at least the next several decades. Even after this period there will be no pressing need for developing new weapon designs, as the plutonium cores can be remanufactured.

Second, RRW proponents have proposed that the new warheads would significantly reduce the need for testing. This is a fallacious argument. As the new weapons are made more reliable, more plutonium will be added to the weapons' primaries. While this will boost the confidence of the RRW designers that the primaries will meet its minimum yield requirements, it will also increase the potential for substantial nuclear yield if there is an accidental detonation of a high explosive. The issue is rendered graver with the claim that the new warheads do not have to undergo full-scale testing. Hence, there will be no guarantee that the weapons can adhere to the stringent US one-point safety requirements of the existing stockpile. Changes made while increasing the reliability of the new warheads will also enhance the risks of accidental detonation since these new weapons will be built without nuclear explosive proof testing. Hence, there will be a trade-off between reliability and safety.

Third, will the military planners in the US Department of Defence (DoD) accept the new warhead into the existing stockpile without a nuclear test? This seems quite unlikely and can also be perceived as a "bait and switch trick". Hypothetically, ten years from now if the DoD states that it needs the new warheads to replace the existing SLBMs and requires one or two confirmatory underground nuclear tests to ensure the credibility of these weapons would the US Congress object? In all probability, it will not. If the US were to conduct a single nuclear test it will open the Pandora's Box of other nations to resume nuclear testing and lead to the resumption of a full-scale nuclear weapons arms race.

Fourth, contrary to the RRW supporters' claims that it will be cheaper to build new weapons than to maintain the existing "aging" stockpile, the design costs for an RRW will be enormous. First funded at US$9million in 2005, the RRW study was awarded US$25million in 2006 and in 2007 the NNSA has requested US$27.7 million for the programme. The NNSA's projected funding for the next five years is estimated at US$97 million. If left unchecked, the weapons labs would expand the RRW study into a multi-million-dollar project in an effort to redesign the entire stockpile. Massive defence spending by the US would encourage other nations to indulge in similar ventures leading to spiraling arms race at the cost of domestic requirements.

Finally, new warhead designs and their subsequent production with new capabilities and new missions will cast significant doubts on US non-proliferation commitments. This may well lead to reducing pressure on Iran and North Korea to relinquish their nuclear weapons programmes and encourage other nations to develop nuclear weapons.

The RRW has the potential to dangerously expand the role of nuclear weapons. It can also be used to develop earth-penetrating warheads making them more usable and severely reducing the threshold for nuclear weapons. As a world leader, US reliance on nuclear weapons would severely disrupt international cooperation in non-proliferation and prove to be a major setback for global disarmament.