05000285/LER-2006-008, Regarding Loss of Shutdown Cooling Due to Repressurizing Reactor Coolant System
| ML070370207 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 01/26/2007 |
| From: | Reinhart J Omaha Public Power District |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LIC-07-0005 LER 06-008-00 | |
| Download: ML070370207 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 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)(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 |
| 2852006008R00 - NRC Website | |
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Omaha Public Power District
. ~~1946 -2006 Fort Calhoun Station P.0. Box 550 Fort Calhoun, NE 68023 January 26, 2007 LIC-07-0005 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station P 1-137 Washington, DC 20555
Reference:
Subject:
Docket No. 50-285 Licensee Event Report 2006-008 Revision 0 for the Fort Calhoun Station Please find attached Licensee Event Report 2006-008, Revision 0, dated January 26, 2007. This report is being submitted pursuant to 10 CFR 50.73(a)(2)(v)(B). If you should have any questions, please contact me.
- - k'ffrey A. Reinhart Site Director Fort Calhoun Station JAR/epm Attachment C:
B. S. Mallett, NRC Regional Administrator, Region IV Alan Wang, NRC Project Manager J. D. Hanna, NRC Senior Resident Inspector INPO Records Center 2-NRC FORM 366 U.S. NUCLEAR REGULATORY COMA APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)
Estimated burden per response to comply with this mandatory collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />.
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the Records and FOIA/Privacy Service Branch (T-5 F52), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail LICENSEE EVENT REPORT (LER) to infocollects@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means 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 (See reverse for required number of information collection.
digits/characters for each block)
- 13. PAGE Fort Calhoun Station 05000285 1 OF 3
- 4. TITLE Loss of Shutdown Cooling Due to Repressurizing Reactor Coolant System
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR SEQUENTIAL REV M
FACILITY NAME DOCKET NUMBER YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 11 27 2006 2006 -008-0 00 01 26 2007 05000
- 9. OPERATING
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
MODE El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[] 20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A) 4 El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 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)
[] 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
E-50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
Fl 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
Z 50.73(a)(2)(v)(B)
El 73.71(a)(5) 0 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER E] 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in logs, and related procedures were reviewed. Procedural guidance, station policies and departmental expectations were considered. The analysis concluded that the root cause of this event was a mismatch between procedural guidance and crew experience.
The procedures in use at the time of the event, OP-3A "Plant Shutdown," OI-RC-9 "RCP Operation" and OI-RC-7 "RCS Pressure Control Normal Operation" contained guidance to prevent SDC isolation. However, a similar precaution located in OI-RC-7 discussing reduced spray flow with less than four RCPs running, should have been included prior to the step in OP-3A that directs securing the final two RCPs. This would have provided timely information to the control room supervisor (CRS) to monitor RCS pressure and prepare to secure pressurizer heaters and/or initiate auxiliary spray to reduce RCS pressure if necessary upon securing RCPs.
NiC FjORM 366A (1-2001
(If more space is required, use additional copies of NRC Form 366A) (17)
An operational historical review was conducted to determine if this was a first time event or if another crew faced similar conditions. It was discovered that an operating crew on April 30, 2006 had the same plant conditions as at the initiation of this event. The operating margins were identical for both crews. However, repressurization of the RCS did not occur on April thirtieth during the securing of the RCPs because the crew secured all pressurizer heaters 55 minutes prior to securing the RCPs. The securing of the pressurizer heaters for 55 minutes allowed the pressurizer to cool, thus eliminating the possibility of a pressure transient upon securing RCPs.
The contrast between the operating crews lies in the experience level of the crew. The April thirtieth crew had a more experienced CRS and a very experienced reactor operator (RO). The November twenty-seventh operating crew was, by comparison, less experienced. The CRS and ROs assigned to the crew were all licensed in 2004.
Neither the procedural guidance nor crew experience alone could be identified as a root cause through the analysis.
However, the combination of these factors formed a mismatch that lead to this event.
CORRECTIVE ACTIONS
As indicated above, plant pressure was immediately reduced and SDC was restored.
Appropriate plant procedures will be revised to include guidance on pressurizer heater operation and the need to initiate auxiliary pressurizer spray flow prior to securing the final two reactor coolant pumps. Discussion of this event will be incorporated into operator training and simulator scenarios. These corrective actions and other enhancements to plant operation will be controlled by the corrective action system.
SAFETY SIGNIFICANCE
The loss of shutdown cooling occurred when both SGs were available to remove decay heat. Although no RCP was in operation, all requirements to start RCPs in each loop were met. The station restored shutdown cooling in twelve minutes and exited Technical Specification (TS) 2.1.1(3)(c). TS 2.1.1(3)(c) states "With no coolant loop IN OPERATION, suspend all operations involving a reduction in boron concentration of the Reactor Coolant System and initiate corrective action to return the required coolant loop to operation in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />." RCS temperature rose 5F during this event. Therefore, this event had very minimal impact on the health and safety of the public.
SAFETY SYSTEM FUNCTIONAL FAILURE This event does result in a safety system functional failure in accordance with NEI-99-02.
PREVIOUS SIMILAR EVENTS
There have not been any other instances of a similar nature resulting in a loss of SDC at the Fort Calhoun Station in the last three years.
NRCL IFUOM 36b6A (1 -0UU1)