05000458/LER-2018-002, Inadvertent High Pressure Co Re Spray Initiation and Loss of Safety Function Due to Inadequate Work Instruction Mitigation Actions

Inadvertent High Pressure Co Re Spray Initiation and Loss of Safety Function Due to Inadequate Work Instruction Mitigation Actions

ML18170A347
Person / Time
Site:	River Bend
Issue date:	06/19/2018
From:	Maguire W Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RBG-47872 LER 2018-002-00
Download: ML18170A347 (6)

LER-2018-002, Inadvertent High Pressure Co Re Spray Initiation and Loss of Safety Function Due to Inadequate Work Instruction Mitigation Actions

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(v), Loss of Safety Function
4582018002R00 - NRC Website

text

Entergx RBG-47872 June 19,2018 Attn: Document Control Desk U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738

Subject:

Dear Sir or Madam:

Licensee Event Report 50-458/2018-002-00 River Bend Station, Unit 1 Docket No. 50-458 License No. NPF-47 Entergy Operations, Inc.

River Bend Station 5485 U.S. Highway 61 N St. Francisville. LA 70n5 Tel 225-381-4374 William F. Maguire Site Vice President 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, WFM/twf Enclosure cc:

(with Enclosure)

U.S. Nuclear Regulatory Commission Attn: Ms. Lisa M. Regner, Project Manager 09-0-14 One White Flint North 11555 Rockville Pike Rockville, MD 20852 U.S. Nuclear Regulatory Commission Region IV 1600 East Lamar Blvd.

Arlington, TX 76011-4511

RBG-47872 Page 2 of 2 NRC Senior Resident Inspector Attn: Mr. Jeff Sowa 5485 U.S. Highway 61, Suite 1 St. Francisville, LA 70775 Public Utility Commission of Texas Attn: PUC Filing Clerk 1701 N. Congress Avenue P. O. Box 13326 Austin, TX 78711-3326 INPO (via ICES reporting)

RBF1-18-0116

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150~104 EXPIRES: 03/31/2020 (04-2018)

Est mated burden per response to comply with Ihb mandatory coIlec:lon request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

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LICENSEE EVENT REPORT (LER)

Reported lessons ~arned afe ncorporated IIlto the lice"sing process and led back to Industry. Send comments regording burden est mote 10 the Informa:ion Services Branch

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"0 (T-2 F43), U.S. N.de.r Regulatory Commlss on, Washington. DC 20555-0001, or bye-mail

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3. Page R iver Bend Station -

Unit 1 458 4

05000 1

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4. Title Inadvertent High Pressure Core Spray Initiation and Loss of Safety Function due to Inadequate Work Instruction Mitigation Actions.

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved Month Day Year Vear I Sequential I Rey Month Facility Name Docket Number Numbor No.

Dav Ye.r NA 05000 NA Facility Name Dockot Numb.r 04 26 2018 2018 -

002 -

00 06 19 2018 NA 05000 NA

9. Operating Mode

11. This Report Is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)

D 20.2201(b)

D 20.2203(;))(3)(1)

D 50.73(0)(2)(11)(1\\)

D 50.73(9)(2)(vlll)(l\\)

D 20.2201 (d)

D 20.2203(a)(3)(II)

D 50.73(a)(2)(II)(8)

D 50,73(a)(2)(vlll)(B) 1 D

D D

D 20,2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(lli) 50.73( )(2)(IK)(I\\)

D 20.2203(a)(2)(1)

D 50.36(c)( 1 )(11(1\\)

0 50.73((I)(2)(lv)(l\\)

D 50 73(a)(2)(x)

10. Powor Lovol D 20,2203(a)(2)(1I) 0 50.36(c)( 11(II)(A)

D 50.73(a)(2)(v)(l\\)

D 73.71( )(4)

D 20.2203(11)(2)(111) 0 50.36(c)(2)

D 50.73(0)(2)(v)(8)

D 73.71(a)(5)

D 20,2203(a)(2)(lv)

D bO.46(3)(3)(II)

