2191 R0 XI.M25

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XI.M25 BWR REACTOR WATER CLEANUP SYSTEM

Program Description

This program is a condition monitoring program that provides inspections to manage cracking due to stress corrosion cracking (SCC) or intergranular stress corrosion cracking (IGSCC) on the intended function of certain austenitic stainless steel (SS) piping in the reactor water cleanup (RWCU) system of boiling water reactors (BWRs). Based on the U.S. Nuclear Regulatory Commission (US NRC) criteria related to inspection guidelines for RWCU piping welds outboard of the second isolation valve, the program includes the measures delineated in NUREG–0313, Revision 2, and US NRC Generic Letter (GL) 88-01 and its Supplement 1.

US NRC GL 88-01 applies to all BWR piping made of austenitic SS that is 4 inches or larger in nominal diameter and contains reactor coolant at a temperature above 93 °C (Celsius) [200 °F (Fahrenheit)] during power operation, regardless of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) classification. US NRC GL 88-01 requests, in part, that affected licensees implement an inservice inspection (ISI) program conforming to staff positions for austenitic SS piping covered under the scope of the letter. In response to US NRC GL 88-01, affected licensees undertook ISI in accordance with the scope and schedules described in the letter and included affected portions of RWCU piping outboard of the second isolation valves within their ISI programs.

The US NRC issued GL 88-01, Supplement 1, to provide acceptable alternatives to the staff positions delineated in US NRC GL 88-01. In US NRC GL 88-01, Supplement 1, the staff noted, in part, that the position stated in US NRC GL 88-01 on inspection sample size of RWCU system welds outboard of the second isolation valves had created an unnecessary hardship for affected licensees because of the very high radiation levels associated with this portion of RWCU piping. The staff also noted that affected licensees had requested that they be exempted from NRC GL 88-01 with regard to inspection of this piping of the RWCU system. Although US NRC GL 88-01, Supplement 1, does not provide explicit generic guidance with regard to staff criteria for reduction or elimination of RWCU weld inspections, it does suggest that the staff would be receptive to modifications to a licensee’s original docketed US NRC GL 88-01 response for RWCU weld inspections, provided that all issues of reactor safety were adequately addressed. The staff has subsequently allowed individual licensees to modify their docketed responses to GL 88-01 to reduce or eliminate their ISI of RWCU welds in the piping outboard of the second isolation valves. This program only applies in cases where the US NRC has not previously approved the complete elimination of the augmented GL 88-01 inspections for RWCU system piping outboard the second containment isolation valves.

Evaluation and Technical Basis

1. Scope of Program: This program provides ISI to manage cracking due to SCC or IGSCC in austenitic SS piping outboard of the second containment isolation valves in the RWCU system.

The components included in this program are the welds in piping that have a nominal diameter of 4 inches or larger and that contain reactor coolant at a temperature above 93 °C (Celsius) [200 °F (Fahrenheit)] during power operation, regardless of ASME Code classification.

2. Preventive Actions: The comprehensive program outlined in NUREG-0313, and US NRC GL 88-01 addresses improvements in all three elements that, in combination, cause SCC or IGSCC. These elements are a susceptible (sensitized) material, a significant tensile stress, and an aggressive environment. The program delineated in NUREG-0313, and US NRC GL 88-01 includes recommendations regarding selection of materials that are resistant to sensitization, use of special processes that reduce residual tensile stresses, and monitoring and maintenance of coolant chemistry. The resistant materials are used for new and replacement components and include low-carbon grades of austenitic SS and weld metal, with a maximum carbon of 0.035 weight percent and a minimum ferrite of 7.5 percent in weld metal and cast austenitic stainless steel. Special processes are used for existing as well as new and replacement components. These processes include solution heat treatment, heat sink welding, induction heating, and mechanical stress improvement. Reactor coolant water chemistry is monitored and maintained in accordance with activities that meet the guidelines in the Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.M2, “Water Chemistry.”

3. Parameters Monitored or Inspected: The aging management program (AMP) monitors SCC or IGSCC of austenitic SS piping by detecting and sizing cracks in accordance with the guidelines of NUREG–0313, US NRC GL 88-01, and US NRC GL 88-01, Supplement 1.

