Reattore nucleare di IV generazione refrigerato con piombo brest 300: la simulazione neutronica tram

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Tratto dalla Rivista IoRoma o dal suo allegato Quaderno che è consultabile al sito: http://rivista.ording.roma.it

a cura di commissione visto da

REATTORE NUCLEARE DI IV GENERAZIONE REFRIGERATO CON PIOMBO BREST 300: LA SIMULAZIONE NEUTRONICA TRAMITE IL SOFTWARE MCNPX, I FLUSSI NEUTRONICI E LA RISPOSTA DI UNA TIPICA SONDA PER REATTORI VELOCI.

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Tabella 1 – Principali caratteristiche dell’impianto nucleare BREST 300 [1] Potenza termica 700 MW Potenza elettrica netta 300 MW Temperatura del refrigerante all’ingresso del core 693 K Temperatura del refrigerante all’uscita del core 813 K Pressione del refrigerante 17 bar Flusso del refrigerante attraverso il core 3.8 Caduta di pressione all’interno del circuito primario 2 bar Numero di generatori di vapore (GV) 8 Numero di pompe primarie (assiali) 4 Potenza del singolo generatore di vapore 87.5 MW Capacità di ciascun GV 185.7 t/h Fluido del circuito secondario Water - steam TIN/TOUT per i GV 613 K / 793 K PIN/POUT per i GV 255 bar / 245 bar Temperatura dell’acqua all’ingresso del GV 538 K

0 $) .0 /'+.0 (0 '1 )/(1 ,/( )'+0 +/+0*1 %1**Y) )0(+/-

Strutture implementate nel codice di trasporto della radiazione MCNPX 1. /++1(1.1 ) $* '') (1 +./(),) [ '+0+/ (1,1''0! .)/ ) *1 1(+0.1 *1 '+. ++ .1 .) /.+0+1 (1**0 0.+1 )($1.)/.1 %) $) .0 - Y)(+1./ .10++/.1 ,/( ) ' /) 1*1 1(+) %) ,/ D '+)D)*1 <fuel assemblies& ;& *) 1*1 1(+) %) ,/(+./**/& ) D*/,,") %) .)$*1++/.1 1 *1 '+. ++ .1 )

1%)0+0 1(+1 ' ''1 1(+) )* D0..1*& $)(/ 0* .) / 1''1* %) ,/(+1() 1(+/- * ')'+1 0 %0 ) *1 1(+0.1 [ /'+.0+/ )( $) .0 1 B * (/,,)/*/& ,/( (0 * ( "1 0 0++) 0 %) FF

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1. *0 /(0 )(+1. 1%)0 1 F-B

1. *0 /(0 )V 1'+1.(0& ,/ 1 /'+.0+/ )( $) .0 E> () & $) .0 ?& "0 ( .1+),/*/ %) W &

) .0

Sezione con vista completa dell’impianto nucleare BREST 300 [1]

'1++1 /') )/() '/(/ /,, 0+1 %0 + D) )%0 1 0'+1 %) ' /.+/- * .1+),/*/ "0 %) 1(')/() B9-?

W B9-?

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Tabella 7 Composizione isotopica del combustibile fresco

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) .0 S Sezione verticale della parte inferiore dell’impianto [1] ) .0 B Sezioni orizzontali dell’impianto, come in figura 2 [1]

) .0 E S Barrette di combustibile per le regioni 1,2 e 3 del nocciolo

) .0 ? Sezione di un elemento di combustibile (FA), misure in mm.

1. Z 0(+/ ,/(,1.(1 )* ')'+1 0 %) ,/(+./**/& 1'! '/ [ ,/ /'+/ %0 BF 1*1 1(+) .0 . 0+) )( Z 0++./ %)$$1.1(+) . ) & & # 1% 6 1 %) Z 1'+) < # 1 ; '/(/ ./ 1++0+) 1. 0 ).1 % .0(+1 1 1(+ 0*) ',1(0.) )(,)%1(+0*)- * ')! '+1 0 [ ./ 1++0+/ 1. .)' /(%1.1 0**1 )(! '1. )/() /')+) 1 %) .10++) )+3 0**Y0 )0 1(+/ %1*

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

1(+) %) ,/ D '+)D)*1& BF 1*1 1(+) %) ,/(+./**/ 1 B D*/,,") %) .)$*1++/.1 .0%)0*1- 0 $) .0 9

/'+.0 +0*1 ,/($) .0 )/(1 ,/( )* (/,,)/*/ %) )!

