05000311/LER-2007-001

LER-2007-001, Inoperability of the Chilled Water System - (21 and 22 Chillers Inoperable)

Docket Number
Event date:	05-01-2007
Report date:	06-29-2007
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3112007001R00 - NRC Website

PLANT AND SYSTEM IDENTIFICATION

Westinghouse — Pressurized Water Reactor (PWR/4) Chilled Water System {KM} Chiller Unit {CHU} Position Switch {33} * Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}

IDENTIFICATION OF OCCURRENCE

Event Date: May 1, 2007 Discovery Date: May 1, 2007

CONDITIONS PRIOR TO OCCURRENCE

Salem Unit 2 was in Operational Mode 1 at 100% reactor power.

No structures, systems or components, other than described below, were inoperable at the time of the discovery that contributed to the event.

DESCRIPTION OF OCCURRENCE

On April 25, 2007, at 2013, the 22 Chiller was declared inoperable due to emergent maintenance, and Technical Specification (TS) 3/4.7.10 "Chilled Water System" Action a was entered. TS 3/4.7.10 Action a allows continued operation for fourteen (14) days for one inoperable chiller {CHU} provided the appropriate non-essential heat loads are removed from the chilled water system within four (4) hours.

On May 1, 2007 at approximately 1500, the 22 Chiller was being returned to Operations for post­ maintenance testing, and 21, 22, and 23 Chillers were placed in the 'pump down' mode in preparation for loading the chiller under test. The 22 Chiller did not complete the pump down cycle and in accordance with surveillance test procedure the 22 Chiller was placed in 'off' (lockout). 22 Chiller remained inoperable for failing to complete the pump down cycle. The licensed control room supervisor (CRS) directed a non-licensed equipment operator to place the 21 and 23 Chillers in the 'run' mode (i.e.

ready to accept load as necessary depending on a pre-determined temperature setpoint). Later that day at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, the non-licensed Primary Duty Operator (PDO) noted that the 21 Chiller was not operating. The 21 Chiller should have been in service based on the chilled water system outlet temperature. The PDO realigned the chiller sequence switches in accordance with procedural guidance in an attempt to start the chiller, but it was unsuccessful.

�NRC FORM 366 (6-2004) PRINTED ON RECYCLED PAPER DESCRIPTION OF OCCURRENCE (Continued) The 21 Chiller was declared inoperable at 2130 on May 1, 2007 and TS 3/4.7.10 Action b was entered.

In addition to removing appropriate non-essential heat loads from the chilled water system, TS 3/4.7.10 Action b requires that the CREACS be placed in single filtration operation within four (4) hours and to restore one chiller to operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. All TS required actions were completed within the required allowable time by TS 3/4.7.10 Action b from 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br />.

Upon further investigation and review, the 21 Chiller was determined to have been inoperable since approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on May 1, 2007 when the 21 Chiller switch was to be placed in the 'run' mode. With 21 and 22 Chillers inoperable at 1500, the CREACS was not placed in single filtration within four (4) hours as required by TS.

This report is being made in accordance with 10CFR50.73(a)(2)(i)(B), "Operation or Condition Prohibited by Technical Specification.

21 Chiller was repaired and returned to operable status at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on May 2, 2007 and TS 3/4.7.10 Action b was terminated.

22 Chiller was returned to operable status at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on May 4, 2007.

PREVIOUS OCCURRENCES

A review of LERs at Salem Station back to 2004 identified one previous similar occurrence, LER 272/2004-004 "Non-Essential Loads Not Isolated With One Chiller Inoperable as Required by Technical Specifications," issued on September 20, 2004. The cause of this LER was multiple human errors associated with valve mispositioning and was attributed to a lack of attention to detail. The corrective actions associated with LER 272/2004-004 were specific to that event and they would not have prevented this LER.

CAUSE OF OCCURRENCE

The cause of the 21 Chiller key switch being in the 'pump down' position instead of the 'run' position was a loose key switch barrel in its mounting hole. This allowed the body of the switch to rotate to indicate 'run,' while electrically the switch remained in the pump down position.

SAFETY CONSEQUENCES AND IMPLICATIONS

There were no actual safety consequences associated with this event.

Although the opposite unit CREACS was not placed in single train filtration in accordance with TS for having two inoperable chillers, the ability of the system to perform its safety function was not compromised. Placing the opposite unit CREACS in single train filtration means that the airflow through the affected unit is being circulated with the opposite unit's fans to minimize the heat load in the affected unit.

At the time of the event, some non-essential heat loads had been removed from service as a result of 22 Chiller being inoperable, and the environmental condition (river water temperature) at the beginning of May was not near the 80 °F assumed in the accident analysis. Therefore, the significance of not having placed the CREACS in single train filtration was minimal.

A review of this event determined that a Safety System Functional Failure (SSFF) as defined in NEI 99- 02, Regulatory Assessment Performance Indicator Guidelines, did not occur. There was no condition that alone could have prevented the fulfillment of a safety function of a system needed to remove residual heat.

CORRECTIVE ACTIONS

1. 21 Chiller key switch was repaired and the chiller was returned to operable at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on May 2, 2007. TS 3/4.7.10 Action b was terminated.

2. The key switch mountings for all of the chillers on Unit 1 and 2 were verified to be in proper operating condition.

3. This event was discussed for lessons learned at Operation's shift briefings.

4. This event and lessons learned will be presented to the training committee for inclusion in the operators' training.

COMMITMENTS

No commitments are made in this LER.