D !l0. f3(o)(2)(v)(C)

D f3.1 f(a)(1) 100 0 20.2203(n)(2)(v)

D 50. 73(nl(~)( I )(A) 0 50. f3(n)(?)(v)(D) 0 73.7/(a)(2)(I) 0 20.n03(a)(2)(vl)

D 50. '3(a)(~)( I )(B )

D 50.73(0)(2)(vll)

D 73.7 f (a)(2)(II)

D bO.l3(u)(?)(I)(C)

D Other (Specify In I\\bstmct below or In NRC Form 3661\\)

12. L1consoo Contact for this LER L1cen.ee Contact Telephone Number (Include Area Code)

Tim Schenk, Manaqer -

Requlatory Assurance 225-381-4177 c.u **

8y."'" l N~mponont l N;"nuI""u,or RopOr1lblo 10 ICES J NA Clm I NA' y"om I Nc;np""ont M'f'u'.etur., I Ropor1lbl. to ICES NA NA NA NA NA

14. Supplomontal Roport Expoctod Month DIY VI.r D

0 15, Expected Submlulon Dato YOI (If Y'"

':Il"'I,kcl" 1:,. I-xl"" l.. cI S"I">lI.. I"" 1)"1" )

No NA NA NA Ab.tract (Lllnilio 1400 SPOCO!!. '.0.. npproxlmololy 111 single-spncoci typewrtllon hno~)

A115:31 CST on April 26, 2018, I&C techniCian s were restoring Reactor Vessel Water Level Transmitter B21-LTN081C to service with the R eactor operating in Mode 1 at 100% power. Ourll19 this transmitter restoration, the station experienced an invalid initiation of High Pressure Core Spray (HPCS) with injoction Into tho roactor vossel. Tho HPCS Olosel Gonorator also started per deSign, but did not connect to the SWitchgear because there was no bus under voltage. Operations terminated the Injection alter approximately 40 seconds in accordance w ith Alarm Response Procedures. The Feedwaler Level Control System resl-londed per design, and maintained nominal Reactor water levels. The cau s of this e vent was Inadequate work Instruction.

This event w as of minimal significance to the health and safety of the public, BACKGROUND High Pressure Core Spray (HPCS) IBG) is designed to limit the release of radioactive materials to the environment following a loss of coolant accident (LOCA) by injecting water into the Reactor Coolant System (RCS). HPCS is also designed to automatically initiate when level 2 is reached in the Reactor Pressure Vessel (RPV). The RPV level 2 signal is generated by Reactor Water Level Transmitters ("L T") in the Nuclear Boiler Instrumentation System. The. C ' reference leg of the Nuclear Boiler Instrumentation System contains two HPCS level 2 Water Level Transmitters.

REPORTED CONDITION On April 26, 2018 after replacing Reactor Water Level Transmitter B21-L TN081 C. an invalid initiation occurred resulting in the injection of HPCS.

With the Reactor operating in Mode 1 at 100% power, I&C technicians were sent to the field to replace the transmitter which is in the 'C' reference leg. In the process of returning the transmitter to service, air introduced during the installation caused a perturbation in the. C' reference leg. With two HPCS level transmitter on the. C' reference leg affected by this perturbation, HPCS initiFlted flnd the Division III Diesel Generfltor stflrted flS designed. Operators responded to the initiation by taking the appropriate actions per alarm response procedure. The HPCS system was placed in standby. the plant was stabilized and field activities stopped. All plant parameters responded as would be expected for an inadvertent actuation of the HPCS System, NRC notification of Emergency Core Cooling System (ECCS) discharge to RCS and subsequent disabling of a single train system (HPCS) was completed at 18:50 COT on April 26, 2018 (EN 53365).

iA troubleshooting procedure was developed and utilized to restore. C ' reference leg following the event.

jAlthough initially reported in accordance with 10CFR50.72(b)(2)(iv)(A), it has since been determined that the actuation signal to the HPCS system was invalid. This report is submitted in accordance with 10CFR50,73(a)(2)(iv)(A) for the invalid actuation of HPCS. This roport is also submitted in accordance with 1 OCFR50,73(a)(2)(v)(D) because the HPCS system was placed in standby and could not fulfill its safety function for a short period following this event.

