05000483/LER-2004-005
| Callaway Plant Unit 1 | |
| Event date: | 2-15-2004 |
|---|---|
| Report date: | 4-9-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4832004005R00 - NRC Website | |
I. � DESCRIPTION OF THE REPORTABLE EVENT system actuation.
EVENT
the main turbine generator to the from the Main Feedwater Regulating Bypass
THAT WERE INOPERABLE AT THE
TO THE EVENT
DATES AND APPROXIMATE TIMES
the main turbine generator to the procedure OTG-ZZ-00003, PLANT STARTUP instructions for plant operations necessary to chest and shell warming had been to High Pressure Feedwater Heaters 6A, 6B, OTG-ZZ-00003 and OTN-AF-00001, HIGH SYSTEM, extraction steam had not been the main turbine generator was paralleled with and MDV55. Reactor power was increased as Steam Generator (S/G) feedwater (MFRBV) to the Main Feedwater Regulating feedwater temperature, which had been in temperature of 99 degrees F in 18 loading and S/G levels be stable before time was allowed for S/G levels and main feedwater supply alteration. S/G levels began to those in the remaining two S/G's. At setpoint (P14) and caused a main turbine isolation, and a motor-driven auxiliary feedwater the Control Room staff entered OTO-AC- reactor power by inserting control rods, and Pump (TDAFP) was started manually to Pumps (MDAFP) that had started upon S/G levels. Despite these efforts, at 1524 the REACTOR TRIP OR SAFETY INJECTION.
that an excessive cooldown was in REACTOR TRIP RESPONSE. Directions
A. REPORTABLE EVENT CLASSIFICATION
This event is being reported per 10CFR50.73(a)(2)(iv)(A),
B. PLANT OPERATING CONDITIONS PRIOR TO THE
Callaway Plant was in Mode 1 having just completed synchronizing electrical grid, and preparations were underway to transfer Valves to the Main Feedwater Regulating Valves.
C. STATUS OF STRUCTURES, SYSTEMS OR COMPONENTS
START OF THE EVENT AND THAT CONTRIBUTED
None.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING
On 2/15/04, Callaway Plant was in the process of synchronizing electrical grid and increasing power to 30 percent using HOT ZERO POWER TO 30% POWER, which provides increase power from 0 percent up to 30 percent. Main turbine completed and feed water preheating had been established 7A, and 7B. Due to inconsistent guidance between procedure
PRESSURE AND LOW PRESSURE FEEDWATER HEATER
aligned to the High Pressure Feedwater Heaters. At 1456 the electrical grid by closing switchyard breakers MDV53 main generator loading was raised in preparation for transferring supply from the Main Feedwater Regulating Bypass Valves Valves (MFRV).
Four minutes after synchronizing with the electrical grid, approximately 323 degrees F, experienced a rapid decrease minutes. Procedure guidance directed that main generator beginning the transition. � Despite this guidance, insufficient generator loading to stabilize prior to commencing the S/G oscillating with levels in two S/G's cycling in opposite directions 1519, the level in "C" S/G reached a high-high level trip generator trip, main feedwater isolation, S/G blowdown (MDAFW) actuation. Upon trip of the main turbine generator, 00001, TURBINE TRIP. Actions were commenced to reduce immediate borating. The Turbine Driven Auxiliary Feedwater assist the two operating Motor Driven Auxiliary Feedwater receiving the previous AFW actuation signal, in maintaining reactor tripped on low S/G water level.
Plant operators transitioned to emergency procedure E-0, After completing the initial actions required, it was recognized progress and the Control Room staff transitioned to ES-0.1, were given to throttle auxiliary feedwater to the S/G's, ensure the S/G atmospheric dumps were closed, and secure the TDAFP. All of these actions were accomplished, but when the operators secured the TDAFP steam supplies, those valves immediately reopened. At this point, the operators realized that a Trip Time Delay (TTD) circuit had actuated earlier when multiple S/G low-low level signals had been present simultaneously, and that with this signal still present, the TDAFP would automatically restart.
When the TDAFP steam supply valves re-opened, the TDAFP tripped on both electrical and mechanical overspeed. After securing all unnecessary steam loads and throttling AFW to the S/G, the excessive cooldown situation was corrected, and a normal recovery from a plant trip was completed.
During post trip investigations:
- It was determined that without extraction steam aligned to the high pressure feedwater heaters, insufficient feedwater heating would occur which in turn would result in the excessive S/G level oscillations experienced.
