05000390/LER-2017-005

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LER-2017-005, Isolation of the 1 B-B Safety Injection Pump Leads to Condition Prohibited by Technical Specifications
Watts Bar Nuclear Plant, Unit 1
Event date: 05-10-2017
Report date: 07-10-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
3902017005R00 - NRC Website
LER 17-005-00 for Watts Bar re Isolation of the 1B-B Safety Injection Pump Leads to a Condition Prohibited by Technical Specifications
ML17191A430
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 07/10/2017
From: Simmons P
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML17191A430 (7)


comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

I. PLANT OPERATING CONDITIONS BEFORE THE EVENT

Watts Bar Nuclear Plant (WBN) Unit 1 was at 46 percent rated thermal power (RTP) .

II. DESCRIPTION OF EVENT

A. Event Summary operations personnel discovered the 1B-B Safety Injection (SI) {EllS:BQ} pump discharge isolation valve {EIIS:V}(1-ISV-63-527) closed. Technical Specification (TS) 3.5.2, ECCS - Operating, Condition A was immediately entered for one or more trains of the Emergency Core Cooling System (ECCS) inoperable. TS 3.5.2 Condition A was exited at 0913 EDT when 1-ISV-63-527 was opened. Investigation determined that the 1B-B SI pump discharge isolation valve had been closed since prior to Unit 1 entering Mode 3 on April 26, 2017, representing a condition prohibited by TS. During this time period, the 1A-A SI pump was inoperable for 21 minutes, representing a loss of safety function.

This event is being reported to the Nuclear Regulatory Commission (NRC) under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS and under 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented fulfillment of a safety function.

B. Inoperable Structures, Components, or Systems that Contributed to the Event No inoperable equipment contributed to this event.

C. Dates and Approximate Times of Occurrences Date Time Event (EDT) 4/11/2017 Preparations occur to perform 0-SI-82-4, 1B EDG Blackout Test, with Unit 1 in Mode 6. To prevent injection of water into the reactor coolant system, the SI pump discharge isolation valve was closed.

4/26/2017 1624 Unit 1 enters Mode 3 5/9/2017 1240 1A-A Emergency Diesel Generator (EDG) declared inoperable to check water in cylinders.

5/9/2017 1301 1A-A EDG declared operable.

5/10/2017 0907 1 B-B SI pump discharge isolation valve found closed, pump declared inoperable.

5/10/2017 0913 1B-B SI pump discharge isolation valve opened, pump declared operable.

D. Manufacturer and Model Number of Components that Failed During the Event Not applicable.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER

2017 - 00 005

E. Other Systems or Secondary Functions Affected

No other systems or secondary functions were affected .

F. Method of discovery of each Component or System Failure or Procedural Error This valve misposition was discovered by an operator performing routine operator rounds.

G. Failure Mode and Effect of Each Failed Component Not applicable.

H. Operator Actions

Upon discovering valve 1-ISV-63-527 isolated, the operator promptly opened the valve.

I. Automatically and Manually Initiated Safety System Responses Not applicable.

III. CAUSE OF THE EVENT

A. The cause of each component or system failure or personnel error, if known.

The test director for the EDG Blackout Test failed to follow procedure use and adherence requirements related to the application of Not Applicable (N/A), and did not obtain Section Manager concurrence for the use of N/A.

B. The cause(s) and circumstances for each human performance related root cause.

The test director for the EDG Blackout Test failed to follow procedure use and adherence requirements related to the application of Not Applicable (N/A), and did not obtain Section Manager concurrence for the use of N/A.

