RS-20-100, Response to Request for Additional Information Regarding Application for Revision to TS 5.5.9, Steam Generator (SG) Program, for a One-Time Deferral of Steam Generator Tube Inspections

Response to Request for Additional Information Regarding Application for Revision to TS 5.5.9, Steam Generator (SG) Program, for a One-Time Deferral of Steam Generator Tube Inspections

ML20232D036
Person / Time
Site:	Byron
Issue date:	08/19/2020
From:	Kusumawati Murray P Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-20-100
Download: ML20232D036 (7)

Text

4300 Winfield Road Warrenville, IL 60555 Exelon Generation 630 65 7 2000 Office RS-20-100 10 CFR 50.90 August19,2020 U.S. Nuclear Regulatory Commission ATTN : Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455

Subject:

Response to Request for Additional Information Regarding Application for Revision to TS 5.5.9, "Steam Generator (SG) Program ,"

for a One-Time Deferral of Steam Generator Tube Inspections

References:

1) Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Application for Revision to TS 5.5.9, 'Steam Generator (SG) Program ,' for a One-Time Deferral of Steam Generator Tube Inspections," dated July 10, 2020 (ADAMS Package Accession No .

ML20196L732))

2) Email from J. Wiebe (U.S. Nuclear Regulatory Commission) to L.A. Simpson (Exelon Generation Company, LLC), "Preliminary RAls for Byron , Unit 2, Amendment to Defer SIG Inspections," dated August 10, 2020 By application dated July 10, 2020 (Reference 1), Exelon Generation Company, LLC (EGC) requested an amendment to the Technical Specifications (TS) for Renewed Facility License Nos. NPF-37 and NPF-66 for Byron Station, Units 1 and 2 (Byron) . The proposed changes would allow a one-time deferral of the steam generator tube inspections required in Section 5.5 .9.d.3, "Steam Generator (SG) Program," of the TS for Byron, Units 1 and 2. Although the proposed change only affects Byron Unit 2, Reference 1 and this submittal are docketed for Byron Station , Units 1 and 2, since the TS are common to Units 1 and 2 for Byron.

The proposed changes were submitted in response to social distancing recommendations by the United States Centers for Disease Control and Prevention, which have been issued as a defensive measure against the spread of the Coronavirus Disease 2019 (COVID-19).

In NRC email dated August 10, 2020 (Reference 2), the NRC determined that additional information is needed to complete its review. The Attachment to this letter provides the requested information.

August19,2020 U.S. Nuclear Regulatory Commission Page 2 EGC has reviewed the information supporting the No Significant Hazards Consideration and the Environmental Consideration that was previously provided to the NRC in Attachment 1 of the Reference 1 letter. The additional information provided in this submittal does not affect the conclusion that the proposed license amendment does not involve a significant hazards consideration. This additional information also does not affect the conclusion that there is no need for an environmental assessment to be prepared in support of the proposed amendment.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b),

EGC is providing a copy of this letter and its attachment to the State of Illinois.

This letter contains no regulatory commitments. Should you have any questions concerning this submittal, please contact Ms. Lisa Simpson at (630) 657-2815.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 19th day of August 2020 .

Respectfully, Kusuma wat i Digita lly signed by Kusumaw atim urray, Putri murray, Putn.

DN: cn = Kusumawatimurray, Putri Date: 2020.08. 19 11:49:41

• 05'00' Putri D. Kusumawati Murray Sr. Manager - Licensing Exelon Generation Company, LLC

Attachment:

Response to Request for Additional Information cc: NRC Regional Administrator, Region Ill NRC Senior Resident Inspector - Byron Station Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT Response to Request for Additional Information By application dated July 10, 2020 (Reference 1), Exelon Generation Company, LLC (EGC) requested an amendment to the Technical Specifications (TS) for Renewed Facility License Nos. NPF-37 and NPF-66 for Byron Station, Units 1 and 2 (Byron) . This proposed amendment request would modify Technical Specifications (TS) 5.5 .9, "Steam Generator (SG) Program ," for a one-time revision to the frequency for SG tube inspections. The requested TS amendments support deferral of the TS required inspections until the next Unit 2 refueling outage.

By email dated August 10, 2020 (Reference 2), the NRC determined that additional information is needed to complete its review. This attachment provides the requested information .

