ML20238C107

Response to Request for Additional Information (Redacted)

ML20238C107
Person / Time
Site:	Callaway
Issue date:	08/25/2020
From:	Ameren Missouri, Framatome, Union Electric Co
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20238C104	List: ML20238C107 ULNRC-06595, Response to Request for Additional Information Regarding License Amendment Request for Deferral of Upcoming Steam Generator Inspection (LDCN 20-0013))
References
LDCN20-0013, ULNRC-06595 ANP-3867Q1NP, Rev 1
Download: ML20238C107 (15)

Text

Attachment 2 to ULNRC-06595 Response to Request for Additional Information (Redacted)

framatGme RAI Response Regarding NP-386Q1NP Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-001 3)

Licensing Report August 2020 (c) 2020 Framatome Inc.

ANP-3867Q1 NP Revision I Copyright © 2020 Framatome Inc.

All Rights Reserved

Framatome Inc. ANP-3867Q1 NP Revision 1 RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Page i Nature of Changes Section(s)

Item or Page(s) Description and Justification I All Initial Issue 2 Section 4.0 Corrected a typo in Reference 6 from ccLiceYJ to License

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Page ii Contents Page

1.0 INTRODUCTION

1-1 2.0 RAI I 2-1 3.0 RAI 2 3-1

4.0 REFERENCES

4-1

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Page iii List of Figures Figure 2-1 AVB Wear Indications Weibull Fit 2-3 Figure 2-2 New AVE Wear Indications Depth Distributions 2-4

Framatome Inc. ANP-3867Q1NP Revision 1 RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Pane iv Nomenclature Acronym Definition AVB Anti-Vibration Bar ECT Eddy Current Testing EFPY Effective Full Power Years LAR License Amendment Request OA Operational Assessment PLP Potential Loose Part RAI Request for Additional Information SG Steam Generator TTS Top-of-Tubesheet

Framatome Inc. ANP-3867Q1NP Revision 1 RAI Response Regarding Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-00 13)

Page 1-1

1.0 INTRODUCTION

Framatome supported a one-time license amendment request (LAR) from Ameren Missouri for the deferral of fall 2020 steam generator (SG) tube inspections at the Callaway Plant (Unit 1) (Reference 1) by providing the technical justification in an operational assessment (OA) (References 2, 3, and 4).

On August 12, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff requested the following additional information in order to complete their review of the subject LAR.

Request for Additional Information (RAI)

I . Section 5. 1 .3 of Attachment 2 discusses the treatment of new wear indications at the tube anti-vibration bar (AVE) locations. The analysis conservatively predicts over 700 total new indications at I R25 that are introduced in two populations at different intervals after I R21.

a. Please discuss how the number of new indications are apportioned between the two populations and the basis for those numbers.

b. Please provide an updated Figure 5-2 that also includes the I RI 8 new indication depth distribution. Discuss why the new indication deferral distribution sampled in the analysis as shown in Figure 5-2 is expected to be representative or conservative.

2. Table 3-4, Section 4.2.1, and Section 5.4 ofthe operational assessment describe the inspections performed with bobbin and array probes to detect foreign objects. The array probes were used in certain areas of the hot leg periphery and no tube lane to supplement the 100 percent bobbin probe inspection. Please discuss the reasoning behind supplemental array probe inspection in the hot leg only, in terms of probability of foreign object wear in the hot leg or cold leg tubes.

Note that all section numbers, tables and figures referenced in the request for additional information (RAI) are from the proprietary version of the OA (Attachment 2 of Reference I). A non-proprietary version of the OA is included in Reference 2.

Framatome Inc. ANP-3867Q1NP Revision 1 RAI Response Regarding Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-0013)

Page 2-1 2.0 RAI I QUESTION:

Section 5.1.3 of Attachment 2 discusses the treatment of new wear indications at the tube anti-vthration bar (AVB) locations. The analysis conservatively predicts over 700 total new indications at I R25 that are introduced in two populations at different intervals after 1R21.

a. Please discuss how the number of new indications are apportioned between the two populations and the basis for those numbers.

b. Please provide an updated Figure 5-2 that also includes the I RI 8 new indication depth distribution. Discuss why the new indication deferral distribution sampled in the analysis as shown in Figure 5-2 is expected to be representative or conservative.

RESPONSE

The number of new AVB wear indications initiated in the probabilistic model is determined through use of a Weibull fit to the cumulative number indications identified in the Callaway steam generators (SGs), as shown in Figure 2-1 The Weibull fit utilized in the evaluation reflects a more aggressive initiation rate than is expected to occur going forward and would project a much larger number of new indications during IR2I than actually occurred. This can be observed by noting that the actual number of newly reported indications decreased in I R2I as compared with I RI 8, which is a behavior consistent with the experience of most plants experiencing structure wear.

Since the Kunin distribution of new wear depths (Figure 2-2) is based on a three-cycle operating interval (IRI8 to 1R21), it is appropriate to introduce new flaws to the simulation at 1R24 (i.e., three cycles after 1R2I). The second population of new flaws is introduced at 1R25, after only one additional cycle of operation. This is quite conservative since the same 3-cycle Kunin depth distribution is used for this purpose.

