ML12320A714

STP - Record of Conference Call-staff Questions on Response to B2137-4-102512

ML12320A714
Person / Time
Site:	South Texas
Issue date:	11/29/2012
From:	Daily J License Renewal Projects Branch 1
To:	South Texas
Daily J, 415-3873
References
TAC ME4936, TAC ME4937
Download: ML12320A714 (11)

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LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project, Units 1 and 2

SUMMARY

OF TELEPHONE CONFERENCE CALL HELD ON OCTOBER 25, 2012, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND STP NUCLEAR OPERATING COMPANY, CONCERNING STAFF INITIAL REVIEW OF APPLICANTS RESPONSE FOR FOLLOWUP REQUEST FOR ADDITIONAL INFORMATION B2.1.37-4, SELECTIVE LEACHING OF ALUMINUM BRONZE, FOR THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION (TAC NOS. ME4936 AND ME4937)

The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of STP Nuclear Operating Company (STPNOC or the applicant) held a telephone conference call on October 25, 2012, to discuss staff's initial reviews and possible followup questions related to the applicant's response to request for additional information (RAI) B2.1.37 -4, related to the selective leaching of aluminum bronze program, in the South Texas Project, Units 1 and 2 license renewal application (LRA). The telephone conference call was useful in clarifying staff concerns on the issue.

Enclosure 1 provides a listing of the participants and Enclosure 2 contains a summary of the discussion.

The applicant had an opportunity to comment on this summary.

J~:a;:e~~nager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosures:

As stated cc w/encls: Listserv

TELEPHONE CONFERENCE CALL SOUTH TEXAS PROJECT LICENSE RENEWAL APPLICATION LIST OF PARTICIPANTS October 25, 2012 PARTICIPANTS AFFILIATIONS John Daily Nuclear Reoulatorv Commission (NRC)

Bill Holston NRC John Wise NRC NRC NRC Arden Aldridoe STP Nuclear Operatino Company (STPNOC) I Ken Taplett STPNOC Richard Kersey__ STPNOC Geoff Eqan Intertek Russell Cioooia Intertek Garv Warner STARS Worley Parsons Center of Business ENCLOSURE 1

REQUEST FOR ADDITIONAL INFORMATION CONFERENCE CALL SOUTH TEXAS PROJECT, UNITS 1 AND 2 LICENSE RENEWAL APPLICATION SELECTIVE LEACHING OF ALUMINUM 8RONZE APPLICANT'S RESPONSE TO FOLLOWUP RAI 82.1.37-4 October 25,2012 The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of STP Nuclear Operating Company (STPNOC or the applicant) held a telephone conference call on October 25, 2012, to discuss staff's initial reviews and possible followup questions related to the applicant's response to request for additional information (RAI) 82.1.37-4, related to the selective leaching of aluminum bronze program, in the South Texas Project, Units 1 and 2, license renewal application (LRA). The telephone conference call was useful in clarifying staff concerns on the issue.

RAI 82.1.37-4 Response - discussion The staff discussed its initial review of the applicant's response and indicated several issues that need to be clarified, regarding the applicant's response to RAI 82.1.37-4. The clarifications will be the subject of a followup RAI. The staff identified implications from the applicant's response that related to issues in Part 50 of 10 CFR, and Part 54 of 10 CFR; the portion related Part 50 was reviewed and discussed by staff in the Division of Engineering (since it would normally not be a subject of license renewal) and the Part 54 portions were reviewed and discussed by staff in the Division of License Renewal.

Discussion led by Division of Engineering The staff noted that on August 16, 2012, it issued a safety evaluation (SE) in response to STPNOC's relief request RR-ENG-3-08 (ADAMS Accession No. ML12201A256). This request addressed leakage from an aluminum bronze valve located in ASM E Code Class 3 service water piping. The request stated that the leakage from the valve appeared to be the result of selective leaching of the aluminum bronze material, from which the valve is constructed.

In the SE, the staff authorized STPNOC's proposed alternative based on a SUbstantial lack of consequences associated with a failure of the valve. In the SE, the staff stated that it did not agree with the calculations which were provided as a means of demonstrating the continued structural adequacy of the subject valve. The basis for the staff's position was the use of non degraded material properties in the calculations. At that time the staff noted that sufficient data appropriate for use in those calculations did not exist.

