Reaeaera es I ns : al I a ` " roirs I nspecto : . a : e , H l { S 0 , I 9 7 9 . 2

Reaeaera
es
.
rq:.,r
v
uv \r,..g4.
I n s : a l I a ' " r o i r sI n s p e c t o : . a : e ,H l { S 0 ,I 9 7 9 .
2
'rDesl8nsa:ety c.ite.ia
foa CEGB
nuclea-- poBe. stationsri, CECBHealth
a n d S a a e t yD e p a . t o e n t , H S / R 1 6 7 / 8(1R e v i s e d ) , 1 9 8 2 .
$rr
*.-
-,,,
-.:r'i..'
i-d-J.C-'*j1--!+,:!-
:4i
>nq !E;
'nr's'&1*ri.6lb$r€ft9i;di,titiie*stAi*&6'
DESCRIPTIoN0F T'JE 8Bl{K RIACToRS
SECTIoN2:
The Che.ncbyl platt
i:F
p.essute
has RBMKboiLiaS !.ate.,
The combinatrot of a p: essu:'e tube coclart
o o d e a a t e da e a c l c a s ,
a gaaphite nodeaato:- ln a coooercj.a.L nuclea:'po*er
u.ique to the Soviet ljnion.
.eacto.s
bullt
The chief
Ir
piessriJ'e tubes rllh
orload .efuellln8.
Vertical
b
FueL asseEbl.ies eobodyinS l8-pin
pellets
iuef
c
I gaaphite oode.ato.
d
Acllirg
Sectioil
the sleae goiilg lo the t!.:'bines.
oi'the
RBMKdesigi
adequacy aSairst
Tables 1 ard 2,
Hith
a.e desc.ibed
pa:'ticulaj'
UK saaety p:'ac!ice Hith
.efe:'ence io NII Safety Assessnenl Piillciples
a-e sunm6--i9ed lr
tube-
and aeflecto..
sa:'ient featu-es
the!.
c]'.rste:'s, each pin coop.isecl of
cl.ad i:l a zi.corlj.rrlll alioy
Hater coolant,
comneits .egaadi.g
statloal 13 a hyb.id,
plutoniuD.
a
this
\,Jith
of the RBIINreactoas a--e:
features
u.65i-Jn dioxide
ciacui!
paaertage can be taaced to the ea:"]y
Its
to paoduce loilita:.y
deslgr
lube,, S.aphite-
(nef 2).
Relevani pa.a.oeters
U:il.ess clhe:.Hise slated
the iifo.nation
is fron Ref 1.
2.1
Ove.vieir o! the RB K
The rDai:lfeat,.L-eso: lhe RB|.{X
a!"e show:1i. Fig 1.
is the.eactoa
The.eactc.
At the ceit.e
of the u'iii
cc.e lrith its suppoalix8 structu:'es and btol.ogical shieldlaS.
cool,a:it ci:'cult,
conslstlng of a coeplex aaray of pipeso.k and
valves, strpplles Hatei- to the fuel .char.els and t.ansports stean/water
Eixtuae to the sleae cLr"!Ds. Above the .eactc:. 1s the reacto. hal1,
ccrlai!1i:r8 the fuelllrg oachine.
the .eactc. a-nd p!.ida-.y ci..cuit.
A coltaia]lellt buildtnS pa.tially
slraolarcls
Aa inhe:'eit featu"e of the desiSn ls that the geieratlon of steaE ln the
fuel cha:inels oakes a positive,
.eaa:ivity of the co.e.
deglabilisi:rt,
cohtalbutic:r to the
I n n o a E a lo p e . a t i a r t h i s e f f e c ! i s c o l ! . l t e . e db y
ihe .eeative Doppe. :uel teope.atur-e coefficient,
These chaaac!e.istics aad
of ope.ation aequlred tc etsLr-e a stable reaatoa opeaati.agaegime
the lioi!s
a r e d i s c u s s e di a t e : ' i r t h i s S e a t i o r 2.2
Reacto:' aad SrrDpor"tligSt:.uctu.es
The aeactoa and lts
suppo.till8
structL!-es aj-e aho{n ta Fig 2,
The aeacto:"
co:'e is cyllndaical
ln shape, elth a dlarete!- Of 11.8o a-'lda heiSht of 7@
exciuditg t"effecto.s.
It conslsts of g:"aphite blocks asseEbledinto
coluBns, yith vertlcal, cylindalcal openings rhich holrse a total of 1661
fuel channels, 211 coitaol chaineLs and l2 axial detecto. st.lngs.
The
oarj.EirE teoper atuie of the gfaphlte is repo.ted to be abcut ?00oC.
coHl{Er{t
Thls 8t'aphlte teoperature ls [email protected] hl8hea thatr
thote ot yhl.ch the Ul( ha! expeplence. It 1! not
knoyn vhether the USSfihave qualllled the
Iraphlte
blocks for the ful.l .ange ol telpe.ature,
hlildlty
and i.rradlatton condltl.or)! oyea the destgn
Ilfe
of the Feaetoa.
the RBHKcondltlons
UK expeflence suSgeats that
a.'e very onerous for the
8raph1te.
T h e w h o j . eo i t h e . e a c t o r i s i o c a t e d i n a l e a k i l g h t c a v l t y ( f o : l e d b y t h e
uppe. aad love. shie1ds and a cylind.ical
steel sheil), Cesigaedto
{ i i h s t a t d a . : i r l e . r a l p . e s s r r e o f 0 . 0 8 M P a( 1 1 . 5 p s i ) . T h e c a v l t y i s f l ] ] e d
v i l h h e l i u , l ! / ! i i t . c g e re i x t u - e ( 8 5 - 9 0 i H e , 1 5 - 1 0 t N , ) w h i c h i l l h i b l t s o x i d a l i o n
cf the 6.aphiie 6-id i6p:'oves heat t.aisfe. f.oo the g.aphite to the cooli:lg
chan:iels. The HelN2 mlxiu-e is ci.cuLated th:'ough a ci.eaa-upeysteo whe:'e
1t 1s rlotito.ed fo:' teege.atuie aid eoistur"e colltert.
CoHXEIII
The relatlyely
hlgh Sraphlte teEp€rature edds to the -.'l
f
l- llportarce of excLudllrg ala troo the t'eactoa caylty. J
cavlty ls a ]atepal ghie1d rhlch takes the fo!.e of a
:'eseavoi:- (annulai' i! c:oss-gection) 190 outslde dianetea and
outside the.eacto.
cylind.ical
16.6m irslde diaEete..
The tank is fabalcated faod 1or a.]1oysteel, aald is
-':i
divlded inte.naLj.y into
llatef.
16 ve.tical
ieak_iight
l.1iih
coopa.tments fllled
The tank is suppoi"ted f:'on beiovr by the b.rilding
st.uctur e.
shield is a fabi'i.'aled steel st:'uct(l:.d, l?i! in di3.1lete.
