XI.M4 (NUREG-1801 R0)
XI.M4 BWR VESSEL ID ATTACHMENT WELDS
Program Description
The program includes (a) inspection and flaw evaluation in accordance with the guidelines of staff-approved boiling water reactor vessel and internals project (BWRVIP)-48(Archived) and (b) monitoring and control of reactor coolant water chemistry in accordance with the guidelines of BWRVIP-29 (Electric Power Research Institute [EPRI] TR-103515)(Archived) to ensure the long-term integrity and safe operation of boiling water reactor (BWR) vessel inside diameter (ID) attachment welds.
Evaluation and Technical Basis
- 1. Scope of Program: The program is focused on managing the effects of crack initiation and growth due to stress corrosion cracking (SCC), including intergranular stress corrosion cracking (IGSCC). The program contains preventive measures to mitigate SCC; inservice inspection (ISI) to detect cracking and monitor the effects of cracking on the intended function of the components; and repair and/or replacement, as needed, to maintain the ability to perform the intended function.
- The guidelines of BWRVIP-48(Archived) include inspection recommendations and evaluation methodologies for the attachment welds between the vessel wall and vessel ID brackets that attach safety-related components to the vessel (e.g., jet pump riser braces and core-spray piping brackets). In some cases, the attachment is a simple weld; in others, it includes a weld build-up pad on the vessel. The BWRVIP-48(Archived) guidelines include information on the geometry of the vessel ID attachments; evaluate susceptible locations and safety consequence of failure; provide recommendations regarding the method, extent, and frequency of inspection; and discuss acceptable methods for evaluating the structural integrity significance of flaws detected during these examinations.
- 2. Preventive Actions: The BWRVIP-48(Archived) provides guidance on detection, but does not provide guidance on methods to mitigate cracking. Maintaining high water purity reduces susceptibility to SCC or IGSCC. Reactor coolant water chemistry is monitored and maintained in accordance with the guidelines in BWRVIP-29 (EPRI TR-103515)(Archived). The program description and evaluation and technical basis of monitoring and maintaining reactor water chemistry are presented in Section XI.M2, "Water Chemistry."
- 3. Parameters Monitored/Inspected: The program monitors the effects of SCC and IGSCC on the intended function of vessel attachment welds by detection and sizing of cracks by ISI in accordance with the guidelines of approved BWRVIP-48(Archived) and the requirements of the American Society of Mechanical Engineers (ASME) Code, Section XI, Table IWB 2500-1 (1995 edition through the 1996 addenda). An applicant may use the guidelines of BWRVIP-62(Archived) for inspection relief for vessel internal components with hydrogen water chemistry.
- 4. Detection of Aging Effects: The extent and schedule of the inspection and test techniques
prescribed by BWRVIP-48(Archived) guidelines are designed to maintain structural integrity and ensure that aging effects will be discovered and repaired before the loss of intended function. Inspection can reveal crack initiation and growth. Vessel ID attachment welds are inspected in accordance with the requirements of ASME Section Xi, Subsection IWB, examination category B-N-2. The Section XI inspection specifies visual VT-1 examination to detect discontinuities and imperfections on the surfaces of components and visual VT-3 examination to determine the general mechanical and structural condition of the component supports. The inspection and evaluation guidelines of BWRVIP-48(Archived) recommend more stringent inspections for certain selected attachments. The guidelines recommend enhanced visual VT-1 examination of all safety-related attachments and those nonsafetyrelated attachments identified as being susceptible to IGSCC. Visual VT-1 examination is capable of achieving 1/32 in. resolution; the enhanced visual VT-i examination method is capable of achieving a 1-mil wire resolution. The nondestructive examination (NDE) techniques appropriate for inspection of BWR vessel internals and their implementation needs, including the uncertainties inherent in delivering and executing NDE techniques in a BWR, are included in BWRVIP-03(Archived).
- 5. Monitoring and Trending: Inspections scheduled in accordance with IWB-2400 and approved BWRVIP-48(Archived) guidelines provide timely detection of cracks. If flaws are detected, the scope of examination is expanded.
