Radium equivalent activity in the light of UNSCEAR report.

Radium equivalent activity (Ra ( eq )) has been in practice for the last 40 years for the assessment of radiological hazard of radioactivity in environmental materials. The in-practice model for the calculation of the Ra ( eq ) has been critically reviewed in the light of the UNSCEAR 2000 report. Annual effective dose (E) values of (232)Th and (40)K were found to be not equal to that of (226)Ra derived from the activity concentrations of these radionuclides used in the expression for the Ra ( eq ). Therefore, a modified model has been proposed for the determination of the Ra ( eq ) for outdoor external exposure to gamma rays. The relation between the E and Ra ( eq ) has been explored. It is recommended that while describing the radiological hazard of the materials containing radioactivity, there should be no need to calculate the Ra ( eq ) if the E has already been determined or vice versa.

Radon survey in Montenegro - A base to set national radon reference and "urgent action" level.

The first nationwide indoor radon survey in Montenegro started in 2002 and year-long radon measurements with CR-39 track-etch detectors, within the national grid of 5 km × 5 km and local grids in urban areas of 0.5 km × 0.5 km, were performed in homes in half of the country's territory. The survey continued in 2014 and measurements in the rest of the country were completed at the end of 2015. The 953 valid results, obtained in the national radon survey, give an average radon activity concentration in Montenegrin homes of 110 Bq/m3. Assuming a log-normal distribution of the experimental results, geometric mean GM = 58.3 Bq/m3 and geometric standard deviation GSD = 2.91 are calculated. However, normality tests show that the experimental data are not log-normal, and that they become closest to a log-normal distribution after subtracting from them radon concentration in the outdoor air of 7 Bq/m3, which is theoretically calculated. Such a transformed distribution has GMtr = 46.7 Bq/m3 and GSDtr = 3.54. The estimations derived from positing a priory that the experimental results conform to a log-normal distribution underestimate the percentage of homes with radon concentrations at the thresholds of 300 Bq/m3 and above, which is better estimated by using GMtr and GSDtr. Based on the results of radon survey, a new national radon reference level of 300 Bq/m3 and an "urgent action level" of 1000 Bq/m3 are suggested, with estimated fractions of the national dwelling stock above these levels of 7.4% and 0.8% respectively. Fractions of homes with radon concentrations above the suggested levels are also estimated for each of the 23 municipalities in Montenegro, using appropriate GMtr and GSDtr. The six municipalities which have more than 10% of homes with radon concentration above 300 Bq/m3 are recommended as radon priority areas.

Radiological aspects of the usability of red mud as building material additive.

Several researchers have examined and achieved favourable results in connection with the building industry's use of red mud extracted in large quantities from the processing of bauxite. These days more and more precedence is being given to limiting the radiological dose to the population. In this study carried out in Hungary, the use of red mud, bauxite, and clay additives recommended for the production of special cements, were examined from a radiological aspect. (226)Ra and (232)Th activity concentrations measured in Hungarian bauxite, red mud and clay samples were significantly similar with the levels for such raw materials mentioned in international literature. Taking radiation protection aspects into consideration, none of these products can be directly used for building construction. Taking Hungarian and international values into consideration, a small amount of red mud, not exceeding 15% could be used for brick production, for example as a colouring material. However, beyond this amount the standards for building materials would not be met. For the production of cements an even stricter limit needs to be determined when both bauxite and red mud are used.

Challenges in harmonising controls on the radioactivity of building materials within the European Union.

Possibilities for harmonising controls on the radioactivity of building materials within the European Union are being discussed in a Working Party on Natural Radiation Sources established by the Article 31 Group of Experts (Euratom Treaty). The Working Party is preparing a document to aid the Article 31 Expert Group and the European Commission in considering possible recommendations and technical guidance to the Member States for the implementation of the new Basic Safety Standards Directive concerning the radioactivity of building materials. The discussions in the working party have demonstrated several challenges in the possible harmonisation of controls, many of them arising from some significant differences in national circumstances.

A review of countermeasures to reduce radioiodine in milk of dairy animals.

The most effective countermeasure for radioiodine contamination of milk is to provide dairy animals with uncontaminated feed, with the added advantage that it will be effective for other radionuclides in the fallout. Another effective response is to process the milk into storable dairy products for an appropriate length of time to allow for physical decay. The use of additives given to ruminants to reduce radioiodine in milk is an alternative countermeasure which could be effective. Stable iodine administration is a practically feasible option which has the potential to reduce radioiodine levels in milk by at most a factor of three. Stable iodine supplementation should be at sufficiently high rates to be effective (and at least 1 g d-1 for dairy cows), particularly for ruminants already receiving high amounts of iodine in the diet. Currently available data are inadequate to recommend a suitable stable iodine administration rate for different species of ruminants. Other compounds, such as perchlorate and thiocyanate, also reduce the transfer to radioiodine to milk (and thyroid). Some of these compounds seem to be potentially equally as effective as stable iodine. However, currently there is inadequate information on their effectiveness and possible toxicity to both ruminants and humans for these compounds to be considered as suitable countermeasure additives.

