ML23219A108

SLRA - Requests for Additional Information - Set 2

ML23219A108
Person / Time
Site:	Monticello
Issue date:	08/07/2023
From:	Mary Johnson NRC/NRR/DNRL/NLRP
To:	Hafen S Monticello, MN
References
Download: ML23219A108 (1)

Text

1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION MONTICELLO SLRA SAFETY REVIEW NORTHERN STATES POWER COMPANY MONTICELLO, UNIT 1 DOCKET NO. 05000263 ISSUE DATE: 8/07/2023 RAI B.2.3.21-1 Regulatory Basis:

10 CFR 54.21(a)(3) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. One of the findings that the staff must make to issue a renewed license (10 CFR 54.29(a)) is that actions have been identified and have been or will be taken with respect to managing the effects of aging during the period of extended operation on the functionality of structures and components that have been identified to require review under 10 CFR 54.21, such that there is reasonable assurance that the activities authorized by the renewed license will continue to be conducted in accordance with the current licensing basis. In order to complete its review and enable making a finding under 10 CFR 54.29(a), the staff requires additional information in regard to the matters described below.

Background:

SLRA Table 3.3.2-9, Fire System - Summary of Aging Management Evaluation, states that loss of material due to selective leaching for gray cast iron piping exposed to soil will be managed by the Selective Leaching program.

SLRA Section B.2.3.21, Selective Leaching, states the following:

Each of the one-time and periodic inspections for the various material and environment populations comprises a 3 percent sample or a maximum of 10 components.

For raw water, waste water, and soil environments, the AMP includes opportunistic and periodic visual inspections of selected components that are susceptible to selective leaching, coupled with mechanical examination techniques. Destructive examinations of components to determine the presence of and depth of dealloying through-wall thickness are also conducted.

The plant-specific operating experience summary in SLRA Section B.2.3.21 does not describe any operating experience or results of inspections related to gray cast iron piping exposed to soil.

NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192, states the following regarding the staffs basis for reducing the extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR

2 guidance) when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance):

1. Opportunistic inspections will be conducted throughout the period of extended operation whenever components are opened, buried, or submerged surfaces are exposed, whereas opportunistic inspections were not recommended in the previous version of AMP XI.M33;

2. Destructive examinations provide a more effective means to detect and quantify loss of material due to selective leaching;

3. The slow growing nature of selective leaching generally coupled with the inspections conducted prior to the initial period of extended operation provides insights into the extent of loss of material due to selective leaching that can be used in the subsequent period of extended operation;

4. The staffs review of many license renewal applications has not revealed any instances where loss of intended function has occurred due to selective leaching;

5. The staffs review of industry OE has not detected any instances of loss of material due to selective leaching, which resulted in a loss of intended function for the component; and

6. Regional inspector input (provided based on IP 71003, Post-Approval Site Inspection for License Renewal,) that selective leaching has been noted during visual and destructive inspections; however, no instances have been identified where there was the potential for loss of intended function.

The NRC issued Information Notice (IN) 2020-04, Operating Experience Regarding Failure of Buried Fire Protection Main Yard Piping, to inform the industry of operating experience involving the loss of function of buried gray cast iron fire water main yard piping due to multiple factors, including graphitic corrosion (i.e., selective leaching), overpressuration, low-cycle fatigue, and surface loads. As noted in the IN, a contributing cause to the failure of buried gray cast iron piping at Surry Power Station was the external reduction in wall thickness at several locations due to graphitic corrosion. In this instance, the thin asphalt external coating could not protect the pipe from the highly corrosive soil environment.

As amended by Subsequent License Renewal Application Supplement 2|letter dated June 26, 2023]] (ML23177A218), SLRA Section B.2.3.16, Fire Water System, states [t]he external coating of buried cast iron or ductile iron piping is a bituminous coating of either coal-tar or asphalt base approximately 1 mil [thousandth of an inch] thick.

Issue:

The recommended extent of inspections in GALL-SLR AMP XI.M33 are based on the six conditions noted by the staff in NUREG-2222. The staffs comparison to these six conditions to the Selective Leaching program at Monticello follows:

Based on its review of SLRA Section B.2.3.21, the staff noted that opportunistic inspections and destructive examinations for selective leaching will be performed, consistent with the first and second conditions in NUREG-2222.

Based on its review of plant-specific operating experience in SLRA Section B.2.3.21, the staff could not determine if selective leaching inspections have been conducted for gray

3 cast iron piping exposed to soil. Based on this observation (i.e., inspections for this material and environment combination may not have been performed prior to the initial period of extended operation), the third condition in NUREG-2222 may not be met at Monticello for gray cast iron piping exposed to soil.

