Chernobyl Accident 1986(Updated April 2015) The Chernobyl accident in 1986 was the result of a fawed reactor design that was operated with inadequately trained personnel The resulting stea! e"plosion and #res released at least $% of the radioacti&e reactor core into the at!osphere and downwind ' so!e $()) *+q (,-1.1 eq) Two Chernobyl plant wor/ers died on the night of the accident0 and a further (8 people died within a few wee/s as a result of acute radiation poisoning 123C4A5 says that apart fro! increased thyroid cancers0 6there is no e&idence of a !a7or public health i!pact attributable to radiation e"posure () years after the accident6 5esettle!ent of areas fro! which people were relocated is ongoing,n ()11 Chernobyl was o8cially declared a tourist attractionThe April 1986 disaster at the Chernobyla nuclear power plant in 1/rainewas the product of a fawed 3o&iet reactor design coupled with serious !ista/es !ade by the plant operatorsb ,t was a direct consequence of Cold 9ar isolation and the resulting lac/ of any safety cultureThe accident destroyed the Chernobyl : reactor0 /illing .) operators and #re!en within three !onths and se&eral further deaths later ;ne person was /illed i!!ediately and a second died in hospital soon after as a result ofin7uries recei&ed Another person is reported to ha&e died at the ti!e fro! a coronary thro!bosisc Acute radiation syndro!e (A53) was originally diagnosed in (.< people on-site and in&ol&ed with the clean-up and it was later con#r!ed in 1.: cases ;f these0 (8 people died as a result of A53 within a few wee/s of the accident 2ineteen !ore subsequently died between 198< and ()): but their deaths cannot necessarily be attributed to radiation e"posured 2obody o=-site su=ered fro! acute radiation e=ects although a large proportion of childhood thyroid cancers diagnosed since the accident is li/ely to be due to inta/e of radioacti&e iodine falloutd >urther!ore0 large areas of +elarus0 1/raine0 5ussiaand beyond were conta!inated in &arying degrees 3ee also sections below and Chernobyl Accident Appendi" (? @ealth ,!pactsThe Chernobyl disaster was a unique e&ent and the only accident in the history of co!!ercial nuclear power where radiation-related fatalities occurrede @owe&er0 the design of the reactor is unique and in that respect the accident is thus of little rele&ance to the rest of the nuclear industry outside the then 4astern +loc @owe&er0 it led to !a7or changes in safety culture and in industry cooperation0 particularly between 4ast and 9est before the end of the 3o&iet 1nion >or!er *resident Aorbache& said that theChernobyl accident was a !ore i!portant factor in the fall of the 3o&iet 1nion than *erestroi/a ' his progra! of liberal refor!The Chernobyl site and plantThe Chernobyl *ower Co!ple"0 lying about 1.) /! north of Bie&0 1/raine0 and about () /! south of the border with +elarus0 consisted of four nuclear reactors of the 5+CB-1))) design (see infor!ation page on 5+CB 5eactors)0 units 1 and ( being constructed between 19und0 set up in 199ollowing a !a7or earthqua/e0 a 1$-!etre tsuna!i disabled the power supply and cooling of three >u/ushi!a Daiichi reactors0 causinga nuclear accident on 11 Carch ()11 All three cores largely !elted in the #rst three days The accident was rated < on the ,243 scale0 due to high radioacti&e releases o&er days : to 60 e&entually a total of so!e 9:) *+q (,-1.1 eq) >our reactors were written o= due to da!age in the accident ' (riday 11 Carch ()11 did considerable da!age in the region0 and the large tsuna!i it created caused &ery !uch !ore The earthqua/e was centred 1.) /! o=shore the city of 3endai in Ciyagi prefecture on the eastern cost of @onshu,sland (the !ain part of Iapan)0 and was a rare and co!ple" double qua/e gi&ing a se&ere duration of about . !inutes An area of the seafoor e"tending 6$) /! north-south !o&ed typically 1)-() !etres horiEontally Iapan !o&ed a few !etres east and the local coastline subsided half a !etre The tsuna!i inundated about $6) sq /! and resulted in a hu!an death toll of o&er 190))) and !uch da!age to coastal ports and towns with o&er a !illion buildings destroyed or partly collapsed4le&en reactors at four nuclear power plants in the region were operating at the ti!e and all shut down auto!atically when the qua/e hit 3ubsequent inspection showed no signi#cant da!age to any fro! the earthqua/e The operating units which shut down were To/yo 4lectric *ower Co!panyGs (Tepco) >u/ushi!a Daiichi 10 (0 .0 and >u/ushi!a Daini 10 (0 .0 :0 Toho/uGs ;nagawa 10 (0 .0 and IapcoGs To/ai0 total 9.u/ushi!a Daiichi units :0 $ Q 6 were not operating at the ti!e0 but were a=ected The !ain proble! initially centred on >u/ushi!a Daiichi units 1-. 