REGULAT INFORNATION DISTRIBUTION STEH (RIDS)

ACCESSION NBR: 8608140272 DOC. DATE: 86/08/08 NOTARIZED: NO DOCKET 0FACIL: 50-275 Diablo Canyon Nuclear Pouer Plant> Unit 1> Pacific Ga 05000275

50-323 Diablo Canyon Nucleav Power Plant> Unit 2> Paci fic Ga 05000323AUTH. NAl'iE AUTHOR AFFILIATION

SHIFFER> J. D. Pacific Ga's Zc Electric Co.RECIP. NANE RECIPIENT AFFILIATION

VARGA> S. A. PWR Pv object Directovate 3

SUBJECT: Forwards qualification of isolation capability of 12-inchcontainment Vacuum Overpressure Relief Valves FCV-662>FCV-663> Zc FCV-664 aftev LOCA> per commitment Zc TNI ActionItem II. E. 4. 2. "Containment Isolation Dependability. "

DISTRIBUTION CODE: A04>tD COPIES RECEIVED: LTR J. ENCL f SIZE:TITLE: OR Submittal: TMI Action Plan Rgmt NUREG-0737 Zc NUREG-0660

NOTES

REC IP IENTID CODE/NANE

PWR-A ADTSPWR-A EICSBPWR-A PD3 LASCHIERLING. HPWR-A RSB

INTERNAL: ACRS 34AEQD/PTBIE/DEPER DIR 33NRR BWR ADTSNRR PWR-A ADTSNRR/DSRO EjitR ITRGN5

COPIESLTTR ENCL

1

2 21 0

1

1

10 101 1

1

1 1

1 1

1

1 1

RECIPIENTID CODE/MANE

PWR-A EBPWR-A FOBPWR-A PD3 PD 01PWR-A PSB

*DN/LFNBELD/HDS2IE/DEPER/EPBNRR PAULSON> W.

NRR PWR-B ADTSEG 04

COPIESLTTR ENCL

1 1

1

5 51

1 00

3 31

1

1

EXTERNAL: LPDRNSIC

0305

2 21

NRC PDR 02 1 1

TOTAL NUMBER OF COPIES REQUIRED: LTTR 42 ENCL 39

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PA.CIFIC GA.S A.ND ELECTRIC COMPANY77 BEALE STREET ~ SAN FRANCISCO, CALIFORNIA94106 ~ (415) 781.4211 ~ TWX 910 372 6587

JAMES D. SHIFFERVICE PIIK5INNT

NIICLTARPOWIII OfNTRATION

August 8, 1986

PGandE Letter No.: DCL-86-233

Hr. Steven A. Varga, DirectorPHR Project Directorate No. 3Division of PHR Licensing-AOffice of Nuclear Reactor RegulationU. S. Nuclear Regulatory CommissionNashington, D.C. 20555

Re: Docket No. 50-275, OL-DPR-80Docket No. 50-323, OL-DPR-82Diablo Canyon Units 1 and 2NUREG-0737,'tem II.E.4.2, Containment Isolation Dependability

Dear Hr. Varga:

Diablo Canyon Unit 1 License Condition 2.C.(6)g, Diablo Canyon Unit 2 LicenseCondition 2.C.(5)b, and related supplements to the Safety Evaluation Reportrequire that PGandE demonstrate 12-inch containment vacuum/overpressure reliefvalve operability in accordance with the appropriate Standard Review Plansections prior to startup after the first refueling outage. The enclosure,"gualification of Isolation Capability of 12-Inch ContainmentVacuum/Overpressure Relief Valves FCV-662, FCV-663, and FCV-664 After aLoss-of-Coolant Accident," fulfills PGandE' commitment to provide anevaluation of the operability of the 12-inch containment vacuum/overpressurerelief valves. The NRC Staff's evaluations of containment isolationdependability are documented in SSER 9, SSER 14, and SSER 31.

