05000390/LER-2017-003

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LER-2017-003, Inadequate Operability Determination Leads to a Condition Prohibited by the Technical Specifications
Watts Bar Nuclear Plant, Unit 1
Event date: 01-04-2017
Report date: 03-03-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3902017003R00 - NRC Website
LER 17-003-00 for Watts Bar, Unit 1, Regarding Inadequate Operability Determination Leads to a Condition Prohibited by the Technical Specifications
ML17065A019
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 03/03/2017
From: Simmons P
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML17065A019 (7)


comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet 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 - 00 003

I. PLANT OPERATING CONDITIONS BEFORE THE EVENT

Watts Bar Nuclear Plant (WBN) Units 1 and 2 were at 100 percent rated thermal power (RTP) .

II. DESCRIPTION OF EVENT

A. Event Summary On January 4, 2017 at 1010 Eastern Standard Time (EST), Watts Bar Nuclear Plant Operations personnel declared Essential Raw Cooling Water (ERCW) (EllS:B1) strainer flush valve 2-FCV-67- 9B {EIIS:FCV} inoperable due to having a through-wall leak. The valve was replaced and the ERCW was returned to service on January 5, 2017 at 0952 EST. This event is reportable because the valve had had a through-wall leak since January 31, 2016 and had not been declared inoperable. A flaw evaluation is required in this situation to demonstrate the through-wall leak was stable and would not become worse. The failure to perform an adequate operability evaluation allowed the valve to remain in service for a period of time longer than allowed by Technical Specification (TS) 3.7.8, Essential Raw Cooling Water, Limiting Condition for Operation (LCO), Condition A.

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 Technical Specifications.

B. Inoperable Structures, Components, or Systems that Contributed to the Event No additional inoperable systems or components beyond the one identified valve contributed to this report.

C. Dates and Approximate Times of Occurrences Date Time Event (EST) 1/31/2016 Condition Report (CR) 1131468 documents a through-wall leak in the body of 2-FCV-67-9B.

1/04/2017 1010 Technical Requirement 3.4.5 Piping System Structural Integrity determined not met for 2-FCV-67-9B. ERCW TS LCO 3.7.8 Condition A entered.

1/05/2017 0930 Work Order 117564121 completed to replace valve 2-FCV-67-9B.

1/05/2017 0952 ERCW TS LCO 3.7.8 Condition A exited.

D. Manufacturer and Model Number of Components that Failed During the Event The leaking valve was a four inch 150 pound class carbon steel ball valve provided by Energy Products Group with a rated operating pressure of 200 psig.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects,Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, 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 - 00 003

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 As a result of an NRC question, the operability of valve 2-FCV-67-9B was reviewed by plant management. The valve was subsequently declared inoperable and the appropriate Technical Requirements (TR) and TS LCO Conditions were entered.

G. Failure Mode and Effect of Each Failed Component While a through-wall leak was identified for 2-FCV-67-9B, subsequent analysis performed demonstrated that it maintained operability with the presence of a leak.

H. Operator Actions

Upon discovery, Operations personnel promptly entered the appropriate TR and TS LCO conditions.

I. Automatically and Manually Initiated Safety System Responses There were no safety system responses associated with this issue.

III. CAUSE OF THE EVENT

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

The most probable cause of the thru wall leak on valve 2-FCV-67-9B is multimode degradation due to cavitation and jet impingement.

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

The causes of the inadequate operability evaluation are associated with human performance errors by both operations and engineering personnel. The apparent cause was attributed to a knowledge gap regarding ASME Class 2 and 3 piping associated with TR 3.4.5.

IV. ANALYSIS OF THE EVENT

On January 4, 2017, as a result of an NRC question, the operability of 2-FCV-67-9B was reviewed by plant management. The valve was subsequently declared inoperable and the correct TR and TS entered for the condition. The valve was replaced within

24 hours
2.777778e-4 days
0.00667 hours
3.968254e-5 weeks
9.132e-6 months

and the system restored to operability.

In investigating this issue, it was determined that a through-wall leak had been identified by plant personnel on January 31, 2016, and Condition Report (CR) 1131468 was initiated. WBN TR 3.4.5, Piping System Structural Integrity, requires the structural integrity of American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 piping at all times. The ERCW system is ASME Code Class 3 piping. The comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet 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 - 00 003 NRC further specifies requirements for through-wall leakage in Inspection Manual Chapter (IMC) 0326, Operability Determinations & Functionality Assessments for Conditions Adverse to Quality of Safety. IMC 0326 indicates for through-wall leakage of Class 3 piping and components, a flaw evaluation would need to be performed. When the leak was identified, the Senior Reactor Operator performing the operability review did not recognize the need to apply TR 3.4.5 and did not request engineering to perform a prompt operability evaluation.

In addition, during the screening process for CR 1131468, site engineering personnel also failed to recognize that a pressure boundary leak of Class 3 components required an ASME Code evaluation.

V. ASSESSMENT OF SAFETY CONSEQUENCES

The valve with the through-wall leak was analyzed after its replacement. This analysis determined that it remained structurally sound, and could accommodate all required design loads, including a safe shutdown earthquake. Accordingly, the safety consequences of this event are low.

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The leaking valve was evaluated after removal. This evaluation determined that it had adequate structural integrity to support operability even with a through-wall leak.

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.

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 valve with the through-wall leak was first identified on January 31, 2016 and was not replaced until January 5, 2017. An analysis on the valve after it was removed demonstrates that it would not have impacted operability of the ERCW system.

VI. CORRECTIVE ACTIONS

This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under CR 1247701.

A. Immediate Corrective Actions

When the condition was identified, the appropriate TR and TS LCO Conditions were entered. The valve was replaced and the ERCW strainer returned to service. The replacement valve has a stainless steel body, reducing the potential to be impacted by the identified degradation mechanisms.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet 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 - 00 003 B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future Additional training of operations and engineering personnel will be conducted related to this issue.

In addition, a training program on TS usage and compliance is in the process of being implemented for all licensed operating staff.

VII. PREVIOUS SIMILAR EVENTS AT THE SAME SITE

(CIV) was not entered when a surveillance associated with impacted penetration was not performed. The surveillance was recognized as potentially going late and corrective action was not taken in a timely fashion.

misinterpreted. When a CIV was found inoperable, it was not isolated in four hours as required, rather operations personnel were stationed to manually isolate the penetration if required. This was a misinterpretation of the wording of the note, which allows for intermittent opening under administrative controls of an inoperable penetration to perform testing.

Both this event and these previous events document knowledge gaps related to the TS compliance by members of the WBN operations staff. Specific training is in progress to address these knowledge gaps to reduce the potential for future recurrence.

VIII. ADDITIONAL INFORMATION

None.

IX. COMMITMENTS

None.