Since the staff issued the subject SE, it has not identified any additional data which could be used as a basis for a demonstration of structural adequacy of aluminum bronze piping or fittings subject to selective leaching. Despite the fact that the staff has, in the past, granted relief for aluminum bronze components, the staff reiterated that, due to the currently recognized lack of adequate data demonstrating the material properties of selectively leached aluminum bronze, there is no structural integrity basis which it can use to authorize alternatives to the ASME Code for relief requests such as RR-ENG-3-08 going forward. The staff also stated that, in order to achieve an acceptable level of quality and safety, as required by regulation, a code compliant repair or replacement may be required unless, as was the case in RR-ENG-3-08, the consequences of failure of the component under consideration posed no significant safety risk.

ENCLOSURE 2

-2 The staff stated that resolution of this issue appeared to imply that the applicant do one of three paths:

• enter into a program to replace susceptible components

• be prepared to make repairs to degraded components in accordance with regulations, the ASME Code, and plant Technical Specifications

• develop an adequate basis which may be approved by the staff in authorizing alternatives in accordance with 10 CFR SO.SSa(a)(3)(ii)

The staff also stated that the applicant may, of course, identify or propose other potential resolution paths as well.

The staff noted that the development of such a basis (third option above) appeared to require the acquisition of sufficient data concerning the material properties of selectively leached aluminum bronze and crack size correlations to support calculations which can demonstrate the structural adequacy of these components. The quantity and quality of data necessary to support structural adequacy calculations for relief requests appeared to be identical to that necessary to support license renewal and the associated aging management program (AMP).

In summary, the staff stated that it appeared as though the applicant has several options to address the current licensing basis issue associated with selective leaching of aluminum bronze. The staff also stated that, if the applicant chose the option of relying upon relief requests, then additional data consistent with that required for the management of aging of these components is required to establish a technical basis for authorizing alternatives to Code repairs under most circumstances. The staff noted that discussions concerning the adequacy of data to support aging management are currently underway as part of the ongoing license renewal review.

Discussion led by Division of License Renewal In relation to license renewal, the staff discussed its initial review (and possible followup RAls) of the October 4,2012, RAI response (to RAI B2.1.37-4) related to the Selective Leaching of Aluminum Bronze plant-specific AMP, especially regarding the staff's ability to complete its final Safety Evaluation Report (SER) for the LRA. This discussion revolved around two specific needs:

(1) what is necessary in order to obtain reasonable assurance, issue the 'final SER, and present this to the full Advisory Committee on Reactor Safeguards (ACRS) committee; and (2) having continuing confirmation that the AMP will continue to adequately predict, maintain, and manage the effects of selective leaching of aluminum bronze components following issuance of a renewed license.

The staff stated that, as expressed through its RAls, the supplemental audit, and the recent public meeting, the staff's concerns with the (plant-specific) Selective Leaching of Aluminum Bronze AMP are summarized as follows:

1. The analyses used to demonstrate structural integrity do not incorporate dealloyed fracture toughness values and yield strength. Although the applicant stated that its modeling methodology makes this a moot point, the staff does not currently agree with this conclusion. In addition, the applicant stated that it validated the methodology by

- 3 conducting a proof test in 1994 (for ease of communication the staff will refer to this as an Analysis Confirmatory Test (ACT>>. The staff stated it recognized that if sufficient testing is conducted, an empirical basis can be established that could validate the analytical methodology used to demonstrate structural integrity. However, the staff does not agree that one test is sufficient to establish the validity of the analytical methodology.

Therefore, the staff stated that additional ACTs will have to be conducted to provide on the one hand, (1) reasonable assurance, and then subsequently, (2) continuing confirmation that degraded components will meet their intended functions.

2. The staff stated that while the AMP is based on external visual inspections, internal cracking has accompanied de-alloying in several instances. The staff stated that the applicant utilizes a correlation based on the observed outside and inside diameter dimensions of cracks and dealloying from four samples (eight for dealloying) sectioned in 1994. The staff's position is that it does not agree that this is a sufficient number of data points to establish an empirical basis for the acceptability of the correlation between outside diameter cracking and inside diameter cracks. Therefore, the staff concluded that additional profile exams (PE) will have to be conducted to provide on the one hand, (1) reasonable assurance, and on the other hand, (2) continuing confirmation, that external visual examination parameters can be used as an accurate projection of the degradation that is occurring throughout the volume of the fitting.

3. In addition, the staff stated that the ACTs and PEs would provide additional data related to material properties and progression of dealloying that are necessary to provide the (1) reasonable assurance, and subsequently, (2) continuing confirmation, that degraded components will meet their intended functions.

