ML21041A450
| ML21041A450 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 02/09/2021 |
| From: | Herr M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CCN: 21-14 | |
| Download: ML21041A450 (13) | |
Text
Exelon Generation.
10CFR 50.55a CCN: 21-14 February 9, 2021 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 2 Renewed Facility Operating License No.
DPR-44 NRC Docket No. 50-277
Subject:
Submittal of the lnservice Inspection (ISi) Owner's Activity Report (OAR) for the 23rd Refueling Outage for Unit 2 Attached is the ISi Owner's Activity Report for the 23rd refueling cycle covering ISi activities that span the third period of the 4th ISi inspection interval and the first period of the 5th ISi inspection interval for Unit 2. This report is submitted in accordance with 10CFR 50.55a(b)(2)(xxxii); the ASME Section XI , Article IWA-6200; ASME Code Case N-532-4; and ASME Code Case N-532- 5.
In addition to the OAR-1 report, the following two evaluations are also being submitted:
- 1. EC 633079 Moisture Barrier Inaccessible Areas Evaluations is being submitted in accordance with 10CFR 50.55a(b)(2)(ix)(A)(2).
- 2. EC 632895 CH-MB Flaw Evaluation is being submitted in accordance with ASME Section XI, Paragraph IWB-3114.
If you have any questions or require additional information, please contact Ben Jordan at 717-456-4583.
Sincerely, Matthew J. Herr Site Vice President Peach Bottom Atomic Power Station Attachment cc: USNRC, Regional Administrator, Region 1 USNRC, Senior Resident Inspector, PBAPS W. DeHaas, Commonwealth of Pennsylvania S. Seaman, State of Maryland B. Watkins, PSEG
FORM OAR-1 OWNERS ACTIVITY REPORT Report Number P2R23 Plant Peach Bottom Atomic Power Station, 1848 Lay Road, Delta, PA 17314 Unit No. 2 Commercial Service Date July 5, 1974 Refueling Outage Number P2R23 (if applicable)
Current Inspection Interval ISI = Fourth & Fifth Inspection Interval / CISI = Second & Third Inspection Interval (1st, 2nd, 3rd, 4th, other)
Current Inspection Period Third & First Inspection Period (ISI and Containment ISI)
(1st, 2nd, 3rd )
ASME Section XI 2001 Ed. w/2003 Add. (4th ISI/2nd CISI Edition and Addenda of Section XI applicable to the Inspection Plans Interval), ASME Section XI 2013 Edition (5th ISI/3rd CISI Interval) 4th/2nd Interval Plans, ER-PB-330-1001 Rev. 0 (8/30/18)
Date and Revision of Inspection Plans 5th/3rd Interval Plans, ER-PB-330-1001 Rev. 1 (12/13/18), Rev. 2 (10/3/19) Rev. 3 (8/13/2020) Rev. 4 (10/16/2020)
Edition and Addenda of Section XI applicable to repair/replacement activities, if different than the inspection plans Same as above Code Cases used: N-532-5, N-613-2, N-638-7, N-702, N-716-1, N-747, N-798, N-800 CERTIFICATE OF CONFORMANCE I certify that (a) the statements made in this report are correct; (b) the examinations and tests, meet the Inspection Plan as required by the ASME Code,Section XI; and (c) the repair/replacement activities and evaluations supporting the completion of P2R23 conform to the requirements of Section XI (refueling outage number)
Signed Benjamin Jordan, ISI Program Owner Date 2/5/2021 (Owner or Owners designee. Title)
CERTIFICATE OF INSERVICE INSPECTION I, the undersigned, holding a valid commission issued by the National Board of Boiler and Pressure Vessel Inspectors and employed by Hartford Steam Boiler Inspection and Insurance Company have inspected the items described in this Owner's Activity Report, and state that, to the best of my knowledge and belief, the Owner has performed all activities represented by this report in accordance with the requirements of Section XI.
By signing this certificate neither the Inspector nor his employer makes any warranty, expressed or implied concerning the repair/replacement activities and evaluation described in this report. Furthermore, neither the Inspector nor his employer shall be liable in any manner for any personal injury or property damage or a loss of any kind arising from or connected with this inspection.
