§ Mr. Frank Cook
asked the Secretary of State for Defence on what basis the countermeasure zones in the public safety schemes for nuclear-powered submarines at Vickers shipyard at Barrow-in-Furness and Devonport dockyard were set at their current limits; if there are any plans to change them in the light of the higher fission product inventory at Devonport; and if he will make a statement.
§ Mr. Stanley
My Department's contingency plans are based on an assessment of the magnitude of releases to the atmosphere associated with various reactor accidents scenarios, and the probability of their occurring. Since it is inconceivable that a reactor accident on one submarine would result in a reactor accident aboard another, the source term release is not cumulative where more than one submarine is present.
The counter-measure zone in the public safety scheme for all naval bases and for the Vickers shipbuilding yard at Barrow is based on the assessment that, within a circular zone of 550 metres radius centred on the submarine, counter-measures will be taken automatically as soon as a reactor accident occurs; that all people remaining within the zone have been given instructions on what they should do; and that, provided they follow these instructions, no people within the zone should exceed any of the upper emergency reference levels of dose specified by the National Radiological Protection Board, and the majority 5W should not exceed any of the lower levels of dose specified by the National Radiological Protection Board. There are no plans to change this assessment.