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| {{#Wiki_filter:Exelon Generation-~ Dresden Nuclear Power Station 6500 North Dresden Road Moms, IL 60450 February 3, 2021 SVPLTR #21-0003 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 3 Facility Operating License No. DPR-25 NRC Docket No. 50-249 | | {{#Wiki_filter:}} |
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| ==Subject:==
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| Owner's Activity Report Submittal Fifth 10-Year Interval 2020 Refueling Outage Activities This letter submits the Owner's Activity Report (i.e., Form OAR-1) for the Dresden Nuclear Power Station (DNPS) Unit 3 refueling outage (D3R26) that began on October 26, 2020 and was completed on November 7, 2020. This is the first refueling outage conducted in the Third (3 rd ) Inspection Period of the Fifth (5 th ) 10-Year Interval lnservice Inspection (ISi) Program for DNPS Unit 3. A copy of the Owner's Activity Report is provided and attached to this letter.
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| This Owner's Activity Report is submitted in accordance with American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Case N-532-5, "Repair/Replacement Activity Documentation Requirements and lnservice Summary Report Preparation and Submission*. Code Case N-532-5 requires an Owner's Activity Report Form OAR-1 to be prepared and certified upon completion of each refueling outage. In accordance with the conditions of Code Case N-532-5, this OAR-1 form.is being submitted within ninety (90) days of the completion of the refueling outage. The 10 CFR 50.55a(b)(2)(ix)(A)(2) evaluation of inaccessible areas is included in Attachment 2.
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| Should you have any questions concerning this letter, please contact Mr. Ryan Sprengel, Regulatory Assurance Manager at (815) 416-2800.
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| Respectfully, Peter J. Karaba Site Vice President Dresden Nuclear Power Station Page 1 of8
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| Attachment 1 Owner's Activity Report, Form OAR-1 FORM OAR-1 OWNER'S ACTIVITY REPORT Report Number Refueling Outage D3R26 OAR-1 Plant Dresden Nuclear Power Station, 6500 North Dresden Road Manis, IL 60450 Unrt No. 3 Commeraal Service Date _ _ _ _1_1.L../1_6'-L./_19'-'7_1'---___ Refueling Outage Number _ _ _ D3_R2_6_ _
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| (If applicable)
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| CUTTe11t Inspection Interval 5th Inspedmn Interval (ISI), 3rd Inspection Interval (Containment)
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| (1 11, 200, Jnl, 4111, other)
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| Current Inspection Pencxl 3rd InspectJOn Period (!SI), 1st Inspection Period (Containment) c1 *, 200, Jn1 )
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| 2007 Edition and 2008 Addenda (ISI),
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| Edrtlon and Acklenda of Secbon XI appllcable to the Insped:Jon Plans 2013 Edition (Containment)
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| Date and RevJSlon of Inspecbon Plans 08/25/2020 (ER-DR-330-1001 Rev. 0)
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| Edlbon and Addenda of Secbon XI applicable to repair/replacement acbvlbes, lf different than the inspection plans NA Code cases used: N-62-7, N-508-4, N-526, N-532-5, N-552-1, N-578-1, N-600, N-613-2, N-702, N-747, N-765, N-778, N-805, N-825, N-845 (If ap pf lea bf e, mcl ud1 rig cases modJf!ed by case N-532 and later revisions)
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| CERTIFICATE OF CONFORMANCE I certify that (a) the statements made m this report are correct; (b) the exam1nabons and tests, meet the Inspecbon Plan as required by the ASME Code, SectJon XI; and (c) the repair/replacement acbvltles and evaluations supporting the completion of D3R26 conform to the requirements of Section XI (refuelmg outage number)
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| Signed Matenal Programs Engineer/ Date o I {a.,(? /a,o ~I OWner or OWner's deslgriee. Tltl CERTIFICATE OF INSERVICE INSPECTION I, the undersigned, holding a valid commission 1SS1.Jed by the Nabonal Board of Bojler and Pressure Vessel Inspectors and and employed by The Hartford Steam Boller Inspection and Insurance Company of Hartford, Connecbcut have Inspected the rtems desaibed In this OWner's ActMty Report, and state that, to the best of my knowledge and belief, the ONner has perfonned all activibes represented by this report m accordance wrth the requirements of Secbon XI.
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| By signing thlS cert:Ificate neither the Inspector nor his employer makes any warranty, expressed or Implied, concenmng the repair/
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| replacement acbVTtles and evaluabon descnbed in thlS 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 arlsmg from or connected with this lnspecbon.
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| ___:.Jir-:::::_..:::~*-~-=~::::===:::::...______ Commissions NB10972 R N I Inspector's Signature (Nabonal Board Number and Endorsements)
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| Date Page 3 of8
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| Attachment 1 Owner's Activity Report, Form OAR-1 TABLE 1 ITEMS WITH FLAWS OR RELEVANT CONDmONS THAT REQUIRED EVALUATION FOR CONTINUED SERVICE Examination category and Item Description Evaluation Description Item Number None None None Page 4 of8
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| Attachment 1 Owner's Activity Report, Form OAR-1 TABLE 2 ABSTRACT OF REPAIR/REPLACEMENT ACTIVITIES REQUIRED FOR CONTINUED SERVICE Code Item Description Date Repair/
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| Class Description Of Work Completed Replacement Plan Number Welded new flanges to pipe and installed pipe.