The methodology used to evaluate the 12-inch containment vacuum/overpressurerelief valves was similar to that previously used for the 48-i nch containmentpurge supply and vent lines. This methodology was accepted by the NRC Staffin SSER 9. The evaluation was performed based on the relief valves blocked tothe maximum 45 degree open position and a limit of 50 degree opening, whi ch iswithin the Technical Specification limit for these valves (TS 3.6.1.7 andBases 3/4.6.1.7).

The evaluation demonstrated that the 12-inch valve closure time does notexceed 5 seconds, consistent with Branch Technical Position CSB 6-4 itemB.l.f. Technical Specification 3.6.3 currently requires a 10 second closuretime for these valves. A license amendment request will be submitted torevise Technical Specification 3.6.3 to require a 5 second closure time forthese valves.

8608140272 860808PDR ADOCK 05000275P PDR

Hr. S. A. VargaPGandE Letter No. DCL-86-233August 8, 1986Page 2

The evaluation demonstrates that the 12-i nch relief valves conform to thecri teri a set forth in Branch Technical Position CSB 6-4 and Standard ReviewPlan 6.2.4 in NUREG-0800. Since PGandE plans to maintain these valves with ablocked maximum 45 degree open position, this evaluation of both 45 degree and50 degree openi ngs satisfies the requirements of the license condition forUnits 1 and 2, Item II.E.4.2 of NUREG-0737, and SSERs 9, 14, and 31. In theevent that PGandE desires to unblock these valves, an evaluation for theunblocked condition will be submitted to the NRC Staff for revi ew.

Kindly acknowledge receipt of this material on the enclosed copy of thisletter and return it in the enclosed addressed envelope.

Sincerely,

gCJ. D. Shi ffer

Enclosure

cc: L. J. Chandler3. B. MartinH. H. HendoncaB. NortonH. E. SchierlingCPUCDiablo Distribution

0896S/0047K/DY/809

PGandE Letter No.: DCL-86-233

ENCLOSURE

DIABLO CANYON PONER PLANT

, UNITS 1 AND 2

QUALIFICATION OF ISOLATION CAPABILITYOF 12-INCH CONTAINMENT VACUUM/OVERPRESSURE

RELIEF VALVES FCV-662, FCV-663, AND FCV-664AFTER A LOSS-OF-COOLANT ACCIDENT

'l.l General

C 0

PGandE has elected to maintain the DCPP Units 1 and 2 12-inch containmentvacuum/overpressure relief valves FCV-662, 663, and 664 (relief valves)blocked to prevent opening beyond 50'90's full open) for the life of theplant. NRC Standard Review Plan 6.2.4 requires an evaluation of thecontainment purging system if an open path is provided from the containment tothe environs during normal plant operation. This report presents theevaluation and qualification of the isolation capability of the relief valvesafter loss-of-coolant accidents (LOCAs). The evaluation of the relief valvesused similar methodology to that previously used by PGandE for the 48-inchpurge supply and vent valves. The previous evaluation was accepted by the NRC

Staff in SSER 9 (June 1980), and the NRC Staff concluded that the evaluationand methodology comply with the criteria contained in NRC Branch TechnicalPosition (BTP) CSB 6-4, "Containment Purging During Normal Plant Operations."

1.2 V lv e ifi ati n

The relief valve specifications are:

12-inch containment vacuum/overpressure relief valveItem No. 31 FCV-662, FCV-663, and FCV-644Valve manufacturer: Fisher ControlsType: ButterflyModel: 9120Actuator: Bettis 722B-SR (Figure 1 of the Attachment shows thevalve/actuator arrangement)

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1.3 0 eratin ndi i n

The operating conditions for the evaluation are as follows:

The subject relief valves are normally closed and have been permanentlyblocked to prevent opening beyond 50'90's fully open). The

evaluation of these valves below the 50'osition provides assurance ofsafe operation during postulated LOCA events.

The vacuum/overpressure relief line will not be used when the purge/ventlines are used.

2. EvALIVAETI N

The evaluation scope covers:

~ System design, maintenance, and surveillance test program

~ Dynamic analysis

~ Radiological consequence assessment

2 1 tern D i n M in n n e n urv ill n T t Pr r m

The containment vacuum/overpressure relief line is part of the containmentisolation system, and as such, meets all of the standards appropriate toengineered safety features.

