05000305/LER-2011-001

LER-2011-001, Auxiliary Building Special Ventilation Inoperability Results in Prohibited Technical Specification Condition

Kewaunee Power Station
Event date:	12-13-2010
Report date:	02-11-2011
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3052011001R00 - NRC Website

10. POWER LEVEL

100

FACILITY NAME

Brian O'Connell TELEPHONE NUMBER (include Area Code) (920) 388-8174

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT

CAUSE SYSTEM COMPONENT MANU-

REPORTABLE

TO EPIx CAUSE SYSTEM COMPONENT MANU-

TO EPIX

14 SUPPLEMENTAL REPORT EXPECTED

• YES (If yes, complete 15. EXPECTED SUBMISSION DATE) J NO

MONTH DAY YEAR

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On December 13, 2010 with the Station at 100% power, charcoal laboratory radioiodine test results were found to be below the acceptance criteria for Auxiliary Building Special Ventilation Train A, which caused the train to be inoperable for a period that exceeded the Technical Specification allowed outage time.

This occurred because the elapsed time, from removal of the sample to the time the vendor analysis was obtained, plus the time required for corrective actions to be completed to address the condition, exceeded the seven day Technical Specification allowance for one train being inoperable.

Although the charcoal test results were below the minimum charcoal adsorber efficiency required for surveillance test acceptance, the efficiency assumed in the design basis accident analysis continued to be met. Therefore, the system remained capable of performing its specified safety function.

Additionally, there are two trains of Auxiliary Building Special Ventilation and Train B passed its surveillance test. Therefore, there is no safety significance associated with this event.

This event is being reported pursuant to 10 CFR 50.73(a)(2)(i)(B), for any operation or condition which was prohibited by the plant's Technical Specifications.

Event Description:

On December 13, 2010 with the Station at 100% power, charcoal laboratory radioiodine test results were found to be below the acceptance criteria for Auxiliary Building Special Ventilation Train A, which caused the train to be inoperable for a period that exceeded the Technical Specification (TS) allowed outage time. This occurred because the elapsed time, from removal of the sample to the time the vendor analysis was obtained, plus the time required for corrective actions to be completed to address the condition, exceeded the seven day TS allowance for one train being inoperable by eight days.

Technical Specifications Section 4.0 required periodic testing of the Auxiliary Building Special Ventilation System [BD] which included the following:

"The laboratory tests for activated carbon in the charcoal filters shall be performed (1) at least once per 18 months for filters in a standby status or after 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of filter operation, and (2) following painting, fire, or chemical release in any ventilation zone communicating with the system.

Charcoal samples from filter [FLT] banks were removed from the Auxiliary Building Special Ventilation Train A on December 1, 2010. The removed individual charcoal adsorber filter was replaced in the ventilation train with a new filter. The samples were then shipped to a vendor for analysis. On December 13, 2010, the charcoal laboratory radioiodine test results indicated a removal efficiency of 96.589% for the Auxiliary Building Special Ventilation Train A. This was below the TS allowable value of greater than or equal to 97.5%. The TS basis stated that if the iodine removal efficiency test results are unacceptable, all adsorbant [ADS] should be replaced. The remainder of the charcoal adsorber filters were replaced and Auxiliary Building Special Ventilation Train A was returned to an operable status on December 16, 2010.

For the Auxiliary Building Special Ventilation System, TS 3.6, CONTAINMENT SYSTEM, stated the following:

3.6.c. All of the following conditions shall be satisfied whenever CONTAINMENT SYSTEM INTEGRITY, as defined by TS 1.0.g, is required:

1. Both trains of the Shield Building Ventilation System, including filters, shall be OPERABLE or the reactor shall be shut down within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, except that when one of the two trains of the Shield Building Ventilation is made or found to be inoperable for any reason, reactor operation is permissible only during the succeeding 7 days.

2. Both trains of the Auxiliary Building Ventilation System, including filters, shall be OPERABLE or the reactor shall be shut down within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, except that when one of the two trains of the Auxiliary Building Special Ventilation System is made or found to be inoperable for any reason, reactor operation is permissible only during the succeeding 7 days.

