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BEHAVIOUR OF ACTINIDES AND OTHER RADIONUCLIDES THAT ARE DIFFICULT TO MEASURE, IN MELTING OF STEEL

Objective

VARIOUS TYPES OF CONTAMINATED PIPING, VALVES, HEAT EXCHANGERS AND VESSELS ARE REMOVED FROM NUCLEAR FACILITIES IN THE COURSE OF DECOMMISSIONING. DEPENDING ON THEIR ORIGIN, THESE COMPONENTS ARE CONTAMINATED WITH VARIOUS RADIONUCLIDES, E.G. ALPHA-EMITTERS, PURE BETA-EMITTERS, AND GAMMA-EMMITERS. UNRESTRICTED OR OTHERWISE NON-HAZARDOUS REUSE OF THESE COMPONENTS IS POSSIBLE IF THE RESIDUAL ACTIVITY CONCENTRATIONS ARE BELOW THE LIMITS AUTHORISED.

TO ACHIEVE THIS GOAL, DECONTAMINATION PROCESSES HAVE TO BE USED IN GENERAL. IN MANY CASES, CHEMICAL DECONTAMINATION OF LARGE COMPONENTS WITH COMPLEX SURFACE GEOMETRY CANNOT BE PERFORMED ECONOMICALLY. RECYCLING CAN BE ACHIEVED IN MANY CASES USING MELTING PROCESSES. THUS THE NON-HAZARDOUS REUSE OF BETA-, GAMMA-CONTAMINATED MATERIAL WHICH ACCUMULATED IN THE COURSE OF REPAIRS AND REFITTINGS OF NUCLEAR POWER PLANTS HAS BEEN DEMONSTRATED BY THE CONTRACTOR IN CO-OPERATION WITH SIEMPELKAMP GIESSEREI GMBH & CO, KREFELD.

THE AIM OF THIS RESEARCH PROGRAMME IS TO EXTEND THE MELT DECONTAMINATION PROCESS TO MATERIALS WHICH ARE CONTAMINATED WITH ACTINIDES AND RADIONUCLIDES THAT ARE DIFFICULT TO MEASURE. THE DISTRIBUTION OF THESE RADIONUCLIDES IN THE METAL AND THE SLAG WILL BE DETERMINED AND DIRECT MEASURING TECHNIQUES OR REPRESENTATIVE SAMPLING TECHNIQUES WILL BE DEVELOPED.
The research work carried out confirmed the expected homogeneous distribution of the radionuclides selected for the experiments (iron-55 and nickel-63) in the metal ingot, as was already known from the behaviour of cobalt-60. Cobalt-60 radionuclide may be used as an indicator nuclide for iron-55 and nickel-63 which are both difficult to measure. Carbon-14 also showed homogeneous distribution in the ingot (carbon steel). As expected for the melt technique strontium is released to the slag. In principle this is valid for actinides too, but depends to some extent on their chemical form (elemental uranium), the added tracer quantity and the quantity of slag forming material. A direct alpha measurement technique has been developed for steel samples and may be suitable for free release measurements of alpha emitting steel waste decontaminated by the melt technique.
B.1. LITERATURE REVIEW RELATED TO RADIONUCLIDE DEPOSITION ON COMPONENTS, CHEMICAL SEPARATION PROCEDURES FOR IRON AND NICKEL, BASIC RADIONUCLIDE DATA AND EVALUATION OF AUTHORISED ACTIVITY LIMITS.

B.2. SAMPLING OF MATERIAL AND TEST MELTS AT LABORATORY SCALE USING WELL KNOWN ACTIVITY QUANTITIES AND ACCOMPANIED BY AN APPROPRIATE MEASUREMENT PROGRAMME FOR ORIGINAL MATERIAL, METAL, SLAG AND OFF-GAS.

B.3. DEVELOPMENT OF DIRECT MEASURING TECHNIQUES FOR ALPHA EMITTERS IN MELT AND SLAG, TAKING INTO ACCOUNT THE ALPHA-ENERGY OF THE EMITTING NUCLIDES AND THE SAMPLE GEOMETRY.

B.4. DEVELOPMENT OF MEASURING TECHNIQUES FOR PURE BETA-EMITTERS, SUCH AS C-14 AND SR-90, EXPECTED TO BE FOUND IN METAL AND OFF-GAS, AND IN SLAG, RESPECTIVELY.

B.5. DEVELOPMENT OF A SAMPLING TECHNIQUE AND SIMPLE CHEMICAL SEPARATION PROCEDURES FOR NUCLIDES DECAYING BY ELECTRON CAPTURE, SUCH AS FE-55 AND NI-59, EMITTING WEAK X-RAYS WHICH CANNOT BE MEASURED DIRECTLY.

B.6. LARGE-SCALE MELT IN A COMMERCIAL FOUNDRY OF ALPHA-CONTAMINATED MATERIAL TO DEMONSTRATE THE TRANSFERABILITY OF THE LABORATORY RESULTS TO INDUSTRIAL SCALE.

B.7. EVALUATION OF RESULTS FROM BOTH LABORATORY TESTS AND LARGE-SCALE TESTS WITH RESPECT TO ALPHA-ACTIVITY DISTRIBUTION IN METAL, SLAG AND OFF-GAS, THE MOST SUITABLE MEASURING TECHNIQUE AND COSTS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Kraftwerk Union AG
Address

63001 Offenbach Am Main
Germany

Participants (1)

SIEMPELKAMP GIESSEREI