) .0 9 S Schematizzazione del core, degli elementi di controllo e del riflettore radiale

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'/ )( +.1 .1 )/() ,/*/.0+1 ) $)() %1**0 ') *0 )/(1 [ '+0+/ ) *1 1(+0+/ 0(,"1 )* .)$*1++/.1 0'')0*1- (+.0 D) '/(/ '+0+) ) *1 1(+0+) ,/ 1 D*/,,") ,/ /'+) %0 (0 '/* )/(1 %) )/ D/ 1 0,,)0)/ 1. +1(1. ,/(+/ %1**1 '+. ++ .1 *) )+./$1 ++) *) 1*1 1(+) %) ,/(+./**/ ) *1 1(+0+) '/(/ ,/'+)+ )+) %0 ( 0''1 D*0 )/ 0''/.D)+/.1 < ;K (/+/ ,"1 1''/ ')0 ,/ /'+/ %0 9 D0..1 0''/.D)+.),) )( B & / ( (0 %1* %)0 1+./ %) 9

- 1. 0*, () %1) ')'+1 ) %) ,/(+./**/ [ '+0+0 %),")0.0+0 0(,"1 *0 * ( "1 0 %) +0*) D0..1++1 & 0& 0% 1'1 )/& 1. )* ')'+1 0 (/( [ '+0+/ .)*0',)0+/ 0*, ( %0+/- 0 * ( "1 0 %1**1 D0..1++1 1. +0*1 ')'+1 0& Z )(%)& [ '+0+0 '+0D)*)! +0 )( 0,,/.%/ ,/( )* $0++/ ,"1 *Y)(+1./ (/,,)/*/ $/''1 1.$1++0 1(+1 ,.)+),/ Z 0(%/ )* ')'+1 0 '+1''/ $/''1 )(+1.0 1(+1 )('1.)+/- / (! Z 1 [ (/+0 *0 1/ 1+.)0 1(1.0*1 %1 *) 1*1 1(! +) %) ,/(+./**/ 1. / ( (/ %1) Z 0++./ ')'+1 ) - 0 $) .0 A /'+.0 *0 ,/($) .0 )/(1 0%/+! +0+0 1. *Y0''1 D*0 )/ 0''/.D)+/.1 )( B *) 0,,)0) ) )1 0+) 1. )* ./ 1++/ ( ,*10.1 '/! (/ %)$$1.1(+) %0 Z 1**) 0%/++0+) 1. )* 1''1* 1 )* down-comer- 0 ,/ /') )/(1 %1**Y0,,)0)/ 1. *1 '+. ++ .1 )(+1.(1 0* (/,,)/*/ < 0)(1 1 0.+) '+. ++ .0*);& (/( [ '+0+0 0(,/.0 %),")0.0+0- 1.! +0(+/& 0) $)() %1**0 ') *0 )/(1& [ '+0+/ '1*1 )/! (0+/ ( +) ),/ 0,,)0)/ )( .0%/ %) *0 /.0.1 )( Z 1'+/ +) / %) 0 D)1(+1- #) +.0++0 %1**Y0,,)0)/ P & / 1++/ %) /*+) '+ %) )(1.1(+) 0+1! .)0*) 1. +1,(/*/ )1 ( ,*10.) 0% 0*+1 +1 1.0+ .1 - 0 ' 0 ,/ /') )/(1 )'/+/ ),0 [ .) /.+0+0 )( +0D1**0 FTabella 10 - Composizione isotopica dell’acciaio HCM12A [3]

( 0,,/.%/ ,/( Z 0(+/ .) /.+0+/ (1**1 .1,1! %1(+) $) .1 1 B& *0 $) .0 /'+.0 *0 ,/($)! .0 )/(1 $)(0*1 %1* ')'+1 0 ( ,*10.1 %0 ) *1!