The uppe. biofogicai
the -auei
It is p€.fo.ated by standpipes Hhich acco@Eodate
and 3I! in helght.
and cant:"ol channel asseobl.ies. The space betlreen the slandpipes is filied
Hj.th se.pentlnlte
conc:-ete. The uppe. shield suppo.ts the Loaded fuei
channels, the floo.
outLel pl.ping.
ha]l above, and the:"eacto. coolant
of the.eacto.
This enti:"e st.uctuj'e 1s In tLrn suppo.ted on .oLLe.-type
suppo.ts by the iate.al
shleld tank.
i n d e s i 8 n t o t h e u p p e as t . u c l i ! - e , b u t 1 4 . 5 m1 n
The lovea shleid 1s sloilaf
dranetea and a! hi8h.
.eacto. coofart lniet
The stauctu'e suppoats the gaaphite stack and ihe
piping, ard is pe.:o:aled by steel tubes which
accon')odelethe lowe. ends of the :-,rel and cont.ol channels. The i oHe:'
shieid !s auppo.ted laom beiow, by a fab:'icaled steel st.uctu.€,
vhich
l : ' a n s m i t s l h e H e i g h i o f t h e g . a p h i ' " es t a c k l o t h e b u i l d i n g .
lbove the uppe. shieid
is a gaile.y
standpj.pes ard the .eacto.
Hhich fo.E biolo8icai
insuiation.
outlet
containing
(o. .isej
the uppe:" ends of the
) pipes.
shieiding io:. the.eacto.
Above this
hail,
6j'e slaEs
6rd act as heat
on the standgipes and can be :'etloved to pe.nil
The si.abs.est
ac.es3 to the st6id2ipe fo: ._efue:lin5.
T5e luel
channel. ii-ust:ated
alloy
(z|.
4o!r.
Steel,/zi.coni,iri
2.5tr Nb) tube,
uppe. ancl Lore. steel
to the steel
st.uctu-^e.
ti!-ough
lA consisls p.ina:i]y
in:rg
88on exte.nai
alloy
t.ansi!!on
end-pieces.
di6rete|
vith
o: zj.conjuo
a wa]] thickness
pieces laciliiate
the attachnent
The irppei. end piece is.i8ldly
of
oi
attached
standpipe Hhich penet.ar-es and ia sealed to the uppe. shieLd
The lowe" end piece is
a bello!{s
unj.t l{hich
expaision betHeen lhe fuel
Bea]ed to the loea- shiel.d st.uct(re
ccoperuates
fo.
the
diffq.ence
channel and the .eactoa
cavity
in the:'Ea-i
st.uctrlre.
The fuel asseobfy, FiS 3A, is oounted in ard suspendedf.oo the top oi the
channel tube by a bal.l-type plu8 that seal.s the top of the channei tube.
THo fuel sub-asseoblies, each 3.5o iong 6.:e held togethe" by a sep6.aie
suppo.t .od and suspendedf:.ofi the pl,rg. Each sub-a3senbly coEp.ises 18
:-JeI pi.s spaaed by 10 stainless steel cellul6j: spacea lattices
The fuel ls.eplacecl on load.
(see TabLe
The cha-ge nachiie ca:aies out the seal.iag
a.i1dursea-l1r9 ope.ation .eooteIy.
The contaol. aod channel heads ar.e deslgned to accept the attachbent of
actlEtoas and also the lnlet cooling lrat e- supply fr@ a coollng system that
i3 Sepa:ate taoD the oain fuel cha-'Ine] cool.lng.
The fuel. chaineLs a--e lhe palliclpal oeans of heat relooval f.od lhe g!^aphlte
blocks. Graphtte nplston .1'lgsn flt a-owrd the p.essee tube, alte"nately
ri coDtact el.lh the p:"essrr-elube and the gaaphlte block, as lliustaated i:,i
Fig 38.
The cooii!18 of the 8:.aphite depeids upo:1the heai coiduction palh
ttl'ough the plsto5 rirg aaaaigellert.
c0ul{E}fr
the aap betreen the fuel charnel. sad the graphite ls lcall, so that fallure of the prelsure tube rouLd
re!d.t
blocks.
pressupe loads on the 8raphlte
Thls rould tend to ttlt
the bt.lck! a-'rd
1n slgnl.flcant
roul.d be ltkely
tg d,aDaSetheE, partlcularly
aftet
l.radlatlon.
CoEequentLy the Srapblte stack
appears tA be yuLoeable tA pl'elsute tube falllrre,
and tbere 1r a ltkel.lhood
to othe. tubes,
of propatatlon
Taken together,
desl8n-paessrl'e ol the ieectd
the .elatlyely
cavlty,
lor
the ]ack of
alrd the pressu.e
tsoderatoa deslgD appear yulnerabte
contalnDent above the.eactor
tube/&.aphlte
and could lead to r slgnlllcant
radloactlvtty
release ol
ln ar accldant that lDcluded D..essurc
tube fatlse.
the.lsk
reacte
ot lallqre
ppopatatlon.Dd breach ot the
aavlty ar'c contrary to XII PrlEctplq!
t52.espectlYelt.
2,4
ev ..
ot tallu--e
91 aad
Ltl
!iicar y Coolaii Ci.cuii
The p:i.eE-_y:r.cu:i (rliust.etec
2,3
bottol! of the fuel
top.
It
cansists
independently;
ia aigs . a.d i)
s i r p p ii e s ' { a t e j ' l c : i i e
channeLs End.eooves ihe ste6-e/vate.
o: t\ro siaila-.
in pa.ailei
loops, uhich function
each loop.efioves heat f|q!
ha]f
f.cxi tre
olxtire
6,id
auel
of lhe.eacto.rs
asseobl ie3.
In each loop,
heade. paases th.ough lorr
Hate:. f:"co the sucllon
eain ci.culating
p-dnps. Under" no: oai ope.atinS
at hiah poHe.,
conditions
th:'ee oi the foui' Bain ci.c',11atln8 puE_rsaj'e !n ope'atlon
:'ese.ye.
aid a p."essu-e of 8.q MPa (1218 psl) ard floes
valve 6nd a tlrottle
vaLve,
in sequence:
each of the 1661 iuel
channeis.
cont.oiieC by Eeans of lsoiating
th.ough the fuel
to sat.!'ation
and the eteao/rate.
HPa (1015 psl)
vhe:'e il
fiors
rixt,!-e
iniets.
in
an isciaiion
the dain ciacijiating
the 22 di.sl.ibuting
An individuaL
and .egul.airng vefves.
iine
heade.s,
ieads into
As !t
D6sses
su:".ounding the fuel, eieoents is heated
par.tiaj:.y evapo.ates {1/1.5t by reight
at a tsnpe:ati:j'e of
th.i"oirShthe individuaL
is Sepaaated inlo
valve,
pipes,
The fiorr :.ate tir.^o\rgh each channei rs
channels, the wats
tempe.atrre,
a non-aetrrn
passes into
whicb have non--'.eln-n vaives at lheia
one heid in
til-ough p.essrre
CooLant then flo',rs inio
puop piessur e heade., f.oE whe:e it
rith
puops at a teope.aluJ.e of 270oC
llat e:. leaves th€ 6ain ciaculatlng
each ol Hhich aae instai.ied
pipes !o the
ste6m and vatea.
