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DECONTAMINATION, BEFORE DISMANTLING, OF THE PRIMARY COOLANT SYSTEM OF THE RAPSODIE FBR

Objective

THE LARGE-SCALE DECONTAMINATION OF FBR SODIUM LOOPS IS AN ORIGINAL TASK, SINCE ONLY A LIMITED NUMBER OF RESULTS WITH LABORATORY-SCALE WORK IS AVAILABLE, SO FAR. THE PRINCIPAL AIM OF THE PRESENT CONTRACT IS THE DEVELOP- MENT OF AN APPROPRIATE DECONTAMINATION PROCEDURE AND ITS APPLICATION TO THE PRIMARY LOOPS OF THE RAPSODIE FBR IN THE FRAMEWORK OF ITS STAGE 2 DECOMMISSIONING.
THE PROCEDURE IS DEVELOPED IN A PILOT FACILITY, ALLOWING TO TREAT REPRESENTATIVE SAMPLES AND PROVIDING THE SELECTION OF AN EFFICIENT DECONTAMINANT, BUT ALSO WITH SPECIAL CARE IN MINIMISING AND TREATING THE SECONDARY WASTE. AFTER DISCONNECTING THE PIPE WORK FROM THE MAIN VESSEL, PIPES WILL BE TREATED BY CIRCULATING CHEMICAL SOLUTIONS, AND CONTAINERS BY SPRAYING LIQUIDS OR GELS.
The principal objective of this work was to develop a suitable decontamination procedure for the primary cooling loops of a fast breeder reactor as part of its decommissioning. The reactor primary cooling system and related circuits (excluding the main reactor vessel), which represented 164 m{2}, were decontaminated in 2 months. The average metal removal depth was 12 um.
The procedure involved 3 steps:
alkaline washing to remove all the acids;
the addition of cerium(IV) to entrain the fixed contamination including about 10% cobalt-60;
a final phosphatisation step.
The estimated initial contamination level of 5500 Bq/cm{2} was reduced to less than 10 Bq/g, enabling manual dismantling operations to proceed without constraints and avoiding an initial occupational dose estimated at 230 mSv. The dose rate in the areas to be dismantled was reduced by a factor of 10. A decontamination factor of about 300 was obtained. This should allow austenitic steel parts to be melted in special furnaces with unrestricted release. The decontamination operations generated 2600 kg of dry extract which was encapsulated by the local waste treatment station.
B.1. CHARACTERISATION OF THE PRIMARY REACTOR LOOPS TO BE DECONTAMINATED, INCLUDING SIZE AND NATURE OF STRUCTURES AND TYPE AND DEGREE OF CONTAMINATION.
B.2. CONSTRUCTION AND COMMISSIONNING TESTS OF THE PILOT DECONTAMINATION LOOP GROLABO.
B.3. DECONTAMINATION TESTS IN THE GROLABO FACILITY,AIMED AT AN OPTIMISATION OF PROCEDURES AND OF SECONDARY WASTE TREATMENT.
B.4.SAFETY ANALYSIS FOR THE DECONTAMINATION OF THE PRIMARY REACTOR LOOPS AND ORDERIMG OF NEEDED EQUIPMENT.
B.5.ADAPTATION OF THE PRIMARY REACTOR LOOPS, INCLUDING ISOLATION FROM THE REACTOR VESSEL AND EQUIPMENT WITH SPECIFIC COMPONENTS AND INSTRUMENTATION.
B.6.ASSESSMENT OF THE ABOVE DEVELOPED DECONTAMINATION PROCEDURES AND DECONTAMINATION OF THE ISOLATED PRIMARY REACTOR LOOPS.
B.7.TREATMENT OF EFFLUENTS.
B.8.FINAL ASSESSMENT OF OBTAINED RESULTS AND RECOMMANDATIONS FOR FUTURE WORK.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
Address
Centre D'études Nucléaires De La Vallée Du Rhône Cité De Marcoule
30205 Bagnols-sur-cèze
France