ML20136E395
| ML20136E395 | |
| Person / Time | |
|---|---|
| Issue date: | 08/19/1985 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Boehnert P Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1818, NUDOCS 8601060534 | |
| Download: ML20136E395 (5) | |
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~/. c ADVISORY COMMITTEE ON REACTOR SAFEGUARDS o, K '
f WASHINGTON, D. C. 20555 -
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August 19, 1985 y
MEM0kr.fiDUM FOR:
Paul Boehnert, Senior Staff Engineer FROM:
van Catton, ACRS Consultant
SUBJECT:
20/3D MEETING REPORT, JUNE 18-21, 1985, MANNHEIM, FRG Dr. Schoch, from GKM, welcomed the participants to the meeting by noting that the 20/30 project was one of a kind. The project has been underway for six years.
It is the largest scale facility of its kind.
For an experimental facility, it is truly massive. Researchers and regulators from three countries, a utility and a reactor vendor are all participat-ing in the project.
It is an interesting combination but leads to a rather slow pace as each element must be agreed to by all parties.
Agreeing to what was said during the meeting for the official minutes took an entire morning.
In the paragraphs'that follow I will summarize my views of what took place and will send you a copy of the official minutes by mail.
I shipped the meeting handouts by surface mail and don't expect them for another month or so.
The first eight tests to be conducted were agreed upon at a meeting in February of this year. The expected behavior of the system combined with calculations using the advanced codes (primarily TRAC) are used to l
select a set of it tial conditions for the experiments. The boundary conditions, in par;icular the simulated core, are controlled to achieve the desired simulation.
A recent modification to the facility has caused further delay and is of some interest in its own right. Calculations using TRAC showed large thermal hydraulic oscillations in the intact loop. Through some inter-action that I failed to follow, this presented a set of circumstances where water hammer could occur., The resulting pressure spikes were predicted to be in excess of what the instrumentation could survive. As a result, the Germans were faced with the possibility of having to replace the instrumentation supplied by the U.S.
To be safe, they chose to incorporate an expensive modification into the facility. The oscil-l lations are condensation induced and the code's ability to predict l
condensation phenomena is weak.
It was with a lot of soul searching that the decision to spend was taken.
I would not have spent the money-based on the code predictions alone. The efforts taken to avoid water hammer are 8601060534 PDR ACRS gwg CT-1818 PDR Certified By c mm x
Catton - 2D/3D 6/18-21/85 Mtg August 19, 1985 staggering.
The water hamer avoidance procedures are so complex they will be a study in themselves.
The core is simulated with 17 pipes that allow varying amounts of steam and water to be injected below the tie plate. The two-phase mixture and its spetial distribution beneath the tie plate are supposed to represent what is expected from an actual core during various loss of coolant accidents, in particular the reflood phase. The two-phase. mixture is selected to natch what is somehow interpreted from CCTF experimental cata. The efforts underway to establish what the flow rates and steam water fractions are probably far exceeds the value of the result. This conclusion is based on my understanding of the geometry below the tie plant and the capability one has to truly simulate the phenomena-even if you knew what it was.
The inicial stages of commissioning of the facility are underway.
Leak testing has been completed. Cold commissioning has been started. An interesting discussion about who was to blame for certain delays took place with the Germans arguing that U.S. interests were the cause while the U.S. argued the converse and the Japanese watched. The step by step procedure that will be followed looks more complicated than a reactor startup plan. Actually sore of the thermal hydraulic systems are more complicated than those found in a nuclear power plant.
GKM furnished the site, utilities, the steam (300 tons /hr), condensate (200 tons /hr), and cooling water (1,100 tons /hr). The facility is
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actually tied into the turbine hall of the GKM electricity generating plant. The cooperation between the utility, indtistry and the government is unique. Such cooperation has not, to my knowledge, occurred in the U.S. for many years.
The Japanese summarized the status of their contribution to the 2D/3D program. They noted that CCTF finished ahead of schedule, analysis is now under way, and SCTF is on schedule. A vigorous discussion about differences that might exist between gravity reflood (the type expected during a LBLOCA) and forced reflood (the type on which present corre-lations are based) took place. The question to be answered is how much effect does the oscillatory behavior have on the reflood heat transfer coefficient.
It was the conviction of some that local fluid conditions determine the heat transfer coefficient and the oscillatory behavior changes the local fluid conditions. The other view was that more detailed experimental and analytical work is needed.
I agree with the former. Similar discussion about the importance of incore cross flow took place. Here future tests are planned so that quantitative analysis i
l can be made.
CCTF combined injection tests (hot and cold leg) yielded very interest-ing results. A distinctly nonuniform flow behavior was observed with large amounts of water flowing through the tie plate in one zone and
Catton - 2D/3D 6/18-21/85 Mtg August 19, 1985 steam and water up through another. The. water from the' upper injection flows down through the colder regions of the core while the hotter regions are cooled by flooding from below. An important consideration here is the locally one dimensional character of the core cooling process.
