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Mechanical Dejacketing of Liquid-Metal-Bonded Nuclear Fuels: An Evaluation of a Hydraulic Method and Two Alternative Methods with Spent Fuel from Core 1 of the Sodium Reactor Experiment

C. D. Watson, G. A. West, W. F. Schaffer, JR.

Nuclear Science and Engineering

Volume 17 / Number 1 / September 1963 / Pages 149-164


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Experimental mechanical equipment for removing the stainless steel jackets from the liquid-metal-bonded fuels of the Sodium Reactor Experiment (SRE), Fermi, and Hallam reactors was evaluated on a pilot scale. A hydraulic dejacketing method and two alternative methods were tested with spent, NaK-bonded stainless-steel-jacketed fuel from Core 1 of the SRE. This four-year-old fuel, consisting of 2.7% enriched uranium slugs, was exposed to an average irradiation of 675 Mw-day/tonne during a period of two years. It was discharged from the reactor after abnormal temperatures had damaged 30% of the core. About 1.8 metric tonnes of spent Core 1 fuel were dejacketed mechanically at rates up to 9.2 kg of uranium per hour. A production rate 2 to 3 times higher had been predicted from the processing of unirradiated fuel. The hydraulic method, by which it was planned that all fuel would be processed (by expansion of the jackets and expulsion of the slugs) worked with only 16.5% of the fuel. The remainder of the fuel had to be processed by one of the two alternative methods. Dislodgment of fuel slugs from the jackets was extremely difficult because the jacket and some slugs were stuck together by a eutectic alloy of stainless steel-uranium. Also, the irradiated jackets had lost their ductility from the midpoint of a fuel rod to the top and, in addition, showed evidence of carburization, work hardening, sensitization, and embrittlement. Dejacketing of the abnormal SRE Core 1 fuel was accomplished successfully but none of the three dejacketing methods evaluated appeared to be sufficiently versatile to accommodate abnormal fuel and thus cannot be guaranteed as reliable production methods for the liquid-metal-bonded fuels.

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