05000247/LER-2018-003-01, Loss of Safety Function Due to Valve SWN-6 Actuator Failure During Service Water Header Swap

Loss of Safety Function Due to Valve SWN-6 Actuator Failure During Service Water Header Swap

ML20050C993
Person / Time
Site:	Indian Point
Issue date:	02/07/2020
From:	Vitale A Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-20-011 LER 2018-003-01
Download: ML20050C993 (7)

LER-2018-003, Loss of Safety Function Due to Valve SWN-6 Actuator Failure During Service Water Header Swap

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 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
2472018003R01 - NRC Website

text

NL-20-011 February 7, 2020 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Entergy Nuclear Operations, Inc, Indian Point Energy Center 450 Broadway, GSB P.O. Box249 Buchanan, NY 10511-0249 Tel (914) 254-6700 Anthony J. Vitale Site Vice President 10 CFR 50.73(a)(1)

• ,. $ubject:

Licensee Event Report 20.18-003-01, "Loss of. Safety Function due to Valve SWN~6 Actuator Failure During Service Water Header Swap" Indian Point Unit No. 2.. :

• N RC Docket No. 50-24 7..

Renewed Facility Operating License No. DPR-26

Reference:

Entergy N.uclear Operations, Inc. lett~r to U.S. Nuclear Regulatory Commission, "Li.censee Event Report# 2018-003-00, 'Loss of Safety Function Due to Valve SWN~6 Actuator Failure During Service Water Header Swap,' Indian Point Nucl~ar Generating Unit 2, Docket No. 50-247, DPR-26" (Letter No. NL-18-084)

(ADAMS Accession No. ML 18361566), dated pe6ember 20, 2018 In accordance with Title 1 O of the Code of Federal Regulations (1 O CFR) 50.73(a)(1 ), Entergy Nuclear Operations, Inc. (Entergy) hereby provides Licensee Event Report (LER) 2018-003-01.

The attached LER is a revision to LER 2018-003-00 (Reference) that reported an event where there was a loss of safety function due to valve SWN-6 actuator failure during an Essential Service Water header swap, thus affecting the capability of the Service Water System (SWS) to remove residual heat and/or to mitigate the consequences of an accident. The event was reportable under 1 O CFR 50.73(a)(2)(v)(B) and 1 O CFR 50.73(a)(2)(v)(D). The safety function was restored after replacement of the failed roll/shear pin and SWN-6 could be closed within the allowed outage time of Technical Specification Limiting Condition of Operation 3.0.3. The reactor remained at 100 percent power during the event. This event was recorded in the Entergy Corrective Action Program as Condition Report CR-IP2-2018-05922; The attached LER revision updates the root cause evaluation of this event, and includes conforming editorial changes.

/'

NL-20-011 Page 2 of 2 There are no commitments made or revised in this letter. If. you have any questions or require additional information, please contact Ms. Mahvash Mirzai, Manager, Regulatory Assurance, at 914-254-7714.

Sincerely, Anthony J. Vitale AJV/cdm/sp

Attachment:

Indian Point Unit 2 Licensee Event Report 2018-003-01 cc:

Regional Administrator, NRG Region I NRG Senior Resident Inspector, Indian Point Energy Center NRG Senior Project Manager, NRG NRR DORL New York State (NYS) Public Service Commission

Attachment NL-20-011 Indian Point Unit 2 Licensee Event Report 2018-003-01 (4 pages)

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

, the NRG may not conduct or sponsor, and a nerson is not reauired to resoond to the information collection.

1. Facility Name

~- Docket Number

. Page Indian Point Unit 2 05000-247 1 OF4

4. Title Loss of Safety Function Due to Valve SWN-6 Actuator Failure During Service Water Header Swap

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved Sequential Rev Facility Name Docket Number M'onth Day Yeai Year Month Day Year Number No.

05000 10 28 2018 2018

- 003

- 01 02 07 2020 Facility Name Docket Number 05000

9. Operating Mode

~bstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)

On October 28, 2018, Operations personnel were unable to fully close valve SWN-6 causing the Service Water System to be declared inoperable, and as a result, Operations entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3~0.3.

This event occurred on October 28, 2018 at approximately 0930 Eastern Time with Unit 2 on-line at 100 percent power (Mode 1) and was identified by Operations personnel during a scheduled Essential Service Water header swap. TS LCO 3.0.3 was entered for a unit shutdown since the Service Water System (SWS) TS LCO 3:7.8 was not met during the header swap as the result of valve SWN-6 (Service Water 4-5-6 Header Supply to Turbine Building Oil Coolers) not stroking full closed. Valve SWN-7 (Service Water 1-2-3 Header Supply to Turbine Building Oil Coolers) had been successfully stroked full open as required.