1(+0.1 0**Y)(+1.(/ %1* ,/%),1 %) +.0' /.+/ %1**0 .0%)0 )/(1 W- 1(+.1& *1 $) .1 1 '/(/ *1 '1 )/() /.) /(+0*1 1 1.+),0*1& /++1( +1 ,/( )0() 1%)0()& %) + ++/ )* ')'+1 0 (0 /*+0 ,"1 1''/ [ '+0+/ ) *1 1(+0+/ (1* ,/%),1 * ')'+1 0 /++1( +/ [ 1.$1++0 1(+1 ,.)+),/- (! $0++)& +.0 )+1 */ '+1''/ ,/%),1 W& ( ,0*! ,/*/ %) ,.)+),)+3 "0 %) /'+.0+/ ,/ 1 )* $0++/.1 %)

/*+) *),0 )/(1 1$$1++) / ')0 0.) 0 1$$X -FFFFFě•?F-FFF E< ;- Y1$$1++) 0 $.0 )/(1 %) (1 +./() .)+0.%0+) [ %),")0.0+0 0.) 0 1$$XF-FF ? - =(Y *+1.)/.1 0(0*)')& 1$$1++ 0+0 ' * ')'+1 0 ) *1 1(+0+/& ,/ ./ 0 +0*1 %0+/#1DD1(1 *1 )($/. 0 )/() .1*0+) 1 0* # FF (/( $/''1./ +/+0* 1(+1 1'0 .)1(+)& )* ')'+1 0 ( ! ,*10.1 ) *1 1(+0+/ ') 0 ),)(0 /*+/ 0 Z 1**/

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) .0 A Assemblaggio assorbitore (AA)

) .0 Schema delle strutture in-core ed ex-core da implementare

) .0

Sezione orizzontale del sistema implementato, da MCNPX

) .0 Sezione verticale del sistema implementato, da MCNPX

/.) )(0*1 1 ,/ (Z 1 T .0 .1'1(+0.1 ( 1'1 )/ 0 '1 '+0(+1 %) .10++/.1 ( ,*10.1 1*/,1 .1$.) 1.0+/ ,/( )/ D/ 1.$1++0 1(+1 ,.)+),/& %/+0+/ %) + ++) ) ' /) ')'+1 ) %) '), .1 0 1 ,/(! +./**/-

) .0 B – Spettro neutronico al centro del nocciolo

Spettri neutronici

) .0 E – Spettro neutronico in corrisponenza dell’elemento di combustibile piÚ periferico

) .0 ? – Spettro neutronico in corrispondenza della circonferenza mediana del down-comer

) .0 : – Errore relativo per le misure dello spettro neutronico al centro del reattore

=(0 /*+0 ) *1 1(+0+/ *Y)(+1./ ')'+1 0 0**Y)(+1.! (/ %1* ,/%),1& *) ' 1++.) 1(1. 1+),) %1) $* '') (1 +./(),) '/(/ '+0+) .),0 0+) )( +.1 (+) %) 1.') %1* .10++/.1 N 0* ,1(+./ %1* (/,,)/*/I N 0 1+3 0*+1 0 %1**Y1*1 1(+/ %) ,/ D '+)D)! *1 )V 1'+1.(/I N )( ,/..)' /(%1( 0 %1**0 ,).,/($1.1( 0 1! %)0(0 %1* down-comer 0 ') *0 )/(1 )( W [ D0'0+0 ' **/ '+ %)/ '+0+)'+),/ %) E )*)/() %) (1 +./() 1 *) ' 1++.) .0,,/*+) )( ,/..)' /(%1( 0 %1) .1,1%1(+) +.1 (+) '/(/ .) /.+0+) .)' 1++) 0 1(+1 )( $) .0 B& E 1 ? 1 $) .1 : 1 9 .) /.+0(/ *Y1../.1 .1*0+) / %1**1

)' .1 ' 1++.0*) .)' 1++) 0 1(+1 0* ,1(+./ %1* .10++/.1 1 (1* down-comer- ( 0,,/.%/ ,/( )*