.!se.
28\.5'C
sepa.ated out is E:xed ai the dr",ln outiets
{ith
!h.:.ou8il 12 downpipes (:.on
the suction
€ach di.Js) inio
6nC a p.ess,:'e of 7
p!pes into
The ljate"
or ave.age)
rhich
feed vate.,
the stee,r d.u.ts
has bee:1
6nd fiows
I
headea.
The tempe.alu^e of ihe rate. iLorin8 inio ihe suction heade:' clepencls
on the
.ate ol stea.o p.odiictlon o: the .eaato..
lhen this dec.eases, the
teEpe:'alu:e lnc.eases s@eHhal becairseof lhe chaaging aatlo of ratea faom
lhe d.uE sepa.alo:.s, a! a teope.aluie of 28lt.C, and feed u6te-, 6t a
teoperatu.e ol 165"C, Consequentiy, phen Lhe:"eactoa povea ls belor 5OOHW
le du-ia8 slai.t-up ca ehut-do-,rnope:ailorls, the fLor iate t}!-ou8h the
p.irda--yci.c\lj.t is cont.olied by using fi!-ottLe-type clntaol vaLvea and
I
.educlng the nurDbe.ol puDps ope:'ating to.eduCe the flcra f.oo the noaba.l
fate of 8000 E'llu. pe. pirDp, to the.ange 6000-7000o!/tl-.
This 13
necessa.:'y
!o ensui'e lhat th€ tedpeaatrfe at the oaj.o ci.culatlnS
2,5
puBp tilet
I
I
is low enoughlo ensFe thai aavliatlon cloes not occu:. in the pu;ips aid to
$ain:ain slean paoduction in th€ co:"e.
c0l.rlc[T
The paess8e tube concept €oployed ln the RBIX
aesu.lts ltt a luch Dcre cooplex aaran8eoent than ha!
De@oe qustooa-"y l!! the UK. Pa:'t1cu1ar dltllcuLtles
a
the potentl al le
lallrFe
gf the c@p1er ar.ay
ot plpeeork;
the potentlal
lo.
p.opagatlon of luch fal.l[[.eg
one plpe to anothe!", Ln vlee of the close
pFox!.lll.ty ol the ptges to ooe anoth€a and the
dltllculty
of p.ovidtng .estial.nt of, o.
tr@
seSregatlon betreen plPes;
the cmplexlty
Cee coollna
of the Elegency
Supply (ECCS)Deeded to cate!. le
bleaks ln any
pa--t of the cl.cult.
The RBHXp.es!t.!.e cl.cult
,.s knorn to have llttle
by
r.ay ot aestaatnt oa seg!'egatlon.
The ECCS1s
deslgDedonl.y to:. sin8le fallE-es
of pipe,
of spectlled 91zeg
The M.l].ne-abll lty o! the palEa.y cl.cult
!s @nt.a--y
to NII P.lnclple 91. It pould afso Eake c@pllance
ylth P.lnclple 109, on adequacyot coollng at all
tlEes, dtfllcuLt
to deooNt.ate.
lnsDectlon rould b€ dlfllcul,t
2.4
P.tncl,ple 46 f€
to Eeet.
EEe.gencyco.e cooltng systeE (EccS)
The ECCSi8 designed to Ealntain co.e cooli.ng in the event of pipe-faiiu: es
in the oain cooLant systeo 6nd in scoe fintact clacultn faults in Fhich the
suppl.y of nate'to
the i'uef channels is inte..upted
to. othe. .easons, [lo.
exanple: loss of feedwatea oa Loss of poHe. suppliesl.
'CCS is no.naily initialed
autoEatically,
Actuatlon oj'the
al.though it is knoun thal the
ope.atoas biocked ECCSope:"ation p.io. to the accident at Che:"nobyi.
Becar$e lhe -'.eacto. cooiant systen is a-':'angedin tHo sep6--ate, lndependeni
loops, the ECCSEuBt be 6i.an8ed !o Ineet lhe diafeaing fqnctlonal
.equl.enents a3soclaled rJllh lhe b.eached and intact halves of lhe aeacto..
The Chernobyl SCCSconsists of ttL-ee sub-syslens (see Fig 5) al.i connecreo
to the dist.ibutlon
heade.a of the coolant systeo.
one sub-systeo paovides
fLov to the dareSed half only, dualng the ea.:'ly stages of a b.each, du.-lng
wlrich tloe,
cooilng of the undaDagedha]f ls via the notuai RCSroute.
The
othea tvo ECCSsub-systeos tr-ovide long teao cooling fo. the aeactoJ", one
sub-systeo fof each ha]f.
Sho.t tem cooltng of the b.eached haif 1s p.ovided by tll-ee t.a.tns of ECCS
equipEenl, coopaising tHo accufiuLa!o)^taains ancl one puop€dtfain.
Each
consists of s1x accurlulato. tankg, containj.ng satea yith a
nit.ogen gas blanket, E:aj.ntainedat 10 MPa (1450 ps!), and is capabie of
acci.rrDul,ato:.
l.ain
deiive:ing
50t oa the oaxlnuo fLoH requi.ement !o the daoagedhalf of the
:'eactoa, io. not iess than 100 seconds afte- the inillation
ot the baeach.
ECCSfiow ',rithin 3.i seconds of the
The thi.d taain utiiises the feed puops,
Fast acling valves aFe used to initiate
b.eak in no.oal vate. suppiy.
$hich a.e electaicaliy
a,r Haie. f:" oo the deae.atoas. The
d.!ven and rhich cL^
p u B p sa a e a e a l l g n e d t o f e e d d i . e c t ] y t o the ECCSheadeas. Thls :.oule i.s
capable of deilveaing 50t of the oaxiduo fioll .equlaeoent to the danaSed
haia of the :.eaclo..
Long te:t
cooiing of the d6Da8edhal.f of the.eacto:.
taains oi ECCSequiFlent.
is pr.ovlded by thj'ee
Each t.ain consists of t{o puops connected ln
pa.j-a1]el and is capable of delive:ln8 50t of the oaxiEuE fioe.
The putps
drav pate. f.oo lhe p!'es3i!-e suppa€slon pools beneath the aeacto., the
Hate. being cooied by se:.vice lrate. ln heat exchange.s in the puEp suctlon
LonS te:'a cooLlng of the lntact haif of the aeactoa ls paovlded by thaee
t.aiN
of ECCSequlpoent.
Each traln conBists of a slngle puEp d.arlng
natea faoo a condensate stoaage tank, ard ls capable of deiive.ing 50t of
the aequi.ed f1oe,
I
The iCCS is !.lgge:"ed by the colncidence of a high p.*su.e
sj.gnaL f:'oc
cqlpaat&ents contalnlng the llain cool ant plpeHo:"kand eithe:' a iolJ level.
si3na1 f:"o@the steao daubs o:. a si3nal lndlcating a clec.easein ci..cuit
P.e33[-e d-op.
?he iatter
identiiy
the dariagedha]f of the .eactc!..
