05000261/LER-2012-004, For H.B. Robinson Unit 2, Regarding Reactor Tripped Due to a Turbine Trip Caused by a Feedwater Isolation Signal from Steam Generator B High Level
| ML12160A056 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 05/23/2012 |
| From: | Cosgrove T Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RNP-RA/12-0062 LER 12-004-00 | |
| Download: ML12160A056 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2612012004R00 - NRC Website | |
text
10 CFR 50.73 jProgress Energy Serial: RNP-RA/12-0062 MAY 2 3 2012 Attn: Document Control Desk United States Nuclear Regulatory Commission Washington, DC 20555-0001 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-26 1/RENEWED LICENSE NO. DPR-23 LICENSEE EVENT REPORT NO. 2012-004-00 REACTOR TRIPPED DUE TO A TURBINE TRIP CAUSED BY A FEEDWATER ISOLATION SIGNAL FROM STEAM GENERATOR 'B' HIGH LEVEL Ladies and Gentlemen:
Pursuant to 10 CFR 50.73, Carolina Power and Light Company, now doing business as Progress Energy Carolinas, Inc., (PEC) is submitting the attached Licensee Event Report.
Should you have any questions regarding this matter, please contact Mr. R. Hightower, Supervisor - Licensing/Regulatory Programs at (843) 857-1329.
This document contains no new Regulatory Commitments.
Sincerely, K
Thomas S. Cosgrove Plant General Manager H. B. Robinson Steam Electric Plant, Unit No. 2 TSC/msc Attachment c:
V. McCree, NRC, Region II A. Billoch-Colon, NRC, NRR NRC Resident Inspector Progress Energy Carolinas, Inc.
Robinson Nuclear Plant 3581 West Entrance Road Hartsville, SC 29550
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES 1013112013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE H. B. Robinson Steam Electric Plant, Unit No. 2 05000261 1 OF 3
- 4. TITLE Reactor Tripped Due to a Turbine Trip Caused by a Feedwater Isolation Signal from Steam Generator
'B' High Level
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER M O N T H D A Y Y E A R Y E A R S E Q U E N T IA L R E V M O N T H D A Y Y E A R 0 5 0 0 0 NUMBER NO MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 03 28 2012 2012 004 00 05 23 2012 05000
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
- 9. OPERATING MODE E]
20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) f-20.2201(d) 11 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A) rl 50.73(a)(2)(viii)(A) 1 20.2203(a)(1) 11 20.2203(a)(4)
El 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii) 5 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
E]
50.73(a)(2)(x) 17 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
E]
73.71(a)(4) 55%
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[3 50.73(a)(2)(v)(B)
E]
73.71 (a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
[]
OTHER Specify in Abstract below
_ E 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D) or in During the course of the troubleshooting for this event several abnormalities or concerns were identified, investigated and factored into the investigation.
- 1)
The laboratory examination of the failed switch observed a high resistance on one of the contacts. The laboratory inspection of the switch reported that the presence of a small amount of debris on one or more of the switch contact surfaces interfered with the proper operation of the switch.
- 2)
The laboratory examination also identified a deposit of copper material on the same contact that had high resistance as noted in item 1 above. The contact that had this deposit was not part of the circuit at the time of the event; therefore, this cannot be classified as the point of failure. Although the source of this material could not be determined, it does indicate a vulnerability of the switches to debris collecting on the contact surfaces.
IV. SAFETY SIGNIFICANCE
As a result of the 1/FM-488B selector switch contacts loosing continuity temporarily while in the closed position, the switch sent a spurious signal to the Feedwater Regulating Valve FCV-488 which resulted in a reactor trip. The event occurred at 55% power which contributed to the event. At this power level the response time to address increasing SG level is greatly reduced.
Failure of this switch does not impact the ability to safely shutdown the plant or maintain it in a safe shutdown condition.
Beyond the risk from an unplanned automatic reactor trip there was no decrease in the margin of safety for the plant or public.
V. CORRECTIVE ACTIONS
Completed Corrective Actions:
a The failed switch was replaced and the circuitry was tested to verify proper operation.
Planned Corrective Actions
Replace the identified low wattage selector switches that provide control signals to plant equipment that are either classified as Critical or Important.
Initiate and complete a Preventive Maintenance Request that requires periodic replacement of the susceptible channel selector switches.
CR 422989 evaluated the weaknesses in implementation and effectiveness of the HBRSEP, Unit No. 2, corrective action program. Corrective actions from this CR will ensure that lower level events will be properly captured as OE.
VI. PREVIOUS SIMILAR EVENTS
Licensee Event Reports (LERs) for HBRSEP, Unit No. 2, were reviewed from the past 5 years. No similar events were identified.