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

1 ,/ /(1(+) %1* .1$.) 1.0(+1& EB 1& E? 1 1 E

. ,/ 1 ,/ /(1(+) %1**1 0)(1- 0 $) .0 A .) /.+0 *0 '1 )/(1 %Y .+/ %) ,0++ .0 .0%)0+) 0 %1* F: D (1**Y)(+1. 0**/ %) 1(1. )1 %) )(+1.1''1 E #) T 1%1.1 ,")0.0 1(+1 *0 ,/..)' /(%1( 0 +.0 ) ),,") %) .)'/(0( 0 Z ) .1'1(+) 1 *1 %1! .1'')/() ,/..)' /(%1(+) (1 *) ' 1++.) (1 +./(),) (,"1 (1* .0( 1 %) 1(1. )1 0* %) '/++/ %) E 1 & )(,.1 1(+0(%/ )* .0%/ %) )' 1 )/(1 (1* ,/%),1 /(+1 0.*/ 1 )* ( 1./ %) (1 +./() ) *1 1(!

> 6 6 6 > 6 >

+0+)& [ /'')D)*1 .) 1*0.1 (0 $/. 0 '1 "1++0+0 1. */ ' 1++./- 0*1 $/. 0& )( Z 1'+/ .0( 1 %) 1(1. )1& [ %0 ) *),0.1 0 )/. 1(+1 0 *) )'/! +/ ) ,"1 ,/ /( /(/ )* ,/ D '+)D)*1 1. */ ' 1++./ 0* ,1(+./ %1* (/,,)/*/ *Y1(1. )0 )V ./D0D)*1 %1) (1 +./() [ 0.) 0 XE 1 &

1(+.1 )* 0*/. 1%)/ [ X ?B 1 - / ' 1++./ (1**0 '1,/(%0 /') )/(1 [ *1 1. 1(+1 )V

/%1.0+/ %1* .) /& ,/( (0 1(1. )0 1%)0 0.) 0 X ? 1 /),"[ )* ./ 1++/ . ''/ .1 1%1 ,"1 *0 '+. !

1(+0 )/(1 (1 +./(),0 ')0 0**/ )0+0 (1* downcomer& ') [ .),0 0+/ */ ' 1++./ (1 +./(),/ ' **0 ,).,/($1.1( 0 1%)0(0 %1* down-comer- (1 ! +./() ',1(+) %0* (/,,)/*/ "0((/ ,/ 1 1(1. )0 )V ./D0D)*1 ( 0*/.1 )(/.1 .)' 1++/ 0 Z 1**) +) ),) %1**0 D0(%0 %) .)'/(0( 0 %) ,0++ .0& )(/*! +.1& 1'') )(,/(+.0(/ * ( / )* ,0

)(/ .)(,) 0*!

1(+1 )* .1$.) 1.0(+1- 1.+0(+/ )* ./,1''/ %) .0*! *1(+0 1(+/ %1) (1 +./() <slow-downing; ,/(+)! ( 0 $)(/ 0% 0'' 1.1 *0 ,*0''),0 %)'+.)D )/(1 0 ,0 0(0- Y1(1. )0 )V ./D0D)*1 %1) (1 +./! () ' **0 ,).,/($1.1( 0 1%)0(0 %1* down-comer [ 0.) 0 XF& B1 <%)1,) /*+1 Z 1**0 %) ( .10++/.1 0% 0,Z 0 *1 1.0;& 1(+.1 *Y1(1. )0

1%)0 [ X:FF1 -

) .0 9 – Errore relativo per le misure dello spettro neutronico nel down-comer

) .0 A – Sezione d’urto (n, ) per 207Pb [5]

