ML20030B807
| ML20030B807 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 08/05/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20030B802 | List: |
| References | |
| NUDOCS 8108240238 | |
| Download: ML20030B807 (5) | |
Text
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-ENCLOSURE 4
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO MECHANICAL'0PERABILITY OF PURGE / VENT _ BUTTERFLY VALVES 0,
ALABAMA POWER COMPANY i
JOSEPH M. FARLEY NUCLEAR PLANT, UNIT NO. 1 DOCKET N0. 50-348 Introduction and PurJe Valve Description The containment purge systems have the capability to purge the containment through 48.0-inch butterfly valves or 18-inch (mini-purge) butterlfly valves.
The 48-inch valves have been used for limited purge operations while the 18-inch valves have been used for essentially continuous purging during
. plant operation.
Ecch of the valve assemblies consists of valve body, operator, and pilot solenoid valve manufactured by H.lPratt, Bettis, and ASCo respectively.
l The operator: are air to open-spring to close type. When the soldnoid valve is energized, the operator (piston) is air loaded to open the valve.
When decnergized, the operator is vented and the spring force acts to close the valses.
Evaluation.
Alabama Power Conaany's ( APCo) evahation~df the purge / vent system butterfly valves were revitwed against the applicable criteria of Standard Review Plan 3.9.3, Rev.1, "ASME Code Clast 1, 2, and 3 Components, Component Supports,
and Core Support Structures," and staff " Guidelines for Deronstration of Operability of P' urge and Vent Valves," which were seri to all licensees by letter dated September. 27,1979. This review was accomplished by the Equipment Qualification Braach, Division of Engineering, NRR in conjuction with Brookhaven National Laboratory.
f A.,18-Inch Mini-Purge Valves The following information was submitted by APCo and reviewed by the staff and its consultants, Brookhaven National Laboratory, in order to assess the.
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operability of the 18-inch mini-purge valves; p
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Reference A:
Alabama. Power Company letter, August 14,1980 'Farley 1 and 2), F.L. Clay'on Jr. to A. Sunwencer.
Reference B:
Alabama Power Company letter, December 10, _1979. ( Fa rl ey 1),
j F.L. Clayton, Jr. to A. Schwencer.
ii Reference C:
Teleconf 9/19/80:
Restivo (BNL), Zudans/Kintner (NRC),
George (APCo), Gallager/3el: (Bechtel).
Reference 0:
Alabama Power Company letter, September 30,180 (Farley 2),
F.L. Clayton, Jr. to A. Schwencer.
Reference E:
Alabama Power Company letter, November 4,1980 (Farley 2),
F.L. Clayton,. Jr. cto A. Schwencer.
The following sections summar.ize the highlights of our rev.ien. The details l
of the review are contained in Brookhaven National Lacoratory letter dated November 12, 1980 from T.J. Restivo to J.J. Zudans.
Mechanical Evaluation (Valves)
APCo has indicated (Reference A) that the subject vai<es are designed to the recuirements of the ASME Boiler and Pressure Vessei Code - Section III.
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tabulation (Table 1) is provided to show stress levels calculated by H. Pratt j
vs. stress allcwables for the valves' critical components based on the loac-ings resulting from the DSA postulated.
Components such as the shaft, disc to shaft pins, etc., were listed.
As examples, the combined maximum stress in the : haft is determined to be 25,077 psi (33,700 psi allowable) and the maxi-num shear stress in the upper disc to shaft pin (uppe-) given as 5812 psi (5'.60 psi allowable).
The stress analysis is based on APCo/Pratt having defined the major force and l
- orque loads acting on the components during the postulated DBA-LOCA.
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ioadings are predicated on the containment pressure condition assumed and are
The SPs used to deternine' dynamic torques for the 18-inch valves are conservatise.
Typically, the maximum Td is developec at disc angles above 70 l
open (90 = full cpen).
The AP used to determine the maximum Td was 24 psig l
which was based on the containment pressure (Pc) reacning 34 psig at the point of fall valve clesure at 6.0 seconds into the LOCA (Reference A, Attachment 1).
In actuality the-AP acre:s a single valve at these higher disc angles would be significantly less due to piping entrance and exit losses, pipe / duct losses, Ind' losses across the valve in series with the one being analyzed.
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D Also to be considered is that the actual containment pressure is.less than-
-24 psig-shen the valve _ position is above 70 'open.
If the stroke time vs.
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' disc angle is assumed to be. linear, the containment pressure would only be
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a p roximately 10 psig.when the disc angle reaches 70' (Reference-A,
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This would also tend to reduce the AP across the valve.
U Based on the information presented,~the staff finds that APCo has satis-y factorily demonstrated that the subject 18-inch valve assemblies are y'
adequately designed to withstand the LOCA-related loads resulting from the ascending ~ differential. pressures of APCo's DBA-LOCA condition as the valves close from the full open (90 ) position.
i jystem Evaluation (Ducts-Valve Disc Inferference-Debris)
The mini purge supply'and exhaust system inlets in:ide the containment build-4 ing arc fabricated ductwork. - The duct operdogs are located outside the primary shield wall and away from any lines whose rupture would initiate a LOCA.
The duct openings are screened with 0.5-inch mesh, 0.047-. inch wire to pre' vent debris from entering or blocking the ducts.
