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%l;N-Mi February 26,1972 Dr. Louis M. Shotkin NL/N 353 US Nuclear Regulatory Comnussion Washington, D.C. 20555 Deat Dr. Shotkin.
I:s letter summartres my conclusions on the sultaodity cr' ROSA IV 'a provide adecuate data for the AP600 code validation.
De data generated by ROSA IV can be judged in accordance to :wo leveis of expectauons:
Tne drst is consistent with the objective of code validation and requires tnat one can state with con 5dence that a) sittular phenomena will observed in the AP600 and that b) the j various events occur in a sinular sequence. The INEL presentation on Friday, January 31.
1991 indicated that for the transients considered this is indeed the case.
He second level is more ambitious and requires that alcuantitative arreement between ROSA IV and the AP600 should be expected and b) that somehow ROSA IV would show predictive capabilities of AP600 transients.
Before drawing my conclusions. I would like to briedy outline tne vanous transients presented by INEL:
Pressure Balancing Line Break. I think that the major a typicality in tnis simulation is the single CMT. The actual break alfects only one venting line system. Therefore, one should see signi5 cant drainage in the intact CMT. This is not the case here since only one CMT ts present. De consequences of this system simpliEcation are: a) delayed CMT drainage:
b) reduced break flew: c) high primary inventory; and d) high pressurizer inventory. The over-estimation of the pnmary inventory is not conservative and 6e distortion in the inventory distribution is also cause of concern. The single cold leg in ROSA IV is a lesser distortion and mearungful data could be obtained without altering its geometry. However, one should consider the mtroducuon of two CMTs in ROSA IV. Further. the break on the PBL from the cold lcg to one of the two CMT could be simulated on an additional tie line from the steam generator to an available downcomer penetration.
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1 Steam Generator Tube Rupture (one and three tubes). His transient ts delayed at its i
mcspoon by steam generator a-typicalities. I am sure that they could be resolved in a satisfactory manner. The ROSA IV transient shows sigm6 cant sinulanties and excellent l
resulta could be achieved with some additional scaling effort.
l One Inch $5.LOCA. This transient demonstrated that the ventmg lines geometry is sigm6 cant and more effort should go in its scaling. The limited condensation events j
observed in ROSA IV is due to distortions in the steam / water interfacial heat transfer and the net effect is delayed CMT drainage. I think that sigmficant improvement could be within reach by altering the CMT and PBL arrangement.
Three Inches SB.LOCA. His is the most important :ransient presented and should be nudied in detail. The surge line/ hot ieg junction shows excessive voidage at about 1000 and
'700 mmutes mto the transient. He over scaled hot leg m ROSA IV has been identified a.s the culprit by INEL 1
The inadequacy of the ROSA IV hot leg geometry is fortunate in that it showed the sensitivity of the transient to the surge line junction conditions. This finding is significant because it implies that parametric studies should be considered in order to assess the
. sensitivity of plant behavior to the junction phase separation. The transient phenomenology must to be studied carefully. In a preliminary look at the transient. I can identified the followmg major ponions (i.e. modes): a) rapid depressurization; b) PBL/CMT circulation:
e) interruption of the PBL/CMT circulation and CMT drainage: d) ADS 1. accumulators
.njecnon and depressunzation: c) ADS-2 3-t and CMT dramage: and 0 RWST injection.
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The two anchor pomts for this transient seem to be the PBL/CMT ctreulation and the l
RWST injection. The system trajectories between these two points should be studied parametrically in order to identify the portion of the transient which could lead to bi furcations. In this respect. I think that ROSA IV could play an essential role since the surge line penetration in the hot leg could be modified with inserts on the surge line side to run a series of tests with different biases on the junction quulity.
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In summary, I think that in all these transienta. ROSA IV captures the major phenomena and follows sirmlar event sequences. Therefore, it can provide data for :he AP600 code validation. The level of complexity of the integral phenomena presented is suf5cient to challenge the integral response of the code. The differences associated with local distonions m the ROSA IV facility (with respect to an ideal AP600 scaled facility) seem to affect the quantitative aspect of the transient while still providing a qualitatively sinular spectrum of phenomena. This is : rue for most of the transient at least in their initial high pressure portion.
