ML17191A787

Regulatory Conference Presentation 07-13-17

ML17191A787
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Site:	Pilgrim
Issue date:	07/13/2017
From:	Entergy Corp
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Download: ML17191A787 (39)

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1 PILGRIM NUCLEAR POWER STATION REGULATORY CONFERENCE EDG A Cooling Fan Right Angle Drive Gearbox July 13, 2017

2 Entergy Representatives Brian Sullivan Site VP Jack Davis VP, Regulatory Assurance (Fleet)

David Noyes Director, Recovery Thomas White Manager, Design and Programs Engineering Grant Flynn Senior Manager, Operations Ronald Gaston Director, Regulatory Compliance (Fleet)

Everett Perkins Manager, Regulatory Assurance

3 OPENING REMARKS Brian Sullivan Site Vice President Pilgrim Nuclear Power Station

4 Agenda Opening Remarks Brian Sullivan Overview Dave Noyes Endurance Test and Vibration Analysis Tom White Root Cause Evaluation Dave Noyes Corrective Actions Grant Flynn Risk Significance Tom White Closing Remarks Brian Sullivan

5 OVERVIEW Dave Noyes Director, Recovery Pilgrim Nuclear Power Station

Introduction

• PNPS agrees with the Design Control Violation

• The deficient performance was in 2000 and current design process would have driven a complete review.

• Recently Endurance Test and Engineering Analysis demonstrate that EDG A was functional at any time prior to September 2016.

• Familiarization with Cooling Fan and Gearbox design.

6

Introduction

• As-found Condition

• Actual picture of EDG-A cooling fan gear box room 7

EDG A Cooling Fan Gearbox 9

Gearbox Internals Robust design with machined gears

10 Gearbox Oil Level - Post-Endurance Test Gear on horizontal shaft always in contact with oil

Relief Valve Vibration incapable of loosening a properly set RV

As-Found Condition of Relief Valve Oil lost only during gear pump operation

13 ENDURANCE TEST DESIGN AND RESULTS Thomas White Manager, Design and Programs Engineering

14 Test setup well represented Test Setup actual installation

• Equipment Representative of Air Side EDG-A Radiator System Identical Fan Equipment Actual gearbox that was found with low oil.

15 Test Conditions well represented Test Conditions actual installation

• System produces conservative air flow conditions:

o Similar gearbox loading; and o Lower convective cooling of the gearbox.

• Gearbox was instrumented to monitor potential signs of degradation:

o Vibration; and o Temperatures near bearings.

• Baseline runs showed similar vibration levels to those measured in the plant.

16 Endurance Test Conditions

• Air temperature bounded possible plant conditions. The temperature was determined for:

o Highest ambient temperatures recorded on site between August 31 to September 28, 2016 o Highest accident scenario (LOCA) engine loading

• Relief valve was offset in the as-reported as-found condition, and restrained to bound any condition that could occur.

17 Endurance Test Conditions

• The initial oil level was at the as-found level observed by the maintenance technicians.

o Allowed the oil to drain undisturbed for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to testing.

o Level was well below input shaft bearings.

18 Endurance Test Temperature Results Temperatures remained well below the 300 F limit

• The gearbox successfully performed its function of transmitting power to the fan for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with low oil.

• Gearbox temperatures reached steady-state values well below manufacturers damage threshold limits.

19 Endurance Test Vibration Results

• The gearbox vendor stated that no increase in vibration indicates no equipment degradation

• Gearbox vibrations reached steady state values during testing in acceptable range

20 Endurance Test Results

• Demonstrated sustainable operation

• Post-test internal inspections showed no visible damage to gear teeth or the roller bearings.

• Gearbox backlash measurements essentially the same before and after testing

• Oil analysis found indicators of small wear particles o Less than 5 mils o Symptomatic of misalignment o The observed wear would not have impacted long term operation.

21 Endurance Test Conclusions

• Test demonstrates gearbox would have fulfilled its safety function for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> starting at as-found oil level.

• It is concluded that gearbox would have continued to operate with low oil for an extended period of time well beyond 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> based on:

o Stable Test Parameters: Temperatures and vibrations reached steady state values within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Temperatures are within manufacturers design limits. No signs of gearbox degradation could be identified from monitored parameters.

o Stable Oil Level: Oil leaked from relief valve during first 20 minutes, but no leakage occurred thereafter. All measured temperatures were well below the oil vaporization temperature, and therefore level would not be further reduced by vaporization.

22 Endurance Test Conclusions (contd) o Post-Test Gearbox Condition: Post-test inspection found no visible damage, and gearbox backlash was not degraded. Analysis of oil after testing found very small (< 5 mils) metallic wear particles.

Wear particles identified would not have any detrimental effects on near-term continuous operation.

o Margin in Gearbox Design - Gearbox is designed to transmit ~3x more power than required to drive radiator fan at design conditions.

o Cooling Capacity - High air flow near gearbox results in significant convective cooling which can remove additional heat generated due to low oil operation without significant increase in temperature.

o Oil Chemistry - Lubrication oil used has extra pressure (E.P.)

additives that create a permanent oil film on component surfaces, and temperatures did not exceed manufacturers limit where additives start to break down.

23 Endurance Test Conclusions (contd)

The test demonstrated long-term sustainable performance as evidenced by:

• Stable component temperatures

• Stable oil level

• Consistent low vibration

• Lack of post-test equipment degradation

• Its the opinion of our industry experts who ran the test, based on sound engineering principles and judgement, the gear box could have functioned for much longer than the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test - 30 days.

