05000416/LER-2010-002, For Grand Gulf, Control Room Air Conditioning Subsystem B Tripped on Low Oil Pressure While in the a Subsystem Was Inoperable for Maintenance Resulting in a Condition That Could Have Prevented the Fulfillment of the Mitigation

For Grand Gulf, Control Room Air Conditioning Subsystem B Tripped on Low Oil Pressure While in the a Subsystem Was Inoperable for Maintenance Resulting in a Condition That Could Have Prevented the Fulfillment of the Mitigation

ML103480006
Person / Time
Site:	Grand Gulf
Issue date:	12/13/2010
From:	Perino C Entergy Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
GNRO-2010/00077 LER 10-002-00
Download: ML103480006 (8)

LER-2010-002, For Grand Gulf, Control Room Air Conditioning Subsystem B Tripped on Low Oil Pressure While in the a Subsystem Was Inoperable for Maintenance Resulting in a Condition That Could Have Prevented the Fulfillment of the Mitigation

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(8) 10 CFR 50.73(a)(2)(viii)(8) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(8)
4162010002R00 - NRC Website

text

PO Port Gibson, Mississippi Entergy Christina Perino Licensing Manager GNRO-201 December 13,2010 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 LER 2010-002-00 Control Room Air Conditioning Inoperability -

of Both Trains Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 I£"C'",C'C No.

Dear Sir or Madam:

Attached is Licensee Event Report (LER) 2010-002-00 which is a final report. This report is submitted in accordance with 10 CFR 73(a)(2)(v)(D).

This letter does not contain any commitments. Should you have any questions regarding the attached report, please call Rita Jackson at 601-437-2149 or Christina L.

Perino at 601-437-6299.

Sincerely, CLP/RRJ

Attachment:

LER 2010-002-00 Cc:

(See Next Page)

cc:

NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150 U.S. Nuclear Regulatory Commission ATIN: Mr. Elmo Collins, Jr. (w/2)

Region Administrator, Region IV 612 East Lamar Blvd, Suite 400 Arlington, TX 76011-41 U.

Nuclear Regulatory Commission ATTN: Mr. Alan Wang, NRR/DORL (w/2)

Mail Stop OWFN/8 G14 Washington, DC 20555-0001

1 OF 6 EXPIRES: 10/31/2013

3. PAGE

2. DOCKET NUMBER 05000416 Unit 1 U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) reverse for number of each NRC FORM 366

1. FACILITY NAME Grand Gulf Nuclear

4. TITLE Control Room Air Conditioning ~UlJfSvstem '8' Tripped On Low Oil Pressure While the 'A' Subsystem was Inoperable for Maintenance Resulting in a Condition that Could Ha\\le Fulfillment of the Mitigation Function 05000 N/A 12

12. LICENSEE CONTACT FOR THIS LER 20.2201 (b) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 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)(8) 50.73(a)(2)(viii)(8) 20.2203(a)(2)(i) 50.36(c)(1 )(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(i\\l)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(\\I)(A)

D73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(\\I)(8)

D73.71(a)(5) 20.2203(a)(2)(\\I) 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)

OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(8) 50.73(a)(2)(\\I)(D) in Abstract below or

Based on 11 following the ""VI T

, *.* of the immediate corrective a~~~vl'<:> a recent 67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> of continuous run, the I

!IIClll of the six thermal t;lAtJCU I<:>IVII a maintenance retest run performed on October 30, 2010, and a 24-hour operability run with the Standby Fresh Air heaters performed October 31,2010 to November 1,2010, the CRAC B system was declared operable and returned to service.

D.

Cause of Occurrence The primary method used to determine the root cause for the equipment problems associated with this event was the Kepner-Tregoe (KT) Problem Analysis process. The KT Problem Analysis identified three.

• failure mechanisms based on the as-found condition of the equipment and the maintenance performed as follows:

1)

Intermittent failure of the low oil differential pressure switch which is in the trip circuitry of the compressor and trips the compressor on low differential pressure. The replacement differential pressure switch was a less robust design than the originally supplied switch.

The replacement differential switch that was installed on the CRAC B train did not provide consistent trip actuation compared to the installed gauges. This was demonstrated with two out of the three replacement switches used.

2)

Intermittent failure of one or more loading/unloading mechanisms due to inadequate work instructions of the compressor rebuild preventive maintenance tasks.

During the last compressor rebuild prior to the October 14, 2010 trip, the loaders/unloaders were not disassembled and inspected. The preventive maintenance (PM) task instructions did not specifically address an inspection of the loader/unloaders. After the number six cylinder loader/unloader was replaced, normal usable oil pressure was achieved. The number six cylinder was replaced because wear marks were found on one of the internal surfaces indicating that this cylinder may have experienced oil leakage.

3)

One or more of the temperature control valves were in an open condition or in a more than desired open condition. The established periodicity or method used to prevent or detect equipment degradation was not effective. The degree of superheat had not been routinely measured and recorded. Had this been done, a degrading trend may have been detected and corrected prior to a compressor trip.

The design purpose of the thermal expansion (temperature control) valve is to maintain a constant degree of superheat across the evaporator. It senses the exhaust temperature and adjust Freon flow by opening and closing an integrated control valve. If one or more of these valves was to fail in an open condition or more than desired open condition then more Freon would be allowed to flow through the evaporator coils, losing superheat and allowing very cold Freon to the compressor. The dissolved Freon in the oil boils out and carries the oil into the condenser.

