ML20206A211

Safety Evaluation Authorizing Pump Relief Request PRR-001 & Valve Relief Request VRR-001 & Denying Valve Relief Request VRR-002

ML20206A211
Person / Time
Site:	River Bend
Issue date:	04/21/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20206A206	List: ML20206A203 ML20206A211
References
NUDOCS 9904280101
Download: ML20206A211 (6)

Text

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g NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30006 0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR.BEOULATION RELATED TO INSERVICE TESTING PROGRAM RELIEF REQUEST FOR ENTERGY OPERATIONS. INC.

RIVER BEND STATION DOCKET NO. 50-458

1.0 INTRODUCTION

Title 10 of the Code of Federal Reaulations (10 CFR) Section 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 pumps and valves are performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (ASME Code) and applicable addenda, except where altematives have been authorized or relief has been requested by the licensee and granted by the Commission pursuant to Sections (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a. In proposing attematives or requesting relief, the licensee must demonstrate that: (1) the proposed attematives provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance is impractical for its facility. Section 50.55a authorizes the Commission to approve attematives and to grant relief from ASME Code requirements upon making the necessary findings.

Guidance related to the development and implementation of IST programs is given in Generic Letter (GL) 89-04, " Guidance on Developing Acceptable Inservice Testing Programs," issued l April 3,1989, and its Supplement 1 issued April 4,1995. Also see NUREG-1482, " Guidelines for Inservice Testing at Nuclear Power Plants," and NUREG/CR-6396, " Examples, Clarifications, and Guidance on Preparing Requests for Relief from Pump and Valve Inservice Testing Requirements."

. The 1989 Edition of the ASME Code is the latest edition incorporated by reference in Section 50.55a(b). Subsection IWV of the 1989 Edition, which gives the requirements for IST of valves, references Part 10 of the American National Standards Institute /ASME Operations l and Maintenance Standards (OM-10) as the rules for IST of valves. OM-10 replaces specific i requirements in previous editions of Section XI, Subsection IWV, of the ASME Code.

Subsection IWP of the 1989 Edition, which gives the requirements for IST of pumps, references Part 6 of the American National Standards Institute /ASME OM-6 as the rules for IST of pumps. ,

OM-6 replaces specific requirements in previous editions of Section XI, Subsection IWP, of the i ASME Ccde.

Entergy Operations, Inc.'s (EOl's, the licensee's), IST program submitted in a letter dated I December 2,1997, covers the second 10-year IST interval for the River Bend Station (RBS),

which began on December 1,1997. In a separate letter dated January 6,1998, and i supplemented September 10,1998, EOl submitted one pump relief request and two valve relief requests for its second 10-year IST program. The staff's evaluation of these relief requests are provided herein.

Enclosure '

9904290101 990421

• PDR ADOCK 05000458 .

P PDR E

2.0 PUMP RELIEF REQUEST 2.1 Relief Reauest PRR-001 1 The licensee has requested relief from the vibration measurement requirements of OMa-1988,

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Part 6 (OM-6), Paragraph 4.6.4(b), for the standby service water pumps and the diesel fuel oil i transfer pumps listed below. Paragraph 4.6.4 requires that vertical line shaft pump measurements shall be taken on the upper motor bearing housing in three orthogonal directions, one of which is the axial direction. The licensee has proposed to take vibration measurements in three orthogonal directions in a location that provides valid indication of motor vibratory motion in close proximity to the upper motor bearing housing.

SWP-P2A EGF-P1A SWP-P2B EGF-P1B l

. SWP-P2C EGF PIC I SWP-P2D 2.1.1 Licensee's Basis for Reauestina Relief The licensee states:

The standby service water pump motors are totally enclosed, weather proof induction motors that are equipped with housing covers which completely ens.aroud the upper motor bearing housing. The housing cover precludes vibration measurements from being taken directly on the upper bearing housing.

The diesel fuel oil transfer pumps are also equipped with housing covers that preclude vibration measurements from being taken directly on the upper motor bearing housing.

Removing the upper motor bearing housing covers for routine vibration readings, would compromise the design configuration and the operation of the pump motors. Cooling, thermocouples and other motor sensors would be disabled.

Also, the test configuration would differ greatly from normal configuration which would invalidate the test data obtained to prove operational readiness of the pump. This option is not practical.

Modifying the upper bearing housing cover to include an access port or installing vibration sensors is not preferred since these methods would change component configuration without a compensating inc. ease in safety. The transmission path for the attemate vibration points will not attenuate the vibration response or amplitude, therefore providing equivalent dLta without disturbing the equipment operation or design.

