The evidence was that plutonium from Calder Hall and Chapel Cross was processed separately from that from the 'civil' reactors of the two electricity boards only if the plutonium from Calder Hall and Chapel Cross was of weapons-grade. Reactor-grade plutonium, said BNFL, was always 'co-processed'.
According to this evidence, the reactor-grade plutonium used in the Nevada bomb test was a porridge of plutonium from Calder Hall, Chapel Cross and the electricity board power stations. On average, more than 80 per cent of the porridge is from the electricity board power stations.
R. V. HESKETH