05000259/LER-2014-005, Regarding Automatic Depressurization System Valve Inoperable for Longer than Allowed by Technical Specifications

Regarding Automatic Depressurization System Valve Inoperable for Longer than Allowed by Technical Specifications

ML15007A381
Person / Time
Site:	Browns Ferry
Issue date:	12/23/2014
From:	Polson K Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 14-005-00
Download: ML15007A381 (9)

LER-2014-005, Regarding Automatic Depressurization System Valve Inoperable for Longer than Allowed by Technical Specifications

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function
2592014005R00 - NRC Website

text

Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 December 23, 2014 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit I Renewed Facility Operating License No. DPR-33 NRC Docket No. 50-259

Subject:

Licensee Event Report 50-259/2014-005-00 The enclosed Licensee Event Report provides details of an Automatic Depressurization System valve inoperable for longer than allowed by the Technical Specifications. The Tennessee Valley Authority (TVA) is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(i)(B), as any operation or condition prohibited by Technical Specifications.

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Nuclear Site Licensing Manager, at (256) 729-2636.

Respectfully, Site Vice President

Enclosure:

Licensee Event Report 50-259/2014-005 Automatic Depressurization System Valve Inoperable for Longer Than Allowed by Technical Specifications cc (w/ Enclosure):

NRC Regional Administrator - Region II Senior Resident Inspector - Browns Ferry Nuclear Plant A-O~f-,

ENCLOSURE Browns Ferry Nuclear Plant Unit I Licensee Event Report 50-25912014-005-00 Automatic Depressurization System Valve Inoperable for Longer Than Allowed by Technical Specifications See Enclosed

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 01/31/2017 (02-2014)

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

3. PAGE Browns Ferry Nuclear Plant, Unit 1 05000259 1 of 7

4. TITLE: Automatic Depressurization System Valve Inoperable for Longer Than Allowed by Technical Specifications

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO.

N/A 05000 FACILITY NAME DOCKET NUMBER 10 29 2014 2014 -

005 -

00 12 23 2014 N/A 05000

9. OPERATING MODE

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

[o 20.2201(b)

[I 20.2203(a)(3)(i)

[I 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) o 20.2201(d) 0l 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

[I 50.73(a)(2)(viii)(A)

El 20.2203(a)(1)

[E 20.2203(a)(4) 0l 50.73(a)(2)(ii)(B)

[I 50.73(a)(2)(viii)(B)

El 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A) 0l 50.73(a)(2)(iii) 0l 50.73(a)(2)(ix)(A)

10. POWER LEVEL 0l 20.2203(a)(2)(ii)

Cl 50.36(c)(1)(ii)(A) 0l 50.73(a)(2)(iv)(A)

[I 50.73(a)(2)(x) 0l 20.2203(a)(2)(iii)

[] 50.36(c)(2)

El 50.73(a)(2)(v)(A) 0l 73.71(a)(4)

El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

[I 50.73(a)(2)(v)(B)

El 73.71(a)(5) 020 [E

20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

[I 50.73(a)(2)(v)(C)

El OTHER 0l 20.2203(a)(2)(vi)

ED 50.73(a)(2)(i)(B)

[I 50.73(a)(2)(v)(D) specify in Abstract bel or in On November 7, 2014, a temporary modification was implemented to restore operability of the ADS safety function. The ADS control air accumulator intended for MSRV 1-19 remains connected to MSRV 1-18. The controls and logic for the two valves were swapped to ensure the ADS circuitry from MSRV 1-19 opens MSRV 1-18. This temporary modification will remain in place until the condition can be corrected during the next refueling outage.

B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event

The control air root valve 1-SHV-032-2519 was inappropriately isolated by a separate, and unrelated, human performance error, that occurred during the fall 2014 BFN Unit 1 RFO, resulting in the discovery of the ADS control air accumulator misconfiguration between MSRV 1-19 and MSRV 1-18.

C. Dates and approximate times of occurrences

Dates & Approximate Times December 7, 2006 April 29, 2007 May 22, 2007 October 29, 2014, at 2225 hours0.0258 days <br />0.618 hours <br />0.00368 weeks <br />8.466125e-4 months <br /> CDT October 30, 2014 November 7, 2014, at 1746 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.64353e-4 months <br /> Central Standard Time (CST)

Occurrence Air hoses to MSRV 1-19 and 1-18 were installed in a swapped configuration during BFN Unit 1 restart.

