Browsing by Author "Fry, RM"

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    Assessment of radioactive fallout arising from testing of nuclear weapons in the South Pacific and the probable effects on the Australian population
    (Australian Atomic Energy Commission, 1973-03) Fry, RM; Symonds, JL; Watson, GM
    The first part of this report gives a short description of the different basic types of nuclear weapon and lists Chinese weapons tests in the northern hemisphere and French weapons tests in the South Pacific by date, together with an indication of the power of each device where such information is available. The second section of the report discusses the measurement of radiation and what dose units are appropriate for assessment of the significance of fallout exposure to man, and outlines the background of natural and man-made radiation to which man is inevitably subject. The principal biological effects of radiation are then identified and the nature of the relationship between radiation dose and the incidence of effects is examined. Conventional radiation protection philosophy assures a linear relationship between dose and effect, which is independent of dose rate, On this assumption it is possible to derive, from the limited high-dose data available, risk coefficients for radiation effects which may be used to calculate the incidence of harmful effects from the low radiation doses relevant to fallout studies. The difficulties and inaccuracies inherent in this extrapolation mean that estimates made in this way are essentially of the upper limits of possible damage, not the most likely value which may often be zero. The final section assesses the magnitude of fallout in Australia from the French and Chinese series of tests and expresses this in the form of dose commitments to man; the dose commitment for any radionuclide being the dose received to date plus the dose to be received in the future from residual long-lived activity already incorporated in the body and remaining in the environment. From these dose commitments, using generally accepted risk coefficients, estimates of the upper limits of the magnitude of the harmful effects, carcinogenesis and mutagenesis, which may be attributed to fallout from the respective series have been derived for the Australian population.
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    Radiation hazards of uranium mining and milling
    (Australian Atomic Energy Commission, 1975-09) Fry, RM
    As well as the need to control the more conventional hazards associated with any mining and milling operation, special care must be exercised in the mining and milling or uranium because of the radioactive nature of the ore. Uranium ore, though only mildly radioactive, contains a complex mixture of radioactive isotopes, the behaviour of which during each phase of the mining and milling process, determines the controls that must be established to ensure safe working conditions. This paper examines each of the radiological problems that arise in these processes and explains their scientific background. The radiation standards that should be applied and the procedures that should be adopted to minimise radiation exposure to all persons are set down in the Australian 'Code of Practice on Radiation Protection in the Mining and Milling of Radioactive Ores 1975'. If the requirements of this code are adhered to, the radiological safety of miners, mill workers and members of the public can be assured. The major operational requirement is to ensure that exposure of miners over their working lives to radon and its daughter products does not lead to an unacceptable increase in their chance of contracting lung cancer. Studies on the incidence of lung cancer amongst underground uranium miners indicate that this risk will be small if lifetime exposures are kept below about 120 'working level months', even amongst underground miners who smoke cigarettes. The risk is much smaller again for miners who do not smoke. Other hazards that must be controlled are exposure of miners and mill workers to external radiation and to dusts containing long-lived radioactive α emitting isotopes. Finally, the solid waste products from the mill (the tailings) which contain most of the naturally occurring radioactivity, must be properly impounded and after closure of the mill, stabilized to ensure long-term containment. Access by the public to the stabilized tailings must be controlled and habitation within the controlled area prohibited.
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    A reformulation of the Lucas Heights liquid effluent discharge authorization
    (Australian Atomic Energy Commission, 1966-08) Fry, RM
    Liquid effluent containing low levels of radioactivity is discharged from the A.A.E.C. Research Establishment at Lucas Heights into a tidal estuary at themouth of which are a number of commercial oyster leases. Since early 1961 the levels of release have been limited by a formula taking specific account of Ra—226, 'other α emitters', Sr-90 and 'other β emitters'. This formula has worked well as is evidenced by the barely detectable levels of radioactivity coming from the Research Establishment found in environmental samples, but it had certain deficiencies and limitations which for operational reasons it became desirable to eliminate. A new formula is described that is sufficiently general not to require future modification in principle and which incorporates recent data on estuarine dilution and concentration factors for nuclides in oysters, and which is based on current 1CRP recommendations and N.S.W. State Regulations concerning maximum permissible doses applicable to members of the general public. Discharges are limited so that population exposures resulting from the ingestion of contaminated oysters, from sunbathing on sands near the discharge point, and from the incorporation of contaminated sand in cuts are kept within acceptable limits; it also ensures that people who daily handle large quantitiesof oysters will not be subjected to unacceptable levels of irradiation. Values for maximum permissible monthly discharge (m.p.m.d.) for 173 nuclides have been calculated and tabulated. For mixtures of these nuclides the formula is: where XI is the quantity of the ith nuclide released and V gallons is the monthly volume of liquid discharged or 3 x 106 gallons, whichever is the smaller.