Progress report of Physics Division including Applied Mathematics and Computing Section. 1st April 1971 - 30th September 1971

All the mechanical and electronic components for the zero power splitable machine (the critical facility) arrived in excellent condition from France. Installation began and good progress was made on the mechanical side where the base and tables were successfully assembled and are being adjusted to meet the exacting specification. Power transients arising from the insertion of short reactivity steps were studied for the reactors, HIFAR, MOATA and the critical facility. Some effort was also devoted to the study of blowdown accidents in light water reactors and calculations of some Italian experiments were made successfully. The measurements of fast fission factor and initial conversion ratios for a range of natural uranium heavy water reactors were completed, and good progress is being made with neutron streaming in aluminium-water lattices. Many other investigators of this problem appear to have neglected or given insufficient attention to the case where the neutron beam is parallel to the plates. It is difficult to fit a cosine curve uniquely as coarse and fine features can not be separated. Previous analysis of the moisture content of soils and concrete by neutron scattering was successfully applied to obtain information on the variation of the moisture in large coal stacks as a function of time. This work was done in conjunction with Electricity Commission of N.S.W. Although a small Pu/Be source was found adequate for the above work, development continued on producing neutron pulses by means of a coaxial plasma focus device. Neutron pulses were produced regularly, but the output was variable; the fault was traced to breakdowns at the breech end of the device where restriking occurs. Although discrepancies of about 2% exist between V-bar for spontaneous fission of 252Cf as measured by the liquid scintillation method and by the Manganese bath method, this important quantity is being measured locally using the liquid scintillator method. Preliminary results suggest a value somewhat lower than obtained by other scintillator groups but still discrepant from the results obtained by other methods. The measurement of the kinetic energy of fission fragments is being extended because of its assistance in elucidating the energy dependence of V-bar. A diffusion theory code is under development as a basic module to a kinetics code package