The staff stated that, in order to draw these points together, managing the selective leaching aging effect of the susceptible components as opposed to replacing them prior to the period of extended operation necessitates the following:

1. A methodology that utilizes a projection of internal cracking and dealloying in conjunction with localized stress analysis input and is capable of demonstrating structural integrity of degraded (Le., leaking) components.

2. Given that the applicant's currently-proposed program is based on an external visual examination, there must be the ability to project the configuration of internal degradation based upon the external examinations. The PEs are essential to demonstrate that, as was observed in the examination of degraded components in 1994, the dealloying is proceeding in essentially a plug-like manner. Should the degradation transition to a layer-type dealloying predominating over plug-like degradation, the linkage between the external visual examinations to the projection of the magnitude of internal degradation would no longer be valid. If this occurs, a fundamental precept of the AMP would be lost and the staff would not find the proposed program to be acceptable, absent some other means to confirm the internal degradation.

3. Finally, continuing testing and trending of degraded components material properties must occur through the end of the period of extended operation to ensure that installed susceptible components will continue to meet their intended functions.

-4 The staff stated that it recognizes that the changes to the applicant's AMP reflect the PE examinations and ACTs of leaking components discussed during the public meeting. However, subsequent to this meeting, the staff conducted further assessments as to how many PEs and ACTs should be conducted in order to: (a) achieve a sufficient level of information to provide reasonable assurance that the essential cooling water system will perform its intended functions during the period of extended operation, and (b) to provide continuing confirmation that the degree of degradation is enveloped by the provisions of the AMP. The staff stated that the results of this assessment are as follows:

Reasonable Assurance Continuing Confirmation 100% of leaking components until end of PE 22 PEO 20% of leaking components until end of ACT 3 sizes, 3 tests in each size PEO The staff noted that the tests to establish reasonable assurance must be completed prior to issuance of the final SER and therefore would not be included in the AMP. The staff stated it plans to make this clear in the followup RAI being developed. Given the current rate of emergent leakers, the staff also noted that this testing could take up to several years.

The staff also stated that the AMP, the UFSAR Supplement, and the related Commitments need to be revised to reflect the continuing confirmation testing. The staff believes that since there were eight PEs and one ACT conducted in 1994, the additional 14 PEs and eight ACTs will provide a sufficient basis for comparing the continued aging that has occurred in the intervening 18 years, and therefore with successful outcomes, provide reasonable assurance that the impact of selective leaching will continue to be consistent through the end of the period of extended operation. However, considering that (a) the Unit 2 renewed license will not expire until December 2048, (b) the importance of the essential cooling water system, and (c) further selective leaching degradation will continue to occur, the continuing confirmation testing will either demonstrate that the rate of degradation continues as it has in the past and therefore can be managed by the program (e.g., plug-like versus layer-like), or with trending, demonstrate the need to replace the susceptible components prior to signs of external leakage.

In that light, the staff stated that, should a PE demonstrate that layer-type dealloying is (or becomes) predominant over plug-type, or should any component be found to be inoperable, all susceptible fittings should be declared inoperable until a revised basis for operability is established. The staff stated that it based this on the conclusions that (a) the existing analytical methodology would be no longer valid if outside visual examinations cannot project internal degradation, and (b) when the first fitting would be found to be inoperable, it is likely that one or more of the remaining hundreds of fittings would also be inoperable.

The staff stated that it will establish a license condition for the renewed license that will include the number of continuing confirmation tests and actions required for conditions yielding unexpected results, as described above.

In addition, the staff stated that the applicant's RAI response did not address the minimum level of degradation (e.g., degree of dealloying) that a component must exhibit in order to be utilizable as an ACT test specimen. The staff noted that the possibility should be recognized that some removed leaking components may not be acceptable specimens for validating the analytical

- 5 methodology. As a side note, the staff stated that the applicant's response to RAI Part 3,

"[d]escribe how the percentage of dealloying is identified when testing specimens," does not account for areas where dealloying has started but not progressed to "completion" (i.e.,

depletion of leachable aluminum).

The staff stated that, regarding its request for additional information in relation to how a design factor is incorporated into STPNOC's operability evaluation for a leaking component, the response to date has been insufficient. Staff's specific questions are as follows (and will be included in the followup RAI):

• How is the external dimension of the indication sized?

• How is a singular rounded indication characterized?

• How are multiple in-line rounded indications characterized?

• Why does the correlation output produce an average crack size instead of the size of the inside crack?

