ML20138C346
| ML20138C346 | |
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|---|---|
| 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
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19 12/96 f
. TECHNISCHE UNIVERSIT4T MONCHEN q
LEHRSTUHl. A FOR THERMODYNAMIK Prof. Dr.4ng. Dr.4ng. E.h. F. Mayinger f
Review on the report 00E/1D-10541 f
Lower Head Integrity under in-Vessel Steam Explosion Loads Not being an expert in structural mechanics, I shall concentrate my revi f
fluiddynamic part of the report, trying to give an overall assessment.
For my review, I also took into account the report DOE /ID-10503 " P f
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 with the phen l i l ads effects of steam explosions. They differ widely in their statement on expo f l depending on assumptions or predictions for premixing, heat transp ih and conversion of thermal energy into mechanical loads. Experiment dimensional to mul-various melts, representing a variety of boundary conditions (from one I
tidimensional) and a wide range of scale.
l fi d The report under discussion here does delibe f
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and on 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 intagrity of its pressure vessel against hypotheticalloads of steam exp g
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m Entering the jungle of phenomena and effects connected with and r bl lt with explosions with the aim to come to a quantitative and physically reaso 0
i t be ful-respect to the mechanical behaviour of a pressu This is
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f med world wide the case in spite of the fact, that numerous resear ll contribu-h tical and in an ex-tions, an. lysing steam explosion phenomena and R$
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i l d in a demonstrate the safety margins of a pressure vessel against steam explos o ly conservative way, which is resistant against critical questions, it is quite obvious to app assumptions.
id h
The design of the AP600 " invites" such conservative assumptions, beca h thick low power density, the core is not only surrounded by a pressure vessel w AP600 design can wall, but also by a stainless steel reflector inside th h
to be 600, to other pres-very careful with any attempts to transfer the data, obtained for the AP h
and fluid-surised water reactors. Conservatisms, assumed l
t to pres-f hypothetical sure vessel failures, which are far beyond the physical reality under such E/ID-10541, there accident. Therefore, inspite of the fine work presen d realistic pre-ill remain many dictions. However, we must also be aware of the fact, that there always w i
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 transition to a molten pool, the availability or non-avail d all processes, olabliities and the preceding or being involved in melt relocation, including blockage co The conclusions, resistance of the reflector and the core barrel aga The two main 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 4-25) and give the goo l
lenum, forming maximum amount of melt, which can interact with the water in the ower p h
eel 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 frame.
i ery important energy scenario, by carefully studying melt relocation characteristics f
t in steam explosion f
and very commendable contribution of this report to the state o ar analysis.
d no further A further, very important result in this chapter la, that "re flood scena i ) This conclusion consideration from a steam explosion standpoint t activities h ld be urider-for existing pressurised water reactors, also, it means, that any effort s taken to add water again into the pressure vessci afte ident.
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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 kg/s. Based on this information, they determined the range of prem and steam and their distribution on the way to 7
i i d particle studied seriously in experiments (the MAGICO 2000), involving well-charact clouds mixing with water /1/. In these experiments, they performed de d in sub-on external and internal characteristics of the mixing zones. Mixing in s h
cooled water was studied. The results of these measu l
d PM ALPHA code, which they at first used for interpreting the experim l
which is the basis for the analysis of quantifying premixtures during a i
f explosion scenario in an AP600. Intertsting ph ll (hot and local voiding in the mixing zone, as well as global voiding throug l
pours).
lt should be mentioned here, that the original 2D PM-ALPHA cod j
l dicted for the three-dimensional version - called PM-ALPHA.30 d
l l
horter than 1 to the lower plenum. The average mixture zone a formed during the takes a few tenth of a second until enough small molten particles are f_
mixing procesa.
f This gives hope, that a very first steam explo 1
ex-sion produces such a high voidage (steam) in the waterpool, that a ibility, because plosion can be avoided. it is obvious, that the authors do not study th it cannot be quantified, but it may be allo ih large dangerous steam explosions probably won't occur in ca l
J 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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12/12/ M TH'J 13: 56 FAI 1 630 252 673o
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husa 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. For descr For describing the teractions between melt and water, the authors followed two ways.
d the microinteraction and for simulating the propagation of steam explosions, h
d computer code ESPROSE.m. This code is based on a series of exp f ility /2/. Originally parallel way which were performed in the so called SIGMA 2000 ac i
that the rate of the formulations for the microinteraction were based on the assumpt on, i
rate.