It
ls a .equi.€oent that the ECCSEu3t iulfi1 its fr.nction in lhe event of a
Ioss of noaEaLpore- supp1les coincident elth the ndestgn basls accident".
The no.oal pover. supplles foa pudps and va.Lves ln the ECCSaae dealved f.oo
the 8:"id, but in the event that the g.td is losl then powe.Fcan be obtalned
fa@ the aunnlng tc-bo-gene-ato. ( s ) . Du:'lng trrbine .un-ctoyn, the tu"boSene^atoa autinues to suppo.t the ae€dpuops ehich cont.lbute to sho.t te.o
ECCSduty foi 45-50 sec\cnds. Subsequently, dlesel gene.atois a:'e b.ouSht
ln' to pone- the pdDpsin those sub-systeEs l{hj.ch contalbLlte to longea te"m
cooilng.
ECCSvalves rhich cannot aacepi intear-uption in suppj.ies aj'e
suppo:'ted by i,atte.les.
The eteagency [email protected] l50t .edlJndancy. The desiSn is claided to
take account of unp.oductlve loss o: cgoiant thaoilgh the b.eaqh, ancl a
51n8l,eactlve o. passlve failu"e
col.rltEltT
UDavellablllty
wlthln o:. outside the ECCS.
ot pa--t of the systeo due to
EalDtenaDce doer not appea.. to be taken lDto
rqcount a! yould b€ fequlred ln the UK. l|hllst
detaued .e1tablllty
the colpLerlty
a
assessent hes noi Ueenoaire,
ol the systeo and 1ts dependenceon
valYe aLlstEent rould p!.obably rerqlt ln lot e.
fellabi].lty
than yould be requlred 1n the UK,
Ptlnclple!
37 .nd 121 and Ref l.
cater. !o!. staglatlon
The ECCSdoe! aot
accldarta althouSh such
oqcl!'icnClat ar.e deared to be polslble
tube reactocar PrlnclDle
lo piersrae
109 eould thet"efee
Dgt b€
ect.
2.5
Contal.nnent Systeo3
The Che:"noby1butldlnS stauctu-e 13 desiSnedto contaln and conflne the
aeLease of J.aclloacttvity folloHtng fal1,J:"esln ce|taln parts of the .eacto:'
coolant cl.cult.
The contalrutent st.uclu.e and assoclated syslens oitlgale
2.5
the effects oi p.6sur:e-pa.t failu-es
in the iorea paats of the dorncooe.,
the pi:ops, lhe p:.ess,!-eheade.s, dls!.ibution
heade:'s and inlet
pipeHo.k.
Hcjveve), faif ,l.es in the uppe:' pa: ts of the fuel, channel, the .lser. pipes,
the sleaE aepa--alo.s lheoselves ancl the uppea poatlons of the downcofte.sa--e
not cate.ed foa.
The bounda.les of the containdent stauctuaes toRethe. e.ith
the p:.ioa:'y ci.cult
a--e sbo'rn 1n Flgs 5 and 6.
The palncipal leatrl].es of the contalrEent systed araeshorn and nuobe.ed in
F i s 6.
These a.:"e
Leakt!ght ccopa.tfierts encloslng the p\rEps (labe11ed "1n) designed foa
a n o v e . p . e s s J . eo f o . ! 5 H P a ( 5 5 p s l ) .
Connectedto lhe leaktiSht Ccnpa:"tdents:a Ste6a dist.ibutlon
(4) and a tro-sto:.ey p:'ess',!Fesupp.ession pool (5), pa.ttaity
Hith Hale.,
The pe.titions
co.ridoa
ailied
aae pe.fo.ated by non-.etu.n vaLves and
venli n8 channeiS.
cctnpaatTents (2) enclosing the distaibutlon
piPing vhich {iji
tofe'6te
heade:.s and aeacto:. inlet
an oveapaess.r.e o! 0-08 HPa (11.6 psi)
,h1ch a--e v€nted to the steaE di,stribution
and
co:.,iido:. via non-.etu-n
valves.
the :"eacto. cavity (3) shich lriil tole.ate an ove:'p:"ess\!.eof 0.08 MPa
(11.6 psi) is ventecl to the pi"essu.e supp:.ession pooL.
the:'ise.
pipe gaLLe.y (6) and the slear d..r.r cqlpai"t$ent (7), which
a:e not desi3:red to rlithstand ovq'pFessrFe 6--e noaoaliy oaintaloed
p.essr"e slightly belov that in the .eacto. hai1.
FolloirlnS p.esslre cl!.cuit lailures
at a
ln the puop coopa:"toentsoi the g.oup
header cgEpal.teents, steaE/vatea 6nd a1. a:e vented to the supp:"esslonpools
via non-:'el,-!-n vaives and ventlng channeis as ghorn in Fig 7. The ae6Jl'ts
of calqulations paesented by the Sovtets shoe that the coDpaatdent p.essuaes
.eoaln
beloH the desl8r] values fo. the cases of fa1l\L-e ol a puop p.essu.e
header, e dist:"ibutlon heade. o. a sligle
2.9
iuel channei vithin
Lhe .eacto.
cav:iy.
A sepa.ate ventinS : oute is p: ovtded foa the r'eacto. cavity, as
iil$t.ated
in Fig 8.
The'e is pi'ovlslon fo:'heat.eooval
faor! the contairhent cdlpa:"toents and
aaoE lhe paessJ:'esuppaesslon poo1s. Su!face condenseasln the stean
co:".ido. .@ove heat onLy du.lng accldent condttions.
A spalnkle:'systeo
ope.ales Lloth dL-lng noaEal. ope:.at1on ard duaing accldents.
lJate' ls cl'asn
faco the supp.esslon pool anc! ir cooied in a se:'vlce uatea heat exchan8e.'
The Ha!e! is then dlaected to the a!. space above the supp:"esslonpool,
Hhe'e it olxes and cools the a1., and to let cool ei.s ln the upp€:' (hottest)
pa:'t of the containEent c\oopa.tEents.
The Jet coole.s ent.ain ai., the.eby
cooiirg the enviaonbent and aeEovlng aadioactlve aerc€o1s and stea!, The
wate. is coilected and .et[-ned to the sJpp]"essionpooL.
P.ovision is madeto maintain the concentJ'atlonof hyd.ogen belos 0.2t (by
Hyd:'ogenis present in the cantaldnent voluEe dsing no:'@ai
ope:'aiion oHlng to cooiant Leakage (assrred to be at a .ate of up to 2
voiuEe).
L/hr).
Dlring accidenl conclitions hyd:"ogenoay also a:'ise i.ool a zi.clniJn_
watei aeactlon.
To catea foa thls,
ala 1s d:'avn faq[ the @ntai lent vol'Jrne
at tl're.ate of 800 ro!/hL-dL!.ing no:"eal.ope.atlcn, and is dischaaged to
atocsDhe.e via fil.t:"alion plant. The plr 8e is autcoatically discontinued
inneiiaiel.y aciloHlng a faii'J:.e of lhe coolant ci:^cuit 6nd is lhen
.einsiated nanuaiiy a-lte. a pe:.iod of 2-3 houas, as hyd.oSen acc,hufates.
coHt{EhT
Frovtllon of a
the ieactoa and Lts prlDary
NII P:.lnclp1e 152 .egrl.es
@ntal.Boent aro$d
cool6nt clrcult
protectlon
unl.ess 1t can be lhoYn that adequate
has been echlered bt s@e othcr DCaD!.