IV. ANALYSIS OF THE EVENT

On April 11, 2017, WBN Unit 1 was in Mode 6 during the Unit 1 fourteenth refueling outage (U1R14). The station was making preparations to perform 0-S1-82-4, 1B EDG Blackout Test. Blackout testing is normally conducted with the unit in Mode 5, however, due to a delay in the U1R14 schedule, the decision was made to conduct the testing in Mode 6. O-S1-82-4 Appendix B aligns the SI System for the blackout testing to ensure that water is not inadvertently injected into the core. Section 3.1 of Appendix B accomplishes this task by ensuring that the Cold Overpressure Mitigation System (COMS) clearance is in place. Normally, a COMS clearance places a hold order on the breakers and hand switches of the system pumps with the capability to inject high pressure water into the core. Appendix B, Section 3.1, Step [2] assumes this clearance for COMS is in place. Appendix B, Section 3.1, Step [3] takes the additional step of ensuring that the 1B-B SI Pump discharge valve (1-ISV-63-527-B) is closed and tagged. This is accomplished by used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER

2017 - 00 005 verifying that the COMS clearance in Step [2] already holds 1-ISV-63-527-B closed and tagged or that the clearance is modified to include this valve.

0-S1-82-4 is written with the assumption that the unit will be in Mode 5 during the performance of the surveillance. An appendix to the procedure restores system alignment following conduct of the testing.

That appendix does not contain restoration steps for 1-ISV-63-527-B because the procedure assumes configuration control for this valve is maintained under the COMS clearance. The surveillance essentially transfers responsibility for configuration control to the COMS clearance, which was not required in this case due to the test being performed in Mode 6. This lack of configuration control in 0-S1-82-4 was a latent error introduced in the procedure in 2004.

The test director recognized that the unit was in Mode 6 and that the COMS clearance was neither required nor hanging at the time of the test. 0-S1-82-4 Appendix B, Section 3.1, Step [2] and [3] were marked N/A during the preparation. Step [2] is marked with a note that states "COMS not required in Mode 6". Step [3] is marked with a note that states "Valve verified closed but not tagged. Mode 6 does not require valve to be tagged for COMS". The test director failed to follow procedure use and adherence requirements. Specifically, the Section Manager concurrence was not obtained prior to moving to the next step in the procedure. Additionally, the test director did not consider the effect of N/A on these steps with regard to configuration control. The system restoration appendix was not reviewed to ensure adequate restoration steps were in place to restore 1-ISV-63-527-B to its required open position for normal operation.

Contributing to the event, while not required, performance of an 18 month locked valve verification and a system alignment verification were waived during the outage.

V. ASSESSMENT OF SAFETY CONSEQUENCES

Both trains of SI were required to be in service to comply with TS 3.5.2 following re-entry into Mode 3 on April 26, 2017. During the time until the valve misposition was identified on May 10, 2017, the 1A-A SI was operable except for a 21 minute period when its associated EDG was inoperable while it was checked to confirm water was not present in the engine cylinders. Therefore, during this 21 minute period, both SI trains were considered inoperable. An evaluation concluded the change in core damage probability from the 1 B-B SI pump being isolated for 14 days considering the brief period where the 1A-A SI pump was also unavailable, was less than 1E-7 during this time period, and the risk significance of this event was very small.

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The 1A-A SI pump was operable during the period in question except for a 21 minute period.

B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident Not applicable.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service The isolated 1B-B SI pump was returned to service seven minutes after discovery. The 1B-B SI pump was out of service from April 26, 2017 until May 10, 2017, or just over fourteen days.

VI. CORRECTIVE ACTIONS

This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under Condition Report (CR) 1294133.

A. Immediate Corrective Actions

Upon discovering the 1B-B SI pump discharge isolation valve closed, the valve was immediately opened.

B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future The EDG blackout procedures will be revised to ensure the SI pump discharge valves are reopened at the completion of testing. Additional management focus has been applied since this event related to procedure use and adherence, particularly in the application of N/A associated with procedure use.

VII. PREVIOUS SIMILAR EVENTS AT THE SAME SITE

clearance was placed on the wrong fuses for a containment purge valve. This led to the purge valve not having power removed to its actuator while leak testing was being performed. While this configuration control issue was also associated with human performance (failure to identify the proper fuse location), it was not associated with procedural compliance.

containment penetration was not isolated within four hours. The event described in this LER is different in that the correct actions to comply with the TS were understood, but a human performance error resulted in the correct actions not being performed.

Concerns with procedural use and adherence are a station focus area and are described in Section VI.B of this LER.

VIII. ADDITIONAL INFORMATION

None.

IX. COMMITMENTS

None.