- 6. Acceptance Criteria: Any indication detected is evaluated in accordance with ASME Section XI or the staff-approved BWRVIP-48(Archived) guidelines. Applicable and approved BWRVIP-14(Archived), BWRVIP-59(Archived), and BWRVIP-60(Archived) documents provide guidelines for evaluation of crack growth in stainless steels (SSs), nickel alloys, and low-alloy steels, respectively.
- 7. Corrective Actions: Repair and replacement procedures are equivalent to those requirements in the ASME Section XI. Repair is in conformance with IWB-4000 and replacement occurs according to IWB-7000. As discussed in the appendix to this report, the staff finds that licensee implementation of the guidelines in BWRVIP-48(Archived), as modified, will provide an acceptable level of quality for inspection and flaw evaluation of the safety-related components addressed in accordance with 10 CFR Part 50, Appendix B, corrective actions.
- 8. Confirmation Process: Site quality assurance (QA) procedures, review and approval processes, and administrative controls are implemented in accordance with the requirements of 10 CFR Part 50, Appendix B. As discussed in the appendix to this report, the staff finds that licensee implementation of the guidelines in BWRVIP-48(Archived), as modified, will provide an acceptable level of quality for inspection and flaw evaluation of the safety-related components addressed in accordance with the 10 CFR Part 50, Appendix B, confirmation process and administrative controls.
- 9. Administrative Controls: See Item 8, above.
- 10. Operating Experience: Cracking due to SCC/IGSCC has occurred in BWR components. The program guidelines are based on evaluation of available information, including BWR inspection data and information on the elements that cause IGSCC, to determine which attachment welds may be susceptible to cracking. Implementation of the program provides reasonable assurance that crack initiation and growth will be adequately managed and the intended functions of the vessel ID attachments will be maintained consistent with the current licensing basis (CLB) for the period of extended operation.
References
10 CFR 50.55a, Codes and Standards, Office of the Federal Register, National Archives and Records Administration, 2000.
ASME Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, ASME Boiler and Pressure Vessel Code, 1995 edition through the 1996 addenda, American Society of Mechanical Engineers, New York, NY.
BWRVIP-03, BWR Vessel and Internals Project, Reactor Pressure Vessel and Internals Examination Guidelines, (EPRI TR-105696 R1, March 30, 1999)(Archived), Final Safety Evaluation Report by the Office of Nuclear Reactor Regulation for BWRVI P-03, July 15, 1999.
BWRVIP-14, Evaluation of Crack Growth in BWR Stainless Steel RPV Internals, (EPRI TR-105873, July 11, 2000)(Archived), Final Safety Evaluation Report by the Office of Nuclear Reactor Regulation for BWRVIP-14, December 3, 1999.
BWRVIP-29, BWR Vessel and Internals Project, BWR Water Chemistry Guidelines-1993 Revision, Normal and Hydrogen Water Chemistry, (EPRI TR- 103515)(Archived), Electric Power Research Institute, Palo Alto, CA, February 1994.
BWRVIP-48, BWR Vessel and Internals Project, Vessel ID Attachment Weld Inspection and Flaw Evaluation Guidelines, (EPRI TR-108724, February 1998)(Archived), Final License Renewal Safety Evaluation Report by the Office of Nuclear Reactor Regulation for BWRVIP-48 for Compliance with the License Renewal Rule (10 CFR Part 54), January 17, 2001.
BWRVIP-59, Evaluation of Crack Growth in BWR Nickel-Base Austenitic Alloys in RPV Internals, (EPRI TR-108710)(Archived), BWRVIP and Electric Power Research Institute, Palo Alto, CA, March 24, 2000.
BWRVIP-60, BWR Vessel and Internals Project, Evaluation of Crack Growth in BWR Low Alloy Steel RPV Internals, (EPRI TR-108709, April 14, 2000)(Archived), Final Safety Evaluation Report by the Office of Nuclear Reactor Regulation for BWRVIP-60, July 8, 1999.
BWRVIP-62, BWR Vessel and Internals Project, Technical Basis for Inspection Relief for BWR Internal Components with Hydrogen Injection, (EPRI TR-108705)(Archived), BWRVIP and Electric Power Research Institute, Palo Alto, CA, March 7, 2000.