The RBI{KF.actoa ha! pErtleL contalrEent ot the
coolent clpcult 8Dd thls yould probebly fall to leet
gX reqrli.!.nts
ot the
Btv.n thc Yuln.rabtllty
p.lB.rt
cl.r'cutt (sc. Sectlon 2.3 .bov!).
2.5 !g9i-$rrlLg!!9g9
The che.nobyl po(ea systens fo:. liJlobea4 reactoa aae ll1ust.ated
in Figs 9
The statlon has tvo Ealn Beneaatoasconnected to the 750 kV gaid
via a eingLe gene.ato.-taansfo:'ae . Tl{o geneaatoi svttches aae tnstalled in
end 10.
2, 1C
seaies wilh each Bain Sene:'ato:'and a cainecf,lon:o]. a unit taansfoanea is
olade between each pai:" of gene.atoa sr.itches, The plant also has a 330kV
c\cnnectlon lo the 8:.id vla a statlon t:.ans:oaoe., al.thouSi,this .oute is
noaoal.ly isolated I'or! the oain elect.ical systeo. Theie powe. gupplies
feed the maln dist:ibutlon bo6:"ds (io {hich loads such as :'eactoa cool.ant
puEps alrldfeed punps, a:e connected) and the es€entlal dist:ibution boa.ds
(to vhich essentlal dalves, such as ECCSpuEps o. clntalnnent spaay puEps,
a:"e connected),
o.oal poeea supplies foa house Loads a.e obtained via lhe unit taansfo:lea.
The follor.lng
pore. sou-Fcese:.e aleo aval.lable in va:.!ous ope.at1n8 dodes:
folioring
a .eacto. o:' tu.bine trip, suppLies can be obtained f:'oo the
750kV gai.d via the gene:.atoa taa-rsfo:'oea.
fol1owin8 loss of the 75okv g:'id o:' Seneaato. t.ansfo:'se. supplies can
be obtained ::"oG the 33okv g:.id via the g:atlon taans:o.tle:'. This
route i.s no:maiiy lsolated and i!
it
is noi cleaa undei vhat ciacu.astelnces
Hould be conlected, no:' how long the connection eould take.
folloring
faults lnltia:ed
by .eacio.
cooiant ciacuit faiirl:'e eith
coincident ioss of no.mal pove: sup_Dliesa,:ld+-u-"binetalp, the aunning
donn tuabogeneaatorscan be used to suppo.t eiect:icai
a liDilect tine.
systeo loads foa
Thjs oode of ope.ation is used to su.opo.t the leed
purp in its ECCSnode fo. a peaiod o: 4i-50 seconds.
foiloHlng loss of aI1 ofl-alte
supplj.es, essential loads can be daiven
f.o6 diegei Sene:atoas.
Folloelng a loss of off-3lte
porer, any.utrning *sentlal
loads a.e t.ipped,
the die-sel geneaato.s aae sta: ted autooatlcally and connect€d to the
syster Hilhln 15 seconds, Essential d.lves .equi.ed by the
incident a.:e sequence8ta:ted f:.oE the aval1ab1e pore:. sorrce (gald oa
elect.ical
dieael. geneaatoa). Auxll1a.ies rlhlch cannot accept the lnteaauptlon of
supplles aae suppoatedby batte.les.
The thiee g:"oupso: essentlarl safety
equlplrent and thei. contaols have lndependent polre. supp1les, aB !llust.ated
iir Fi8u.e 9.
cor{l.Ettr
-
Ihe Eslentlal. Electalcal. Systeo playa a lreJor' tole
1!l enlualn8 cofe @ollng foUoilnS
faults
such as
braache! of the p.essrre cl.cult.
Unavatlabtlltt
E]ect:.tcai Po.e. orlns to
Eal.nten.nce, 1n c@blnatl,on yl.th a shgl,s lalfrDe
of
onc t.a1n ol Esscnttel
a ac@nd tt altr, r,oufd r.sllt
coollnS crpacltt
!|(E
ltl l
dequate @re
the oo. fdrtllDg
Thc stst€o rould not Deet III
121 or the CE(E crlte.l8,
ln
50t tt.ln.
Prlnctples 37' 112,
het {.
2.? Isg!i9!-+L!st!sl'!s
The neulaon fLux detectoas aeeuiaed foa Eonlto.lng, cont:"ol and plotectlon
a.e located in-Co.e and ex-coae a3 d*cfibed
beios.
pul.se detecto.s (KNT 31) 6r"elo!.e.ed inlo lhe .efi.ectoa fo. eta.t
:'6i8e ls .eached. Th€y
they aae withd:.awnehen the next me63!!-emenl
! lisgion
up.
cove. the aange 8 x 10-t2 to 3 x 10-' of fJIt
po{e..
4 sensitlve i.on chanbe.s (KNK55)located in the shieid tank Sive Pe.iod
p.otectlon clring sta.t up f.oo 3 x 1O-! to 5 x 1o-2 oi fuil povea.
4 ion chaEbe.s (KliK56)located in the shield tank slrpply the signals to
(systa,r!AR2) in the.atSe 6 x lo-t
cont.ol the io'r- i.o!r poHe- autolallc.ods
to 1.5 x 10-'of
f.,rlI poeq'.
8 lon chaDbe.s (lClK53M)located in the shield tank supply the siSnals to
cont:'oi the teo 3e!5 of fou. autooatic contr^ol aods (systems ARl and an2) in
the:.ange 5 x 10_2 to 1.2 of fuli
poHea ove:.shoot paotection.
powea. The slSnais a.e also used foa
4 ton chasbe:s (XIK53H)Located 1n the shlei,d tank supply slgnal.i fo. poHe:'
Eoaitoflng and pe.iod p.otectlon.ln the !'arge 10-5 to 1.2 of fuLl po!.ea.
2 lon chaDbe.s (KNK53M)
located in the shleLd tenk 3uppiy 518rai.3 toa llneai
pove- readlng in the aange 10-z to 1.2 of fu.l1 porea.
2.12
Paoteetlon1evel 5 is activated by:
A poweaoveashoot of '0t of nominal 'ul,l, poue:
A .eduction in the .eactor" peaiod to 10 secldds
D.uo sepa--atoalevel high o. lot{
LoH feedHate.
floIJ
Excess paessu.e in leaktight
coGpaatsenls; d.un sepaaatoas, aeactoa
cavity oa foFea nate: 1ines.
Low contaol-aod
cootant-aeseave oa cool an!-f1oH
Taip o: tvo trrbogene.ato.s
T.ip
of the oniy ope.ating
tlrbogene'ato.
