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Transformation of aerosol under the WWER containment during the loca accident
J. Aerosol Sci., Vol. 22, Suppl. I, pp. $705-$708, 1991. Printed in Great Britain.
TRANSFORMATION CONTAINMENT A.G.Godizov
i
0021-8502/91 $3.00 + 0.00 Pergamon Preu plc
OF AEROSOL UNDER ]'HE W W E R DURING THE LOCA ACCIDENT
, A.D.Efano~
2
, V.~.Merkuiovicn
0
Yu. V. M u r a n o v ~ 7
1
A
S. S t e p a n o v " ,
i
,
?
YU. S. Y~.,.r'e v ~
I-
82,Lenin st. , O b n i n s k , K a l u g a reg. ,24902d~,'JSSR, SPA ' Typr, o o n " 12--. 1 , B o n d a r e n k o sq. ,Obninsk,Kaluga reg. ,249020,USSR, Institute of F'hysics and F'ower Engineering When substantiating the safety systems of an atomic power plant special attention is paid to the movement anO trans+ormarion of a e r o s o l s in r e a c t o r ouilOings at Z n e l o s s cf c:oo:ant accidents. This is connected b o t h wi'zh tlne d i r e c t contribution o~ r a d i o a c t i v e aerosols into the radiation situation at a n a t o m i c power plant under the emergency conditions ann with an indirect effect of a e r o s o l s on the thermodynamic and nyOrodynamic a n d Ineat a n O m a s s t r a n s f e r processes L'nOer tile reactor containment a s w e l l a s o n tlne l e v e l of t h e m i x t u r e mai.'ic~im pres:.,..'~'E ( S a m o i l o v et al., 1989). ]'he m a t h e m a t i c a l moOel of a e r o s o l transformation under Z-,e WWER containment is a s y s t e m of t . ~ e r m o d y n a m i c (~urar, o v et al., 1990) and microphysic (Godizov et ai, 1990) equations describing tne motion o~ t h e vapour-gas--0rc.,p].et, m i x t u r e in the containment, ~_ine e v o l u t i o n of E i n e r m o O y n a m i c paramecers an0 aerosols. The tnermo0ynamic and micropnysic parts :.-.,+t h e problem are connecteO witr, e a c h o t h e r througi", t:ne llqu:id wa-zer content ~ t n e amQutnt o4 w a t e r conoensec in e vc~:_,n,e urict.. ~ne variation o~: w n l c h gives sources (sinks.~ dE tr~e e n e r g y " c9 plnase t r a n s i t i o n s and vapour. T h e n : e n a v i o u r of t n e ! i q u = c water content i s in EL(on c l o s e l y connecteO witr. n e t e r o g e n e o L ~ s condensation of v a p o u r on aerosol (conoer-,saZion nuclei > . The geometric moeel of t h e c o n t a i n m e n t is a cylindric porous body containing a source of s u p e r l n e a t e d vapo,._,.r- a n d a e r o s o l ic, i t s bett.om. T h e d y n a m i c and thermodynamic c~naracteris~ics of n ~ e source a r e s e t in s p a c e and time. When superheated water vapour enters the containment lowing aerosol processes occur. The vapour adiabatic on with its cooling leads 'to t h e f o r m a t i o n 04 a z o n e the water vapour is c o n d e n s e d . T h e d r o p s p e c t r u m 7 in pie, can De calculated w i t h t h e ki. n e t i c equation.
the folexpansiwnere princip-
But for estimations one can use the parametrization oi= t h e drop spectrum in t h e f o r m o f , for example, gamma-distribution. In t h i s c a s e a s i g n i f i c a n t simplification o9 zr,e pro-D i e m is p o s s i b l e that is connected wit,h t h e d e t e r m i n a t i o n of tne phase relaxation t i m e of t h e w a t e r vapour excess ~hrough the spectrum moments, i.e. the drop concentration, liqulO water content, avoiding tin,~ k i n e t i c equation solution (Godizov et al, 1990). This allowed to close the thermodynamic equa-
$705
A. G. GODlZOV et al.
$706
zions Dy determining to condensation onto
the the
sources drops.