Commissions (Inspectors Signature) (National Board Number and Endorsement)
Date Page 1 of 3
TABLE 1 ITEMS WITH FLAWS OR RELEVANT CONDITIONS THAT REQUIRED EVALUATION FOR CONTINUED SERVICE Examination Examination Item Category Number Item Description Evaluation Description As found condition evaluated by engineering under EC 633079 and E-A E1.30 Damaged Moisture Barrier determined to be acceptable.
Corrective measures were taken under WO 04997289.
External corrosion and coatings conditions evaluated by engineering External corrosion and coating loss E-A E1.11 under A/R 04379999-02 and on external Torus determined acceptable with no corrective measures required.
As found condition evaluated by CH-MB multiple new indications that engineering under EC 632895 and B-A B1.22 were not acceptable per the IWB-determined to be acceptable in 3510 table accordance with IWB-3600.
As found condition repaired and one cycle justification per EC 632907.
Leak found at N-16A nozzle during B-P B15.10 Relief Request I5R-14 and the B-P Pressure Test evaluations submitted to NRC.1
- 1. Relief Request submitted on November 4, 2020 (ML20309B020). Flaw evaluations submitted on November 24, 2020 under ML20329A345 and ML20329A346.
Page 2 of 3
TABLE 2 ABSTRACT OF REPAIR/REPLACEMENT ACTIVITIES REQUIRED FOR CONTINUED SERVICE Code Item Description Date Repair/Replacement Class Description Of Work Completed Plan Number Performed half nozzle repair 1 N-16A Nozzle based on leak found during B-P 11/14/2020 20-113 pressure test.
Page 3 of 3
Engineering Change Company Name : EXELON GENERATION CO.,LLC Print Date: 11/08/2020 EC Number : 0000632895 001 Status/Date : CLOSED 11/08/2020 Facility : PEA PEACH BOTTOM ATOMIC POWER STATION Type/Sub-type: EVAL MECH Page: 1 EC
Title:
ASME SECTION XI FLAW EVALUATION - WELD CH-MB P2R23 INDICATIONS 16 AND 28 Mod Nbr : KW1: SR KW2: KW3: KW4: KW5:
Master EC : N Work Group : Temporary : N Outage : Y Alert Group: A5452NESDM Aprd Reqd Date:
WO Required : Image Addr : Exp Insvc Date:
Adv Wk Appvd: N Alt Ref. : Expires On : 08/04/2023 Auto-Advance: Y Priority : Auto-Asbuild : N Caveat Outst: N Department : Discipline :
Resp Engr : TRAVIS GEHMAN Location :
Units Fac Unit Description PEA 02 UNIT TWO Outages Fac Unit Outage Description PEA P2R23 UNIT 2 REFUEL, CYCLE 23 Systems Fac System Description PEA 04 REACTOR PRESSURE VESSEL & INTE
Engineering Change Print Date: 11/08/2020 EC Number : 0000632895 001 Status/Date : CLOSED 11/08/2020 Facility : PEA Type/Sub-type: EVAL MECH Page: 1 EC
Title:
ASME SECTION XI FLAW EVALUATION - WELD CH-MB P2R23 INDICATIONS 16 AND 28 Mod Nbr : KW1: SR KW2: KW3: KW4: KW5:
Master EC : N Work Group : Temporary : N Outage : Y Alert Group: A5452NESDM Aprd Reqd Date:
WO Required : Image Addr : Exp Insvc Date:
Adv Wk Appvd: N Alt Ref. : Expires On : 08/04/2023 Auto-Advance: Y Priority : Auto-Asbuild : N Caveat Outst: N Department : Discipline :
Resp Engr : TRAVIS GEHMAN Location :
Milestone Date PassPort Name Req By 110-PREPARE EC 11/06/2020 E028493 GEHMAN TRAVIS APPROVED 120-REVIEW EC 11/07/2020 RUFOBX RUFO BRIAN APPROVED I performed an independent review of this revision. I agree with the inputs, methodology, and conclusion.
