05000483/LER-2001-005
| Docket Number | |
| Event date: | 09-17-2001 |
|---|---|
| Report date: | 11-9-2001 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4832001005R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
This Licensee Event Report (LER) is submitted because of an incident that resulted in an Auxiliary Feedwater Actuation Signal (AFAS) being generated, which started both Motor Driven Auxiliary Feedwater Pumps (MDAFP).
This event was classified as an 8-hour Reportable Event per 10CFR50.72(b)(3)(iv)(A) and reported as NRC Event Number 38291. This event is also reportable as an LER per 10CFR50.73(a)(2)(iv)(A) "Any event or condition that resulted in manual or automatic actuation of the systems listed in paragraph (a)(2)(iv)(B)..." which includes PWR auxiliary feedwater systems.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
On 9/17/01, when this event occurred, the Callaway Plant was in Mode I operating at 100 percent Reactor Power.
C. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE INOPERABLE AT THE
START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT
There were no Inoperable structures, systems, or components that contributed to this event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES
On 9/17/01 Workman's Protection Assurance (WPA) tagging was being placed to support a scheduled inspection of non-safety related battery PK01. A Non Licensed Operator (NLO) was cross-tying non-safety related DC busses PKOI and PK02 in accordance with plant procedures to complete the installation of the WPA. During this evolution, at 1207, power to PK01 was inadvertently lost when a fusible disconnect operated by the NLO did not close completely.
With the loss of power to PKOI, an Auxiliary Feedwater Actuation Signal (AFAS) was generated, Steam Generator (S/G) Blowdown isolated, Reactor (Rx) Coolant Letdown isolated, and multiple Main Control Board (MCB) alarms were generated.
The AFAS was generated due to two Main Feedwater Pump (MFP) Lube Oil pressure switches losing power.
This was sensed as a loss of lube oil on each MFP, which is indicative of a loss of the Main Feed Pumps. When the AFAS was generated, it caused both MDAFPs to start and supply water from the Condensate Storage Tank to the Steam Generators. The AFAS also generated the S/G Blowdown isolation signal.
When PK01 was de-energized, power was lost to distribution bus PK51 which supplies DC control power to the two Rx Coolant Letdown isolation valves, which caused the Letdown Isolation Valves to fail closed.
During this event, Rx power increased as a result of the injection of Auxiliary Feedwater at a temperature colder than that being supplied by Main Feedwater, with the entire transient lasting approximately 45 minutes. Rx power peaked at 3607.2 Megawatts Thermal (MWT), or 101.18 percent Rx power, and was then stabilized at 3563.7 MWT (99.96 percent Rx power). Rx power was at 101.18 percent for less than 1 minute, between 100.5 and 101 percent Rx power for approximately 3 minutes, and between 100 and 100.5 percent Rx power for approximately 40 minutes. The 8-hour MWT Rx power average was within limits as defined in NRC Inspection Manual, Inspection Procedure 61706, which states: "It is permissible to briefly exceed the 'full, steady-state licensed power level' (3565 MWT for Callaway) by as much as 2 percent for as long as 15 minutes. In no case should 102 percent power be exceeded, but lesser power 'excursions' for longer periods should be allowed, with the above as guidance. For example, 1 percent excess for 30 minutes and '/2 percent for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> should be allowed. There are no limits on the number of times these 'excursions' may occur, or the time interval that must separate such 'excursions'. The above requirement regarding the 8-hour average power will prevent abuse of this allowance.
E. METHOD OF DISCOVERY OF EACH COMPONENT, SYSTEM FAILURE, OR PROCEDURAL ERROR
Electrical power was inadvertently interrupted to PKO I while aligning electrical power sources to PKO I in preparation for battery inspections. Upon loss of electrical power to PKOI, numerous alarms were generated and several pieces of equipment either started or repositioned. These indications, along with the NLO contacting the Control Room, were the initial method of discovery of the event.
II. � EVENT DRIVEN INFORMATION
A. SAFETY SYSTEMS THAT RESPONDED
An Auxiliary Feedwater Actuation Signal (AFAS) was generated and both Motor Driven Auxiliary Feedwater Pumps started.
Steam Generator Blowdown isolated as a result of the AFAS.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
No Safety Systems were made Inoperable as a result of this event.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT
An evaluation was performed to estimate the risk incurred due to the event described in this LER. The estimated incremental conditional core damage probability (ICCDP) incurred, due to this event, was determined to be significantly below 1E-6. Therefore, this event was not risk significant.
III. � CAUSE OF THE EVENT The root cause of the event was identified to be inadequate procedural guidance. The procedure did not adequately verify that the bus had been properly transferred.
IV. CORRECTIVE ACTIONS
The procedure for this evolution has been revised to provide additional guidance for verifying bus transfer. In addition, other procedures will be reviewed for similar improvements.
V. PREVIOUS SIMILAR EVENTS
A review of previous LERs from 1998 until present and Callaway Action Request (CAR) documents starting with 199801000 until present revealed no similar events.
FACILITY NAME (1) DOCKET (2) LER NUMBER (6) PAGE (3) Callaway Plant Unit 1 YEAR 05000 2001 _ 005 _ 00 4 � of � 4 VI. � ADDITIONAL INFORMATION The system and component codes listed below are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 respectively.
System: � El Component: DISC