CAUSAL ANALYSIS IAn organizational false sense of security eXisted based on past successful on line completion of a Reactor Water Level Surveill'lnce Test Procedure (STP). The mitigation strategy of this STP was used in the transmitter replacement work package. 1 his fauited mental model influenc d Inadequate risk recognition dunng the analysis, deSign, dev lopment. and implementation o( solutions. As a result, the risk screenin!=! conducted was not adequate (or the work performed. Work OrdtH instructlolls w~re Ilot Wrttt~1l III su (fi ci~llt d~ t ai l to pr~cl u du the tlVI:)Ilt.

CORRECTIVE ACTION TO PREVENT RECURRENCE I he following Acllonll hAvo been AS!!lgnod to prevont A recurrence of thl!! event And fire doctlmented In the stAtlon's corroctlve Action progrAm.

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05000-1 458 I ""

12018 1_ 1 SEQUENTIAL REV NUMBER NO.

002 1-0

- Conduct a review of Surveillance Test Procedures that impact reference leg instrumentation with ECCS initiation function.

Production Manager set and document expectations for work package detail and process rigor with Planning Department staff in accordance with station and corporate procedures.

Online Maintenance Scheduling Superintendent set and document expectations for process rigor with Work Control staff.

- Engineering Managers set and document expectations for process rigor for all technical activities.

Maintenance Manager set and document expectations for process rigor with Maintenance staff.

Develop and present a Case Study to all employees in the applicable departments focusing on the Organizational shortfalls that led to injection of HPCS.

PREVIOUS OCCURRENCE EVALUATION No similar events have been reported by River Bend StAtion In the last three yeArs.

SAFETY SIGNIFICANCE

The RBS Updated Safety AnalysIs Report addresses an inadvertent Initiation of HPCS. The addition of cooler water to the upper plenum causes a reduction in steam flow which results in some depressurization as the pressure regulator ("RG")

responds to the event. In the automatic flow control mode, following a momentary decrease, neutron power settles out at a level slightly above operating level. In manual mode, the flux level settles out slightly below operating level. In either case, pressure and thermal variations are relatively small and 110 Significant consequences are experienced. The minimum critical power ratio remains within the safety limit and, therefore, fuel thermal margins are maintained.

The ECCS is deSigned, in conjunction with the primary and secondary containment, to limit the release of radioactive materials to the enVIronment following a OCA, The _CCS uses two independent methods (flooding and spraying) to cool the core during a LOCA. The ECCS network is composed of the HPCS System, the Low Pressure Core Spray (LPCS)

System, and the low pressure coolant injection (LPCI) mode of the Residual Heat Removal (RHR) System. The ECCS also consists of the Automatic Depressurization System (ADS), The suppressIOn pool provides the required source of water for tho ECCS, I\\lthough no crodit Is takon In tho safety analyses for tho condensate storage tank (CST), It is capable of provldtng a sOurce of water for the HPCS System, iAdequate core cooliny is ensured by the ol.H:Hability of tile radundant and ulverse low pressure ECCS lI)jecllon/spray subsystems in conjunction with the ADS, Also, the Reactor Core Isolation Cooling (RCIC) System will aulomatically provide Systom Will outomatlcally provldo makoup wol r at mosl roa clor oporatlng prossuros, LPCS, LPC\\, ADS, and RCIC wor~

oporahle for tho duration of tho evont.

IThis evont WRS of minim I signlficRnco to th hef\\lth nd sRfoty of the publtc du to Ihe RVRIIRbiitty of Rlternalo ECCS And tho nogllgiblo ffoct of an Inadvortent tntltalton of HPCS on roaetor safoty, 3

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(NOTE: Energy Industry Identification System component function identifier and system name of each component or system referred to in the LER are annotated as (**XX" ) and [XX). respectively.)

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