ML22146A066
| ML22146A066 | |
| Person / Time | |
|---|---|
| Site: | Electric Power Research Institute |
| Issue date: | 06/06/2022 |
| From: | Lois James Licensing Processes Branch |
| To: | Richard Chang Licensing Processes Branch |
| Lois James, NRR/DORL/LLPB, 301-415-3306 | |
| References | |
| EPID L-2022-PPM-0000 | |
| Download: ML22146A066 (8) | |
Text
June 6, 2022 MEMORANDUM TO:
Richard Chang, Chief Licensing Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Lois M. James, Senior Project Manager /RA/
Licensing Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF MEETING FOR ELECTRIC POWER RESEARCH INSTITUTE TO PRESENT ANTICIPATED ASME CODE CASE N-729 VISUAL EXAM UPDATES TO THE U.S. NUCLEAR REGULATORY COMMISSION (EPID L-2022-PPM-0000)
On May 11, 2022, the U.S. Nuclear Commission staff met with the Electric Power Research Institute (EPRI) for EPRI to provide an update to the NRC of changes to American Society of Mechanical Engineers (ASME) Code Case N-729 that has been submitted to the ASME Code Committee. The meeting summary is Enclosure 1 and the list of attendees is Enclosure 2.
If you have any questions or comments, please contact me via e-mail at Lois.James@nrc.gov.
Docket No. 99902021
Enclosures:
- 1. Meeting Summary
- 2. List of Attendees CONTACT: Lois M. James, NRR/LLPB 301-415-3306
U.S. Nuclear Regulatory Commission Public Meeting Summary
Title:
Meeting for Electric Power Research Institute (EPRI) to Present Anticipated American Society of Mechanical Engineers (ASME) Code Case N-729 Visual Exam Updates to the U.S. Nuclear Regulatory Commission (NRC)
Date of Meeting: May 11, 2022, 1:30 pm - 3:30 pm Location: Webinar Purpose of the Meeting: For EPRI to provide an update to the NRC of proposed changes to ASME Code Case N-729 that will be submitted to the ASME Code Committee.
General Details: The NRC staff held a public, observational meeting with EPRI for EPRI to provide an update to the NRC regarding proposed changes to ASME Code Case N-729 visual examination requirements that was discussed and will be submitted to the ASME Code Committee, Task Group on High Strength Nickel Alloys, for consideration. The meeting began at 1:30 pm and ended 3:25 pm. There were 26 NRC staff members, 3 EPRI members, 15 members of industry, and 3 members of the public or individuals who did not identify their affiliation. The meeting began with introductions of the NRC staff, EPRI staff, and industry staff.
Summary of Meeting: EPRI began the discussion by explaining the purpose of the meeting.
Specifically, over the last several years, several licensees have submitted relief requests regarding visual examinations associated with concerns and indications on the upper head when using ASME Code Case N-729. In addition, the NRC staff issued Regulatory Issue Summary (RIS) 2018-06, Clarification of the Requirements for Reactor Pressure Vessel Upper Head Bare Metal Visual Examinations, to clarify the requirements for bare metal visual examination, which can be either a visual examination of the bare metal of the upper head or a visual testing (VT)-2 examination under the insulation to meet the requirements, as conditioned by 10 CFR 50.55a(g)(6)(ii)(D), of notes 1 and 4 in Table 1 of ASME Code Case N-729-6.
EPRI considers the current Code Case requirements associated with visual examinations vague and proposes to update those requirements. Based on industry and NRC thoughts and experiences, EPRI began working to develop improvements to the visual examination language in ASME Code Case N-729 to implement a more structured process and reduce ambiguity.