of
neat
and
vapour
sinks
due
Further conaensation g r o w t h of d r o p s a n d t h e i r s c a v e n g i n g with the drops falling from the ~ontainment top and the equipment, the typical s i z e s of w h i c h a r e g o v e r n e d with the surface tension coefficient, causes scanting of t h e c o n d e n sation nucleus spectrum. Wet scavenging of t h e l a r g e d r o p fraction of c o n B e n s a t i o n nuciei, retards heterogeneous condensation of w a t e r v a p o u r , that results in t h e g r o w t h of i t s partial pressure. It s h o u l d b e m e n t i o n e d that the secondary circuit water contains~ as a rule, boron additions going together with the vapour under the containment. The evaluations performed h a v e s h o w n t h a z un a t y p i c a l scenario of a s m a l l acsiaent the Brownian diffusion-induced coagulation of d o r i c acia particles they reach the sizes, when become condensation-active under supersaturations of t h e o r d e r of p e r c e n t v .cluri~g a b o u t i0 m i n u t e s . T h i s m e a n s tlnat t h e v o l u m e t r i c con~ensation critical state does not occur due to scavenging. The e s Z i m a t e s nave shown that Oecause of t h e c o n t i n u o u s u r s e o-i E o n d e n s a z i o n nuclei their concentration Oecomes tionary.
sosta-
The n u m e r i c a l stuaies performed of t h e b e h a v i o u r of t h e va-pour-alr-droplet meaium under the containment w i t h t h e equa-C l a n s of h y d r o d y n a m i c s ana microphysics m a d e it p o s s i b l e to oe~ermine the vapour density, pressure ana temperature of t h e mixzure, the temperature of t h e w a l l a n d e q u i p m e n t , aerosol anO drop concentration and sizes. In t h i s c a l c u l a t i o n the drop spectrum is m o d e l l e d as the monodisperse one. Typical calculation results a r e g i v e n in F i g . i in t h e P - T (F' is t h e p r e s s u r e , T is t h e t e m p e r a t u r e ) coordinates where the saturation curve ( P s " T s ) a n 0 t h e c u r v e of t h e fo'g f o r mation initiation at a r e l a t i v e humidity of 8 0 % a r e g i v e n . T i m e in s e c o n d s is in ~irc].es, in m i n u t e s - in s q u a r e s . The containment i n i t i a l s ~ a t e is d e t e r i o r a t e d witln a p o w e r f u l t h r u s t of v a p o u r f r o m t h e p r i m a r y circuit w i t h t h e r a t e of .4 kL, ~::g/s O u t i n g s e v e r a l seconds. During the first seconds fog is f o r m e d , i.e. t h e c o n d e n s a t i o n in b u l k t a k e s p l a c e . W h e n 2 ] s a r e o v e r at t n e m i x t u r e heating, evaporation of f o g O e g i n s ; in t o e t w e n t i e t h minu'Ce w h e n t h e t e m p e r a t u r e aecreases _
~o
.
('~
~,JC
the
condensation
in
zne
whole
T h e c o r : o e n s a t i o n on zlne c o n d e n s a t i o n walls retards pressure growth under zemperaZures Is
4"IL
of
1400C,
when
the
volume
begins
again.
nuclei and onto the the conzainment up t o
pressure
of
saturated
tr~e
vapour
Pa~
The total pressure reaches 3.8"105pa condensation on t h e w a l l s a n d on t h e inzenslvely the massive
in 2 0 s. T h e s u r f a c e equipment proceeds very
at an e n o r m o u s supersatuation equipment and containment are
of 1 0 5 p a a s heated very
far as slowly.
Transformation of aerosol under the WWER containment P
.5 ~4olt)
$707
Pa)
I /
I
/ /
I
I
60 Fig.
I
80 i.
