ML20085M395

Ro:Describing Possible Backseating Disc Mislocation Problem on 2-inch Darling Valves on S-350 Wdd Welding End.Valves Repaired.Valve Stems Will Be Changed During Next Refueling Outage

ML20085M395
Person / Time
Site:	Peach Bottom, Point Beach, 05000000
Issue date:	10/29/1973
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M392	List: ML20085M390 ML20085M395
References
NUDOCS 8311080436
Download: ML20085M395 (4)

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. October 29, 1973 Directorate of LicensingMr. John F. O' Leary, Director U. S. Atomic Energ ,

Washington, D. C. y Cc= mission 20545

Dear Mr. O' Leary:

DOCKET NOS.

FACILITY OPERATING LICENSE NOS50-266 AND 50-301

- BACKSEATING DISC MISLOCATION PROBLPOINT EM ON 2" DARLING VALVES Technical Specifications for Poi tin accordance with Section 1 n

Operating License Nos. DPR-24 and Beach DP R-27), Nuclear Plant (Facility 'L.

a possible generic problem with a cate this report describes stalled at Point Beach Nuclear are 2"

. goryPlant of 2" gate valves in-TheS-350 valves C in question disc ga,te valves with lip sealsNo. D welding end, outsid Darling Valve and Manufacturingompany. ,

and C are manufactured by thee screw and yo Point lb. valves. Beach Nuclear Plant

• are saf The tvalves used at e y class I, ASA series 1500 f~

September 15, 1973,An investigation of excess letdou '.

lead to an in n line leakage on of September on valve IMOV-129926 1973. on Unit 1 (excess letdspection and subsequent its downstream s, eat protruded fr the. valve disc was fully withdrawn fInspection e that of the val by its backseating ring, the disc seat ring when reinserting. rom co u the ldom guides,the valve body such that as allowed previous valve closings.Four stream marks on the seat ringlipindicated of the dowcatch the " lip" n- that the dis Internal damage to the valve consic had caught portion of the the upstream and downstream discs downstream seat ringof a fine sted vertical c foundstream to be dislightly bent also and Two locating pins betweenock positi down ofsthe split disc valve were in the damage.sc were evident. ome facial scratches to the There was no metal loss involved 83110g043b7310b gDR ADOCK 05000 7

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October 29, 1973-o .

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' Repair of the valve involved rounding the lip of the seat ring to prevent future hangups of the disc. The thin ver-tical crack in the downstream seat could not be fully lapped out during the repair. Accordingly, a manual valve was added to the system downstream of 1MOV-1299 to back up the root valve. Valve 1MOV-1299 thereby remains effective and operable as a remotely l

controlled root shutoff valve, but is considered not totally capable of effecting completely tight shutoff without some through-leakage.

At the time, measurements indicated that the location of the backseating ring on the valve stem was too low but this could not be assuredly determined. If such was the case, this would allow the split discs to fully clear the seat rings when the valve was fully open and backseated. The tendancy for inter-ference to occur between the downstream disc and seat during valve closing could be expected to increase if there was flow through the valve, creating a differential pressure which could swing the loose hanging disc onto the lip of the seat.

There are six similar 2" Darling valves in each unit at Point Beach Nuclear plant.

In addition to the above mentioned 1299 valve, valves 270A & B (normally open) are installed on the reactor coolanu pump seal return lines. These valves are. rarely operated in the life of the plant. Also, valves 598 and 599 on the reactor coolant system drain line are of this type. These valves are never operated during normal pressurized and power operation. The sixth,similar valve on each unit is MOV-427 on the normal letdown line. The function of valve 427 is to close in the event of low pressuriner level and, in closing, cause the closure of the containment isolation valves 200 A, B and C, via an interlock. None of the Darling valves described in this re-port are containment isolation valves.

Valve 1MOV-427 was investigated during a Unit 1 shut-down on October 13, 1973, af ter it was reported that' it would not fully close remotely. Manual manipulation of the valve on Septem-ber 28, 1973, had shown that at approximately one-half shut and again just prior to closing, the valve operation became sticky.

Tests were conducted at that time to verify that IMOV-427 was capable of performing its primary function of initiating an iso-lation signal for the letdown line. The slightest movement of the valve off its backseat was found to be sufficient to activate the interlocks and close the AOV-200 letdown isolation valves.

Measurements indicated that the discs of 1MOV-427 when Attachment B

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backseatedclOedtheseatrineeand1 lar problems as experienced in IMOV-1299.

e va1ve egen to simt-Inspection showed no damage to valve 1MOV-427 other than a slight marking of the upper edge of the seat ring, similar to that found in 1MOV-1299. Before closing up the valve, the seat ring edges were rounded to aid in guiding the discs down between the seats. The " valve opan" limit switch was then set for 2-1/4", 5/16" less than the maximum back-seating position of 2-9/16". Valve cycling tests were then con-ducted satisfactorily.

During the same shutdown, valve IMOV-270B was cycled manue11y with no evidence of stickiness or disc hangup. At the completion of repair of 1MOV-427, on October 13, 1973, it was concluded from measurements taken, operating experience and tele-phone discussions with the valve manufacturer, that, indeed, a dimension error could exist with respect to backseat locations on the stem. With these confirmations, it was concluded that all twelve valves of this type would require investigation on a sche-dule commensurate with the plant operating schedules.

Valves IMOV-1299, 2MOV-1299 and 2MOV-427 will be electrically limited similarly to 1MOV-427. Valve IMOV-1299 will be completely changed out during a convenient shutdown fol-lowing the receipt of a new valve. New valve stems with back-seats located so that full opening of the valve will not permit the discs to lose the guide effect of the seats have been ordered and will be fitted in the remaining valves at convenient shut-downs. The service of the 598, 599 and 270A & B valves is such that it is not considered necessary to change the stems of these valves until the next refueling shutdown of each unit.

The nuclear steam supply system supplier has been in-formed about the problems encountered with these valves.

Very truly yours, -

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Sol Burstein Senior Vice President cc: Mr. James G. Keppler ,

Regional Director Directorate of Regulatory Operations, -

Region III l '

,a Attachment B Page 3 of 3

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Directorate of latory Operations Bulletin 74 dated January 3, 1974 Distribution: ,

Chief, Field Suppbrt and Enforcement Branch Deputy Director, RO Assistant Director for Construction and Operation, R0 (3)

Assistant Director for Radiological, Environmental, and Materials Protection, R0 Director, Office of Operations Evaluation, RO Assistant for Plans and Programs, RS Director, DL Deputy Director, DL Deputy Director for Tecnnical Review, DL -

Assistant Director for Bk'R's, DL (3)

Assistant Director for Pk'R's, DL (3)

Assistant Director for Operating Reactors, DL (3)

Assistant Director for Environmental Projects, DL (3)

R. F. Fraley, ACRS Files R Central Files cc: Letter addressed to Licensee w/ encl w/o distribution and address list NSIC R. L. Shannon, ITIIE (TIC)

Chief, Regulatory News Branch, IS PDR Local PDR I

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