05000336/LER-2006-005

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LER-2006-005, Inadvertent Actuation of 'A' Motor Driven Auxiliary Feedwater Pump
Docket Number
Event date: 05-02-2006
Report date: 06-30-2006
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(B), System Actuation

10 CFR 50.73(a)(2)(iv)(A), System Actuation
3362006005R00 - NRC Website

1. Event Description Millstone Power Station (MPS) Unit 2 Auxiliary Feedwater (AFW) System [BA] consists of two Motor Driven Auxiliary Feedwater (MDAFW) Pumps [P] and a Turbine Driven Auxiliary Feedwater (TDAFW) Pump [P]. All of the pumps provide feedwater to both of the Steam Generators (SG) [AB]. The normal use of the AFW System is to supply feedwater during plant startups until main feedwater is available. The system also provides for decay heat removal until the Reactor Coolant System (RCS) is placed on Shutdown Cooling. During power operations, the AFW System is aligned for automatic start of the MDAFW Pumps on either low SG level or high Pressurizer (PZR) [AB] pressure.

On May 2, 2006 at approximately 1430, with MPS Unit 2 at 100% power, the 'A' MDAFW pump started after the pump control switch was placed in the 'Normal' position following surveillance testing by Instrument & Controls (I&C) personnel.

The l&C surveillance was being performed to satisfy the monthly Engineering Safety Features (ESF) Channel Functional Test requirements identified in Technical Specification Surveillance Requirement 4.3.2.1.1, Table 4.3-2 for AFW (for SG Low Level and Automatic Actuation Logic) and SG Blowdown (for SG Low Level). In addition, this testing satisfies the monthly Reactor Protection (RPS) Channel Functional Test requirements identified in Technical Specification Surveillance Requirement 4.3.1.1.1, Table 4.3-1 for SG Water Level — Low.

The event occurred during the performance of the Time Delay Relay Test' section of the surveillance. This section verifies that after receiving a start signal from the system logic, the time delay relays initiate a signal to start the 'AM' MDAFW pumps after approximately 3 minutes and 25 seconds. During this relay testing MC personnel failed to remove a jumper as required by the surveillance procedure. This resulted in the 'A' MDAFW pump starting as soon as the operator restored the pump control switch to the 'Normal' position following completion of testing. The operators immediately realized that this was an unexpected response and secured the pump. Since the input parameters for the initiation of automatic auxiliary feedwater (i.e., SG level and PZR pressure), were within the normal ranges, the start signal for the 'A' MDAFW pump was not valid.

The actuation of the `A' MDAFW pump is reportable under the provisions of 10CFR50.73(a)(2)(iv)(A) as an invalid actuation of a system listed in 10CFR50.73(a)(2)(iv)(B).

2. Cause The cause of this event was personnel error in that the l&C technician did not adequately adhere to the requirements of a Continuous Use procedure as defined by the Dominion administrative procedure on procedure adherence and usage. This allowed the technician to miss two restoration steps in the surveillance procedure resulting in the inadvertent start of the 'A' MDAFW pump.

3. Assessment of Safety Consequences The AFW System is normally used to supply feedwater during plant startups until main feedwater is available. The system also provides for decay heat removal until the RCS is placed on Shutdown Cooling. During power operations, the AFW System is aligned for automatic initiation on either low SG level or high PZR pressure. The AFW Pumps pump cold water into the SG from the condensate storage tank (CST). This could have lowered reactor coolant temperatures, causing a corresponding drop in PZR level and pressure. Additionally, the cooler RCS water could have added positive reactivity to the core, potentially causing a power excursion, however the operators immediately realized what had occurred and secured the pump within 30 seconds of the pump start.

Therefore, there were no safety consequences associated with this event.

4. Corrective Action Corrective actions are being taken in accordance with the station's corrective action program.

5. Previous Occurrences None Energy Industry Identification System (EIIS) codes are identified in the text as [XX].