ML17354A251

Requests Info Re Any Change in Schedular Commitments for Installation of Debris Screens Pending Resolution of Operability Concerns Per long-term Review of Containment Purge & Vent Valves.Assessment of Valve Operability Encl

ML17354A251
Person / Time
Site:	Turkey Point
Issue date:	02/10/1983
From:	Varga S Office of Nuclear Reactor Regulation
To:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
References
NUDOCS 8302240137
Download: ML17354A251 (22)

Text

Fee

>o 1983 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:

LONG-TERM REVIEW CONTAINMENT PURGE AND VENT VALVES TURKEY POINT UNITS 3 AHD 4 DISTRIBUTION Docket NRC PDR L PDR NSIC ORBNl Rdg DEisenhut OELD JMTaylor ELJordan ACRS-10 CParrish DMcDonald EReeves Gray.

By letter dated August 31, 1981, we identified the components and status of our long-term review for containment purging 'and venting during normal power operation of Turkey Point Plant, Units 3 and 4.

Subsequently, your letter dated November 17, 1982 provided a commitment to install debris screens on the purge supply and exhuast valves during the next refueling outage for each unit.

We found this acceptable as stated in our letter dated Februaryl1,~ T983.

Recent information concerning the operability of large-diameter Pratt butterfly valves (of the generic family glA or HR1A1) in the event of a DBA-LOCA has railed concern.

Your report dated September.

17, 1982, provided calculations for valve and operator stresses at the lower angles of opening.

Enclosure 1 provides the background information, our initial assessment of your subnittal, and the basis for our concern.

I We request that you;provide any change in your scheduldr commitments for installation of the debj is screens pending resolution of the. operability concerns.

We have performed a generic evaluation of the. radiological consequences of accidents while pur'ging or venting at power.

To assure that the generic evaluation is valid for Turkey Point Plant, Units 3 and 4, wh verified the adequacy of Technical Specifications

.1imits on iodine equilibrium and the valve closure times.

The Safety Evaluation, Enclosure 2, provides the details of our review.

The valve operabiltty concern identified in Enclosure 1 is the only item remaining unresolved for this rather complex issue we identified in our letter of November 28', 1978.

The staff is reconsidering the adequacy of 8302240i37 8302i0 PDR ADOCK 05000250 P

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Docket No 50-250 an 50-251 Dr. Robert E.

hrig,.Vice President Advanced System and Technology Florida Power an Light Company Post Office Box 52 00 Miami, Florida 331 DISTRIBUTION Docket NRC PDR L

PDR NSIC ORB81 Rdg DEisenhut OELD JMTaylor ELJordan ACRS-10 CParrish DMCDonald EReeves Gray

SUBJECT:

LONG-TERM REVI CONTAINMENT PURGE AND VENT VALVES TURKEY POINT UNIT 3 AND 4 By 1etter dated 'August 31, 1981 we identified the components and'tatus op our long-tenn revteu Vor conAanment purgtng and venttng duutng normal power operation of Turkey Point Pla t, Units 3 and 4.

Subsequently, your letter. dated November 17, 1982 provi ed a commitment to install'ebris screens on the purge supply and exhau valves during the next refueling outage for each unit.

We found this ac ptable as stated in our letter dated February l., 1983.

Recent information concerning the operabili of large-diameter Pratt butterfly valves (of the generic family R1A o NRlA) in the event of a DBA-LOCA has raised concern.

Your report date/ September 17, 1982, provided calcula'tions for valve and operator stl esIses at the loWer angles

- ~f opening.

Enclosure 1 provides the background conformation,aourtinitial "assessmentcof-your~ubmittal, and the basis for o r concern.

G.

We request that you provide any change in your schedular commitments, for installation of the debris screens pending resolutioh<of the operability concerns.U-We have performed a generic evaluation of tge radiological

, consequences of accidents while purging or venting at pb er.

To assure that the generic evaluation is valid for Turkey Point Pla t, Units 3 and 4, we verified the adequacy of Technical Specification lim s on So'dine equilibrium and the valve closure times.

The Safety Evaluate n, Enclosure 2, provides the details of our review.

The valve operability concern identified in Enclosure 1 is the onl item renaining unresolved for this rather complex. issue we identified in r

letter of November 28, 1978.

The staff is reconsidering the adequacy f the interim position of October 23, 1979, which allows power operation OFFICE/

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0 Dr. Robert E. Uhrig the Justification for the inter im position of October 23, 1979, which allows power operation with the valves blocked in a partial open position.

Me will inform you of our decision and any.- required action on your par t.

Sincerely,

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Steven A. Varga, Chief Operating Reactors Branch 81

.Division of Licensing

Enclosures:

1.

Evaluation and Request"'for Additional Information 2.

Safety Evaluation-Radiological, Consequences of Accidents klhile Purging or Venting at Power cc w/enclosures:

See next page

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Enclosures:

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Evaluation and Request 'for Additiona't Information 2.

Safety Evaluation-Radiological Consequences of Accidents >thi'le Purging or Venting at Power cc ~f/enclosures:

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Dr.,Robert E. Uhrig the justification for the interim,position of.October 23, 1979, which allows power operation with, the valves blocked in a partial open position.

We will inform you of our decision and any required action on your.part.

Sip I

erely,

Enclosures:

1.

Evaluation. and"Request for Additional Information 2.

'Safety Evaluation-Radiological Consequences of Accidentsi While Purging or Yenting at Power cc w/enclosures:

See next page

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

'Harold F. Reis, Esquire Lowenstein, Newman, Reis and Axelrad 1.025,Connecticut

Avenue, N.W.

Suite 1214 Washington, 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.

