05000416/LER-2018-003, Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests Due to Use of a Test Box

Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests Due to Use of a Test Box

ML18117A482
Person / Time
Site:	Grand Gulf
Issue date:	04/27/2018
From:	Emily Larson Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GNR0-2018/00023 LER 2018-003-00
Download: ML18117A482 (8)

LER-2018-003, Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests Due to Use of a Test Box

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 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)(iv)(A), System Actuation 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)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
4162018003R00 - NRC Website

text

~~Entergy GNR0-2018/00023 April 27, 2018 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Entergy Operations, Inc.

P. 0. Box 756 Port Gibson, MS 39150 Eric A. Larson Site Vice President Grand *Gulf Nuclear Station Tel. (601) 437-7500 10CFR5q.73

SUBJECT:

Licensee Event Report 2018-003-00, Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests due to Use of a Test Box Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 License No. NPF-29

Dear Sir or Madam:

Attached is Licensee Event Report 2018-003-00, Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests due to Use of a Test Box. This report is being submitted in accordance with 1 OCFR50. 73(a)(2)(v)(A) as an event or condition that could have prevented the fulfillment of the safety function.

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

Sincerely,

£a;{_

Eric A. Larson Site Vice President Grand Gulf Nuclear Station EAL/tdf

Attachment:

Licensee Event Report 2018-003-00 cc: (see next page)

GNR0-2018/00023 Page 2 of 2 cc: with Attachment U.S. Nuclear Regulatory Commission ATTN: Mr. Siva Lingam Mail Stop OWFN 8 81 Rockville, MD 20852-2738 NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150 U. S. Nuclear Regulatory Commission A TIN: Mr. Kriss Kennedy, NRR/DORL (w/2)

Mail Stop OWFN 881 Washington, DC 20555-0001

/

Attachment Licensee Event Report (LER) 2018-003-00

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017)

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13. PAGE Granc:!'Gulf Nuciear Station, Unit 1 05000 416 1 OF5

4. TITLE Inoperable Reactor Protection Functions During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests due to Use of a Test Box

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 05000 N/A 3

6 2018 2018-003-00 4

FACILITY NAME DOCKET NUMBER 27 2018 NIA 05000 NIA

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENlS OF 10 CFR §: (Check all that apply)

9. OPERATING MODE D 20.2201(b)

D 20.2203(a)(3)(i+*)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201(d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 1 D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1 )(i)(A)

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

D 20.2203(a)(2)(ii)

D 50.36(c)(1)(ii)(A) 181 50.73(a)(2)(v)(A)

D 73.71(a)(4)

10. POWER LEVEL D 20.2203(a)(2}(iii)

D 50.36(c)(2)

D 50.73(a)(2)(v)(B)

D 73.71(a)(5)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

D 50.73(a)(2)(v)(C)

D 73.77(a)(1) 78%

D 20.2203(a)(2)(v)

D 50. 73(a)(2)(i)(A)

[81 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i)

D 20.2203(a)(2)(vi)

D 50. 73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

.Q.50.73(a)(2)(i)(C)

Q.OTHER

. Specify. in Abstract below or in A. PLANT CONDITIONS PRIOR TO THE EVENT On March 6, 2018, Grand Gulf was operating in Mode 1 at 78% Power. There were no structures, systems, or components that were inoperable at the start of this event that contributed to this event.

B. DESCRIPTION

On March 6, 2018, engineering personnel identified that the use of the Reactor Protection System (RPS) [EIIS: JC] test fixture as implemented in some surveillance test procedures could result in the loss of two RPS reactor scram safety functions. Use of the test fixture in surveillance test procedures unintentionally resulted in the loss of Technical Specification (TS) Table 3.3.1.1 Function 6, Main Steam Isolation Valve-Closure, and Function 9, Turbine Stop Valve Closure (Trip Oil Pressure -Low), as defined in the TS bases. The TS bases state a scram will occur on isolation of at least one main steam isolation valve (MSIV) [EIIS: SB][ISV] in three of four main steam lines (MSLs), and on* closure of three of four turbine stop valves (TSV) [El IS: TA][ISV]. A review determined that iso_lation of three of four MSLs, or closure of three of four TSVs, would not necessarily have resulted in a full Scram while the test fixture was in use.

