§ Mr. Llew Smith
To ask the Secretary of State for Defence, pursuant to paragraph 72 of the Strategic Defence Review, Cm. 3999, what were the reactors of origin of the 7.6 tonnes of defence plutonium; and if he will list its isotopic composition. 
§ Mr. Spellar
The reactors of origin for the bulk of the stock of 7.6 tonnes of plutonium are Windscale Piles, Calder Hall and Chapelcross. We have announced, as part of the Strategic Defence Review, our intention to produce by Spring 2000 our initial report of Defence fissile material production since the start of our defence nuclear programme in the 1940s. It would be contrary to national defence and security interests to reveal the isotopic composition of this plutonium and this information is therefore being withheld under Exemption 1 of the Code of Practice on Access to Government Information.