05000259/LER-2014-006, Regarding Main Steam Relief Valves Lift Settings Outside Technical Specifications Required Setpoint
| ML15028A193 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/26/2015 |
| From: | Polson K Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 14-006-00 | |
| Download: ML15028A193 (8) | |
| 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 |
| 2592014006R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 January 26, 2015 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 1 Renewed Facility Operating License No. DPR-33 NRC Docket No. 50-259
Subject:
Licensee Event Report 50-259/2014-006-00 The enclosed Licensee Event Report provides details of a failure to meet the requirements of Browns Ferry Nuclear Plant, Unit 1, Technical Specification 3.4.3 concerning main steam relief valve operability. 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 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, I.J oson Site Vice President
Enclosure:
Licensee Event Report 50-259/2014-006 Main Steam Relief Valves' Lift Settings Outside Technical Specifications Required Setpoint cc (w/ Enclosure):
NRC Regional Administrator - Region II Senior Resident Inspector - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Unit I Licensee Event Report 50-25912014-006-00 Main Steam Relief Valves' Lift Settings Outside Technical Specifications Required Setpoint 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 6
- 4. TITLE: Main Steam Relief Valves' Lift Settings Outside Technical Specifications Required Setpoint
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUMBEN LR E
MONTH DAY YEAR N/A NUMBER NO.
NA05000 FACILITY NAME DOCKET NUMBER 11 25 2014 2014 - 006 -
00 01 26 2015 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)
[] 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
El 20.2201(d)
[3 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A) 10 20.2203(a)(1)
[I 20.2203(a)(4)
El 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)
[I 50.73(a)(2)(iii) 0l 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0l 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[I 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
[I 20.2203(a)(2)(iv) 0l 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B) 0l 73.71(a)(5) 100 [1 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstrat beo or inNRC
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
Mike Oliver, Sr Licensing Program Manager 256-729-7874MANU-REPORTABLE MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX B
SB RV T020 Y
N/A N/A N/A N/A N/A
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (Ifyes, complete 15. EXPECTED SUBMISSION DATE)
[
NO DATE N/A N/A N/A ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On November 25, 2014, the Tennessee Valley Authority determined, two of thirteen Browns Ferry Nuclear Plant (BFN), Unit 1, Main Steam Relief Valves (MSRVs) mechanically actuated at pressures outside the allowed +/- three percent tolerance of their Technical Specification (TS) setpoint. The BFN, Unit 1, TS Limiting Condition for Operation 3.4.3 requires the safety function of twelve MSRVs to be Operable in reactor Modes 1, 2, and 3. Since two of the thirteen MSRVs actuated outside their TS setpoint allowance by greater than +/- three percent, it is probable that BFN, Unit 1, operated with only eleven Operable MSRVs for longer than allowed by the TS.
An analysis of the event determined that there was no impact on the MSRVs to perform their specified safety function.
The cause for the MRSVs failing above three percent of their setpoint was corrosion bonding of the pilot valve discs to the valve seats because the valve disc surface finish does not make allowance for corrosion bonding. Corrective actions to reduce the probability of similar events occurring in the future are to determine what the required MSRV pilot valve disc finish is for optimal platinum adhesion and to revise the valve procedure to add steps to verify pilot disc finish is equal to or better than this value before the disc is coated in platinum.
NRC FORM 366 (02-2014)
- 1.
Plant Operating Conditions Before the Event
On November 25, 2014, Browns Ferry Nuclear Plant (BFN) Unit 1 was in Mode 1 at approximately 100 percent power.
II.
Description of Event
A. Event On November 25, 2014, the Tennessee Valley Authority (TVA) determined, two of the thirteen BFN, Unit 1, Main Steam Relief Valves (MSRVs) [SB] mechanically actuated at pressures outside the allowed +/- three percent tolerance of their Technical Specification (TS) setpoint. The two out-of-tolerance MSRVs have the same nameplate setpoint of 1135 pounds per square inch gauge (psig). The as-found setpoint for one MSRV was outside the TS setpoint allowance (i.e.,
6.7 percent) at 1211 psig, and the as-found setpoint of the other MSRV was outside the TS setpoint allowance (i.e., 7.8 percent) at 1224 psig. The MSRVs were thus not Operable for an indeterminate period during the previous operating cycle, which started on December 4, 2012, and ended on October 4, 2014.