References :

1) Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Application for Revision to TS 5.5.9, 'Steam Generator (SG) Program,'

for a One-Time Deferral of Steam Generator Tube Inspections," dated July 10, 2020

2) Email from J. Wiebe (U .S. Nuclear Regulatory Commission) to L.A. Simpson (Exelon Generation Company, LLC), "Preliminary RAls for Byron, Unit 2, Amendment to Defer SIG Inspections," dated August 10, 2020

3) EC 632009, Revision 0, "Foreign Object Operational Assessment to Support B2R22 Deferral LAR," dated July 2020 NRC RAI 1 Table 4, "Byron B2R20 Foreign Objects Remaining in SGs Based on Visual Inspection ," in , "Description and Assessment," of the application , provides details for six foreign objects (FOs) that were found during visual inspections during Byron Unit 2 Refueling Outage 20 (B2R20). While reviewing the Byron Unit 2 SG tube inspection report for B2R20 dated April 5, 2018 (ADAMS Accession No. ML18095A116), the NRC staff noted on page 9 that the tube in Row 35, Column 22 (R35C22) in SG 2A and the tube in R40C52 in SG 2D "were preventatively plugged due to the FO that caused the wear is still present that may cause continued tube wear." The SG tube inspection report also stated that the foreign object wear in these tubes were newly reported in B2R20. Based on the statements in the SG tube inspection report for B2R20 , identify whether the presence of the FOs impacting these tubes were visually confirmed. If they were visually confirmed, provide justification for not including these FOs in Table 4 of Attachment 1 in the application. Provide justification that the FO analysis in the application is still valid if it only accounts for six of the eight FOs remaining in the SGs from B2R20.

EGC Response to NRC RAI 1 The two tubes preventatively plugged during B2R20 for foreign object wear (i.e., R35C22 in SG 2A and R40C52 in SG 2D) both had an assumed FO present at the wear location, which was just below the fifth tube support plate (i .e., tube support plate (TSP) Location 05H).

These two tubes are located several tubes into the bundles, which negatively impacted their accessibility. The Possible Loose Parts (PLPs) detected by eddy current in these tubes were not accessible for visual inspection during B2R20; therefore , they were not included in Table 4, "Byron B2R20 Foreign Objects Remaining in SGs Based on Visual Examination ," in Page 1 of 5

ATTACHMENT Response to Request for Additional Information of Reference 1. Support 05H is the third support structure above the secondary side handhole on the Hot Leg top of tubesheet. The nearest secondary side access handholes in the Byron Unit 2 SGs are located at the pre-heater section (Cold Leg) and at the top of tubesheet on the Hot Leg side. It is general industry practice not to pursue visual confirmation or removal of PLPs at the upper tube supports unless significant damage has occurred due to a FO . In these cases, to achieve access, it may be necessary to cut a hole into the SG vessel wall and inner wrapper.

Based on +Point' 1 eddy current, it was determined that both FOs were located just below 05H TSP and are positioned within the quatrefoil flow holes of the two tubes that were plugged in B2R20; therefore, they do not pose any risk to the surrounding tubes. To verify this, all tubes surrounding the tubes with the FOs (24 tubes for each FO) were inspected during B2R20 with the +Point' probe and confirmed there was no contact of the FOs with any adjacent tubes. The circumferential extent of the wear flaw within a quatrefoil lobe is limited to less than 90 degrees; therefore, there is no risk of the tube severing and affecting the surrounding tubes. Based on these as-left conditions, the FO analysis summarized in Reference 1 is still valid, as FO wear to inservice tubes from these two remaining TSP FOs is not expected. In addition, the revised 3-cycle Operational Assessment for FO wear (Reference 3) considers the possibility that new FO wear indications at TSPs similar to those detected in B2R20 could occur (either via new FOs entering the SGs or existing FOs potentially "relocating" from their current plugged tube locations). These hypothetical new FO wear indications at TSPs, even if actively growing at a conservative growth rate (i.e., 17.5%TW/cycle) for three operating cycles, were evaluated to not exceed the Condition Monitoring limit.

