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Kyle J. AmbergePrincipal Technical Leader

NRC-Industry Materials Technical Exchange MeetingRockville, MD 5/21/2019

PWR Core Barrel Cracking Operating Experience in USMRP-227-A Inspection Findings Summary

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2018 OE associated with PWR Core Barrel Cracking In spring 2018 refueling outage, a domestic CE plant identified cracks on OD

surface of the core barrel in the belt-line elevation using EVT-1 method– These inspections were previously planned in accordance with MRP-227-A– Utility informed industry and NRC during outage

Based on first-of-a-kind EVT-1 inspection finding, utility performed additional EVT-1 and UT inspections to further characterize the indications (owner-elected extent of condition exams)– One crack-like indication found in base-metal adjacent to the middle-girth weld

(Primary component in MRP-227-A)– 45 crack-like indications found in base-metal adjacent to the middle-axial weld

(Expansion component in MRP-227-A)– None of these indications are through-wall

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2018 OE associated with PWR Core Barrel Cracking Conservative engineering analysis was performed by the utility owner Analysis was in accordance with methods identified in WCAP-17096-NP-A

which is NRC-approved acceptance criteria/methodologies– Conditions are acceptable to operation for one 18-month cycle

(ML19044A636)– Utility-specific actions and additional inspections are planned for fall

2019 Industry established joint EPRI/PWR Owners Group Focus Group

– Intent is to provide generic assessment of impact of OE to industry

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Additional 2018-2019 Inspections for PWR Core Barrels Two additional utilities performed MRP-227-A inspections of PWR

core barrels in fall 2018 and spring 2019 These PWR units are CE-design units similar to the affected PWR

with core barrel cracking indications in spring 2018 outage Each utility performed EVT-1 visual inspections of 100% of all core

barrel girth welds and axial welds in the core belt-line region No indications of cracking were identified

Thus, so far, three (3) PWR utilities have inspected core barrels– One CE-design PWR unit identified the cracking in spring 2018

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MRP-227-A PWR Core Barrel inspections since 2011

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PWR Core Barrel Inspections in USA thru 2019Unit Year Upper Flange Weld UGW/MGW or LGW Lower Flange Weld Axial welds

1.W-2-loop PWR 2011 EVT-1 sat VT-3 (isi) VT-3 (isi) No exam*

2.W-3-loop PWR 2012+2013 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

3.W-3-loop PWR 2012+2014 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

4.W-2-loop PWR 2013 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

5.W-2-loop PWR 2015 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

6.W-3-loop PWR 2013 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

7.CE-design PWR 2014 EVT-1 sat EVT-1 sat No exam No exam*

8.W-3-loop PWR 2014 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

9.W-3-loop PWR 2014 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

10.W-2-loop PWR 2014 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

11.W-2-loop PWR 2015 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

12.W-4-loop PWR 2016 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

13.W-3-loop PWR 2016+2018 EVT-1 sat (2016) EVT-1 sat (2018) EVT-1 sat (2018) No exam*

14.W-3-loop PWR 2016 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

15.CE-design PWR 2017 EVT-1 sat EVT-1 sat No exam No exam*

16.W-4-loop PWR 2017 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

17.W-3-loop PWR 2018 EVT-1 sat EVT-1 sat EVT-1 sat No exam*

18.CE-design PWR 2018 EVT-1 sat EVT-1 sat No exam No exam*

19.CE-design PWR spring 2018 EVT-1 sat EVT-1 MGW indication No exam 45 indications MAW

20.CE-design PWR fall 2018 EVT-1 sat EVT-1 sat EVT-1 sat EVT-1 sat

21.CE-design PWR spring 2019 EVT-1 sat EVT-1 sat EVT-1 sat EVT-1 sat

22.CE-design PWR fall 2019 - Re-inspect planned - Re-inspect planned

*Previous inspections that did not include axial welds in scope

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List of upcoming planned MRP-227-A CB inspections Fall 2019- one (1) 4-loop WEC-design PWR Spring 2020- one (1) 2-loop WEC-design PWR Fall 2020- two (2) 4-loop WEC-design PWRs, 3-loop WEC-design PWR Spring 2021- one (1) 4-loop WEC-design PWRs, 3-loop WEC-design PWR Fall 2021- two (2) 4-loop WEC-design PWRs, 3-loop WEC-design PWR Spring 2022- one (1) 4-loop WEC-design PWR

Industry’s intent is to provide inspection guidance to these PWR plants based on potential risk of identifying similar core barrel “off-axis” cracking

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Near-Term PWR Core Barrel Inspection and Evaluations Industry prepared MRP-227-A interim guidance is nearing

completion:– Interim Guidance technical basis letter provided technical details behind

the inspection guidance being considered Currently CB interim guidance is under final review by utilities Focus of interim guidance is to address potential for “beyond

design-basis” conditions and need for long-term asset management Continued core barrel weld technical efforts in 2020 will transition

to on-going PWR Owners Group Materials Committee projects, and individual plant-specific actions based on inspection findings

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