ML20248J019

Safety Evaluation Accepting Licensee Inservice Testing Program Interim Pump Relief Request Per 10CFR50.55a(a)(3) (II)

ML20248J019
Person / Time
Site:	Summer
Issue date:	06/04/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20248J010	List: ML20248J008 ML20248J019
References
NUDOCS 9806080350
Download: ML20248J019 (6)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM INTERIM PUMP REllEF REQUEST SOUTH CAROLINA ELECTRIC AND GAS COMPANY VIRGIL C. SUMMER NUCI EAR STATION DOCKET NUMBER 50-395

1.0 INTRODUCTION

The Code of Federal Regulations,10 CFR 50.55a, requires that inservice testing (IST) of certain ASME Code Class 1,2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda, except where relief has been requested and granted or proposed attematives have bee authorized by the Commission pursuant to 10 CFR 50.55a (f)(6)(i), (a)(3)(i), or (a)(3)(ii). In order to obtain authorization or relief, the licensee must demonstrate that: (1) conformance is impractical for its facility; (2) the proposed attemative provides an acceptable level of quality and safety; or (3) compliance would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety. Section 50.55a (f)(4)(iv) provides that inservice tests of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to the limitations and modifications listed, and subject to Commission approval. NRC guidance contained in Generic Letter (GL) 89-04," Guidance on Deve!oping Acceptable Inservice Testing Programe," provided attematives to the Code requirements determined to be acceptable to the staff. The GL guidance also authorized the use of the attematives in Positions 1,2,6,7,9, and 10, provided the licensee follows the guidance delineated in the applicable position. When an attemative is proposed which is in accordance with GL 89-04 guidanca and is documented in the IST program, no further evaluation is required; however, implementation of the altemative is subject to NRC inspection.

Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staff's findings with respect to granting or not granting the relief requested, or authorizing the proposed

, attemative as part of the licensee's IST program, are contained in this Safety Evaluation (SE).

The second 10-year interval for the V. C. Summer Nuclear Station (VCSNS) began on January 1,1994, and ends on December 31,2003. The licensee's IST program is based on the 1989 edition of ASME Section XI, which references Operations and Maintenance (OM)

Standard, Part 6, for pumps (OM-6) and Part 10 for valves (OM-10). The licensee's February 11,1998, letter transmitted their interim relief request to the staff.

9906090350 980604 PDR ADOCK 05000395 P PDR Enclosure

2.0 DISCUSSION l

l Intenm Relief Request

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The licensee has requested relief from the OM-6 acceptance criteria requirements of Paragraph 1-6.1 for charging / safety injection pump *C." The pump is currently tested at full-flow conditions during refueling outages, and at minimum-flow conditions quarterly in accordance with GL 89-04, Position 9 guidance. Because of bearing vibration values in the alert range during refueling outage testing, the licensee has prop 7 sed to test the "C" pump every 6 weeks.

Bearing vibration will be monitored using spectral analysis until refueling outage (RF) 11, when the pump rotating element will be replaced. At the conclusion of RF-11, the licensee will revert back to the original testing schedule.

Licensee's Basis for Reauestina Relief The licensee states:

The Charging /SI Pumps are tested in accordance with NRC Generic Letter 89-04, Position 9. This position allows the use of a non-instrumented minimum flow path for quarterly testing with a test performed at substantial flow conditions during cold shutdowns or refueling outages. As the C Charging /SI Pump had also exceeded the code allowable for the alert range during minimum flow testing after the maintenance activity discussed below, the required quarterly frequency has been doubled resulting in a required test every six weeks. Periodic testing on minimum flow in conjunction with testing at substantial flow conditions during refueling outages provides adequate assurance that these pumps are capable of performing their design safety function upon demand.

This position is incorporated into the VCSNS Inservice Testing (IST) Program.

Through the IST Program, the acceptance criteria applied to pump performance parameters [are) established through ASME/ ANSI Oma-1988, Part 6. Part 6 is structured to address actions to be taken when performing quarterly tests for components within systems capable of demonstrating their design function performance during power operation.