The redundant inside and outside containment vacuum/overpressure relief valvesare on separate safety trains, and each valve has a spring return actuatorclosing on loss of air. These valves also close on loss of electrical power.Therefore, no energy sources are required to close these valves.

The vacuum/overpressure relief line will not be opened when the 48-i nch

purge/vent valve is open. The subject valves are manually controlled,pneumatically actuated, and are installed in the orientation of pressurerelief as the normal flow direction.

The maintenance and surveillance tests performed for these valves areconsistent wi th those for other engineered safety features and include leaktest, position switch test, close-time test, and isolation signal test.

2.2 D namic Anal i

The dynamic analysis method used is similar to that used and previouslyaccepted by the NRC Staff (SSER 9) for the DCPP 48-inch purge and ventvalves. A brief description of the general approach, the method, the results,and the criteria used follows. Due to the insignificant mass of the disc,

0896S/0047K

stresses in the disc shaft and key due to seismic events are very small and,therefore, not considered. The Attachment provides a discussion of theequations used in the analysis, which are similar to those previously used andsubmitted to the NRC Staff for the 48-inch purge/vent valves.

The purpose of dynamic analysis is (1) to determine the valve closing timeafter receiving the isolation signal, and (2) to establish the stress levelsin the critical structural parts of the valve, namely the disc shaft and thekey.

The dynamic analysis method is summarized by the following steps:

~ The valve disc dynamic equation of motion was defined in terms of:

Disc mass moment of inertia (I)Disc aerodynamic characteristics (aerodynamic torque Td)Cylinder spring effect (spring torque Ts)Actuation effect (actuator torque Ta)

~ The spring force of the actuator cylinder (which includes the nonlinearand frictional effects) as a function of valve disc opening angle wasobtained from an in-situ test. The test results are shown in Figure 2 ofthe Attachment in the form of a hysteresis curve. This force was used tocalculate the spring torque, Ts, in the first step.

~ The disc dynamic equation of motion was solved numerically in small timeincrements under the driving force of LOCA containment pressuretransients to obtain the closure time and the disc angular velocity atclosing.

~ The disc shaft and key stresses at valve closing were conservativelycalculated by assuming that all of the impact kinetic energy istransferred as strain energy in the angular deflection of the shaft.

The dynamic equation of motion was derived by coupling the flow and discdynamics to the aerodynamic torque expression provided by the valvemanufacturer, Fisher Controls.

Three cases of LOCA containment pressure transients as shown in Figure 3 ofthe Attachment were analyzed:

Case 1 — Double-ended cold leg ruptureCase 2 — Double-ended pump suction ruptureCase 3 — 3 ft2 pump suction rupture

These cases envelop the longest valve closure time and the maximum discshaft/key stress. The results of the evaluation for the three LOCA cases aresummarized below and show that in all cases the valve closure times andstresses are much less than allowable.

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4

COMPARISON OF RESULTS FOR LOCA CASES

(Values Shown for 45'nd 50'pen Positions)

~It ms

LOCA~ss 1

LOCACase 2

LOCA

CmMAllowable

V 1

*ValveClosureTime (sec.)

3.42/3.51 3.48/3.59 3.88/4.01 5.00

Stress inKey (psi)

5,468/5,708 5,522/5,732 5,533/5,706 39,500

Stress inShaft (psi) 10,550/11,010 10,650/11,060 10,670/11,010 67,000

*NOTE: 1. The Technical Specifications require these valves beblocked to limit opening to 50'. The valve blocks arenominally set to 45 .

2. The maximum valve closure time measured duri ng the onsi tetest under normal plant operation (including the 0.5second signal delay) is 3.25 sec.

2.3 Radi 1 i 1 n uence As m n

The 12-inch vacuum/overpressure relief valves are significantly smaller thanthe 48-inch purge/vent valves, and they are permanently blocked to a maximum45'alve opening. The 48-inch purge/vent lines will not be usedsimultaneously with 12-inch vent/overpressure relief line. In SSER 9, the NRC

Staff concluded that radiological consequences associated with use of the48-inch purge/vent valves are within the guidelines of 10 CFR 100. Since anydose released to the outside through the 12-inch vacuum/overpressure reliefvalves will be less than that which would result if the 48-inch purge/ventvalves are open, the radiological consequences associated with use of the12-i nch vacuum/overpressure relief valves are within the guidelines of10 CFR 100.