1nit : beca!e a proble! on day #&eThe reactors pro&ed robust seis!ically0 but &ulnerable to the tsuna!i *ower0fro! grid or bac/up generators0 was a&ailable to run the 5esidual @eat 5e!o&al (5@5) syste! cooling pu!ps at eight of the ele&en units0 and despite so!e proble!s they achie&ed Gcold shutdownG within about four days The other three0 at >u/ushi!a Daiichi0 lost power at .:( p!0 al!ost an hour after the qua/e0 when the entire site was fooded by the 1$-!etre tsuna!i This disabled 1( of 1. bac/-up generators on site and also the heat e"changers for du!ping reactor waste heat and decay heat to the sea The three units lost the ability to !aintain proper reactor cooling and water circulation functions 4lectrical switchgear was also disabled Thereafter0 !any wee/s of focused wor/ centred on restoring heat re!o&al fro! the reactors and coping with o&erheated spent fuel ponds This was underta/en by hundreds of Tepco e!ployees as well as so!e contractors0 supported by #re#ghting and !ilitary personnel 3o!e of the Tepco sta= had lost ho!es0 and e&en fa!ilies0 in the tsuna!i0 and were initially li&ing in te!porary acco!!odation under great di8culties and pri&ation0 with so!e personal ris/ A hardened e!ergency response centre on site was unable to be used in grappling with the situation due to radioacti&e conta!inationThree Tepco e!ployees at the Daiichi and Daini plants were /illed directly by the earthqua/e and tsuna!i0 but there ha&e been no fatalities fro! the nuclear accidentA!ong hundreds of aftershoc/s0 an earthqua/e with !agnitude u/ushi!a than the 11 Carch one0 was e"perienced on < April0 but without further da!age to the plant ;n 11 April a !agnitude u/ushi!a-@a!adori0 caused no further proble!sThe two >u/ushi!a plants and their sitingThe Daiichi (#rst) and Daini (second) >u/ushi!a plants are sited about 11 /!apart on the coast0 Daini to the southThe recorded seis!ic data for both plants ' so!e 18) /! fro! the epicentre ' shows that $$) Aal ()$6 g) was the !a"i!u! ground acceleration for Daiichi0 and ($: Aal was !a"i!u! for Daini Daiichi units (0 . and $ e"ceeded their !a"i!u! response acceleration design basis in 4-9 directionby about ()% The recording was o&er 1.)-1$) seconds (All nuclear plants in Iapan are built on roc/ ' ground acceleration was around ())) Aal a few /ilo!etres north0 on sedi!ents)The original design basis tsuna!i height was .1 ! for Daiichi based on assess!ent of the 196) Chile tsuna!i and so the plant had been built about 1) !etres abo&e sea le&el with the seawater pu!ps : ! abo&e sea le&el The Daini plant was built 1. !etres abo&e sea le&el ,n ())( the design basiswas re&ised to $< !etres abo&e0 and the seawater pu!ps were sealed Tsuna!i heights co!ing ashore were about 1$ !etres0 and the Daiichi turbine halls were under so!e $ !etres of seawater until le&els subsided Daini was less a=ected The !a"i!u! a!plitude of this tsuna!i was (. !etres at point of origin0 about 18) /! fro! >u/ushi!a,n the last century there ha&e been eight tsuna!is in the region with !a"i!u! a!plitudes at origin abo&e 1) !etres (so!e !uch !ore)0 these ha&ing arisen fro! earthqua/es of !agnitude u/ushi!a prefectures"See al)o bac/$round on Earth0ua/e) and Sei)!ic (rotection for Nuclear (ower (lant) in .apan'4&ents at >u/ushi!a Daiichi 1-. Q :,t appears that no serious da!age was done to the reactors by the earthqua/e0 and the operating units 1-. were auto!atically shut down in response to it0 as designed At the sa!e ti!e all si" e"ternal power supply sources were lost due to earthqua/e da!age0 so the e!ergency diesel generators located in the base!ents of the turbine buildings started up ,nitially cooling would ha&e been !aintained through the !ain stea! circuit bypassing the turbine and going through the condensersThen :1 !inutes later0 at .?:( p!0 the #rst tsuna!i wa&e hit0 followed by a second 8 !inutes later These sub!erged and da!aged the seawater pu!psfor both the !ain condenser circuits and the au"iliary cooling circuits0 notably the 5esidual @eat 5e!o&al (5@5) cooling syste! They also drownedthe diesel generators and inundated the electrical switchgear and batteries0 all located in the base!ents of the turbine buildings (the one sur&i&ing air-cooled generator was ser&ing units $ Q 6) 3o there was a station blac/out0 and the reactors were isolated fro! their ulti!ate heat sin/ The tsuna!is also da!aged and obstructed roads0 !a/ing outside access di8cultAll this put those reactors 1-. in a dire situation and led the authorities to order0 and subsequently e"tend0 an e&acuation while engineers wor/ed to restore power and cooling The 1($-&olt DC batteries for units 1 Q ( were fooded and failed0 lea&ing the! without instru!entation0 control or lighting 1nit . had battery power for about .) hoursAt riday 11 Carch a 2uclear 4!ergency was declared0 and at 8$)p! the >u/ushi!a *refecture issued an e&acuation order for people within ( /! of the plant At 9(. p! the *ri!e Cinister e"tended this to . /!0 and at $:: a! on 1(th he e"tended it to 1) /! @e &isited the plant soon after ;n 