EPRI began with a review of the existing visual examination acceptance criteria of ASME Code Case N-729 which includes the following concepts:
Evaluation for source of relevant conditions Evaluation for degradation of low-alloy steel Supplemental exam or correction of the source Subsequent visual examinations of the previously obscured surfaces before return to service and at the next refueling outage (RFO)
EPRI is proposing to incorporate the following additional concepts not currently explicitly included within the Code Case:
Explicit consideration of masking deposits from a source other than head penetration leakage (including a limit on number of masked penetrations depending on the head category)
Explicit recognition that superficial discoloration and superficial deposits do not require evaluation Specification of the information to be collected in support of the evaluation, to the extent such information is relevant and can reasonably be obtained Establish an explicit standard of reasonable confidence that the relevant condition is not the result of head penetration leakage EPRI also noted that:
The concept of relevant conditions is reasonably reflected in the current language of the code case, but is not as tightly defined as it could be The concept of evaluation for degradation of low-alloy steel is there and is adequate The following concepts are there but would be modestly adjusted under this proposal o Supplemental exam or correction of the source o Subsequent visual examination (VE) of previously obscured surfaces before return to service and at the next RFO The EPRI presentation next focused on a detailed discussion of their flowchart capturing the entirety of the proposed revised process for conducting the visual examination, evaluating any identified relevant conditions, and taking the necessary actions determined from that evaluation.
EPRI characterized this revised process as providing for a more structured, methodical evaluation than currently required, and incorporating the new concepts previously noted.
Several new or revised definitions and their basis were also discussed including that of masking deposits, which is important to the evaluation. The proposed masking definition requires there be strong evidence that the deposit is coming from above, but also recognition that more than one source of leakage might be present and that the masked condition could compromise the visual examination.
EPRI explained that the proposed standard of reasonable confidence recognizes that absolute confidence in the determination whether evidence of nozzle leakage is present is not necessary.
This conclusion is based on related requirements that maintain defense in depth and that extensive research and operating experience support a determination that the required repeat visual exam in the next refueling outage is sufficiently timely to avoid a consequential challenge to nuclear safety.
EPRI also proposed a requirement for personnel performing the evaluation of relevant conditions identified during visual examinations.
EPRI concluded by explaining that they plan to initiate a Code Action through ASME to seek Code Committee approval. Subsequent NRC consideration of the approved revised Code Case would of course take time, but the updated Code Case and basis document would be available, and licensees could use the information.
The NRC staff asked questions and made comments including the following:
Regarding the 15 indications, partially masked penetrations may Can you further explain the word may?
o Licensees would have the option of counting fractions of masking indications. For example, if there are two penetrations that are 50 percent masked, this could count as one fully masked penetration rather than two. This would require additional analysis within the required evaluation, but is an option.
Can you speak to reasonable confidence in the context of the detection and evaluation of relevant conditions?
o Dust or debris which is blown away would not count as a relevant condition. After blowing, remaining deposits that may be reactor coolant system leakage and meet the relevant condition definition would need to be evaluated under the Code Case. The reasonable confidence standard is obtained through the rigorous, detailed deposit evaluation process, which may include potential steps delineated in supporting documents such as MRP-60. Deposit removal should not be undertaken until a licensee has sufficiently assessed and characterized the material, including any necessary sampling, to support the subsequent evaluation. Power wash cleaning would be the last task accomplished.
Reasonable confidence is a field decision that will need to be recorded and justified.
There does not appear to be clear cut go/no-go decision point. Given this is a field decision, is there more information for regional inspectors to better understand?
o The reasonable confidence standard would primarily be applied during the well-documented evaluation process for dispositioning relevant conditions identified during the initial VE as opposed to being a true field decision. EPRI has also worked on a quantitative scoring rubric concept which might be applied to reduce the subjectivity in assessing each evaluation item. This scoring rubric may be included in the basis documents rather than being codified in the Code Case.
This is part of the details that are still being developed.
Can you discuss the terms superficial nature, previously obscured, and masked further?
o Superficial discoloration or superficial deposits are defined as areas of discoloration or deposits on the head upper surface with no visually discernible thickness. Based on operating experience from past inspections, superficial deposits or discoloration have not been associated with head penetration leakage. The proposed Code Case changes do not require further evaluation of the superficial deposits or discoloration but do require their documentation during the visual inspection.
o Regarding previously obscured and masked, EPRI explained that any relevant conditions need to be removed to allow inspection of the bare metal to see corrosion and any degradation before returning to service. Masked locations are only a subset of potential relevant conditions that may obscure the head surface, so both terms are relevant in this discussion.