Therefore, the alternative testing proposed would provide adequate indication of component condition to verify operational readiness.

n9 2.1.2 Alternative Testing The licensee proposes:

Vibration measurements will be taken in three orthogonal directions in a location that provides valid indication of motor vibratory motion in close proximity to the upper motor bearing housing.

On the standby service water pumps the upper measurements will be taken on a lifting lug that is integral to the motor stator housing. The lifting lug is structurally rigid and provides transmissibility of the motor vibratory motion. The vibration j measurements will be taken in three orthogonal directions on the lifting lug. l On the diesel fuel oil transfer pumps the upper measurements will be taken on the motor stator housing which is rigidly connected to the motor bearing housing. 4 The vibration measurements will be taken in three directions on the motor stator I in close proximity to the motor bearing housing.

2.1.3 Evaluation The Code requires that quarterly vibration measurements be taken on vertical line shaft pumps during their regular inservice test. Since the actual pumps are submerged in water or oil, the Code requires that vibration measurements be taken on the upper motor bearing housing in three orthogonal directions, one of which is the axial direction. The licensee states that accat .

to the upper motor bearing housing for both the standby service water and diesel fue,I oil j transfer pumps is impeded by housing covers on all seven pumps. It would be a hardship without a compensating increase in safety for the licensee to modify the pump to perform the vibratic,n measurements if there were comparable locations on the pumps to collect vibration data.

The licensee has proposed to take vibration measurements from attemative locations that would provide vibration data, which was not attenuated from the upper motor bearing housing.

For the standby service water pumps, the licensee will take vibration measurements from a lifting lug that is integral to the motor stator housing. The vibration measurements for the diesel fuel oil transfer pumps would be taken from the motor stator housing, which is rigidly connected to the motor bearing housing. The licensee states that measurements will be taken in three orthogonal directions on all pumps as required by the Code.

The licensee's alternative locations for taking vibration measurements provide rigid structural contact to the motor bearing housing. The locations should not be subject to dampening effects that could mask potential degradation. Therefore, the licensee's proposed attemative testing will provide assurance of pump operability. In addition, the licensee should ensure that the new test locations are properly marked in accordance with OM-6, Paragraph 4.6.4(d), to ensure the validity of the vibration measurements upon implementation of the attemative testing.

F-2.1.4 Conclusion The proposed alternative to the vibration measurement requirements of OM-6, Paragraph 4.6.4(b), for the standby service water pumps and the diesel fuel oil transfer pumps ,

is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) based on the determination that compliance j with the specified requirements results in a hardship without a compensating intcrease in the level of quality and safety. A similar alternative was authorized for RBS in an NRC safety evaluation dated April 28,1997.

3.0 VALVE RELIEF REQUEST 3.1 Relief Reauest VRR-001 VRR-001 requests relief from the stroke time measurement requirements of ASME Code.

OM-10, Paragraph 4.2.1.4, for the affected main steam line safety / relief valves (SRVs) and automatic depressurization system (ADS) relief valves. These valves are located on the main steam lines between the reactor vessel and the first isolation valve inside the drywell.

3.1.1 Licensee's Basis for Heauestino Relief The licensee states: 1 The Safety Relief Valves are not equipped with direct position indicating devices.

Additionally, the actual valve stroke times are on the order of 100 mS. Use of other -

indicators of valve position (i.e. acoustic monitors, tailpipe temperature, vessel pressure) da not provide the accuracy required to use the stroke times, which would be obtained, for any meaningful use (i.e., degradation trending). The proper valve stem movement during actuation is verified during periodic shop testing.

Modification of the valves to provide direct position indication would be costly and would not provide a compensating increase in the level of safety gained by the availability of stroke time measurements.

3.1.2 Alternative Testina The licensee proposes:

No stroke time measurements will be performed. The valves will be full stroke exercise tested in accordance with ASME/ ANSI OMa-1988, Part 10. SRV tailpipe staam flow, reactor vessel pressure drop, or indication on the SRV tailpipe acoustic monitor will be used to provide positive indication of valve stroke.

3.1.3 Evaluation and Conclusion The Code requires that power-operated valves be stroked-timed in order to determine the I extent of any valve degradation. However, the affected SRVs and ADS valves are not equipped with direct position indicating devices, and additionally, the actual valve stroke times are on the order of 100 ms. Although the installation of direct positioning indicators may be physically possible, there are no feasible means to accurately measure the stroke time. To I

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O 5-require the installation of a device to directly measure stroke time would constitute z. hardship without a compensating increase in the level of quality and safety. The proposed means of using acoustic monitors, tailpipe temperature, and vessel pressure drop do not provide the accuracy for the required stroke time, but it would provide reasonable assurance of valve stroking and operational readiness of the affected valves.