Immediate removal of the valve SWN-6 actuator cover plate identified the worm gear roll/shear pin to be broken, which was the direct cause. The pin was replaced, allowing the valve to be cycled full closed and TS LCO 3.0.3 to be exited. A loss of SWS safety function was declared. This required an 8-hour report per 10 CFR 50. 72(b)(3}(v}(B} and 10 CFR 50.72(b}(3}(v)(D). The root cause remains indeterminate due to the roll/shear pin being misplaced and lost and no interior valve inspection, but three possible causes have been identified: backed out roll/shear pin, binding in components, or inadequate preventive maintenance frequency.

There were no radiological or industrial safety impacts. The event had no effect on public health and safety. There were no human performance contributors to the event.

NRG FORM 366 (04-2018)

Note: The Entergy Industry Identification System Codes are identified within brackets { }.

DESCRIPTION OF EVENT

On October 28, 2018 at approximately 0930 Eastern Time, while Operations was swapping Essential Service Water {Bl} headers in accordance with (IAW) the Service Water System (SWS) Operation Procedure. The valve actuator {HCO} handwheel. for valve SWN-6 {ISV}, "Oil Coolers {CLR} Supply from Header 4-5-6 Stop" started freewheeling when attempting to close the valve at approximately the 85 percent open (15 percent closed) position.

The operator stated that the valve started to bind up while closing when approximately 15 percent closed. The operator then reopened the valve in an attempt to free up the actuator mechanism. A second attempt was then made by the operator to close the valve, but it bound up again at 15 percent closed position,* at which time the handwheel began to spin freely on the way open agah The operator promptly notified the Operations Field Support Supervisor-(FSS) that the valve wasinopera.ble, which was cohfir111ed by the FSS~

Pe~ Technical Specifications (T$)Elases section 3;7,6, the Service Water System {Bl, KG} prqvides a heat sink for the removal of process and Operating heat from safety related components during a Design Basis Accident (OBA) or transient. The function of valve SWN-6 is to isolate the SWS 4-5-6 header when needed via operator manual

• action to position the valve in the full closed position. Based on SWN-6 failing in the open position, the Service Wat.er Non-Essential isolation could not be established rendering the Non-Essential Service Water System {KG}

inoperable and TS LCO 3.0.3 (7 hour8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> shutdown) was entered. In addition, with SWN-6 open, in the event of an acQidentand a loss of offsite power, water could be diverted from the essential header to the non~essential header

• . (through the open SWN-6 valve) which may result in the essential header riot having sufficient floW. These conditions constituted a loss of safety function as this condition could have prevented the fulfillment of the SWS safety function that was needed to remove residual ~eat and required ari 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report IAW 1 O CFR

• 50.72(b}(3}(v)(B). This event was also reported under 1 O CFR 50.72(b)(3)(v)(D) for a condition that could have prevented the fulfillment of the safety function of the SWS that was needed to mitigate the consequences of an accident.

Due to the valve SWN-6 handwheel free-spinning, Operations removed the actuator cover from the actuator. It was determined that the cause of valve SWN-6 not closing was a broken roll/shear pin which disengaged the

• handwheel shaft from the worm gear {GR}. Maintenance installed a new roll/shear pin and replaced the grease in the actuator. The Essential Service Water header swap to the 4-5-6 header was then completed successfully and TS LCO 3.0.3 was exited. This. event was recorded in the Indian Point Energy Center (IPEC) Corrective Action Program as Condition Report CR-IP2-2018-05922.

There were no human performance issues encountered during the valve manipulation. However, the broken roll/shear pin was misplaced sometime after the actuator cover was removed and a condition report was initiated to document loss of the affected part(s).

CAUSE OF EVENT

The direct cause was failure of the valve SWN-6 actuator's roll/shear pin. The root cause of the pin failure remains indeterminate. Page 2 of 4 (04-2018)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

, the NRC may not conduct or hHp:fAWAW.nre..oovlrearnng-mll'doc~:slaff!sr1022/r3f) sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME

2. DOCKETNUMBER

3. L.ERNUMBER Indian Point Unit 2 05000-247 YEAR SEQUENTIAL NUMBER REV NO.

2018

- 003

- 01 Root Cause:

The ultimate root cause of the valve SWN-6 actuator roll/shear pin failure is unknown/ indeterminate at this time since the broken roll/shear pin parts had been misplaced and there has been no outage of sufficient duration to fully inspect the valve interior.

Possible causes include:

• The roll/shear pin backed out of the worm gear resulting in impact on the ~egment gear that caused shear or resulting in fatigue over time that caused shear.

Resistance due to binding in actuator/valve components overstressed the roll/shear pin which broke in place as designed.

The preventive maintenanc::efrequency allowed degradation of the valve.. intemals due to the harsh.

• environment resulting in excessive force being required for operation leading to pin failure (ncite the extent

• • of condition identified no other issues).

CORRECTIVE ACTIONS

Immediate/Interim/Mitigating Actions:

1.

A.hew roll/shear pin was installed in the actuator worm gear, grease was changed out, and valve SWN-6 was able to be stroked smoothly to the required closed position. Valve SWN-6 has a required safety related function to be closed.during a loss-of-coolant accident (LOCA) for post-accident cooling, but has no safety functions requiring it to be opened. SWN-6 was able to be closed upon replacerrient of the roll/shear pin and was put into its safety related closed position as was required after the header swap.