210-DEPT RVW-EP 11/08/2020 E114373 JORDAN BENJAMIN APPROVED ISI Program review performed by Ben Jordan, PBAPS ISI Program Owner 300-APPROVE EC 11/08/2020 U001JL7 LAVERDE JULIAN APPROVED
EC 632895 Rev. 0 Page 1 of 3 TITLE: ASME Section XI Flaw Evaluation - Weld CHMB P2R23 Indications 16 and 28 This Engineering Technical Evaluation was prepared in accordance with CCAA309101 Rev. 15. An HUAA1212 Rev. 10 Risk Ranking was performed with the following results and compensating methods:
Consequence Risk Factor:
[M.1] - Errors introduced with operational consequences: ISI program review Human Performance Risk Factors:
[H.4] - Knowledge/experience gaps: Design reviewer has ISI experience
[H.5] - First time task: Perform walkthrough of task This evaluation will require an independent review as it affects safety related components.
Revision 1: This revision does not impact the classification as a Technical Evaluation, the HUAA1212 review performed, or the review requirements of revision 0.
1.0 REASON FOR EVALUATION/SCOPE A scheduled ISI inspection of the Unit 2 RPV head during P2R23 identified indications in weld CHMB that do not meet the acceptance criteria of ASME Section XI Table IWB35101 and require analysis per the requirements of IWB3600 to determine if they are acceptable for continued service (IRs 4380356/4382547). This technical evaluation will use a 2002 GEHitachi flaw evaluation report [Ref. 1] (referred to as the 2002 report in this evaluation) of weld CHMB to determine if the P2R23 flaws are bounded by the previous 2002 evaluation and acceptable for continued service. This methodology mirrors that used to evaluate and accept a CHC2 weld flaw in P2R18 [Ref 3].
Revision 1: IR 4382547 documents an additional unacceptable weld CHMB indication (#28) per ASME Section XI Table IWB35101. This technical evaluation revision will analyze indication 28 IAW the requirements of IWB 3600 to determine if it is acceptable for continued service. Revision 1 changes are indicated with revision bars in the left margin.
2.0 DETAILED EVALUATION The reactor pressure vessel closure head at Peach Bottom Atomic Power Station, Unit 2 was ultrasonically (UT) examined during P2R23 in accordance with the Peach Bottom Fifth Ten Year ISI Interval Plan, which is committed to the 2013 Edition of ASME Section XI [Ref. 4].
There were multiple indications noted in the Closure Head Meridional Weld (CHMB). All but two of the indications either were deemed acceptable based on the ASME Section XI, Table IWB35101 or by previous evaluation. Indications #16 and #28 from the P2R23 inspection require evaluation per IWB3600 to allow continued operation. Indication 16 was presented in GE Report CNF ISI007 (Attachment 1) [Ref. 2] and indication 28 was presented in GE Report CNF012 (Attachment 2) [Ref.5].
In 2002, GEHitachi performed a flaw evaluation for multiple indications on weld CHMB. This technical evaluation will use that report (G080VC301) to determine if the new indications are bounded. In order to do so, the following items were evaluated/confirmed:
- 1. Flaw Size/Type:
The 2002 report evaluated 16 different surface flaws that were not acceptable per ASME Section XI, Table IWB35101. P2R23 flaw #16 has a length of L = 0.9 and depth of a = 0.16 (a/L = 0.1778). There
EC 632895 Rev. 0 Page 2 of 3 are multiple indications in the 2002 report that bound the P2R23 flaw, with the largest having a length L
= 3.75 and depth a = 0.25 (a/L = 0.0667).
Indication 16 is a surface flaw with a length to depth aspect ratio that is larger than the bounding 2002 report flaw. The stress intensity factor (K) increases as aspect ratio decreases, as seen in Table 41 of the 2002 report. Therefore, the flaw size, type, and stress intensity factor for P2R23 indication 16 are bounded by the 2002 report.
