The European Directive applies to all practices that involve a risk from ionising radiation from an artificial source and special cases from natural sources. The German Ordinance to implement it covers the following main sections:
• General regulations.
• Protection of man and environment against radioactive substances or ionising radiation.
• Protection of man and environment against natural radiation due to work activities.
• Protection of the consumer against the addition of radioactive substances to products.
• Common requirements.
Issues relevant to nuclear plant operation cover new dose limits, other reference levels, the clearance of very low activity materials to be met by utilities during operation or decommissioning, and additional protection measures for outside workers. Compared to previous regulations, there is far more emphasis given to the need for changes in organisation, planning and personnel management.
There are new dose limits, both occupational limits for personnel and limits for members of the public. For the public, the effective dose limit has been set at 1mSv/year. Previously, the general limit was 1.5mSv/year.
There are also dose limits laid down for operational air and water discharges from nuclear facilities. These require the effective dose to the public to be kept below 0.3mSv/year, with additional limits set for organ doses. These limits have to be met outside the facilities area.
The area of the facility is not necessarily limited by the site fence. It is defined as the developed site where the facility is located. This is the area where the licensee has responsibility for radiation protection, and where the licensee can limit access and residence time. Theoretically, if limits for liquid and gaseous releases were exhausted, and if the utility could not limit the time period during which peoiple were affected, direct radiation from the site should be 0.4mSv/year, with a mean dose rate of 0.05µSv/h. This is not the case for operating facilities.
The new regulations state that if there is no reliable data for the residence time, then a steady stay over the whole year (8760 hours) is assumed. In practice, higher dose rates are possible by considering realistic residence times. For supervised and controlled areas, a working/residence time of 40 hours a week and 50 weeks per year is assumed, resulting in a theoretical time of 2000 hours, if no other conditions can be proven. To meet the limits at the site boundary, in some cases, additional measures may be necessary, such as improved shielding in critical areas or special planning.
For companies sending personnel to work as occupationally exposed persons in nuclear facilities (outside workers or contracted personnel), the reduced 1mSv/year limit also implies more clarification, and may have consequences. Companies providing personnel require authorisation if the effective dose of the person may exceed 1mSv/year. Dose limits and radiation protection measures for these people apply in the same way as for utility personnel. The company has to equip each worker with a legal dosimeter and a registered radiation passport for all exposures.
The borderline of the site area is considered to be between members of the public and the people exposed by their activities on site. The new Ordinance applies lower thresholds for areas with potential exposures or dose rates as defined in the Tables. The Figure on p22 gives a schematic presentation of the areas defined on site and its integration with company and public area.
Reducing the limit for the controlled area should not imply severe modifications in constructive areas of the plants, as normally the borders of the controlled area are not limited by the dose rate, but by constructive boundaries. There are, however, areas where these reductions have to be considered, such as areas on site with temporary storage of radioactive waste, which may need some limits due to higher dose rate.
For areas inside the company’s influence, care should be taken that, outside controlled areas, doses higher than 1mSv/year will be detected. In addition, access to areas with continuous dose rates >0.5µSv/h outside the controlled area will be restricted to ensure that the dose limit of 1mSv can be met for residence times of 2000h. When work is carried out in these areas, the dose has to be assessed by wearing dosimeters or equivalent measures.
Clearance for re-use, recycling and disposal
The new Ordinance lays down, for the first time in Germany, a complete set of data to regulate the release of radioactive material. The Ordinance clarifies the procedures, levels and conditions and, to some extent, it aims to simplify the measures for handling slightly radioactive material.
Criteria for the release of slightly contaminated or activated material out of regulatory control have been defined in the new Ordinance in compliance with the EU basic safety standards. Related clearance values for different ways of recycling or re-use and disposal have been integrated into the Ordinance. It considers possible pathways that may be taken by unconditional use of the material, or the conditional use of material by disposal in a waste disposal site, incineration, or conditional recycling by melting. This consideration and data are also related to the contamination of work-places, clothes and material on site and the transfer of such material from the controlled area for use outside.
For solid material with measurable surfaces, levels have to be met for surface contamination and specific contamination. The measurement of materials with large surfaces is a significant undertaking. Material properties may cause problems: a low specific weight material, such as insulation, may have a higher specific activity and a higher volumetric relation for the same activity than a high specific-mass material.
Special measuring chambers of different sizes can check the specific activity levels of the material, for operating plants and for plants being decommissioned. Experience has been gained in the release of buildings and of soil areas by contamination monitoring. In situ contamination monitoring of large areas and of contaminated soil by specific activity measurements have also been developed.
There are additional conditions for the release of radioactive material. These are split into general conditions and those linked to different release pathways. Among the conditions:
• If the surface of the material allows a surface contamination measurement, measurements must show that the surface contamination limits and the activity concentration limits are met.
• The averaging mass for the measurement of the activity concentration must not be significantly greater than 300kg.
• The averaging area for contamination measurement may be up to 1000cm2.
• If several radionuclides are present, a summation formula for the normalised contributions shall be applied for the specific activity and the surface contamination; nuclides need not be considered if the contribution of the neglected nuclides is less than 10% of the normalised sum.
• For radionuclides in radioactive equilibrium, the daughter radionuclides listed in a specific table may be neglected in the summation.
• For those nuclides not listed in the table, the values have to be calculated for the specific case. For nuclides with half lives less than 7 days or, in the case of small masses, the specific activity of the exemption level may be used for the release of solid or liquid material.
With these general conditions and the limits satisfied, unconditional release is permitted. This makes no restriction on further use. The values for solid material may also be used for building rubble and excavated material, if the mass is less than 1000t/year.
If the material is being released for disposal and not reuse, different conditions apply. The material must be sent to the waste disposal site without biological or chemical pre-processing or into an incineration plant, and the material must not be used outside the waste disposal site or incineration plant.
For dismantling buildings, measurements should be taken at the building prior to destruction, and may be taken by a spot check procedure. Areas up to 1m2 may be averaged. When a building has been demolished, the rubble that arises from dismantling does not require a separate release procedure.
Metal can be released for recycling if the recycling process involves melting the metal. The defined values cannot be used for mixtures of metallic and non-metallic material.
When considering contaminated land, readings may be averaged for land areas of up to 100m2. If there are no defined reference levels, dose calculations based on contamination measurements are required. The specific activity clearance level for soil may be recalculated into a surface contamination level, where surface level is a product of the specific level, soil density and mean penetration depth.
Overall changes in the Ordinance
Dose limits have undergone some important changes and reductions of values. Guidance on the release of low radioactive material either for unconditional use or for conditional use by recycling or by disposal has been implemented as a new, comprehensive part of the new Ordinance.
Although some effort to comply with the new Ordinance will have to be undertaken by nuclear plants, the implementation of the new regulations should not cause significant problems for utilities. However, in some cases, costs may increase.
TablesDose rates derived from dose limits Doseage threshold