At the time the filter was removed on December 1, 2010, there was no indication that the Auxiliary Building Special Ventilation Train A was inoperable. The sample analysis failure identified on December 13th constituted discovery that the Auxiliary Building Special Ventilation Train A exceeded the TS surveillance requirement for charcoal adsorber efficiency. With the charcoal adsorber filter replacement completed on December 16th, there was a 15 day period where the Auxiliary Building Ventilation Train A was considered to not satisfy the surveillance requirement, even though the filters were replaced within the time allowed by TS U.S. NUCLEAR REGULATORY COMMISSION NRC FORM 366A (10-2010) LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

Kewaunee Power Station

2. DOCKET

(from time of discovery). The surveillance criteria were determined to not be met for 15 days thus exceeding the allowed outage time of 7 days.

Therefore, this was a condition prohibited by the plant's TS since the definition of OPERABLE-OPERABILTY was not met. OPERABLE-OPERABILTY stated (in part):

"A system or component is OPERABLE or has OPERABILITY when it is capable of performing its intended function within the required range. The system or component shall be considered to have this capability when: (1) it satisfies the LIMITING CONDITIONS FOR OPERATION defined in TS 3.0, and (2) it has been tested periodically in accordance with TS 4.0 and has met its performance requirements.

Because the surveillance criteria were not met, the LCO was considered not met. With the LCO not satisfied, the TS definition of operability was not met for longer than the 7 day period allowed by TS.

This event is being reported pursuant to 10 CFR 50.73(a)(2)(i)(B), for any operation or condition which was prohibited by the plant's Technical Specifications.

On February 2, 2011, NRC approved Improved Technical Specifications for Kewaunee Power Station. This License Amendment revised the TS definition of OPERABILITY consistent with NUREG 1431. The new (current) definition does not base operability on satisfying the LCO. Therefore, this system would now have been appropriately considered OPERABLE under the given conditions because it remained capable of fulfilling its specified safety function.

Event and Safety Consequence Analysis:

The TS 3.6.c ventilation systems support the containment system. Proper functioning of the Auxiliary Building Special Ventilation System is necessary to preclude possible unfiltered leakage through Shield Building penetrations that enter the Special Ventilation Zone (Zone SV). The system is designed to automatically start following a safety injection signal. Each of the two trains has 100% capacity. If one train is found to be inoperable, there is not an immediate threat to the containment system performance and reactor operation may continue while repairs are being made.

The charcoal adsorbers are installed to reduce the potential radioiodine release to the atmosphere. The laboratory carbon sample test results indicate a radioactive methyl iodine removal efficiency under test conditions which are more severe than accident conditions.

Accident analysis assumes a charcoal adsorber efficiency of 95%. To ensure the charcoal adsorbers maintain that efficiency throughout the operating cycle, a safety factor of 2 is used. Therefore, if accident analysis assumes a charcoal adsorber efficiency of 95%, this equates to a methyl iodide penetration of 5%.

If a safety factor of two is assumed, the methyl iodide penetration is reduced to 2.5%. Thus, the acceptance criteria of 97.5% efficient is used for the charcoal adsorbers.

The charcoal adsorber test results were at a 96.589% efficiency for Auxiliary Building Special Ventilation Train A. The Train A maintained its safety function since the measured value for efficiency was greater than the accident assumed value of 95.0%.

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

Cause:

The cause of this event was unplanned inoperability of the Auxiliary Building Ventilation Train A due to a decrease in efficiency of the charcoal adsorbers. The direct cause of the decrease in charcoal efficiency was charcoal filter end of life. This was as a result of the inability of trending to adequately identify charcoal filter banks that are degrading prior to failure. The filter testing program accounts for the inexactness in predicting end of life by using a safety factor of 2 (as previously discussed).

Corrective Actions:

The charcoal filter banks were replaced and in-place testing was completed for the Auxiliary Building Ventilation System Train A.

Activities are being created to periodically replace the Auxiliary Building Ventilation System charcoal filter banks and other ventilation systems that contain charcoal adsorber filters.

Similar Events:

A review of Licensee Event Reports covering the last three years identified no similar events.