EVENT ANALYSIS

During the performance of Service Water Essential Header swap, the SWN-6 (supply to Turbine Building {TB} Oil Coolers {CLR}) valve stem became disconnected from its gear box at 85 percent open and could not be operated.

Therefore, the Service Water System was inoperable. If an accident occurred and off site power was lost, the system design is to direct flow to the essential service water header. With valve SWN-6 open, flow could be diverted to the non-essential header (non-essential pumps are not powered), and insufficient flow may have been provided to the essential header. TS LCO 3.0.3 was entered at 0930 Eastern time on 10/28/2018 with the required actions to be in Mode 3 in 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, Mode 4 in 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and Mode 5 in 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. Repair efforts were successful at shutting SWN-6, and LCO 3.0.3 was exited at 1305 Eastern time on 10/28/2018 before operators normally added any negative reactivity in support of shutdown.

The condition constitutecj a loss of safety function which required an 8-hour report IAW 10 CFR 50.72(b)(3)(v)(B) for an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. The event was also reported under 10 CFR 50.72(b)(3)(v)(D) for an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. Page 3 of 4 (04-2018)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 4-d?'"

LICENSEE EVENT REPORT {LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this fonn hllp://www.mc.gov/reajnq-rm/cloc-co!leclioosfnuregsfslaWsr1<YZ2/r3f)

, the NRG may not conduct or spon.sor, and a person is not required to respond to, the information collection.

3. LEA NUMBER YEAR Indian Point Unit 2 05000-247 2018 EXTENT OF CONDITION REVIEW SEQUENTIAL NUMBER

- 003 REV NO.

- 01 The valves determined to be susceptible to the extent of condition review are Unit 2: SWN-4, SWN-5, SWN-7, FCV-1111, FCV-1112, SWN-29, SWN-30, SWN-31, SWN-32, SWN-35, SWN-35-1, SWN-38, and SWN-39. These valves were specifically chosen based on their risk significance (active safety functions) and due to being equipped with Fisher Controls M-series manual gear actuators. As stated, these gear actuators contain a roll/shear pin where failure of this single pin results in the valve being inoperable.

It was confirmed that the Unit 3 actuators {HCO} utilize Jamesbury manual gear actuators that utilize 2 set screws (in lieu of a single roll/shear pin) to secure the shaft to the worm gear. This different design is inherently much less susceptible to failure thus excludes U3 from further EOC review.

To ensure the EOC is captured; CRs werE3_ generated to replace the potentially affected Unit 2. actuators. ar,d as an interim* action, to perform an inspection of the currently installed gearboxes.

PAST SIMILAR EVENTS Internal Events A historical review of the Paperless Condition Reporting System (PCRS) Database of applicable condition reports (CRs) using a key word search-of "SWNlland "shear pin" yielded 23 CRs with a date range of January 2004 to December.4, 2018. A review was performed, but was limited to. Fisher Controls M-series manual gear actuators (like-in-kind) in the Unit 2 and Uriit 3 Service Water Systems that have an active safety-related function and are regularly exercised by Operations. This* population was further reduced by investigating the PM history of the *

• susceptible va.lves listed in the EOC review (SWN-4, SWN~s. SWN-7, FCV-1111, FCV-1112, SWN-29, SWN-30, SWN-31, SWN-32, SWN-35, SWN-35-1, SWN-38, and SWN-39).

External Events A search of significant OEs was performed. The search was performed on database for Institute of Nuclear Power Operators (INPO) and the Nuclear Regulatory Commission (NRC) (e.g., IERs L 1 L2, SOERs, SERs, INs, Gls, RIS, NRC Bulletins, etc.). Key word searches included broken shear pin, Fisher Controls 9500 butterfly valve, valve gearbox, and manual gearbox. The search yielded 56 reports of which 11 appeared applicable. Through a collegial review by engineering and maintenance root cause team members, three of the 11 OE reports were determined to be applicable significant OEs. The OE reports were regarding Vogtle Unit 1, Waterford Unit 3 and Oconee Unit 2.

SAFETY SIGNIFICANCE

This event had no effect on the health and safety of the public. There were no actual safety consequences for the event because Operations personnel were able to close valve SWN-6 within the allowed outage time (AOT) of TS LCO 3.0.3. The increase in plant risk was minimal (i.e., non-risk significant). A quantitative assessment of risk was performed and it was determined that the increase in Core Damage Frequency (CDF) was 4.11 E-07 and an increase in Large Early Release Frequency (LERF) of 1.80E-10 (reference Root Cause Evaluation associated with Condition Report CR-IP2-2018-05922 for the subject event), both of which are below the screening criteria of 1.0E-6 and 1.0E-7, respectively, for risk significance per Regulatory Guide 1.174. Page 4 of 4