A Contributing Cause of failure to exclude foreign material during maintenance activities on CRAC B was identified. Actions taken to preclude the entrance of any undesirable material were inadequate.

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2. DOCKET 05000416

6. LER NUMBER YEAR ISEQUENTIAL I NUMBER 2010 002 00 REV.

NO.

3. PAGE 40F6 A

root cause could not definitively be determined; however, GGNS made the decision to address all three of the possible root causes as well as the contributing cause.

E

Corrective Actions

Immediate Actions Immediate actions following this event were to recover CRAC A, place it in service and then disassemble CRAC B compressor, perform inspections, retrieve oil samples and perform maintenance.

Additionally, the CRAC B compressor was rebuilt, including replacing all six thermal expansion valves, the differential oil pressure switch, the filter dryer and the number six loader/unloader.

Short and Long Term Actions The corrective actions for the three probable root causes are listed below.

1)

Ensure that only original differential pressure switches (or a suitable equivalent) can be used and exclude the replacement switch model that was utilized to replace the original switch.

Update all applicable parts lists. This switch CAT 10 99193008 Model F0113ZUK is manufactured by Emerson/Alco.

2)

Revise compressor PM tasks for both A and B compressors to include lessons learned from Trane benchmarking. This will include detailed instructions for the loader/unloader disassembly, inspection and re-assembly. Revise tasks for compressor A and B rebuilds.

3)

Revise compressor PM tasks for both A and B compressors to record degree of superheat for each thermal expansion valve. Revise leak check PM tasks.

The corrective actions for the contributing cause are:

Provide additional gUidance in the compressor PM for both compressors.

Revise performance monitoring plan for CRAC system to ensure monitoring criteria are complete and robust.

Revise the control building operator rounds to provide tighter operating limits for CRAC compressor lube oil suction and discharge pressures differential pressure.

These corrective actions and others are being tracked in GGNS's Corrective Action Program under CR-GGN-2010-7315.

F.

Safety Assessment

According to the GGNS Technical Specification Bases, the design basis of the CRAC System is to maintain the control room temperature for a 30 day continuous occupancy and ensure the OPERABIL1TY of components in the control room. The ability of the CRAC System to maintain the control room temperature during Modes 1, 2, and 3 is implicitly assumed in the analyses of the design basis accidents (e.g., loss of coolant accident, main steam line break). The TS Bases also states that the Control Room AC System satisfies Criterion 3 of the NRC Policy Statement. This means that it is considered to be a part of the primary success path which functions to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

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Unit 1 05000416 2010 002 00 50F6 The GGNS UFSAR states that the control room HVAC ensures that the operability of the s8r8rv-r8118IF!O control and instrumentation will not be due to environmental conditions and will continue to function in a environment.

no sP<<~CI:BI environmental design requirements have been incorporated in the qualification of equipment located in the control room.

Since the Control Room was maintained within limits until a CRAC sU[)svstem was there was no impact to the equipment located in the control room with of the following two C::O\\/C::OTl::tln'lC::O Two Control Room alarms were received due to the elevated ternpE~ratures; A RCIS INOP alarm came in at 0937 and was reset several times, but would not stay reset. Control room temperature was elevated at approximately 87 F at the time. RCIS was reset successfully at 1202 hours0.0139 days <br />0.334 hours <br />0.00199 weeks <br />4.57361e-4 months <br />, after CRAC B was restored and Control Room temperature was lowered to 79 F. During the RC&IS INOP period the rod gang drive cabinet analyzer stopped, this does not compromise the safety function of the system. The rod positions are still available at the rod action control cabinets.

The Control Room alarm CCW DIV 1 MOVs TROUBLE (Component Cooling Water Division 1 Motor Operator Valve Trouble Alarm) was received at 0940 hours0.0109 days <br />0.261 hours <br />0.00155 weeks <br />3.5767e-4 months <br /> while the Control Room temperature was at approximately 87 degrees F. There was no other apparent cause for the alarm. The alarm cleared at 1233 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.691565e-4 months <br />, after CRAC B was restored and Control Room temperature was lowered to 76F (CR-GGN-2010-07299).

The Alarm Response Instruction (ARI) immediate actions were performed for this alarm. No failure status lights were illuminated. No CCW DIV 1 MOVs had power loss, no trip units were tripped or gross failed. The cause of the alarm could not be determined; it was most likely due to an intermittent annunciator circuit. No CCW components were affected.

The CRAC system also maintains control room habitability. This function was not affected by this event.

The control building is outside of the radiological controlled area therefore there were no radiological concerns for this event, nor were there any industrial safety concerns associated with the event.

G. Additionallnformation Previous Occurrences - There has not been any occurrence of an event or condition in the past five years at Grand Gulf Nuclear Station involving these same conditions.

The Root Cause Evaluation addressed the extent of condition as well as the extent of the cause of this event. There are two identical trains of CRAC, A and B. No other air conditioning systems in the plant use the CVI Inc.

model unit. CRAC A unit was reviewed for extent of condition relating to low usable oil pressure trips on the B unit. There is no immediate concern with CRAC A. All Corrective Actions for CRAC Bare being applied to CRAC A.

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An

'fJC1 CUIII~ EAfJCIICII\\.,c search was performed using multiple searches. No recordable differential pressure multiple failure OE cases with the original switch or replacement switch were noted and no Si~llm\\"dlll Operating EAtJCIICII\\.,C Report (SOER) I Industry Event Report (IER) cases were found Illal\\"II;II~ any of the identified root causes.

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