05000285/LER-2003-003, Calhoun Station Re Reactor Trip During Plant Shutdown
| ML033250339 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 11/11/2003 |
| From: | Ridenoure R Omaha Public Power District |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LIC-03-0136 LER 03-003-00 | |
| Download: ML033250339 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 2852003003R00 - NRC Website | |
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Omaha Public PowerDstict 444 South 16th Street Afall Omaha N'E 68102-2247 November 11, 2003 LIC-03-0136 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 2003-003 Revision 0 for the Fort Calhoun Station Please find attached Licensee Event Report 2003-003, Revision 0, dated November 11, 2003.
This report is being submitted pursuant to 10 CFR 50.73(a)(2)(iv). If you should have any questions, please contact me.
Sincerely, c:
B. S. Mallett, NRC Regional Administrator, Region IV A. B. Wang, NRC Project Manager J. G. Kramer, NRC Senior Resident Inspector INPO Records Center G Employment with Equal Opportunity
Abstract
During a reactor shutdown in preparation for a refueling outage, the power reduction was stopped because the operators were unable to maintain the axial shape index (ASI) within the expected band. In order to minimize the operational challenge, management provided two reactor trip criteria. At 2037, with the power reduction close to a nominal 15 percent power, it was noted that ASI might not be maintained within the required margin if the shutdown continued. At 2055 on September 12, 2003, Operations determined that a reactor trip was required because one of management's reactor trip criteria was about to be met. The reactor operators were directed to trip the reactor using the manual pushbutton. A four (4) hour non-emergency report was made to the NRC Operations Center at 0010 CDT on September 13, 2003, pursuant to 10 CFR 50.72(b)(2)(iv). This report is being made pursuant to 10 CFR 50.73(a)(2)(iv).
No formally approved written guidance was provided to the operator and therefore this event is reportable.
Management failed to recognize that a manual trip of the reactor without a change to the shutdown procedure would be reportable.
Appropriate procedural revisions to allow the flexibility in plant procedures to allow a manual reactor trip from power levels greater than 2 percent are being processed.
Al NRCM FOURM 36 (7 2W)
(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
SAFETY SIGNIFICANCE
The manual reactor trip is not significant to nuclear safety because a manual reactor trip is an analyzed action appropriately incorporated into design analyses and FCS design bases. Although the trip challenges plant equipment to respond, all structures, systems and components (SSCs) responded appropriately, and the trip was uncomplicated.
While there is a slight increase in core damage risk due to a manual reactor trip, this risk is largely associated with higher power levels (above 50 percent). The relatively low power level of the reactor prior to the trip (15 percent) contributes to the conclusion that the event was non-safety significant. No reactor safety functions were challenged during the event.
In addition, the magnitude of the ASI transient experienced during the plant down-power was within the reactor's specified design parameters and all design analyses remained valid.
CONCLUSION Plant management had carefully considered the challenges that the operating crews were experiencing with controlling ASI during the plant shutdown. The option of tripping the reactor, as well as other options, were discussed in detail during the management meetings conducted during the shutdown. Nuclear engineering personnel were consulted to determine if any options were being overlooked. After due consideration to the safety and effectiveness of the various shutdown options to meet the plant shutdown objectives, two shutdown criteria were developed as previously mentioned. Management failed to recognize that a manual trip of the reactor without a change to the shutdown procedure would be reportable in accordance with NUREG 1022, revision 2. No formally approved written guidance was provided to the operators. Therefore, this event is reportable.
CORRECTIVE ACTIONS
Appropriate procedural revisions to allow the flexibility in plant procedures to allow a manual reactor trip from power levels greater than 2 percent is being processed. Other corrective actions to preclude similar situations will be implemented by the plants corrective action system.
SAFETY SYSTEM FUNCTIONAL FAILURE This event did not result in a safety system functional failure in accordance with NEI 99-02.
PREVIOUS SIMILAR EVENTS
The plant has not experienced any similar problems.
NHU FURM 366A (1 20U1)