T.ip
oi 3 out oi 4 ope:atirg,
dain ci.cu-latinB
pr.ltps in eithe.
pLxlp
aocro.
in the plait
voitage
loss
Fai:u.e
to .espond :o p:'o:ection
alixili6.y-poHe.
suppiy-syster
leve.l 3,2 o:' 1 deoEnds
I'ianual t.ip.
Paotectlon level 5. is actlvaled by 6n eoe.gency pollea oYe.shoot, 8ene.a!ln8
a paatia-] t.ip, stopping the:'ods vhen the oveashoot signa] clea:"s. The
dtstj.ncbion betveen a poHeaoveashoot actlvating level 5, aid an ele:'gency
po{e. ove.shoot actlvatlng level 5t, is not cfer.
With such heavy:eLi6nce
on the opeaato. to Eaintain a stable configlration
nanual .od adjustoents, lt
and lo ce.ay out so oany
is believed that ievel 5r is the do.oa]iy-
activated Level ln:.esponse to polreaoveashoot, sith lul1 taip by ievel 5 as
the Eoae ex:aeme backup-
?.15
I
t
P.otection ievel. 3 is activa:ed by:
Load :"ejectlon by both tFboaeneaalo.s
Load aejeation by the only ofJ€:'atingtrboSeneaato:"
P : ^ o t e c t l o nl e v e 1 2 l s
activated by:
outa8e of one of teo tlFboSene:"ato.s
Load aeJectlon by one of tro turbogeneaatoas
Paotectlon level 1 ls activated by:
Loss of I of 3 opeaating Ealn cl.culation
Reduction o: nalea flor
putaps ln eitbe.
p-tlnp:'oo{n.
in the paina--y ciacuit.
Reduction oi feedratea ::or.
Reduction of ]evei in the d.un sep6aato:'s.
Actuation of the goup closl.re key fo. the coolant ci.cuit
.egujatirg
COII EMI
valves.
- P.lo- to the Cheanobyl accl.dent a nuober of trlp
pa:'aDcte.s res'e blocked shoslng that the paotectlon
38 atrd 131 on
unauthoals€daccess. Prlnclple 38, 1n paj'tlcula.,
says iuBautborlseal acces! to and lnteaference 91th
systeo i.ould not oeet NII P:'lnclples
gtfuctrses, lysteos and c@poDentg
lafety-related
llle
should be pFerentetl bt rultable !ea!tae!t.
Drotactton ststa! ts theaefc,r'c not adequate
(PrlnctpLe 107). Detalled lntcrdatl on and analvsls
rould be requlrcd to l!!e!!
c@pllaDce ylth
total
Prtnclpl.es 121 and 122 rhlch lay that tg cat€r fe
feults
-
o. oalope!.aEloE the p!'otectlon
€obody dlveaslty
and aedrmdancy.
2, 16
lylter
lhould
+"haottie
2. r0 3999j!:_.Q.9is!_i!!
T h e d e t a i l . e d s a f e t y d e s i g n p h i l . o s o p h yo f t h e R B M K . e a c t o a a i s n o t a v a i i a b i e .
Howeve , lhe physics cha:acte:.istlcs
the no.Baf ope:.atiig .egioe
positlve
void coef:icient
outlined
Eust be constaained by the :'equlaement :hat
ts llolted
*iy
in the Appendix iLlust:'a:e
ln dagnitude,
leading
the
to a negative
value Of the po\rea coefficient,
These aequlaenents a:e affected by poxe:' leve1 and a coobination of cont:"o1
.od ro.lh and inse:'tlon.
Hence:
The Hoath oi cont:'ol. :"ods lNe:.ted
should be suJ:icient to.est:'ict
du.ing nollaL porea ope.ations
the.eacto.
v o i d c o e a a i 3 i e n tt o a
ievel consistent with a negatlve pove. coefficient.
An on-line
r
o
p
e
.
a
t
l
n
g
:
.
e
a
c
t
i
v
i
t
y
c o i l p u t a t i o no f l h e
o a - - 8 i n r i s a v a ! i . a b l e! o t h e
o p e a a t o ao n d e o 6 i d . I f h e s e e s l h a t i t t i e s o u i s i d e a i . l b i t ( s i a t e d t o
be at least 30 equivalent :'ode lnse:'ted in the coae) then he is
srlpposedto t:"ip the :.eacto.. The ope.ating aeectivlty ma.8ii is also
quoted as nlt no.th of inse:.ted :.ods,,- The enfoaceneit oi this iimit
is the:'espoisibiiity
of the opeaatoa and no specific
design p.ovisions
E:'e fiade to easr::e coBpiianc€.
Suslained po!re:'ope:.atiod 1s peaeltted only above a ioHea limit oi 201
ot fuii posea (Bei 3) and opeaa:lon beioir this 1evel is subject to
special .estaiations.
A g a i n e n f o a c e m e not f t h i s 1 l m l t i s i n t h e h 6 n d s
oi the opeaato: and again theae aae no speci:'ic desiSin paovisiois to
ensuae cqDDfi:nce.
col.rr{Elo - In the UK, the lntentlon
ls tbat the sa.fety case
should be e-stabllshed for the edtl!'e .an8e ot
.eacto-
ch.-ractet.lstlc3,
by !od!.fylD8 the d6ttgn
and/o. the fuel Lgadln8 so that onl.y acceptabla
cha--acte.-Istlca arc bullt
lnto the .eacto..
olnlErE requlreoent, 1t eouLd be necerlary to
enslrie, by the froylllon of lnte.locks e
protectiotr, that th€ opeaate could not
2.17
As a
lnadvealentl.y altea the iaactor. che.aacte--15tlc! so
that they serlou!1y devltted
faco the assr.EptloDs
paescnted ln the satety anal.ysl!.
lbe RBXXde!l8!e!.s
d1d not de.!.gn or p.otect
aSalist
ol uIEat€ nalop.iatloDs.
They lett
to tflp
the r.eactoa lanually
that tha poear coelllclant
FII Pilnclple
57 fcqulres
characterlsttca
the posslbl,ltty
the op.rata
thafe r.a! a tllk
vould bacooe posttlre.
ll
that thc de!18n
lhoul.d ba ltable
and haye no slddeD
changc outslde tha specltlad
pattlcuLsr
P.lnctpIe
PrlnclDte
43 fequl...
opeaattt!8 LlElts.
In
58 rdd.Fes!es cool art yotdlna.
that the d.s18n .lbuld
any ope:.at1ng Eode etceedlnS lafe
l,intts.
preveot
P.lnclpl,e
57 t eg\rl,!.es that Dov€oent ol coie c@poaenta that
could 1nc!'ee!e aeactlvlty lhould be controlled by
deslSn.
The R9l{Kdesign voufd not Eeet ant of these
aequlieoents.
To tr'ip the:eacto:',
the conti"ol:'ods a.e d:.iven into the co.e eiect.icaiiy
at 0.! oetaes pea seconcl, takiig sc,$e i8 semnds to taave:"sethe co:.e
I e n g t r . T h e i ' e s t . i c t i o n i n ( a ) a 5 o v e: s s t a l e d t o e n s r e t h e . e q J r . e o
initiai
t:'ip Lro:'th of B pe. second, eheae I is the.eactivity
the deiayed neut:'on iraction,
COHTEIT
about 0.55t at equiLib.iuo fuel cycl.e.
