ML19220C056

Describes Containment Sys Branch Position Re Capability of Secondary Sys to Mitigate Consequences of Main Steam Line Break Accident

ML19220C056
Person / Time
Site:	Crane
Issue date:	02/04/1977
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Vassallo B Office of Nuclear Reactor Regulation
References
NUDOCS 7904280138
Download: ML19220C056 (3)

Text

-

A i

G

,;g ghfhc_(t'.

I 2

g DISTRIBUTION Q~:

, 77 6

DOCKET FILES N RR READING CSB READING PS PEADING R. TEDESCO Docket No. 50-320 MEMORANDIDI FOR:

D. 3. Vassallo, Assistant Director for Light Water Reactors, DPM FROM:

R. L. Tedesco, Assistant Director for Plant Systems, DSS SU3 JECT:

TRV.E MILE ISLAND UNIT NO. 2 (UtI2) ?tAIN STEX4 LINE BREAK ACCIDENT ANALYSIS The purpose of this memorandus is to inform you of the Containment Systems Branca position regarding the capability of the secondary system to siti-We have con-gate the consequences of a =ain steam line break accident.

cluded that, as a sinimuc, tne cesign of tne feedwater control and power supply systems should be upgraded to assure that a single active failure will not jeopardize the capability to terminate feecwater flow to the affected steam generator following a main steam line break accident.

Our evaluation only considered main stean line breaks inside containment.

The basis for our position is discussed below.

The secondary system inside contain=ent is designed to meet seismic Category I requirenents. Non-mecnanistic pipe failures aie postulated for the contairment analysis, which further assumes no coacurrent seismic event (per Technical Issue No.1).

As a result, the components relied on to mitigate the accident need not be safety gn de.

With regard to the feedwater syste:n, there need only be sufficient redundancy of components and quality of design in the control and power supply systems to assure tnat a single active failure can not prevent the termination of feedwater ficw to the affected stem generator.

We have reviewed the situation where a MSIV fails to close and allows both steam generators to blowdown to the containment. Our confinatory analysis shows that tne contain=ent design pressure will not ise exceeded; Therefore, however, the effects to the core have yet to be evaluated.

we have directed our concern to the design adequacy of the control and power supply systems to terninate feedwater flow.

Contact:

F. Eltawila 7 90428 0 De f Ext. 27M1 m

oresc e p SW48t Ass F M saru

• 2 u. s. sovs4maeant *=ustme orricas sera.sas. tee Forna E318 Ma*. 9 53) AICM 0240 86 195

..,,a tre

=

->/

D. J. Vassallo 2

We will require the applicant to analyze the consequences of a postule.:ed SSI.3 accident in conjunction with various single active failures in the

ain feedwater systca.

'de will also require the applicant to j t.s tify cne sanual termination of auxiliary feedwater flow to the affected steam g,ene rato r.

(jn : 2.

! 'i

11. t : L. Tele :co Robert L. Tedesco, Assistant Director for Plant Syste=s Division of Sysetts Safety

Enclosure:

Rcquest for Additional Information on Three Mile Island Unit No. 2 cc:

S. Hanauer R. Heineman W. Mcdonald R. Boyd S. Varga H. Silver D. Ross T. Novak G. Lainas J. Kudrick J. Shapaier J. Glynn F. Eltawila FILE: Three Mile Isir.nd Unit No. 2 e

r 86 196

>c =

• b ES__

PS 4B:PS phhSS evaa W pliawilaimL._xShapak_er

_Glainh RLT'edesco

.._2/f/77

_2f_)/77 2/ [ 77 2/ /77

.m fory AEC.)l3 (Rev. 7 5)) AECM 0240

• 2 v. s. eovammus=v see m e arrices este.saa.see

_