Operations identified MSRV misconfiguration.

Work that same day failed to correct the condition.

BFN Unit 1 was brought on-line with the misconfiguration still in place. Start of MSRV 1-19 inoperability.

MSRV 1-19 failed to open during the MSRV Manual Cycle Test. BFN Unit 1 entered TS LCO 3.5.1.E.

Troubleshooting activities identified the misconfiguration of the control air lines to both the MSRV 1-19 and MSRV 1-18.

Implemented temporary modification to restore ADS function. Operations declared MSRV 1-19 Operable and exited TS LCO 3.5.1.E.

D. Manufacturer and model number (or other identification) of each component that failed during the event:

There were no failed components associated with this event.

NRC FORM 366 (02-2014)

E. Other systems or secondary functions affected

There were no other system or secondary functions affected.

F. Method of discovery of each component or system failure or procedure error:

During performance of the BFN Unit 1 MSRV Manual Cycle Test, MSRV 1-19 failed to open. Investigation of the failure on October 30, 2014, revealed the failure of MSRV 1-19 to stroke was due to the control air root valve, 1-SHV-032-2519, being inappropriately isolated by a separate human performance error. Further investigation revealed a misconfiguration of the control air lines to both MSRV 1-19 and MSRV 1-18.

G. The failure mode, mechanism, and effect of each failed component, if known:

There were no failed components associated with this event.

H. Operator actions

MSRV 1-19 failed to open during the MSRV Manual Cycle Test when Operations took the handswitch to the open position. Operations declared MSRV 1-19 inoperable and entered TS LCO 3.5.1.E.

Ill.

Cause of the Event / Problem Statement A. The cause of each component or system failure or personnel error, if known:

The direct cause of this condition was MSRVs 1-18 and 1-19 were initially installed with swapped control air supplied due to a latent human performance error made during BFN Unit 1 restart in 2006.

Contributing to this event was that there are no requirements to verify the ADS-MSRVs are connected to ADS accumulators.

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

cause

The cause of this event was a latent organizational and programmatic gap associated with the BFN Unit 1 Restart Organization. Specifically, the management and organizational infrastructure in place during the BFN Unit 1 restart was inadequate to preclude numerous human performance errors during the 2005-2007 time period, including the multiple human performance errors associated with this event.

IV.

Analysis of the event

The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plant's Technical Specifications.

The BFN Unit 1 TS LCO 3.5.1, ECCS - Operating, requires the ADS function of 6 MSRVs to be Operable, during Mode 1, and Modes 2 and 3, when the steam dome pressure is greater than or equal to 150 pounds per square inch gauge (psig). With one BFN Unit 1 ADS valve inoperable, TS 3.5.1 Required Action E.1 requires the ADS valve to be returned to Operable status in 14 days. If the ADS valve cannot be restored to NRC FORM 366 (02-2014)

Operable status in the required time period, TS 3.5.1 Required Actions G.A and G.2 require the unit to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and to reduce reactor steam dome pressure to less than or equal to 150 psig in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

Inoperability of MSRV 1-19 began on May 22, 2007, when BFN Unit 1 was brought on-line after an extended shutdown and ended on November 7, 2014, at 1746 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.64353e-4 months <br /> CST, when the ADS function was declared operable following a temporary modification to MSRVs 1-19 and 1-18. Therefore, BFN Unit 1 operated with one inoperable ADS valve for longer than allowed by TS 3.5.1 Actions.

BFN Unit 1 LCO 3.0.4 prohibits Mode changes when an LCO is not met except under certain conditions that were not applicable to this event. Since it was not recognized that one BFN Unit 1 ADS valve was inoperable from May 22, 2007, until November 7, 2014, BFN changed Modes in violation of LCO 3.0.4 on multiple occasions.

This event was the result of multiple, and latent, human performance errors at all levels of the organization during BFN Unit I restart. Specifically, human performance errors were introduced when flex hoses were initially installed incorrectly in 2006, when preparing the flawed corrective maintenance work order after the condition was identified in 2007, when the work order was approved with the flaw, when the work order was performed without identifying the error, and when the organization failed to verify the identified misconfiguration had been corrected.

