A NEW political row over the controversial award of the #5000m Trident missile submarine refit contract to Devonport Dockyard instead of Rosyth is set to erupt this week when MPs hear vital nuclear safety upgrading work is more than three years behind schedule and #400m over budget.

It will inevitably provide further ammunition for the SNP over Labour, despite the fact the original contract was awarded by the previous Tory government, coming amid rumours that up to 1300 Rosyth jobs are at risk because of the possible cancellation of a Ministry of Defence programme to refit S-class nuclear hunter-killer submarines there.

The extra cost to the taxpayer is due to be discussed by the Commons' spending watchdog group, the public accounts committee.

Labour is understood to have hoped the thorny question of Trident refits could be delayed until after the next General Election. Military sources said last night the nuclear power plant on the first Trident boat, HMS Vanguard, was performing so well it would be possible to put off replacing its fuel rods and a general overhaul until 2001-2002, almost two years later than planned.

The #5000m refit deal for the four Royal Navy Vanguard-class Trident boats was given to the Plymouth yard in preference to Rosyth in 1993 amid claims the Tories were merely seeking to secure votes in marginal south of England constituencies.

The Devonport bid of #236m was #12m lower than its Fife rival, although it also involved #170m from the public purse to bring the area up to standard for the Nuclear Installations' Inspectorate, the independent body which licenses all sites handling nuclear material.

Rosyth, which had handled the vast majority of nuclear refits for the previous 30 years, already had a partial licence for Trident, and still operates the UK's only emergency berth for the boats.

The yard was preparing a giant dock on solid bedrock and fitted with seismic arrester blocks, huge shock absorbers, to meet the stringent refit safety requirements when Devonport entered the bidding in 1992. By that time, almost #250m of public money had been spent on nuclear berthing facilities in Fife, including #120m on a giant dock, RD57.

Rosyth and Devonport have been privatised since 1993. The Plymouth facility is run by Devonport Management Ltd, a consortium headed by the US-owned Brown and Root. The Fife yard is operated by Babcock Thorn.

Devonport ran into safety problems almost immediately after award of the contract. The dockyard complex is built on a base of soft limestone and slate, which the NII says would not meet the requirement for secure handling of a drydocked Trident in the event of seismic shock up to the level of a small earthquake.

DML tried strengthening the existing concrete structure of two old battleship docks and adding 100-foot solid rock anchors. But costs have spiralled.

The NII's nightmare is a seismic shock which would allow seawater into the drydock while a submarine was berthed with its nuclear reactor core exposed and fuel rods still in place. The result would be ''a catastrophic explosion'' which would release a lethal plume of highly radioactive gas.

Labour's only practical but temporary way out of embarrassment would be to scale down the Vanguards' patrols.

Short of scrapping Trident altogether, the problem will not go away. Sooner or later, the boats will have to come in for vital refitting.

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