ML19246A729
| ML19246A729 | |
| Person / Time | |
|---|---|
| Issue date: | 05/01/1979 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Bates A Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1113, NUDOCS 7907060288 | |
| Download: ML19246A729 (5) | |
Text
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NUCLE AR REG'JLATOPY COMMISSION y., j j g ORY COMMITTEE ON REACTOR PAFEGUARDS'tm
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WASmNGTON, D. C. 20555 g, ;.
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a tey 1, 1979
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Dr. Andrew Bates J
1 FROM:
Ivan Catton
SUBJECT:
MARK II OMERS GROUP MEETING, KiRCH 21-23, 1979, PALO ALTO, CALIFORNIA COPIES TO:
M. S. Plesset R. Savio Su : nary A new series of 4T tests will be run.
As usual the new tests have a narrow focus and in some respec cs seem to be poorly thought out.
Minimal additional instrumentation could atd a great deal. %e expariments will answer questions about the vent acoustics and air / steam ratios effects on pool botndary loads.
They do not, however, address vent lateral loariing.
The CREARE multivent study appears to be much improved.
We test matrix is satisfactory. Data interpretation, however, will be difficult. % e CREARE multiple vent load ruloction factor will probably be pre osed for use on some future plants. % is will have to be viewed with caur' The approach taken to obtain plant pool boundary loat...
%e 4T data will be used to characterize a chug source for ur
-D acoustic model of a plant pool. The plan is to use a worst case chu_
only remaining hurdle is to determine how close to simultaneous chugg ng is one in a 80 vent Mark II pool.
The Caorso SRV data demonstrates that the Mark II DFFR is almost-a factor of three too high in specifying SRV loads.
Apparently there is some lack of cooperation between various membsrs of the owners group. WPPS is the only plant still using the rams head SR/V. All others wil] use T-Ouenchers. Susquehana proceeded on its own oy having KhU carry out studies of both T-Quenchers and Vents.
Only recently have the members of the owners group bought into thenfd T-Quen'her wrk.
Susquehana is proceeding on its own with the Vent project with the help of both KhU and SRI.
As a result the K.U T-Quencher work was available to all Owncrs Group mcmbers (but not GE) and the KWU Vent work was not availc.ble '_o GE nor the owners group.
The KhD T-Quencher study conducted for PP&L and the Mark II owners group shows that the condensation oscillation pressures are negligable and that the air clearing loads are about one-half those specified in the DFFR which are based on use of a rams head SRV.
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The study of chuggiry being carried out for PP&L by KWU is very thorough.
When the results become available diey will set a standard for the industry.
Exteaded 4T Program The earlier 4T test were conducted with the simulated drywell some distance away. A number of questions were raisC about the effect of the vent leryth and how it couples the drywell to the pool (oscillations, etc.).
Fur ther, the NRC Staff did not feel that past test analysis and scaling arguments were suf ficiently convincing to make plant specific conductions.
A new series of experiments will be conducted with the drywell mounted on top of the 4T tank so that the vent length is the same as full size.
All aspects of a LOCA will be modeled including air /ateam mixtur es.
The major non-prototypic aspect is the symmetric arrangement of the 4T facility.
The primary purpose of the new program is tc measur e wall loads.
As a result only vent mass flow, with grab samples to assess air content, tank wall pressure and selected tenperatur es will be measured.
Ther e will be "no" str ain guages on the downcomers.
This seems, on the sur face, to be absurd.
One should attempt to obtain as much information as possible from every test. The possibility of chugging and large lateral loads on the vents is not fully resolved in my mind as the var ious statistical apptcaches are based on a limited amount of data.
The cost of a few strain guages is relatively small. Another similar question is about loads on obstacles beneath the vent. A rake of well placed hot wire anemometets would yield the information needed to validate, or invalidate, the ring vortex model being foster ed for use in such load calculations.
Air effects on the steam injection process are to be a part of this new study.
It is not clear how the test can be set up to properly simulate how the br eak flow will purge the drywell. GE has put the break at the top of the drywell to try and obtain the most rapid air purging.
The steam mixture entets the drywell via a tams head. Circulation patterns could be set up that vill delay air outflow.
It would be better if the rams head were replaced with a diffuser or if some baffles were used. Until a definitive study of how the air is purged from the drywell is car ried out, one must asstrne the worst canbinations of air and steam.
Some observations have shown that air content delays the bubble collapse ' ut doesn't always alter how it collapses.
It is therefore possible that cer uain canbinations of air and steam can put one in the regime of large lateral loads.
Multivent Chugging Experiments A multivent chuggirg experiment is being conducted by CRFARE at scales ranging from 1/10 to 5/12.
Up to seven vents will be used in their systan. The basic plan looks very good. Test data shown were fairly repeatable. Air content was maintained to below 15 ppn.
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A statistical analysis is planned where maximum and mean pressures are looked at.
I believe that the work w;11 miss the point unless the
~ atistics are viewed in light of the several different types of physical
'acesses occurring in the pool.
CREARE is attempting to develop a multirent multiplication factor.
They note that as pool size increases for t given number of vents the load de-creases. Thia is not surprising and has been observed by KWU as well as others. The reason is that each vent is a pressure or momentum source and the surface of a larger pool must feel a lower pressure than a sma'.1 pool if the pool boundary integrated value is to be the same.
