Uranium series isotopes in the Avon Valley, Nova Scotia.

An U-series isotopic study was carried out in the waters of the Avon Valley, Nova Scotia. The fresh and acidic recharge waters flow rapidly through the watershed composed of a granitic highland and a sedimentary, largely carbonate, lowland plain, before draining to the sea. There is no significant anthropogenic pollution; but, naturally elevated U levels can be encountered within the bedrock. Nonetheless, the U concentrations of the surface and groundwater are low (generally within the range of several hundredths to several tenths of a microg l(-1)), except in the proximity to weathering of U mineralization. The dissolved U in the surface waters appears to be stabilized by organic rather than inorganic complexes. Both the groundwaters and surface waters have similar (234)U/(238)U activity ratios that rarely deviate from secular equilibrium by more than 20% throughout the watershed. The magnitude of the (234)U/(238)U activity ratio is not determined by lithology but rather by the weathering mechanism, the high rate of flushing, and the leaching of local U mineralization. Dissolved Ra is consistently absent. The dissolved Rn concentrations, though variable, are measurable even in surface waters. This may be due to a continual degassing from the U-enriched bedrock or release from local sites of U mineralization underlying the surface water sources.

A new method of retrospective radiation dosimetry: optically stimulated luminescence in dental enamel.

Currently, retrospective biophysical radiation dosimetry lacks a technique that is sensitive, non-invasive, and portable. This has made reliable cause and effect relationships between radiation exposure and its outcomes in humans difficult to establish. Since optical technology is amenable to miniaturization, a search for optically stimulated luminescence in dental enamel was begun. The first successful detection of time dependent optically stimulated luminescence from gamma irradiated enamel was accomplished. This luminescence is absent in enamel that is not irradiated or that was heated following irradiation. Thermoluminescence observations were made concurrently with the optical measurements which clarified the role of the organic component of enamel.

Application of optically stimulated luminescence to the dosimetry of recent radiation events involving low total absorbed doses.

We determined the suitability of optically stimulated recombination luminescence in quartz for low-level dosimetry of recent events such as radiation accidents. Minimum detectable doses were determined for both fired and unfired quartz. Using a single aliquot technique, good detection of doses on the order of 0.01 Gy in fired quartz was achieved. In unfired quartz, the minimum dose detected was an order of magnitude larger. Using single aliquot optically stimulated regeneration of a natural quartz sample, a dose of 0.18 +/- 0.02 Gy was measured and was in good agreement with the dose determined by multiple-activation thermoluminescence. Delayed measurements of radiation doses on the order of 1 Gy were shown to be feasible in an emergency response situation when measured up to 7 wk following the irradiation event, using a regeneration-ratio technique. Our conclusions are based on observations of 100 degrees C isothermal decay of the luminescence, high-temperature preheating experiments, thermal fading after prolonged room temperature storage, and observations of the relationship between post-annealing residual luminescence and the TL glow curve. We were able to correlate the optically stimulated recombination luminescence of quartz extracted from building tile with the sample's 278 degrees C TL emission.