ML20058H079

Part 21 Rept Re BVPS Unit 2 Suction Valves for Rs Pumps Supplied by Henry Pratt Co,W/Regard to Inadequate Discharge Pressure.Temporary Mod Made to Four Affected Suction Valves Which Will Properly Position & Retain Spline Adapter

ML20058H079
Person / Time
Site:	Beaver Valley
Issue date:	12/03/1993
From:	Freeland L DUQUESNE LIGHT CO.
To:	NRC
References
REF-PT21-93 NUDOCS 9312100277
Download: ML20058H079 (6)

Text

' OU TEL: 412-645- 576 Decbo93 1d:49 No.uus r.u AttOchment 1

• Page 1 10 CFR Part 21 '

BVPS Unit No. 2 - Suction Valves for the Racirculation SDray Pumns (i) Name and Address of Individual Making Notification:

L. R. Freeland, General Manager, Nuclear Operations Duquesne Light Company s Beaver Valley Power Station i

P.O. Box 4 Shippingport, PA 15077 (ii) Basic Component Affected:

Motor-operated suction valves (2RSS-MOV155A, B, C and D) ,

for the Recirculation Spray Pumps which are utilized for long term core cooling capability and maintaining the containment pressure subatmospheric in the event of a Loss of Coolant Accident (LOCA). The valve is a 12" Henry Pratt Butterfly Valve (Model 1400).

(iii) Firms Supplying Components:

Supplier: Henry Pratt Company 401 South Highland Ave.  ;

Aurora, Illinois 60506-3392 (iv) Nature of Defect:

During shutdown mode testing of Recirculation Spray Pump '

(2RSS-P21D), the pump developed inadequate discharge pressure. Subsequent investigation discovered that the  :

disc of the motor-operated valve (MOV) on the suction of the pump was not engaged to the motor operator. The shaft splina adapter of the motor-operator had moved out of position becoming separated from the adapter drive sleeve. ,

The spline adapter is retained in the motor operator by an adapter plate which is in turn supported by a valve bonnet piece. The retention is accomplished by limiting'che through-hole diamatars of the adapter plate and bonnet piece to a value that would not allow the' spline adapter ,

to move out of position. Both diameters were intended to i

be the same for the above valve. If the adapter plate diameter is larger than the diameter of the bonnet piece, the spline adapter could be retained by the bonnet piece.  ;

0701 l 9312100277 931203 PDR s ADOCK 05000412 roe gg/[/ p',

.NOU TEL: 412-643-8376 Dec 03 93 15:50 No.003 P.03 AttOchment 1 Page 2 10 CFR Part 21 DVPS Unit No. 2 - Suction Valves for the Recirculation Borav Pumps (continued)

However, this arrangement would provide insufficient spline engagement (see attached sketch). For the Beaver Valley Power Station Unit Number 2, the adapter plate and bonnet piece-plate were provided by the valve manufacturer. The valve is a 12" Pratt Butterfly valve (Model 1400) with a Limitorque HBC Operator.

This design deficiency was also noted on the other three Recirculation Spray Pump Suction Valves for pumps 21A, 21B and 21C. Therefore, common mode failure of the suction valves for all four recirculation spray pumps potentially existed if gone ' undetected. The deficiency was found during shutdown mode conditions. The investigation leading to the failure determined the suction valve

[2RSS-MOV155D) failed during either the recent outage static MOV testing or pump flow testing. This investigation confirmed the operability of the suction valves during power operation.

Duquesne Light Company (DLC) reviewed the original purchase order file, applicable vendor documents, and the maintenance history associated with the Henry Pratt valves (2RSS-MOV155A, B, C & D). DLC determined that there was no work activity or initiating problem that could have led to modification or replacement of the adapter plate and/or bonnet at BVPS during construction or subsequent power operations and that the adapter plates are in their "as received" condition.