The fourth, fifth, and sixth conditions in NUREG-2222 focus on the staffs review of industry operating experience not identifying any instances of loss of material due to selective leaching which had resulted in a loss of intended function for the component. Based on recent industry operating experience documented in IN-2020-04, the last three conditions in NUREG-2222 are no longer applicable for gray cast iron piping exposed to soil. Since these conditions are no longer applicable (i.e., there is now industry operating experience involving loss of material due to selective leaching which resulted in a loss of intended function for gray cast iron piping exposed to soil), the staff requires additional information to determine if the reduced extent of inspections in GALL-SLR AMP XI.M33 are appropriate for this material and environment combination.

The staff also noted buried gray cast iron piping at Monticello is coated with a thin external bituminous coating, which was a contributing cause to a failure of buried gray cast iron piping at Surry Power Station as documented in IN-2020-04.

Request:

Provide additional operating experience (or other technical justification) to demonstrate that the extent of inspections in GALL-SLR AMP XI.M33 (i.e., 3 percent with a maximum of 10 components) are appropriate for gray cast iron piping exposed to soil.

RAI B.2.3.27-1 Regulatory Basis:

10 CFR 54.21(a)(3) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. One of the findings that the staff must make to issue a renewed license (10 CFR 54.29(a)) is that actions have been identified and have been or will be taken with respect to managing the effects of aging during the period of extended operation on the functionality of structures and components that have been identified to require review under 10 CFR 54.21, such that there is reasonable assurance that the activities authorized by the renewed license will continue to be conducted in accordance with the current licensing basis. In order to complete its review and enable making a finding under 10 CFR 54.29(a), the staff requires additional information in regard to the matters described below.

Background:

As amended by Subsequent License Renewal Application Supplement 2|letter dated June 26, 2023]] (ML23177A218), SLRA Table A-3, List of SLR Commitments and Implementation Schedule, Commitment 30(e) states the following (in part):

[p]erform inspections of buried and underground piping and tanks in accordance with NUREG-2191 Table XI.M41-2 Preventive Action Category C for buried steel and stainless steel components, unless a reevaluation of future OE [operating experience] and soil conditions determines that another Preventive Action Category is more applicable. In the 10-year period

4 prior to and during SPEO [subsequent period of extended operation] for each 10-year interval, perform buried and underground piping and tanks inspections in accordance with the Preventive Action Category C as outlined in NUREG-2191 Table XI.M41-2.

SLRA Section B.2.3.27, Buried and Underground Piping and Tanks, includes the following enhancement (in part):

[c]larify that inspections of buried and underground piping and tanks within the applicable plant systems will be conducted in accordance with NUREG-2191 Table XI.M41-2 Preventive Action Category F for buried steel and stainless steel piping, unless a reevaluation of cathodic protection performance, future OE, or soil conditions determines that another Preventive Action Category is more applicable.

Preventive Action Category C cited in GALL-SLR Report Table XI.M41-2, Inspection of Buried and Underground Piping and Tanks, is applicable to plants where the cathodic protection system has met availability and effectiveness goals.

Issue:

The staff noted the following based on its comparison of the commitment and enhancement cited above:

1. For buried steel piping, Preventive Action Category C is referenced in the commitment; however, Preventive Action Category F is referenced in the enhancement. The staff seeks clarification with respect to why different Preventive Action Categories are cited in the enhancement and commitment.

2. The staff seeks clarification with respect to why cathodic protection performance is referenced in the enhancement but not in the commitment. Preventive Action Category C is applicable to plants where the cathodic protection system has met availability and effectiveness goals.

Request:

1. Provide clarification with respect to why different Preventive Action Categories are cited in the enhancement and commitment for buried steel piping and revise the SLRA (as appropriate).

2. State the basis for not including cathodic protection performance in the commitment.

Alternatively, revise the SLRA (as appropriate) to clarify that the number of inspections for buried steel piping are based on cathodic protection performance.

RAI B.2.3.27-2 Regulatory Basis:

10 CFR 54.21(a)(3) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. One of the findings that the staff must make to issue a renewed license (10 CFR 54.29(a)) is that actions have been identified and have been or will be taken with respect to managing the effects of aging during the period of extended operation on the functionality of structures and components

5 that have been identified to require review under 10 CFR 54.21, such that there is reasonable assurance that the activities authorized by the renewed license will continue to be conducted in accordance with the current licensing basis. In order to complete its review and enable making a finding under 10 CFR 54.29(a), the staff requires additional information in regard to the matters described below.