Environmental radiation protection: philosophy, monitoring and standards.

The Euratom Treaty confers important powers to the European Commission with regard to monitoring and assessment of levels of radioactivity in the environment and discharges with effluents (Articles 35-37 of the Euratom Treaty). Current developments in the area relate to harmonised reporting of environmental data and to harmonisation of effluent monitoring data. Both developments relate to the requirement under the new Basic Safety Standards (BSS) for a realistic assessment of population exposure. Guidance to this effect is being prepared by the Article 31 Group of Experts. In the context of Article 36 intercomparison exercises for radionuclides measurements in environmental samples are organised. New challenges for environmental monitoring result from the requirement under the BSS to regulate also industries processing NORM materials. Also the international move towards extending the scope of environmental radioactivity to the protection of biota opens new perspectives.

Determination of self-absorption corrections for gamma analysis of environmental samples: comparing gamma-absorption curves and spiked matrix-matched samples.

Accurate determination of the massic activity of gamma-emitting radionuclides in environmental samples, particularly sediments and soils, cannot be achieved without taking into account sample self-absorption. The extent of self-absorption in the sample will depend on a number of factors including sample composition, density, sample size and gamma-ray energy. The preferred method for correcting for this effect is to use spiked or natural matrix reference materials that match each sample type to be analysed. However, for laboratories that must measure a wide variety of sample matrices this method is too costly and time-consuming. Another technique commonly used is to make direct gamma-ray transmission measurements for each sample. This method, while more practical, still requires a minimum of three measurements to be made for each sample analysed. A more convenient method is to prepare sets of gamma-absorption curves. This approach involves making a series of direct transmission measurements for samples of varying densities but similar type. Sets of matching samples, both spiked and unspiked, were prepared and density correction factors determined using the direct transmission method and the spiked sample approach. It was found that, for soil and sediment samples, these two methods typically differed by 5-9% for higher energy gamma rays and by 12-15% for the 59.54 keV 241Am peak. Gamma-absorption curves were also derived and, for the admittedly limited dataset, 95% confidence intervals of +/-7% for the curve generated using the spiked samples method were obtained.

Development of the NIST bone ash standard reference material for environmental radioactivity measurement.

The bone ash standard reference material (SRM), a blend of 4% contaminated human bone and 96% diluent bovine bone, has been developed for radiochemical method validation and quality control for radio-bone analysis. The massic activities of 90Sr, 226Ra, 230Th, 232Th, 234U, 235U, 238U, 238Pu, (239 + 240)Pu and (243 + 244)Cm were certified using a variety of radiochemical procedures and detection methods. Measurements confirmed undetectable radionuclide heterogeneity down to a sample size of 5 g. thereby implying adequate blending of particulate materials with dilution factors of up to 17,900. The results among most of the intercomparison laboratories and their methods were consistent. Disequilibrium was observed for decay chains: 234U(0.67 mBq/g)-230Th(0.47 mBq/g)-226Ra(15.1 mBq/g)-210Pb(23 mBq/g)-210Po(13 mBq/g) and 232Th(0.99 mBq/g)-228 Ra(6.1 mBq/g)-228Th(7.1 mBq/g). The disequilibria were the results of mixing occupationally contaminated human bone with natural bovine bone and the fractionation during internal biological processes. The massic activity of 210Pb, 228Th and 241Am were not certified because of insufficient 228Ra and 241Pu data and lack of knowledge in how 222Rn and its daughters will be fractionated in the SRM bottle over time.

Measurement of 90Sr in bone ash.

Bone is a critical organ for the accumulation of many radionuclides, including 90Sr. A bone ash has been prepared by NIST to become a standard reference material and the assaying of the 90Sr activity concentration is reported. A radiochemical procedure, based on extraction chromatography using a crown ether, has been developed to separate Sr from the bone ash. The natural Sr content of the bone ash has been determined by isotope dilution inductively coupled plasma mass spectrometry. The 90Sr activity concentration has been measured by low-level liquid scintillation counting.

Metrological capability of the Brazilian laboratories of analyses of radionuclides in environmental samples.

The metrological capability of 24 Brazilian laboratories of radionuclide determinations in environmental samples was analysed for purposes to establish requirements for accreditation of laboratory for each radionuclide. For each type of analysis, the range of activity per unit mass or volume, the range of the reference value and its correspondent uncertainty were described. The accuracy was established using the statistical criteria of USE.P.A. for the laboratory performance classification. The precision of the analyses, expressed by its variation coefficient of the laboratory determinations, was classified in intervals of 5%. The data base was constituted by 3013 results of analyses obtained in 28 intercomparison runs performed from 1991 to 2000, for K, Th, Unat, gross alpha, gross beta, and other 27 radionuclides, in matrices of water, soil, vegetation, air filter and milk. The quality criteria established were the variation coefficient less than 5% and good performance in intercomparison runs. Results included from 5% to 10% are also considered, for special types of matrices and radionuclides.

