Experimental fast reactor "JOYO" Operation report; Operation results of main primary cooling system

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The main primary cooling system of Experimental Fast Reactor "JOYO" has experienced approximately 52,000 hours operation since the initial sodjnm charge in 1976 by the end of Reactor-Run 6 at 75MWt in Dec., 1981. In the meantime, though the primary sodium pumps were pulled out once and the labyrinth-bushes on shaft-seal assemblies, sodium bearings were remodeled, primary sodium pumps were operated for 38,000 hours satisfactorily. JOYO has achieved 12,800 hours of reactor operation, and will attain 100MWt reactor power after the core conversion work now in progress. This report generally deseribes the operation history and results of main primary cooling system and primary sodium pumps.