Background:

SLRA Section B.2.3.27, Buried and Underground Piping and Tanks, includes the following enhancement (in part):

[c]larify the guidance for piping inspection location selection as follows: (a) a risk ranking system software incorporates inputs that include coating type, coating condition, cathodic protection efficacy, backfill characteristics, soil resistivity, pipe contents, and pipe function During its audit, the staff reviewed SL-008367, Nuclear Management Company Monticello Nuclear Generating Plant Cathodic Protection System Evaluation Report, Revision 0 and noted pipe-to-soil potential measurements as negative as -23,921 mV with respect to a zinc reference cell between the years 1976 and 2003.

GALL-SLR Report AMP XI.M41, Buried and Underground Piping and Tanks, recommends a limiting critical potential of -1,200 mV to prevent damage to coatings or base metals.

Issue:

Based on its observation during the audit noted above, the staff seeks clarification with respect to why cathodic overprotection is not used as an input for determining piping inspection locations. Cathodic protection efficacy is currently referenced as an input; however, the staff seeks clarification with respect to whether this considers areas that have been overprotected.

Request:

State the basis for why cathodic overprotection is not used as an input for determining piping inspection locations. Alternatively, revise the SLRA (as appropriate) to consider cathodic overprotection as an input for determining piping inspection locations.

RAI B.2.3.15-1 Regulatory Basis:

Section 54.21(a)(3) of Title 10 of the Code of Federal Regulations (10 CFR) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. One of the findings that the U.S.

Nuclear Regulatory Commission (NRC) staff must make to issue a renewed license (10 CFR 54.29(a)) is that actions have been identified and have been or will be taken with respect to managing the effects of aging during the period of extended operation on the functionality of structures and components that have been identified to require review under 10 CFR 54.21, such that there is reasonable assurance that the activities authorized by the renewed license will continue to be conducted in accordance with the current licensing basis. In order to complete its review and enable making a finding under 10 CFR 54.29(a), the staff requires additional information in regard to the matters described in the requests for information.

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Background:

The Monitoring and Trending program element in Aging Management Program (AMP) XI.M26, Fire Protection, in Volume 2 of NUREG-2191, Generic Aging Lessons learned for Subsequent License Renewal (GALL-SLR) Report (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17187A031), states the following:

The results of inspections of the aging effects of cracking and loss of material on fire barrier penetration seals, fire barriers, fire damper assemblies, and fire doors are trended to provide for timely detection of aging effects so that the appropriate corrective actions can be taken.

The performance of the halon/CO2 fire suppression system is monitored during the periodic test to detect any degradation in the system. These periodic tests provide data necessary for trending.

The Detection of Aging Effects program element in GALL-SLR Report AMP XI.M26 states, Visual inspections of the halon/CO2 or clean agent fire suppression system are performed to detect any sign of corrosion before the loss of the component intended function. The Acceptance Criteria program element in GALL-SLR Report AMP XI.M26 states, Also, inspection results for the halon/CO2 or clean agent fire suppression system are acceptable if there are no indications of excessive loss of material. While GALL-SLR does not explicitly state that the halon fire suppression system inspection results be trended, the NRC staff notes that the expectation would be that the results be trended since there could be loss of material that is not considered excessive and determined not to result in a loss of intended function. This information would be trended to monitor how the condition of the halon fire suppression system is changing over time in order to take timely corrective action.

Issue:

The enhancement to the Monitoring and Trending program element in Subsequent License Renewal Application (SLRA) Section B.2.3.15 states, Trend the inspection results for timely detection of aging effect so that appropriate corrective actions can be taken. However, SLRA Table A-3 states, Trend the inspection results on fire barrier penetration seals, fire barriers, fire damper assemblies, and fire doors for timely detection of aging effect so that appropriate corrective actions can be taken. SLRA Section B.2.3.15 appears to include trending of all Fire Protection program inspection results, while SLRA Table A-3 appears to exclude the halon fire suppression system.

Section 3.3 of Report No. XCELMO00017-REPT-065, Subsequent License Renewal Aging Management Program Basis Document - Fire Protection (basis document), states that Section 4.5 of the basis document documents that the Cable Spreading Room Halon fire suppression system procedures specify trending of inspection results of this system. However, the NRC staff did not identify where this documentation is made in Section 4.5, and did not identify documentation related to trending periodic test results. The staff does note that it states, The MNGP Cable Spreading Room halon fire suppression system is monitored during the periodic tests to detect any degradation in the system. In addition, the staff did not identify where Revision 28 of Procedure 0328, Cable Spreading Room Halon System, discusses trending of inspection or periodic test results.

7 Table 1 in Section 7.0 of the basis document states that Procedure 0328 will be updated to trend inspection results and where practical, project degradation until the next scheduled inspection.

However, it does not state it will be updated to include trending of periodic test results.

