ML20084H698

Ninth Interim Deficiency Rept Re Potential Design Deficiency in Valve Yoke to Motor Mount Weld.Initially Reported on 740514.Util Is Replacing 12-inch Globe Valve in Test Return Line W/Larger Globe Valve & Orifice Plate Combination

ML20084H698
Person / Time
Site:	Browns Ferry
Issue date:	08/05/1976
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20084H694	List: ML20084H692 ML20084H696 ML20084H698 ML20084H702 ML20084H706 ML20084H709
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8305040744
Download: ML20084H698 (4)

Text

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E 5 -M i Mr. Normann C. Moseley, Director 4 $ /o Office of Inspection and Enforceenent s U.S. Nuclear Regulatory C - 4=sion .

. Region II - Suite 818 t g JJ 230 Peachtree Street, NW. 3- , M/

Atlanta, Georgia 30303 ,, %g,g, g Dear Mr. Moseley f;

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BROWNS PERRY NUCLEAR PLANT UNITS 2 AND 3 - POTENTIAL DESI , , _ . ,

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DEFICIENCY IN VALVE YOKE TO MOTOR MOUNT WELD Initial report of the subject potential deficiency was made on May 14, 1974, and was followed by our June 14. July 15, ,h Anasust 12, September 13, 1974, January 15, 1975 March 3 O C and March 17, 1975, letters, J. E. Gilleland to Donald F. -

Knuth. An eighth interim report was submitted to John G. . p  % 7/  ;

Davis from J. E. G111m1==d on March 30, 1976. Because the -

i yoke to motor base welds of PCV-74-58 in unit i failed, &

similar valves (FCV's 74-58 and 74-72) in units 2 and'3 may '

s V)- N be subject to the sanne type of failure. NO; ,, -b

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f The ninth interim report of DDN 191 is enclosed.

Very truly yours.

J. E. Gilleland Assistant Manager of Power Enclosure CC (Enclosure):

Dr. E. Volgenau, Director /

Off. ice of Inspection and Enforcasesnt U.S. Nasalaar Regulatory Comunission Washington, DC 20555 l

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'An Equal Opportunity Employer

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ENCLOSURE BRORNS FERRY NUCLEAR PLANT UNITS 2 AND 3 POTENTIAL FOR FAILURE OF THE WELD BETWEEN THE YOKE l AND MOTOR MOUNTING PLATE FOR FLOW CONTROL VALVES (FCV'S) 74-58 AND 74-72 NINTH INTERIM REPORT DDN}.91 On May 14, 1974, an intial report regarding the subject deficiency was made by telecon to W. S. Little, AEC-DRO Inspector, Region II. The report was made by L. D. Weber and J. A. Raulston in compliance with 10CFR50 55(e).

There have been eight subsequent interim report dated June 14, 1974; July 15, 1974; August 12, 1974; September 13, 1974, January 15, 1975; March 3, 1975; March 17, 1975; and March 30, 1976. The initial report was made because the weld between the yoke and motor mounting plate of FCV 74-58 (4-inch globe valve) in the RHR test return line torus spray connection failed in unit 1. Since the unit 1 failure appeared to be vibration related, the corresponding valves and valves in close proximity, such as FCV 74-59 (12-inch globe valve), in units 2 and 3 were assumed to potentially be subject to a similar type of failure.

The eighth interim report summarized the Southwest Research Institute (SwRI) report on their initial phase of testing and their evaluation of the RER system test return lines for potential vibration induced component failures.

It also presented a proposed solution, consisting of the addition of a flow restricting orifice downstream of the 12-inch globe valve in the test return line. This orifice would provide sufficient back pressure on the 32-inch valve to effectively reduce downstream cavitation and its associated induced vibrations. However, the addition of orifices in the discharge lines of the RER pump runout (DDR 224) Creatly reduced the pressure drop available for any orifice located downstream of the 12-inch globe valve.

After installation of the RHR pump discharge line orifice and the RHR test return line orifice, several tests were performed to determine the effects the addition of the orifices would have on test return line flow and flow induced vibration. The flow rates achie'ved' in units 1 and 2 met the

. minimum flow requirements (8000 gpm per pump, total 16,000 gpm per loop) established by General Electric for two RHR pump operation, but they provided very little margin. The flow rates in unit 3 exceeded the minimum flow requirements (8000 gpm per pump, total 16,000 gpm per loop), but also with limited margin.

Preliminary results for units 1 and 2 on the vibration measurements performed by SuRI-indicate that cavitation and vibration levels have been reduced very little from those observed earlier uithout the pump or test return line orifice

- plates ' original design). The very large hole. required in the test return line orifice plate, because of the addition of the RHR pump discharge line orifice, has ' rendered the test return line orifice relatively ineffective in reducing cavitationi The CURL . rece:.mendation is to replace the 12-inch globe valve with a drag-type valve (or equivalent) of appropriate size.

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o.. o Preliminary results for unit 3 on the vibration measurements performed by SwRI indicate that cavitation and vibration levels have been reduced significantly from those observed earlier without the pump or test return line orifice plates (original design). However, the relatively large hole required in the test return line orifice plat,e, because of the addition of tbe RHR pump discharge line orifice, has rendered it somewhat ineffective in reducing cavitation to very low levels. SwRI is also recommending the replacement of the 12-inch globe valve on unit 3 with a dra6-type valve (or equivalent) of appropriate size.

TVA is teking steps to replace _ the 12-inch globe valve in the test return line with a larger globe valve and orifice plate combination or with a drag-type valve (or equivalent) on all Browns Ferry units. This commitment is intended to provide increased margins in the test return line flow and reduce the flow induced vibrations downstream of the valve to low values.

After installation of the new valves, flow and vibration measurements will be taken to verify the final configuration.

Before replscement of the valves, the test return lines on units 1 and 2 will not be operated at high flow (> 12,000 gpm) unless required for special testing or emergency operation. This restriction has been recommended by SuRI and should minimize flow-induced vibration and associated fatigue.

In addition, the test return line orifice plates will be removed from units 1 and 2 because of their ineffectiveness. A sparger will be installed on each test return line discharge to disperse the flow. Whenever feasible, both test return lines will be used to avoid prolonged high flow operation.

The test return lines on unit 3 vill be equipped with orifice plates and spargers. The effect of spargers on test return line flow and vibration

' was found during testing to be inconsequential. They are being added to minimize suppression chamber flow induced vibration. There will be no operating restrictions on unit 3.

A final report will be prepared and submitted after the 12-inch 61obe valves have been replaced with drag-type valves and after confirmatory testing has been completed. ,

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