ML19210D640

Forwards Addl Info Re ECCS & RHR Pumps in Response to NRC 791022 Ltr.Advises That Offsite Dose Calculation Manual Still Under Preparation & Will Be Submitted for Review by 791231

ML19210D640
Person / Time
Site:	Mcguire, McGuire
Issue date:	11/21/1979
From:	Parker W DUKE POWER CO.
To:	Baer R Office of Nuclear Reactor Regulation
References
NUDOCS 7911270417
Download: ML19210D640 (5)

Text

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. y DUKE POWER COhiPANY Powra Butt.ntxo 420 SocTn Cauncu Srazer, Cunt.orrz, N. C. a824a W I L LI AM O. PA R K E R, J R.

v'cc Pats.cca November 21, 1979 retc.-c ~ c: ^a c. 7c.

Sica Peooverion 373 4cs3 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attention: Mr. R. L. Baer, Chief Light Water Reactor Project Branch #2 Re: McGuire Nuclear Station Units 1 and 2 Docket Nos. 50-369, 50-370

Dear Mr. Denton:

Attached is Duke Power Company's response to the request for additional information transmitted by Mr. Robert L. Baer's letter of October 22, 1979.

Please be advised that the revised Offsite Dose Calculation Manual is still under preparation. It is our intent to provide this document for staff review by December 31, 1979. This is identified as item number 24, Radio-logical Effluent Tec ical Specifications, on the staff's milestone chcrt.

V y truly yours, y'

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'WilliamO. Parker,Jr.[

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ENCLOSURE 1 Answers to Request for Additional Information McGuire Nuclear Station McGuire Milestone Item 1 (ECCS Pump NPSH)

a. The equation (signs applied as shown), the actual data and the results of the calculations of available NPSH for the Residual Heat Removal Pumps are presented in Enclosure 2. It should be noted, that no credit is taken for containment sump water level. This conservatism accounts for an additional minimum available head of 4.5 feet based on the minimum LOCA injection volume for McGuire of 238,005 gallons.

b. The results presented in Enclosure 2 were based on a maximum RHR pump runout flowrate of 5300 gpm. This maximum flowrate exceeds the RHR purp runout flagrate (5157 gpm) measured during pre-operational testing.

For the in-plant test, the RHR pump discharge piping alignment was setup for the recirculation made of operation; however, the RHR pump suction piping'was aligned to the RWST. If the pump suction had been aligned to the containment sump, then pump runout would have been less than the 5157 gpm measured because of the difference in elevation head between the RWST and the sump.

Therefort, the 5300 gpm flowrate used in the calculation of NPSH is conservative.

c. The McGuire si.mp screen design changes were analyzed by Alden Laboratory and the results ware included in our August 30, 1979 letter. The reduction in screen area changed the total entrance losses from 0.4 to 0.6 inches of water.

This loss was included in the NPSH calculations as shown in Enclosure 2.

McGuire Milestone Item 31 (RWST Capacity)

An alarm has been added to the McGuire switchover design to occur at automatic switchover level (73,431 gallons). This will alert the operator that the RHR pumps have been switched over automatically and that the remaining ECCS pumps must be switched over manually using the procedure in Table 6.3.2-3 starting with step

3. An analysis 'is presented in Enclosure 3 in support of these added measures.

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ENCLOSURE 2 (Sheet 1 of 2)

Available Net Positive Suction Head (NPSH)

For Residual Heat Femoval Pumos To demonstrate that adequate NPSH is p'ovided for '.ke Residual Heat Removal pumps, calculations were performed for the recirculation mooc which is the most limiting alignment for NPSH requirements. Available NPSH is determined from the following operation:

NPSH = (h) containment - (h) vapor + (h) static - (h) loss actual pressure pressure head To evaluate the adequacy of the available NPSH, several conservatisms are applied:

a. No increase in Containment pressure from that present prior to the accident is assumed.

b. The Containment sump fluid temperature is assumed to be 190* F even though the maximum temperature reached is approximately 173'F (see Figure 6.2.1-26).

c. The static elevation head is calculated from the floor eyelvation of the sump (elevation 725' + 0") instead of the available water level. The elevation of the spray pump is 699'+6" (centerline of discharge pipe).

d. The head loss is evaluated based on all pumps running at the maximum runout flow with conservatively assumedfriction factors.

e. The required NPSH is based on one pump running at its maximum runout flow.

