Advisory Committee on Reactor Safeguards Full Committee Davis-Besse Nuclear Power Station Final & Supplemental Safety Evaluation Report November 4, 2015 Rick Plasse, Project Manager Office of Nuclear Reactor Regulation

2 LRA Submitted by letter dated August 27, 2010 Pressurized Water Reactor (PWR), Babcock & Wilcox nuclear steam supply system Operating license for NPF-3 expires April 22, 2017 Located approximately 20 miles east of Toledo, OH Overview

3 Safety Evaluation Report (SER) with Open Items was issued July 2012 ACRS License Renewal Subcommittee Meeting held September 19, 2012 Final SER was issued September 2013 Supplement to SER was issued August 2015 ACRS 2 nd License Renewal Subcommittee Meeting held September 23, 2015 Safety Review Results

OI B Operating Experience Issue: During review, LR-ISG , “Ongoing Review of Operating Experience,” was issued Basis for closure: Applicant provided additional information that addressed the guidance in LR-ISG Applicant will enhance AMPs or develop new AMPs when necessary to ensure effects of aging are adequately managed 4 Open Item B.1.4-1: Closed

OI Reactor Vessel Neutron Embrittlement (SER Section 4.2.2): Issue: Reactor vessel welds with unknown initial upper shelf energies (USE) require an equivalent margins analysis (EMA), per §Part 50, App G, requirements Basis for closure: EMA submitted and approved to demonstrate that the welds will have adequate margins of safety on USE, as required by §Part 50, App. G EMA provides an acceptable basis to accept the USE TLAA under §54.21(c)(1)(ii). 5 Open Item 4.2-1: Closed

OI Pressure-Temperature (P-T) Limits: Issue: Methodology (Report BAW A, Rev. 2) invoked by Tech. Spec for calculating P-T limits may not assess potentially limiting reactor vessel non- beltline locations Basis for closure: Applicant demonstrated Report BAW-10046, Rev. 2, appropriately accounts for potentially limiting reactor vessel non-beltline locations near geometric discontinuities. TS basis remains valid to accept under §54.21(c)(1)(iii). 6 Open Item : Closed

Safety Review Results Final SER issued September 2013 (all open items were closed): 44 AMPs total 7 Staff Disposition of Program Existing AMPs New AMPs Consistent with the GALL Report95 Consistent with enhancements112 Consistent with exceptions2- Consistent with both enhancements and exceptions 5- Plant specific46 Subtotals:3113

SER Supplement 1 Supplement 1 to SER issued August 10, 2015 –Reactor Vessel Internals Inspection Plan and Program –Annual Updates in 2013, 2014, and 2015 –Updated information and commitments in response to recent industry operating experience –New plant specific program Service Level III Coating and Linings Monitoring Program –Steam Generator Replacement (Spring 2014) –Shield Building Laminar Cracking Propagation Conclusion is unchanged List of Commitments in Appendix A –Several commitments completed and reviewed by NRC staff 8

9 Shield Building Monitoring Program to manage aging effects on laminar cracks; preventive protective coating applied. Plant-specific prevention & condition monitoring AMP, supplements Structures Monitoring Program Scope includes SB Wall Concrete & Reinforcing Steel; SB exterior concrete coatings Periodic visual inspections of representative sample of core holes; Visual inspections will be supplemented with NDE (i.e., Impulse Response (IR) Mapping) Opportunistic visual inspections of rebar near laminar cracking Periodic visual inspections of exterior coating every 5 years & coating reapplied every 15 years Personnel qualifications per ACI Report 349.3R Ch. 7 Shield Building Monitoring Program (OI )

10 Operating experience of crack propagation: AMP considers and incorporates future operating experience, as necessary Accordingly, the applicant revised AMP to incorporate plant-specific OpE of laminar crack propagation discovered in 2013 & 2015, attributed to “ice-wedging” phenomenon Revised AMP increased inspection sample size of core holes, increased inspection frequency, and conducts IR to confirm extent of crack propagation Shield Building Monitoring Program (contd…)

11 Adequacy of sample size and distribution: Representative sample for inspection consists of a minimum of 28 core hole locations, with provisions for consideration of past evidence of propagation and expanding inspection sample. 14 are cracked covering the spectrum of locations with highest prevalence of cracking and a range of observed crack widths; includes the 3 maximum observed crack widths, to monitor crack width & planar limit of propagation. 14 are uncracked but generally located near areas of known cracking providing ability to monitor propagation including 5 leading edge bores to monitor limits of recent planar propagation. Shield Building Monitoring Program (contd…)

12 Acceptance Criteria for Core Bore Inspection Findings: Need for corrective action evaluated in Corrective Action Program using evaluation hierarchy in Figure 5.1 of ACI 349.3R, if any of below criteria not met. Qualitative: Cracking remains passive –No discernible change in existing cracks (width, planar size) –No Indication of new cracking in bores or from IR mapping Quantitative: Bounded by qualitative criteria; and bounded by SB calculations-of-record –Crack width does not exceed inch (current observed maximum width) –Extent of circumferential planar crack limit does not exceed that in SER Table Shield Building Monitoring Program (contd…)

13 ACI 349.3R Evaluation Heirarchy

14  In summary, the staff finds the SBMP AMP acceptable because: Laminar cracks are inspected at a 1 year interval and this interval will not be progressively incremented to 2/4 years unless cracks become passive A representative sample of no less than 28 core bores will be inspected at every inspection to effectively monitor crack width and planar limit The use of visual inspections and Impulse response testing can effectively detect changes in laminar cracking Inspection findings will be evaluated by qualified personnel using the evaluation procedure in ACI Report 349.3R The acceptance criteria of crack being “not passive” would trigger further evaluation under the corrective action program if inspection findings indicate discernable change in the cracks Shield Building Monitoring Program – Conclusion

15  Based on the AMP attributes discussed in the previous slides, staff concludes that through implementation of the AMP, the applicant will be able to adequately monitor the cracks, perform structural evaluations, and take timely corrective actions, if necessary, prior to loss of function  Staff thus concludes that there is reasonable assurance that aging effects on the shield building laminar cracking will be adequately managed by the Shield Building Monitoring Program, such that intended functions will be maintained during the period of extended operation.  OI is closed and staff evaluation is documented in SER/SSER Section Shield Building Monitoring Program – Conclusion (contd..)

16 Conclusion On the basis of its review, the staff determines that the requirements of 10 CFR 54.29(a) have been met for the license renewal of Davis-Besse Nuclear Power Station