The RBHKp.otectton
lnclude!
stop lf
It
equivalent o:
sylteo
ls t|rllsual sllrcc lt
a 1eyel r.hlch a]lol.s entry oa the aods to
the ln1tia.l trlp condltlon clears.
seeo! p.obebl a that tha cdDh.sla on EallltalnlDg
reactoF ayallabllttt
attttqd.
he! Intluenced the opetrtofts
to the lDDort&c!
ot tt'10 furctlotE.
Beaclingsffor! the 130.ad1.e.1and 12 axla] ln-coae detecloas a".e p.ocessed in
a centr.aljsed rdonlto.lng syste6, knorn as SKALA,r.hlch cooblnes the detecto:'
:'eadi:18stith
:^eacto. calculations p:.ovlded pe:"lodically by links to an
exte.nal. cooputer to der"ive the integaated porea of each fuel assenbly and
poHe. paofiie.
the associated axiai
ylth
oeasured assecbiy flos
oa.-gln to c.itical
nucleate
bolllllg,
These poee. dist.lbulio$
aate! atd l!1let
heat flux
co.ditio.s
a."e combitled
to caicu.late ihe
1t each assembly, to exslre ib departuae f.on
r'hlch iJould lead to fuel
oveaheatj.:18.
Unacceptably lov Eaaglns to ct'1t1cal heat flux ln any asseEbly a--e dlspLayed
to the ope.alo. on a.eacto. olo1c plan eYe.y 5 to 10 Elnutes, togethea Hith
a !"ecooEeidation oi floe adjugtoent to Ehe asseobfy, Hhife the autdatic
cont:"ol systeo lniiiates
a local
oa r.eactoa pose. seiback at zeao !la--8i'l.
The florl to each asseBbly cai be adjusted by the opeaatoa a'ld, ln
equtllbaiuE fuel c''cle, an adj'JatDert ls oade at least teice i.l the life
of
each of the 1661 :.Jef assemblles, !o optiolse the reactoa outp\rt.
Stablllty
of the |eactor'povea ard power"distaibuliol
ln nomal operation is
co:ltao]led autqDaliaally by lHo dlscaele 8.oups o: .ocs:
the autcoatic eean poee. aeSulatirg 8aolr9. iithea of teo 8:'oups of
forr coit.oi
lhe .eacto. powea !n :"espoa.seto siSials f.oo detecto.s
the lateaaf'{aie:"
shieLd outslde the co.e
the ioca] automatic coit|ol
gioup of aods divi.ded iito
12 slngie.od
zoies, co:1!.o:i1!1a illstabi.lities lt lhe .acj.aL azioulhal posea
j.n .espolrse to 918nals i.om ioca:. detecto$.
This
dlst.ibutlon,
co!1taol.fu.rciion is backed up by a local ede.Seatcypaotectlon system,
nhich eithea:.eezes
the autooalic:"od vithdrawai oa inseats local
eEefSescyproiection .ods.
The opeaatoa 1s exp€cted to tal!
the .adial
aziEuthal. povea distalbuttoo
ooveoent of a'ly ol 139 Danual aod! to optleise
hai'oonlc ln any axlal
poee. outPut and allo
ellEioate
the fi.st
lnstablllty
.ods lito
tbe toD oa the co.e o.t 21 shorteted abso.be. tocls lrto
by
to
by ooveoent of aa-'lual
the bottocl
of the co!.e, as app.op:"iate.
The SKILI lorltoailrg
systeo contput4 the total
.eactivlty
contj ol aods inseated into the co.e, by axiaf statistical
the axlal paofiles :.oo the axial. detectoa staiiSs.
r.o!"!h of a]l
velShtlng usiig
The .*ult
is c@pai'ed
eiih
lhe ope.atoa of any shoatfali.
so lhat
co..eclive
saoe aesul,i ls used to assess the iaitiaL
aeactot talp,
l s p r - o v i d e dt o
6a.gin of 1i ard ar irdicatior
the ope.etive.eactiviiy
foa Ccopa:"1soneith
ieaclirity
the.equiaed
The
actio!1 ca:1 be laken.
rro.th avaiiable
fo.
oiniouE Of 0.55t pea seclnd.
The .ole of the opeaato:"ln high poHeaopeaation ls the.efo.e to:
adjust coola-')t fLon through j.rdlvidua] fuel asseobl!e5.
11
cont:.ol axlaL lmtabtLltj.€
by ooveoe.t of tt.o types of absofber,
11t
Ea-'rual.lytalE the aadial-aziEuthal po\.readlstaibutloil to optiBlse polrea
output, consistert eith the autooa:ic corlaol by the locai autoaratlc
iv
ope:'ate such that the opea6live r"eactlvity Ba.gln is oaintained a'id
ihe.efoae ihe void and pollea coef:icieat
6r e rithin
the safety deslgn
lio-its.
in conj,!',c11on rj.lh
lhe auto.:atlc
vi
ii
corj,r'ictior
cort.ol
trith
least 0.55i.eactivity
COMEhT
(iv),
ensuae ei:ective
:"ods Lrithj.r o.ese'ibed
(iv),
laiatbair
actior
contaoile.
the iniiial
inse.iio!1
l.lmits.
.equiaene.,t
taip
eoath pe. seco.,d-
Fa€6 the above lt
can be seen that the deslSn places
an uFeasonable onu! on the oDeratoa to eisure that
the plant 1! rlthln
safe op€ratlng 1l!1ts.
a]loys accass to lEportant
It aLso
pnotectlon ltsteo!
o! the satety
tbe Fosslblllty
of llyalldatlon
fuactloa.
Ielthcr ot thele aspects roul.d be
a9ceptable ln the UK.
by holditS
elth
of at
neae:ences
1
rThe accldent at the Che:.nobyl nucleaf pove. plant €nd lts
congequencestr,infoaoatlon cloplIed foa the IAEA Erpeats Ueet!n8,
25-29 August 1986, vlenna, by the USSBState Cooolttee on the
uti.I lzation o: Atcric Ene.gy.
'Safety assessent
I.Etailatlons
palnqlples
foa nucleaa aeactors',
HH llucleaa
InsDectoFate, HllSO, 1979.
nI SACarbE6.y :.epo.t on the post-accident aevier DeetlnS on the
Chernobyl accidettn, Vienna 30 August - 5 Septeober 1986.
nDeslgn safety c.ite.ia
fo:" CEGBnuclea. powe. stationst,
and Se-:ety Depaitoent, tls/R167/81 (Revised), 1982.
CE@ Health
E
&
TABLE1
oene.al SPecification
Theanaf po{er', l{J
3200
Elect:"lcal. pove. (at Sene-atlng te.Dinais,
MH)
1000
Actl ve co.e dlarlete., !