- It was determined that the overspeed trip of the TDAFP was an expected result from the method operators used in trying to secure the TDAFP. With a TDAFP actuation signal present, when the operators manually stopped the TDAFP, the trip and throttle valve began closing, however, the governor valve started opening in an effort to maintain rated speed. When the trip and throttle valve stroked shut, it automatically reset and reopened due to the existing TDAFP actuation signal still present. The governor valve control circuitry had not reached its reset value which would allow control of the pump during startup. Therefore, with the trip and throttle valve opening, the supply of steam was sufficient to overspeed the TDAFP.
E. METHOD OF DISCOVERY OF EACH COMPONENT, SYSTEM FAILURE, OR PROCEDURAL ERROR
The main turbine generator trip was recognized by the Control Room staff due to Main Control Board (MCB) alarm and display indications.
The reactor trip was also recognized by the Control Room staff due to additional MCB alarm and display indications.
Control room operator recognized that the TDAFP was tripped when the normal lamp indication was absent on the MCB.
II. � EVENT DRIVEN INFORMATION
A. SAFETY SYSTEMS THAT RESPONDED
The Reactor Protection System and Auxiliary Feedwater System both were actuated as a result of conditions experienced during this event.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
No safety system was inoperable during this event. The two motor-driven auxiliary feedwater trains remained operable and supplied sufficient auxiliary feedwater throughout this event.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT.
A probabilistic .risk assessment (PRA) determined that the reported event was of very low risk significance.
III. CAUSE OF THE EVENT
A multi-disciplinary Root Cause Analysis (RCA) team was assembled to investigate this event. This RCA team was conducted for both LER 2004-004-00 and 2004-005-00. These two events were found to have related root causes and corrective actions. The RCA team conclusions for this event were:
Root Cause 01 (RC-1) Policy Guidance regarding Pre-Job Briefs is not strict enough and allows interpretation, resulting in varying degrees of quality of Pre-job Briefs.
Root Cause 02 (RC-2) Operations supervisory oversight and standards reinforcement need improvement.
Root Cause 03 (RC-3) Training coursework needs to be improved in the areas of operating Secondary Plant and situational awareness of indications.
Root Cause 04 (RC-4) General Operating procedures (OTGs) are cumbersome and difficult to follow.
IV. CORRECTIVE ACTIONS
The following Corrective Actions were developed by the RCA team. Corrective Actions to Prevent Recurrence (CATPR) are actions that will be taken in order to prevent a similar event from occurring in the future.
CATPR 01 Expectations for Pre-Job Briefs (PJB) have been strengthened in Operations. � The Plant Manager and Superintendent of Operations conducted briefings with each crew affirming the expectations for pre-job briefs. The Shift Supervisors and Operations management conducted an all-day performance review meeting where the expectation for performing pre-job briefs was reaffirmed. In addition, the Senior Reactor Operators met as a group and discussed the importance and expectations of pre-job briefs.
Improved site-wide guidance for pre-job briefs is being evaluated for implementation.
CATPR 02 The Shift Supervisor and Senior Reactor Operator meetings discussed under CATPR 01 also emphasized the following Operations standards:
- Ensure the level of supervisory oversight compensates for infrequency of evolutions, experience level of crew members, and evolutions of high consequence.
- Ensure standards address the roles and responsibilities of crew members and supervisors.
- Ensure leadership is engaged and is conducting observations and coaching personnel.
CATPR 03 Operations and Training are conducting an effectiveness review of the current training courses developed to provide instruction for routine and atypical secondary plant manipulations.
CATPR 04 OTG-ZZ-00003 was revised to clarify the requirements for extraction steam alignment to feedwater heaters prior to rolling the turbine. OTG procedures issues.
V. PREVIOUS SIMILAR EVENTS
are being revised to address layout, formatting, and sequencing are not similar events, the RCA team determined they actions, as discussed previously in this LER.
System (CARS) historical data between 2/15/01 and 2/15/04 and reveal any additional trips of this nature.
determine if there were any similar failures of the TDAFP. No occurred as a result of operator actions while an actuation signal 2001 until present did not document any similar LERs.
below are from the IEEE Standard 805-1984 and IEEE Standard were no component failures associated with this event.
Even though LER 2004-004-00 and 2004-005-00 have related root causes and corrective A review of the Callaway Action Request searching for similar reactor trips did not A similar CARS review was conducted to CARs were identified where a TDAFP trip was present.
A historical review of Callaway LERs from
VI. ADDITIONAL INFORMATION
The system and component codes listed 803A-1984 respectively.
System: � Not applicable. There Component: � N/A