Safety Implications:

If the failure had gone undetected, the possibility existed for a common mode failure of all four suction valves to the Recirculation Spray Pumps which would have prevented long term core cooling capability and Containment cooling in the event of a LOCA. The suction valves are normally in the "open" position and will receive a signal to open on a containment Isolation Phase "B" (CIB) to ensure the suction valve of the pump is-open. However, the valves are stroke tested on a quarterly basis. The potential for the valve disc of the Mov to become disengaged from the motor operator due to this common mode defect could have resulted in the valves becoming disengaged in the " closed" position. The operations staff would not have had knowledge of this condition because the limit switches would have indicated "open" in the control room.

i

.N00 TEL:412-643-8376 Dec 03 93 15:50 No.003 P.04 '

Attachment 1

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Page 3 10 CFR Part 21 BVPS Unit No. 2 - Suction Valves for the Recirculation Borav Pnuns (Continued) I i

Also postulated was the failure of the recirculation spray pump 21D as a result of the defect of the suction valve 2RSS-MOV155D (purple train powered) in conjunction with a  ;

single failure of the opposite train pump 21C (orange train powered). When the low-low level setpoint of the Refueling Water Storage Tank is reached after Safety i Injection initiation, the C and D Rocirculation Spray l Pumps (2RSS-P21C, D) begin to support long-term core '

i cooling by providing water from the containment sump to the suction of the High-Head Safety Injection Pumps.

Since the Recirculation Spray Pumps 21C and 21D are the only two pumps capable of recycling water back to the Reactor Coolant System, the injection phase via the Recirculation Spray System, in conjunction with single failure, cGuld have been lost as a result of this defect.

Therefore, the defect, if gone undetected, could have created a major degradation of essential safety related equipment, and a required safety system may not have performed its function. As such, the defect is reportable pursuant to 10 CFR Part 21 requirements.

(v) Date On Which Defect Identified!

The failure of the Recirculation Spray Pump Suction Valve identified on October 17, 1993 during (2RSS-MOV-155D) was the regularly scheduled pump performance test required by Tech Spec 4.6.2.2. The evaluation and resulting report was presented to our Onsite Safety Committee on December 2, 1993.

(vi) Number and Incation of. Components:

Affected Components: BVPS Unit No. 2 Recirculation Spray Pump Suction Valves (2RSS-MOV155A, B, C and D)

Location: BVPS Unit No. 2 1 Safeguards Building I

I l

l .NOU TEL:412-643-8376 Dec 03 93 15:51 No.003 P.05 l I

Attachment 1 Page 4 10 CFR Part 21 BVPS Unit No. 2 - Suction Valvas for the Recirculation Sorav Punns (Continued)

(vii) Corrective Actions Takant l An inspection was conducted of the adapter plates and l bonnets of all similar valves supplied by Henry Pratt. It l was concluded that the only valves affected by this defect l are the four recirculation spray pump suction valves (2 l RSS-MOV155A, B, C and D). l A temporary modification was made to the four suction valves which will properly position and retain the spline adapter. A temporary clamp device has been secured to the valve shaft for all four valves to provent axial movement of the spline adapter. The device has been tested and visually observed to confirm proper operation. )

Replacement adapter plates and bonnets will be procured <

for the subject- valves. Installation of the replacement hardware has been scheduled for the next refueling outage (2RS). In the interin, the temporary modifications to che four valves will ensure proper operation.

l (viii) Other Advice Related To Purchasers or Licensaan:

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TEL:412-643-8376 Dec 03 93 15: 49 No.003 P.01 1

Duquesne Ught Company Nuclear Group '

Nuclear Opretions Unit 1

FAX Transmittal To: N12 C.- D Ds_v .2 + i o n 3 C_.e_n & s. e l t (

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Telephone: 301- 992-818'7' FAX Number:  !

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Location: Beaver Vallev Power Station Plant OfNce (Mail Dron BV-P1)  ;

I Telephone: 39 3 -S i o I FAX Number: (412)-843 - 8376

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