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| 3 Repair CREVS Pipe Flanges 9/25/2019 3-19-007 (IR 04176499)
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| Install new slip on pipe flanges involving welding U3 EDGCWP Inlet flange on check valve 3-3930-3 due to wear. Includes repair of pitted areas if 4/22/2020 3-20-054 501 found. (IR 04336861)
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| Page 5 of8
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| ATTACHMENT 2 CONTAINMENT ISi (IWE) RESULTS Page 6 of 8
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| As required by 10 CFR 50.55a(b)(2)(ix)(A), "Metal containment examinations: First provision,"
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| for Class MC applications, 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. For each inaccessible area identified for evaluation, the applicant or licensee must provide the following in the ISI Summary Report required by 1WA-6000:
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| (i) Description of the type and estimated extent of degradation, and the conditions that led to the degradation:
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| During the Unit 3 refueling outage (D3R26) visual examinations of the drywell basement moisture barrier were performed due to an extent of condition from the Unit 2 outage in 2019.
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| The Unit 2 inspection found more than 50% of Unit 2 Drywell moisture barrier to be degraded (Ref. 1). Therefore, it was recommended by the Responsible Individual to inspect the Unit 3 drywell basement moisture barrier (Ref. 2). The Unit 3 inspection in D3R26 found three locations with recordable indications to be relevant indications (Ref. 3). The cause of this condition is not directly tied to one event, but rather due to the work activities performed in the drywell basement since the application of the moisture barrier which could have introduced damage to the moisture barrier surface (e.g. moving equipment, building scaffold, etc.).
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| Inaccessible areas of the liner plate were made accessible by removing these portions of the moisture barrier. A supplemental VT-1 exam of liner behind moisture barrier was completed and found no recordable indications (Ref. 4). Due to finding no recordable indications on the underlying liner plate at the locations with the degraded moisture barrier the liner plate is acceptable for continued service by examination in accordance with IWE-3122.1 (Ref. 1). A technical evaluation of the inaccessible locations of the containment liner is further discussed in Engineering Change Evaluation (EC Eval 633181 - Ref. 6).
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| (ii) An evaluation of each area, and the result of the evaluation:
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| Both Dresden Unit 2 & 3 share the same Boiling Water Reactor (BWR) Mark I containment design. There were no recordable indications on the underlying containment liner examined during D3R26, therefore the conclusions from the Unit 2 evaluation (EC 629967 Ref. 7) have been conservatively used to accept Unit 3's conditions and conclude no degradation is occurring in the inaccessible areas. Furthermore, UT thickness measurements are performed on Unit 3 drywell steel liner sand pocket area, as part of Generic Letter 87-05 and in accordance with License Renewal program B 1.26, core bore holes are ultrasonically examined every outage to trend liner degradation. The thickness corrosion rate has been conservatively estimated based on the given data to be no greater than 7.2 mil/year, and this is less than the conservatively worst-case corrosion rate of 10 mil/year for fresh river water (Ref. 8). Based on this conservatively assumed corrosion rate, it was concluded that the effects of corrosion on liner stresses would remain below the ASME Code allowable stress limits until January of 2030.
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| Additionally, the concrete is very basic (high pH), which protects the steel in contact with it from rusting. 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. The inaccessible portion of the drywell below the floor's surface could also be exposed to moisture, but it would not have as much exposure to oxygen, if at all. This line of highest vulnerability is Page 7 of8
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| typically observed with submerged steel, having rust at the water line but not above or below it.
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| The VT-I examination of the U3 containment liner (Ref. 4) indicated no evidence of corrosion in the areas where the moisture barrier has separated. 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.
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| (iii) A description of necessary corrective actions:
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| Removal and replacement of degraded locations of the drywell basement moisture barrier was performed during D3R26 (Ref. 9). The moisture barrier will be inspected (VT-1) during the next inspections period (D3R27) in accordance with IWE-2420 (b) (Ref. 5). Since, the VT-I of the underlying containment liner had no recordables, the underlying containment is acceptable without additional repair or replacement activities per IWE-3122.1 (Ref. 5).
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| REFERENCES
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| : 1. Issue Report No. 04294208 - D2R26 Drywell Basement Moisture Barrier Relevant Conditions
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| : 2. Issue Report No. 04296902 - D3R26 Contingency WO for DW Moisture Barrier Replacement
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| : 3. Issue Report No. 04379976-D3R2 6 Drywell Basement Moisture Barrier Relevant Conditions
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| : 4. NDE Report 20-435 - (K) NDE Perform VT-1 Of Containment Liner WO 04999923
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| : 5. American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC), Section XI, 2013 Edition
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| : 6. EC 633181 Rev. 000 - D3R26 Engineering Evaluation for Moisture Barrier And Drywell Liner
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| : 7. EC Evaluation 629967 - D2R26 Engineering Evaluation For Moisture Barrier And Drywell Liner Degradation
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| : 8. EC 373104 Rev. 003 - Evaluation ofU3 Drywell Steel Liner NDE Data
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| : 9. Work Order No. 04999923 - Request D3R26 Contingency WO for DW Moisture Barrier Replacement Page 8 of8}}
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