Band 73, Heft 3

Since 2001, the protection against natural radiation is implemented in the German Radiation Protection Ordinance. Water supply facilities are now obliged to estimate the radon exposure of their staff. In 75 water supply facilities in Bavaria, Germany, radon exposures above the action limit of 6 mSv per year were determined. In these facilities the radon exposure has to be continuously monitored. By the proposal of the Bavarian Environment Agency (LfU), this should be done by continuous wearing of personal track-etch detectors, that are changed every three months. The results are sent to the LfU and reported to the central German dose register. Because of measuring periods of three months a high radon exposure that could probably exceed the annual limit of 20 mSv can be recognised at an early stage and immediate protection measures can be taken. In collaboration with the University of Regensburg remedial strategies for the permanent reduction of the radon exposure have been developed. The exposure is effectively reduced by reducing the time spent inside the units as much as possible. A very effective way to reduce the radon concentration inside buildings and hence the radon exposure is to blow fresh air directly into the work place of the staff with stationary or mobile devices. An alternative way to reduce the indoor air concentration is to avoid any transfer of radon polluted air exhausted from purification tanks to indoor air. For a long lasting success of the remedial measures a work instruction was developed by the LfU. All plants, their mean radon concentration and the measures to be taken have to be stated there.

This paper discusses a simple phenomenological model of TENORM formation. The model is based on a mass and activity balance in an industrial process. It characterises the radionuclide enrichment of a residue in relation to the input materials according to three parameters (mass transfer factor MTF, activity transfer factor ATF and enrichment factor EF). The model shows that high enrichment is only possible if mass transfer into the residue is low. By analysing data from several real industrial processes, the co-precipitation of dissolved radium with barium salts (EF about 10 4 ), the volatilisation of lead and polonium in thermal processes (EF about 300) and the combustion of fuels (EF 10–100) are identified as very effective enrichment processes. However, in real industrial processes the specific activity of residues may be influenced by admixtures of masses after the decisive step of radionuclide redistribution. Therefore, focus should be placed on the identification and characterisation of elementary processes of TENORM formation. Several such processes are discussed in this paper.

The German Radiation Protection Commission has recommended “Principles and Methods for the Consideration of Statistical Uncertainties for the Determination of Representative Values of the Specific Activity of NORM wastes” concerning the proof of compliance with supervision limits or dose standards according to § 97 and § 98 of the Radiation Protection Ordinance, respectively. The recommendation comprises a method ensuring the representativeness of estimates for the specific activity of NORM wastes, which also assures the required evidence for conformity with respect to supervision limits or dose standards, respectively. On the basis of a sampling survey, confidence limits for expectation values of specific activities are determined, which will be used to show that the supervision limit or the dose standard is met or exceeded with certainty, or that the performed sampling is not sufficient for the intended assessment. The sampling effort depends on the type and the width of the distribution of specific activities and is determined by the position of the confidence interval with respect to the supervision limit or of the resulting doses with respect to the dose standard. The statistical uncertainties that are described by confidence limits may be reduced by an optimised extension of the sample number, as far as necessary.

Discharges of radium-carrying mine waters from hard coal mining in the area of the Fossa Eugeniana and the Rheinberger Altrhein in Germany have caused elevated radioactivity in sediments and soils. Extensive measurements of the ambient dose rate revealed some small area contaminations as well as a larger one in a nature protection area at the Rheinberger Altrhein. For the evaluation of the potential radiation exposure investigations of the activity concentrations of river sediments, soils, and biological materials were performed. The potential exposure of members of the public was modelled on the basis of the German Guidelines for the Calculation of Radiation Exposure due to Radioactivity from Mining Activities. In the assessment the present situation as well as its possible future development was considered.

The investigation of the radiation situation is an essential part of preparing the remediation of the formerly abandoned Wismut sites. If the exposure is relevant, then the exposure pathway “inhalation of radon/radon daughters” plays the dominant role. Therefore, the development of a straightforward approach suitable for the evaluation of the involved radon situation is one of the most important tasks. It has to include the whole chain beginning with the characterization of the relevant exposure situation and ending up with the identification of remedial options. For that purpose a new technique of visualizing the radon flux from the waste rock dumps has been developed. The specific conditions at formerly abandoned Wismut sites will be demonstrated and the remediation solutions envisaged to reduce the radon flux will be explained.

