ML20028A158
| ML20028A158 | |
| Person / Time | |
|---|---|
| Issue date: | 10/27/1982 |
| From: | Thomas C Office of Nuclear Reactor Regulation |
| To: | Sherwood G GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 8211160512 | |
| Download: ML20028A158 (5) | |
Text
e OCT 2 71982 General Electric Company ATTN: Dr. G. G. Sherwood, Manager Safety and Licensing 175 Curtner Avenue l
San Jose, California 95114
Dear Dr. Sherwood:
Subject:
Request Number 3 for Additional Information on NEDE-23785-1(P)
We are currently reviewing the General Electric Company licensing topical report NEDE-23785-1(P) entitled "The GESTRA-LOCA.and SAFER Models for th Evaluation of the Loss of Coolant Accident."
The continuing review of Volume II entitled "S FER-Long Term Inventory Model for BWR Loss-of-Coolant Analysis" reveals the need for additional information as identified in the enclosure.
This additional information is necessary to continue the review - its expeditious submittal will, therefore, be to General Electric's advantage. -We request your response no later than December 1,1982. Please advise us of your intended sub-mittal date, so that we may schedule the continuing review.
Sincerely.
Cecil 0. Thomas, Acting Chief Standardization & Special Projects Branch Division of Licensing
Enclosure:
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r ENCLOSURE 1.
Specify the differences in the heat transfer logic and correlations between the current Evaluation Model (EM) and SAFER.
Compare the conditions which the current E'M must see in order to assume a specific heat transfer (HT) regime with the conditions SAFER must see to assume the same regime.
Provide the basis, experimental'or other=
wiser for these changes in HT correlations and the HT Logic.
Specific references (pages and figure numbers) should be provided for experimental data references.
2.
Provide example calculations using both the current EM and SAFER for a large breaks intermediate breaks and small break which show as-a function of time:
a) the applicable heat transfer regimes (i.e.,
nucleate boilings transition boiling, etc.);
b) the heat transfer correlations used for each regime and the resulting numerical values of the heat trans-l l
fer coefficients; i
c) where there is a change in HT regime, why the change l
l occurse i.e.,
what does the code see that prompts a change in HT coefficient.
l l
3.
Relative to the current EM, explain the effect and the resson for the effects of each of the following changesi I
l.
F
. on the determination of applicable HT regimer CCFL break-downs and peak cladding temperature; quantify the effects where possible:
a)
Increased number of regions modeled b)
Core region subdivision c)
Internal flow splits based on pressure differences s
d)
GESTR-LOCA gap conductance model.
4.
What criteria will be used to determine when the drift flux model for vapor sweep flow will be used as opposed to the Wilson bubble rise model?
What is the difference in effect on heat and mass transfer?
5.
Under conditions of subcooled CCFL breakdown in the periph-eral bundles, how is the flow split modeled between those I
bundles which have " broken down" and those which have not broken down?
How do you know that the hot bundle is not i
1 starved when the upper plenum is drained through the periph-eral bundles?
Is this conditi'on considered in the d6ter-mination of HT regime in the central bundles or the hot bundle?
1 l
6.
How does SAFER determine that CCFL has set up at the various restrictions in the core?
What does the code see that i
i
F.
. indicates CCFL breakdown?
What is the basis for assum-9 ing these thresholds?
7.'
For CCFL conditions at other than the upper tie plater Y
.O what is the basis for the values of CD1/4?
Provide specific data or references to readily available data.
s 8.
The spray HT coefficient is proposed to be determined as a function of inlet steam flow rater pressure, and down-flow througr. the tr>er tie plate.
Downflow is to be cal-culated from the CCFL correlation.
Tests at the SSTF have indicated that multidimensional effects are important in CCFL conditionsi but that conclusions regarding the central bundles could not be reached because of the pie" slice shape of the facility.
How then can a credible calculation of spray HT coefficient be made based on CCFL for the hot bundler since it will be a central bundle?
Provide a comparison of calculated HT coefficients with I
data to substantiate your model.
l l
9.
Tests in the TLTA and SSTF have indicated that leakage from the bypass region, and CCFL at the side entry orifice, play important roles in refilling the fuel bundles.
Is CCFL considered to restrict the leakage flow into the bundles from the bypass region?
If so, to what extent?
If not, why not?
. 10.
The fuel rod stress and perforation models are said to be applied to only selected peak and average rods in SAFER, while the CHASTE code applies the model to all rods in a given-bundle.
How does SAFER then determine the total number of rode wh'ch have become perforated--a number re-quired as i n p u +..or calculation of the metal-water reaction s
rate?
11.
Describe the modeling of the occurrence of an early boiling ra.;ition for input to SAFER differs from the s
Does the current EM consider an early boiling curr t r a n.: ' '- 4.
a average power bundles?
If so, discuss the impact on FCT of deleting this consideration in SAFER and discuss the re.errn'ed (in your report) data which suppo'ts your proposal 12.
Identify those models in SAFER which you consider to con-l tain the largest uncertainties, and explain how these are conservatively bounded.
Compare the uncertainties in SAFER with those in the current EM.
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