1CAN052104, Notification of Deviation from Materials Reliability Program (MRP) 2019-008
| ML21131A169 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/11/2021 |
| From: | Couture P Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 1CAN052104 | |
| Download: ML21131A169 (8) | |
Text
Entergy Operations, Inc.
1340 Echelon Parkway Jackson, MS 39213 Tel 601-368-5102 Phil Couture Senior Manager, Fleet Regulatory Assurance NEI 03-08 1CAN052104 May 11, 2021 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Notification of Deviation from Materials Reliability Program (MRP) 2019-008 Arkansas Nuclear One, Unit 1 NRC Docket Nos. 50-313 Renewed Facility Operating License No. DPR-51 In accordance with Appendix B, Section 8.1.c of Nuclear Energy Institute (NEI) 03-08, Guideline for the Management of Materials Issues, Revision 3, Entergy Operations, Inc.
(Entergy) is notifying the U. S. Nuclear Regulatory Commission (NRC) that Arkansas Nuclear One, Unit 1 (ANO-1) has processed a deviation from a needed Interim Guidance in MRP 2019-008, Interim Guidance for NEI 03-08 Needed Requirements for US PWR Plants for Management of Thermal Fatigue in Non-Isolable Reactor Coolant System Branch Lines. The requirements of MRP 2019-008 shall be implemented within two refueling outages after August 1, 2019.
There are four Needed requirements in the Interim Guidance (IG) provided in MRP-2019-008.
Requirements 1, 3 and 4 have been satisfied or determined to not be applicable for ANO-1 and require no additional inspections. One line that screened-in, in accordance with Requirement 2 requires a one-time examination of the piping.
NEI 03-08 allows deviation from Needed elements with the appropriate justification and documentation. The deviation was documented in accordance with Entergys corrective action program and approved by the appropriate levels of Entergy Management. Enclosed is a summary of the evaluation and justification for the deviation.
This Electric Power Research Institute (EPRI) MRP Issue Program Owner has been informed of the deviation for a needed requirement in accordance with NEI 03-08.
This notification is provided for information only. No approval or action is required.
1CAN052104 Page 2 of 2 This report contains no new regulatory commitments.
Should you have any questions or require additional information, please contact Riley Keele, Manager, Regulatory Assurance, at (479) 858-7826.
Respectfully, Digitally signed by Philip Philip Couture Date: 2021.05.11 Couture 07:54:30 -05'00' Phil Couture PC/rwc
Enclosure:
Justification for the Deviation from MRP 2019-008 cc: NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One
Enclosure 1CAN052104 Justification for the Deviation from MRP 2019-008
1CAN052104 Enclosure Page 1 of 5 Justification for the Deviation from MRP 2019-008 This deviation is for the needed Interim Guidance in Materials Reliability Program (MRP) 019-008. The justification for the deviation is provided below.
Background:
Materials Reliability Program (MRP) 2019-008, Interim Guidance for NEI 03-08 Needed Requirements for US PWR Plants for Management of Thermal Fatigue in Non-Isolable Reactor Coolant System Branch Lines, was issued April 1, 2019. The requirements of MRP 2019-008 shall be implemented within two refueling outages after August 1, 2019.
The operating experience (OE) from the MRP 2019-008 is based on Westinghouse designed plants. Both units of another site experienced rejectable weld indications at the upstream elbow weld at the first elbow off the Residual Heat Removal (RHR) suction line. Subsequent thermocouple measurements have indicated thermal cycling in the horizontal piping downstream of the elbow. However, this line had screened out of MRP-146 because the MRP-170 analytical software predicted the horizontal portion of the piping stays hot (no stratification/de-stratification cycling expected).
There are four Needed requirements in MRP-2019-008. These requirements are:
- 1. DH [Down Horizontal] lines previously exempted by the Generic Analysis option (i.e., R-Strat) described in MRP-146, paragraph 2.1.5.4 shall be inspected every other
[Refueling Outage] RFO if all the following conditions are true:
x Cracking has been identified x The cause of the cracking could not be identified and mitigated / eliminated.
- 2. For those large bore (> 4") DH lines that previously screened-out as "HOT" (per MRP-146) a one-time examination of the piping at the first 45-degree (or 90-degree) elbow is required (as represented on Figure 1A [of MRP 2019-008]). As a minimum, the inspection volume shall include the base metal and welds represented in Figure 1B [of MRP 2019-008].
Note: credit may be taken for previous exam if:
x Previous exam volume requirements bound those of this IG.
- 3. Sites shall review MRP-146 "screened" out UH/H lines to determine susceptibility to in-leakage from cross-flow. To perform this determination, interconnected lines, or lines sharing a common header, with only check-valve isolation between [Reactor Coolant System] RCS loops, shall be "screened in" as potentially susceptible to in-leakage / cross-flow. For the new "screened-in" lines a one-time inspection shall be
1CAN052104 Enclosure Page 2 of 5 performed using the volumetric requirements of MRP-146 Rev. 2 Figure 2-11 through Figure 2-14, as applicable) and as amended by IG #4 below.
