The first full-system chemical decontamination (FSD) of a nuclear power reactor in the United States was performed at Consolidated Edison’s Indian Point 2 (IP-2) PWR in March 1995. This National Demonstration of a full reactor coolant system (RCS) decontamination was performed using a five-step decontamination process. To evaluate the effects of the
decontamination on materials in the IP-2 RCS, and to ensure the integrity of these materials, several types of corrosion specimens were installed in the decontamination process system (DPS). Corrosion coupons were fabricated from: . major RCS materials of construction - Alloy 600, type 304 stainless steel (SS) , sensitized 304 SS, 316 SS, 410 SS. . Cr- and Ni-plated materials. Co-, Ni- and Fe-based hard-facing alloys. Stressed specimens were included for materials that could possibly be susceptible to inter-granular attack and stress corrosion cracking. The metallographic examination of the corrosion specimens did not reveal any materials compatibility issues that would have an impact on operation of the IP-2 PWR following the FSD. IP-2 was successfully returned to service without problems, and is now into the second cycle of operation following the FSD. A key result from the Scanning Auger Microscopy (SAM) examination of 304 SS and Alloy 600 artifacts from IP-2 was that a thin, Cr-rich film remains on the specimens after the decontamination. The presence of a Cr-rich oxide may serve to passivate surfaces and minimize recontamination rates during subsequent reactor operation. At the conclusion of the FSD in 1995, the radiation fields had been reduced by an average of 87%. Radiation field measurements taken by Consolidated Edison during the 1997 refueling outage (25 months following the FSD) indicated that the radiation fields had increased by less than 10 % across the plant and were 84% lower than the 1995 pre-decontamination levels; recontamination rates are significantly lower than expected.
Keywords: full-system decontamination, PWRs, materials compatibility, corrosion, chemical decontamination, dose reduction, ALARA, recontamination