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3 On the 6econd higher level of expectations, the distonions m ROSA IV may lead to
- ualitauve (and therefore also quantitauve) diferent phenomenologies in the long term portion of the transient (times beyond the first 20 minutes) due to cumulative integral l
erfects. However, I thmk ROSA IV can perform parametne tesu to usess the sensitivities ofits a.:ypicalities and most important to enhance the understandlag of the AP600 behavior
- n a wider range of operstmg conditions. The idea of usiss RELAP to formulate the test matnx with sir 'ated compansons between the AP600 and various ROSA IV configurations
.s an excellent one. I was impressed by the INEL presentation and I recommend that more compansons be performed prior to finalize the ROSA IV modifications and test matrix.
On a more practical point of view. I am convinced that ROSA IV is the most cost effsetive way to obtain relevant information at high pressure and at a reasonably large scale. I am sure that m light of the overall time constramts, this is the most Of not tne cruy) reasonable
- cune of action, i
1 would stress the need fc parametrization to generate a range of initial conditions for the
- ow pressure facilities which will be designed to study iong term cooling. In my recent
- etters to you I have discussed my thoughts concerning the two facilities versus the " ideal" facility scheme and I have commented on the necessity to expano tne pressure range of the low pressure facilities to match the initial conditions with sufficient confidence.
i I hope these comments will be of some help and I will be glad to funner discuss any add!donal aspect of interest to you.
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Yours sincerely, j
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N Manno di Marzo ec. M. Ortiz, INEL l
l Manno el Maras O sees Bureene Rome O Betheses Aso 20s17 0 30140s.sas? O Fas:301-314 4477 i
l'ETER GRIFFITH Roorn 7 a4J
" '1msacntuetts Asenue t ',annrujee, SIA 0:IjY olis 253 ::4X 9 June 1992 l
l Dr. Marcos Ortiz l
Idaho National Engineering Laboratory l
EG&G Idaho. Inc, l
P.O. Box 1625 Idaho Falls. ID S3415
Dear Marcos:
This is a letter giving my reaction to the AP600 meeting on the ROSA IV experiments which was held in Idaho Falls June 3 and 4,1992. Also enclosed is l
an invoice for the time spent on this project. Let me start by making some l
general observations about the program, then proceed to discuss some of the specific questions raised and finally close with some conclusions.
This is a well structured program which clearly benefited from our experience with the LOCA work done on LWR's during the 70's and 80's.
Because the experimental program consists of three integral tests being run on l
three quite different rigs each scaled according to three different rationales, I j
can't imagine that there will be many questions outstanding about the system performance when these experiments are completed.
We have, in addition, got an operating, documented, computer code, RELAP-5, which can be used for the predication and analysis of the ROSA-IV j
experiments. The pieces of the program will come together in a timely way so that the results of this program can be used to design out any problems which might arise in the course of this research.
The other experiments are to be run in a timely manner too. The OSU and SPES experiments, which are small scale and doubtless easier to build and run, l
will be up and operating before ROSA IV is ready. The test matrix for ROSA-
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IV can he revised, a3 desirable, as a result of expenence on the smaller l
cxpenments. I think the whole program will hold together well.
l Let me now turn to the specific questions raised on the Rosa IV expenments. First I'll consider the pressunzer.
The long pressurizer is cenainly more like the prototype than the squatty one now installed. I don't think the difference is very profound, however, and I l
believe the codes are capable of predicting the differences in all imponant ways.
j If RELAP5 can't do it now it can be made to do so. The principal advantage in replacing the pressurizer is the long one will give an accident sequence which is j
closer to the prototype. What's that worth? I don't know, but I don't think it's l
worth a lot.
l The loop seal problem is greatly reduced with the new shallower loop l
seal, but not eliminated. There is a velocity through it which will allow it to fill.
l it water is present. and that will tend to divert flow. I suggest looking at the loop seal, seeing if it does ever have such a low velocity in it and see if it is possible l
that filling it with water will cause a significant change in vessel inventory. It l
might be fine as proposed but we'll have to look. In any case, I think it makes more sense to schedule a loop seal experiment on one of the small rigs than it i
does to spend $106 on a new ROSA-IV cold leg.
