ML19312D394

Forwards Request for Further Info Needed for Review of Steam Generator Level Measurement Errors.Addl Info Already Provided in Was Insufficient.Requests Response by 800321

ML19312D394
Person / Time
Site:	McGuire, Mcguire
Issue date:	02/29/1980
From:	Baer R Office of Nuclear Reactor Regulation
To:	Parker W DUKE POWER CO.
References
NUDOCS 8003240321
Download: ML19312D394 (5)

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' UNITED STATES

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NUCLEAR REGULATORY COMMISSION

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FEB 291980

Docket Nos. 50-369 and 50-370 Mr. William 0. Parker, Jr.

Vice President, Steam Production Duke Power Company P. O. Box 2178

'422 South Church Street Charlotte, North Carolina 28242

SUBJECT:

STEAM GENERATOR LEVEL-MEASUREMENT ERRORS (McGuire Nuclear Station, Units 1 and 2)

We have evaluated the additional infomation provided in your letter of December 18, 1979 concerning steam generator level measurement errors and require some further infomation in order to complete our evaluation. This infomation is described in the Enclosure.

It is requested that this infomation be 'provided no later than March 21, 1980.

Sincerely, kb g

Robert L. Baer, Chief Light Water Reactors Branch No. 2 Division of Project Management

Enclosure:

' Request.For Additional Infomation ces w/ enclosure:

See next page 800ss40 3 z (

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L Mr. William O. _ Parker, Jr'.

Vice President, Steam Production Duke Power Company '

P. O. Box 2178 422 South Church Street

. Charlotte, North Carolina 28242

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cc: Mr. W.~L.' Porter Duke Power Company P.'O. Box 2178 1

422 South Church Street Charlotte, North Carolina 28242 J

Mr'. R. S. Mcward Power Systems Division Westinghouse Electric Corporation P. O. Bor 3C5 Pittsburgh, Pennsylvania 15230 Mr. E. J. Keith EDS Nuclear Incorporated

,l 220 Montgomery Street San Francisco, California 94104 i

~Mr. J, E. Houghtaling NUS Corporation 2536 Countryside Boulevard Clearwater, Florida 33515 Mr. Jesse L. Riley, President The Carelina Environmental Study Grcup l

854 Henley Place Charlotte, North Carolina 28207 J. Michael McGarry, III, Esq.

Debevoise & Liberman

.p.;

-1200 Seventeenth Street, N. W.

-Washington, D. C.

20036

' Robert M. Lazo, Esq., Chairman Atomic Safety and Licensing Board U. S. Nuclear Regulatory Comission Washington, D. C.

20555 Dr. Emmeth A. Luebke Atomic Safety and Licensing Board

. U. S. Nuclear Regulatory Comission Washington, D. C.- 20555 Dr. Cadet H. Hand, Jr., Director i

.I Bodega Marine ~ Lab of California P. O. Box 247:

~ Bodega Bay, California 94923l

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FEB 2 91980 1

. Mr.' Will iam.0. P.ar ker,~ J r..

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~cc:T David Flesichaker, Esq.

-1735 Eye Street, N. W.,-

Suite 709-Washington,-D. C. -20006 LRichard P. Wilson, Esq.

Assistant Attorney General State of South Carolina 2600 Bull Street Columbia, South Carolina 29201 w

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l '..Ycur response provided an. analysis to show how the steam generator icw-low

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-level trip setpoint is to be determined as a result of temperature induced

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errors resulting from accident environmental (heatup) effects on the reference leg.

You calculated a maximum error of "+ 12.2% of span" and

' propose to use this as the setpoint (upward from zero percent of span)~ for

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the Llow-low level trip point. We have the following concerns and request action be taken as described:

A.

The basic ~setpoint for the low-low level trip at "zero percent of span" corresponds to a water level exactly at the height even with 'the lower narrow range sensing tap. 'This setpoint does not provide an adequate margin to ensure that the instrument channel will initiate safety actions since the level transmitters do not respond to a reduction of water below-this point in the steam generator. Therefore, we require that a margin of safety of at least 3% be used in addition to the value of the accu-mulated errors to establish a minimum allowable setpoint.

B.

We question the basis for your use of an environmental allowance error which you state as being 7%. We assume that this error is an allowance for the -level transmitter. Based on our review of the Westinghouse tests of Barton Lot 1 transmitters, we conclude that the results do not demon-

. strate accuracies -less than the acceptance criteria which is- + 10%.

Therefore, this evaluation should be based upon + 10% errors or a basis

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should be provided for using a lower value.

2.

Your response indicates that reference legs will-be insulated to limit the error due to reference leg heatup. Provide the following additional informa-tion pertaining to the ~use of insulation:

A.

A. basis should be provided for the 2% error assumed due to insulation j

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addition. A description of how the 2% reference leg error is detennined i

should be provided.

B.

"rovide an analysis of the impact that the level measurement errors, due i

to reference leg heatup, will have on the post-accident monitoring (PAM) functions required of the steam generator narrow range and pressurizer level. instruments.

1 C.

The reference leg should not be insulated imediately adjacent to the condensing pot because the pot must be allowed to cool to perform its

' function, and the reference leg must be able to' cool to ambient before

. it enters the insulated portion.

Please describe how your design addresses these concerns.

.D..

Identify what precautions are to be taken to ensure that the operators

are aware of the possibility of erroneous indications that could result from flashing _of.the reference leg water to steam.

E.' Describe any long-tenn solutions that are being investigated that will provide reference leg ^ temperature compensation for the level transmitters.

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- 3.'.You state that the pressurizer icw level signal is.used for a control J.inction only and'that no credit is taken'for this' function in the accident analjses.

The FSAR states -that the pressurizer low level signal is used to:

1) Actuate an alarm when the -level falls-to a fixed setpoint, 2) Trip the pressurizer

. heaters ^"off" (to-protect'from overheat), and 3) Close the letdown line

isolation valves.

We areiconcerned that the impact'of level measurement errors due to. reference

-leg heatup in an accident environment would give' erroneous high. water level indication which could prevent the pressurizer low level control functions.

'Therefore :please revise your response to address the impact that the level measurement errors will have'on the pressurizer low level control functions and describe any corrective actions to be taken.

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