Progress report of Physics Division. 1st October 1972 - 31st March 1973

MOATA was operated at a nominal 90 kW to assess the problems which might have arisen from the modifications and the higher power levels. No problems were evident. The neutronics and modified cooling circuits proved satisfactory. Greater interest is being shown in MOATA as its higher flux levels and ease of access become better known. A detailed shielding survey indicated that radiation levels greater than 1 mrem were very localised and remedial action would be minor. The overall shielding in the building is, however, not so satisfactory. When the recently installed elevated target platform (ELF) is in use with moderate beam current from the 3 MeV accelerator, shielding arrangements have been found inadequate overall, although levels in the offices cause no concern. The zero power split table machine for reactor studies operated in a satisfactory, trouble-free, manner. Several modifications have been made to improve its operation and safety. The work on MOATA mockup has provided more detail on the reactivity behaviour of the reactor under isothermal and transient temperature conditions. An investigation of the neutronic cross coupling between the twin slab core tanks commenced. Studies have developed out of the safety assessments of the Commission's reactors and some calculations have been performed to define the irradiation field at different reactor's pressure vessels. The neutron capture mechanisms continued under study by means of γ-ray de-excitation for a wide selection of elements using NaI and Ge(Li) detectors. An attempt was made to clarify the 5.5 MeV bump on the spectra