I think the simplified instrumentation is better than that proposed in the more complex original proposal. I'd like to see the check valves instrumented with the gate positioti measured however. I'm sure INEL can come up with a scheme that's simple to implement and will give this. A pan open gate valve is a fine flow meter - set reference (1) below. It measures flow up to around 10 ft/sec at which time it saturates but an orifice or turbine meter would then work very well. It also measures no flow which no other meter does. The enclosed xerox from reference (1) show how the check valve works. There's a whole theory for them available now too.
I think check valve position measurements fcr key check valves would tell us a lot about how the system is operating.
l There are always possible surprises awaiting the experimenter when a new.
ng is run. A system involving cold water and steam can experience a water hammer. I think water hammers are the most likely surprise we'll find. I think it 1 " Application Guidelines for Check Valves in Nuclear Power Plants," EPRI Report Number MP-5479.
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page 3 would be worthwhile to take the CREARE water hammer reports i2) below and use the items they identify as a list of possible water hammers. Construct a check list to see if the circumstances leading to water hammers might anse tiunng these transients.
Only one anses during drainage and that's mentioned in 0) below. It seems to have been designed out of the AP600 but until the computer nms for vanous transients are checked in detail we won't know for sure.
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l Any horizontal line that drains and is refilled with cold water is prone to j
water hammer. Does that ever happen in these ngs? If the SI line drains and is refilled a water hammer is possible. It's difficult to fill long horizontal 4
lines. The point the ECC enters the down commer is also a problem much as the feed rine was in the W steam generators a number of years ago. All it takes is a i
low velocity of cold water in the SI line. Bjorge (see reference 2) has a critenon for that.
1 I wonder too if a cold, stratified flow in the SI line might not cause it to bow and form a small loop seal in the far end. Both problems can easily be designed out if they are real.
I don't really grasp the implications of the non-prototypical IRWST tank they are proposing on ROSA IV. To the extent that the performance can be bounded by calculations (perfectly mixed and perfectly stratified) I don't see why the alternatives can't be explored on the computer. I shall withhold judgment on that issue.
Finally, I'd like to bring to your attention the experiments and analysis on heated TC's done by one of my students, Merschoff (4), several years ago.
Their behavior is not simple but it is predictable. It might make sense to look at this and see how the heated TC's will perform. A copy of this thesis is enclosed.
4 In conclusion, I think the AP600 is an uncommonly clean system. The ECC system looks robust and reasonably predictable. We have a variety of experiments to test its performance and see if there are any surprises. I believe if any are uncovered, they can be designed out a this stage. The separate effects.
2 Izenson, M.G., P.H. Rothe, G.B. Wallis," Diagnosis of Condensation-Induced Water Hammer," NUREG/CR-5220 vol.1 & 2, October 1988.
3 Griffith, P., Robert Silva " Steam Bubble Collapse Induced Water Hammer in Drainmg Pipes," presented at the PVP conference of ASME in New Orleans, June 1992.
4 Merschoff, E.W.," Design and Anal 's of a Core Water Level Detector for Pressurised Water Reactors "SM thesisin ME, June 1980.
l age l esperiments. the integral effect experiments and the analysis are all coming
- ogether in a timely manner so that we should have the answers when we need
- hem.1.'m pleased to see we've leamed from past expenence.
i Sincerely, i
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Peter Griffith Consultant i
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Dr. L. Shotkin Dr. B. Sheron t
Dr. G. Rhee U.S. Nuclear Regulatory Commission l
.\\1 ail Slot NL/N 353 l
7915 Eastem Avenue l
Washington DC 20555 l
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