ML20003G862
| ML20003G862 | |
| Person / Time | |
|---|---|
| Issue date: | 04/08/1981 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Boehnert P Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1329, NUDOCS 8105040078 | |
| Download: ML20003G862 (2) | |
Text
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UNITED STATES y, gg
'o NUCLEAR REGULATORY COMMISSION F
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ADVISORY COMMITTEE ON REACTOR SAFEGUARDS o
WASHINGTON,0. C. 20666
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April 8, 1981 it piI m s
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Yl MRMORANDUM FOR: Paul Boehnert, Staff Engineer
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FROM:
I. Catton, Consultant
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SUBJECT:
DNBR AND LOFT The DNBR limit imposed on operating reactors determines to some extent the operating envelope of values of pressure, temperature, flow, and power.
This is done by carrying out a series of calculations for certain antici-Codes are used in obtaining the heat transfer correls-pated tran3fents.
This leads us to a tions used in codes to carryout the calculation;.
msber of questions needing discussion:
How well can one calculate the critical heat flux and heat 1.
flux in a plant during the prescribed transients?
2.
How well do we know the critical heat flux?
3.
How was the DNBR limit of 1.3 selected?
4.
What happens if the DNBR limit is violated?
There is discussion of allowing more burn-up of the fuel.
5.
How will this impact on the consequences of a violation of the DNBR limit?
Is there a better way of insuring that fuel dama,e won't occur?
6.
For example, why not use time at temperature?
7.
PBF and LOFT have violated the DNBR limit. What happened to the fuel?
Three years ago (approximately) Westinghouse argued successfully for aAs I recall, the reduction in the DNBR limit and now CE has done so.
I believe an ACRS limit seemed very conservative and somewhat restrictive.
review is overdue.
A number of questions need The LOFT test matrix seems to be weakly based.
Some of the questions to be addressed before a test should be considered.
that come to mind are:
i What phenomena will I be studying in a given test?
1.
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. Paul Boehnert 2.
Why do I need the data?
3.
How will the information be used?
a) Code assessment b) Licensing What is the cost of not having the data?
4.
What separate effects data has been brought to bear on 5.
a particula-test and where is our knowledge so weak that I need tr; run a large test?
- 6. What specifically is being confirmed?
If there 1s no need to further understand a particular phenomena, the test If a particular phenomena is of interest, one can should not be run.
assess whether or not the LOFT will be helpful.
The Some of the proposed experiments do not meet the above requirements.The power ris planned ATWS tests will yield 'little new information.is too low an Even if the LOFT safeties are calibrated, we will not neces-sarily be able to predict the behavior of commer:ial plant relief valve safety valves.
behavior under ATWS conditions.
The LOFT secondary side is not secondary side to ;fve meaningful results. Further, operational transients very representative of commercial plants. occur on full scale plants and LOFT is of very little use in studies of small breaks.
The test selection No new information was presented to the Subcommittee.
proces's ut.ed by the LOFT program seems to be one of choosing a test for its popular' appeal rather than its ability to gain understanding of a par-As a result, my views of the program are not changed.
ticular phenomena.
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