05000391/LER-2017-005

LER-2017-005, Unplanned Emergency Core Cooling System Injection into the Reactor Coolant System due to Personnel Error

Watts Bar Nuclear Plant. Unit 2
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3912017005R00 - NRC Website

LER 17-005-00 for Watts Bar, Unit 2, Regarding Unplanned Emergency Core Cooling System Injection into the Reactor Coolant System due to Personnel Error

ML18025B349
Person / Time
Site:	Watts Bar, Watts Bar Nuclear Plant. Unit 2
Issue date:	01/25/2018
From:	Simmons P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 17-005-00
Download: ML18025B349 (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= Infccollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs.

NEOB-10202, (3150-0104). Office of Management and Budget, Washington, DC 20503. If a means 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

I. PLANT OPERATING CONDITIONS BEFORE THE EVENT

Watts Bar Nuclear Plant (WBN) Unit 2 was in Mode 5.

II. DESCRIPTION OF EVENT

A. Event Summary On November 26, 2017, at 1225 Eastern Standard Time (EST), the Watts Bar Nuclear Plant (WBN) Unit 2 experienced an unplanned Emergency Core Cooling System (ECCS) {EIIS:BQ} discharge to the Unit 2 Reactor Coolant System (RCS) {EllS:AB} while de-pressurized, in Mode 5, with the Pressurizer vented to the Pressurizer Relief Tank {EllS:TK}. ECCS injection via the Boron Injection flow path occurred during planned Safety Injection system Engineered Safety Features Actuation System (ESFAS) testing. The Boron Injection flow path should have been isolated and should not have resulted in any injection flow to the Unit 2 RCS.

This event is being reported to the Nuclear Regulatory Commission (NRC) under 10 CFR 50.73(a)(2)(iv)(A) as a safety system actuation.

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 (EST)

Event

11/26/17 1224 Initiated Unit 2 Safety Injection from the Main Control room (MCR) during performance of 0-S1-82-6, "18 Month Loss of Offsite Power With Safety Injection Test - DG 2B-B.

11/26/17 1225 Unit 2 experienced unplanned ECCS discharge to RCS 11/26/17 1232 Operator noted rapidly rising pressurizer level and lowering Volume Control Tank (VCT) level. Noted 2-FCV-63-25, Safety Injection System (SIS) Boron Injection Tank (BIT) Shutoff valve was open. Dispatched a unit operator to the 2B1 480V Reactor MOV Board to close 2-FCV-63-25 and open its associated breaker. Letdown was maximized and pressurizer level stopped rising. Peak pressurizer level was 79 percent.

11/26/17 1616 Operations made required four hour notification to the NRC for an unplanned ECCS Injection.

D. Manufacturer and Model Number of Components that Failed During the Event There were no failed components that contributed to this event.

E. Other Systems or Secondary Functions Affected

No other systems or secondary functions were affected.

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 F. Method of discovery of each Component or System Failure or Procedural Error The issue was identified by operations personnel as a result of increasing pressurizer level.

G. Failure Mode and Effect of Each Failed Component There was no equipment failure associated with this event.

H. Operator Actions

Upon identifying rising pressurizer level, the BIT outlet valve 2-FCV-63-25 was closed and its associated breaker was opened.

I. Automatically and Manually Initiated Safety System Responses Upon identifying that flow was being injected into the RCS, the operator isolated the flow path to the RCS.

III. CAUSE OF THE EVENT

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

The cause of this issue is that an Operator improperly used a Caution Order (CO) to determine the configuration of the breaker for the BIT outlet valve.

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

The cause of this issue is that an Operator improperly used a CO to determine the configuration of the breaker for the BIT outlet valve. This is a personal accountability issue for not properly using the human performance tool Correct Component Verification to validate the current position of the breaker in the field.

IV. ANALYSIS OF THE EVENT

During preparation for the performance of 0-S1-82-6, "18 Month Loss of Offsite Power With Safety Injection Test - DG 2B-B," it is intended that the BIT outlet valve is closed with power removed by opening its associated breaker. During the pre-test lineups in advance of performance, an Operator improperly used a Caution Order to determine the configuration of the breaker for the BIT outlet valve. A CO tag is provided to identify that a component is in an off normal configuration but does not control configuration.

The breaker had actually been repositioned to closed to support previous plant testing with no reconfiguration required following that testing based on plant conditions. The Operator relied solely on the information present on the CO tag to determine breaker position and did not validate the position in the field.

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 NEOB-10202, (3150-0104). Office of Management and Budget. Washington, DC 20503. If a means 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.

V. ASSESSMENT OF SAFETY CONSEQUENCES

The event resulted in an unplanned injection into the RCS which was promptly identified and corrected by Pressurizer level and pressure remained below limits. With the Unit in Mode 5 following refueling, the plant operating crew were able to stop the increase in pressurizer level well in advance of overfilling the pressurizer, therefore there was no safety consequence.

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event If the BIT outlet valve was unable to be closed, the affected charging pump could have been secured.

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 This event involved a single component during testing. Other means were available to secure ECCS injection.

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 Not applicable .

VI. CORRECTIVE ACTIONS

This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under Condition Report (CR) 1362001.

A. Immediate Corrective Actions

Upon identifying rising pressurizer level, the BIT outlet valve 2-FCV-63-25 was closed and its associated breaker was opened.

B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future Corrective actions for this event include revising procedures to ensure the breakers associated with the boron injection flow path will be tagged open during ESFAS testing and that lessons learned related to this event are communicated to operating crews. An evaluation on the use of Caution Orders for off normal equipment positions will be performed .

VII. PREVIOUS SIMILAR EVENTS AT THE SAME SITE

On May 10, 2017 the 1B-B Safety Injection (SI) pump discharge isolation valve was discovered closed during operator rounds as described in LER 390-2017-005. The cause of the mispositioned valve was the 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 Infocollects.Resource@nrc.gov. and to the Desk Officer. Office of Information and Regulatory Affairs, NEOB-10202. (3150-0104). Office of Management and Budget. Washington. DC 20503. If a means 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 result of an individual failing to follow procedure use and adherence requirements related to the application of Not Applicable during the performance of Emergency Diesel Generator (EDG) Blackout testing. The safety injection pump discharge valve was closed to support the test but was not reopened following the testing. Corrective actions for this event Includes personal accountability actions, revision of the EDG blackout procedures to ensure the SI pump discharge valves are reopened, and additional station focus on procedure use.

This event is similar to the event described in this report. WBN continues to focus on operator human performance as a result of this and prior events.

VIII. ADDITIONAL INFORMATION

None.

IX. COMMITMENTS

None.