ML20154G634
| ML20154G634 | |
| Person / Time | |
|---|---|
| Issue date: | 12/15/1985 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Boehnert P Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1826, NUDOCS 8603100060 | |
| Download: ML20154G634 (2) | |
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..T O Paul Dochnort 15 D ccmbcr 1925 FROMt Ivan Catton rhDR D3D3E b SUDJECT: ECCS Subcommittee Meeting 22 November 1905
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H Street, Washington D.C.
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Five topics were covered at the subcommittee meeting. I will try to addrest them in the centext requested by the rubcommittee chairman. In general I find the research program difficult to assess. There seem to be programs covering the important aspects of thermal hydraulics. However, every time we look in d et'ai l at r. program we find inadequate documentatn, lack of interpretation, insufficient depth of understanding to make it worthwhile,'
and.in rome caucu wrono physico. I am lef t with the f eeling that all of the rezcarch staff are not candid with us. The brief exposure we have had to come of the programs does not cllow one to offer more than superficial advi Separate effectu utudies are the backbone of our ability to predict thermal hydraulic behavior of full size LWRs. The funding in this area is around one million dollars or on the order of 5% of the thermal hydraulic area budget. This it much too small a portion of a budget that in too small in itself. One can carily suggest several areas where codes are weak and in ne of seperete offect9 cupport:
a.
upper plenum do-entrainment b.
cor e voi d di stribut ion durina flooding or boildown c.
quench temperature and its relationship to precursor cooling d.
bull cendentation There are many more topice one could suggest, some probably more important than thoto menticoned. There are also many equipment related seperate effects studier that could be useful. For enemple, pump seal analysis dann by West >nchcuse is very crude and can only be used for =erceth order information. Here caperiment and modeling would be usef ul both for assessmer of existing pump se31u and decign of future pump seals. Topics dealing with inventory estimation seem to have been largly forgotten in spite of the importance attcched to them following the TMI-2 incident. Research into means by which one might diagnose the direction a plant is heading seems to have dicepueared from the receerch program.
The Technical Intcor ation Center concept now beino developed could lead to a properl y planned research program if well thought out.
The need to do comethina to maintain a " critical mazo" in certain of the areas important to safety iu2ves is clear.
We are already seeing some areas looning their best people.
This coal ic clearly one that could be beneficial to NRC abilities to assenu saf ety.
At present it appears as if only a Thermal Hydraulic TIC han been consi dered.
Michelson's comment about a need for an overall ogency approach to TICS should be pursued before a particular TIC i s launched into being.
For example, the proposed Thermal Hydraulic TIC appears as if it will include code development as well as experimental effprts. This may be too broad.
I have always felt that LANL had the code expertine whereas INCL had the caperimental capability.
The Thermal Hydr eulic TIC should have a clearly defined capability based on the kinds of safety questions that we have neon during the past few years In particular it should have the capability to do component-tenting (valves, pumpu, seals, anri other thermal hydraulic devices) as well as measure the various two phase flow and hent transfer parameters that are important to saf ety analysis.
The emphasis on an integral test facility is, in my view, not appropriate.
B603100060 051215 EE/JD CG";I::AL PDR ACRS PDR Cort m ed L CT-1926 7-
The conclucion reached by Deckner that the MIST downcomer in on2 dimenaioni is nel sururiring.
We have been tellina them that it uno for come time.
'lhe one dimensional c h ar ac t er-of the MIST downcomer suggests that one oughi to take a second loch at the test plan to see whether or not some of the testu could be replaced or eliminated.
The present plan is to leave it as it is because it would be troublesome to change.
I find such an answer weak in the face cf the budget reductions the Theraml Hydraulic area has undergone.
The calculations that lead to the conclusion that the MIST downcomer is one dimenaional raised another interesting question.
When finer moding was used the question of ill-posedness comes up whereas coarse moding looses needed detail.
We thould ask how this predictament is to be resolvt The code assescment pr ogram has provided us with a strange tail of errors, non physical results and general troubles.
As pointed out by Buxton at the WhSR meeting, discontinuities in the constituitive relations for friction factor give calculations a strange tilt.
The tricks used to get around the d2scontinuities lead to calculations based on physics that allous negative friction factors.
One of the RELAPS newsletters indicates thet the f ricti on f actor was changed by a f actor of ten to achieve results th+t compared well with wuperimental data.
The friction fcctor can be guesbcd to within a factor of ten.
Such adjustments are made and focqctten all too often.
This is a practice that must be discouraged.
Ihc ICAAP is Siciding good results.
A number of important wooknen,ca have been pointed out and some interesting interactions have been found.
Fcr enemple, the Delaian study of SGTR has shown that steam oenerator modeling is weak and that linear heat transfer degradat i on wi th level leedr to non-conservative estimates of over-cooling (P TG).
With the loss of skilled US codes users it seems conter-productive to tr ain Foreigners to use the codes the US has spent so much money oevelopino.
The effort to develep a Nuclear Plant Analv:er thould be strengthened.
The cost to NRR tor a plant analysis is simply much too high, I am not, however, in favor of meFino the advanced codes like TRAC or RELAPS over into plant onlyzers.
If one wants a particular tool one shoudn't try to jury rig it from enisting tools developed for another purpose.
A number of more appropriate approaches exist and should be pursued.
Water Hammer was bracfly discusred. It is my view that RES should have a program to utudy water hammer resulting f rom steem bubble collapse.
Water hammer induced by valve closure, rapid pump stert and similar events do not involve phase chance and are calculable with a number of different codes that have been well validated (this doesn't mean NRC is using good codes). Fhase change induced water hammer leads to a wide variety of problems. Flow of near saturation water through valves causes fatique problems while pump closure can result in major pump system failure.
A steam bubble resulting from a valve cloture lead to tense moments at TMI.
Prof Griffith has predicted that steam bubble water hammer may occur in the cold leg when safety injection is recovered following a partial core uncovery. Certain NRR consultants felt that steam bubble collopse induced water hammer could be a serious safety issue. We cannot predict the magnitude of the water hammer that might result from collapse of a steam bubble.
The planned Integral Facility described by the staff seems to be headed to another full height full pressure system not un11le SemiScale. I wrote a memo l ast month that gives my views of the RCS plans in some detail.
Nothing was presented at this meeting that would change my mind.