I
I
~oo
I
~
I
,,
-r, '. F
The p_-r s c n e m e o.÷ ~_ne ~:i,zlng-zr-, f,r o cesses o+ the WWER-5,)c) cc, n E a l n m e r i t aE a maximum zeak:aoe m, vapour ~--~ .,].las~e~ ~Ja-i, °o,~ e q u i p m e n [ ~---F'=,L..2,F •
F'
(.7) ,
'"
Tog.
S
At all the stages of densation are parallel, account is necessary.
the
process therefore
volumetric and their correKt
contact concomparaole
An i m p o r t a n t peculiarity is that the neat sources comprzse the 0Mop concen'[ration and their size, there+ore joint ssuol-es of solid and liquid aerosols dynamics are nee0ed bct:i] from the theoretical and the experimental poinss o~ v i e w . it appeared that it is rather difficult to StUdy the condensation in oulk Wltlq t h e moOel o+ the con L :nmer? .... ¢~Llse t h e reouction in the containment size results In arti+iciai uuToerestlmation of the role o4 tne volumetric conOensatlon.
REFERENCES Samoilov O.B., Ustinov G.B., Ba~::nmet e v A.ff,. ~ i 9 ~ 9 . , . Safety of n u c l e a r power plants. M. , E n e r g o a t c , m i z o a r . . Muranov Yu.V. , Ye.~anov A.D. , Kashcheev V.M. , Nomo+il, ov E.V. , Yur'ev Yu.S. (1990). A mathematical model of neat and mass
$708
A . G . GODIZOV et al. sransfer in the ~WER containment. International '?~ERMOPHYSIC-90".Amstracts,Obnins~::,USSR, 25-28
Seminar on September,
J. "~9~_~.
Godlzov' A.G. , Merkul~vicn V.M. ~ Stepanov A.S. ~1990) . ConOen. satlon ano coagulation processes Within a EloseO volume in the presenEe ot a superneateo vapour sourEe, international ~.eminar on "TERMOPHYSIC-90".Abstracts,Obnins~::~USSR, 25-28 September,1990.
TRANSFORMATION CONTAINMENT A.G.Godizov
i
0021-8502/91 $3.00 + 0.00 Pergamon Preu plc
OF AEROSOL UNDER ]'HE W W E R DURING THE LOCA ACCIDENT
, A.D.Efano~
2
, V.~.Merkuiovicn
0
Yu. V. M u r a n o v ~ 7
1
A
S. S t e p a n o v " ,
i
,
?
YU. S. Y~.,.r'e v ~
I-
82,Lenin st. , O b n i n s k , K a l u g a reg. ,24902d~,'JSSR, SPA ' Typr, o o n " 12--. 1 , B o n d a r e n k o sq. ,Obninsk,Kaluga reg. ,249020,USSR, Institute of F'hysics and F'ower Engineering When substantiating the safety systems of an atomic power plant special attention is paid to the movement anO trans+ormarion of a e r o s o l s in r e a c t o r ouilOings at Z n e l o s s cf c:oo:ant accidents. This is connected b o t h wi'zh tlne d i r e c t contribution o~ r a d i o a c t i v e aerosols into the radiation situation at a n a t o m i c power plant under the emergency conditions ann with an indirect effect of a e r o s o l s on the thermodynamic and nyOrodynamic a n d Ineat a n O m a s s t r a n s f e r processes L'nOer tile reactor containment a s w e l l a s o n tlne l e v e l of t h e m i x t u r e mai.'ic~im pres:.,..'~'E ( S a m o i l o v et al., 1989). ]'he m a t h e m a t i c a l moOel of a e r o s o l transformation under Z-,e WWER containment is a s y s t e m of t . ~ e r m o d y n a m i c (~urar, o v et al., 1990) and microphysic (Godizov et ai, 1990) equations describing tne motion o~ t h e vapour-gas--0rc.,p].et, m i x t u r e in the containment, ~_ine e v o l u t i o n of E i n e r m o O y n a m i c paramecers an0 aerosols. The tnermo0ynamic and micropnysic parts :.