Skip to main content

CONDITIONING OF NUCLEAR CLADDING WASTE BY HIGH TEMPERATURE MELTING IN COLD CRUCIBLE

Obiettivo

THE CONDITIONING OF ZIRCALOY AND STAINLESS STEEL HULLS BY HIGH TEMPERATURE MELTING IN COLD CRUCIBLE IS BEING DEVELOPED BY THE C.E.A IN FRANCE.
THE FEASIBILITY OF THIS PROCESS WITH DOES NOT REQUIRE ANY METALLIC ADDITIVE IS DEMONSTRATED, AT INDUSTRIAL SCALE WITH AN INACTIVE PROTOTYPE.

IN ORDER TO CARRY OUT EXPERIMENTS INVOLVING RADIOACTIVE HULLS, LABORATORY SCALE FACILITIES HAVE BEEN SET UP INSIDE A NEW SHIELDED CELL : THE MELTING UNIT IS ABLE TO PRODUCE SMALL METALLIC INGOTS WEIGHING ABOUT 3.5 KG, 18 CM LONG AND 5.7 CM IN DIAMETER.
THE OBJECTIVES OF THIS PROGRAM ARE :
- TO QUALIFY THE CELL PROCESS UNDER COLD CONDITIONS,
- TO REALIZE ACTIVE INGOTS WITH GENUINE STAINLESS STEEL HULLS COMING FROM THE PHENIX REACTOR,
- TO REALIZE INGOTS WITH ACTIVE ZIRCALOY COMING FROM THE OBRIGHEIM REACTOR.

THE PROJECT INCLUDES THE CHARACTERIZATION OF THE FINAL WASTE MATERIALS (INACTIVE AND ACTIVE INGOTS, GLASSES USED AS CONDITIONING MATRIX FOR SLAGS) AND THE EVALUATION OF THEIR LEACH RESISTANCE.
The fusion of cladding wastes obtained from the reprocessing of various irradiated fuels is an alternative method to the cementation process used for the conditioning of such wastes. This new process, based on the direct fusion of cladding has been carried out at CEA Marcoule with an inactive industrial prototype and qualified with an active laboratory prototype (scale 1/50) called cell 73. The results obtained with the laboratory prototype on stainless steel and zircaloy cladding are presented.

In order to qualify the melting unit of the cladding set up in cell 73, 6 inactive reference ingots were made up in real working conditions: 2 stainless steel ingots; 2 zircaloy ingots; 2 ingots of about 84% zircaloy, 10% stainless steel and 6% inconel (representative of the Obrigheim wastes).

The slags recovered after each melting were analysed. The metal ingots were cut into sections before being characterized. The laboratory investigation aims to specify the structure, the homogeneity, the chemical consistence and the water corrosion resistance of such ingots.

The differences in mass balances obtained compared with those obtained with inactive reference ingots are not noteworthy. The mass of slag recovered is however noticeably increased, averaging 13% with inactive ingots to 14.7% with active ones. The dissolution of the metal masses observed before and after melting was superior to the diminution noticed all through the tests with inactive reference ingots (1.45% with active ingots to 0.9% with inactive ones), confirming the loss in the form of oxide of the hull components and accounting for the larger quantity of slag recovered.

Active ingots make by melting stainless steel cladding from Phenix were also examined. The orginal activity introduced with the cladding is distributed in the volatile elements, in the slag and in the ingot at the end of the test. 84.9% of the beta activity was found inside the ingot, 9.6% in the slag, and 5.5% in the volatile eleme nts. 95.2% of the ruthenium activity 95.5% of the antimony activity and 99.97% of the cobalt activity was held within the ingot.

The alpha activity was distributed differently with more than 0.4% being inside the volatile elements, 99.5% in the slag and less than 0.1% inside the ingot.

The rate of activity inside each ingot was calculated. Cobalt-60, antimony-125 and the couple ruthenium-rhodium-106 were held inside the ingot. 60% of the caesium was volatilized; the remaining 40% is found in the slag. 96% of the scarcely volatile strontium was caught in the slag whereas the remaining 4% was distributed amongst the ingot and the volatile elements in equal proportions.

The results demonstrate and illustrate the importance of the ratio of slag mass to cladding mass.
THE PROJECT INCLUDES THE CHARACTERIZATION OF THE FINAL WASTE MATERIALS (INACTIVE AND ACTIVE INGOTS, GLASSES USED AS CONDITIONING MATRIX FOR SLAGS) AND THE EVALUATION OF THEIR LEACH RESISTANCE.

B.1. DEFINITION OF STANDARD WORKING CONDITIONS INVOLVING EITHER STAINLESS STEEL HULLS OR ZIRCALOY HULLS. DEVELOPMENT OF SUITABLE OPERATING METHODS FOR CHARACTERIZATION OF INGOTS AND SLAGS.

B.2. REALIZATION AND CHARACTERIZATION OF INACTIVE STAINLESS STEEL AND ZIRCALOY INGOTS.

B.3. REALIZATION AND CHARACTERIZATION OF ACTIVE STAINLESS STEEL INGOTS.

B.4. REALIZATION AND CHARACTERIZATION OF ACTIVE ZIRCALOY INGOTS.

Meccanismo di finanziamento

CSC - Cost-sharing contracts

Coordinatore

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