05000416/LER-2018-010-01, Reactor Manual Scram Due to Main Steam Bypass Stop and Control Valve Drifting Open

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Reactor Manual Scram Due to Main Steam Bypass Stop and Control Valve Drifting Open
ML19192A062
Person / Time
Site: Grand Gulf 
Issue date: 07/11/2019
From: Emily Larson
Entergy Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
GNR0-2019/00030 LER 2018-010-01
Download: ML19192A062 (6)
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LER-2018-010, Reactor Manual Scram Due to Main Steam Bypass Stop and Control Valve Drifting Open
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(iv)(B), System Actuation
4162018010R01 - NRC Website
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text

GNR0-2019/00030 July 11, 2019 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Entergy Operations, Inc.

P.O. Box756 Port Gibson, Mississippi 39150 Eric A. Larson Site Vice President Grand Gulf Nuclear Station Tel: 601-437-7500 10 CFR 50.73

SUBJECT:

Supplemental Licensee Event Report 2018-010-01, Reactor Manual SCRAM Due To Main Steam Bypass Stop and Control Valve Drifting Open

Dear Sir or Madam:

Grand Gulf Nuclear Station, Unit 1 NRC Docket No. 50-416 Renewed Facility Operating License No. NPF-29 Attached is Supplemental Licensee Event Report 2018-010-01, Reactor Manual SCRAM Due To Main Steam Bypass Stop and Control Valve Drifting Open. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A) for any event or condition that resulted in a manual or automatic actuation of systems listed in 10 CFR 50.73(a)(2)(iv)(B).

This letter contains no new commitments. If you have any questions or require additional information, please contact James Shaw at 601-437-2103.

Sincerely, Cat~-----

Eric A. Larson EAUram

Attachment:

Licensee Event Report 2018-010-01 (See Next Page)

GNR0-2019/00030 Page 2 of 2 cc:

NRG Region IV - Regional Administrator NRG Senior Resident Inspector, Grand Gulf Nuclear Station NRR Project Manager

GNR0-2019/00030 Attachment Licensee Event Report 2018-010-01

NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)

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

.Page Grand Gulf Nuclear Station, Unit 1 05000416 1 OF3

4. Title Reactor Manual SCRAM Due To Main Steam Bypass Stop and Control Valve A Drifting Open
5. Event Date
6. LER Number
7. Report Date
8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Number No.

Month Day Year NIA OSOOONIA 12 12 2018 2018 010

- 01 7

11 2019 Facility Name Docket Number NIA OSOOONIA

9. Operating Mode NIA NIA Nia

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

At approximately 1351 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.140555e-4 months <br /> on Wednesday, December 12, 2018, while operating in MODE 1 at approximately 100 percent power, the Grand Gulf Nuclear Station was manually shutdown in response to Main Steam Bypass Stop and Control Valve A drifting open. The Main Steam Line Isolation Valves were manually closed as a mitigating action to control reactor pressure vessel rate of depressurization and cooldown. During the scram recovery, the Reactor Core Isolation Cooling (RCIC) System injection was delayed. During preparation to initiate High Pressure Core Spray (HPCS) System the operator noted that RCIC had started to inject but due to the water level and the rate of change the operator started HPCS. HPCS was secured once water level was trending higher. RCIC was utilized for reactor water level control until RCIC was placed in standby at 1645 hours0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br />. There were no consequences to the general safety of the public, nuclear safety, industrial safety and radiological safety for this event.

The direct cause of the condition is a failed linear variable differential transformer (L VDT) in the actuator for the Main Steam Bypass Stop and Control Valve A The cause of the event was the existing operating guidance for the turbine electro hydraulic control (EHC) did not provide procedural steps to manually swap from a faulty controller to an auxiliary controller, which would have allowed the operators to close the valve. Corrective actions included swapping wiring from the failed LVDT to an installed spare L VDT and enhancement of the procedural guidance to ensure operators have the tools to manually swap from a faulty controller to an auxiliary controller. This report is made pursuant to 10 CFR 50.73(a)(2)(iv)(A) for any event or condition that resulted in manual or automatic actuation of systems as listed in 10 CFR50.73(a)(2)(iv)(B), specifically the Reactor Protection System, HPCS, and RCIC systems were actuated.

NRC FORM 366 (04-2018) (04-2018)

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

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readinq-rm/doc-collections/nureqs/staff/sr1022/r3L)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LEA NUMBER YEAR Grand Gulf Nuclear Station, Unit 1 05000-416 2018 A. PLANT CONDITIONS PRIOR TO THE EVENT SEQUENTIAL NUMBER
- 010 REV NO.
- 01 Grand Gulf Nuclear Station (GGNS) Unit 1 was operating at approximately 100 percent power in Mode 1. There were

_no Structures, Systems, or Components that were inoperable that contributed to this event.

