SALT BATH HEAT TREATMENT OF PWR CORE 2 FUEL ELEMENTS

摘要

Previous investigations at Bettis Laboratory established that the Zircaloy cladding of PWR Core 2 seed and blanket fuel elements pressure-bonded in the alpha-plus-beta field possessed inadequate corrosion resistance and that high corrosion resistance could be restored to Zircaloy in this two-phase condition by an additional heat treatment in the all-beta field followed by rapid cooling. The present work was undertaken to determine the feasibility of per¬forming this beta treatment on PWR Core 2 fuel elements in a molten salt bath on a production basis and, if feasible, to deter¬mine the metallurgical parameters for the process. To this end a vertical salt bath capable of beta-treating production-sized (55 x 4-inches) fuel elements was improvised using available compo¬nents, and experiments were performed using both solid Zircaloy plates and pressure-bonded PWR Core 2 seed and blanket fuel elements. It was found that salt bath beta treatment was a fea¬sible production process, and the process parameters were established.