ML17345A963

Requests Assessment of Large Diameter Pratt Purge & Vent Valve Operability & Intentions to Maintain Valves Sealed Closed in Accordance W/Srp & Operable in Event of DBA-LOCA

ML17345A963
Person / Time
Site:	Turkey Point
Issue date:	02/16/1983
From:	Varga S Office of Nuclear Reactor Regulation
To:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
References
NUDOCS 8303040111
Download: ML17345A963 (9)

Text

DISTRIBUTION fgg I 6 Igggcket Foie RRC PDR Local PDR ORB 1 File D. Eisenhut OELD E. L. Jordan E.

Reeves A<<r<~r D. McDonald C. Parrish NSIC J.

M. Taylor ACRS (10)

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He1temes Docket Nos.

50-250 and 50-251 Dr. Robert E. Uhrig, Vice President Advanced Systems and Technology Florida Power and Light Company

'Post Office Box 529100 Miami, Florida; 33152

SUBJECT:

~COMPLETIOH OF VALVE OPERABILITY REVIELIS FOR LARGE PRATT BUTTERFLY VALVES USED FOR PURGE OR VENT OF COHTAINMENTS AT TURKEY POINT PLANT UHITS 3 AND 4 In our letter of November 28, 1978, we identified the generic concerns of purging and venting of containment to all operating reactor licensees and requested your response to these concerns.

Our review of your response was interrupted by the TMI accident and its demands on staff resources.

Consequently,.

an Interim Position on containment purging and venting was transmitted to you by letter dated October 23, 1979.

You were requested to implement short-term corrective actions to remain in effect pending completion of our longer term review of your response to our November 28, 1978 letter.

One of the remaining interim corrective actions (and the subject of this letter) still in place while our longer term review is being completed is to:

"Maintain the containment purge and vent isolation valves closed whenever the reactor is not in. the cold shutdown or refueling mode until such time as you can show that:

a.

All isolation valves greater than 3" nominal diameter used for containment purge and venting operations are operable under the most severe design basis accident flow condition loading and can close within the time limit stated in your Technical Specifications, design criteria or operating procedures.

The operabi1ity of butterfly valves may, on an interim basis, be demonstrated by limiting the valve to be no more than 30'o 60'pen (90'eing full open).

The maximum opening shall be determined in consultation with the valve supplier..

The valve opening must be such that the critical valve parts will not be damaged by DBA-LOCA loads and that the valve will tend to close when the fluid dynamic forces are introduced."

Your letter of June 8, 1979, provided your commitment to operate in confor-mance with this Interim"Position pending completion of our long-term review of valve o erabilit.

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Dr. Robert E. Uhri g FF.B 1 6 1983 However, recent information concerning the operability of large-diameter Pratt butterfly valves (of the generic family RlA or HR1A) in the event of a DBA-LOCA has raised concern whether your justification for operability provides the required assurance that these valves. will close.

Enclosure 1 provides the background information and the bases for our concern.

Therefore, pursuant to 10 CFR 50.54(f), you are requested to inform us in writing within 15 days of receipt of this letter:

1.

Your assessment of the operability of your large-diameter Pratt purge and vent valves in light of the concerns outlined in Enclosure 1, and 2.

Hhether or not you intend to maintain the purge and vent valves sealed closed in accordance with Standard Review Plan Section 6.2.4, II.6.f and to verify them to be closed every 31 days whenever. the reactor is not in the cold shutdown or refueling mode-until such time as you submit acceptable information that demonstrates that your large-diameter Pratt purge/vent valves will operate in the event of a DBA-LOCA.

This information will enable the Commission to determine whether or not further action should be taken to modify, suspend, or revoke your license.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, ONB clearance is not required under P.L.96-511.,

Sincerely, Original signed by/

S. A. Varga Steven A. Varga, Chief Operating Reactors Branch fl Division of Licensing

Enclosure:

As stated cc w/enclosure:,

See next page RB OFFICE%

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83 NRG FORM 310 t10-80) NRCM 0240 OFFIClAL RECORD COPY USOPO: 1981~960

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Robert E. Uhrig Florida 'Power and Light Company cc:

Harold F. 'Reis, Esquire Lowenstein,

Newman, Reis and Axelrad 1025 Connecticut

Avenue, N.M.

Suite 1214 l'ashington, D.

C.

20036 Norman A. Coll, Esquire

Steel, Hector and Davis 1400 Southeast First National Bank Building Miami, Florida 33131 Mr. Henry Yaeger, Plant Manager Turkey Point Plant Florida Power and Light Company P. 0.

Box 013100 Miami, Florida 33101 Mir. Jack Shreve

.Office of the Public Counsel Room 4, Holland Building Tallahassee, Florida 32304 Administrator Department of Environmental Regulation Power Plant Siting, Section State of Florida 2600 Blair Stone Road Tallahassee, Florida 32301 Resident Inspector Turkey Point Nuclear Generating Station U. S. Nuclear Regulatory Commission Post Office Box 1207

. Homestead, Florida 33030 James P. O'.Reilly Regional Administrator Region II U. S. Nuclear Regulatory Commission 101 Marietta Street - Suite 3100 Atlanta, Georgi'a 30303

EhCLOSURi 8=-ckoround On August 3, 1982, the evaluation was co,",.pletc.:d for the P inch Pratt butterfly purge valves at Three Hile Island 1 (TMI-'1).