During the audit of the Fire Protection program, the applicant stated that the halon fire suppression system in the Cable Spreading Room does not require enhancement for trending because trending of the periodic tests are already performed under FP-E-MR-03, Maintenance Rule Monitoring. However, FP-E-MR-03 does not discuss trending the periodic tests of the halon fire suppression system, and does not reference Procedure 0328 or the basis document.

In addition, Procedure 0328 and the basis documents do not reference FP-E-MR-03.

Therefore, it is unclear to the NRC staff how trending of the halon fire suppression system inspection and periodic test results are performed, and will continue to be performed during the subsequent period of extended operation (SPEO), given the lack of clear documentation in plant-specific procedures and documents.

Request:

Consistent with the Detection of Aging Effects and Monitoring and Trending program elements in GALL-SLR Report AMP XI.M26, please provide sufficient information demonstrating that trending of the halon fire suppression system inspection and periodic test results will be performed during the SPEO, including where the requirements are documented in plant-specific procedures. Alternatively, revise enhancement 18.b) in SLRA Table A-3 to include trending the halon fire suppression system inspection and periodic test results, and, for consistency, the corresponding enhancement to the Monitoring and Trending program element in SLRA Section B.2.3.15.

RAI B.2.3.15-2

Background:

The Acceptance Criteria program element in GALL-SLR Report AMP XI.M26 states, no significant indications of cracking and loss of material of fire barrier walls, ceilings, and floors and in other fire barrier materials.

Figure 5.3 in Revision 23 of 4 AWI-08.01.00, Fire Protection Program Plan, and Revision 50 of Procedure 0275-02, Fire Barrier Wall, Damper and Floor Inspection, state to consider cracks greater than 0.25 inches wide in walls, floors, and ceilings. However, these documents did not cite a reference for the basis for this crack width limit.

During the audit of the Fire Protection program, the applicant stated that the basis for the crack width limit is in Section 3.2.18.2 of MPS-0924, Installation of Electrical and Mechanical Penetration Seals. The applicant further stated that the 0.25 inch crack width can be extrapolated to cracks in fire barriers because Section 3.2.18 of MPS-0924 states the specification is for sealing openings in hollow walls, with or with out a penetrant or existing sealant material.

Issue:

Section 3.2.18 of MPS-0924 provides instructions (Sections 3.2.18.1, 3.2.18.2, and 3.2.18.3) for installing hollow wall fire stop seals for sealing of openings in hollow-walls with gypsum wallboard surface, either single or double layer, with or without penetrant, and with or without

8 existing sealant materials. Section 3.2.18.2 of MPS-0924 provides instructions for applying thermal board or gypsum wallboard patches. It states, Patch may be in sections, end should be cut to clear penetrant with no more than 1/4 [inch] gap width. Section 3.2.18.3 of MPS-0924 includes instructions for applying a thermal mastic to joints between mating surfaces, edges of patch, cracks between patch sections, and between patch penetrant. Therefore, it appears that the 0.25 inch gap width in Section 3.2.18.2 would be covered by thermal mastic and not left uncovered.

It is unclear to the NRC staff how a 0.25 inch wide gap between the patch and penetrant that will eventually be covered by thermal mastic can be extrapolated to cracks in other fire barriers.

Request:

Please provide sufficient information, including references, to support extrapolating the 0.25 inch wide gap in MPS-0924 to other fire barriers.

RAI 4.3.2-2 Regulatory Basis:

Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.

Background:

In Enclosure 10a of its supplement dated July 18, 2023 (ADAMS Accession No. ML23199A154),

the applicant explained that there is no fatigue waiver evaluation done for the instrumentation nozzles and jet pump instrumentation nozzles in accordance with the ASME Code Section III, Paragraph N-415.1 or NB-3222.4(d) provisions for fatigue waiver.

Issue:

Given the lack of fatigue waiver evaluation in accordance with ASME Code Section III Paragraph N-415.1 or NB-3222.4(d), the staff needs additional information on how the applicant ensures that the cumulative usage factor (CUF) values for these nozzles do not exceed the fatigue design limit (1.0).

Request:

1. Clarify whether the stresses applied to the instrumentation nozzles and jet pump instrumentation nozzles are less than the fatigue endurance limit. If not, discuss the following: (1) whether the other reactor pressure vessel nozzles or components evaluated in SLRA Section 4.3.3 are bounding for the instrumentation nozzles and jet pump instrumentation nozzles in terms of the applied transient stresses and resultant CUF; and (2) the basis of determining that the other nozzles or components are bounding for the instrumentation nozzles and jet pump instrumentation nozzles.

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2. If the Fatigue Monitoring aging management program will be used to manage the aging effect of cumulative fatigue damage for the instrumentation nozzles and jet pump instrumentation nozzles, describe how the program will be used to manage the aging effect for these nozzles.