Internal dose assessment of 148Gd using isotope ratios of gamma-emitting 146Gd or 153Gd in accidently released spallation target particles.

The pure alpha emitter 148Gd may have a significant radiological impact in terms of internal dose to exposed humans in case of accidental releases from a spallation source using a tungsten target, such as the one to be used in the European Spallation Source (ESS). In this work we aim to present an approach to indirectly estimate the whole-body burden of 148Gd and the associated committed effective dose in exposed humans, by means of high-resolution gamma spectrometry of the gamma-emitting radiogadolinium isotopes 146Gd and 153Gd that are accompanied by 148Gd generated from the operation of the tungsten target. Theoretical minimum detectable whole-body activity (MDA) and associated internal doses from 148Gd are calculated using a combination of existing biokinetic models and recent computer simulation studies on the generated isotope ratios of 146Gd/148Gd and 153Gd/148Gd in the ESS target. Of the two gamma-emitting gadolinium isotopes, 146Gd is initially the most sensitive indicator of the presence of 148Gd if whole-body counting is performed within a month after the release, using the twin photo peaks of 146Gd centered at 115.4 keV (MDA < 1 Bq for ingested 148Gd, and < 25 Bq for inhaled 148Gd). The corresponding minimum detectable committed effective doses will be less than 1 µSv for ingested 148Gd, but substantially higher for inhaled 148Gd (up to 0.3 mSv), depending on operation time of the target prior to the release. However, a few months after an atmospheric release, 153Gd becomes a much more sensitive indicator of body burdens of 148Gd, with a minimum detectable committed effective doses ranging from 18 to 77 µSv for chronic ingestion and between 0.65 to 2.7 mSv for acute inhalation in connection to the release. The main issue with this indirect method for 148Gd internal dose estimation, is whether the primary photon peaks from 146 and 153Gd can be detected undisturbed. Preliminary simulations show that nuclides such as 182Ta may potentially create perturbations that could impair this evaluation method, and which impact needs to be further studied in future safety assessments of accidental target releases.

Certified Reference Material IAEA-446 for radionuclides in Baltic Sea seaweed.

A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The (40)K, (137)Cs, (234)U and (239+240)Pu radionuclides were certified for this material, and information values for 12 other radionuclides ((90)Sr, (99)Tc, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (230)Th, (232)Th, (235)U, (238)U, (239)Pu and (240)Pu) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes.

External radiation doses from (137)Cs to frog phantoms in a wetland area: in situ measurements and dose model calculations.

For assessment of external radiation doses to frogs in a wetland area contaminated with (137)Cs, frog phantoms were constructed from polymethyl methacrylate (PMMA). The frog phantoms contained thermoluminescence (TL) chips and were used in situ at two study sites to measure doses. To test if higher doses are received by the sensitive skin of frogs, extra-thin TL chips were applied close to the surface of the frog phantoms. In addition, the measured doses were compared with those calculated on the basis of soil sample data from the wetland multiplied with dose-conversion coefficients from the US Department of Energy's RESRAD-BIOTA code and from the ERICA assessment tool. Measured doses were generally lower than those calculated to ellipsoids used to model frogs. Higher doses were measured at the frog phantoms' surfaces in comparison to inner parts at one of the two sites indicating that the frogs' thin skin could receive a higher radiation dose than expected. In the efforts to assure protection of non-human biota, in situ measurements with phantoms provide valuable dose information and input to dose models in site-specific risk assessments of areas contaminated with radionuclides.

Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea).

A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units.

Radiation risk and cost-benefit analysis of a paediatric radiology procedure: results from a national study.

A national study was performed to investigate radiation doses and associated risks to patients during X-ray fluoroscopy-guided small intestinal biopsies in the investigation of coeliac disease. Thermoluminescent dosemeters (TLD) and questionnaires were sent to 42 of the 43 paediatric departments in Sweden performing these biopsies. During the study period (2 x 3 weeks) 257 biopsies were recorded, representing about 10% of annually performed paediatric investigations. The results show that the absorbed dose during biopsy ranged from 0.04 mGy to 23.8 mGy (mean 1.87 mGy). The fluoroscopy time ranged from 2 s to 663 s (mean 60 s). The collective dose from the procedure amounts to 4.7 manSv year(-1). Thus, the annual excess cancer mortality, including severe hereditary effects, can be estimated at 0.6-0.7 cases per year. However, significant dose saving can be obtained by proper choice of sedation and biopsy equipment.

Uranium and thorium series radionuclides in drinking water from drilled bedrock wells: correlation to geology and bedrock radioactivity and dose estimation.

Natural radioactivity in drinking water from 328 drilled wells was studied in correlation to source parameters. Poor correlation to both aquifer geology and bedrock radioactivity was observed. Concentrations of 238U, 226Ra, 228Ra, 222Rn and 210Po in groundwater samples was in the ranges <0.027-5.3, <0.016-4.9, <0.014-1.24, 5-8105 and <0.05-0.947 Bq.l(-1) respectively. In about 80% of the sites the radon concentration exceeds the Nordic recommended exemption level for radon in drinking water and 15% of the sites exceed the action limit. The effective doses from ingestion were calculated and presented in association with geology. Doses due to ingestion ranged between 0.05 and 20.4 mSv.y(-1), where the average contribution from 222Rn amounted to 75%. In comparison, the effective doses from inhalation of indoor 222Rn ranged between 0.2 and 20 mSv.y(-1). The average contribution from inhalation of 222Rn in air to the total effective dose (ingestion+inhalation) was 58 +/- 22%, 73 +/- 18% and 77 +/- 16% (1 SD) for the age categories 1 y, 10 y and adults respectively.