The test box was designed to reduce unnecessary RPS actuations. The test box consists of a S-ohm resistor in parallel with a 5 VAC lamp terminated with banana jacks. The RPS test box establishes a low resistance path in parallel with the trip logic relay contacts.

The RPS has two independent trip systems (A and B) with two trip logics (i.e., trip divisions) in each trip system: A and C trip logics for Trip System A, and Band D trip logics for Trip System B.

For Function 6 (MSIV Closure), which uses pressure transmitters and trip units to detect changes in hydraulic pressure, there are sixteen total instrument channels. (two per MSIV) with each logic division having four instrument channels and each trip system having eight. The logic used ensures a full reactor scram occurs for the condition where at least one MSIV in three or more MSLs are less than 90% open. This occurs as the logic uses vaives in A and C MSLs for Division A trip logic, A and B MSLs for the Division B trip logic, Band D MSLs for the Division C trip logic, and C and D MSLs for the Division D trip logic. By varying the order in which the auxiliary relay contacts are paralleled within each RPS trip logic it can be assured that a half Scram will occur in each trip system even if all the MSL switches on any one MSL fail. *similarly, the TSV logic has eight instrument channels with -the same alternating logic for the four TSVs.

The use of the RPS test box, as implemented in the procedures, would bypass MSL valve position signal inputs for two MSLs (i.e., bypass four instrument channels) and prevent the associated trip logic from being in a tripped condition (i.e., half-scram). This prevents the associated trip system

• from generating a half-scram when two of three isolated MSLs are !n the bypassed division and, while a valid Group 1 isolation (closure of all four MSLs) would still result in a full scram, a scram would not occur in two of four possible MSL isolation scenarios involving just three MSLs, as required by the TS bases.

For Function 9 (TSV Closure), the logic used ensures a full reactor scram occurs for the condition where three or more TSVs are less than full open. Each trips stem monitors trip fluid ressure Page 2 of 5 APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (4-2017)

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/r3D

1. FACILITY NAME

2. DOCKET

, 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 SEQUENTIAL NUMBER REV.

NO.

2018-003-00 for all four TSVs, and the use of the RPS test box would bypass the pressure transmitter inputs for two of the TSVs. This prevents the associated trip system from generating a half-scram when two of the three closed TSVs are in the bypassed division, and_ while a turbine trip (closure of all four TSVs) would still result in a full scram, a scram would not occur in two of four possible TSV closure scenarios involving just three TSVs as required by the TS bases.

Use of the test box was added to the Function 6 (MSIV) test procedures on May 5, 2016, and added to the Function 9 (TSV) procedures on June 6, 2016. The MSIV Closure procedure was performed six times with the test box and each TSV Closure procedure was performed six times.

The longest time the test box was installed during the surveillances was 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and 32 minutes for the Function 6 and 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 48 minutes for Function 9.

With one trip trip logic bypassed and Function 6 inoperable, Technical Specific_ation 3.3.1.1 Required Action G requires restoring RPS trip capability or being in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. TS 3.3.1.1 Condition G was not intentionally entered during the performance of the surveillance but was met each time.

With one trip logic bypassed and Function 9 inoperable, Technical Specification 3.3.1.1 Conditions C and E requires restoring RPS trip capability within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or reducing power to less than 35.4%

reactor thermal power within the following 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. TS 3.3.1.1 Condition E was not intentionally entered during the performance of the surveillance but was met each time with one exception. On January 4, 2017, Function 9 was in a bypassed condition for 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 48 minutes, however GGNS was in Mode 4 at the time and operability was not required.

C. REPORTABILITY

This event is being reported under 1 OCFR50.73(a)(2)(v)(A) and 50.73(a)(2)(v)(D) as an event that that could have prevented the fulfillment of the safety function of structures or systems that are needed to (A) shut down the reactor and maintain it in a safe shutdown condition and (D) mitigate the consequences of an accident.

