05000395/LER-2021-001, (Vcsns), Unit 1, Condition Prohibited by Technical Specifications

(Vcsns), Unit 1, Condition Prohibited by Technical Specifications

ML21238A158
Person / Time
Site:	Summer
Issue date:	08/26/2021
From:	Lippard G Dominion Energy South Carolina
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
21-258, VCS-LIC/JB RO LER 2021-001-00
Download: ML21238A158 (5)

LER-2021-001, (Vcsns), Unit 1, Condition Prohibited by Technical Specifications

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3952021001R00 - NRC Website

text

V.C. Summer Nuc lear Station ~ Dominion Bradham Blvd & Hwy 215, J enk insville, SC 2 9 065 Mai ling Address: ~ Energy P.O. Box 88, Jenkinsvi lle, SC 29065 DominionEnergy.com August 26, 2021

Document Control Desk Serial No.: 21-258 U.S. Nuclear Regulatory Commission VCS - LIC/JB RO Washington, DC 20555 Docket No. 50-395 License No. NPF-12

DOMINION ENERGY SOUTH CAROLINA (DESC)

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 LICENSEE EVENT REPORT 2021-001-00 CONDITION PROHIBITED BY TECHNICAL SPECIFICATIONS

Dominion Energy South Carolina hereby submits Licensee Event Report (LER) 2021 - 001 - 00 for VCSNS. This report provides details concerning an operation or condition prohibited by Technical Specifications and is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B). The attached LER also fulfills "Reporting of Defects and Noncompliance" requirements under 10 CFR 21.2(c).

Should you have any questions, please call Mr. Justin Bouknight at (803) 941-9828.

Sincerely,

George A. Lippard Site Vice President V.C. Summer Nuclear Station

Enclosure

Commitments contained in this letter: None

cc:

G. J. Lindamood - Santee Cooper L. Dudes - NRG Region II V. Thomas - NRG Project Mgr.

NRG Resident Inspector J. N. Bassett-INPO Marsh USA, Inc.

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMS: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)

V.C. Summer Nuclear Station, Unit 1 05000 395 1 OF 4

4. Title

Condition Prohibited by Technical Specifications

5. Event Date 6. LER Number 7. Report Date 8. Other Facilities Involved

Month Day Year Number No.

05000 06 28 2021 2021 - 001 - 00 8 26 2021 Facility Name Docket Number

05000

9. Operating Mode 110. Power Level 1 100%

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In 2010, Nuclear Logistics (NLI) was contracted by V.C. Summer Nuclear Station (VCSNS) to replace its 3 safety-related chillers. On June 28, 2021, V.C. Summer Nuclear Station (VCSNS) was notified that the bolted diagonal supports for the NU safety related chillers (XHX0001 A/1 B/1 C) have a bolt (the pin) which would not withstand the combined design seismic and thermal loads. The vendor conclusion was confirmed by VCSNS personnel. As a result, the previous NU chiller support frame design does not meet required seismic qualification under VCSNS procurement specification for compliance with 10 CFR 50 Appendix A, Criterion 2. At the time of discovery, only the 'A' Chiller had been replaced. Additional support bracing was designed, fabricated, and installed for the affected in-service 'A' Chiller. The enhanced bracing installation has corrected the issue and restored compliance with Technical Specifications (TS). There were no seismic events of consequence to the 'A' Chiller functionality during the time of the deficient seismic restraint (February 17, 2017 until June 29, 2021). However, there were times when the 'A' Chiller was credited as a TS support component, resulting in the plant operating in a condition prohibited by TS.

1.0 DESCRIPTION OF THE EVENT

In 2010, NU (now a part of Paragon Energy Solutions) was contracted by V.C. Summer Nuclear Station (VCSNS) to provide 3 replacement safety-related chillers. On June 28, 2021, Paragon Energy Solutions notified V.C. Summer Nuclear Station (VCSNS) that the bolted diagonal supports for the NU safety-related chillers (XHX0001A/1 B/1 C) have a bolt (the pin) which cannot withstand the combined seismic and thermal loads. The deficiency was confirmed by VCSNS personnel, following review of the vendor documentation. As a result, the NLI chiller support frame design did not meet required seismic qualification under VCSNS procurement specification for compliance with 10 CFR 50 Appendix A, Criterion 2. At the time of discovery, only the 'A' Chiller had been replaced. The 'B' Chiller was in the process of being replaced. The 'C' Chiller was operable, with its replacement being fabricated by the vendor. This condition had existed for the 'A' Chiller since February 17, 2017. The 'A' Train of Chilled Water was declared non-functional at 1435 hrs on June 28, 2021 and the station entered Technical Specification (TS) Action Statement 3.5.2.a.

