Trident more effective with US arming device, tests suggest

Tests have implications for UK role in future disarmament talks and raise questions about independence of nuclear missiles
A new warhead firing system will make Britain's nuclear missiles more accurate and effective tests in the US show. Photograph: Lt. Stuart Antrobus/CROWN COPYRIGHT RESERVED/EPA

Successful tests have been carried out in the US on a new warhead firing system to arm Britain's nuclear missiles, making them more accurate and more capable.

The move underlines the extent to which Britain's Trident system is dependent on the US, and it could have serious implications for Britain's role in any future disarmament negotiations, military analysts and experts on British and US nuclear weapons say.

The tests on an upgraded nuclear warhead component, called W76-1, to arm Britain's Trident missiles have been disclosed by Sandia National Laboratories in the US. "The first W76-1 United Kingdom trial test" provided data "critical to the UK implementation of the W76-1", according to a report in the latest issue of Sandia's official publication, Labs Accomplishments.

Defence sources admit that the new arming device would make Britain's nuclear missiles more accurate and more effective.

The Ministry of Defence has always been reluctant to comment publicly on plans to equip Britain's Trident missiles with US components. It describes the new US firing system fuse as a "non-nuclear part" of the warheads but insists that the nuclear warheads themselves are British designed and built. The submarines are designed in Britain but the Trident missiles are leased from the US.

US navy officials say the upgraded American firing mechanism would make Trident missiles more effective against "hard targets". British defence officials privately agree.

Such comments suggest "a significant improvement of the military capability of the weapon", Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, said. "The fuse upgrade appears to be modernisation through the back door," he added.

Nick Ritchie, an expert on Trident and research fellow at Bradford University's Department of Peace Studies, said Sandia's revelations "underline the extent to which the UK's nuclear weapons programme is fully integrated with the US programme, reinforcing our technical, political and financial nuclear dependency and a fuzzy, at best, notion of being an independent nuclear power." A new US arming, fusing, and firing system that controls the detonation of the warhead, combined with the high accuracy of Britain's Trident warheads will allow the UK to threaten hard targets such as underground bunkers, Ritchie added.

He said the US programme would extend the service life of Trident warheads by 30 years.

The government was first questioned about the new US components for Britain's Trident missiles in 2007 by Nick Harvey, the Liberal Democrat defence spokesman and now armed forces minister. Des Browne, then defence secretary, told him: "I am not prepared to discuss the detailed performance characteristics of our nuclear weapons."

The government is particularly sensitive about the Trident nuclear warhead upgrade as it could be seized on by non-nuclear states in any forthcoming international disarmament talks.

The disclosures come at a time when discussions about how to replace the existing Trident system is causing severe strains within the government.

Liam Fox, the defence secretary, insists the existing fleet of four submarines must be replaced like-for-like and Britain must persist with a continuous at-sea deterrent (CASD) – that is, having one nuclear-armed submarine on patrol every day of the year.

Harvey told the Guardian earlier this year that alternatives did not seem to have been given detailed or objective assessments. "The debate has been very much yes or no to this single notion of how a credible deterrent can be provided," he said.

No date has yet been fixed for the "initial gate" decision on the design of the new Trident submarine fleet. The MoD first said it would be announced in December. One of the problems is what kind of nuclear reactor would propel the submarines. The choice is between the existing pressurised water (PWR2) reactor of the kind used in the navy's Astute-class conventionally armed submarines and a new PWR3 reactor of US design.

A decision about the final makeup of a successor to the existing Trident system has been put off until after the general election, due in 2015. The MoD was unable to immediately respond to Sandia's disclosures or their significance.