-.,+t h e problem are connecteO witr, e a c h o t h e r througi", t:ne llqu:id wa-zer content ~ t n e amQutnt o4 w a t e r conoensec in e vc~:_,n,e urict.. ~ne variation o~: w n l c h gives sources (sinks.~ dE tr~e e n e r g y " c9 plnase t r a n s i t i o n s and vapour. T h e n : e n a v i o u r of t n e ! i q u = c water content i s in EL(on c l o s e l y connecteO witr. n e t e r o g e n e o L ~ s condensation of v a p o u r on aerosol (conoer-,saZion nuclei > . The geometric moeel of t h e c o n t a i n m e n t is a cylindric porous body containing a source of s u p e r l n e a t e d vapo,._,.r- a n d a e r o s o l ic, i t s bett.om. T h e d y n a m i c and thermodynamic c~naracteris~ics of n ~ e source a r e s e t in s p a c e and time. When superheated water vapour enters the containment lowing aerosol processes occur. The vapour adiabatic on with its cooling leads 'to t h e f o r m a t i o n 04 a z o n e the water vapour is c o n d e n s e d . T h e d r o p s p e c t r u m 7 in pie, can De calculated w i t h t h e ki. n e t i c equation.
the folexpansiwnere princip-
But for estimations one can use the parametrization oi= t h e drop spectrum in t h e f o r m o f , for example, gamma-distribution. In t h i s c a s e a s i g n i f i c a n t simplification o9 zr,e pro-D i e m is p o s s i b l e that is connected wit,h t h e d e t e r m i n a t i o n of tne phase relaxation t i m e of t h e w a t e r vapour excess ~hrough the spectrum moments, i.e. the drop concentration, liqulO water content, avoiding tin,~ k i n e t i c equation solution (Godizov et al, 1990). This allowed to close the thermodynamic equa-
$705
A. G. GODlZOV et al.
$706
zions Dy determining to condensation onto
the the
sources drops.
of
neat
and
vapour
sinks
due
Further conaensation g r o w t h of d r o p s a n d t h e i r s c a v e n g i n g with the drops falling from the ~ontainment top and the equipment, the typical s i z e s of w h i c h a r e g o v e r n e d with the surface tension coefficient, causes scanting of t h e c o n d e n sation nucleus spectrum. Wet scavenging of t h e l a r g e d r o p fraction of c o n B e n s a t i o n nuciei, retards heterogeneous condensation of w a t e r v a p o u r , that results in t h e g r o w t h of i t s partial pressure. It s h o u l d b e m e n t i o n e d that the secondary circuit water contains~ as a rule, boron additions going together with the vapour under the containment. The evaluations performed h a v e s h o w n t h a z un a t y p i c a l scenario of a s m a l l acsiaent the Brownian diffusion-induced coagulation of d o r i c acia particles they reach the sizes, when become condensation-active under supersaturations of t h e o r d e r of p e r c e n t v .cluri~g a b o u t i0 m i n u t e s . T h i s m e a n s tlnat t h e v o l u m e t r i c con~ensation critical state does not occur due to scavenging. The e s Z i m a t e s nave shown that Oecause of t h e c o n t i n u o u s u r s e o-i E o n d e n s a z i o n nuclei their concentration Oecomes tionary.