• Precisely what design factor(s) are applied to the stress input?

The staff needs to understand these details in order to complete its evaluation of the acceptability of the analytical methods used to demonstrate structural integrity.

In summary, until sufficient PEs and ACTs are conducted and the program is amended to address the above issues, as well as others to be included in the upcoming followup RAI, the staff stated it cannot complete its evaluation of the Selective Leaching of Aluminum Bronze plant-specific AMP. The staff stated it plans to develop a followup RAI to address these comments as well as several other details. The staff also stated that it recognizes that significant progress has been made in regard to a common understanding of this pervasive degraded condition and enhancements to the applicant's proposed AMP, and appreciates the STPNOC staff's willingness to continue working through the details in a supportive manner.

The staff stated that it requested the call in order to share its thoughts prior to issuance of the RAI so that all may have

• the additional information required to complete the staff's evaluation of your program and produce a determination of reasonable assurance of the adequacy of this AMP; and

• a more clear understanding of both the issues and the implications related to discovering a future leaking fitting in SPTNOC's current operating period.

Following a brief question-answer period between the staff and the applicant, the call was ended. The applicant indicated it would take the elements of the call into account as it prepares responses to any followup RAls.

ML12320A714 "'concurred via email OFFICE LA:RPB1 :DLR'" PM:RPB1:DLR BC:RPB1 :DLR PM:RPB1:DLR NAME YEdmonds JDaily DMorey JDaily DATE 11120/12 11/27/12 11/28/12 11/29/12 Memorandum to STPNOC from J. Daily dated November 29, 2012

SUBJECT:

Summary of Telephone Conference Call conducted on October 25,2012 DISTRIBUTION:

HARD COPY:

DLRRF E-MAIL:

PUBLIC RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRpb2 Resource RidsNrrDlrRerb Resource RidsNrrDlrRpob Resource RidsNrrDraApla Resource RidsOgcMailCenter JDaily TTran WHolston DMclntyre,OPA BSingal, DORL WWalker, RIV JDixon, RIV BTharakan, RIV WMaier, RIV VDricks, RIV NOKeefe, RIV AVegel, RIV GPick, RIV DAiley, DE TLupold, DE

November 29, 2012 LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project, Units 1 and 2

SUMMARY

OF TELEPHONE CONFERENCE CALL HELD ON OCTOBER 25, 2012, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND STP NUCLEAR OPERATING COMPANY, CONCERNING STAFF INITIAL REVIEW OF APPLICANT'S RESPONSE FOR FOLLOWUP REQUEST FOR ADDITIONAL INFORMATION B2.1.37-4, SELECTIVE LEACHING OF ALUMINUM BRONZE, FOR THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION (TAC NOS. ME4936 AND ME4937)

The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of STP Nuclear Operating Company (STPNOC or the applicant) held a telephone conference call on October 25, 2012, to discuss staff's initial reviews and possible followup questions related to the applicant's response to request for additional information (RAI) B2.1.37-4, related to the selective leaching of aluminum bronze program, in the South Texas Project, Units 1 and 2 license renewal application (LRA). The telephone conference call was useful in clarifying staff concerns on the issue. provides a listing of the participants and Enclosure 2 contains a summary of the discussion.

The applicant had an opportunity to comment on this summary.

IRA!

John Daily, Senior Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosures:

As stated cc w/encls: Listserv DISTRIBUTION: See next page ADAMS Accession No.: ML12320A714 *concurred via email OFFICE LA:RPB1 :DLR

• PM:RPB1 :DLR BC:RPB1 :DLR PM:RPB1 :DLR NAME YEdmonds JDaily DMorey JDaily DATE 11/20/12 11/27/12 11/28/12 11/29/12 OFFICIAL RECORD COpy

Memorandum to STPNOC from J. Daily dated November 29, 2012

SUBJECT:

Summary of Telephone Conference Call conducted on October 25, 2012 DISTRI BUTION:

HARD COPY:

DLR RF E-MAIL:

PUBLIC RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRpb2 Resource RidsNrrDlrRerb Resource RidsNrrDlrRpob Resource RidsNrrDraApla Resource RidsOgcMailCenter JDaily TTran WHolston DMclntyre, OPA BSingal, DORL WWalker, RIV JDixon, RIV BTharakan, RIV WMaier, RIV VDricks, RIV NOKeefe, RIV AVegel, RIV GPick, RIV DAiley, DE TLupold, DE