2CAN051405, LER 14-01-00 for Arkansas Nuclear One, Unit 2 Regarding Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications

LER 14-01-00 for Arkansas Nuclear One, Unit 2 Regarding Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications

ML14135A246
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/15/2014
From:	Jeremy G. Browning Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2CAN051405 LER 14-01-00
Download: ML14135A246 (7)

Text

Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Jeremy G. Browning Site Vice President Arkansas Nuclear One 2CAN051405 May 15, 2014 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Licensee Event Report 50-368/2014-01-00 Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6

Dear Sir or Madam:

Pursuant to the reporting requirements of 10 CFR 50.73, attached is the subject Licensee Event Report concerning Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications.

There are no new commitments contained in this submittal.

Should you have any questions concerning this issue, please contact Stephenie Pyle, Manager, Regulatory Assurance, at 479-858-4704.

Sincerely, Original signed by Jeremy G. Browning JGB/rwc

Attachment:

Licensee Event Report 50-368/2014-001-00

2CAN05140x Page 2 of 2 cc: Mr. Marc L. Dapas Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 LEREvents@inpo.org

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA/Privacy Section (T-5 F53), U.S. Nuclear Regulatory LICENSEE EVENT REPORT (LER) Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects.resource@nrc.gov, and to the Desk Officer, Office of Information (See reverse for required number of and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and digits/characters for each block) Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME 2. DOCKET NUMBER 3. PAGE Arkansas Nuclear One - Unit 2 05000368 1 OF 5

4. TITLE Operation of Switchgear Rooms Ventilation Prohibited by Technical Specifications

5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NO.

FACILITY NAME DOCKET NUMBER 3 31 2014 2014 - 001 - 00 05 15 2014

9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 1 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)

10. POWER LEVEL 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 100% 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D) Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)

Stephenie L. Pyle, Manager, Regulatory Assurance 479-858-4704

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT MANU- REPORTABLE MANU- REPORTABLE CAUSE SYSTEM COMPONENT CAUSE SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIX

14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR SUBMISSION YES (If yes, complete 15. EXPECTED SUBMISSION DATE) NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

While performing a post-assessment of a 10 CFR 50.59 evaluation performed in 2002 for a modification to the Arkansas Nuclear One (ANO) Unit 2 switchgear room exhaust fans, ANO identified that automatic action had been replaced with credit for manual operator action. During additional evaluations of this concern, it was identified that there was one occasion within the last three years in which the room coolers and exhaust fan configuration did not support the operability of the switchgear room without reliance on operator action, which was longer than the time allowed by Technical Specification.

The apparent cause of this condition is the inappropriate credit of operator action in place of an automatic action.

As a corrective action, caution cards were promptly placed on the Control Room hand switches and local breakers associated with the exhaust fans.

NRC FORM 366 (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV.

NUMBER NO.

Arkansas Nuclear One - Unit 2 05000368 2 OF 5 2014 -- 001 -- 00 NARRATIVE A. Plant Status At the time this condition was identified, Arkansas Nuclear One, Unit 2 (ANO-2) was operating at approximately 100% power. No structures, systems or components were out of service at the time of this event that contributed to this event.

B. Event Description This condition is associated with a 10 CFR 50.59 evaluation performed in 2002. While performing a post-assessment of that evaluation in response to a separate NRC Resident Inspector question, ANO identified a concern with the evaluation. The evaluation is associated with a modification which changed the operation of the ANO-2 switchgear room exhaust fans from automatic (start on high room temperature) to manual start. This modification was necessary to preclude the pressurization of an area which could affect the operability of the Control Room boundary post-accident.

It was determined that the electrical equipment in the switchgear rooms were operable if both service water supplied room coolers in each room were operable. The associated switchgear exhaust fans are not required for switchgear room operability as long as both room coolers in a room are operable.

If a room cooler is taken out of service for planned maintenance, the exhaust fan can be started before removing the cooler from service to maintain operability of the associated switchgear within the room without reliance on post-accident operator action, or the associated Technical Specifications (TSs) for the switchgear equipment can be entered.

The current procedure for removing a room cooler from service is to verify the exhaust fan is operable.

It does not require the exhaust fan to be placed in service. The aforementioned caution cards compensate for this condition until further analyses can be completed and procedures subsequently revised.

ANO-2 TS 3.8.2.1 requires a specific list of vital electrical busses to be operable. The ANO-2 switchgear rooms contain a portion of these busses. If less than the full list of busses are operable, the TS requires the inoperable bus(ses) to be returned to operable status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV.

NUMBER NO.