D. CAUSE

The direct cause of this event was inadequate procedure revision. Th.e cause of the inadequate /

procedure revision was.an inadequate 1 OCFR50.59 screening of the associated design change due to inadequate risk recognition and inadequate technical rigor.

The activity description in the process applicability determination was not clear, and the risk was not recognized. The TS bases were reviewed as part of the applicability determination but the impact of the change on the bases was not recognized.

NRG FORM

.(4-2017) 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT {LER)

CONTINUATION SHEET (See NU REG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readinq-rm/doc-collections/nuregs/staff/sr1022/r3D

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

1. FACILiTY NAME

2. DOCKET Grand Gulf Nuclear Station, Unit 1 05000 416

E. CORRECTIVE ACTIONS

The following actions are completed or planned.

Completed:

YEAR

3. LER NUMBER SEQUENTIAL NUMBER 2018-003-00 Revised MSIV Closure surveillance procedures to remove the use of RPS Test Box Revised TSV Closure surveillance procedures to remove the use of RPS Test Box.

Conduct training for 50.59 evaluators using industry experts as instructors to increase evaluator knowledge of changes with respect to NEI 96-07 and current industry experience on 50.59 evaluations.

Review a sample of 50.59 Evaluations performed within the past three years to verify technically correct justifications Review a sample of process applicability determinations performed within the past tt;lree years to confirm those changes screened out Review a sample of process applicability determinations performed within the past three years to verify engineering changes were screened to the correct program Utilize industry 50.59 experts for independent third party reviews of 59.59 evaluations.

Planned actions included in the corrective action program which may be changed in accordance with the program Review this event with engineering personnel and coach on the need for technical rigor and risk recognition F.

SAFETY SIGNIFICANCE

Function 6 had one division bypassed for a total of 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> and 46 minutes over the 20 month period. While Function 6 did not meet the bases requirement for operability while bypassed, RPS remained functional and would have initiated a scram on a Group 1 M$1V isolation (isolation of all four MSLs). In addition,- GGNS credits Function 2.b, Fixed Neutron Flux - High, with generating a scram in the overpressurization analysis rather than a direct scram from MSIV closure, and reload analyses show that MSIV closure is not an otherwise limiting event.

Function 9 had one division bypassed for a total of 69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br /> and 54 minutes over the 20 month period. Regarding Function 9, the TSV scram is credited in the Turbine Trip with no bypass analysis, which is a limiting event. While the TSV scram did not meet the bases requirement for operability while bypassed, RPS remained functional and would have initiated a scram upon a turbine trip and TSV closure: In addition, the turbine control valves (TCVs) [EIIS: TA][FCV] are operated by follow-up pistons which receive fluid from the TSV trip system. In the event that RPS failed to respond t9 the TSV closure, Function 10, TCV Fast Closure, Trip Oil Pressure-Low, would initiate a reactor scram based on pressure loss in the system. Plant data indicates the TCV scram would occur within 0.1 seconds of TSV scram failure.

MSIV closure, TSV closure, and TCV valve fast closure are all anticipatory trips for reactor vessel over ressure transients, and scram earlier than either the neutron monitorin s stem or nuclear Page 4 of 5 REV.

NO. APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 (4-2017)

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/nuregs/staff/sr1022/r3l)

1. FACILITY NAME

2. DOCKET

, 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 SEQUENTIAL NUMBER REV.

NO.

2018-003-00 system high pressure. The nuclear system high-pressure scram provides diversity of trip initiation and, in conjunction with the pressure-relief system, is adequate to preclude overpressurizing the nuclear system. RPS safety function was maintained at all times and there was no significant impact to health and safety of the public. Based on this, this condition will not be counted as a safety system functional failure against Performance Indicator MSOS, Safety System Functional Failures.

G. PREVIOUS SIMILAR OCCURRENCES No previous similar. events could be found.

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