Impiego di strumentazione neutronica: camera a fissione per alte temperature. / 1 )** '+.0+/ )( $) .0 & )* ./ 1++/ . ''/ .1! 1%1 *Y)('+0**0 )/(1 %1**0 '+. 1(+0 )/(1 1. )* ,/(+./**/ %1* .10++/.1 0**Y)(+1.(/ %1* down-comer- ++0 )0 (/( [ ' 1,)$),0+/ ,"1 +) / %) +1,! (/*/ )0 [ ) )1 0+0- 1.+0(+/& ') [ %1,)'/ %) 0* +0.1 *0 .)' /'+0 %) (0 +) ),0 ,0 1.0 0 $)'! ')/(1 1. 0*+1 +1 1.0+ .1& 0++ 0* 1(+1 +)*) 0! +0 1. )* /()+/.0 )/ %) .10++/.) 1*/,) .1$.) 1.0! +) ,/( '/%)/ <# ; /),"M *0 +1 1.0+ .0 1%)0 %1* .1$.) 1.0(+1 (1* down-comer [ 0.) 0 X?A & ') [ '1*1 )/! (0+0 ,/ 1 '/(%0 ( /%1**/ ./%/++/ %0**0 "/+/()' *0 = B - 0 +0D1*0 F /'+.0 *1 ' 1 .)(,) 0*) ,0.0++1.)'+),"1 1% [ ',"1 0+) 0! +0 )( $) .0 0 ,/ /') )/(1 )'/+/ ),0 %1**/ '+.0+/ '1(')D)! *1& %) %1(')+3 '1(')+) 1X9& C, [ .) /.+0+0 )( +0D1**0

0 .)' /'+0 %1**0 ,0 1.0 0 $)'')/(1 = )(! '1.)+0 )( ( $* ''/ +1. ),/& +) ),/ %) ( .10++/.1 0% 0,Z 0 *1 1.0& [ .) /.+0+0 )( +0D1**0 0 .)' /'+0 %1**0 '+1''0 ,0 1.0 0 $)'')/(1 = [ '+0+0 0* +0+0 Z 0(%/ )('1.)+0 )( ( $* ''/ (1 +./(),/ %) 0*1 )(+1(')+3& 0 ,/( ' 1++./ 1(1. 1+),/ ,/..)' /(%1(+1 0 Z 1**/ .)! 1*0+/ (1* down-comer %1* # FF * .0+1/ %) $)'')/(1 T 1''1.1 0* +0+/ ,/ 1 $ X (< ;5 E5 $< ;% , ! '! ;

Tabella 20 - Principali caratteristiche della camera a fissione Photonis CFUE32 [4] 1 1.0+ .0 %) 1'1.,) )/ 0+1.)0*1 %) .) 1'+) 1(+/ 0+1.)0*1 )'/*0(+1 1(')/(1 (/ )(0*1 #+.0+/ '1(')D)*1 0''0 %1**/ '+.0+/ '1(')D)*1 0' %) .)1 ) 1(+/ 6)0 1+./ ( "1 0 ( "1 0 '+.0+/ '1(')D)*1 1 / 1. ,/**1 )/(0.1 *0 ,0.),0 #1(')D)*)+3 0) .0 ) 0

0 0'') 0 1' /') )/(1 0) .0 ) 0

0

< ;

> 6 6 6 > 6 >

)(/ 0 ?FF 4 ,,)0)/ )(/'')%0D)*1 < /8F-FE@; > BFF = >9 0..),,")+/ )( E=7AF@ F- C, . /( 0 AFF 0 :

EF

E?

EF (' ! F F C 5"! FB C"

) .0 Detector, camera a fissione Photonis CFUE32 [4]

1

Tabella 22 - Composizione isotopica dello strato sensibile interno alla camera a fissione Photonis CFUE32 [4]

?

Composizione isotopica [%w/w]

234 U 0.059731

235 U 98.048936

236 U 0.039821

238 U 1.403686

16 O 0.447826

Tabella 23 - Risposta della camera a fissione Photonis CFUE32 per un flusso termico [4]

Thermal neutronic flux [ n] [n/(cm2s] 103ě•Ś108 107ě•Ś3¡1012 109ě•Ś1013

Pulse mode Campbelling mode Current mode

Signal

10-3 conteggi/(s¡n/(cm2s>) 4¡10-29A2/(Hz¡n/cm2) 10-16A/n(n¡cm-2s-1)

Tabella 24 - Segnale in uscita dalla camera a fissione Photonis CFUE32 per il flusso neutronico tipico del BREST 300 in corrispondenza del down-comer

