ML20138C346
| ML20138C346 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 11/20/1996 |
| From: | Mayinger F TECHNISCHE UNIVERSITAT MUNCHEN (TECHNICAL UNIVERSITY |
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| ML20138C152 | List: |
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| NUDOCS 9704300095 | |
| Download: ML20138C346 (7) | |
Text
19 12/96 Int a.;
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. TECHNISCHE UNIVERSIT4T MONCHEN q LEHRSTUHl. A FOR THERMODYNAMIK Prof. Dr.4ng. Dr.4ng. E.h. F. Mayinger Review f on the report 00E/1D-10541 Lower Head Integrity under in-Vessel Steam Explosion Loads f
Not being an expert in structural mechanics, I shall concentrate my f revi fluiddynamic part of the report, trying to give an overall assessment. !
For my review, I also took into account the report DOE /ID-10503 f "P Explosions: ESPROSE.m Verification Studies" Description of the Microinteractions Conceptin Steam Explosions /2/.
- 1. Pmblem d the Taare are many papers in the internationalliterature dealing l i with l ads the phen effects of steam explosions. They differ widely in their statement f l on expo depending on assumptions or predictions for premixing,ihheat transp and conversion of thermal energy into mechanical loads.
dimensional to mul-Experiment I
various melts, representing a variety of boundary conditions (from one tidimensional) and a wide range of scale.
l fi d f h The report under discussion here does h and on delibe more is based on carefully planed experiments, performed by some of th constitutive descriptions of pheriomens, involved in steam explosion proces h
Object of the study is the advanced pressurised water reactor g intagrity of its pressure vessel against hypotheticalloads of steam exp j g a.: m Entering the jungle of phenomena and effects connected bl lt withwith and re 0 explosions with the aim to come to a quantitative iand physically t be ful- reason
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This is
{< respect to the mechanical behaviour of a f med world widepressu ll contribu-R$
the case in spite of the fact, thath numerous tical and in an ex-resear d
tions, an. lysing steam explosion phenomena and
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12/12/96 TH1; 13 : 33 FAI 1 630 232 M oo i l d in a demonstrate the safety margins of a pressure vesselly againstconservative steam explos o way, which is resistant against critical questions, it is quite obvious to app assumptions.
id h The design of the AP600 " invites" such conservative hassumptions, thick beca low power density, the core is not only surrounded by a pressure vessel w AP600 design can h to be wall, but also by a stainless steel reflector inside th 600, to other pres-very careful with any attempts to transfer the data,h obtained and fluid- for the APl t to pres-surised water reactors. Conservatisms, hypothetical assumed f sure vessel failures, which are far beyond the physical E/ID-10541, reality there under such d realistic pre-accident. Therefore, inspite of the fine work presen ill remain many i
dictions. However, we must also be aware of the fact, that there always w intangibles within the scenarios of hypothetical severe accidents.
_2. Melf relocation characteristics d core, the Melt relocation characteristics are influenced by the heating up of the unco d all processes, transition to a molten pool, the availability or non-availa olabliities and the preceding or being involved in melt relocation, The conclusions, including blockage co The two main resistance of the reflector and the core barrel agai conclusions, namely that h ll and very the failure itself can be expected, that it will be local azimut a y near to the top of the oxidic pool and that ihi the coolability of the release will occur within a time-period, which is w t n the lower blockage, d feeling, that the are presented in chapter 4 of the report (see page l 4-25)lenum,and forming give the goo maximum amount of melt, which can interact withhtheeelwater in the ower p anical load a steam explosion, is limited and by this also the energy release and t e onto the pressure vessel wall would be within a reasonable i ery important frame.
f energy scenario, by carefully studying melt frelocation t in steam explosion characteristics and very commendable contribution of this report to the state o ar analysis. "
d no further A further, very important result in this chapter ila, ) This that "re flood scena conclusion t activities consideration from a steam explosion h ld bestandpoint urider-for existing pressurised water reactors, also, it means, that any effort s ident.
