05000458/LER-2019-004, For River Bend Station, Unit 1, Potential Loss of Safety Function for All ADS, (Automatic Depressurization System) Valves

For River Bend Station, Unit 1, Potential Loss of Safety Function for All ADS, (Automatic Depressurization System) Valves

ML19357A229
Person / Time
Site:	River Bend
Issue date:	12/23/2019
From:	Vercelli S Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RBG-47985 LER 2019-004-00
Download: ML19357A229 (4)

LER-2019-004, For River Bend Station, Unit 1, Potential Loss of Safety Function for All ADS, (Automatic Depressurization System) Valves

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i)
4582019004R00 - NRC Website

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Entergy RBG-47985 December 23, 2019 Attn: Document Control Desk U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Entergy Operations, Inc.

River Bend Station 5485 U.S. Highway 61N St. Francisville, LA 70775 Tel: 225-381-4177 Steven P. Vercelli Site Vice President River Bend Station 10 CFR 50.73

Subject:

Licensee Event Report 50-458 / 2019-004, "Potential Loss of Safety Function for all ADS (Automatic Depressurization System) Valves".

River Bend Station, Unit 1 NRC Docket No. 50-458 Renewed License No. NPF-47

. In accordance with 10 CFR 50.73, enclosed is the subject Licensee Event Report. This document contains no commitments. If you have any questions, please contact Mr. Tim Schenk at 225-381-4177.

Sincerely, SPV/djp

Enclosure:

Licensee Event Report 50-458 / 2019-004, "PotenUal Loss of Safety Function for all ADS (Automatic Depressurization System) Valves".

cc:

NRC Region IV Regional Administrator, w/o Enclosure NRC Senior Resident Inspector - River Bend Station, Unit 1 Ji Young Wiley, Department of Environmental Quality, Office of Environmental Compliance, Radiological Emergency Planning and Response Section Public Utility Commission of Texas, Attn: PUC Filing Clerk

• NRC Project Manager

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)

, the NRC may not conduct or sponsor, and a

1. Facility Name River Bend Station - Unit 1

4. Title person is not required to respond lo, the information collection.

2. Docket Number 3.Page 05000 458 1

OF 3

Potential Loss of Safety Function for all ADS (Automatic Depressurization System) Valves.

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved Month Day Year Year I Sequential I Rev Month Day Year Facility Name Docket Number Number No.

NA 05000 NA 10 24 2019 2019 004 00 12 23 2019 Facility Name Docket Number NA NA 05000

9. Operating Mode

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i)

50. 73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 1 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1 )(i)(A)

50. 73(a)(2)(iv)(A) 50.73(a)(2)(x)

10. Power Level 20.2203(a)(2)(ii) 50.36(c)(1 )(ii)(A) 0 50.73(a)(2)(v)(A) 73.71 (a)(4) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 100 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 0 50. 73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2,203(a)(2)(vi) 50.73(a)(2)(i)(B)

50. 73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)

Other (Specify in Abstract below or in REPORTED CONDITION 05000-I 4

5 8

NUMBER NO I

YEAR SEQUENTIAL REV

- r-,

004 1-0 Both trains of ADS were inoperable due to the failure of compressor SW-C4A to maintain pressure with SW-C4B tagged out. ADS header pressure dropped below the Technical Specification limit of 131 psig and caused the ADS function of seven SRV's to be declared Inoperable. The station entered Technical Specification 3.5.1 Condition G requiring the station to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. As a result, this event is being reported under 10 CFR 50.73(a)(2)(v)(A) and 10 CFR 50.73(a)

• (2)(v)(D).

FAILURE ANALYSIS Maintenance was executed to re-build the 'B' Train ADS AOV's. Post event causal analysis revealed that issues with two of these valves caused the ADS header to 1.eak and lose pressure. Technicians discovered a rolled O-ring in one valve and the other was not shuttling properly. The AOV with the rolled O-:-ring was re-built and tested prior to installation and the AOV not shuttling properly was replaced with a new valve. This maintenance evolution ultimately exposed a gap in maintenance technician's* performance of best practices and skills required.

In addition, the portion of the ADS supply header where pressure is sensed is bounded by check valves which isolate the ADS Supply Header and the ADS accumulators. As header pressure began to lower, air pressure was contained within the piping and accumulators bounded by these check valves. ADS Supply Header pressure lowered due to the identified leaks in the 'B' Train ADS and as a result of air supplied to the Suppression Pool Level Transmitter Bubbler as seen in illustration provided.

CORRECTIVE ACTION TO PREVENT REOCCURENCE Actions are planned to be issued in the stations Corrective Action Process to address causal factors identified in Maintenance Fundamentals and Technical Skills. Other causal factors in Risk Management of Safety Significant Systems are also planned to have Corrective Actions assigned in this same condition report.

PREVIOUS OCCURRENCE EVALUATION There have been no similar events reported by River Bend Station in the past three years.

SAFEY SIGNIFICANCE The ADS system was declared inoperable for approximately 40 minutes due to the ADS Supply Header pressure lowering below the Technical Specification limit of 131 psig. During that time both the HPCS and RCIC were operable and the ADS function was maintained by ADS Accumulator check valves. An engineering evaluation, based on recent leak rate testing of the check valves, concluded that pressure in the ADS accumulators was maintained well above the minimum required pressure. This would, by design, ensure 2 ADS actuations at 70% drywell pressure and 4 actuations at normal drywell pressure. Additionally, the PVLCS system remained capable of maintaining a minimum pressure of 101 psig (USAR 5.2.2.4.1) to ensure long-term operability of the ADS valves. Note that operation of the PVLCS to supply accumulators is governed by pmcedure and that the lowest pressure experienced during this event was 10 8 psig in the "A" header.

During this event, no radiological release or environmental impact occurred. It was also of minimal consequence to the health and safety of the public. Therefore, there was no Safety System Functional Failure of the ADS. Page 3

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