Neutronic flux [ n] [n/(cm2s] 103ě•Ś108 107ě•Ś3¡1012 109ě•Ś1013

Pulse mode Campbelling mode Current mode

)( , ) E [ )* ( 1./ %) )'/+/ ) %) E= 1. , 0**Y)(+1.(/ %1**0 ,0 1.0 0 $)'')/(1 ( 0,,/.%/ ,/( *0 ,/ /') )/(1 %1* ,/ D '+)! D)*1 1 %1* *) 1**/ %) /+1( 0 +1. ),0 %1* (/,,)/*/ 0 )1(0 /+1( 0& )* $* ''/ (1 +./(),/ 1%)/ )(! ,/.1 [ '+) 0+/ 0.) 0 (X -?? 5 F (C<,

5';&

1(+.1 (1* down-comer 1''/ [ 0.) 0 (%/ (!,/! X 5 F (C<,

5'; 1. * .0+1/ %) $)'')/() )(%/++1 0**Y)(+1.(/ %1**0 = 1. 1 / %) ( $* ''/ (1 +./(),/ +1.!

),/ %) )(+1(')+3 5 F (C<,

5';& ,/( XF-F E1 & [ ,0*,/*0+/ +.0 )+1 *0 < ; 1% [ 0.) 0 PX - 9B5 FA'! / '+1''/ $* ''/ %) )(+1(')+3 5 F (C<,

5';&

0 ,/( %)'+.)D )/(1 1(1. 1+),0 ,/)(,)%1(+1 ,/( Z 1**0 %1**/ ' 1++./ (1* down-comer& [ ,0*! ,/*0+0 %)',.1+) 0(%/ )( 1(1. )0 *0 .1*0+) 0 %)! '+.)D )/(1- 1.+0(+/ *Y1Z 0 )/(1 < ; T %)! ',.1+) 0.') (1**0 $/. 0 (

$ X ) 5 E5 $) , ! '! ;

< ;

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)( , ) ( [ )* ( 1./ %) D0(%1 1(1. 1+),"1 ,/( , ) [ '+0+0 %)',.1+) 0+0 *0 %)'+.)D )/(1& [ )* $* ''/ 1%)/ 1. *0 D0(%0 ) 1 $)& [ *0 '1 )/(1 %Y .+/ %) $)'')/(1 1. E= )( ,/..)' /(%1( 0 %1**Y1(1. )0 1%)0 ) ,/ 1+1(+1 0**0 D0(%0 1(1. 1+),0 ) ( 0,,/.%/ ,/( *Y1Z 0 )/(1 < ;& ,/(')%1.0(%/ ' $$),)1(+) Z 0++./ D0(%1 %) 1(1. )0 1. %)',.1! +) 0.1 )* $* ''/ (1* down-comer& )* .0+1/ %) $)'!

Signal 3.62¡10-4 conteggi/(s¡n/(cm2s>) 1.45¡10-29A2/(Hz¡n/cm2) 3.62¡10-17A/n(n¡cm-2s-1) ')/() )(+1.(0 1(+1 0**0 = & Z 0(%/ )('1.)! +0 (1* down-comer %1* # FF& [ .) /.+0+/ )( +0D1**0 B /($./(+0(%/ ) .)' *+0+) .) /.+0+) )( +0D1**0 B ,/( Z 1**) .) /.+0+) (1**0 .1,1%1(+1 +0D1**0 & ') .)',/(+.0 ,"1 )* '1 (0*1 )( ',)+0 %0**0 ,0 1! .0 0 $)'')/(1 = & Z 0(%/ )('1.)+0 (1* down-comer %1* # FF& [ 0.) 0 ,).,0 ( +1. / %) Z 1**/ ./%/++/ %0 ( $* ''/ +1. ),/ %) 0.) )(+1(')+3-