taken to add water again into the pressure vessci afte
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l 3 Quentification of crervixtures The authors of the report came to the result, that for the AP600 the amount ing into the lower plenum through the downcomer, would be in the 7 kg/s. Based on this information, they determined the range of prem i and steam and their distribution on the i d particle way to studied seriously in experiments (the MAGICO 2000), involving well-characte clouds mixing with water /1/. In these experiments, they performed d in sub- de on external and internal characteristics of the mixing zones. Mixing h in s l '
cooled water was studied. The results PM ALPHA code, which they at first used for interpreting lthe experim of these measu d
which is the basis for the analysis of quantifying premixtures during a
' i f
- explosion scenario in an AP600. Intertsting ll (hot ph l and local voiding in the mixing zone, as well as global voiding through
' pours). I j
lt should be mentioned here, that the original 2D l PM-ALPHA dicted for the cod d
l three-dimensional version - called PM-ALPHA.30 l horter than 1 to the lower plenum. The average mixture formed duringzone the a takes a few tenth of a second until enough small molten particles are mixing procesa.
f_ f This gives hope, that a very first steam explo 1
ex-sion produces such a high voidage (steam) in the waterpool, ibility, becausethat a plosion can be avoided. it is obvious, that the authors do not study th it cannot be quantified, but it may be allo ih J
l large dangerous steam explosions probably won't occur in ca water.
id e in the Another fact, which limits the momentum of l the migration of pressure pulses, because it offers a compressible vo um are physically well The mixing deliberations and calculations, presented in the report, based and deserve a high grade of credibility.
- 4. Quantification of exofonion fonds There are two key phenomena influencing loads of steam explosion. T a _ --
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.0L-RE ~5. husa 12/12/ M TH'J 13: 56 FAI 1 630 252 673o the mixing of particle clouds plunging into water and
- the microinteraction between water and melt.
i The first phenomenon was discussed in the chapter before.theFor descr For describing teractions between melt and water, the authors followed two ways. d the microinteraction and for simulating the propagation of steam h explosions, d
computer code ESPROSE.m. This code is based onOriginally f ility /2/. a series of exp '
parallel way which were performed in the so calledi SIGMAthat the 2000 rate of ac 4
the formulations for the microinteraction were based on the assumpt i rate.on, coolant mixing between debris and water is proportional to the melt f This is a reasonable assumption and by this it was i possible l ds, starting to prod parisons from available experiments for a wide range of steam il explo from weak propagations to supercritical detonations. The first formu based on experimental results, obtained ii l detona- in t ii ti effect of " venting", due to wave reflection at a id free liquid lt only, pouringsurface. at Sup tions were observed in the KROTOS facility with aluminium ox e me very high temperatures into water.
l lts, ob-In a next step, the constitutive equations werei assessed ts were carried by usingout exp tained in the above mentioned SIGMA 2000 facility. These exper men 0 C, im with molten tin drops, having temperatures up to 1800 l sions h
course one can argue, that there 600 are reactor. scalingAc-steam explosion loads to be expected during a seversil accident with the in an cording to the reviewer's opinion, these scaling problems d in the however chap- a mixing of particle clouds, plunging into water,fh a problem which was d ter before and which was solved by the authors with the help o t e .
ALPHA.30. i The SIGMA 2000 facility was experimentally i aboutvery well equippe the fragmenta-techniques, like radiography, gave very good quantitative informat on ed wit tion of the drop mass and its distribution. The fragmentation, f ch types of measur was reproducible within less than 20% which is a very good d was accuracy sub-experiments. In addition the fragmented melt was co ery reliable jected to sieve analysis.
i ion of the electron microscope photographs.h Generally reviewer. ignals In the SIGMA-2000 facility, not only the fragmentation d srate, Due tobut al of the steam explosions were recorded by using high speed pressu the small scale of the facility, these pressure signals may be AP600. conse In a large a large scale geometry, like the downcomer or the idlower d areas, plenum damp- of volume, in which fragmentation of a hot melt starts, there are always v ing pressure propagation.
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WW88 N 15:37 FA.I 1 630 252...4780 - - . . . - . .
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. DOE /lO. .
