Page 31 - Neutrons for Sciences and Society

Chapter 1 - Pre-history
Jacrot, Perroud, Lacaze and Weil. This was a joint project bringing together physicists, reactor engineers, and low temperature specialists from Grenoble and Saclay. The reactor described summarily in this presentation was a swimming pool type. The only features retained from the Brookhaven design were the under-moderated core, and the use of highly enriched uranium.
Swimming-pool reactors are reactors where the core of
enriched uranium26, is usually immersed in a light water pool (demineralised ordinary water). The latter serves a triple role: it contributes to the neutron thermalisation and cooling of the core and in addition contributes as a protection against the radiation emitted. This type of reactor, developed in the USA since 1950 had been presented during a preceding Geneva Conference in 195527. The SILOE reactor in Grenoble was of this type. The project presented in Geneva by Robert Dautray was similar, but incorporated a heavy water reflector. Jules Horowitz with Victor Raievski had filed a swimming pool reactor patent from where certain aspects were incorporated into the high flux reactor project (RHF).
Maier-Leibnitz was also present at the 1964 Geneva Conference, having been present at the OECD meetings in Paris. He was immediately captivated by the project and its possible realisation in Grenoble. He spoke of this to Joachim Pretsch, head of the division of nuclear research, and to Hans Lenz, the director
26 In naturally occurring uranium there is only 0.7% uranium-235 which is the most common fissile isotope. In enriched uranium this percentage is increase by various physical methods (centrifugation, gaseous diffusion). It is said to be highly enriched when this percentage exceeds 90%. This highly enriched uranium can be used for the fabrication of atomic bombs.
27 Proceedings: https://www.worldcat.org/title/proceedings-ofthe-international-conference-on-the-peaceful-us- es-of-atomic-energy-1955/oclc/514057.
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