Conclusioni =(0 ') *0 )/(1 /(+1 0.*/ )( W %1* .10++/.1 # FF %0 :FF U+" [ '+0+0 ) ! *1 1(+0+0& )(,* %1(%/ ')0 *1 '+. ++ .1 )(!,/.1 ,"1 Z 1**1 1R!,/.1- #) [ )( 1'+) 0+/ ' **0 Z 0! *)+3 %1 *) ' 1++.) 1(1. 1+),) %1) (1 +./() )( +.1 %)! 1.') (+) %1* .10++/.1 % 1 )(!,/.1 1 (/ 1R! ,/.1- 0 $/. 0 %1 *) ' 1++.) (1 +./(),) [ '+0+0 .)! 1*0+0 1 ' )1 0+0 )( D0'1 0 ,/(')%1.0 )/() ' **1 '1 )/() %Y .+/ %) ,0++ .0 %1) .)(,) 0*) )'/+/ ) ,/ /(1(+) )* .1$.) 1.0(+1& *) 0,,)0) 1 )* ,/ ! D '+)D)*1- (/*+.1& '/(/ '+0+1 ,/(%/++1 0* +0 )/! () ' **0 .)' /'+0 %) +) ),"1 ,0 1.1 0 $)'')/(1 1. 0*+1 +1 1.0+ .1 %Y1'1.,) )/- ( 0.+),/*0.1& [ '+0+0 0* +0+0 *0 .)' /'+0 %1**0 ,0 1.0 "/+/! ()' = & ,/ (1 1(+1 ) )1 0+0 (1) .10+! +/.) 1*/,) .1$.) 1.0+) ,/( '/%)/& Z 0(%/ ) /+1+)! ,0 1(+1 )('1.)+0 (1* down-comer %1* # FF#) [ 1. 1( +) 0* .)' *+0+/ ,"1 )* '1 (0*1 )( ',)!

> 6 6 6 > 6 >

2

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)/() ,/**1 )/(0+1 )(,/.0 )0(/ 0 $0.1 *+1.)/.) 0 ./$/(%) 1(+) ' **1 ,0 1.1 0 $)'')/(1 ) )1! 0+1 (1 *) # 1 0 ./ /..1 ) *)/.0 1(+) ,/! '+. ++) ) 1. .0 ) ( 1.1 (0 ,/..1(+1 )( ',)+0

0 )/.1 0(,"1 1. .10++/.) .1$.) 1.0+) ,/( )/ G/-

% % "$ %$

0+ .0** #0$1 10%! //*1% 0'+ 10,+/. $/. 0. 1!#,0*1 ,*10. / 1. 1(1.0* %)+/.' ./$- -H- %0 / & ./$- - - H.*/ & /',/ EE +"/.' - - H.*/ & - - )*)(& - #- # ).(/ & - -#)*0! / )+' & - #- ' (/ & - - 1/(/ & - - # ).! (/ & - - / 0+ )(& - "- 0(1 & #- - /')(& - - G.0 /G& 8- - 1* 0(+'1 0& - - "0,"0.1'/ & - - / + /(+.)G +/.' H- - /.)'/ & #- - *0 )(& - - 0 / & - - ) 0*/ & - - / 0(/ 0& - F- #1 1(/! 0& #- - 1%/./ 1 +./(! " '),0* ,"0.0,+1.)'+),' /$ $0'+ .10,+/. ,"0((1*& 0+1.!,//*1% # 0.)(/ #- -& ) */ - -& . / - -& ./ %/ - -& ,"1.1 ()( - #-& & /',/ ./,11%)( ' /$ +"1 +" (+1.(0+)/(0* /($1.1(,1 /( ( )./( 1(+0* F1 .0%0+)/( /$ 0+1.)0*' )( ,*10. / 1. # '+1 ? A0+1. 10,+/.' ? %)+1% G - - **1(& -C- )( & 0(% - 1*'/( # 6 "1 )(1.0*'& 1! +0*' 4 0+1.)0*' #/,)1+ 7& EE< /../')/( /$ 0(%)%0+1 0+1.)0*' $/. # 1.,.)+),0* A0+1.! //*1% 10,! +/.'- - - **1(& - "1(& - 0(& :- 1(& 0(% - #.)%"0.0( D() 1.')+ /$ A)',/(')(& D# & #") 1"0. D 0) C0 0( ,*10. ,*1 F1 1*/ 1(+ ('+)+ +1 G0.0 )& C0 0( = F0+0'"11+ /$ +"1 (1 +./( %1+1,+/. D & ./% ,1% G 5H H # / 0( < : D'1.B' 0( 0*& 1.')/( -;-E& .)* E & ! ! !EE= 9IIIIIIIIIIIIIIIIIIIIIIIIIII email: %)$$1.1( )0*1 0"//-)+

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