05000483/LER-2004-005, Inadequate Feedwater Heating During Plant Startup Causes Turbine Trip and Subsequent Reactor Trip
| ML041110926 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 04/09/2004 |
| From: | Witt W AmerenUE |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC04980 LER 04-005-00 | |
| Download: ML041110926 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4832004005R00 - NRC Website | |
text
AmerenUE Ca//away Plant PO Box 620 Fulton, MO 65251 April 9, 2004 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 ULNRC04980
"'Ameren UE DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2004-005-00 Inadequate feedwater heating during plant startup causes turbine trip and subsequent reactor trip.
Ladies and Gentlemen:
The enclosed licensee event report is submitted in accordance with 1 OCFR50.73(a)(2)(iv)(A), to report an event where inadequate feedwater preheating during a plant startup causes a main turbine generator trip and subsequent reactor trip.
Sincerely, Warren A. Witt Manager, Callaway Plant Enclosure
.1 C-
a
a subsidiary of Ameren Corporation
ULNRC04980 April 9, 2004 Page 2 Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)
Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360 Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339
Abstract
On 2/15/04, during plant startup and synchronizing to the grid, Callaway experienced oscillations in Steam Generator (S/G) levels which resulted in a main turbine generator trip and subsequent reactor trip. After the reactor trip occurred, to reduce the plant cooldown rate, operators attempted to secure the Turbine Driven Auxiliary Feedwater Pump (TDAFP). However, due to an automatic actuation signal being present, the TDAFP experienced an electrical and mechanical overspeed trip.
Post trip investigations determined that the SIG oscillations were due to not having aligned extraction steam to provide feedwater preheating. The overspeed trip of the TDAFP was per system design. A TDAFP actuation signal was present when the operators closed the steam supply valves, causing the valves to reopen automatically and in such a sequence as to cause an overspeed condition.
A Root Cause Analysis team was assembled and identified four Root Causes, plus several Corrective Actions to Prevent Occurrence.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On 2/15/04, Callaway Plant was in the process of synchronizing the main turbine generator to the electrical grid and increasing power to 30 percent using procedure OTG-ZZ-00003, PLANT STARTUP HOT ZERO POWER TO 30% POWER, which provides instructions for plant operations necessary to increase power from 0 percent up to 30 percent. Main turbine chest and shell warming had been completed and feed water preheating had been established to High Pressure Feedwater Heaters 6A, 6B, 7A, and 7B. Due to inconsistent guidance between procedure OTG-ZZ-00003 and OTN-AF-00001, HIGH PRESSURE AND LOW PRESSURE FEEDWATER HEATER SYSTEM, extraction steam had not been aligned to the High Pressure Feedwater Heaters. At 1456 the main turbine generator was paralleled with the electrical grid by closing switchyard breakers MDV53 and MDV55. Reactor power was increased as main generator loading was raised in preparation for transferring Steam Generator (S/G) feedwater supply from the Main Feedwater Regulating Bypass Valves (MFRBV) to the Main Feedwater Regulating Valves (MFRV).
Four minutes after synchronizing with the electrical grid, feedwater temperature, which had been approximately 323 degrees F, experienced a rapid decrease in temperature of 99 degrees F in 18 minutes. Procedure guidance directed that main generator loading and S/G levels be stable before beginning the transition. Despite this guidance, insufficient time was allowed for S/G levels and main generator loading to stabilize prior to commencing the S/G feedwater supply alteration. S/G levels began oscillating with levels in two S/G's cycling in opposite directions to those in the remaining two S/G's. At 1519, the level in "C" S/G reached a high-high level trip setpoint (P14) and caused a main turbine generator trip, main feedwater isolation, S/G blowdown isolation, and a motor-driven auxiliary feedwater (MDAFW) actuation. Upon trip of the main turbine generator, the Control Room staff entered OTO-AC-00001, TURBINE TRIP. Actions were commenced to reduce reactor power by inserting control rods, and immediate borating. The Turbine Driven Auxiliary Feedwater Pump (TDAFP) was started manually to assist the two operating Motor Driven Auxiliary Feedwater Pumps (MDAFP) that had started upon receiving the previous AFW actuation signal, in maintaining S/G levels. Despite these efforts, at 1524 the reactor tripped on low S/G water level.
Plant operators transitioned to emergency procedure E-0, REACTOR TRIP OR SAFETY INJECTION.
After completing the initial actions required, it was recognized that an excessive cooldown was in progress and the Control Room staff transitioned to ES-0.1, REACTOR TRIP RESPONSE. Directions (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17) prior to rolling the turbine. OTG procedures are being revised to address layout, formatting, and sequencing issues.
V.
PREVIOUS SIMILAR EVENTS
Even though LER 2004-004-00 and 2004-005-00 are not similar events, the RCA team determined they have related root causes and corrective actions, as discussed previously in this LER.
A review of the Callaway Action Request System (CARS) historical data between 2/15/01 and 2/15/04 and searching for similar reactor trips did not reveal any additional trips of this nature.
A similar CARS review was conducted to determine if there were any similar failures of the TDAFP. No CARs were identified where a TDAFP trip occurred as a result of operator actions while an actuation signal was present.
A historical review of Callaway LERs from 2001 until present did not document any similar LERs.
VI.
ADDITIONAL INFORMATION
The system and component codes listed below are from the IEEE Standard 805-1984 and IEEE Standard 803A-1 984 respectively.
System:
Not applicable. There were no component failures associated with this event.
Component:
N/A