Note: credit may be taken for previous exam if:
x Previous exam volume requirements bound those of this IG.
- 4. Future fatigue examinations of the bottom inner third thickness of base metal as indicated in Figure 2-20 of MRP-146, Rev. 2 shall be 1" wide.
This notification was issued late into the window for scoping for the Arkansas Nuclear One, Unit 1 (ANO-1) Fall 2019 outage. The Fall 2019 refueling outage was the first refueling outage within the timeframe of MRP 2019-008.
The evaluations were started in August 2020 and finished at the end of October 2020 with preliminary results provided on November 3, 2020, with the identification of a required inspection later communicated to ANO-1 Outage Management. The review identified one line with two welds for a one-time inspection per Interim Guidance (IG) 2. Based on the 2 Rem dose estimate after all dose goals for the outage were established, the NEI 03-08 needed examination cannot be completed in the Spring 2021 refueling outage (second refueling outage after April 2019).
The proposed date of the future examination will allow adequate time for budgeting, planning, dose allocation and coordinating the NEI 03-08 needed examination in the Fall 2022 refueling outage (1R30).
Evaluation:
Item 1, 3 and 4 have been satisfied or determined to be not applicable for ANO-1 and require no additional inspections. IG 2 had one line that screened-in and requires a one-time examination of the piping at the first 45-degree (or 90-degree) elbow. As a minimum, the inspection volume shall include the base metal and welds represented in Figure 1B of MRP 2019-008. The line that screened-in contains two weld locations that will require a one-time inspection of each weld.
Entergy has elected to extend the examination of the downstream weld of the elbow to 1R30 and the upstream weld has been mitigated by a structural weld overlay. The IG is designed to minimize the probability of thermal fatigue cracks that exceed allowable flaw dimensions or result in forced or extended outages.
IG 2 is from OE at a plant that experienced rejectable weld indications at the upstream elbow weld at the first elbow off the RCS hot leg RHR suction line. The line had screened out of MRP-146 because the MRP-170 analytical software predicted the horizontal portion of the piping stays hot (no stratification/de-stratification cycling expected).
DH location DHR (Decay Heat Removal) 1A (Run 1) previously screened-out as "HOT" (per MRP 146 Revision 2). The DHR 1A (Run 1) was updated (slightly longer) for the vertical pipe length used in the current MRP-170 run and has screened this line out since cycling does not penetrate the horizontal segment. Due to recent OE with similar configurations (relatively long
1CAN052104 Enclosure Page 3 of 5 effective vertical length to the horizontal segment), a one-time examination shall be performed on this location per the requirements of IG 2. It is recommended that inspections be performed on both welds of the elbows joining the vertical and horizontal segments. The applicable examination volumes would be those shown in Figures 2-15 and 2-18 of MRP-146 Revision 2 as modified by Figure 1B of MRP 2019-008 for the lower and upper welds.
1CAN052104 Enclosure Page 4 of 5 The presence of a structural weld overlay precludes full examination of the upper elbow weld original material. This is essentially 0% limited examination coverage and will be technically evaluated in Entergy's Corrective Action Program (CAP) as required in MRP-146 Revision 2, Section 2.4.1, p.2-30, Item 4.a. A best effort examination will be performed during 1R30 in 2022. While full structural weld overlays have been shown to mitigate Primary Water Stress Corrosion Cracking (PWSCC) crack growth due to the compressive effects inherent with a weld overlay application, mitigation of thermal fatigue crack growth has not been evaluated or analyzed. The lower and upper elbow weld section will be delayed for one refueling outage, from 1R29 in 2021 to 1R30 in 2022.
The review of MRP 2019-008 DH line location concludes that the line will be found not susceptible to the thermal fatigue cracking described in the MRP. ANO-1 has enhanced detection capabilities for RCS leakage, as discussed in ANO-1 Safety Analysis Report (SAR)
Section 4.2.3.8, equipment to detect a one gallon per minute leak in one hour to support use of Leak Before Break (LBB).
This line is not in the scope of the LBB analyses, but the detection methods still provide the capability to detect leakage and Operations performs a daily RCS leakrate calculation per procedures. Thus, the overall risk to the station is mitigated such that a leak will be detected, and plant shutdown commenced prior to a gross structural failure.
1CAN052104 Enclosure Page 5 of 5
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Conclusion:==
Delaying the examination by one cycle does not pose any additional risk to ANO-1 and is acceptable. There is one line that screened-in based on the OE described in MRP 2019-008.
The one line has two affected welds, one of which has a structural weld overlay. The recommendation to complete the one-time inspection is based on recent OE with similar configurations (relatively long effective vertical length to the horizontal segment). Per discussion with the Thermal Fatigue Focus group, other plants that have performed the inspection per the MRP 2019-008 IG have had no findings.