Corrosion evaluation of the PNS CITROX process for chemical decontamination of BWR structural materials

Technical Report · Fri Aug 01 04:00:00 EDT 1986

OSTI ID:5361959

Wang, M T

The effects of PNS Citrox decontamination on the corrosion and intergranular stress corrosion cracking (IGSCC) of sensitized Type 304 stainless steel and Alloy 600 were assessed. Evaluations involved decontaminated surface morphology examination, as well as constant extension rate tensile (CERT) testing in BWR water. Quenched and tempered low alloy steel was also included for evaluation of general corrosion. The Pacific Nuclear Services (PNS) Citrox decontamination included laboratory one- and three-step processes as well as an in-plant three- step Citrox process applied at the Vermont Yankee Power Plant. For the laboratory Citrox decontamination, intergranular attack (IGA) up to 3.2 mils in depth was observed in the sensitized Type 304 stainless steel. No IGA occurred in the laboratory decontaminated Alloy 600. On the other hand, no IGA was found in sensitized Type 304 stainless steel for the in-plant Citrox decontamination, but shallow and extremely narrow IGA was observed in the Alloy 600. Results of CERT stress corrosion cracking tests indicated that sensitized Type 304 stainless steel exposed to the three-step laboratory Citrox decontamination suffered degradation of IGSCC resistance. However, no degradation of IGSCC resistance was observed for the steel exposed to the one-step laboratory process or to PNS Citrox decontamination at the Vermont Yankee Plant. Moderate general corrosion in the range of one to three mils per decontamination cycle was observed in quenched and tempered low alloy steel. However, very low general corrosion was found in sensitized Type 304 stainless steel and Alloy 600.

• Research Organization: General Electric Co., San Jose, CA (USA). Engineering Services
• OSTI ID: 5361959
• Report Number(s): EPRI-NP-4687; ON: TI86920477
• Country of Publication: United States
• Language: English

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