4. Detection of Aging Effects: The extent, method, and schedule of the inspections delineated in the US NRC inspection criteria for RWCU piping and US NRC GL 88-01 are designed to maintain structural integrity and to detect aging effects before the loss of intended function of austenitic SS piping and fittings. Guidelines for the inspection schedule, methods, personnel, and sample expansion are based on US NRC GL 88-01 and GL 88-01, Supplement 1, and any applicable alternatives to these inspections that were subsequently approved by the US NRC. These alternative inspections are implemented in accordance with the current licensing basis for the plant. Typically, if all of the GL 89-10 actions had not been satisfactorily completed, then one alternative inspection would include 10 percent of the welds every refueling outage. Another alternative inspection would typically include at least 2 percent of the welds or 2 welds every refueling outage, whichever sample is larger, if: (a) all of the GL 89-10 actions had been satisfactorily completed, (b) no IGSCC had been detected in RWCU piping welds inboard of the second containment isolation valves, and (c) no IGSCC had been detected in RWCU piping welds outboard of the second containment isolation valves after a minimum of 10 percent of the susceptible welds were inspected.

5. Monitoring and Trending: The extent and schedule for inspection in accordance with the recommendations of US NRC GL 88-01 provide for the timely detection of cracks. Based on inspection results, US NRC GL 88-01 provides guidelines for additional samples of welds to be inspected when one or more cracked welds are found in a weld category.

6. Acceptance Criteria: US NRC GL 88-01 recommends that any indication detected be evaluated in accordance with the requirements of ASME Code, Section XI, Subsection IWB-3640.

7. Corrective Actions: Results that do not meet the acceptance criteria are addressed in the applicant’s corrective action program under those specific portions of the quality assurance (QA) program that are used to meet Criterion XVI, “Corrective Action,” of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the corrective actions element of this AMP for both safety-related and nonsafety-related structures and components (SCs) within the scope of this program.

The guidelines in US NRC GL 88-01 are followed for replacements, stress improvement, and weld overlay repairs.

8. Confirmation Process: The confirmation process is addressed through those specific portions of the QA program that are used to meet Criterion XVI, “Corrective Action,” of 10 CFR Part 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the confirmation process element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.

9. Administrative Controls: Administrative controls are addressed through the QA program that is used to meet the requirements of 10 CFR Part 50, Appendix B, associated with managing the effects of aging. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the administrative controls element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.

10. Operating Experience: IGSCC has occurred in small- and large-diameter BWR piping made of austenitic SS. The comprehensive program outlined in US NRC GL 88-01 and NUREG–0313 addresses improvements in all elements that cause SCC or IGSCC (e.g., susceptible material, significant tensile stress, and an aggressive environment) and is effective in managing IGSCC in austenitic SS piping in the RWCU system.

The program is informed and enhanced when necessary through the systematic and ongoing review of both plant-specific and industry operating experience including research and development such that the effectiveness of the AMP is evaluated consistent with the discussion in Appendix B of the GALL-SLR Report.

References

10 CFR Part 50, Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.

10 CFR 50.55a, “Codes and Standards.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.

ASME. ASME Code Section XI, “Rules for Inservice Inspection of Nuclear Power Plant Components.” New York, New York: The American Society of Mechanical Engineers. 2008.

US NRC. Generic Letter 88-01, “NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping.” Agencywide Documents Access and Management System (ADAMS) Accession No. ML031150675. Washington, DC: U.S. Nuclear Regulatory Commission. January 27, 1988.

_____. Generic Letter 88-01, “NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping.” Supplement 1. ADAMS Accession No. ML031130421. Washington, DC: U.S. Nuclear Regulatory Commission. February 4, 1992.

_____. Generic Letter 89-10, “Safety-related Motor Operated Valve Testing and Surveillance.” ADAMS Accession No. ML031150307. Washington, DC: U.S. Nuclear Regulatory Commission. August 3, 1990.

_____. NUREG–0313, “Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping.” Revision 2. ADAMS Accession No. ML031470422. Washington, DC: U.S. Nuclear Regulatory Commission. January 31, 1988.

_____. Pulsifer, Robert M., U.S. Nuclear Regulatory Commission, letter to Michael A Balduzzi, Vermont Yankee Nuclear Power Corporation, “Review of Request to Discontinue Intergranular Stress Corrosion Cracking Inspection of RWCU Piping Welds Outboard of the Second Containment Isolation Valves (TAC No. MB0468).” ADAMS Accession No. ML010780094. March 27, 2001.

_____. Shea, Joseph W., U.S. Nuclear Regulatory Commission, letter to George A. Hunger, Jr., PECO Energy Company, “Reactor Water Cleanup (RWCU) System Weld Inspections at Peach Bottom Atomic Power Station, Units 2 and 3 (TAC Nos. M92442 and M92443).” ADAMS Accession No. ML090930466. September 15, 1995.

Boiling Water Reactor

Stress Corrosion Cracking

United States of America

Nuclear Regulatory Commission - The US federal government agency that regulates nuclear power plants

American Society of Mechanical Engineers

Aging Management Program

Quality Assurance

Agency wide Documents Access and Management System - The official recordkeeping system, through which the U.S. Nuclear Regulatory Commission (US NRC) provides access to the "libraries" or collections of publicly available documents