JAFP-23-0008, Supplement to Inservice Inspection Summary Report Cycle 25

Supplement to Inservice Inspection Summary Report Cycle 25

ML23053A217
Person / Time
Site:	FitzPatrick
Issue date:	02/22/2023
From:	Mark Hawes Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
JAFP-23-0008
Download: ML23053A217 (1)

Text

Constellation.

JAFP-23-0008 February 22, 2023 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 James A. FitzPatrick NPP P.O. Box 110 Lycoming, NY 13093 Mark Hawes Acting Regulatory Assurance Manager - JAF James A. FitzPatrick Nuclear Power Plant Renewed Facility Operating License No. DPR-59 NRC Docket No. 50-333

Reference:

1.

Dear Sir or Madam:

Supplement to lnservice Inspection Summary Report Cycle 25 Constellation letter, lnservice Inspection Summary Report Cycle 25, JAFP-22-0053, dated December 20, 2022 On December 20, 2022, Reference 1 submitted the Owner's Activity Report (OAR) for examinations conducted during the 2022 Refuel outage 25 (FP1 R25). This letter supplements the OAR with additional supporting information for a condition identified in the Enclosure to Reference 1, Table 1: "Items with Flaws or Relevant Conditions That Required Evaluation for Continued Service". Specifically, item E-A, E1.11 for Drywall Liner.

The Enclosure to this letter provides the information in accordance with 1 O CFR 50.55a(b )(2) (ix)(A)(2).

There are no new regulatory commitments contained in this letter. If you have any questions in this regard, please contact Mr. Peter Logar, Programs Engineering Branch Manager, at (315) 791-3620.

Very truly yours, Mark Hawes Acting Regulatory Assurance Manager MH

Enclosure:

Technical Evaluation 637628 Evaluate Pitting of Drywall Liner at Concrete Interface 256' Elevation cc:

NRC Region 1 Administrator NRC Project Directorate NRC Resident Inspector NYSERDA

JAFP-23-0008 ENCLOSURE Technical Evaluation 637628 Evaluate Pitting of Drywell Liner at Concrete Interface 256 Elevation (5 Pages)

EC 637628 REV. 0 TECHNICAL EVALUATION 637628 EVALUATE PITTING OF DRYWELL LINER AT CONCRETE INTERFACE 256 ELEVATION

1) CONTEXT During the RFO25 (2022) General Visual (GV) examination 1R25-IWE-VT-013 (Attachment 3) of the drywell interface on 256 elevation, seven locations of heavy corrosion were noted at the interface between the liner and the concrete floor (see IR 04525962) in addition to six locations identified in RO23 (see IR 04174135 & EC 625691). This is a relevant condition per ER-AA-335-018 Rev. 15.

To determine the extent of wall loss in the corroded areas a VT-1 was performed on the original six locations required by ASME and a supplemental UT was performed on all thirteen pitted locations as directed by the ISI engineer. See results in UT report 1R25-IWE-UT-001 (Attachment 1) and VT-1 report 1R25-IWE-014(Attachment 2) and the table below.

2) REASON FOR EVALUATION The drywell steel liner to concrete interface at elevation 256 has exhibited signs of corrosion for multiple outages due to the absence of protective coating. Although the drywell is an inert environment during the operating cycle, it is exposed to oxygen during outages. Additionally, steam leaks, air handling system water leaks and basement flooding make this area susceptible to corrosion due to moisture collection as a containment low point.

The ASME XI acceptance criteria for VT-1 examination of containment surfaces requiring augmented examination are defined in IWE-3520. IWE-3521 states pressure-retaining component corrosion or erosion that exceeds 10% of the nominal wall thickness is a relevant condition and must meet the requirements of IWE-3122 prior to continued service. The supplemental UT and VT-1 examinations identified one location that exceeds 10% wall loss, it is shown on Figure 1 as location G. Therefore, this evaluation will demonstrate the acceptability of the as found condition of the drywell steel liner at the concrete interface in accordance with IWE-3122.3, acceptance by engineering evaluation.

IWE-2500(d) states when conditions exist in the accessible areas that could indicate the presence of, or result in, degradation in an inaccessible area, an engineering evaluation shall be performed to determine the acceptability of the inaccessible area. Given the condition of the drywell steel liner to concrete interface an evaluation to determine the acceptability of the inaccessible areas is required.

10 CFR 50.55a(b)(ix)(A)(2) states:

(2) For each accessible area identified for evaluation, the applicant of licensee must provide the following in the ISI Summary Report as required per IWA-6000:

I.

A description of the type and estimated extent of degradation, and the conditions that lead to the degradation II.

An evaluation of each area, and the result of that evaluation; and III.

A description of necessary corrective actions.

EC 637628 REV. 0 This evaluation will also address the requirement of 10 CFR 50.55a stated above.

3) DETAILED EVALUATION The FitzPatrick Containment ISI Program outlines the requirements for the inspection of Class MC pressure-retaining components (primary containment) and their integral attachments in accordance with the requirements of 10 CFR 50.55a and the ASME Boiler and Pressure Vessel Code, 2007 Edition through the 2008 Addenda,Section XI, Subsection IWE.