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-0013)

Page 2-2 Attenuation of AVB wear growth over time is an observed behavior; therefore, it is assumed that the depth distribution of new indications at I R21 will be similar if not bounding of an expected new indication depth distribution that would be identified after the following three-cycles (i.e., at 1R24). This attenuation can be observed in the Callaway new indication depth distributions from 1R15, 1R18 and 1R21, as shown in Figure 2-2. It should be noted that the SGs had only operated one cycle at 1R15, so the new indications at 1R15 were adjusted to a comparable 3-cycle length of 4.016 EFPY (i.e., the summation of Cycles 15, 16 and 17 from Reference 2).

Framatome Inc. ANP-3867Q1NP Revision 1 RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Page 2-3 Figure 2-1 AVB Wear Indications WeibuN Fit

[d,e]

Framatome Inc. ANP-3867Q1NP Revision I RAt Response Regarding Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-0013)

Page 2-4 Figure 2-2 New AVB Wear Indications Depth Distributions

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for CaHaway Unit 1 One-Time License Amendment Request (LDCN 20-00 13)

Page 3-1 3.0 RAI 2 QUESTION:

Table 3-4, Section 4.2.1, and Section 5.4 of the operational assessment describe the inspections performed with bobbin and array probes to detect foreign objects. The array probes were used in certain areas of the hot leg periphery and no tube lane to supplement the 100 percent bobbin probe inspection. Please discuss the reasoning behind supplemental array probe inspection in the hot leg only, in terms of probability of foreign object wear in the hot leg or cold leg tubes.

RESPONSE

No foreign object wear or foreign objects that could potentially impact tube integrity have been identified in the Callaway SGs to date, and the incorporation of loose part trapping features within the SG design provides a high level of assurance that tube integrity will not be impacted by foreign material going forward.

The array probe examination of the hot leg periphery tubes performed during 1R21 represents a 50% sample of the most important tubesheet region with respect to foreign object wear (i.e., 50% of hot leg plus cold leg locations). In the absence of any indication of foreign objects or wear during this examination, no expansion of the inspection scope into the cold leg was considered to be necessary. In addition, 100% of the top of tubesheet region (hot and cold leg) was examined with bobbin probes. While bobbin probe detection of foreign objects and wear very close to the TTS is not equal to that of the array probe, the bobbin probe inspection nonetheless provides additional assurance that significant foreign object wear was not present in the tubes.

The I R21 CMOA (Reference 5) summarizes these points:

I . Callaway has no history of foreign object wear or foreign objects. Neither ECT examinations nor secondary side visual inspections have identified foreign object wear or foreign objects through 9.369 EFPY of operation (through 1 R21).

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for Callaway Unit 1 One-Time License Amendment Request (LDCN 20-0013)

Page 3-2

2. During 1R18 and 1R21, visual inspections were performed along both the hot and cold leg periphery and inner bundle passes from the no-tube lane to the sludge pile region. These visual inspections can typically see 8 tubes deep into the bundle and as identified above, have identified no foreign objects.

3. During I RI 8 and I R21 visual inspections were performed in the upper steam drum of all four SGs. These inspections revealed no foreign objects on the loose part trapping screen, or any degradation of secondary side components that could result in foreign material entering the SG tube bundle.

4. Callaway water lanced all four SGs during I RI 8 and I R21 A review of the material found in the lancing strainers at 1R18 (Reference 7) and 1R21 identified only a small number of foreign objects such as tube scale, rubber, plastic, sludge rocks, string, and two small metallic pieces less than 0.5 in length, none of which pose a threat to tube integrity.

Framatome Inc. ANP-3867Q1NP Revision I RAI Response Regarding Framatome Operational Assessment for Callaway Unit I One-Time License Amendment Request (LDCN 20-0013)

Page 4-1

4.0 REFERENCES

I . NRC ADAMS Accession No. ML2OI 78A668, Callaway Plant Unit 1 Request for, One-Time License Amendment to Defer Upcoming Steam Generator Inspection (LDCN 20-0013).

2. NRC ADAMS Accession No. ML2O1 78A673 Attachment 3 Callaway Unit I, Steam Generator Operational Assessment to Support Deferral of Planned Inspections from 1 R24 to I R25, Revision I (Redacted). (Corresponds to Framatome Documents 5 1 -931 2589-000 (Proprietary) and 51 -931 2589-001 (Non-Proprietary).)

3. Framatome Letter Framatome-20-01407, from Josh Harrison to Carissa Richardson,

Subject:

Transmittal of the following Framatome Proprietary Documents and Related Affidavit for Ameren/Callaway Records and Use, dated June 25, 2020.

4. Framatome Letter Framatome-20-05105, from Josh Harrison to Carissa Richardson,

Subject:

51-9312589-000 Callaway Unit 1 Steam Generator Operational Assessment to Support Deferral of Planned Inspections from 1 R24 to 1R25, dated July 14, 2020.

5. Framatome Document 51-9259621-000, Callaway Unit I SG Condition Monitoring for Cycles 19, 20 and 21 and Final Operational Assessment for Cycles 22, 23 and 24.

6. NRC ADAMS Accession No. ML20203M328, Callaway Plant Unit 1, Supplement to License Amendment Request Regarding Deferral of Upcoming Steam Generator Inspection (LDCN 20-001 3).

7. Framatome Document 51-9177474-000, Callaway 1R18 Steam Generator Deposit Characterization.