The 1986 Chernobyl accident resulted in radionuclide contamination (dominated by 137 Cs) across large areas of Belarus. Consequences of this accident continue to affect Belarus long after initial contamination, which in turn has placed strain upon social, economic and political infrastructures. One method to reduce this strain and remediate contamination is to return areas of land no longer posing a risk, back to an appropriate use. As a method of remediation, this requires regular and accurate monitoring of the landscape at which existing ground based techniques have not been entirely well-suited. Remote sensing, specifically the use of imaging spectrometry offers the potential to monitor the Belarusian landscape at opportune spatial and temporal resolutions. Vegetation has been shown to be an important agent in the cycling of radioactive isotopes in the environment and therefore a useful indicator of radionuclide contamination. This pilot research has focused on assessing the spectral response from Pinus sylvestris (dominant on the Belarusian landscape) at differing ages and with varying levels of 137 Cs contamination. Continuum removal was applied to the spectra showing that for older forests (c. 35 years) significant spectral differences between low and high contaminated sites exist at wavelengths that are causally related to foliar biochemicals. This was not the case for young forests (c. 15 years) where no significant differences were found. The results signify the potential to infer contamination levels from spectra of forests, partitioned by age, thus indicating the possibility of using imaging spectrometry to monitor radionuclide contamination, a possibility warranting further investigation.
The uncertainty in gamma spectroscopic activity measurements is investigated for soil containing hot particles. A radioactivity inhomogeneity uncertainty needs to be taken into account, which depends on the density of hot particles in the sample geometry, the distribution of their activities, and the specific source-detector geometry. The maximum activity error due to hot particles in our sampled Chernobyl soil with a 137Cs activity of 100 kBq kg(-1) soil was 6% for our source detector geometry. The methodology presented might have a practical application in nuclear power plants to detect hot particles in a large quantity of dust or dirt. The number of hot particles present can be estimated if the activity of all particles is assumed to be similar. With this assumption 100 g of the investigated soil sample would contain about 500 hot particles with an approximate activity of 20 Bq each.
This study re-examines the risk to health from radium ((226)Ra) dial watches. Ambient dose equivalent rates have been measured for fifteen pocket watches giving results of up to 30 μSv h(-1) at a distance of 2 cm taken with a series 1000 mini-rad from the front face (arithmetic mean ambient dose equivalent for pocket watches being 13.2 μSv h(-1)). A pocket compass gave rise to a similar ambient dose equivalent rate, of 20 μSv h(-1), to the pocket watches, with its cover open. Eighteen wristwatches have also been assessed, but their dose rates are generally much lower (the arithmetic mean being 3.0 μSv h(-1)), although the highest ambient dose equivalent rate noted was 20 μSv h(-1). A phantom experiment using a TLD suggested an effective dose equivalent of 2.2 mSv/y from a 1 μCi (37 kBq) radium dial worn for 16 h/day throughout the year (dose rate 0.375 μSv h(-1)). For this condition we estimated maximum skin dose for our pocket watches as 16 mSv per year, with effective doses of 5.1 mSv and 1.169 mSv when worn in vest and trouser pockets respectively. This assumes exposure from the back of the watch which is generally around 60-67% of that from the front. The maximum skin dose from a wristwatch was 14 mSv, with 4.2 mSv effective dose in vest pocket. Radium ((226)Ra) decays to the radioactive gas radon ((222)Rn), and atmospheric radon concentration measurements taken around a pocket watch in a small sealed glass sphere recorded 18,728 B qm(-3). All watches were placed in a room with a RAD7 real-time radon detector. Radon concentration average was 259±9 Bq m(-3) over 16 h, compared to background average over 24h of 1.02 Bq m(-3). Over 6 weeks highs of the order of 2000 Bq m(-3) were routinely recorded when the heating/ventilation system in the room was operating at reduced rates, peaking at over 3000 Bq m(-3) on several occasions. Estimates of the activity of (226)Ra in the watches ranged from 0.063 to 1.063 μCi (2.31 to 39.31 kBq) for pocket watches and from 0.013 to 0.875 μCi (0.46 to 32.38 kBq) for wrist watches. The risk from old watches containing radium appears to have been largely forgotten today. This paper indicates a health risk, particular to collectors, but with knowledge and appropriate precautions the potential risks can be reduced.
The Chernobyl accident in 1986 resulted in the widespread identification of the post-accident presence of radioactive (or ‘hot’) particles across large areas of Eastern and Central Europe. Such particles arise from direct deposition and also from condensation and interactions on particle surfaces during and following the deposition of soluble fallout. Identification of the presence and nature of hot particles is necessary in order to determine the long-term ecological impact of radioactive fallout. This paper describes several techniques for the identification and characterization of hot particles in soil samples from Belarus. In addition to new results from the use of gamma spectrometry, we include two novel instrumentation approaches that have been developed and applied to Chernobyl fallout-contaminated soils. The first, ‘differential’ autoradiography, utilizes a photographic film sandwich to characterize the nature of the ionizing radiation emitted from samples. In this paper we show that differential autoradiography can not only identify hot particle presence in soil, but can also determine the dominant radionuclide in that particle. The second approach, sector field ICP-MS (ICP-SFMS), can provide rapid, high-precision determination of the actinides, including the transuranic actinides, that characteristically occur in hot particles originating from weapons fallout or fuel matrices. Here, ICP-SFMS is shown to yield sufficiently low detection limits for plutonium isotopes (with the exception of 238Pu) to enable us to confirm negligible presence of plutonium in areas outside the Chernobyl exclusion zone, but with high levels of fission-product contamination.
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