NRC RAI 2 On page 21 of Attachment 1 of the application, you state that there are 12 tube support plate (TSP) wear indications and five drilled support plate (DSP) wear indications in the Byron Unit 2 SGs. In Note 2 of Table 7, "Summary of Input Parameters and OA [Operational Assessment]

Results for Mechanical Wear at Structures," on page 22 of Attachment 1, you state that there are 13 TSP paired indications and 10 DSP paired indications for B2R18 and B2R20 combined. Provide clarification of the type of TSP and DSP wear indications reported on page 21 (i.e., single or paired wear indications) and confirm the reported numbers.

EGC Response to NRC RAI 2 Page 21 of Attachment 1 of Reference 1 states that there are 12 TSP wear indications and five DSP wear indications in the Byron Unit 2 SGs. These counts are correct for projecting growth of the TSP and DSP wear indications returned to service after B2R20. Note that one tube with two TSP wear indications was removed from service by plugging in B2R20.

In Note 2 of Table 7, "Summary of Input Parameters and OA [Operational Assessment] Results for Mechanical Wear at Structures," on page 22 of Attachment 1 of Reference 1, it states that there are 13 TSP paired indications and 10 DSP paired indications for B2R18 and B2R20 combined. Subtracting single (new and unpaired) indications found in B2R18 and B2R20, EGC 1

+Point is a trademark or registered trademark of Zetec, Inc. , its subsidiaries and/or affiliates in the United States of America and may be registered in other countries through the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

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ATTACHMENT Response to Request for Additional Information confirms there are 13 TSP paired indications for B2R18 and B2R20 combined, as reported in Note 2 of Table 7 on page 22 of Attachment 1 of Reference 1. The 1O DSP paired indications for B2R18 and B2R20 combined that were reported in Note 2 of the same table was overstated due to the inadvertent counting of two legacy FO wears near a DSP. The correct count of DSP paired indications for B2R18 and B2R20 combined is 8.

The table below provides a clarification of the type (i.e., TSP and DSP) and count of paired wear indications from the B2R18 and B2R20 refueling outages combined reported in Note 2 of Table 7 on page 22 of Attachment 1 of Reference 1.

B2R20 B2R18 B2R18 + B2R20 Description

___ (~~~-?_99_~~!.!.~)____ ___ (~~g;_gs_!~~-!.?L . .J~9.!~_?_, T_~_t?J~.?.L TSP DSP TSP DSP TSP DSP Wear Wear Wear Wear Wear Wear Total# of Support Wear Indications 74 14 1 5 4 NR NR Reported

1. of Repeat Indications "Paired" to a Wear Indication from Prior 84 4 5 4 13 83

_______________________l_~-~-P.~~!~~~---------------------- --------------- --------------- --------------- --------------- --------------- ---------------

1. of "Single" (New and Unpaired) 52 1 2 0 NR NR Indications Notes:

(1) Fourteen is the number of TSP wear indications reported in B2R20. However, Page 21 of Attachment 1 of Reference 1 states, "There are 12 TSP wear indications in the Byron Unit 2 SGs." This count is based on the number of remaining indications returned to service after B2R20 as one tube, SG 2C R49C65, with two TSP wear indications, was plugged during B2R20.

(2) Includes two "unpaired" indications that were identified at locations where prior TSP wear was reported in B2R18. This is due to the sizing technique from B2R18 to B2R20 being changed from bobbin to +Point'. Two tubes that each had a single TSP wear indication reported in B2R18 subsequently had wear detected at two separate quatrefoil lands at the same support locations in B2R20 (SG 2B R46C50 and SG 2C R49C65).

(3) Previously reported as 10 DSP paired indications in Note 2 to Table 7 of Attachment 1 of Reference 1. The updated count of paired DSP wear indications in Note 2 from 10 to eight does not affect the bounding degradation growth rates observed for DSP wear reported in Table 7 of Attachment 1 of Reference 1 and used in the 3-cycle Operational Assessment.

(4) There was one additional repeat TSP wear indication identified in B2R20 (14% TW), which was also detected in B2R18 (13%TW) but was not reported in ML15051A312 (i.e ., tube SG 2B R49C73) . There is no impact on the B2R20 or B2R18 operational assessments as a result of this omission of one TSP wear indication in B2R18. EGC has documented this issue in the corrective action program.