Revision 1: P2R23 flaw 28 has a length of L = 2.0 and depth of a = 0.15 (a/L = 0.075). This surface flaw has a length to depth aspect ratio that is larger than the bounding 2002 report flaw. The stress intensity factor (K) increases as aspect ratio decreases, as seen in Table 41 of the 2002 report. Therefore, the flaw size, type, and stress intensity factor for P2R23 indication 28 are bounded by the 2002 report.
- 2. Since the 2002 evaluation, PBAPS has undergone an extended power uprate (EPU). However, it was confirmed that the bounding loads did not change since the 2002 report:
The following assumptions were used in the 2002 report and remain valid.
The boltup temperature is 70 F. This assumption is acceptable per ambient temperature conditions at boltup.
The test pressure and temperature are 1050 psi and 169 F. Verified per STO080500(680)2.
- 3. Since the 2002 evaluation, PBAPS has received a subsequent license to allow operation up to 80 years.
The 2002 report evaluated a bounding fatigue crack growth of 0.025 using the 60year license at the time. The fatigue crack growth can conservatively be increased using the longer operation period by scaling out the time period: 0.025 x 80/60 = 0.033. This growth is inconsequential and would remain bounded by the 2002 flaw referenced above.
- 4. It was verified that the applicable sections of ASME Section XI did not change. Therefore, the 2002 report methodology remains valid.
Based on the above considerations, P2R23 indications 16 and 28 are bounded in flaw characteristics and evaluation method performed in 2002 GE report G080VC301.
3.0 CONCLUSION
S/FINDINGS Per IWB3132.3, Acceptance By Analytical Evaluation, P2R23 Indications 16 and 28 on weld CHMB, as detailed in the Attachment 1 and 2 reports, have been evaluated as described in IWB3600 and meet the acceptance criteria of IWB3600. Weld CHMB is acceptable for continued service and is predicted to be acceptable through end of plant life. In accordance with IWB2420, successive exam requirements will need to be evaluated. This is being tracked via assignment 0438035602.
Per IWB3134(b) this analytical evaluation must be submitted to the regulatory authority having jurisdiction at the plant site (i.e. NRC). Assignment 0438035603 has been generated to track this submittal.
Revision 1: A note has been added to the above assignments to reference the addition of indication 28 to this technical evaluation.
EC 632895 Rev. 0 Page 3 of 3
4.0 REFERENCES
- 1. G080VC301, The Evaluation of Indications in Peach Bottom Unit 2 Vessel Closure Head for Continued Operation.
- 3. Evaluation A111853002, Technical Evaluation for U2 RPV Closure Head to Flange Weld (CHC2) Indication
- 4. ASME Boiler and Pressure Vessel Code,Section XI, Rules for InService Inspection of Nuclear Power Plant Components, 2013 Edition.
- 5. CNF012, GE Report CHMB Customer Notification Form 5.0 ATTACHMENTS - CNF ISI007 GE Report: Indication 16 (3 Pages) - CNF012 GE Report: Indication 28 (2 Pages) 6.0 MILESTONES See Passport for Milestones.
7.0 Impact Review ISI program engineer performed an interface review and signed a Passport Milestone.
Per review of CCAA102, there were no additional impacts identified.
Revision 1: An ISI program engineer performed an interface review and signed a Passport Milestone.
There are no additional impacts from revision 1 of this technical evaluation.
Engineering Change Print Date: 12/08/2020 EC Number : 0000633079 000 Status/Date : MODIFIED 12/08/2020 Facility : PEA Type/Sub-type: EVAL STRU Page: 1 EC
Title:
ASSESS UNIT 2 MOISTURE BARRIER DAMAGE IMPACT ON DRYWELL VESSEL Mod Nbr : KW1: SR KW2: KW3: KW4: KW5:
Master EC : N Work Group : Temporary : N Outage : N Alert Group: A5452NESDM Aprd Reqd Date:
WO Required : Image Addr : Exp Insvc Date:
Adv Wk Appvd: N Alt Ref. : Expires On : 09/03/2023 Auto-Advance: Y Priority : Auto-Asbuild : N Caveat Outst: Y Department : Discipline :
Resp Engr : PAUL R KESTER Location :
Milestone Date PassPort Name Req By 110-PREPARE EC 11/23/2020 U000PRK KESTER PAUL APPROVED 120-REVIEW EC 12/03/2020 U000JV6 VACANTE JOSEPH APPROVED I have independently verified this Engineering Technical Evaluation and con cur with the conclusions herein. All comments have either been incorporate d or resolved between the originator and verifier. Additional engineering analysis regarding the corrosion mechanisms and environment are deemed appr opriate and are provided by reference within this document.