BFN, Unit 1, TS Limiting Condition for Operation (LCO) 3.4.3 requires the safety function of twelve MSRVs to be Operable in reactor Modes 1, 2, and 3. With one or more required MSRVs not Operable, the unit is required to be placed in Mode 3 (Hot Shutdown) within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 (Cold Shutdown) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Since two of the thirteen MSRVs actuated outside their TS setpoint allowance of
+/- three percent, it is probable that BFN, Unit 1, operated with only eleven Operable MSRVs for longer than allowed by the TS.
B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event
There were no inoperable structures, components, or systems that contributed to this event.
C. Dates and approximate times of occurrences
December 4, 2012 BFN, Unit 1, exits refueling outage 9 (U1R9) and begins cycle 10 (U1C10) operation.
October 4, 2014 BFN, Unit 1, ends UIC10 and begins U1R10.
November 25, 2014 National Technical Systems (NTS) completes testing of MSRVs following U1R10 and reports two MSRVs failed the as-found setpoint test.
NRC FORM 366 (02-2014)
D. Manufacturer and model number (or other identification) of each component that failed during the event All BFN MSRVs are Target Rock Model No. 7567F [T020]. There were no other systems or secondary functions affected.
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 The out-of-tolerance lift setpoints were identified during the performance of as-found setpoint testing at NTS, located in Huntsville, Alabama.
G. The failure mode, mechanism, and effect of each failed component, if known The MSRVs failed to lift within the lift setpoint tolerances due to corrosion bonding.
H. Operator actions
There were no operator actions.
I. Automatically and manually initiated safety system responses
There were no automatically or manually initiated safety system responses.
Ill.
Cause of the Event
A. The cause of each component or system failure or personnel error, if known The cause for the MRSVs failing above three percent of their setpoint was corrosion bonding of the pilot valve discs to the valve seats because the valve disc surface finish does not make allowance for corrosion bonding.
B. The cause(s) and circumstances for each human performance related root cause There was no human performance related root cause.
IV.
Analysis of the event
TVA is submitting this report in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plant's Technical Specifications.
On November 25, 2014, NTS completed the as-found testing of the thirteen pilot MSRVs, which were removed from BFN, Unit 1, during U1R10. Two MSRVs failed the as-found setpoint testing criteria. Twelve MSRVs are required for operability per TS 3.4.3 with operability defined as having an as-found setpoint within +/- three percent of the nameplate setpoint. The results of the test are shown in the following table.
NRC FORM 366 (02-2014)
As-Found Lift Setpoints MSRV Unique Pilot Valve MSRV TS 1st Test 2nd Test 3rd Test Identification Number Number Setpoint Deviation Deviation Deviation 1-PCV-001-0004 1014 1155 0.8 0.4 0.3 1-PCV-001-0005 1079 1145 0.6
- - 0.1 0.6 1-PCV-001-0018 1070 1145 1.1
- - 0.2
- - 0.5 1-PCV-001-0019 1033 1135
- - 0.4
- - 0.4
- - 0.1 1-PCV-001-0022 1240 1145 0.5 0.6 0.3 1-PCV-001-0023 1264 1135 3
- - 0.3 1-PCV-001-0030 1028 1145
- - 1.2
- - 0.3 0.5 1-PCV-001-0031 1260 1135
- - 0.3
- - 0.5 1-PCV-001-0034 1259 1135 1.9 1.9 1.5 1-PCV-001-0041 1026 1155 2.1 0.4 0.3 1-PCV-001-0042 1064 1155
- - 1.4 0.2 1.3 1-PCV-001-0179 1085 1155
- - 2.9
- - 3.4
- - 2.9 1-PCV-001-0180 1016 1155 1.7 1.1 0.9 (1) Shaded values indicate 1st Test results, which were outside of the TS-required three percent tolerance. Note that the first actuation is the setpoint of record for acceptance criteria determination.
Subsequent actuations are used to determine setpoint drift and valve performance characteristics.
The MSRV pilot valves for UIC9 were platinum coated. When tested at the end of the cycle, the MSRV pilot valve test results were acceptable as only one of the thirteen MSRV pilot valves failed their as-found lift setpoint value. Based on as-found test data received from other utilities that use the platinum coating, previously high numbers of as-found lift setpoint failures have been reduced to a rate similar to those recently documented at BFN. Continuing the practice of utilizing platinum coated discs in the MSRV pilot valves will reduce the probability of similar events occurring in the future.