Anthropogenic radionuclides in seawater of the Far Eastern Seas.

Large quantities of radioactive wastes have been dumped in the Far Eastern Seas by the former Soviet Union and the Russian Federation, and small amounts of radioactive wastes have been dumped by Japan and the Republic of Korea. In order to investigate the concentrations of anthropogenic radionuclides in the nine dumping areas, a second expedition was conducted in 1995 by Japan, the Republic of Korea, the Russian Federation and IAEA, following the first expedition in 1994. The results show that 137Cs, 90Sr and 239 + 240Pu concentrations in surface and bottom waters at dumping areas do not significantly differ from the values observed in background areas, and from historical values. There is no clear effect of possible contamination due to radioactive waste dumping. The concentrations and water column inventories of 137Cs, 90Sr and 239 + 240Pu in the Far Eastern seas are controlled by physical oceanic processes such as horizontal transport and biogeochemical processes such as scavenging.

Collective dose estimates by the marine food pathway from liquid radioactive wastes dumped in the Sea of Japan.

IAEA-MEL has been engaged in an assessment programme related to radioactive waste dumping by the former USSR and other countries in the western North Pacific Ocean and its marginal seas. This paper focuses on the Sea of Japan and on estimation of collective doses from liquid radioactive wastes. The results from the Japanese-Korean-Russian joint expeditions are summarized, and collective doses for the Japanese population by the marine food pathway are estimated from liquid radioactive wastes dumped in the Sea of Japan and compared with those from global fallout and natural radionuclides. The collective effective dose equivalents by the annual intake of marine products caught in each year show a maximum a few years after the disposals. The total dose from all radionuclides reaches a maximum of 0.8 man Sv in 1990. Approximately 90% of the dose derives from 137Cs, most of which is due to consumption of fish. The total dose from liquid radioactive wastes is approximately 5% of that from global fallout, the contribution of which is below 0.1% of that of natural 210Po.

Radiation dose at small intestinal biopsies in children: results of a national study.

The radiation dose delivered at small intestinal biopsies in children was investigated in a national study engaging 42 of 43 paediatric departments performing small intestinal biopsies. Measurements were performed with a thermoluminescence system at 257 biopsies. The results show a considerable variation of both duration of fluoroscopy (range 2-660 s; department medians) and radiation dose (range 0.1-14 mSv; department medians). The median of all absorbed doses was 0.69 mSv and the median duration of fluoroscopy 30 s. The observed variation cannot be explained by differences in X-ray equipment only. By optimization of all the technical conditions, such as X-ray equipment, biopsy device and method of sedation, at least a 6-fold reduction of radiation dose was obtained in one department. Especially if the operator is less experienced, it is worthwhile to optimize other factors to achieve the lowest possible radiation dose to the child. Children, coeliac disease, fluoroscopy, radiation dose, radiation risk, small intestinal biopsy.

Small intestinal biopsy in children with coeliac disease: measurement of radiation dose and analysis of risk.

To verify the diagnosis of coeliac disease in childhood, three consecutive small intestinal biopsies are performed under fluoroscopic control. To assess the amount of radiation dose absorbed during biopsy, dose measurements were performed both in patients and in a phantom model. These measurements were used for a theoretical assessment of cancer risk and shortening of life due to radiation exposure. The cancer excess lifetime mortality risk (CELMR) was 0.001, i.e. 1 case per 1000 children with a diagnosis of coeliac disease. The loss of life expectancy after three small intestinal biopsies in childhood was approximately 15% of the risk due to lifetime exposure to natural background radiation. These results should be compared with the reported increased risk of malignancy for undiagnosed coeliac disease in adult age. Although the excess risk of the biopsies was small, all efforts should be made to use a technique and equipment giving the least radiation dose.

Investigation of aerial dispersion of radioactive dust from an open-pit uranium mine by passive vinyl collectors.

Detailed investigations of the aerial dispersion of radioactive dust from the biggest open-pit U mining and milling operation in Australia were carried out. Spatial distributions of the long-lived radionuclides of 238U series and their origin, i.e., mining and milling operations vs. natural background radiation, have been studied. Horizontal flux, dry deposition, and ground resuspension of the radionuclides were investigated along a 50-km transect in the direction of the prevailing monsoonal winds in the region. The study was performed by means of unconventional "sticky vinyl" passive dust collectors, occasionally supported by high-volume air filter samplers. The data from the flux measurements show an inverse square to inverse cubic dependence, and the dry deposition exhibits an inverse square dependence, of radionuclide load vs. distance. The pit has been the predominant contributor of long-lived U series radionuclides to the environment within the radius of several kilometers from the operations. An aerial dispersion computer code (LUCIFER), based on a Gaussian plume model, was developed for the project. Experimental data were used as the code input data. Good agreement between the measured data and the normalized computed results was obtained.