AN IMPORTANT TASK IN THE DECOMMISSIONNING OF NUCLEAR INSTALLATIONS IS THE PROOF OF THE VERY LOW RADIOACTIVITY LEVELS, ALLOWING FOR FREE RELEASE OF THE GENERATED WASTE. THIS PROOF INVOLVESLONG MEASURING TIMES ON A GREAT NUMBER OF REPRESENTATIVE SAMPLES OUT OF IMPORTANT MASSES OF METAL STRUCTURES AND CONCRETE, AND CONSIDERABLE RADIATION EXPOSURE OF THE MEASURING STAFF. THE MAIN OBJECTIVE OF THE PRESENT RESEARCH IS THE DEVELOPMENT, CONSTRUCTION AND LARGE-SCALE TESTING OF A PROTOTYPE FOR AN AUTOMATIC MEASURING SYSTEM, APPROPRIATE TO TREAT IMPORTANT MASSES OF WASTE, WITH LOW-LEVEL ACTIVITIES AND DIFFERENT NUCLIDE COMPOSITIONS AND SHAPES. IT IS EXPECTED TO MINIMISE HUMAN ERRORS BY AUTOMATIC OPERATION. THE MEASURING SYSTEM WILL BE DESIGNED AS A MOBILE UNIT, WITH A MODULAR STRUCTURE ALLOWING FOR A GENERAL PURPOSE APPLICATION TO LWR TYPICAL WASTE ARISING, AT DIFFERENT DECOMMISSIONING SITES. THE PRACTICAL TESTING WILL BE DONE A TOTAL MASS OF 1000 MG IN THE FRAMEWORK OF THE KKN DECOMMISSIONING. THE STUDY WILL BE COMPLETED BY A CONCLUSIVE ASSESSMENT OF THE MERITS OF THE DEVELOPED MEASURING SYSTEM FOR LARGE-SCALE OPERATION.
The dismantling of nuclear facilities requires proof that the radioactivity levels of materials to be released from restricted areas remain below low limiting values. Up till now, decisive measurements have been almost impossible on parts and material with complex geometries. In order to keep measurement costs low, a device has been developed which uses a fast automatic procedure to examine large amounts of dismantled and potentially contaminating components.
The device measures the gross gamma-radiation which has a higher penetrating capacity into the material than beta radiation. The measuring tunnel is 1.2 m broad and 1.2 m high. Parts to be measured can be up to 4 m long and weigh 1 tonne. Analysis of measurements has shown that the specified minimal detectable activity level of 1000 Bq cobalt-60 can be achieved, even with steel shielding of 2 cm thickness.
B.1.CONCEPTUAL STUDIES FOR THE DEFINITION OF THE REQUIREMENTS FOR A MEASURING SYSTEM,INCLUDING ASSESSMENT OF EXISTING LOW-LEVEL ACTIVITY MEASURING TECHNIQUES, DEFINITION OF THE TYPES OF WASTE TO BE TREATED, AND HEALTH PHYSICS PROTECTION CONSIDERATIONS.
B.2. PREPARATION OF A DESIGN OF THE COMPLETE MEASURING SYSTEM,INCLUDING DETECTORS,CONTROL AND TRANSPORT SYSTEM, GENERAL PURPOSE SOFTWARE FOR MEASURING DATA PROCESSING, FOLLOWED BY A CALL FOR TENDERS AND THE CHOICE OF MANUFACTURES.
B.3. PREPARATION OF A LICENSING DOSSIER FOR EXPERIMENTAL OPERATION OF THE MEASURING SYSTEM PROGRAMME. IN THE FRAMEWORK OF THE DECOMMISSIONING OF KKN.
B.4. EXECUTION OF A LARGE-SCALE TEST PROGRAMME.
B.5.CONCLUSIVE ASSESSMENT OF THE APPROPRIATENESS OF THE DEVELOPED MEASURING SYSTEM, CONSIDERING TECHNICAL AND ECONOMIC ASPECTS.