05000440/LER-2008-001, Regarding Condition Prohibited by Technical Specifications Due to Unrecognized Reactor Core Isolation Cooling Inoperability
| ML080800451 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 03/14/2008 |
| From: | Allen B FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-08-103 LER 08-001-00 | |
| Download: ML080800451 (6) | |
| 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) 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 |
| 4402008001R00 - NRC Website | |
text
FENOC Perry Nuclear Power Station NOC10 Center Road FirstEnergy Nuclear Operating Company Perry Ohio 44081 Barry S. Allen Fa. 440-280-5382 Vice President Fax: 440-280-8029 March 14, 2008 L-08-103 10CFR50.73 ATTN: Document Control Desk United States Nuclear Regulatory Commission Washington, D.C. 20555-0001
SUBJECT:
Perry Nuclear Power Plant Docket No. 50-440, License No. NPF-58 Licensee Event-Report Subimittal Enclosed is Licensee Event Report (LER) 2008-001, "Condition Prohibited by Technical Specifications Due to Unrecognized Reactor Core Isolation Cooling Inoperability." The root cause analysis associated with the RCIC flow controller performance is still under managementreview at the time of this report. A supplemental report will be issued, if required, if any additional causes and corrective actions are identified.
There are no regulatory commitments contained in this letter. Any actions discussed in this document that represeht'intended or planned actions are described for the NRC's information, and are not regulatory commitments.
If you have questions or require additional information, please contact Mr. Jeffrey J. Lausberg, Manager - Regulatory Compliance, at (440) 280-5940.
Sincere-*,
Barry'S. Allen
Enclosure:
LER 2008-001 cc: NRC Project Manager NRC Resident Inspector NRC Region III
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 8/31/2010 (9-2007)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE Perry Nuclear Power Plant 05000 440 1 OF5
- 4. TITLE Condition Prohibited by Technical Specifications Due to Unrecognized Reactor Core Isolation Cooling Inoperability
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YER NUMBER NO, MONTH jDAY IYEAR FDOCKET NUMBER 01 14 2008 2008
- - 001 00 03FACILITY NAME
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[
20.2201(b)
[I 20.2203(a)(3)(i)
[D 50.73(a)(2)(i)(C)
E] 50.73(a)(2)(vii) 1 20.2201(d)
E] 20.2203(a)(3)(ii)
[
50.73(a)(2)(ii)(a)
E] 50.73(a)(2)(viii)(A)
J 20.2203(a)(1)
[
20.2203(a)(4)
[
50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
[]20.2203(a)(2)(i)
[]50.36(c)(1)(i)(A)
[]50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[
20.2203(a)(2)(ii)
[
50.36(c)(1)(ii)(A)
[
50.73(a)(2)(iv)(A)
Ej 50.73(a)(2)(x)
[]20.2203(a)(2)(iii)
[]50.36(c)(2)
[]50.73(a)(2)(v)(A)
[1 73.71 (a)(4) 100 Ej 20.2203(a)(2)(iv)
[_1 50.46(a)(3)(ii)
E] 50.73(a)(2)(v)(B)
Ej 73.71 (a)(5)
E] 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[
50.73(a)(2)(v)(C)
EI OTHER Specify in Abstract below
__ 20.2203(a)(2)(vi)
[
50.73(a)(2)(i)(B)
[
50.73(a)(2)(v)(D) or in Additional monitoring of the flow controller output since that time has not identified any additional occurrences of the flow controller output anomaly.
CAUSE OF EVENT
The flow controller output change is likely the result of an intermittent failure of one of the four replaced components (flow controller and connecter, the power supply, the ramp generator/signal converter, or the computer input circuit board). The failure does involve the output of the flow controller but is most likely the connector.
Failure to closely monitor flow controller output following previous flow controller replacement contributed to the failure to identify the fluctuations more promptly.
Equipment Reliability Issues also contributed to this failure. Subsequent to the replacement of the flow controller and connector, the power supply, the ramp generator/signal converter and the computer input circuit board, the condition has not reoccurred.
The root cause analysis associated with the RCIC flow controller performance is still under management review at the time of this report. A supplemental report will be issued, if required, if any additional causes and corrective actions are identified.