Additional support bracing was designed, fabricated, and installed for the affected in-service 'A' Chiller. The action statement was exited within the allowable 72-hour outage time on June 29, 2021 at 1030 hrs. The enhanced design was applied to the 'B' Chiller, prior to its return to service, and will be applied to the replacement 'C' Chiller at the vendor facility prior to its delivery and installation. The enhanced bracing installation has corrected the issue and brought the issue in line with VCSNS seismic design specifications. There were no seismic events of consequence to the 'A' Chiller functionality during the time of the deficient seismic restraint.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS

Although not specifically addressed in TS, Safety Related Chilled Water is required for operability of TS-required equipment. The 'A' Chiller was installed February 17, 2017 and subsequently credited as a TS support component. A past functionality evaluation performed on the 'A' Chiller determined the 'A' Chiller was non-functional, as a result of inadequate seismic restraints, from February 17, 2017 to June 29, 2021. During this period, there were occasions when

'A' Chiller was one of two chillers credited for support of the Emergency Core Cooling System (ECCS) equipment, required per TS 3.5.2. The most-limiting ECCS component supported by the Safety Related Chilled Water are the charging pumps. The non-functional 'A' Chiller could have also impacted availability of the Control Room Emergency Filtration System (CREFS) (TS 3.7.6) and potentially other safety-related equipment for some scenarios. These past condition(s) prohibited by TS were not known until Paragon submitted the Part 21 information on June 28, 2021. There were no seismic events of consequence to the 'A' Chiller functionality during the time of the deficient seismic restraint (February 17, 2017 until June 29, 2021).

The Chilled Water System provides cooling to safety-related areas (TS Table 3.7-7) as an attendant cooling system and supports the comfort requirements for the Control Room Emergency Filtration Systems (CREFS). The Chilled Water System is necessary to ensure equipment located within these areas can withstand the environmental effects of a postulated FSAR chapter 15 event.

The 'A' Chiller (XHX0001A) is designed to provide a continuous flow of 45 deg F chilled water to various safety-related cooling coils in the plant during both normal and emergency conditions. All TS areas in Table 3.7-7, with the exception of Areas 23-30 (cooled by outside air ventilation), are cooled by chilled water air handling units. If the temperature limits for any room listed in TS Table 3.7-7 are exceeded for more than eight hours, a Special Report demonstrating operability of the pertinent equipment is required per TS 3.7.9.a. If those values are exceeded by more than 30 deg F for more than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> the equipment in the room is considered inoperable per TS 3.7.9.b.

In order for the 'A' Chiller to continuously deliver 45 deg F water, all heat loads generated in the areas served by the Chilled Water System must be transferred to the chilled water fluid, and absorbed by the refrigeration system, which is then rejected to the Service Water System. The 'A' Chiller is designed to provide this function under all operating scenarios.

Therefore, it is required to operate continuously, when started on demand, and the total heat removal rate (cooling capacity) must meet or exceed the total steady-state heat load rates for the Chilled Water System supported areas. This is required during both normal and accident heat load conditions, provided the system is Seismic Category I components.

3.0 CAUSE OF THE EVENT

The cause of the non-functionality was the inadequate seismic design for bracing on the installed 'A' Chiller, as well as for the 'B' was in the process of being installed. Specifically, the issue was the bolts (pins) utilized in the seismic bracing design were not adequate for the design load.

4.0 CORRECTIVE ACTIONS

Additional support bracing was designed, fabricated, and installed for the affected in-service 'A' Chiller. This modification was completed on the installed 'A' Chiller on June 29, 2021. The same design modification was applied to the 'B' Chiller prior to its return to service and will be applied to the enhanced 'C' Chiller prior to its installation. The enhanced seismic restraint has corrected the issue, restoring compliance with the VCSNS seismic design and TS.

VCSNS personnel have engaged with Paragon regarding the design and fabrication of its chillers and continue to provide oversight in accordance with procurement and quality assurance program requirements.

5.0 SIMILAR EVENTS

A review of Licensee Event Reports (LERs) and condition reports (CRs) at VCSNS for the three previous years did not identify any similar events.

6.0 MANUFACTURER I MODEL INFORMATION

Paragon/Nuclear Logistics (NU) 280-ton Custom Chillers, Serial Numbers XHX-0001A, XHX-0001 B, and XHX-0001 C.

The Chillers were originally supplied to VC Summer Nuclear Station by Nuclear Logistics under purchase order NU-02SR726683 in 2010.

7.0 ADDITIONAL INFORMATION

While this LER describes a condition that could have had adverse impacts to equipment qualification following a seismic event, there was no such event. As a result, the chilled water system and the equipment it supports were not impacted by the design vulnerability that has now been corrected.