The objective of the study is to propose activity limits below which very slightly radioactive concrete arising from nuclear facility dismantling could be treated in conventional industry, or slightly contaminated buildings could be reused or decommissioned.

The study is based on the evaluation of concerned concrete quantities and allows the identification of groups of people exposed to radiation hazards. From the evaluation of individual radiological risk, the derived limits for exemption of concrete will be deduced. The study is also meant to participate in the harmonization of criteria and rules between countries of the European Community.

Potential benefits in determining such limits are:

limitation of the decontamination time and operations, ie, decontamination and disposal costs;
recycling of valuable material to preserve natural resources.

The research programme is performed in cooperation with TUV Bayern and RWE (contract No. FI2D0039), into which CEA-IPSN will bring in the following information: natural radioactivity in concrete; work programme and results of each period; results of other French experiments connected with the subject.
The objective of the study is to propose activity limits below which very slightly radioactive concrete arising from nuclear facility dismantling could be treated in conventional industry or slightly contaminated buildings could be reused or decommissioned. The study is based on the evaluation of concerned concrete quantities and allows the identification of groups of people exposed to radiation hazards. From the evaluation of individual radiological risk, the derived limits for exemption of concrete can be deduced.

A literature review on the mass resulting from dismantling of nuclear installations, including nuclear power plants and other plants from the fuel cycle was done.

From the results of an inquiry on different crushing stations, the time needed for crushing the concrete arising from one nuclear power plant was estimated

The values of the inhalable dust concentrations were measured in different conditions.

A study of the concrete crushing station was done. For workers, the exposure hazards are:
dust (inhalation, hand contamination, face contamination, ingestion, exposure to a deposit on soil, crusher maintenance);
concrete debris or aggregates (exposure to pile and during transport);
iron rebar (exposure to pile and transport, inhalation of iron dust during rebar cutting).
For public, the exposure hazards are:
inhalation of dust around the concrete crushing station;
ingestion of vegetables from a garden located near the concrete crushing station.
For the critical workers, the exposure parameters in the crushing station, were calculated.

The dose values for different critical pathways in a concrete crushing station, were calculated from the exposure parameters.
WORK PROGRAMME

1. Data collection

1.1. Estimation of contaminated and activated concrete quantities.
1.2. Identification of radionuclide spectra and activity levels.
1.3. Estimation of concrete quantity which is recycled or disposed off.
1.4. Determination of the state of the art to identify the critical group of workers and public.
1.5. Investigations on the possibilities of exposure of the public to different concrete by-products.
1.6. Dust measurements and analysis in different crushing stations.

2. Treatment of information and modelling.

2.1. Collection and evaluation of parameters for the different by-product pathways.
2.2. Modelling of the different realistic exposure situations for critical groups.

3. Calculation of the radiological impact using the parameters collected during the inquiries

4. Determination of the activity limits for each radionuclide and for classes of them.