V.
Assessment of Safety Consequences
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The two out of tolerance MSRV pilot valves have the same nameplate setpoint of 1135 psig. The as-found setpoint for one MSRV exceeded the TS setpoint by 6.7 percent at 1211 psig and the other MSRV exceeded the TS setpoint by 7.8 percent at 1224 psig.
All BFN units have thirteen MSRVs arranged in three setpoint groups. There are four MSRVs with a setpoint of 1135 psig, four MSRVs with a setpoint of 1145 psig, and five MSRVs with a setpoint 1155 psig.
NRC FORM 366 (02-2014)
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 event occurred during reactor operation. Since two of the thirteen MSRVs actuated outside their TS setpoint allowance, it is probable that BFN, Unit 1, operated with only eleven Operable MSRVs for longer than allowed by the TS.
AREVA performed analyses at the request of TVA and determined that the two highest as-found MSRV opening setpoints are bounded by the two highest ASME valve groupings shown in their analyses. The as-found setpoints for the other ten valves (assuming one failure) are conservatively bounded by the lowest setpoint grouping. Therefore, the limiting ASME overpressurization event was not re-analyzed since the analytical setpoint data for the previous ASME case conservatively bounds the current as-found setpoints. The analysis results demonstrate that the design MSRV capacity is capable of maintaining reactor pressure below the ASME Code limit of 110 percent of vessel design pressure (110 percent x 1250 psig = 1375 psig). All twelve MSRVs, even the two that actuated outside of the +/- three percent TS criteria, actuated at or before 1224 psig, thus satisfying the ASME Code limit of 110% of vessel design pressure.
NUREG-0800, Chapter 15, Section 15.8, Anticipated Transients Without Scram, states that in evaluating the reactor coolant system boundary for Anticipated Transients Without Scram (ATWS) events, "the calculated reactor coolant system transient pressure should be limited such that the maximum primary stress anywhere in the system boundary is less than that of the 'emergency conditions' as defined in the ASME Nuclear Power Plant Components Section II1. The acceptance criteria for reactor coolant pressure, based upon the ASME Service Level C limits, are approximately 10.3 MPa (1500 psig) for BWRs." For the ATWS analysis, the setpoint groupings conservatively bound the ten lowest as-found MSRV opening setpoints; however, the two highest valve setpoints fall outside the bounds of the valve groupings. Therefore, AREVA re-analyzed the limiting ATWS overpressurization event, which was identified as the ATWS pressure regulator failed open 100 percent rated power and 81 percent rated flow at the beginning of cycle exposure. The results from this analysis indicated that, despite the two MSRVs that exceeded the as-found setpoint, the maximum vessel pressure and maximum dome pressure reach a maximum of 1395 psig, and, therefore, do not exceed 1500 psig, the ATWS vessel pressure limit. Therefore, there was no impact on the MSRVs to perform their specified safety function.
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 There was no failure that that rendered a train of a safety system inoperable.
In summary, this condition is of low safety significance and posed little risk to public health and safety.
NRC FORM 366 (02-2014)
VI.
Corrective Actions
Corrective Actions are being managed by TVA's corrective action program under Problem Evaluation Report (PER) 962223.
A. Immediate Corrective Actions
All thirteen MSRV pilot valves were replaced during U1R10 with refurbished pilot valves certified within one percent of name plate setpoint (as-left testing).
B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future Corrective actions to reduce the probability of similar events occurring in the future are to determine what the required MSRV pilot valve disc finish is for optimal platinum adhesion and to revise the valve procedure to add steps to verify pilot disc finish is equal to or better than this value before the disc is coated in platinum.
VII.
Additional Information
A. Previous similar events at the same plant TVA has submitted previous reports on similar events at BFN. The last LERs for each of the three BFN units are 50-259/2010-005-01, 50-260/2009-003-01, and 50-296/2012-006-01. The previous LER for BFN, Unit 1, reported probable inoperability of three of thirteen MSRV pilot valves during Cycle 8 operation.
B. Additional Information
There is no additional information.
C. Safety System Functional Failure Consideration A review of this event determined that a Safety System Functional Failure as defined in NEI 99-02, Regulatory Assessment Performance Indicator Guidelines, did not occur. This event did not prevent the ability of a system to fulfill its safety function to either shutdown the reactor, remove residual heat, control the release of radioactive material, or mitigate the consequences 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)