The qualifica-tion on these valves vas found to be

$ nscfficient to deranstrate ttm ability of these valves to close in the event of a LOCA accident.

The major reason for this finding was the determination that the shaft stress would exceed allowable stress when experiencing worst case LOCA torque loads.

A number of operating plants have Pratt butterfly valves of the sme

'eneric family '(R1A or t/R1A) and approximate size as the 48 inch RlA butterfly valves.at Three Mile Island. 1.

Some of'these plants have agreed to maintain these valves sealed closed in operating modes above cold shutdown.

A larger number of plants, ho~ever, do operate these valves for some period of time during operating

modes, opening the valve to a limited maximum opening.

The limitation on maximum valve opening has been determined by the licensees in consultation with the. valve vendors in accordance with the Staff Interim Position of October 23, 1979.

The basis for this position'was that for most butterfly valves the highest torque lo'ads under flow woul'd occur at the higher angles of opening.

Sub-sequent testing has revealed that for some valve installations downstream of an elbow the higher torques may be experienced at smaller angles of.

opening but for the large majority of valve installations the higher torque at higher angles is valid.

For most of the butterfly valves used for purgino and venting operations a maximum opening limitation of 50 degrees has produced sufficient con-fidence in the valve's ability to close in the event of a LOCA to allow con'tinued use of these valves while qualification was progressing.

In June

1981, ho~ever, Henry Pratt Yalves began to inform utilities

"'perating with 48 inch and larger RlA and HRlA model valves that addi-tional restrictions might be required for these valves in order to assur e the ability of these valves to close under LOCA loads.

Aqcord-ing to Pratt analyses,.the valve restrictions wmuld be a t."aximum opening of 30 'degrees to 55 degrees, depending on the individual valve or operator.

Since that time, a numb'er of qualification reports for these valves have been submitted for RRC staff review.

The najority'of these reports have been performed'or valves closing from the full open (90 deg. ees) position.

These analyses have shown the valves to be overstressed for this angle of opening.

Pratt has recommended smaller maximum angles of opening for,.

these valises but no analysis has been done to show the acceptability'of operating the valves at the lower angles of opening.

Tvo of the licens'ees have submitted reports calculating valve and operator stresses at the lower angles of opening.

These reports were the Turkey Point 3 and 4 report submitted Septembei 17, 1982 by Florida Power and Light (FPE L) and the

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Three Mile Island (THI-1) report submitted by General, Public Utilities (GPU).

As previously stated, the THI-1 report was evaluated on August 3, 1982 and found insufficient to qualii'y the valves to close aaainst LOCA loads.

The Turkey Point 3 and 4 report was for 48 inch and 54 inch Pratt RlA butterfly valves.

These valves were to be blocked to 35 degrees and 30 degrees respectively.

The, peak containment pressure was not used in qualifying these valves but rather a percentage of that pressure by taking credit for the fact that these valves would begin to close before the containment would reach its peak pressure.

Enveloping static seismic loads of gx = 3, oy = 3 and gz = 4 were used in analyzing the 48 inch valve but actual required seismic loads of gx = 1.5, gy = 1.5 and gz = 1.15 were used in analyzing the 54 inch valve.

The calculated shaft stresses for the Turkey Point 48 inch and 54 inch valves were 27,861 psi and 26,534 psi respectively.

The analysis used a shaft stress allowable of 30,000 psi.

This value was based on the ASf1f allowable of 1.5 Sm for pressure retaining code parts.

Effectively, 30,000 psi would be a minimum yield strength.

At t'his point a small amount of permanent deformation would be experienced.

The calculated values are 93 percent and 88 percent of this yield point leaving small

. margins.

In addition, the values calculated were determined on the basis of strai,ght l.ine aoproach flow.

'The actual installation.

nf'hese valves have elbows and bends upstream which would d)stor1 the flow profile to these valves and change the torques experienced by these valves.

Tests performed on other model valves have shown the effect of upstream elbows as increasing the torque by as much as 100 percent.

As no information has been submitted to date on the effects of upstream elbows on this model valve, it is uncertain what the magni-tude of the increase on torque would be on this valve.

The small margins remaining for the shaft stress for these valves is inadequate to cover the concern of upstream elbows.

Consequently, the qualifica-tion submitted for the Turkey Point 3 and 4 valves is insufficient to demonstrate the ability of these valves to close against LOCA loads.

Although there are some design differences in the Rlh series of butter,-.

fly valves installed in purge and vent syste'ms of operating nuclear

plants, the inadequacy of the analysis submitted to,qualify these valves to'cl'ose, in conjunction with the fact that the analyses submitted for the THI-1 and Turkey Point 3 and 4 were for the lowest angles of open-ing, indicates that the Interim. Position of October 23, 1979 is insuf-.

ficient to provide adequate assurance that the RlA series

Pratt, butter-'ly valves used for purging and venting in nuclear pla'nts vill close in the event of a LOCA.

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