B. DESCRIPTION

At approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> CDT on Wednesday, December 12, 2018 while operating in MODE 1 at approximately 100 percent power the GGNS,Main Steam Bypass Stop and Control Valve A [JI] begandrifting open. The valve began to modulate between 0-1 O percent open over the course of 90 minutes. After 90 minutes, the valve began to open at an increased rate, reaching approximately 50 percent open. The reactor was manually scrammed at 1351 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.140555e-4 months <br />. The Main Steam Line Isolation Valves [SB] were manually closed as a mitigating action to control reactor pressure vessel rate of depressurization and cooldown. Reactor pressure was controlled through the use of the Safety/Relief Valves [SB] and ultimately the Reactor Core Isolation Cooling (RCIC) System [BN].

During the scram recovery, at 1358 hours0.0157 days <br />0.377 hours <br />0.00225 weeks <br />5.16719e-4 months <br /> the operator proceeded into the steps for a controlled start of RCIC. The expected RCIC injection response was delayed due to discharge pressure indication and governor valve light indications were not as expected. Therefore, the operator prepared to initiate the High Pressure Core Spray (HPCS)

System [BG] based on current reactor water level and its trend.

During preparation to initiate HPCS, the operator noted that RCIC had started to inject but reactor level was in the low end of the desired control band at -24.8 inches Wide Range (WR) with a downward trend and current RCIC injection was not arresting the decreasing trend in a timely manner. After evaluating the reactor water level and rate of change, the operator completed manually starting HPCS injection at 1408 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.35744e-4 months <br />. At 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br />, the HPCS injection was secured with reactor water level at 7.4 inches WR and trending higher and RCIC still injecting. RCIC and Safety/Relief Valve$ were utilized for reactor water level control until RCIC was placed in standby at 1645 hours0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br />.

C. REPORT ABILITY This event was reported under 1 OCFR50.72(b )(2)(iv)(A) and 10CFR50.72(b)(2)(iv)(B) for any event that results in the Emergency Core Cooling System discharge to the Reactor Coolant System, actuation of the Reactor Protection System while the reactor is critical, and under 1 OCFR50.72(b)(3)(iv)(A) for any specified system actuation (HPCS and RCIC) in Emergency Notification System (ENS) Notification 53788.

This report is made pursuant to 10CFR50.73(a)(2)(iv)(A) for any event or condition that resulted in manual or automatic actuation of systems as listed in 10CFR50.73(a)(2)(iv)(B), specifically the reactor protection system, HPCS, and RCIC systems were actuated.

D. CAUSE

The direct cause of the condition is a failed linear variable differential transformer (L VDT) in the actuator for the Main Steam Bypass Stop and Control Valve A. Page 2 of 3 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2018)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3[)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER YEAR Grand Gulf Nuclear Station, Unit 1 05000-416 2018 SEQUENTIAL NUMBER
- 010 REV NO.
- 01 The Hoot Cause of the event is the existing operating guidance for Turbine EHC did not provide procedural steps to manually swap from a faulty controller to an auxiliary controller, which would have allowed the operators to close the Main Steam Bypass Stop and Control Valve A.

E. CORRECTIVE ACTIONS

The following corrective actions are completed.

Completed:

The wiring from the failed LVDT on the Main Steam Bypass Stop and Control Valve A was removed and reconnected to an installed spare LVDT, valve control was retested, and the valve returned to service.

Operating instruction (ONEP-05-1-02-V-1) was updated with guidance to manually swap bypass control valve control to the auxiliary controller which will drive the valve to its proper position should a similar issue occur and the automatic transfer to the auxiliary controller not occur.

F. SAFETY SIGNIFICANCE

The manual Reactor SCRAM and manual closure of the MSIVs did not result in actual consequences to safety of the general public, nuclear safety, industrial safety or radiological safety.

If manual operation of the Safety/Relief Valves (SRVs) was not performed following this event, the potential consequence to safety of the general public, nuclear safety, industrial safety and radiological safety would have been mitigated by automatic operation of the SRVs to control Reactor pressure.

Based on the above, the safety significance of this event is determined to be low. The response to the manual scram was performed in accordance with plant procedures. Plant parameters (reactor level, pressure) were maintained within procedure and safety limits. There were no actual nuclear safety consequences or radiological consequences during the event.

G. PREVIOUSLY SIMILAR EVENTS Entergy conducted a three-year review of the relevant licensee event reports and determined that there were no similar events. Page 3 of 3

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