The staff concludes that relief from the stroke time measurement requirements of OM-10, Paragraph 4.2.1.4, for the main steam SRVs and ADS valves is granted pursuant to 10 CFR 50.55a(a)(3)(ii) based on the determination thct compliance with the Code requirements results in a hardship without a compensating increase in the level of quality and safety and that the proposed attemative provides reasonable assurance of valve operability.

A similar alternative for the same valves was authorized for River Bend in an NRC safety evaluation dated November 24,1997.

3.2 Relief Reauest VRR-002 VRR-002 requests relief from the requirements of valve obturator movement of Paragraph 4.3.2.4(b) of OM-10 when a mechanical exerciser is used for the following check valves:

E22-AOVF005; E12-AOVF041 A; E12-AOVF041B; E12-AOVF041C; E21-AOVF006; E51-AOVF065; E51 AOVF066 3.2.1 Licensee's Basis for Reauestina Relief The licensee states:

Demonstration of valve obturator movement in accordance with Part 10, Paragraph 4.3.2.4(b) may not provide adequate assurance of valve operational readiness for check valves other than vacuum breakers. Measurement of the force or torque required to initiate movement (breakaway) may not be sufficient to verify that the listed valves are capable of stroking to their open safety position. Valve binding in excess of acceptable limits may occur at the obturator positions beyond the point of initial movement. This mode of valve degradation would not be identified by the procedure specified in Part 10, Paragraph 4.3.2.4(b).

The listed valves no longer have air actuators connected to the valves. Therefore, the valve actuators cannot be used to perform the Code required exercise testing.

Exercising the listed valves with flow would require using the Emergency Core Cooling System (ECCS) pumps to inject water into the reactor due to relatively high accident flow rates required for full stroke exercising of the valves. Additionally, the injection line nozzles associated with the Residual Heat Reinoval System are not equipped with internal spargers. General Electric Service Information Letter 401 identifies problems with injecting water through this flow path and potential damage to nuclear instrumentation or fuel assemblies which could occur if this flow path were used for other than emergency conditions. For these reasons performing the Code required check valve testing with flow creates a hardship without providing a compensating increase in the level of quality and safety.

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Part 10 also allows check valve disassembly at refuehg outages as an alternative to the valve obturator movement described in Paragraphs 4.3.2.4(a) or (b). However, check valve disassemoly is not a preferred attemative.

The proposed alternate testing is in accordance with a previously approved edition of the ASME Boiler and Pressure Vessel Code and will provide an acceptable level of quality and safety.

3.2.2 Alternative Testina The licensee proposes:

Obturator movement for the listed valves will be demonstrated in accordance with the 1980 Edition of the ASME Boiler and Pressure Vessel Code,Section XI,

. Paragraph IWV-3522(b), as follow:

A mechanical exerciser shall be used to move the disk. The force or torque delivered to tne disk by the exerciser will be limited to less than 10% of the equivalent force or torque represented by the minimum emergency condition pressure differential acting on the disk, or to 200% of the actual observed force or torque required to perform the exercise on the valve when the valve is new a.2d in good operating condition, whichever is less.

The force or torque required to full-stroke exercise the listed valves to the open position will be measured.

3.2.3 Evaluation and Conclusion Use of a mechanical exerciser to demonstrate valve obturator movement is permitted by OM-10, Paragraph 4.3.2.4(b), and Code relief is not required. However, Paragraph 4.3.2.4(b)

. requires specifically that the force or torque of initial movement (breakaway) be measured and

, compared to a reference value. Measuring the force or torque of the initial movement provides important information for determining how the valve would initially break away from its seat.

The proposed test, performed in accordance with Section XI, Paragraph IWV-3522, and previously allowed by the Code, does not require the measurement of, and comparison to a reference value, the breakaway force or torque. Therefore, the proposed test would not provide equivalent information required by OM-10, Paragraph 4.3.2.4(b). Also, the licensee has not demonstrated, at this time, that there is any hardship, burden or impracticality to performing the Code-required measurement of breakaway force or torque using the mechanical exerciser.  ;

Therefore, relief request VRR-002 is denied. I It should be noted that the licens)e's proposed alternative of performing the test in accordance with Section XI, Paragraph IWV-3522 was previously allowed by the Code and would provide i useful information about a check va!ve. The staff considers use of Section XI,  !

Paragraph IWV-3522 to be acceptable, and its use would not require relief if the force or torque of initial obturator movement is measured and compared to a reference value in accordance  ;

. with Paragraph 4.3.2.4(b) of OM-10.

Principal Contributor: Y. S. Huang l

Date: April 21, 1999 L-