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3. MMARY F RE LT

Based on the evaluation described herein, PGandE concludes that the 12-inchcontai nment vacuum/overpressure relief valve isolation capability isdemonstrated, in that:

The system design meets the standards of engineered safety features;maintenance and surveillance test programs currently performed areadequate and will ensure operability of the relief valves.

The valves will be closed within 5 seconds (including a 0.5 second signaldelay time) after a LOCA.

The maximum stress in the disc shaft and key are well within allowablestress limits.

Radiological consequences following a LOCA are wi thi n 10 CFR 100

guideline values.

The relief valves conform to the criteria specifi ed in Branch TechnicalPosition CSB 6-4 and Standard Review Plan 6.2.4.

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Attachment

DESCRIPTION OF ANALYSIS OF

12-INCH VACUUM/OVERPRESSURE RELIEF VALVES

0 namic Characteristics of Valves and Actuators

The actuators are a scotch-yoke arrangement (Figure 1) which uses a push-pullaction of the two pneumatic actuators to open a valve. Pneumatic pressure inthe actuator cylinders maintains a valve in the open position. A signal toclose a valve opens a solenoid valve which relieves the pressure in theactuators and allows a spring 1n one of the actuators to close the valve.

A1r flowing through the valve creates an aerodynamic lift effect which acts ina d1rection to close the valve. In all normal operat1ng modes, there is a

very small differential pressure across the valve; consequently, theaerodynamic torque is insignificant and is counterbalanced by the pneumaticactuators.

Time-Histor Anal sis of Valve Parameters

A FORTRAN computer program, VALVE, has been developed to calculate valve andactuator parameters as a function of time for LOCAs descr1bed 1n the DiabloCanyon FSAR (Figure 3). This Attachment briefly describes the analyticalmodel and calculation methods of the computer program.

~In ut Outa

l. Containment pressure (psig) as a function of time (seconds) after a LOCA

is stored in arrays CP and TAL, respectively.

2. The left s1de of the actuator/valve hysteresis curve (measured pressureand position data for closing of valves) is entered,in the arrays LSHCA(abscissa) and LSHCO (ordinate).

3. The valve pressure/flow characteristic (CV) and valve position (degreesopen) are stored in the arrays CV and CVVP, respectively.

4. The containment temperature (degrees F) and time (seconds) after the startof a LOCA are entered in the arrays CT and CTT, respectively.

5. Water vapor saturation volume (cubic feet/pound) and pressure (psi) arestored in the arrays SV and PSV, respectively.

6. The aerodynamic torque coefficients ( 1nch pounds/psi) and valve position(degrees) are stored 1n arrays ATCS and ATCA, respectively.

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Cal cul at) on of Parameters

Predicted valve position (PVP): The valve position can be accuratelypredicted by using the calculated valve position (VP), angular velocity (AV),and angular acceleration (AA), which were calculated in the previouscalculation interval. (The time increment (hT) = constant = 0.005 seconds.)

V AV . T AA . (hT) 2

The predicted valve position is used to determine the actuator parameters(actuator position, pressure force, spring force, net torque, and actuator airvolumes).

After the valve position is calculated (based upon calculated torques,acceleration, velocity, and valve pos1tion during previous interval), thedifference between valve position and predicted valve position is calculated.for accurate results, this difference is kept very small (0.02').

The geometric model is shown in Figure l. The valve actuator is ad)usted sothat when the actuator arm is at a 45'ngle (THETA), the valve position isfully open ( i.e., 90').