Years ago, inspectors found that a licensee cleaned a deposit found on the reactor vessel head before conducting any analyses or evaluation. Would this be permitted under the revision being proposed.
o EPRI stated the intent is to build more structure and logical sequencing into the revised language beyond what is currently in the Code Case such that all appropriate information would be collected to support analysis and evaluation prior to cleaning to remove relevant conditions.
There has been a lot of discussion in this meeting about applying the standard of reasonable confidence in the Code Case. Why reasonable confidence and not reasonable assurance? And what are the criteria? Why would you not update the language in the Code Case instead of providing more guidance in the basis document or MRP-60?
o EPRI stated that reasonable confidence is subjective and not easily reducible to a set of objective criteria. As proposed, whether a reasonable confidence conclusion can be reached is the focus of the evaluation. The evaluation must weigh the available evidence, develop a logical framework for assessing and understanding it, and present a defensible position as to why it does or does not reach a conclusion with reasonable confidence.
o Given this lack of simple objective criteria, direct incorporation into the Code Case appears impractical and EPRI judged it more appropriate to provide practical guidance and examples within EPRI Technical Report MRP-60, Materials Reliability Program: Visual Examination for Leakage of PWR Reactor Vessel Upper Head Nozzles. Also, there seems to be little difference between reasonable confidence and reasonable assurance as they are generally considered synonymous.
Public Participation Themes: No member of the public spoke on the webinar.
Attachments:
Meeting description and agenda - ADAMS Accession No. ML22117A034 EPRI slide presentation - ADAMS Accession No. ML22129A008 EPRI Markup of ASME Code Case N-729 - ADAMS Accession No. ML22129A007
U.S. Nuclear Regulatory Commission Public Meeting Attendees
Title:
Meeting for Electric Power Research Institute to Present Anticipated American Society of Mechanical Engineers Code Case N-729 Visual Exam Updates to the U.S. Nuclear Regulatory Commission Date of Meeting: May 11, 2022, 1:30 pm - 3:30 pm NRC PARTICIPANTS Name Affiliation Anchondo-Lopez, Isaac U.S. Nuclear Regulatory Commission (NRC)
Michael Benson NRC John Bozga NRC Burton, Mat NRC Mat Burton NRC Jay Collins NRC Stephen Cumblidge NRC Robert Davis NRC Binoy Desai NRC Bart Fu NRC Emma Haywood NRC Allen Hiser NRC John Honcharik NRC Lois James NRC Varoujan Kalikian NRC Seung Min NRC Matthew Mitchell NRC Carol Moyer NRC Carol Nove NRC Cory Parker NRC Eric Reichelt NRC David Rudland NRC Atif Shaikh NRC John Tsao NRC Dan Widrevitz NRC On Yee NRC INDUSTRY PARTICIPANTS Name Affiliation David Van Allen Arizona Public Service Company Donald Armbruster Constellation Nuclear Joseph Buchanan Constellation Nuclear Ramon Cruz Constellation Nuclear Name Affiliation Rebecca Rice Constellation Nuclear Glenn Chatterton DC Cook Markus Burkardt Dominion Engineering, Inc. (Dominion)
Troy Meurer Dominion Glenn White Dominion Jim Cirilli Electric Power Research Institute (EPRI)
Craig Harrington EPRI Chris Wax EPRI Mark Ferlisi GSE TrueNorth Kevin J Hacker Services Truong V Vo Services Dale Brown Southern Nuclear Corey Thomas Southern Nuclear Maria Luisa Garcia Heras Tecnatom PUBLIC PARTICIPANTS Name Affiliation Austin Charles Keller public Rowland Walter Tedder Jr.
public unannounced public
- via email OFFICE NRR/DORL/LLPB/PM NRR/DORL/LLPB/LA NRR/DNRL/BC NRR/DORL/LLPB/BC NAME LJames*
DHarrison MMitchell RChang DATE 05/26/2022 06/03/2022 06/06/2022 06/06/2022 OFFICE NRR/DORL/LLPB/PM NAME LJames DATE 06/06/2022