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ATTACHMENT Response to Request for Additional Information NRC RAI 3 There appears to be a several typographical errors in Attachment 1 of the application which are identified below.

EGC Response to NRC RAI 3 The following responses are provided as correction to the typographical errors identified in Reference 1.

NRC RAI 3.a

a. Section 3.2.3.d, "Operational Assessment Summary for All Degradation Mechanisms, Including Predicted Margin to the Tube Integrity Performance Criteria at B2R23 (October 2021 ),"consistently states that B2R23 is in October 2021, however, it is the NRC staffs understanding that B2R23 is in April 2022. Provide confirmation that B2R23 is in April 2022. In addition, provide clarification whether the approximately 52 effective full power months, also referenced in this section, is based on October 2021 or April 2022 .

EGC Response to NRC RAI 3.a Byron refueling outage B2R23 is scheduled in April 2022 , which is approximately 18 months following the fall 2020 refueling outage (B2R22). All instances where "October 2021" is stated in the EGC application dated July 10, 2020 (Reference 1) are typographical errors; these should instead state "April 2022," which is the month and year in which B2R23 is scheduled to begin.

In addition , the approximately 52 effective full power months referenced in Section 3.2.3 .d of of Reference 1 is based on April 2022 (B2R23). The corrected statement is as follows:

In summary, using the deterministic method, which is considered to be the most conservative OA approach, tubes with any of the three existing structural support mechanical wear mechanisms can safely operate for three cycles (approximately 52 EFPM) until April 2022 without challenging the tube integrity limits for each type of wear.

NRC RAI 3.b

b. On page 18, you state that the structural integrity performance criteria will be satisfied at B2R23 for existing and potential degradation and that the "accident-induced leakage performance criteria (AILPC) for the limiting accident condition will be met for the end of Cycle 22 condition." The NRC staff believes that you intended to state that the AILPC for the limiting accident condition will be met for the end of Cycle 23 condition . Please confirm that the AILPC will be met for the end of Cycle 23 condition.

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ATTACHMENT Response to Request for Additional Information EGC Response to NRC RAI 3.b EGG confirms that the AILPC for the limiting accident condition will be met for the end of Cycle 23 condition. Including "end of Cycle 22" in this statement of Reference 1 was a typographical error. The corrected statement is as follows:

Accident-induced leakage performance criteria (AILPC) for the limiting accident condition will be met for the end of Cycle 23 condition .

NRC RAI 3.c

c. Note 3 to Table 6, "Summary of Operational Assessment (Exam Scope, Results, and Margins) for Potential SCC [Stress Corrosion Cracking] Degradation Mechanisms for 3 Cycle Operation to B2R23 (October 2021 ),"on page 20, states that "no primary-to-secondary leakage was reported during Cycle 21 and is not expected for Cycle 22."

Confirm whether or not that you intended to state that there was no primary-to-secondary leakage reported during Cycles 21 and 22 and is not expected for Cycle 23 .

EGC Response to NRC RAI 3.c Table 6, "Summary of Operational Assessment (Exam Scope, Results, and Margins) for Potential SCC Degradation Mechanisms for 3 Cycle Operation to B2R23," contains typographical errors. The title of Table 6 should reference "April 2022" instead of "October 2021 ." In addition, Note 3 to Table 6 contains a typographical error regarding Cycle 22 . The corrected Note 3 is as follows:

(3) No primary-to-secondary leakage was reported during Cycle 21. to date for Cycle 22.

and is not expected for Cycle 23.

NRC RAI 3.d

d. On page 24, you state "should a loose part be present in the hot leg or cold leg primary bowl during operating Cycle 22, Byron Unit 2 will take appropriate action to minimize any damage to the Steam Generators." Confirm whether or not that you intended to state should a loose part be present in the hot leg or cold leg primary bowl during operating Cycle 23 .

EGC Response to NRC RAI 3.d The use of "Cycle 22" in the discussion regarding the Loose Parts Detection System of the Steam Generations contained a typographical error; it should have stated "Cycle 23." The corrected statement is as follows:

Should a loose part be present in the hot leg or cold leg primary bowl during the remainder of Cycle 22 or operating Cycle 23, Byron Unit 2 will take appropriate action to minimize any damage to the Steam Generators.

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