11,8
Actlve co.e height, E
7
25o x 250
1661
Nuobet"of fueL chainels
Nunbe!. of controi
iod channels
Constant u-aniJD dloxide cha38e, t
20\
U!"anlun, en.ich[ent,
2.O
t
Maxl&uE desigr che,nnel.polJe:., klJ
PoHe. of lrost hl8hLy !.ated chennel, k|.l
27AO
Cooiant floH in Baxlouo poFer channel, t/tr
28
Cooiant flor
37.i x 10r
t/ho'..F
Maxlalro stead content wt I
20.1
MeanbuLk steao conlent ht t
14 . 5
Sat'J'ated stean tedpeaatFe, de8 C
28t
Cooiant tedpe.atse
at fuei channel lnLet,
deg C
270
satuaated steao paessu.e in ct uE sep6iators kgflco2
Feedi.ate:" teope.atu.e,
deg C
Maxi.E',.bpeanissibl,e Staphlte t€opeaatuae, deg C
Bu-n-up Hm/kE lfanir!
165
750
Key
'| Reactor
standplpes
2 Fuel-channel
3 Steam/waterrlser plpes
4 Steam drumg
5 Steam headeF
6 DowncomeB
7 llaln clrculatlng Pumps(MCP)
8 Gmup dlstrlbuilon headers
9 Fesctor Inlet w'ter PlPes
10 Burlst-candetectlon system
11 Upper blologlcalshleld
12 Slde blologlcalshleld
13 Lower blologlcsl thleld
'14hrrdlated fuel Elolage Pond
15 Fuelllngmachlne
16 Brldge c.ane
-- .-* F-1s.,! 9ECTIONA- VIEW OF RBMK - rOOOBEAGTOR
Charge face
Coolant
outlel
s""d_____--l-._l-
Helium/Nilrogen
Nitrogen
Upper & lowel
neulron shields
--- Graohilemoderator
Water shield
Coolanl +
lnlet
Supporl sleelwork--
l
lt I
1[
Concrete
(Biologicalshield)
FIG. 2 SECTIONTHROUGHRBMK REACTOR
Plle cap (Floorot refuellinghall)
Removableshleld block
Bottom blologlcrl shleld
and corc suppon
slruclure
Fuel channel seal plug
Upper tuel assembly
Coolant
Top lhermal shleld
(Steel)
Zr - SS joint
Channel shroud lube
Upperblologlcal
shleld and
channel supporl
Lower luel assembly
Bollom retleclor
slruclure
Boltom lhermal shleld
Zr - SS lolnt
Neulron shield plug
(Helical)
Channel feede_rpipe
Coolant inlet
FlG. 3a FUEL CHANhiL
(
W,
ti
k;
h
|
A;
ftl
Hq
k
80 mm Inslde diameter. I
-_-+l
K
ffi
["d
Bi
p,{
Pressurclube
4 mm wall
thlckness.(Zr-2lrNb)
Graphlterlng (lnner)
ffi
ffi
Graphltemoderalor
stacl(
Graphlterlng (Outer)
Preaaurelube
FIG. 3b ARBANGEMENTOF PRESSURETUBES
F'iDE
IN
IIEAFTftI'
Fuelllngmachlne
Rerclor
Pi€3sum h€adar
Malnclrculatlngpumps
Oowncometplpea
Sucllonheader
Reactorinlet waterplpes
Sleam drums
Prcssurcsuppresslonpond
Cenlre llne of reaclor
FIC. 4 GHERNOBYL 4
,{
ECCSaccumulatorstor
short term coollngof
breachedclrcult
Steamdrums
ECCSpumpsfol
long term coollng
of inlact circuit
ECCSpumpsfor
long term cooling
ot breached
circuil
ii
|
||
,
-
it
L_._.r_._.r._
tl
|
Cooling
seavice
water
Suppresslonpoots
Feedpump alignedto ECCSfo. short term
coolingol breachedcircuit
FIG. 5 SCHEM-ATICDIAGRAM REACTORCOOLIITIG
a^n..t'r^'
CIRCUIT
AttlD Ft|FltnElr4irt
FIG. 7 VENTING ROUTES I?I THE
cr'rN-f
a I rrl/| E llrF |srrQrrF rt
TEM.
OTEOTTHE REACTORCASING
FFCIF
rlltEcGl
rhF
APPENDIX2.]
A2.1
. PijYSICSCHAR.ACTERISTICS
OF REMK
In!roduction
The object of this appendix is to aevier in a sinple lda.rlnea
the pe:"foaoance
cha-"acteai s tl cs of the 8!HK aeactoa Fhich a:e felevant to an undeastandlng
of the Che!.nobyl accident. tt Hl.]l. be shorn that, as in othe:' .eactoas
cooled by bolllng watea, the hyd.ogen atcrts ln the coolant have an iapo.tant
lnfluence on the cou-se of the neulaon chain aeaction. If theae ls s@e
dlsttrbance to the steaE p.oduction 1n tha coae theae sil.l be a feedback
effect
on.the pore!'output which can in painctple be poeltlve
(destabil1s1o8) o. neSatlve (stabilistlg)
dependlngon the details of the
co.e desiSn. Tbls appendix the:.e:oae p.esents a quafitative discussion of
the physics of the neut:'on cycle ard of the heat .edoval paocesses in the
boilinS coolant, so that the facto.s intluenclng the 6ign and magnilude of
the feedback effect can be unde:"stood. It irtl] be shown that the aeactoa
vas in a pa:.tlcula-1y unstabie s+,ale iordedialely p.io:- to the agcident.
42,2
The ope:.atin8 Pllnciple
of a the.mat Reacto.
The eleoent t!.anj.ue is found in naluae as a oixtrre oj" lsotopes Hith the
app.oxiEate p.opoations 99-3" U"., 0.7i U,'3. Iuclea. flsslon can orly be
induced in U"t by.eiativ€l.y iast mov:ng nelt:.ons Hith en€:-Eies oi aboLlt
1 MeV and upwa:.ds. The doFinant effect of Ur!. is the absoaptioa of
neut:^ona. On the othe. hand fissio, can be induced i.n Urrr by neutaons of
aLt eneagies ancl indeed lhe paocess is pa:"ticuiaaly e6sy to induce elth slow
lloving neut:'ons.
A the:'da.l.:.eacto. is desl.gnedto €xploit the above cha.actealstics
by
a.: enging foa the fast neutaoN eEitted tn fisslon to be sloeed doyn to an
ene!'8y rhe e the.e ls a sutficj.entiy hlgh p.obabllity of tnduclng suffi.cient
ner| iissions ln U"5 to paoducea seLf sustainlng chain !^eactlon. The
(ie
slot.ing dovn l.s p!"oduced by alloi.1rg the neut.ons to colltde elalticatly
to Eake bil11a--d baLl type collislons) ,ith the atoos ol a light eleoent in
a nediur! knourn as the ,,hocle.atoa'. This paocess t€ continued untlL the
neutaorls co&e lnto a state pheae thela ootlons a-e Ln app:oxlEate theaEal
equllibaiuD
rith
the atoEic notions of the at@s of the oode.ato..
neutaons a.e desc.ibed as ,ithe.6a: reut.onsr and tbeia p.obability
captFe
by U2r5 oust- be su:licien::.y hlgh:"elatlve
Such
of
to the charces of captl.ee