[en] The PWR steam generator tube to tubesheet crevice test program was formulated to develop flushing procedures for removing concentrated chemical solutions from partially rolled (deep) tubesheet crevices and to investigate the characteristics of various tube to tubesheet joint crevice configurations with regard to the initiation of concentration processes. The crevice flushing testing indicated that significant fractions of a concentrated sodium hydroxide solution could be transported out of a full depth, unpacked tubesheet crevice by heating and then depressurizing the contents of the crevice. Based upon testing of both packed and unpacked crevices, the most effective flushing procedure was found to utilize the primary coolant system as the heat source, an initial crevice temperature of about 300₀F, a nitrogen overpressure in the steam generator, and alternating rapid and slow depressurizations