The area dose rate (ADR) of the natural radiation is subject to strong fluctuations caused by meteorological influences. Rain in particular can strongly increase the local dose rate values on the earth's surface for a short time because radon progenies can be washed out of the atmosphere and accumulated on the Earth's surface. The Physikalisch-Technische Bundesanstalt (PTB) has reference measuring facilities at its disposal which allow permanent measurement of the individual components of natural ambient radiation. Results of long-term measurements and their correlation to weather data, seasonal fluctuations, but also to solar activity, are presented. In addition to the quantification of the radiation level caused by photons, the contributions of the charged components of cosmic radiation (myons and electrons) as well as neutron radiation were measured. The terrestrial component of natural ambient radiation results from the radionuclides in the soil and in the air. In order to determine which nuclides cause the corresponding dose rate, the in-situ-gamma spectrometry method is especially suited. Measurements of the variation of the nuclide-specific photon flux as a function of the precipitation prove that the activity concentrations of radon progenies have an important influence on the local dose rate.

The determination of naturally occurring radionuclides in the environment is a complex problem. Particularly the optimization of the analysis methods is very important, while the choice of the method influences the financial and personnel resources, as well as the quality of the results. This work is prepared from a working group within the working group(suggest instead use Research Group) “natural radioactivity” of the German-Swiss radiation protection association (FS). It is a recommendation for clients of existing laboratories, as well as new or renovated laboratories, which order measurements. This article shows some excerpts of the full work.

In Europe and Germany administrative regulations exist for the surveillance of the Total Indicative Dose of water supplied for human consumption. This parameter, which can not be analysed directly, has to be calculated using nuclide specific activity concentrations, age-specific dose conversion factors and consumption rates. Available calculation methods differ regarding the used radionuclides, consumption rates and whether they use age specific dose conversion factors or not. In Germany, administrative guidelines for the determination of the Total Ingestion Dose are still not available. From a large number of water sample analyses, a graded practical concept for the determination of the ingestion dose is derived, which considers radiological, analytical and hydrochemical aspects as well. Finally, it is suggested to consider mineral water in the same manner as drinking water.

The implementation of radon mitigation and precaution standards needs continuously scientific attendance and research networking on international level. Otherwise the radon issue could degrade easily to a simplified techno-economical exercise without sustainable results in public health. In this paper the radon investigations in Austria which have been carried out in the last 20 years and the applied methods and derived standards for mitigation and precaution at home and workplaces are discussed. Future strategies, scientific and social necessities to solve the radon problem are outlined comprehensively. The agreed and proposed future research objectives and cooperations in Austria that seem absolutely necessary are discussed in consideration of the medium-term perspective of the European radiation protection.

Measurements of indoor radon activity concentration have been carried out in more than 10 000 dwellings in different regions of Germany. The statistical correlations between geology, building ground, indoor radon and the house characteristics were investigated. The geographical location – and therefore the geological setting – can be used as a proxy for both region-specific geological properties and building characteristics. Together with different variables of house type and living habits it significantly contribute to the explained variance for both ground floor and basement radon activity concentrations. Soil gas and indoor radon activity concentrations are connected by a transfer factor. The study has shown, that this factor can vary depending on regional differences in building characteristics, especially between the western and eastern part of Germany. Radon risk prediction maps for radon in houses based on the German soil gas map and the regional distribution of radon transfer, indicating the probability of exceeding indoor threshold values, can be designed. They can be used as a tool for indoor radon prediction, especially in regions without a sufficient number of indoor radon data.

Since the amendment of the German Radiation Protection Ordinance in the year 2001 special workplaces with increased exposure due to natural terrestrial radiation have been subject to legal regulations. After the Radiation Protection Ordinance came into force the Bavarian Environment Agency informed all water supply facilities, breweries, dairies, mineral water manufactures, operators of underground workplaces and radon spas that the annual radon exposure of their staff has to be estimated. In Bavaria approximately 3330 companies with workplaces with exposure to radon were investigated. Herein the water supply facilities represented the largest group with 2550 companies. In about 96 % of all investigated companies the radon exposure of the staff is below the action level of 6 mSv per year. In 75 water supply facilities and two mines the radon exposure of the staff exceeded the action level (6 mSv/a) or the annual limit (20 mSv/a). Workplaces with increased exposure due to uranium and thorium are of secondary importance in Bavaria. Within the scope of a research project 13 companies were found, that still use thoriated welding electrodes. Only a few facilities use thoriated mantles, thorium alloys or natural thorium and uranium. The effective dose of all examined workers was below the action level of 6 mSv per year.