THETA = PVP —45'P

= 2.5 + 2.5 tan (THETA)AVSL = (77) (AP)

Actuator Pressure and Standard Air Volume

The model uses an instrumentation time delay of 0.5 seconds between the t1meof the containment isolation pressure setpoint (3 psig) and the open1ng of thesolenoid valves to relieve the actuator pressure. When the solenoid valve isopen, the actuator air loss rate is based upon the equat1on:

Q = 963 CVThP

Q: Flowrate SCFHhP: Differential Pressure, psig

T: Degrees RankineCV = 0.35

If the solenoid valve has not opened, the actuator pressure ( P) is predictedfrom the a1r volume at the current position and the air volume and pressure ofthe previous calculation interval.

Aerod namic Tor ue

The aerodynamic torque is calculated by the formula

Taero = (A + 8) ~ hP + C

where A and C are constants. A = 28.8, C = 1200 inch pounds/psi for thesevalves, and 8 is a funct1on of valve type and valve posit1on. The coeffic1ent8 is named ATCHT 1n the program and is read from the arrays ATCA and ATCO

for the calculated valve posit1on in each time interval.

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H steresis Curve

The measured valve posit1on versus actuator pressure data is presented inFigure 2. In each calculation interval, the net torque on the disc, the nettorque on the disc during the previous calculation interval, and the previousposition on the hysteresis curve are used to determine the current position onthe hysteresis curve.

Acceleration Velocit and Position of Valve Disc

The angular acceleration (AA), angular velocity (AV), and valve position (VP)are calculated at each time step hT as follows:

Net Tor uen+1 Mass Moment of Inertia

AVN~l = AVn + AAn~l . hT

VPn+1 = VPn + AVn+l T + AAn+l ~2

(LiT)2

Ca ab111t of Valves to Withstand the Effects of Slammin Shut

The angular velocity of the valves at the time of closing was calculated indegrees per second. The kinetic energy of the valve would be part1allyabsorbed in the seating of the valve. The rema1ning kinetic energy would bestored in torsional strain energy in the twisting of the shaft. The valvedisc energy would be absorbed in the hysteresis of the actuator and the energyrequired to seat the valve.

The calculations g1ven below verify that the shaft and shaft-keys havesufficient strength to withstand the closing forces. The method that is usedin the calculations is to assume that all of the kinetic energy of the disc isstored as strain energy in the angular deflection of the shaft, calculate theangular deflection, determine the torque assoc1ated with 1t, and determine theresulting stress on the shaFt keys.

Kinetic Energy = Strain Energy:

l/2 IWMAX MAX

2 2

8MAX = wMAX / IL/~G

Maximum Shaft Torque:

T = JGOMax/L

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Force on Shaft Keys:

F = 1/2 Tr

Shear Stress:

Ss = F/A

Bearing Stress:

(Formula from Formulas for Stress and Strain, Roark, 6th Edition,page 334.)

Sb = 2 Ft/b21

Haximum Shear Stress:

( )HAX (2 )b 2 2

where

G:

b:

e eHAX:

mass moment of inertia

moment of inertia

shear modulus

angular velocity at impact

disc shaft length

length of shaft key

width of the shaft key

thickness of shaft key

angular shaft rotation

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'

~G0

4+r0

Cr

Ao

FIG, 1A 12 IN. CONTAINMENT VACUUM/OVERPRESSURE RELIEF VALVE

SCHEMATIC

g+

FIG, 1B 12 IN, CONTAINMENT VACUUM/OVERPRESSURE REI IEF VALVE

DISK DRIVING MECHANISM

70.

60.

50.Linearly Extrapolated

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

40.o

WCC

CQAa 30.

Closing Case

DM

o20.

CQ

10.

0. 10. 20. 30. 40. 50. 60.

Figure 2

ACTUATOR PRESSURE (PSIG)12 inch Containment Vacuum/Overpressure Relief ValveClosing Hysteresis Curve

C580

~Q

DOQSLE ENDEI COLO LEe RVPTURE

DOVbLE nOED etwas SVCTIOI RVtTNE

IO

3.0 FT IN'VCTIN NQPTNE2

O. I

TlltE (SEC)

IO IOO

Figure 3. LOCA CurvesFSAR UPDATE

UNITS I AND 2 l

DIABLO CANYON SITE

CHFhINMENT PRESSURE TRANSIENTSBLOMDOWN PHASE

~ & W