ML19308B717

Comments on Vendor Ltr Re Small Break LOCA Analysis.Requests Addl Explanation Re Technical Basis for Acceptability of B&W Small Break LOCA Analysis as Conservative Prediction of Min Core Coverage for Small Breaks

ML19308B717
Person / Time
Site:	Crane, Bellefonte
Issue date:	02/08/1979
From:	Patterson D TENNESSEE VALLEY AUTHORITY
To:	Mcfarland J BABCOCK & WILCOX CO.
References
TASK-TF, TASK-TMR NUDOCS 8001160785
Download: ML19308B717 (2)

Text

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TENNESSEE 'v ALLEY Au's r.vna..

VILLC.TcNNC$5EE*37002 Mi W10C12G,.400 Commerce Avenue

.a MEB 79 0213 116

) February 8,1979 V

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t Babcock and Hilcox Post Office Box 1260 rg'-.

Lynchburg, Virginia 24505 L

Attention: Mr. James McFarland Gentlemen:

h BELLEFONTE HUCLEAR PLANT UNITS 1 AND 2 HUCLEAR STEAM SUPPLY SYSTEMS CONTRACT 71062-54114 2 LETTER NO. K-5478 SIMLL BREAK LOCA ANALYSIS - N4H-2-14(AR)_

We acknowledge receipt of your letter. No. D-3132 (NEB 790125 5 have the following comments.

TVA n111 require. the fo11oFring clarification and additional expla The to complete its review of.the sub.iect analysis and reference letter.

attachment to the reference letter contains the following statements:

"Af ter natural circulation ceases, the system pressure will be con-That is, the system pressure will j

1.

trolled by a ' volume balance.'

balance at a point where the volume of fluid discharged through j

the break equals the volume of steam being created in the core.i h inc

... the volume relief out the break increases w t 2.

"The volume of steam being generated in the core decreases with

. system pressure..... -

3.

increasing pressure."

5tatements'2 and 3 appear to belinconsistentJwit

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statement 1.

diction of minimum core coverage for 2

.'LOCA analysis as a conservagive preappears to require that statement three be j Please breaks smaller than 0.05 ftWe assume that statement 2 is incorrect.

j correct as written.

clarify.

belance"JasTwell as._* volume balance.", ~

ill break balance at a point where the volume of fluid discharged throu h heat content equais the volume of ste'am being. created in the core and t e "i

i reated of fluid discharged throughithe becak equals the dec

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) to be directly volumetric steam flow ratio (final value/ initial value V

in the core.

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' Babcock and Wilcox February 8,1979 proportional to the enthalpy and density 'ra'tfos (initial value/ final value).

E Since steam density increases mech faster than the enthalpy decreases over the range of interest, the net effect is a decrease in volumetric flow with JF.*

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increasing system pressure. This is in agreement with' statement 3.

However. :;. 1 the mass (volume X density) of fluid converted to steam is proportional to the enthalpy ratio only, which is increar.ing with increasing pressure.

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Therefore, the net effe~ct of increasing system pressure is to incr. ease the

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rate of loss of system inventory (mass).

It is this increasing inventory depletion coupled with a decreasing makeup rate from 'the HPI pump at elevated pressure that forms the basis for TVA's One way for B&W to alleviate this concern is to show that a concern.

"themal balance" does not have to pertain; otherwise, it would appear that the B&W small break LOCA analysis may not be an acceptable ounding predictor of minimum core level for breaks smaller than 0.05 ft Please reconfirm your position as stated in the reference letter and provide TVA with an appropriate explanation for not requiring a "themal balance."

Such a reply should resolve most of our remaining questions concerning very small break LOCA behavior.

Of course, concepts such as " volume balance" and " thermal balance" should be recognized as ov'ersimplifications which may apply only to a few special cases.

The rigorous solution must be based on mass and energy conservation principles applied to the entire system including all inputs, outputs, and phase changes within the system.

Please give us your written response by March 15, 1979.

Very truly yours, TENNESSEE VALLEY AUTHORITY Orisiosi SIE"*d DY

p. n. Pauens

' D. R. Patterson, Chief

' Mechanical Engineering Branch b

7 In triplicate cc: Mr. J. L. Atchison m

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