05000397/LER-2013-002
| Docket Number | |
| Event date: | 03-02-2013 |
|---|---|
| Report date: | 05-01-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3972013002R00 - NRC Website | |
NTINUATION SHEET
t MOM 1. ;ALIT') NAME It -41 3. PAGE Columbia Generating Station 40"
PLANT CONDITIONS
At the time of event, the plant was operating in Mode 1 at 100% power.
EVENT DESCRIPTION
In October 2012, it was determined that the Technical Specification (TS) surveillance procedure to verify that each control room air conditioning (AC) subsystem (NI) has the capability to remove the assumed heat load for TS Surveillance Requirement (SR) 3.7.4.1 did not satisfy the surveillance requirement. The methodology for the existing surveillance had been in use since 1998 around the time Energy Northwest converted to the Improved Technical Specifications. TS SR 3.0.3 was invoked. An informational test was performed on November 3, 2012, indicating acceptable performance of the cooler (CLRj. A new surveillance procedure was developed and on March 2, 2013, while performing the new surveillance, the test results revealed that the air handler thermal performance for the "A" train did not meet the acceptance criteria. This failure to satisfy SR 3.7.4.1 in March, following entry into SR 3.0.3, is reportable under 10 CFR 50.73(a)(2)(1)(8) - Any operation or condition which was prohibited by the plant's technical specifications.
IMMEDIATE CORRECTIVE ACTION
- Addition of Hydrogen Peroxide to the service water spray ponds to kill biological material in the cooling water.
- Cleaning and Inspection of the air side of the cooling coils.
- Cleaning, flushing and inspection of the water side of the cooling coils (CCLI
- Adjustment of the water flow to balance coil flow and heat removal capacity.
A final performance of the test on March 21, 2013 demonstrated heat removal capacity significantly above the minimum acceptance criteria.
CAUSE
The direct cause was determined to be macro-fouling of the water side of the tubes. The presence of large anode deposits, due to degradation of the zinc sacrificial anode, and sediment in the lower tubes of the cooling coils were blocking flow.
The apparent cause was lack of a periodic performance test. With no component specific periodic performance test specified timely identification of degradation, and subsequent action to mitigate the degradation, was not possible to prevent component failure. No routine surveillance on this cooler had been performed for 16 years.
Contributing to this failure was a lack of procedural guidance to balance flow through the cooling coils. The control room coolers are unique in that they are the only double coil coolers used for service water systems RI]. There is no flow indication for the individual coils, only the total flow. Thermal performance testing found that flow was not property balanced between the coils.
Another contributing cause was a general Increase in the sediment levels of the service water system.
26158 R5 6. LER LASER 3. PAGE 1. FACILITi NiAik 2. OoCIEET'
- Columbia Generating Station 05000397
FURTHER CORRECTIVE ACTION
The surveillance procedure for the control room cooler will be scheduled and performed on a routine basis.
Develop periodic inspection, cleaning, and anode replacement plan for all coolers.
ASSESSMENT OF SAFETY CONSEQUENCES
The main control room has two divisions of air handling units, each with the capability to maintain temperatures within the required limits during accident conditions. The main control room air coolers are required to have a minimum efficiency of 65% to provide the required cooling for a design basis event. In November 2012, the measured efficiency of the "A" train AC was 67% as obtained by a maintenance test. The measured efficiency for the "A" train AC in March 2013 was 62.6%. The "B" train AC efficiency was greater than 65%. The "B" train AC was fully capable of maintaining required control room temperatures. The "A" train AC was stilt capable of providing adequate cooling for most situations. Since November 2012 the "B" train was not been available for service on three occasions each with an outage duration of less than *I day. During these times the "A" train would still have been capable of maintaining the control room within the required limits due to actual conditions being significantly less than design basis conditions (ambient temperature of 105°F and service water temperature of 77°F).
In addition to the coolers utilizing service water, the main control room AC subsystem also has the capability to be aligned to emergency chillers (KM), which provide additional cooling capability. Each division of the main control room air handler has two sets of coolers. One emergency cooler and one for normal HVAC. Both emergency coolers can be lined up to either service water or an emergency chiller, a clean closed-loop system. Typically, the "A" train Is lined up to service water and the "B" train to an emergency chiller.
The safety significance of one main control room cooler having a slightly reduced efficiency was minimal.
SIMILAR EVENTS
A review of various databases at Columbia found no similar issues of a component not being tested per surveillance.
ENERGY INDUSTRY IDENTIFICATION SYSTEM (ENS) INFORMATION CODES BS codes are bracketed Q Moro appkable In the narrative.
26158 R5