sosta-
The n u m e r i c a l stuaies performed of t h e b e h a v i o u r of t h e va-pour-alr-droplet meaium under the containment w i t h t h e equa-C l a n s of h y d r o d y n a m i c s ana microphysics m a d e it p o s s i b l e to oe~ermine the vapour density, pressure ana temperature of t h e mixzure, the temperature of t h e w a l l a n d e q u i p m e n t , aerosol anO drop concentration and sizes. In t h i s c a l c u l a t i o n the drop spectrum is m o d e l l e d as the monodisperse one. Typical calculation results a r e g i v e n in F i g . i in t h e P - T (F' is t h e p r e s s u r e , T is t h e t e m p e r a t u r e ) coordinates where the saturation curve ( P s " T s ) a n 0 t h e c u r v e of t h e fo'g f o r mation initiation at a r e l a t i v e humidity of 8 0 % a r e g i v e n . T i m e in s e c o n d s is in ~irc].es, in m i n u t e s - in s q u a r e s . The containment i n i t i a l s ~ a t e is d e t e r i o r a t e d witln a p o w e r f u l t h r u s t of v a p o u r f r o m t h e p r i m a r y circuit w i t h t h e r a t e of .4 kL, ~::g/s O u t i n g s e v e r a l seconds. During the first seconds fog is f o r m e d , i.e. t h e c o n d e n s a t i o n in b u l k t a k e s p l a c e . W h e n 2 ] s a r e o v e r at t n e m i x t u r e heating, evaporation of f o g O e g i n s ; in t o e t w e n t i e t h minu'Ce w h e n t h e t e m p e r a t u r e aecreases _
~o
.
('~
~,JC
the
condensation
in
zne
whole
T h e c o r : o e n s a t i o n on zlne c o n d e n s a t i o n walls retards pressure growth under zemperaZures Is
4"IL
of
1400C,
when
the
volume
begins
again.
nuclei and onto the the conzainment up t o
pressure
of
saturated
tr~e
vapour
Pa~
The total pressure reaches 3.8"105pa condensation on t h e w a l l s a n d on t h e inzenslvely the massive
in 2 0 s. T h e s u r f a c e equipment proceeds very
at an e n o r m o u s supersatuation equipment and containment are
of 1 0 5 p a a s heated very
far as slowly.
Transformation of aerosol under the WWER containment P
.5 ~4olt)
$707
Pa)
I /
I
/ /
I
I
60 Fig.
I
80 i.
I
I
~oo
I
~
I
,,
-r, '. F
The p_-r s c n e m e o.÷ ~_ne ~:i,zlng-zr-, f,r o cesses o+ the WWER-5,)c) cc, n E a l n m e r i t aE a maximum zeak:aoe m, vapour ~--~ .,].las~e~ ~Ja-i, °o,~ e q u i p m e n [ ~---F'=,L..2,F •
F'
(.7) ,
'"
Tog.
S
At all the stages of densation are parallel, account is necessary.
the
process therefore
volumetric and their correKt
contact concomparaole
An i m p o r t a n t peculiarity is that the neat sources comprzse the 0Mop concen'[ration and their size, there+ore joint ssuol-es of solid and liquid aerosols dynamics are nee0ed bct:i] from the theoretical and the experimental poinss o~ v i e w . it appeared that it is rather difficult to StUdy the condensation in oulk Wltlq t h e moOel o+ the con L :nmer? .... ¢~Llse t h e reouction in the containment size results In arti+iciai uuToerestlmation of the role o4 tne volumetric conOensatlon.
REFERENCES Samoilov O.B., Ustinov G.B., Ba~::nmet e v A.ff,. ~ i 9 ~ 9 . , . Safety of n u c l e a r power plants. M. , E n e r g o a t c , m i z o a r . . Muranov Yu.V. , Ye.~anov A.D. , Kashcheev V.M. , Nomo+il, ov E.V. , Yur'ev Yu.S. (1990). A mathematical model of neat and mass
$708
A . G . GODIZOV et al. sransfer in the ~WER containment. International '?~ERMOPHYSIC-90".Amstracts,Obnins~::,USSR, 25-28
Seminar on September,
J. "~9~_~.
Godlzov' A.G. , Merkul~vicn V.M. ~ Stepanov A.S. ~1990) . ConOen. satlon ano coagulation processes Within a EloseO volume in the presenEe ot a superneateo vapour sourEe, international ~.eminar on "TERMOPHYSIC-90".Abstracts,Obnins~::~USSR, 25-28 September,1990.