Mr. Jack Shreve Office of the, Public Counsel Room 4, Hol,land Building Tallahassee, Florida 32304 Administrator, Department of Environmental.Regu'!ation Power Plant Siting Section

'State of Florida 2600 Blair Stone Road Tallahassee, Florida 32301'esi'dent 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, Georgia 30303

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I OPERABILITY ASSESSMENT TTERFLY V VES R A OR NR1A ENCLOSURE 1

~ Q4sP Backoround On August 3, 1982, the evaluation was completed for the 48 inch Pratt butterfly purge valves at Three Mile Island 1 (TMI-1).;The qualifica-tion on these valves was found to be inscYficicnt to demonstrate the 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 wou1d exceed allowable stress when experiencing worst case LOCA torque loads.

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

'eneric family (RlA or HRIA) and approximate size as the 48 inch RlA'utterfly 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,

however, do operate these valves for some period of time during oper'ating

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 witli 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 would 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 purging 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 continued use of these valves while qualification was progressing.

In June

1981, however, Henry Pratt Valves began to inform utilities

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

At;cord-ihg to Pratt analyses, the valve restrictions wou1d be a maximum opening of 30 'degrees to 55 degrees, depending on the individual va1ve or 'operator.

Since that time, a number of qualification reports for these valves have been submitted for NRC staff review.

The majority of these reports have been performed for valves closing from the full open.(90 degrees) position.

.These analyses have sho~n the valves to be overstres'sed for this angle of opening.

Pratt has recommended smaller maximum angles of opening for:.

these valves but no analysis has been done to show thy acceptability af.

operating the valves at the lower angles of opening.

Two of the 1icens'ees have submigted reports calculating valve and operator stresses at the lower angles of opening.

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

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Three Nile Island (TNI-1) report submitted by General Public tltilities (GPU).

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

Evaluation The Turkey Point 3 and 4 report was for 48 inch and 54 inch Pratt Rlh 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, gy = 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 ASME allowable of 1.5 Sm for pressure retaining code parts.

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

At this 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 stra$ qht l.ine aooroach flow.

The actual installqtinne nf these valves have elbows and bends upstream which would d>stort 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 Nuch 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 aagni-tude of the increase on torque would be on this valve.

The saall aargins 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.

Concern Although there are some design differences in the RlA series of butter fly valves installed in purge and vent systems of operating nuclear plants, the inadequacy of the analysis submitted to qualify these valves to'close, 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, raises concerns as to the adequacy of the justification for Interim

'Position of October 23, 1979.

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ENCLOSURE 2 GENERIC EVALUATION OF THE RADIOLOGICAL CONSEQUENCES OF ACCIDENTS. WHILE PURGING OR VENTING AT POWER Introduction The release of radioactivity through vent or purge valves from a potential large LOCA at power has been considered generically to assure that such events do not constitute an undue hazard to the people residing around operating reactor sites.

To evaluate the radiological consequences of such accidents, the following assumptions have been made:

a.

vent and purge valve isolation signals, circuitry and purge

.valve actuation are reliable; b.

purge system isolation valve closure times.are generally sufficient to prevent the release of activity associated with fuel failures that could follow a large break (a total accident elapsed time of about 15 seconds or less);

c.

maximum allowable coolant iodine equilibrium and spiking activity limits do not exceed those contained in Standard Technical Specifications (STS);

d.

fission products generated by pipe breaks are reflective of coolant activity and fuel failures estimated using 10 CFR Part,;

50, Appendix K, a'nalysis techniques; and e.

radiological consequences'f accidents while purging or venting would be bounded by those produced by a large break.

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Evaluation A large number of staff evaluations of the radiological consequences of LOCA's have been performed for construction permit, operating license, operating license amendment, and Systematic Evaluation Program reviews.

In; addition, a generic assessment of the amount of radioactivity that could be released while venting and purging from a spectrum of pipe breaks through the range of purge valve sizes utilized by industry has been made.

In virtually all cases, the contribution through vent or purge valves is estimated to be of the order of 2 percent, or less, of the Exclusion Area Boundary (EAB) and outer boundary of the Low Popula-

.tion Zone (LPZ) doses that would occur from a large break LOCA in which a source term indicative of a substantial melt of the core with subse-quent release of appreciable quantities of fission products is assumed.*

For dose assessments in which only activity in primary coolant systems would be released, or for events in which fuel failures indicative of 10 CFR Part 50; Appendix K, LOCA analyses are indicated, EAB and LPZ dose

'1

.estimates are substantially less than dose estimates made for a large break LOCA assuming a substantial fuel melt.

Since the magnitude of the vent or purge contribution to severe LOCA dose estimates is small compared to other LOCA scenarios within design

bases, we conclude that the consequences of such accidents are within applicable dose guidelines.

Estimates based upon SRP analysis techniques and 10 CFR Part l00.11.

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Plant S ecific The following plant specific information. for Turkey Point, Units 3 and 4,

,was verified to assure that the important assumptions for the generic evaluation are valid as applied to Turkey Point 'Units

3. and 4:

1.

Reactor Coolant Activit The maximum limits on i6dine equilibrium is required to be 1.0 microcuries/gram during normal operation and 30.microcuries/

gram during power transients.

These.l.imits are. defined in the Technical Specifications, Section 3, for Turkey Point Plant; Units 3 and 4.

2.

Valve Closure Time The valve closure time is required to be.less than.about 10 seconds.

The licensees submittal,- dated. January 20, 1982,.indicates the maximum, closure time is 5 seconds.

Conclusion A generic assessment of the radiological consequences of, large break'ccidents,-'including a resulting severe LOCA of the type. hypothesized for site suitabil,ity purposes, while venting or purging, at power indicates that the dose contribution through open valves is small.

Therefore, we find tota1 accident radiological consequences of such accidents wou1d be less than the dose guidelines of 10 CFR Part

)OO.

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