ML19323H790
| ML19323H790 | |
| Person / Time | |
|---|---|
| Issue date: | 05/08/1980 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Duraiswamy S Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1245, NUDOCS 8006160189 | |
| Download: ML19323H790 (2) | |
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May 9, 1980 ME 141960 e
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S. Duraiswamy
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ECC6 and fiatural Circulation Subcommittee Meetings, 25-26 March 198 L
SUBJECT:
In that natural During the two day meeting a number of questions arose.
The comments circulation is a part of ECC, I didn't try to separate the two.
in the following paragraphs apply to both subcommittee meetings.
The Westinghouse small break analysis for UHI plants, WCAP-9369, and th
- i staff review of their analysis were quite informative.
Some questions the analysis methodology and the results appear quite reasonable.
and comments arising after review of WCAP 9369 that were not answered du the meeting as well as some arising during the meeting are as follows:
A large amount of cold water (UHI) entering the upper part of the core when it is partially voided will certainly lead to multi-dime 1.
The tools for motion.
that one-dimensional drif t-flux modeling still applies. Westingho could be used and the staff, through RSR, has access to this exist.
and TRAC.
not seem to be appropriate.
There are a number of ways to calculate the location of the froth levelThe W 2.
in the core during the period of core uncovery.
model overpredicts the level (non-conservative) whereas the Zuber-Findlay Both approaches have con-work underpredicts the level (conservative).It is not clear what is done stants that can be, and are, adjusted.
A request by Westinghouse nor is it clear how they justify what they do.
for the details, with emphasis on experimental justificat I
made.
as CE models as well as for the Westinghouse model.
If UHI actuation occurs during the single phase natural circulation phase of either an overcooling transient or a small break loss of coolant acciden 3.
(SBLOCA) the cold water injected from above may not only half the n During the per:od circulation, it may reverse the direction of the flow.
that the natural circulation is being re-established there will be a tem-The una perature overshoot because of the fluid inertia.
and b) what what is the peak average temperature in the coreIt is possible that b are a) overpressurization could lead to PORV or SRV actuations as a result of is the peak clad temperature.
the flow transient resulting from UHI.
The technical aspects of the feed and bleed approach to handling a SBLO If one has enough exit area for a given pump per-The EPRI seems to be well in hand.
formance the'n feed and bleed can be a method of accident mitigation.
It SRV study should answer questions about flow through a given exit area.
If one then wants to remains to see what a given plant pump performance is.
use feed-and-bleed to mitigate a SBLOCA then they must make the chang 8006160%
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It seems Whether or nor one wants to use feed and bleed is another question. Effort should to me that too much is being made of a relatively simple concept.
i be devoted to deciding if feed-and-bleed is desirable.
The question of non-condensible gas effect on the reflux mode of core The question of how well we need to know the heatR cooling needs attention.
transfer co6Tficient is still unanswered.
process and all that is needed is confirmation that the process is e TRAC is enough under all conditions. fled when all codes in use are based on lum presently too slow for SBLOCA analysis.
or some similar facility ought to be used soon for a series of scaping expe h
ments to determine how much non-condensible gas is necessary to degrade t e reflux boiling mode of cooling to the point it is not sufficient of how much non-condensible gas is available would dictate whether or not mo core coolability.
detailed studies are necessary.
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