Abstract
The new German Radiation Protection Ordinance contains for the first time a systematic framework of regulations protecting workers and the public against radiation exposures from residues of industrial and mining processes containing enhanced levels of naturally occurring radionuclides (TENORM). These regulations will satisfy the requirements of the European Council Directive 96/29/EURATOM and serve as a common basis for the radiation protection activities of the German states in this field. The consideration of exposures from materials containing naturally occurring radionuclides gains on this basis an increased level of significance within the German radiation protection efforts.
The overall goal of the new regulations is to keep the additional effective dose for the population from the recycling and disposal of TENORM below 1 mSv/a. In order to achieve this objective, companies in which such residues arise have to carry out representative measurements of activity concentrations in these materials. If exemption levels defined in the new regulations are exceeded, restrictions on the recycling and disposal come into effect. These exemption levels are nuclide specific and distinguish between material types and different recycling and disposal options. This specific definition of exemption criteria serves the goal to minimise the number of companies and the amount of residues affected by the new regulations to the extent possible, focussing the efforts of operators and regulators to those materials having the potential to actually cause radiation exposure problems.
The specific exemption criteria were derived on the basis of an analysis of typical amounts and activity concentrations of industrial and mining residues with enhanced radioactivity contents in Germany. In a second step, practically applied options for the recycling and disposal of these materials were investigated. On this basis, generic scenarios for the radiation exposure of the workforce and the public were defined and doses were estimated. All relevant pathways including possible long term effects (ground water) were considered in these analyses. Based on the 1 mSv/a criterion, a catalogue of relevant materials, potentially requiring radiation protection measures, was developed. For these materials the practically applied recycling or disposal options were grouped into categories, for which specific exemption levels were derived. The derivation of these criteria was based on realistic estimates of radiation exposure, for example taking into account the dilution of the residues with other materials in technological processes or during the disposal in landfills.
The residues subject to the new regulations mostly arise in large quantities over extended periods of time. This leads to significant variations of radionuclide concentrations depending on feed materials and process parameters. To carry out representative measurements without the necessity of taking a too large number of samples, therefore, requires an adequate measurement strategy. Particular aspects to be considered are uncertainties of the measurements themselves and the heterogeneity of the residues. In addition, the measurement strategy has to be compatible with diverse situations in the different industries affected. The framework developed for designing individual strategies for the various industries and types of residues satisfies these requirements and can also provide guidance for measurement campaigns in other areas.
The paper outlines the general situation with regard to TENORM in Germany. The main streams of residues and options for their recycling or disposal are described. On this basis, scenarios used for the radiological evaluation are defined and examples for resulting radiation exposures are given. The exemption levels derived from this analysis are discussed. Finally, the framework for the design and implementation of an adequate measurement strategy is outlined.
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