coolant mixing between debris and water is proportional to the melt f 4
This is a reasonable assumption and by this it was possible to prod i
l ds, starting parisons from available experiments for a wide range of steam explo il from weak propagations to supercritical detonations. The first formu based on experimental results, obtained in t ii ti ii l detona-effect of " venting", due to wave reflection at a free liquid surface. Sup id lt only, pouring at 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 were assessed by using exp i
ts were carried out 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 course one can argue, that there are scaling h
600 reactor. Ac-steam explosion loads to be expected during a severs accident in an il with the cording to the reviewer's opinion, these scaling problems however a d in the chap-mixing of particle clouds, plunging into water, a problem which was d fh ter before and which was solved by the authors with the help o t e ALPHA.30.
i The SIGMA 2000 facility was experimentally very well equipp i
about the fragmenta-techniques, like radiography, gave very good quantitative informat on ed wit tion of the drop mass and its distribution. The fragmentation, measur f
ch types of was reproducible within less than 20% which is a very good accuracy d was sub-experiments. In addition the fragmented melt was co ery reliable jected to sieve analysis.
electron microscope photographs. Generally h
i ion of the reviewer.
ignals In the SIGMA-2000 facility, not only the fragmentation rate, but a d
s Due to of the steam explosions were recorded by using high speed pressu the small scale of the facility, these pressure signals may be conse AP600. In a large a large scale geometry, like the downcomer or the lower plenum of id d areas, damp-volume, in which fragmentation of a hot melt starts, there are always v ing pressure propagation.
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 well documente l i n progress, like 10503. This report documents how ths various effects in steam exp os o d The report wave dynamics, explosion coupling and integral behaviour were assesse h
fluids demonstrates how the code is handling pressure waves in single i
y Special atten-and tnis not only in a one-dimensional, but in a twedimensional geom arison between pre-tion was given to reflection and transmission beh nt for li tions and the tem-a wide variety of thermo-and fluiddynamic parameters. The loca s tua dii paral behaviour are well predicted. So, the code ere done by The extrapolation from the small scale to the large geometry of the d
titutive fews for using the basic equations for wave dynamics in multiphase media h SIGMA facility, also.
mictointeractions. The latter ones were refined if edicting and simu;ating large scale conditions, also.
li bility of the Finally one has to ask the question on " substance scaling" i.e.
re mainly per-data, measured with modelling melts to liquid corium. The experi id is very likely to formed with tin and with aluminium oxide. Especiaily aluminium ox produce supercritical steam explosions when i definition and overall approach"):
l i
ith reactor "Also, it is important to note, that within the h
x 2
2 1995), nor is it known tensively voided premixtures (Huhtiniemi et al.,
be triggered to j
whether or under what condidons such premixtures can explode".
DOEllO 10541, on With respect to " substance scaling" the data, presented in the re id without any doubt, explosion loads, originating from steam explosions are on the s sure pulses than ex-because a corium molt / water interaction will produce much softe i
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 "to poten by 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_
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id t there After depressurising the primary system, followin i 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 of the lower core id to the lower good enough to prevent it from failing and core melt flows from the s bl plenum, steam explosions, originating from it, should not be a pro em.
i The second statement is as important as the first one, becau d core again after a 1
ing up to now, whether it would be advisable to try to flood a degra l
d in a former certain escalation of a severs accident. This p h
should be i
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 degre physics, it has been possible to bound uncertainties to a su i e side and the me to add, that these " wide margins" are still on the conservatvof a hypotheti-j 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 this fine work, i
point of view, but important problem and solving it to a great extend from an en h fluiddynamics to but based on controlling physics and on reliable constitutive laws l
l be expected in steam explosion scenarios.
^Y Prof. Dr.-Ing. Dr.-Ing.E.h. F. Mayinger f
f Munchen, November 20th,1996 S. Angelini, T.G. Theofanous and W.W. Yuen, The M 5
- 1995, 1
ing into Water, NUMETH 7, Saratoga Springs, NY, S 1
i NUREG/CP-0142 Vol. 3,1754-1778, J
X. Chen, W.W. Yuen and T.G. Theofanous, On the O
H7 Saratoga Microinteractions Concept in Steam Explosions, Proceedin 2
10-15,1995, NUREG/CP 0142 1
Springs, NY, September
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SORRELL TC002 10/a0/36 WED 14:51 FAI 1 830 252 4710 ANL-RE
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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
~
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 Best regards l
Brian Turland AEA Technology plc Phone +441305 203029 Fax +441305 202508 e-mail brian.turtand@aest.co.uk 1
l