' The verification of the ESPROSE.m code is very l i n progress, well documente like
, 10503. This report documents how ths various effects in steam exp os o d The report i
wave dynamics, explosion coupling and integral behaviour h were fluids assesse
- demonstrates how the code is handling pressure waves y Special atten-in single and tnis not only in a one-dimensional, but in a twedimensional arison between pre- geom nt for tion was given to reflection and li transmission tions and the tem- beh a wide variety of thermo- and fluiddynamicdiiparameters. The loca s tua paral behaviour are well predicted. So, the code ere done by The extrapolation from the small scale to the dlargetitutive geometry fews for of the using the basic equations for wave dynamics in multiphase h SIGMA facility, also. media if edicting and mictointeractions. The latter ones were refined simu;ating large scale conditions, also.
li bility of the re mainly per-Finally one has to ask the question on " substance scaling" i.e.
data, measured with modelling melts to liquid corium.likely id is very Thetoexperi formed with tin and with aluminium oxide. Especiaily aluminium ox definition and overall produce supercritical steam explosions when i approach"): l i ith reactor h x "Also, it is important to note, 2 2 1995), that nor is it within known the j tensively voided premixtures (Huhtiniemi et al., be triggered to whether or under what condidons such premixtures can explode".
DOEllO 10541, on With respect to " substance scaling" the data,idpresented without any doubt, in the rel explosion loads, originating from steam explosions are onex-the s sure pulses than because a corium molt / water interaction will i produce much softe actions.
perianced in the experiments with aluminium oxide molt / water n
- 5. Inteoration and antanament ery important statements, in the chapter 7 " integration and assessment", there are two v namely that d a sig-from a more global perspective, the only way by "to poten nificant structural challenge on the lower head, would be having a highly subcooled pool in it" and J ii f "even a postulated rapid reflood scenario could no concern...".
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12/12/96 TEL '5:53 FAX 1 630 252,4, 30_
id t there After depressurising the primary system, ifollowin d sure vessel. This would be true not only for the AP600, but also for a water reactors. i
. So as long as one can guarantee, that the cooling id to ofthe thelower lower core good enough to prevent it from failing and core bl melt flows from the s plenum, steam explosions, originating from it, should not be a pro i em.
1 The second statement is as important as the d core first againone, after a becau ing up to now, whether it would be advisable to ltrydto in aflood formera degra h should be certain escalation of a severs accident. i This p
' given more effort to in-vessel cooling also after a partial core disint
.l 4
> s. Conclusions 541 report, to i fully agree with the conclusions presentad in chapter 9 of the the statement of the authors, that "because of the wide marg n ,fficient degree ;
physics, it has been possible to bound uncertainties to a su iofeaside and the me j to add, that these " wide margins" are still on the conservatv hypotheti-loads onto the pressure vessel and its lower plenum would be lowe cat severe accident, than predicted in the DOEllD-10541 report.
ki very difficult Finally I would like to congratulate the authors to i this point offineview,work, but important problem and solving it to a great extend fromto an enl h fluiddynamics l but based on controlling physics and on reliable constitutive laws l l be expected in steam explosion scenarios. ---
^Y f
Prof. Dr.-Ing. Dr.-Ing.E.h. F. Mayinger f i
Munchen, November 20th,1996 l
S. Angelini, T.G. Theofanous and W.W. Yuen, The M 1995, 1
5 l 1
ing into Water, NUMETH 7, Saratoga Springs, NY, S i NUREG/CP-0142 Vol. 3,1754-1778, J 2
X. Chen, W.W. Yuen and T.G. Theofanous, O H7 Saratoga
, On the !
Microinteractions Concept in Steam Explosions, Proceedinl 10-15,1995, NUREG/CP 0142 1 Springs, NY, September l
ANL-RE -c S. SORRELL TC002 10/a0/36 WED 14:51 FAI 1 830 252 4710
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. I M 5Nt3MhT241dN EN4 ll From: Snan Turtand Sent: Fnday. October 25,199611:05 AM To: Reactor Engineenng
Subject:
Re(2): Review of DOE /ID-10541 t-sa n coc Walt Deitnch Reactor Engineenng Argonne National Laboratory
Dear Walt,
I attach a Word 6 document containing my review of DOE /1010541. This does not contain any comments on the PM-ALPHA Venfication Studies. I am generally happy with the PM-ALPHA report. I will send some formal comments later, but I now have a period of leave, courses and foreign travel that takes me through until November 7.
I hope you And my comments on the main document and the supporting document on ESPROSE.m venfication studies useful. Please confirm that
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you are able to read the document successfully.
Thank you for asking me to do this work. If I can be of help in the future, please let me know. l l
Best regards l
Brian Turland AEA Technology plc Phone +441305 203029 Fax +441305 202508 e-mail brian.turtand@aest.co.uk l
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