The we.k is preliminary and, when viewed with the KWU proprietary data in mir 1, is headed in the right direction. The question will be how well the multiplication fac ct scales to full size complex geometries.
Improved Chugging P ol Boundary Load Definition Use of the 4T data to define loads for a plant requires several steps.
The 4T data contains in it the effect of boundary ring out as well as vent and pipe frequencies.
The approach taken is to ask what pressure source at the vent exist gives certain measured response at the pool boundary. This uncouples the vent chugging f rom the paol response and yields a vent source term that can be used elsewhere.
A series of 4T " chugs" have been examined and the 137 with the highest peak pressures used to characterize a chug. The chug was uncoupled from the 4T pool using a K-FIX model of the pool and a finite clement model of the pool baundaries. This characteristic chug source term will then be used with a 3-D acoustic mcdel to cbtain rigid wall loads for a Mark II contaimnent. A structural PSI model with plant unique characteristics will then yield plant unique pool boundary loads.
The statistics being generated by CREARE, with appropriate scaling factors, and chug timing (how are the vents behave relative to one another in time) will be needed to combine the characteristic chug into a multi-vent model.
The results of these experiences reduce the amount of work needed to confirm the SRV loads being used in the Susquehana design.
The Karlstein Test Facility is being modified to better simulate the Susquehana plant. A typical cell (geometric cross-sectional shape) associated with an SRV was constructed. The piping, valves, vacuum breakers, pipe supports, elbow, and the SR/V were simulated in full scale.
Some compromise will result due to the solid boundaries. The" are expected to be minimal and to fall within the experienced gained frua earlier KWU work. 1Se test facility is extremely well instrumented.
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The Karlstein Tests clearly demonstrate that quenc' ers eliminated SRV steam discharge oscillation problems by significantly descreasing the pressure oscillation magnitu:le.
SRI has looked at several aspects of the F30J work for Susquehana.
Their contribution appears to be minimal.
Caorso SRV Experinents The series of experiments conducted at Caorso show that the DFFR is conservative. An examination of maximum and minimum pressures measured at Caorso under a variety of conditions indicates that they are almost a factor of three under DFFR values.
A great deal of discussion lead to no conclusions a ; to why.
T-Ouencher Study The T-Ouencher study was originally initiated through a contract between PP&L (Susquehana) and KWU.
The study support has since been augmented by the Mark II owners group. Tne owners group has not decided, at this time, whether they will use the results of the stujy to ask for a reduc-tion in the DFFR loads.
The F0fJ group has been involved with SRV problems for quite some time and as a result made the decision to use quenchers over six years ago.
Tb demonstrate that quenchers w;uld solve problems such as those experiencea at Wiergassen, a program was conducted that included full scale tests as well as two in-plant tests during startup.
The results of their studies show that without a quencher, pool temperature must be limited to 45 C and with a quencher allowable pool pressure must be the limiting factor (their design pressure). The results of the study apply directly only to a single SRV of the Susquehana design.
Other owners will have to use analysis to account for plant differences if they choose to use the results of the study.
The approach used to account for multiple SRV's will be to determine what should be used.s a characteristic SRV source in a manner similar to that used to account for multiple vent chugging and with 3-D analysis determine the g>ol boundary loads.
KWU generated a great deal of evidence to confirm the approach during the licensing of the 8 B'#R's in Germany.
GKM Condqnsation Oscillation Test Program Work is being done by 10fJ under contract to PP&L. Neither GE nor the owners group is involved and as a result is not privy to the program's results. The experimental study will only address pool boundary loads 300 100
MARK II Mtg 3/21-23/79 May 1, 1979
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and will be unique to Susquehana. PPLL plans a May 1980 fuel loading date for Susquehana and to meet the time requirements GKM will have completed testing by January 1,1980. PP&L has SRI interfacing with KWU and there is somebody in residence in Mannheim.
The experimental facility will simulate a 30 sector in full scale.
The test facility is in many respects similar to the GE 4T test facility.
KWU went through the methodolog" needed to use the single vent data for plant calculations.
In principie, it is similar to that being done for the owners group by Bechtel.
To confirm their multi-vent approach, a series of 1/8 scale experiments were run. " hey compared results from 10 vents, six vents, two vents and one vent. All were run in a concrete box with same vent to pool area ratio. They found the chugging load of a vent decreases when the pool area is larger.
Further the maximum load was a factor of two higher than the average load and measurements all fell below calculations.
It was concluded by KWU that measurements in a single cell can reasonably be corrected for use in a plant by accounting for area change.
One can then reconstruct the total load by superposition.
This can only be done rigorously for uniformly placed ducts.
KNU will explore this by running several different tests.
There are still several concerns.
The control of the steam / air mixture in the drywell seems to be arbitrary and as a result effects of air on chugging will have to be viewed with caution.
Its not clear that the steam thermal content is high enough to drive the pool through the proper temeprature-time history.
Finally, the pool boundaries will change the pool stratification (this is probably minor).
The thoroughness of the KWU study is very encouraging.
Ib docunemtation is available at this time.
PP&L has not decided to what degree they will take credit for the results of the study.
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