Human performance issues during the BFN Unit 1 Restart were previously identified and evaluated by Problem Evaluation Report (PER)137614 in 2008 to investigate the five BFN Unit 1 scrams following BFN Unit 1 restart. The investigation identified three common root causes including an inadequate BFN Unit 1 management and organizational infrastructure, less than adequate risk management, and a lack of first line supervision and management oversight. Consistent with these findings, the cause of this event was a latent organizational and programmatic gap associated with the BFN Unit I Restart Organization.

Contributing to this event was that there are no requirements to verify the ADS-MSRVs are connected to ADS accumulators. During each outage, testing is performed as part of pre-startup activities to verify the ADS valves can be cycled from the control room.

The MSRV solenoid pilot valves are removed and replaced with lab verified, refurbished pilot valves that have certified set points, and the ADS accumulators are checked for soundness. However, the connection of the ADS-MSRVs to the correct ADS accumulators is not verified. This missing requirement, in part, allowed this misconfiguration condition to exist undetected for approximately seven years.

The likelihood of the MSRV control air lines being swapped in the future is unlikely because the flex hoses connecting control air to the MSRVs cannot be physically manipulated to interface with an adjacent MSRV because the interface is welded and this union is not broken during normal valve maintenance. To ensure this condition does not exist for the other BFN units, walkdowns will be performed on the BFN Units 2 and 3 MSRV control air lines during each units upcoming refueling outage. To preclude this condition from recurring, the MSRV pilot valve installation procedures will be revised to verify ADS-MSRVs are connected to the correct accumulator.

I NRC FORM 366 (02-2014)

V.

Assessment of Safety Consequences

ADS serves as a backup to the HPCI System under certain loss of coolant accident conditions. During the last three years, one ADS valve has been inoperable, and the HPCI and low pressure ECCS have been out service for maintenance along with the inoperable ADS valve. Evaluations provided by General Electric and AREVA have shown that the bounding scenario plus the loss of the ADS valve does not result in failure to meet 10 CFR 50.46 and Primary Containment acceptance criteria.

A Probabilistic Risk Analysis (PRA) of this condition concluded that the unavailability of the MSRV 1-19 to perform an ADS function or to be backed by an accumulator would have an insignificant impact on overall plant risk. The PRA concluded that there was no plant configuration which would present a significant increase in risk over normal test and maintenance due to the unavailability of a single ADS valve.

Based on the discussion above, the safety significance of this condition is minimal and did not pose a threat to the health and safety of the public or plant personnel.

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event:

Five of the six ADS valves remained available. Although the ADS function for MSRV 1-19 was unavailable, the valve would have performed within the tolerance of the mechanical setpoint of 1135 psig during an overpressurization event.

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:

The ADS is not required to perform its safety function when the reactor is shut down.

C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from discovery of the failure until the train was returned to service:

Inoperability of MSRV 1-19 began on May 22, 2007, when BFN Unit 1 was brought on-line after an extended shutdown and ended on November 7, 2014, at 1746 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.64353e-4 months <br /> CST, when the ADS function was declared operable following a temporary modification to MSRVs 1-19 and 1-18.

VI.

Corrective Actions

Corrective Actions are being managed by TVA's corrective action program under Problem Evaluation Report (PER) 952082.

Immediate Corrective Actions

A temporary modification was implemented to restore operability of the ADS safety function. This temporary modification will remain in place until the configuration can be corrected during the next refueling outage.

NRC FORM 366 (02-2014)

Corrective Actions that Reduce Probability of Similar Events Occurrinq in the Future BFN will perform walkdowns of the BFN Units 2 and 3 MSRV control air lines during each units upcoming refueling outage to ensure proper configuration.

BFN will revise the MSRV pilot valve installation procedures for all three units to include a step to validate the ADS-MSRVs are connected to the appropriate ADS accumulator.

VII.

Additional Information

A. Previous similar events at the same plant:

A search of the Corrective Action Program and BFN Licensee Event Reports for Units 1, 2, and 3, for approximately the past three years did not identify any similar events.

B. Additional Information

There is no additional information.

C. Safety System Functional Failure Consideration:

In accordance with the Nuclear Energy Institute (NEI) 99-02, "Regulatory Assessment Performance Indicator Guideline," this event is not considered a system functional failure because the minimum number of ADS valves remained available to perform their safety function in the event of an accident.

D. Scram with Complications Consideration:

This event did not result in a reactor scram.

VIII. Commitments

There are no commitments.

NRC FORM 366 (02-2014)