Health physics最新文献

On 14 February 2014, there was a release of radiological material at the Waste Isolation Pilot Plant in New Mexico due to improper waste packaging. The resulting chemical reaction released 241Am as airborne contamination in the Waste Isolation Pilot Plant underground repository. This incident caused a small leak through the bypass dampers, creating effluent in an airborne plume of radiological contamination consisting of primarily 241Am. The original ground deposition was determined using validated plume modeling for the precipitation to ensure the release was below regulatory limits. Building upon this data allows for the assessment of long-term, off-site doses downwind of the facility. Using the health physics code HOTSPOT, air source terms were generated across the ground deposition plume in grid format to allow for a detailed analysis of the full scope of the ground deposition plume. The individual squares of the grid, or "kernels" were summed to calculate the dose at different offsite locations from the inhalation pathway. The lifetime integrated total effective dose equivalents (TEDEs) of these areas were all found to be, conservatively, on the order of millisievert or less and thus negligible from a radiobiological perspective. Additionally, further resuspension of this material was accounted for using three of the four different methods available in HOTSPOT. Using conservative assumptions, the wind-adjusted upper bound lifetime doses of all off-site locations were found to be substantially less than the average yearly background dose of around 3.10 mSv and are thus negligible.

US nuclear weapons launched from Johnston Island for testing purposes in 1958 and 1962 resulted in 12 successful launches, from which high-altitude nuclear detonations occurred, and four failed launches, resulting in aborted tests with no nuclear detonations. Lists of US nuclear tests produced by testing organizations include only events in which nuclear detonations occurred. Hence, the four failed launches in which no nuclear detonation occurred were not considered tests and are not in the lists, even though three of the failed launches resulted in significant local contamination of Johnston Island. A few summaries of nuclear testing at Johnston Island have mistakenly assumed that the launches resulting in local contamination were among the 12 nuclear tests listed for Johnston Island. This note explicitly lists the identities of all 16 launches of nuclear devices from Johnston Island for the purpose of correcting this assumption.

Determination of 210 Pb, 210 Po, 234 U, and 238 U activity concentrations in groundwater sources used for drinking water can improve confidence in ingestion dose assessments used for comparison with radiological governance guidelines, such as the Australian Drinking Water Guidelines. Such results can provide additional guidance information for detailed assessments where water supplies exhibit high relative concentrations of natural radioactivity. Measurements of these radionuclides, as well as the more commonly measured gross alpha and beta, 226 Ra, and 228 Ra activity concentrations, were undertaken for 21 water supplies in regional Queensland, Australia. Groundwater was the primary or only source for these water supplies. Dose assessment using the measured values based on the Australian Drinking Water Guidelines assumed water consumption, and estimates of actual consumption rates in the Australian population were undertaken for different age groups. The validity of assumptions underpinning screening assessments based on gross alpha and gross beta activity results and measurement of 226 Ra and 228 Ra were shown to be valid. The adolescent age group (14-18 y) was identified as a potential critical group for dose assessment where activity concentrations of 226 Ra and 228 Ra were elevated. Other radionuclides, 210 Pb, 210 Po, 234 U, and 238 U were shown to be significant contributors to overall committed effective dose in several water supplies; however, total doses in those supplies were well below the operational dose value of 0.3 mSv from the Australian Drinking Water Guidelines. Improved detection limits for 228 Ra could improve accuracy of dose assessments from drinking water.