B401.4 in its final stages of being demolished
September 21, 2010
Building 401.4 was constructed during 1954, was ready for occupation by January 1955 and was referred to as the Critical Assembly Building which described the type of installations to be constructed in the building.
During 1955 a device called Zeus was constructed. Zeus measured 60cm across and was used to study the design for the core of the Dounreay Fast Reactor (DFR). The enriched U235 resulting from Zeus was ultimately used in the DFR.
A further reactor system that existed in 401.4 for a short period before being moved to Winfrith was NERO. NERO was a zero energy reactor designed to enable experiments to be carried out on a wide variety of reactor types and on the nuclear properties of materials used in reactors. It consisted of a concrete shield and a flexible system of control rods and instrumentation. A wide variety of lattices could easily be constructed inside the shield. NERO used U235 and was moderated by graphite.
The reactor commenced operation at Harwell in 1957 and was used to investigate the physics of advanced types of graphite moderated reactors. When it was moved to Winfrith in 1960, a pile oscillator was installed. This device enabled the nuclear behaviour of fuels, moderators and structural material in reactors to be studied using small samples.
For further information please contact Angela Vincent, RSRL Communications Manager, Harwell