Standard reference materials for thorium analysis.

Reference materials (RMs) are used in analytical measurements for several purposes--to develop and validate analytical measurements, as quality control indicators and for calibration. It is therefore essential that suitable reference materials are available. Because thorium is usually found in very acid-resistant, mineral phases, this becomes even more critical when techniques such as ICP-MS are used, which require complete sample digestion. This paper gives an overview of the reference materials that are currently available for thorium (232Th and other thorium isotopes) in various matrices, sources and indicative costs. The IAEA database is identified as a particularly useful source of information, and the website address is: http://www.iaea.org/programmes/nahunet/e4/nmrm/index.htm A brief summary of the discussion held at the '1st European Workshop on the Analysis of Thorium in Workplace Materials', regarding reference materials, is given at the end of the paper. A general need for new RMs, specifically for workplace materials, was identified as a priority.

Current status of internal dosimetry in Lithuania.

After Lithuania regained independence, the legal basis for existing radiation protection was modified radically according to the IAEA, ICRP recommendations and the requirements of legislation of the European Community. The legal basis for internal dosimetry and a functioning system of assessment of exposure to intake of radionuclides have been created in the Radiation Protection Centre (regulatory authority in radiation protection). Direct and indirect measurements of concentrations of radionuclides are used for the assessment of internal doses of workers and the public.

Preparation of spiked grass for use as an environmental radioactivity reference material.

Measurement of radionuclides from environmental samples includes a wide variety of matrix compositions and densities. To improve the traceability of environmental monitoring, LNE-LNHB intends to produce mixed γ-ray reference materials with a known mass activity and a composition as representative as possible of real environmental samples. This paper describes the preparation and characterization of a low density treated grass matrix spiked with mixed γ-emitters. This material was used in a proficiency test exercise whose results are presented.

First participation by the NMISA in a low-level comparison: CCRI(II)-S9 exercise.

The NMISA Radioactivity Standards Laboratory participated in the CCRI(II)-S9 inter-comparison of the measurement of the activity concentration of (137)Cs and (40)K in rice material, piloted by the KRISS. The paper describes the equipment used, the measurement set-up and data analysis. The efficiency of the detector for (137)Cs and (40)K was determined by comparison against a spiked standard solution, and Monte Carlo simulations performed to estimate the difference in γ-ray escape probability between the solution standard and starch (as an approximation for milled rice) due to attenuation disparities. The uncertainty budget was estimated rather conservatively, since these were the first low-level measurements performed by the NMISA using an HPGe detector.

Regulation of radiation pollution: its possible usefulness in strategy for intervention against chemical mutagens.

Over the last 25 years, a large amount of work has been carried out in the field of safety with regard to ionizing radiations. This has resulted in the establishment of norms of security which have been accepted in most countries. These norms are not perfect; they are constantly reviewed and, from time to time, revised; but, such as they are, they are of tremendous usefulness. These standards may serve as a model of what must be achieved in the field of pollution by chemical mutagens. Further, the norms already in force for radiation may serve as a reference for the establishment of similar norms for the major environmental mutagens. It is not possible to assign a specific factor of equivalence with radiation (rad-equivalence) to a given chemical pollutant; but it is possible to establish point-equivalences with regard to well-defined biological systems under well-defined conditions. When they are accurately determined, such point values may be useful and sensible. In this area, as with radiation, it is impossible to find perfect solutions; however, approximate solutions can be arrived at that would already represent a reat progress with regard to the present situation, and which could later be improved as work in the field allows.

Uranium and thorium in urine of United States residents: reference range concentrations.

We measured uranium and thorium in urine of 500 U. S. residents to establish reference range concentrations using a magnetic-sector inductively coupled argon plasma mass spectrometer (ICP-MS). We found uranium at detectable concentrations in 96.6% of the urine specimens and thorium in 39.6% of the specimens. The 95th percentile concenetration for uranium was 34.5 ng/L (parts per trillion); concentrations ranged up to 4080 ng/L. Thorium had a 95th percentile concentration of 3.09 ng/L; concentrations ranged up to 7.7 ng/L.

[Consequences of the latest Euratom directive 96/29 ("basic standard") regarding radiotherapy]. / Auswirkungen der neuen Euratom-Richtlinie 96/29 ("Grundnorm") im Bereich der Strahlentherapie.

AIM: The Council Directive 96/26 will be brought into force by the Member States of the EC until the year 2000. What practical consequences on both mounting and holding radiotherapeutical facilities should be considered? METHODS: Regarding the Council Directive, facts on workers' actual occupational exposure in medicine and representative calculations on structural shielding the consequences will be evaluated. RESULTS: Increasing both total number of occupationally exposed workers and number of Category A workers but also enforced structural shielding should be expected. Working in any protected area during pregnancy will be strictly prohibited now. CONCLUSIONS: With respect to the generally sufficient structural shielding no restrictions for existing radiotherapeutical facilities are to be expected. But it is emphasized to carry out further mountings on base of the latest Council Directive 96/26 Euratom.