210-DEPT RVW-EP 11/23/2020 E114373 JORDAN BENJAMIN APPROVED I have reviewed the technical eval and concur with the specified conclusion. This evaluation meets the ASME Section XI requirements of IWE2500(d) and 10CFR50.55a(b)(2)(ix)(A)(1).
Ben Jordan (11/23/20) 300-APPROVE EC 12/08/2020 U000A5M HUBER AMY APPROVED
EC 633079 rev. 0 Page 1 of 3 Scope:
This evaluation applies to Peach Bottom Unit 2, addressing the condition discovered during P2R23. The condition being evaluated is that the moisture barrier, where the drywell bottomelevation concrete floor slab abuts the steel containment vessel, was found degraded. The moisture barrier is essentially a large bead of caulk that seals the interface where the concrete floor stops at the steel containment vessel wall as it rises above the Elevation 11911 floor elevation. Refer to dwg. S193 detail 1 (ref. 4).
This interface forms the circular perimeter of the Elevation 11911 floor slab. A 4long section of the perimeters sealant material was found to be unadhered and dislodged from the joint from azimuth 145 to azimuth 157. This would leave the joint, and the potential crevice between the concrete and steel below it, open to any water that leaked within the drywell (excluding the undervessel area). The water has no drainage path from there, so it could remain in the crevice and corrode the steel containment vessel. This area of the vessel, the internal steel surface beneath the concrete floor at Elevation 119 11, is classified as inaccessible.
The scope of this EC, as directed in AR 4379124 Assignment 02, is to evaluate the asfound condition and determine the acceptability of the inaccessible areas in accordance with 10CFR50.55a(b)(2)(ix)(A). That code states:
(A) Metal containment examinations: First provision. For Class MC applications, the following apply to inaccessible areas.
(1) The applicant or licensee must evaluate the acceptability of inaccessible areas when conditions exist in accessible areas that could indicate the presence of or could result in degradation to such inaccessible areas.
(2) For each inaccessible area identified for evaluation, the applicant or licensee must provide the following in the ISI Summary Report as required by IWA-6000:
(i) A description of the type and estimated extent of degradation, and the conditions that led to the degradation; (ii) An evaluation of each area, and the result of the evaluation; and (iii) A description of necessary corrective actions.
Evaluation:
The drywell is a steel containment vessel with varying thickness. The thickness for each section is designed to provide the needed capacity for all pressure, weight, thermal, seismic and other stresses.
This thickness must be monitored to ensure that sufficient capacity remains throughout its design life.
The bottom portion of the drywell is considered to be inaccessible because it is adjacent to concrete on both sides. Since the thickness and condition of the steel in this area can not be directly measured or
EC 633079 rev. 0 Page 2 of 3 visually monitored, this evaluation provides a qualitative assessment of the potential for material loss due to corrosion from exposure to water.
The moisture barrier addressed here is a sealant applied to the perimeter of the drywell concrete floor, at its interface with the steel drywell shell. That sealant is intended to prevent water or moisture from coming into contact with the drywell shell below the elevation of the floor surface. Corrosion in this area would be difficult to detect due to its inaccessibility. With the damage discovered to the sealant during 2R23 and the known leakage in the drywell, it must be assumed that water has infiltrated the interface of the concrete and the drywell shell to some degree. The potential for this to cause corrosion of the drywell shell is therefore assessed.