The design of.the duct-work.inside containment emphasized minimizing the length of the ductwork so
- that flow-developed pressure drop through the ductwork remains negligible.
j Due to'the minimization of ducting, the elimination of potential debris and the low approach velocities, the staff agrees with APCo that ductwork damage i
l Iinside containment and therefore interferences with the cicsure of the valves j
is unlikely.
The piping between the inside anc outside mini purge velves is fabricated with a design pressure rating in excess of the peak LOCA pressure.
In the mini purge system ductwork outside of cont'ainment, the postulated flow ar.d pressure conditions will tend to cause overpressurization failures of tne cuctwork.
These failures have low pro:: ability of interference with the
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closure capability of the valves.
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All the ducting and piping which is part of the mini purge system has been
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cesigned to maintain structural integrity under the seismic event postulated for these facilities.
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Seismic Evalus'. ion (Valve Assemblies)
I In Reference A, APCo has indicated that the valve and operator assembly art seismically qualified by static analysis using a seismic nertial load of
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3.0 g acting simultaneously in the horizontal and vertical directions.
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analysis was performed-in accordance with IEEE-344 (1971).
4 In its recent review of the licensee application for Farley 2, the s.taff has 4
evaluated-the seismic qualification program conducted by APCo for'the Farley plant.
The staf f concluded that this program, which included the qualifi-cation of the purge valves, provided reasonable assurance that the seismic L
Category I mechanical and electrical equipment are adequately qualified seismically.
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'9 Environmental Evaluation (Actuator, Solenoid and Main Valve Sealing Device)
I The 18-inch mini purge valves use ASCo pilot solenoid valves to actuate the Bettis operators.
The review of environmental qualification concerning these solenoid valves wil' '- included in the staff's overall review of the environ-mental qualification of equipment being p~erformed in accordance with the Commission Memorandum and Orde- (CLI-80-21) dated May 23, 1980.
In Reference D, APC' describes Bettis operators used inside containments as being qualified for the expected environment- ?ollowing a design basis acci-dent. Qualification levels for the various environmental conditions are presen ted. Qualification is based on material programs rather than testing an assembled prototype operator, In Reference E, APCo indicated that Bettis recomme ds replacement of the operator seal kits en a regular basis with intervals not to exceed five yea rs.
This replacement cycle is said to be based on industry standards for minimizing maintenance work and associated equipmen' downtime and not for maintaining a qualified design life of tne material.
Based on this, APCo will replace the operator seals every five years as recommended.
The upgraded Technical Specifications for Unit No. I will include this as a surveillance item.
With respect to the valve body seals, APCo has indicated th?t no p reven-tive maintenance is necessary for these components.
Th n has been confirmed by a vendor representative.
However, information now exists to indicate that seal deterioration may go undetected unless tests are run more frequent-ly.
Refer to Enclosure 1 to the fonvarding letter for the basis for new Tcchnical Specification surveillance te:ts being recommended to assure valve
' leak tightness.
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f8-InchPurgeValves APCo is presently committed to maintaining these valves closed whenever Farley 1 and 2 are in operational modes 1, 2, 3, and 4 The upgraded Techni-cal Specifications for Unit No. I will include this as a Limiting Condition of Operation.
ARCO is evaluatino these va7ves for operability under LOCA conditions. Oper-ability assessment information is to be submitted by ARCO at a later time.
However, the 8-inch, fully qualified valve system described in Enclosure 3 to the forwarding letter would appear to negate a need for attempting to qualify su:h a large valve.
(See BTF CSB 6-4 Fosition B.1.C).
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3 Some information -for these valves has baen provided in Reference A.under j
18-inch mini-purge valves conce ning preventive maintenance and inspection.
The va':<e manfacturer's recommendation to flush the top and valve trunnions' with silicone grease and inspecting valve seats will be performed at refuel-t ing outages. APCo has indicated that degradation of the valve seat material will be noted based on unsatisfactory results df the yearly local leak rate test.
O The staff considers; more frequent local leak rate tests are needed to ci~
note degradation of sealing capability as with the 18-inch valves. ' Also, i
these seals should be replaced on an interval not to exceed five years.
Based on the above, the staff finds that the 48-inch valves will success-
- fully maintain containment isolation during postulated loss-of-coolant acci-dents if they. are maintained sealed closed during modes 1, 2, 3, and 4,
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with resident seals replaced at five-year intertals, and the seat leakage i
surveillance performed at the recommended frequency.
Evaluation Summary Based on the licensee provided information, the staff finds that APCo has j
satisfactorily demonstrated that the 18-inch mini-purge valves are capable of closure from a full 90' open position when subjected to the. loading associated with postulated loss-of-coolant accidents.
The staff finds that the seismic qualification of the valves and operators i
is acceptable. The staff finds that the environnen'tal qualification of the I
Jalt0 components are accepta51e (except as noted for the main valve seals).
An evaluation of the associated electrical equipment for these valves will i
be included in the staff's overall review of the environmental qualification of equiprent being performed in accordance with the Commission Memorandum i
and Order (CLI-80-21) dated May 2 3, 19 80,-_
The staff finds that the piping-ducting-debris evaluation performed by the licensee acceptably demonstrates that these mini-purge system components will not affect valve closure and sealing.
The staff considers that changes are necessary to the existing Technical Specifications to assure that an adequate margin of safety exists for both the 48-inch and the 18-inch purge system valves.
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