§ Dr. David Clark
To ask the Secretary of State for Defence (1) whether changes were made to the safety plans for the Faslane nuclear site following discovery of seismic problems; what was the total cost of these changes; and when they were carried out;
(2) what frequency his Department assumed when planning the Faslane nuclear site for earthquakes measuring 0.2 G or more horizontal ground acceleration;
(3) what steps his Department took to ensure that. appropriate (a) seismic surveys and (b) geological structure surveys were conducted in the planning stage of the Faslane nuclear site;
(4) what technical changes were made to the shiplift facility for the Trident system at Faslane following lessons learnt from the Chernobyl nuclear reactor explosion; and what was the total cost of these changes;
(5) what is the maximum horizontal ground acceleration that the Faslane nuclear site is able to withstand from an earthquake.
§ Mr. Freeman
Safety plans for the Clyde submarine base, Faslane, are kept under continuous review and amended as necessary in the light of all relevant information. During the planning stage of the Trident 455W support facilities at Faslane, a number of geotechnical reports on the site were commissioned on behalf of the Ministry of Defence from distinguished academics and other experts. These included one specifically on geology and seismicity. Planning also drew on the British Geological Survey's national database of fault lines and seismic events. The support facilities were designed in accordance with the relevant national standard, namely, that a reactor plant must be capable of being shut down and maintained in a safety shut down condition following an earthquake of a severity with a probability of occurrence not exceeding one in 10,000 years. For Faslane the design peak horizontal ground acceleration of such an earthquake is 0.2 G. In the event, the Ministry of Defence achieved a more demanding criterion for the shiplift in the light of developments in United Kingdom civil practice which had followed the Chernobyl incident.
It is not possible to identify separately the financial effects of the changes in the design of facilities during planning and construction nor of past and prospective refinements to safety plans.