§ Mr. Benn:
A small experimental fast breeder reactor has been in operation at Dounreay since 1959. This reactor has been used since 1963 as a test bed for advanced fuels and materials. There have been frequent scheduled shutdowns because of the experimental nature of the programme.422W
In May last year, a small leak was discovered in the primary sodium circuit of the reactor. Since then, work has been directed towards locating and repairing the leak and it is anticipated that remedial work will be completed in the next few months.
As a result of the experience obtained with the experimental reactor, a 250 MW(E) fast reactor is now being constructed at Dounreay to be producing power by 1971. Construction has not been affected by the sodium leak in the experimental reactor and is proceeding to programme. It is anticipated that further commercial reactors of this type will he introduced by the mid to late 1970's.