EVENT ANALYSIS
The RCIC system provides core cooling automatically or manually following Reactor Pressure Vessel (RPV) isolation. The RCIC system provides cooling for reactor pressures from 165 to 1215 pounds per square inch absolute (psia) (rated flow is 700 gallons per minute at 1118 psia). The RCIC system is designed to initiate and discharge, within 30 seconds, to provide the specified flow into the RPV at the specified pressure.
Technical Specification (TS) Limiting Condition for Operation (LCO) 3.5.3 requires that the system be operable, in Mode 1. With the RCIC system inoperable, the Required Action is to verify High Pressure Core Spray is Operable within an hour and to restore the RCIC system to operable status in 14 days or be in hot shutdown within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Since the condition had been unrecognized from December 10, 2007, until January 14, 2008, these requirements were not completed within the required time.
The RCIC system response is credited for several plant transients to provide RPV level control and decay heat removal until Residual Heat Removal systems are capable of providing decay heat removal. A conservative estimation of RCIC mission time is 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (maximum required operating duration based upon credited transient sequences and assumed in the Probabilistic Risk Assessment model).
The immediate investigation noted that the Flow Controller Output anomaly was repeating and the first occurrence was on December 21, 2007. The follow-up root cause investigation identified additional occurrences dating back to December 10, 2007. The anomaly has therefore been known to be present for 35 days. The investigation team
believes that the anomaly was most likely introduced into the system during the numerous flow controller changes that were performed to address RCIC flow controller tuning concerns during November and December 2007.
A bounding evaluation was performed assuming automatic operation of RCIC has been unavailable for 48 days (November 28, 2007, through January 14, 2008). Operation of the RCIC system using manual control was available and demonstrated following the plant shutdown in November. The probability of the RCIC manual control failure as a result of human error was included in the evaluation. The resulting Incremental Conditional Core Damage Probability (ICCDP) was determined to be 1.84E-08. The Incremental Conditional Large Early Release Probability (ICLERP) by definition Can not be greater than the ICCDP.
Configurations with a core damage probability of less than 1.OE-06 and a large early release probability of less than 1.OE-07 are not considered to be risk significant events, therefore this event is considered to be of very low risk significance.
CORRECTIVE ACTIONS
The Bailey 701 flow controller and connecter, the power supply, the ramp generator/signal converter, and the computer input circuit board were replaced.
Plant operating staff is currently monitoring the flow controller output via the plant computer on-a daily basis. This check has been included in the control room operator rounds.
The Bailey 701 Flow Controllers will be replaced with new controllers no later than the end of Refuel Outage 12, scheduled for the spring of 2009.
The RCIC Control System Tuning procedure will be revised to specify the use of the plant computer to monitor RCIC flow controller output following replacement or adjustment to a controller.
PREVIOUS SIMILAR EVENTS
Two LERs, Automatic Reactor Protection System Actuation Due to Feedwater Control Power Supply Failure, 2007-004-1 and Plant Startup With Inoperable Reactor Core Isolation Cooling System, 2007-005 document events in 2007. Both conditions were related to improper tuning of the RCIC Bailey 701 flow controller. While both conditions resulted in the flow controller being replaced, the purpose of replacement was to minimize the out of service time for the tuning and not the result of a component failure. For the January 14, 2008, event described in this LER the failure cause is considered a component failure therefore the cause is different than the previous tuning issues. Since the cause is different, the corrective actions from LER 2007-004-1 and LER 2007-005 would not have been expected to prevent this event.
Condition Report 06-00318 documents an event in which the RCIC pump did not respond properly when placed in Automatic. The cause of that event was determined to be dirty contacts on the balance resistor causing the Bailey flow controller to drift low. The issue in
LER 2008-001 is that the component failure is intermittent and does not appear to have been due to failure of a flow controller component. The corrective actions from Condition Report 06-00318 include replacing the Bailey flow controller with a new flow controller from another manufacturer. This corrective action has not yet been completed and is being tracked for completion in Refuel Outage 12.
COMMITMENTS
There are no regulatory commitments contained in this letter. Any actions discussed in this document that represent intended or planned actions are described for the NRC's information, and are not regulatory commitments.PRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPER