The document defines and discusses the phenomenon of low-temperature flow-accelerated corrosion (FAC), which can occur below 200°F. It summarizes operating experience with low-temperature FAC at several nuclear plants. The Electric Power Research Institute (EPRI) found susceptible areas in pressurized water reactors (PWRs) and boiling water reactors (BWRs) and made recommendations for inspections and analyses. The impact on corrosion susceptibility inspection projects is that piping downstream of condensate filters and demineralizers in PWRs, as well as low-oxygen areas in BWRs, should not be excluded from evaluations due to low temperatures.

1. Flow-Accelerated Corrosion at Low Temperatures R. Doremus February 20, 2009

2. Overview Summary of EPRI TR-1015170 Definition of Low-Temperature FAC Cause Operating Experience PWR BWR EPRI Findings EPRI Recommendations Impact on CSI Procedures

3. Definition Typically, Flow-Accelerated Corrosion (FAC) occurs between 200ºF and 450ºF. Low-Temperature FAC is FAC occurring below 200ºF.

4. Cause “poor water chemistry” NOT Low Temperature Low oxygen content < 20 ppb Neutral water pH ~ 7.0

5. Operating Experience in PWRs South Texas Project Palo Verde Surry Vogtle

6. South Texas Project Wear in piping downstream of Condensate Polishers Operating Temp. = 90-130ºF Carbon Steel (A106 B) pH @ 77ºF = 7.0 Dissolved O 2 ~ 5 ppb Measured Avg. Max. Wear Rate ~ 11.9 mils/year

7. Palo Verde Wear in Resin Traps downstream of Condensate Polishers Operating Temp = 135ºF Carbon Steel (A106 B) pH @ 77ºF = 7.0 Dissolved O 2 ~ 1-3 ppb Measured Avg. Max. Wear Rate ~ 6.6 mils/year

8. Surry Wear downstream of Condensate Polishers Operating Temp = 135ºF Carbon Steel (A106 B/A234 WPB) pH of slightly less than 7.0 Measured Avg. Max. Wear Rate ~ 10 mils/year

9. Vogtle Wear downstream of Steam Generator Blowdown Demineralizers Operating Temp = 130ºF Carbon Steel pH = 7.0 Measured Avg. Max. Wear Rate ~ 4.6 mils/year

10. Operating Experience in BWRs Fukushima Daini Nine Mile Point

11. Fukushima Daini Wear downstream of orifice in Control Rod Drive line. Operating Temp. = 95ºF Carbon Steel (JIS STPT38) Dissolved O 2 < 10 ppb Measured Avg. Max. Wear Rate ~ 8.1 mils/year

12. Nine Mile Point Wear in Reactor Building Closed Loop Cooling System (RBCLC) Operating Temp. = 120ºF Carbon Steel (A53 A,B / A234 WPA,B) Avg. pH = 6.5 Dissolved O 2 ~ 0 ppb (“below measurable amounts”) Worked in conjunction with other wear mechanisms (crevice, galvanic, and general corrosion)

13. EPRI Findings Susceptible areas in PWRs Downstream of Condensate Polishers before amine injection point Downstream of Steam Generator Blowdown Demineralizers Susceptible areas in BWRs Condensate upstream of oxygen injection point Anywhere with oxygen content < 20 ppb

14. EPRI Findings According to EPRI, CHECWORKS SFA can be applied to BWRs, CANDUs, and PWRs effectively for Low-Temperature FAC.

15. EPRI Recommendations PWRs Perform susceptibility analyses and, if necessary, inspections on Resin Traps and piping between polishers and amine injection points. Perform susceptibility analyses and, if necessary, inspections on piping downstream of Steam Generator Blowdown Demineralizers.

16. EPRI Recommendations BWRs Include all low-oxygen areas (< 20 ppb) of condensate, feedwater, and auxiliary systems in the FAC program. Be aware of possible damage upstream of oxygen injection location. Analysis and inspection may be required.

17. Impact on CSI Projects PWRs Piping downstream of Condensate Polishers and Steam Generator Blowdown Demineralizers should not be excluded in a System Susceptibility Evaluation (SSE) analysis due to low temperature. These lines should be modeled, if possible. Otherwise, include in the Susceptible Non-Modeled (SNM) Program. Will need input from client on amine injection point if not obvious from P&IDs or isometrics.

18. Impact on CSI Projects BWRs Use Water Chemistry Analysis in SFA to determine low-oxygen areas of the plant. May require entering plant global data in CHECWORKS prior to completion of an SSE. Be aware piping upstream of oxygen injection points. Categorize all low-oxygen areas as susceptible, regardless of temperature. Model susceptible lines if possible. Otherwise, include in SNM.