Berkeley Nuclear Power Station Case Study

A phase of the decommissioning of Berkeley Nuclear Power Station required access openings to be formed into three vaults containing active waste and into one unused vault.

The main contract was placed by RDU BNFL Magnox Generation with Nukem Ltd, the civils with Amec, who in turn awarded the concrete cutting to Holemasters Demtech Ltd .

An opening 3.4m x 1.7m was formed into each active vault by stitch drilling the 2.0m thick roof into 3 blocks of 9T each. Also, 14 no. 920mm diameter holes were stitch drilled through the same roof section. An opening 7.8m x 2.3m was formed in the fourth vault by stitch drilling into 6 blocks of 12T each. All the blocks were secured to strongbacks by drilling and grouting bars.

In addition, 34 camera holes were formed by diamond drilling single 300mm diameter cores, counterbored with 450 diameters. In total 1,100 holes, 2,200 linear metres of drilling , was carried out, using remote controlled electro-hydraulic drill rigs.

The main constraint, other than those normally imposed during nuclear operations, was to limit the water entering the vaults, and to prevent cores entering the vaults, adding to the nuclear waste. Methods were developed to successfully satisfy these requirements.

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