The actioris prescribed for components with parameters in the Alert range do not accommodate components that require testing during cold shutdown plant mode to demonstrate design performance parameters. During the Fall 1997 refueling outage, Charging Pump C indicated one vibration point out of 5 (pump horizontal, outboard) to be in the Alert range for both full flow and minimum flow conditions, it was noted that the test frequency was impacted but that the pump was still recognized as opueble to the Code acceptance criteria. VCSNS initiated an evaluation ts determine the cause of the deviation and establish corrective actions, i

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The evaluation included a review of Charging Pump C data collected to determine a viable cause and established corrective actions that could be pursued to improve the vibration condition.

Efforts to determine the cause included-

• Analysis of the vibration data spectrum I

• Review of past maintenance history 1

• Review of trend data (in particular, vibration)

Corrective actions performed to alleviate vibration and confirm cause included-(this includes' activities prior to the start of the outage through the completion of the testing performed after all maintenance conducted during the outage)

• Performed alignment check; discovered that there was no apparent alignment problem, additionally, checks for a ' soft foot' condition were performed on the gearbox and pump casing hold down bolts. ' Soft foot' corrections were made on the gearbox.

• Inspected barrel key block, determined that the key was contacting but was not binding. No corrections were performed for this condition.

• Verified that all the bolts in the outboard bearing area were torqued as required.

• Disassembled pump coupling to insure correct assembly and presence of correct amount of grease.

• The pump outboard bearing housing was tom down, the radial bearing fits were checked. The bearing to housing fit was found to be out of tolerance, this was corrected by installing a gasket with the correct tolerances. The allowed axial float of the shaft was also out of tolerance, this condition was corrected by machining the end cover to correct the outboard thrust shoe position.

Full flow (substantial flow) testing was performed after [the conclusion of] each

' phase of major maintenance on the charging pump when the appropriate test conditions existed (e.g. refill or draindown of the reactor vessel). This test was performed a total of three times during RF-10 while attempting to find and correct the cause of the alert range vibration. The final test results indicate the outboard bearing horizontal vibration amplitude is 0.43 inches per second (ips). This value is above the Oma-6 limit for alert *ange (0.325 ips) but is still below the action range. The pump manufacturer, ingersoll Dresser Pump has provided a letter to

. SCE&G stating that the current levels of pump vibration are acceptable for continued operation and that for this pump,0.54 ips shoula be the alarm limit.

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Minimum flow testing was performed on this pump after all maintenance had been completed and the full flow test results were analyzed. The final results for

. this test were 0.38 ips at the same test point, with all other parameters satisfactory.

The increased frequency testing of every six weeks will provide periodic reinforcement that there is not a continuous degradation mechanism involved with this pump. Quarterly vibration measurements for this pump at this test point have shown a consistently high (but below alert) vibration level. These t measurements are recorded back through 1994 and range from 0.187 to greater than 0.305 ips. No additional significant degradation is expected to develop for this pump based on this history. Additionally, the full-flow vibration measurement for this point has been consistently close to the alert limit of 0.325 ips.

During maintenance on the pump, the vendor was onsite to provide additional guidance. EPRI was also consulted for possible additional actions after final testing was completed. SCE&G has determined, based on evaluation of the data and all available inputs, that the appropriate corrective action is to replace the rotating assembly. Other utilities were contacted to attempt to obtain a spare rotating assembly but none were available. VCSNS has one spare rotating

- assembly, however this assembly must be rebuilttalanced by the manufacturer (currently in progress) and this could not be completed prior to restart from the Fall 1997 outage.

A planned shutdown to Mode 6 in order to test this pump to comply with the increased frequency testing requirement will create unnecessary challenges to the plant and operating personnel without a corresponding increase in safety.

The C Charging /SI pump is the installed spare and is usually aligned to the operating pump but electrically racked out during all modes of operation.

Full flow (substantial flow) testing of 'ne charging pump would only be feasible during an extended planned shutdoun with the Reactor Vessel head removed.

VCSNS will conduct this testing pr'or to the 1999 Refueling outage if system alignment and reactor vessel cc.-ditions will support performance of the test.

However, should this condition not be corrected prior to the increased test frequency due date, the pump will be declared inoperable and removed from service if relief from increased frequency testing is not received from the NRC (requested by June 18,1998).

Altemative Testing The licensee proposes to: .