It appears as if one could easily do the type of calculation i
required of Westinghouse for their two loop plants if one knew how much more cross-sectional area wculd be in downflow. There should be enough data available soon from CCTF, and eventually from UPTF, to form the basis of a model.
Preliminary estimates should be possible based on the existieg CCTF data.
SCTF is undergoing modification. Basically, the modification involves installing better instrumentation (supplied by the U.S.?).
The focus of future testing will be upper plenum ECC of the type used in KWU plants.
The results will have some usefulness in fine tuning our understanding the Westingbcuse 2-Loop plants. There are thirteen scheduled tests covering a wide variety of different phenomena including vent valves.
Some recent CCTF tests were conducted that simulated past FLECHT tests.
Af ter ser.e tinkering with CCTF test conditions to make them similar to FLECHT, the results were found to be indistinguishable. This says even the local thermodynamics are similar. The observed similarity is of importance when we try to extrapolate thermal hydraulic phenomena from small scale to full scale LWRs.
A large number of separate effects studies of instrumentation are underway. Some of them are the following:
- Karlstein Calibration of Turbine Flow Meters
- KWU. Development of a Tie Plant Mass Flow Algorithm
- Hannover University Test Turbine Flow Meter Testing
- Upper Plenum Flow Measurement Module Development at MIT
- USNRC Advanced Instrumentation Development Program These programs look as if they are almost completed.
In some respects they had better be if UPTF results are to be meaningful and obtained without further delay.
I An overview of the methods to be used by the Germans to compare expected UPTF measurements and TRAC calculations was given. The plan secmed to be a strange combination of multiple regression and interpolation.
It will be difficult to sort out the details. The measurement locations do j
not line up with TRAC notarization. This means that the measurements will somehow have to be averaged or interpolated. The interpolation
i Catton - 2D/3D 6/18-21/85 Mtg August 19, 1985 will require a great deal of thought if it is to be meaningful. How the code comparisons would be made was the most hotly argued subject of the meeting. Some argued that the codes should only be evaluated for their ability to predict parameters important to safety. This means that the parameters to be compared would have to be carefully selected and would most likely be integral as contrasted to local measurements. The other side of the argument was based on a perceived need to compare the code results with detailed local measurements. This view seems to be based on a misconception of what the codes are capable of doing.
I favor an approach that is based on some kind of volume or area average so that the comparisons may be of value under selected conditions. For example, one could generate a surface fit of vapor and liquid flow rates through the tie plate using spline fits or some other method. The surface fit data could then be averaged over portions of the tie plate that are similar to the TRAC noding. This would allow one to make use of data such as observed downflow area from the upper plenum injection' tests using SCTF.
Some of the new experiments are expected to overrange the instrumenta-tion. This new findings led to a great deal of bickering about who was at fault and who should remedy the problem.
In the case receiving the most attention, the Germans want the U.S. to redesign and calibrate the drag disks. The U.S. argues that the Germans wanting to operate at higher pressures lead to the overranging and, therefore, they should take care of it. All participants were instructed-to review their calculations, pending any changes.
A great deal of time was spent on discussions of'the first eight tests planned for UPTF. Some of the discussion about the tests seemed silly.
x The main concern should be that a series of large scale tests be run that will span a wide range of parameters involving all important phenomena and that they have a well defined set of initial and boundary 3
I conditions. There will be a lot of large scale non-equilibrium
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two-phase flow experiments in an apparatus that appears to look like a nuclear reactor primary system with certain aspects of the secondary side.
It will certainly yield data that heretofore has been unavail-able. How directly applicable it will be is questionable. The limited height of the simulated core will not allow the two-phase zone to adequately develop. How important this is I do not know.
A large number of calculations are being done with TRAC to try and home
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in on test conditions for the UPTF runs. These calculations are being done both by the U.S. and by the Germans. Actually for each of the experimental parts of 2D/3D there are calculations being done by Japan, USA and FRG.
I think this is way overdone. We cannot be sure that the plant calculations are correct so why work su hard to generate test conditions based on them. Calculations by GRS yielded results that are quite different from those generated by LANL. One wonders why this is the case and whose (if either) are correct.
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Catton - 2D/3D 6/18-21/85 Mtg August 19, 1985 The UPTF data will be the only data from a system that is nearly full scale. As weak as some aspects of its simulation of a full scale reactor are, it will yield data that are one of a kind. A number of questions about hot leg flow will be answered convincingly. Questions about ficw bypass during the early stages of a LBLOCA will finally be put to rest. Many questions about condensation that plague the analyst will be answered with experimental data. One can argue that emphasis on the LBLOCA should be reduced, and to a certain extent it has. This perception is not fully correct. Although the data could be made more useful, it has a great deal of value as presently planned.
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