The Australian Government plans to rehabilitate the former nuclear weapons testing ranges at Maralinga and Emu in South Australia and to allow access to the areas for the Pitjantjatjara (Aboriginal) people who are the traditional owners of the land. The major radiological hazard posed by reoccupation of the ranges arises from inhalation of residual plutonium. The committed effective dose that these people might receive from inhalation on reoccupation of the lands is computed for a range of sites. The estimated doses for permanent occupancy range up to 300 mSv y-1 indicating the need for substantial rehabilitation before these areas are suitable for unrestricted access.
Experimental attenuation curves have been obtained for uncollirnated bremsstrahlung radiation, incident on ilmenite-loaded concretes of densities 180, 240 and 270 lb/ft3. Measurements were made at bremsstrahlung end-point energies of 5, 10, 20, 30 and 40 MeV, at thicknesses increasing in steps of 3 in. from 0 to 30 in.It was found that for all except the Iowest energy, the breinsstrahlung weighted build-up factor was relatively small. Attenuation curves, calculated for a Schiff spectrum with a simplified photon transport equation, in which all photons were assumed to be forward Soing, agree closely with the measurements for all except the 5 MeV case.
Energy distributions of fast neutrons (>0.5 MeV) transmitted through slabs of normal and high density ilmenite concretes, obtained by time of flight methods, are presented for concrete thicknesses increasing in steps of 7.6cm from 0 to 46cm. The incident spectrum consisted of a photoneutron continuum from aluminium irradiated with 35 MeV bremsstrahlung, and was thus of somewhat higher mean neutron energy than a typical fission spectrum.The measured distributions are in satisfactory agreement with the results of a Monte Carlo simulation, and results from the latter are used to extrapolate the measured data to greater thicknesses and other ilmenite concrete densities.
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