24 ROOT CAUSE EVALUATIONS Dave Noyes Director, Recovery Pilgrim Nuclear Power Station

25 RCEs 2016-07443 and 2016-09706

• RCE 2016-07443, Rev 1 - Low Gearbox Oil Condition o Assess the EDG ventilation gearbox relief valve disassembly and the impact on EDG A functionality/operability

• RCE 2016-09706 , Rev 0 - Programmatic Deficiencies o Failure to effectively monitor the gearbox oil level based on a consideration of loss of inventory during testing o Introduction of the new failure mode (external relief valve) without appropriate design control considerations o Failure to identify, evaluate, and report the presumed loss of safety function associated with the equipment failure analysis

26 RCE 2016-07443 Root Cause: (Most Probable) An inadequate procedure for directing the gearbox oil pre-start check was the Root Cause.

Contributing Causes:

• Less than adequate training for non-licensed operators on method of verification (manual action) of the oil level in the fan gearbox.

• Inadequate program design of surveillance test for post-cool down inspection of EDG radiator fan room.

27 RCE 2016-07443 -

Extent of Cause/Condition

• The Condition was extended to other safety related equipment with gear boxes with oil levels which could be subject to a low or no oil condition included:

o High Pressure Coolant Injection (HPCI) Turbine o Standby Liquid Controls (SLC) Pumps o Control Rod Drive (CRD) Pumps o Reactor Core Isolation Cooling (RCIC) Turbine o Recirculation Motor Generator Set Fluid Drive Pumps

• The Cause was extended to procedures that provide instructions for fluid verification of safety related mechanical equipment.

• No Similar Issue Identified.

28 Relief Valve Vibration Analysis

• Analytic Approach o A calculation evaluated conservative vibration loading to thread pre-load.

o Determined with the relief valve at normal set pressure, the insert will not back out due to in-plant vibrations.

• Testing Approach o A test monitored the movement of the valve insert and cap under vibrations.

o Determined with the relief valve at normal set pressure, the insert will not back out due to in-plant vibrations.

o Determined that the as-found relief valve insert and cap position did not result from in-plant vibrations.

29 RCE 2016-9706 Root Cause: Effective monitoring of equipment inside the EDG radiator fan room to ensure operability of the EDG was not established due to restricted access to the room for personnel safety concerns with EDG in emergency standby. This caused the condition by preventing identification of the loss of oil from the EDG radiator fan gearbox prior to performing the surveillance test for EDG B, resulting in a loss of safety function for onsite emergency AC power.

Contributing Causes:

• Inadequate work practices during implementation of the design change process in 2002.

• Inadequate implementation of the corrective action program in the proper classification and prioritization of the condition report.

30 RCE 2016-9706 Extent of Cause/Condition

• The Condition was extended to other Tech Spec auxiliary electrical equipment that may be inoperable for reasons other than low oil level.

• The Cause was extended to effective monitoring of other safety-related systems whose failure could result in the loss of a safety function.

31 CORRECTIVE ACTIONS Grant Flynn Senior Manager, Operations

32 RCE 2016-07443 - Corrective Actions

• On September 28, 2016, after identifying the low oil condition:

o Drained oil and internally inspected gearbox visually; with no damage identified.

o Reassembled, bench tested and set the relief valve at 15 psig and refilled the gearbox with new oil. The monthly Surveillance Test was then successfully completed.

• Pre-start check procedure changed to provide additional guidance on how to validate the gearbox oil level.

• Non-licensed operator trained on gearbox oil level validation method.

33 RCE 2016-9706, Corrective Actions

• Establish an effective method to monitor equipment inside the EDG radiator fan rooms to ensure reasonable assurance of equipment operability when the EDGs are in emergency standby or in operation. Revise procedures to incorporate the established method to monitor equipment inside the EDG radiator fan rooms

• Perform an 50.59 Process Applicability Determination for the addition of the EDG fan gearbox relief valve to determine whether a full 50.59 evaluation is needed.

• Perform an assessment of completed minor modifications intended to accommodate component replacement with an engineering evaluated equivalent component to determine if any new failure mode was introduced but not properly recognized or evaluated.

34 RISK SIGNIFICANCE Thomas White Manager, Design and Programs Engineering

35 Key Risk Assessment Differences Preliminary Current o In the as-found condition the EDG o The Endurance Test provided was not functional and would have compelling evidence that the EDG A failed to run for its 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> PRA would have operated for at least the mission time. 24 Hour mission time prior to o The disassembly of the relief valve September 28, 2016.

was due to normal engine o Engineering Vibration evaluation vibrations, and as such the exposure period extended to March showed that if the relief valve was at 2016. its setpoint with the cap installed o Risk Significance dominated by vibration could not cause the Lower Switchgear Room fires which disassembly.

were assumed to cause a non- o Best Estimate is that this condition recoverable LOOP with reliance on is of very low safety significance, the A5 bus, which would lead to with the only increase in CDF being core damage if the EDG A failed. due to the time EDG A was out-of-o Did not credit FLEX Action to service to evaluate and correct the Charge Batteries following an ELAP low oil level.

36 SAFETY SIGNIFICANCE

SUMMARY

• Best estimate result is very low safety significance, limited to the increase associated with EDG A unavailability for evaluating and correcting the low oil level condition

• Sensitivity analysis using PNPS PRA model determined very low safety significance, using an EDG A failure rate 10 times normal and a one month exposure period.

37 CLOSING COMMENTS Brian Sullivan Site Vice President Pilgrim Nuclear Power Station

38 Summary

• We agree with the violation.

• EDG A was always functional (24-hour PRA mission and likely full 30-day mission time)

• This condition is of very low safety significance, with the only increase in CDF being due to the time EDG A was out-of-service to evaluate and correct the low oil level