ML20133G671

Forwards Three Questions to Be Discussed During Telcon Re Info Submitted in

ML20133G671
Person / Time
Site:	Comanche Peak
Issue date:	11/15/1996
From:	Donohew J NRC
To:	Woodlan D TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
References
NUDOCS 9701160116
Download: ML20133G671 (2)

Text

.. - . _ _ _ - -. _ _ _ . .

~

C o mau.a c Pc 4( 5 0-44 C fo-44/ .

l 'l

.' November 15, 1996 NOTE TO: Don Woodlan r u E l re r<e ic_

l FROM: Jack Donohew N <c.

SUBJECT:

PHONE CONFERENCE CALL ON MONDAY CONCERNING INFORMATION SUBMITTED IN NOVEMBER 1, 1996, LETTER Attached are 3 questions to be discussed on Monday. There may be additional questions raised by the staff at the phone call.

This telecopy is 2 pages.

l l

i i

!60nnq l

f0 11l 9701160116 961115 i PDR ADOCK 05000445 P PDR

_ _ _ ~ .. __ _ . . - _ . _ . . _ .. . _. __ _ . . .

l f

Questions Related to Comanche Peak 1&2 LBLOCA Reanalyses l (From Attachment to Letter TXX-96501, Nov. 1, 1996) l

1. Clarify the assumptions used in calculating the reflood heat transfer coefficients in the four analyses, i.e., LB16J, LB16Z, LB23W, and LB23X.

2. The plots on pp. 4 and 16 show reflood rates at the time of PCT l consistent witi information >rovided previously by TU Electric (TUE),

l 1.e., approximately 1.74 incies per second (ips). However, the plots on pp.10 and 22 show reflood rates at the time of PCT that are j

considerably lower, due to the fact that they are further out in time on  :

the curve (approximately 1.5 ips and 1.6 1ps, respectively). The  ;

reflood rates in the revised analyses are well within the range of '

concern for the Siemens correlation (i.e., 1.0 to 1.77 ips), and are

! substantially below the 1.74 ips rate in the original analyses.

TUE's determination that the Comanche Peak analyses demonstrated compliance with 10 CFR 50.46 was based on the proximity of the reflood rate at time of PCT to the endpoint of the " range of concern." This appears to no longer be the case. TUE needs to address this issue. 1

3. The trend of heat transfer coefficient as a function of time in the TUE  !

analyses requires clarification, as well. The plots on pp. 9 and 21 show heat transfer coefficient (HTC) as a function of time (presumably at the point of PCT, though that is not explicitly stated). The trend in both plots is for the HTC to increase monotonically--in fact, almost linearly--as a function of time (starting from around 52 seconds).

However, the reflood rate during this time (between 52 secords and the time of PCT is decreasing montonically. If the HTC curve isg at best, a constant as a function of reflood rate (i.e., capped at 1.77 ips), and (realistically) follows the reflood rate trend (a lower reficod rate means a lower HTC), how can these curves be explained?

1