Arkansas Nuclear One - Unit 2 05000368 3 OF 5 2014 -- 001 -- 00 A subsequent evaluation determined that at 2300 on February 12, 2014, one of the room coolers was removed from service in accordance with procedures and the cooling requirements of the procedures were verified (exhaust fan verified operable, but not placed in service). This room cooler was restored to operation at 1530 on February 13, 2014. This time period exceeds the total of TS allowed outage time and action time of 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> to be in HOT STANDBY.

C. Background - System Design This condition impacts rooms 2100 and 2101, the Red and Green Train Vital 4160V Switchgear Rooms. Room 2100 contains 4160V bus [EB] 2A4 and 480V bus 2B6 [EB]. Room 2101 contains 4160V bus 2A3 and 480V bus 2B5, among other equipment.

Each room has two room coolers. These cooling units take air from the respective switchgear room and returns cooled air to the same area. One of the two cooling units in each switchgear room is normally in stand-by. These coolers are supplied with service water. The unit coolers are designed to maintain normal room temperature at 110 °F DB maximum with 85°F service water available.

The coolers are designed to be operated automatically during a design basis accident (DBA).

The room coolers are safety related and seismic category 1 components.

During normal operation the unit coolers can be started manually from the Control Room.

Each switchgear room is also equipped with an exhaust fan. In the original design, if the switchgear room temperature rises above 120 °F, the room thermostat [IM] starts the exhaust fan to remove the air from the switchgear room to the Controlled Access 2 (CA-2) area. This latter area borders the ANO-2 Control Room.

During normal operation the exhaust fans are off. The fans may be started manually from the Control Room as needed.

It was determined in 2002 during the original tracer gas testing of the Control Room that this configuration increases air in-leakage rates into the Control Room which negatively impacts Control Room dose values. To reduce air in-leakage, Operations opens a door at CA-2 prior to starting the switchgear exhaust fans, eliminating pressurization of CA-2. In order to maintain Control Room habitability during a DBA, the operation of the exhaust fans was changed from automatic control by thermostat (i.e. on at 120 °F) to manual control to permit Operations time to open the CA-2 door..

NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV.

NUMBER NO.

Arkansas Nuclear One Unit-2 05000368 4 OF 5 2014 -- 001 -- 00 D. Event Cause The apparent cause of this condition is the inappropriate crediting of operator action in place of an automatic action. See Information Notice 97-78, Crediting of Operator Actions in Place of Automatic Actions and Modifications of Operator Actions, Including Response Times.

E. Corrective Actions Operations promptly placed caution cards on the Control Room hand switches and local breakers associated with the exhaust fans.

Additional evaluations are being performed to determine if one room cooler is sufficient to maintain the room and equipment operable.

F. Safety Significance Evaluation The room coolers provide temperature control for the safety related 4160V bus 2A4 and 480V bus 2B6 room, and the 4160V bus 2A3 and 480V bus 2B5 room. The design of the coolers is to maintain the room temperature such that the electric busses remain operable post-accident. This ventilation system ensures that the ambient air temperature does not exceed the allowable temperature for the equipment. The rooms, busses and room coolers / exhaust fans are arranged in redundant safety related trains.

The exhaust fans originally received an automatic start signal on high room temperature (120 °F) in the event of an accident. This was replaced with manual actions.

Although there have been no events at ANO-2 that would have required long-term cooling using the exhaust fans, the fans could have been placed into service from the Control Room as needed to maintain the ambient air temperature in the room below the allowable temperature for the equipment.

G. Basis for Reportability This event is reported pursuant to the following criteria:

10 CFR 50.73(a)(2)(i)(B) - Any operation or condition which was prohibited by the plants Technical Specifications.

NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV.

NUMBER NO.

Arkansas Nuclear One Unit-2 05000368 5 OF 5 2014 -- 001 -- 00 With the requirement of having the exhaust fan operating or entering the TS when one or more room coolers are removed from service, a review of the past three years identified a time in which a room cooler was out of service without the exhaust fan operating for greater than the 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> allowed by TS 3.8.2.1 to be in HOT STANDBY.

H. Additional Information 10 CFR 50.73(b)(5) states that this report shall contain reference to any previous similar events at the same plant that are known to the licensee. NUREG-1022, Revision 3 reporting guidance states that term previous occurrences should include previous events or conditions that involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.

A review of the ANO corrective action program and Licensee Event Reports for the previous three years was performed. While several instances of issues associated with room coolers at ANO, no relevant similar events were identified.

Energy Industry Identification System (EIIS) codes and component codes are identified in the text of this report as [XX].

NRC FORM 366A (02-2014)