The primary inspection method for the primary containment and its integral attachments is visual examination. Visual examinations are performed either directly or remotely with illumination and resolution suitable for the local environment to assess general conditions that may affect either the containment structural integrity or leak tightness of the pressure retaining component. Supplemental examination methods and techniques may be performed when visual examinations detect flaws or evidence of degradation requiring evaluation The bottom portion of the drywell is considered to be inaccessible because it is adjacent to concrete on either side. The chemistry of concrete is very basic (high pH), which protects steel in contact with it from rusting, much like rebar contained within the concrete is protected from rusting. The concrete in at the 256 elevation was poured into the drywell during construction effectively coating all inaccessible surfaces making corrosion at these locations unlikely. In addition, oxygen must be present for the drywell steel to oxidize. The drywell is purged with nitrogen most of the time, limiting the presence of oxygen. The area of drywell steel that would have the highest exposure, and therefore vulnerability to moisture and oxygen, would be at the location where the liner and floor meet, where we have 13 spots of corrosion/pitting. This location is exposed to oxygen during a refueling outage and is where water leakage in the drywell could collect. The inaccessible portion of the drywell below the floors surface could also be exposed to moisture, but it would not have as much exposure to oxygen, therefore it can be concluded that the area beneath the 256 floor elevation is in better condition than the corroded areas at the liner interface.

To specifically address items (i), (ii) and (iii) from 10 CFR 50.55a(b)(ix)(A)(2) mentioned above:

i.

The type of degradation being evaluated is the corrosion and pitting of 13 locations of the steel drywell liner at the 256 elevation of the drywell reported in IR 04174135 & IR 04525962. The UT results shown below document minor material loss as a result of the corrosion. The liner has exhibited signs of corrosion for multiple outages due to the absence of protective coating.

Although the drywell is an inert environment during the operating cycle, it is exposed to oxygen during outages. Additionally, steam leaks and air handling system water leaks make this area susceptible to corrosion due to moisture collection as a containment low point.

ii.

According to calculation JAF-CALC-PC-04436 (reference 1), the nominal wall thickness for drywell shell and vent system for the lower sphere of the drywell is 1.375 with a minimum required thickness of 0.863. UT exams were performed and are noted below and in attachment 2, they show that significant margin exists in the degraded areas when compared to the minimum required thickness.

EC 637628 REV. 0 iii.

In order to prevent further corrosion all areas without protective coating must be prepared and recoated per IS-M-01. IR 04526882 discusses the need for recoating with the recommended action to perform the recoating in RO26 (2024).

As illustrated on drawing 3.11-44 (reference 3), it is important to note that the drywell lower sphere shell thickness is not uniform. It consists of an assembly of different insert plate sizes. The typical nominal thickness is 1.375 however, in certain areas it can be 1.5 and up to 2.75. Field measurements indicate that locations below vent headers have a nominal thickness of 2.75 whereas locations in between vent headers tend to be closer to 1.5. The nominal thickness, as measured by UT thickness readings, of the unaffected liner plate in each area of degradation is noted in the table below. See Figure 1 for NDE locations.

The table below provides the UT thickness of the unaffected liner plate in each area of degradation, physical pitting measurements taken with a Cambridge gauge, and the remaining wall thickness in each area of degradation.

Location Number Perimeter Location Nominal Thickness Remaining Liner Thickness Minimum Required Thickness Determination 1

See Figure 1 2.816 2.737 0.863 Pass 2

See Figure 1 2.84 2.683 0.863 Pass 3

See Figure 1 1.529 1.431 0.863 Pass 4

See Figure 1 2.797 2.659 0.863 Pass 5

See Figure 1 2.847 2.69 0.863 Pass 6

See Figure 1 2.8 2.682 0.863 Pass A

See Figure 1 2.815 2.658 0.863 Pass B

See Figure 1 1.53 1.491 0.863 Pass C

See Figure 1 2.824 2.745 0.863 Pass D

See Figure 1 2.82 2.682 0.863 Pass E

See Figure 1 2.809 2.652 0.863 Pass F

See Figure 1 2.836 2.698 0.863 Pass G

See Figure 1 1.399 1.242 0.863 Pass

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EC 637628 REV. 0

4) CONCLUSIONS Based on the information presented in the table above, all locations have significant margin, and it can be concluded that the drywell shell thickness at 256 elevation remains in compliance with the design basis requirements. In addition, it is determined that the inaccessible areas are capable of meeting the design basis requirements. In order to prevent further corrosion/pitting of the drywell liner the floor interface should be cleaned and recoated per IS-M-01 during RO26.

5) ATTACHMENTS

1. Visual Examination of IWE Surfaces (VT-1), Report Number 1R25-IWE-VT-014

2. UT Erosion/Corrosion Examination, Report Number 1R25-IWE-UT-001

3. Visual Examination of IWE Surface (VT-G), Report Number 1R25-IWE-VT-013

6) REFERENCES 1

JAF-CALC-PC-04436 Revision 0, Minimum Shell Thickness of Drywell and Vent System for IWE Inspection.

2 IWE-3520 Standards for Examination Category E-C, Containment Surfaces Requiring Augmented Examination.

3 Drawing 3.11-44, Revision B, Drywell Shell - General Plan.

4 IS-M-01, Rev 018, PREPERATION AND PAINTING OF PLANT STRUCTURES, COMPONENTS AND CONCRETE ITEMS 5

ER-AA-335-014, Rev 012, VT-1 Visual Examination