The chemistry of concrete is very basic (high pH), which protects the steel in contact with it from rusting, much like the rebar contained within concrete is protected from rusting. That chemical process, and its applicability to this specific configuration have been described in detail in the attachment to previous IR 2561844 A03 (ref. 3). It remains applicable to the current concern being addressed for the Unit 2 drywell in P2R23. In addition, oxygen must be present for the drywell steel to oxidize. The drywell is purged with nitrogen most of the time, limiting the presence of oxygen. The area of drywell steel that would have the highest exposure, and therefore vulnerability to moisture and oxygen would be at the location of the moisture barrier. This location is exposed to oxygen during a refueling outage, and is where water leakage in the drywell could collect (in the areas of a damaged moisture barrier). The inaccessible portion of the drywell below the floors surface could also be exposed to moisture, but it would not have as much exposure to oxygen, if any at all. This line of highest vulnerability is typically observed with submerged steel, having rust at the water line but not above or below it. There is no visual evidence of any significant corrosion in the areas where the moisture barrier has separated. The observed steel at the dislodged area of the moisture barrier had little to no surface corrosion present.
Since this is the most likely area for corrosion, it can be concluded that the area beneath the level of the floor is in as good of a condition as the exposed areas, or better.
Note that this condition has been evaluated in detail for other Units in the past. Those past evaluations are included in the references below. Those evaluations were reviewed and determined to be applicable for the subject condition evaluated here. The essential arguments from those evaluations are provided above, while some of the more detailed explanations have not been repeated here. See the references below for more details as needed.
To specifically address the required items (i), (ii) and (iii) from the code above:
(i) The type of degradation being evaluated is the potential internal surface corrosion of the drywell containment vessel below the surface of the 11911 concrete floor. Based on the information above and in the cited references, the estimated extent of degradation is, at worst, minor surface corrosion with no significant loss of thickness in all inaccessible areas. This is based on the minor areas of surface corrosion visible at the interface being the worst level of corrosion, due to the chemically protective properties of the concrete and the absence of an environment containing oxygen below the floors surface. The condition that lead to the potential for corrosion is the portion of damaged moisture barrier. The exact cause of the damaged moisture barrier is not known, but it is suspected to be due to high temperature fluid leakage (oil or water) causing a loss of adhesion.
EC 633079 rev. 0 Page 3 of 3 (ii) The information above, and the supporting details in the references indicate that there would be no significant corrosion on the inaccessible surface of the drywell containment vessel. It is concluded that there would be no loss of thickness, and therefore the containment remains fully qualified.
(iii) The moisture barrier was restored to its required configuration (ref. 5). No additional corrective actions are required.
==
Conclusion:==
The failed portion of moisture barrier and the resulting potential for water having seeped into the interface between the floor slab and the drywell shell do not present a threat of any significant corrosion occurring to the drywell shell. The deficiencies in the moisture barrier have been corrected to prevent further exposure. No additional action is required.
Administrative:
This is a technical evaluation prepared in accordance with CCAA309101 rev 15. It addresses a safety related structure and therefore requires an independent review, manager approval and transmittal to Records Management. Any required ISI program impacts are intended to be addressed by the program owner under AR 4379124 A03 and A04. A Milestone signoff has been requested of the ISI program owner to ensure that this response addresses the programs remaining needs. Based on a review of CC AA102, this evaluation has no other program, procedure or other documentation impacts and does not require interface review by any other group. Application of HUAA1212 with Julian Laverde indicated the highest applicable consequence risk factor has a Low severity level (L.2), and one human performance/process risk factor (P.6) is applicable to the scope of this evaluation. The uncertainty of critical parameters is mitigated through investigation of past, similar evaluations and the technical details supporting them. The resulting risk rank is 1, and existing process reviews are appropriate. This evaluation is not complex, and no supplemental reviews are required or warranted.
References:
- 1. Passport EC 621863 rev. 0, Unit 3 moisture barrier damage discovered during P3R21
- 2. Passport AR 4066968, Unit 3 moisture barrier damage discovered during P3R21
- 3. Passport AR 2561844, Unit 3 moisture barrier damage discovered during P3R20
- 4. Drawing S193 rev. 4, Reactor Vessel Foundation
- 5. WO 04997289 02, Repair of Moisture Barrier during P2R23 Attachments:
None