Using all of these conservative assumptions, the minimum NPSH available is calculated to be 23.4 feet and the NPSH required is 21.5 feet. The actual available NPSH will always be greater than the calculated value.

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ENCLOSURE 2 (Sheet 2 of 2)

NPSH Verification Data For RHR Pumos Pump runout flowrate, gpm 5300 Containment pressure, psia 14.34 Vapor pressure @l90*F, psia 9.34 Sump bottom elevation, ft 725 Pump suction centerline elevation, ft 699.5 Piping losses (includes 0.05 due to sump screen), ft 14.01 Density of Water @l90* F, lb/ft 60.343 c

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ENCLOSURE 3 Time Sequence for Switchover To Recirculation (Sheet 1 of 2)

If Operator Action is Delayed Until Second Alann Time (3)(5) Time Elasped te Change In RWST RWST Volume (10)

Steo()) Rea.(Sec) (Sec) RWST{

(GPM) Volume (Gal) Remaining (Gal) 113,431(g)

- - 127.7 18,800 40,000 73,431 0 60(4) 187.7 9,800 9,800 63,631 4 37 224.7 9,800 6,043 57,588 5 30 254.7 9,800 4,900 52,688 6 30 284.7 9,800 a,900 47,788 7 25 309. 7 9,800 4,083 43,705 8 25 334.7 6,100 2,542 41,163 9 35 369.7 2,400 1,400 39,763 10 35 404.7 2,400 1,400 38,363 11 80 484.7 2,400 3,200 35,163 12 25 509.7 2,400 1,000 34,163 13 35 544.7 2,400 1,400 32,763 14 35 579.7 2,400 1,400 31,363 15 80 659.7 2,400 3,200 28,163 16 25 684.7 2,400 1,000 27,163 17 30 714.7 2,400 1 ,200 25,963 18 30 744.7 2,400 1,200 24,763 19 20 764.7 2,400 800 23,963 20 30 794.7 2,400 1,200 22,763 21 30 824.7 2,400 1,200 21.563 22 20 844.7 1,100 367 21,196 23 30 874.7 1,100 550 20,646(:7) 1,207.6 1,100 6,103 14,543 24 332.9(8) 30.0 1,237.6 1,100 550 13,993 25 60.0 1,297.6 0 0 13,993 26 60.0 1,357.6 0 0 13,993 22.6 min 1T98 298 9

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ENCLOSURE 3 (Sheet 2 of 2)

NOTES:

(II See Table 6.3.2-3 for description of steps.

(2) Flow rates are based on conservatively high runout flows with two train operation during the injection mode:

RHR Pump = 4500 GPM SI Pump = 650 GPM CC Pump = 550 GPM Spray Pump = 3700 GPM (3) Valve operating times are maximum operating times. Time required to start or stop a pump is 5 seconds.

(4)An allowance of time (60 seconds) for response to the Automatic Switchover is conservative due to continuous tank level indication and the fact that the operator must recognize that the RHR Pumps have already been switched over and realign power to 1FW21A.

(5)secon ired tooperator Time $qfor complete response the tlquired action inc udes a conservative 20 me for each manua procedure.

(6)The flowrate in this column is assumed to occur during the entire time interval for its respective step. This is conservative since a pump is stopping or a valve is closing, thus reducing the flowrate during the time interval .

(7)The Lo-Lo Level Alann is actuated at 14,543 gallons above the level where vortexing could occur. This ensures that suction would never be lost for any of the pumps in the ESF Systems. .

(8)These values indicate that the operator still has a sufficient amount of time remaining with all but three (3) steps completed. The centrifugal charging pumps continue to take suction from the RWST until the Lo-Lo

. Level Alann is actuated.

The Automatic Switchover is actuated at 73,431 gallons useable RWST volume remaining. An alarm indicates that the remaining ECCS pumps must be switched over. .

( 0)These RWST water volumes are minimum useable values.

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