05000302/LER-2001-005
| Crystal River Unit 3 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| 3022001005R01 - NRC Website | |
DESCRIPTION
On October 24, 2001, Florida Power Corporation's (FPC) Crystal River Unit 3 (CR-3) was in MODE 3 (HOT STANDBY) at 0 percent RATED THERMAL POWER preparing for a reactor startup. Reactor coolant system (RCS) [AB] temperature was 531 degrees Fahrenheit and RCS pressure was 2125 pounds per square inch gauge. Once through steam generator (OTSG) [SB, HX] levels were being maintained by the "B" steam-driven main feedwater pump (FWP-2B) [SJ, P]. Auxiliary steam (AS) [SA] (motive steam) to FWP-2B was being supplied from the Crystal River Unit 1 (CR-1) coal-fired plant. The Crystal River Unit 2 (CR-2) coal-fired plant, which can also supply AS to CR-3, was in a scheduled maintenance outage. At approximately 1000, CR-1 tripped causing a loss of AS to FWP-2B. The loss of steam caused the pump to slow down, resulting in a loss of main feedwater (FW) [SJ] and the subsequent actuation of the emergency feedwater system (EFW) [BA] on low OTSG levels. CR-1 was restarted and AS from CR-1 was restored to CR-3 at approximately 1643. FW was reestablished to the OTSGs and EFW was secured at approximately 1748.
At 1341, on October 24, 2001, a non-emergency eight-hour notification was made to the NRC Operations Center (Event Number 38422) in accordance with 10CFR50.72(b)(3)(iv)(A) as an event that resulted in automatic actuation of the emergency feedwater system. This report is being submitted pursuant to 10CFR50.73(a)(2)(iv)(A).
CAUSE
The cause of the event was the unexpected loss of the only available source of AS during plant startup. A contributing cause is the dependency of CR-3 on external sources of AS when the plant is shutdown.
SAFETY CONSEQUENCES
The main feedwater pumps at CR-3 are steam turbine driven. At high power levels (>80 percent RATED THERMAL POWER) the main feedwater pump turbines are normally supplied from reheat steam (RH) [SB]; at lower power levels and shutdown conditions the turbines are supplied from AS. When the plant is at >1=10 percent RATED THERMAL POWER, the source of AS is the main steam system (MS) [SB]. When the plant is shutdown or operating at percent RATED THERMAL POWER, the source of AS is cold reheat steam from CR-1 or CR-2.
With CR-2 shutdown for maintenance and CR-3 in HOT STANDBY at the time of the event, CR-1 was the only source of AS available to provide the motive force for FWP-2B and supply the gland steam (GS) [TC] needed to maintain condenser [SG, COND] vacuum. The unexpected trip of CR-1 and loss of AS caused FWP-2B to slow down and stop feeding the OTSGs, resulting in an EFW actuation on low OTSG levels. EFW actuated and operated as designed. The steam driven emergency feedwater pump (EFP-2) [BA, P] and diesel emergency feedwater pump (EFP-3) started and restored levels in the OTSGs. OTSG levels remained on scale throughout the event. The loss of AS also resulted in a loss of GS and decreasing condenser vacuum. The control room operators realigned the GS supply from AS to MS, which restored GS and condenser vacuum.
When CR-3 is in MODE 3, the heat input to the RCS is limited to that provided by the operating reactor coolant pumps (RCP) [AB, P1 and core decay heat. With the plant supplying EFP-2 and the steam loads that had been supplied from CR-1 prior to the trip of the unit, this heat input was not sufficient to maintain RCS temperature. In response to the decreasing RCS temperature, the control room staff appropriately secured EFP-2 and minimized other plant steam loads, allowing RCS temperature to return to its pre-event value. EFP-3 was used to supply EFW to the OTSGs until AS from CR-1 was restored and FW was reestablished to the OTSGs using FWP-2B.
Based on the above information, this event did not represent a reduction in the public health and safety. This event does not meet the definition of a Safety System Functional Failure.
CORRECTIVE ACTIONS
The plant was stabilized in MODE 3 (HOT STANDBY).
CR-3 will not normally schedule an outage simultaneous with a scheduled outage of either CR-1 or CR-2. Should an equipment issue at CR-3 raise the need for an outage, CR-3 will balance the risk and benefit of available outage schedule windows. If a CR-3 outage is necessary when either CR-1 or CR-2 is shutdown, CR-3 will establish restrictions on activities which would reduce the availability of systems required to respond to a loss of FW while the FW Pumps are operating on Auxiliary Steam.
PREVIOUS SIMILAR EVENTS
There have been two previous similar events at CR-3 involving EFW actuations due to a loss of FW.
Emergency Feedwater Actuation
ATTACHMENTS
Attachment 1 - Abbreviations, Definitions, and Acronyms Attachment 2 - List of Commitments ..._ .. � :-.-■-
- ATTACHMENT 1
ABBREVIATIONS, DEFINITIONS, AND ACRONYMS
10CFR � Title 10 of the Code of Federal Regulations AS � Auxiliary Steam EFP � Emergency Feedwater Pump EFW � Emergency Feedwater System FPC � Florida Power Corporation FW � Main Feedwater FW P � Main Feedwater Pump GS � Gland Steam MS � Main Steam OTSG � Once Through Steam Generator RCP � Reactor Coolant Pump RCS � Reactor Coolant System RH � Reheat Steam Note: Improved Technical Specifications terms appear in capitalization in the text of the LER. EIIS Codes appear in square brackets. Defined terms / acronyms / abbreviations appear in parentheses when first used.
ATTACHMENT 2
LIST OF COMMITMENTS
The following table identifies those actions committed to by Florida Power Corporation in this document. Any other actions discussed in the submittal represent intended or planned actions by Florida Power Corporation. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify the Supervisor, Licensing & Regulatory Programs of any questions regarding this document or any associated regulatory commitments.
RESPONSE
SECTION
COMMITMENT DUE DATE
No regulatory commitments are made in this submittal.