Perform on-line vibration monitoring and analysis at minimum flow conditions at a frequency of every six weeks to verify pump pe.1ormance and identify any pump degradation. The attemate test flow is the minimum charging pump flow of i approximately 60 gallons per minute (gpm). This relief is requested until i

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completion of the 11th Refueling Outage (scheduled for Spring,1999) when additional pump' repairs and full flow testing can be performed. Full flow testing during the next refueling outage will confirm acceptable operation after maintenance or will identify that further action is necessary. The test interval established by Generic Letter 89-04, Position 9 will be resumed when the cause is corrected.

3.0 EVALUATION There are three single speed, horizontal, centrifugal, charging pumps manufactured by Pacific Pumps (now ingersoll-Dresser Pumps) in the VCSNS chemical volume and control system.

The charging pumps are also the high-head safety injection pumps in the emergency coia cooling system (ECCS). Two pumps are required to fulfill their safety function. During plant operation, one pump is normally running, one pump is a non-running pump, and the third is a spare with its associated breakers normally racked out.

Each charging pump at VCSNS is being tested in accordance with the guidance provided in GL 89-04. Position 9 of GL 89-04 states that the increased interval is an acceptable attemative to the Code requirements provided that pump differential pressure, flow rate, and bearing vibration measurements are taken during this testing, and:

• flow can only be established through a non-instrumented minimum-flow path during quarterly pump testing, and a path exists at cold shutdowns or refueling outages to perform a test of the pump under full or substantial flow conditions.

Position 9 further specifies that quarterly testing also measuring at least pump differenti91 pressure and vibration is to be continued. Current considerations for Position 9, which are included in NUREG-1482, state that if a pump parameter is measured in the alert range during refueling outage testing, it is recommended that efforts be made to take corrective actions during the o'utage and perform testing after the maintenance is complete.

l l . During RF-10, the charging pump "C" outboard bearing, horizontal direction, was measured to l ,have overall vibration values during full- and minimum-flow testing above the alert range of l- 0.325 ips; The licensee stated in their basis for requesting relief that numerous maintenance activities have been performed on the pumps to reduce the vibration. After all maintenance

- was completed, the vibration values for the outboard bearing, horizontal direction, were L 0.43 ips and 0.38 ips for full flow and minimum flow respectwely. The pump manufacturer has stated that the current vibration levels are acceptable for operation.

The licensee concluded that the appropriate action was to replace the rotating assembly. An assembly was available onsite but could not be refurbished before the end of RF-10. The licensee plans to replace the rotating assembly on charging pump "C" during RF-11, scheduled to begin in the spring of 1999.

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{ The Code requires that, if a measured pump test parameter falls within the alert range, the testing frequency shall be doubled until the cause of the deviation is determined and the condition corr 6cted. Since the "C" charging pump was in the alert rcnge during RF-10, it would be required to be tested again during the middle of the cycle.' Because the "C" charging pump cannot be tested at full flow while the plant is at power, the licensee is requesting relief for an interim period from June 18,1998, until completion of RF-11. In the interim period, the licensee has proposed to test the pump every 6 weeks. This is the same interval as currently required by the Code because the pump is in the alert Iange on minimum flow. In addition to the Code overall vibration values, spectral data of the pump will be taken during each 6-week test.

It would be a burden on the licensee to shut the plant down to perform the Code-required testing if there were other means to monitor the pump for degradation during the interim period.

The proposed testing provides a reasonable assurance of oprational readiness because the pump will be monitored every 6 weeks, and spectral vibration data will be collected to assess whether the pump has experienced further degradation. In addition, during the next refueling outage, the relating assembly will be replaced.

4.0 CONCLUSION

On the basis of the above evaluation, the staff concludes that the proposed attemative to the Code acceptance criteria requirements of OMa-1988, Part 6, Section 6.1, for the "C" charging pump may be authorized pursuant to 10 CFR 50.55a(a)(3)(ii) based on the determination that compliance with the specified requirements results in a hardship without a compensating increase in the level of quality and safety. The attemative is authorized for an interim period from the date of this SE until completion cf the 11th refueling outage.

Principal Contributor: J. Colaccino Date: June 4, 1998