3aturday 1(th he e"tended the e&acuation Eone to () /!,nside the >u/ushi!a Daiichi reactorsThe >u/ushi!a Daiichi reactors are A4 boiling water reactors (+95) of an early (196)s) design supplied by A40 Toshiba and @itachi0 with what is /nownas a Car/ , contain!ent 5eactors 1-. ca!e into co!!ercial operation 19uel ponds? de&eloping proble!s1sed fuel needs to be cooled and shielded This is initially by water0 in pondsAfter about three years under water0 used fuel can be transferred to dry storage0 with air &entilation si!ply by con&ection 1sed fuel generates heat0 so the water is circulated by electric pu!ps through e"ternal heat e"changers0 so that the heat is du!ped and a low te!perature !aintained There are fuel ponds near the top of all si" reactor buildings at the Daiichi plant0 ad7acent to the top of each reactor so that the fuel can be unloaded under water when the top is o= the reactor pressure &essel and it is fooded The ponds hold so!e fresh fuel and so!e used fuel0 pending its transfer to the central usedLspent fuel storage on site (There is so!e dry storage on site to e"tend the plantGs capacity)At the ti!e of the accident0 in addition to a large nu!ber of used fuel asse!blies0 unit :Gs pond also held a full core load of $:8 fuel asse!blies while the reactor was undergoing !aintenance0 these ha&ing been re!o&ed at the end of 2o&e!berA separate set of proble!s arose as the fuel ponds0 holding fresh and used fuel in the upper part of the reactor structures0 were found to be depleted in water The pri!ary cause of the low water le&els was loss of cooling circulation to e"ternal heat e"changers0 leading to ele&ated te!peratures and probably boiling0 especially in hea&ily-loaded unit : @ere the fuel would ha&e been unco&ered in about < days due to water boiling o= @owe&er0 the fact that unit : was unloaded !eant that there was a large in&entory of water at the top of the structure0 and enough of this replenished the fuel pond to pre&ent the fuel beco!ing unco&ered ' the !ini!u! le&el reached was about 1( ! abo&e the fuel on about (( AprilAfter the hydrogen e"plosion in unit : early on Tuesday 1$ Carch0 Tepco was told to i!ple!ent in7ection of water to unit : pond which had a particularly high heat load (. C9) fro! 1..1 used fuel asse!blies in it0 so it was the !ain focus of concern ,t needed the addition of about 1)) !.Lday to replenish it after circulation ceased>ro! Tuesday 1$ Carch attention was gi&en to replenishing the water in the ponds of units 10 (0 . as well ,nitially this was atte!pted with #re pu!ps butfro! (( Carch a concrete pu!p with $8-!etre boo! enabled !ore precise targeting of water through the da!aged walls of the ser&ice foors There was so!e use of built-in plu!bing for unit ( Analysis of radionuclides in water fro! the used fuel ponds suggested that so!e of the fuel asse!blies !ight be da!aged0 but the !a7ority were intactThere was concern about structural strength of unit : building0 so support forthe pond was reinforced by the end of Iuly2ew cooling circuits with heat e"changers ad7acent to the reactor buildings for all four ponds were co!!issioned after a few !onths0 and each reduced the pool te!perature fro! uel asse!blies are now being re!o&ed fro! unit : pool"See al)o bac/$round on >u/ushi!a >uel *onds and Deco!!issioning section below)5adioacti&e releases to air5egarding releases to air and also water lea/age fro! >u/ushi!a0 the !ain radionuclide fro! a!ong the !any /inds of #ssion products in the fuel was &olatile iodine-1.10 which has a half-life of 8 days The other !ain radionuclide is caesiu!-1.urther ,-1.1 and Cs-1.< and Cs-1.: were apparently released during the following few days0 particularly following the hydrogen e"plosion at unit . on 1:th and in unit : on 1$th Considerable a!ounts of "enon-1.. and iodine-1.1 were &ented0 but !ost of the caesiu!-1.< (1: out of 1$ *+q total) along with !ost of the Cs-1.: apparently ca!e fro! unit ( on or after the 1$th ' the only one of the four units which did not su=er a hydrogen e"plosion de!olishing its superstructure Also ten ti!es !ore iodine is attributed to unit ( than unit 10 while unit . produced half as !uch as unit 1 @owe&er0 there re!ains so!e uncertainty about the e"act sources and ti!ings of the radioacti&e releases;n 16 Carch0 IapanRs 2uclear 3afety Co!!ission reco!!ended local authorities to instruct e&acuees under :) years of age lea&ing the () /! Eone to ingest stable iodine as a precaution against ingestion (eg &ia !il/) of radioacti&e iodine-1.1 The pills and syrup (for children) had been pre-positioned at e&acuation centers The order reco!!ended ta/ing a single dose0 with an a!ount dependent on age @owe&er0 it is not clear that this was i!ple!ented ;n 11 April the go&ern!ent suggested that those outside the ()/! Eone who were li/ely to accu!ulate () !3& total dose should !o&e out within a !onth Data at the end of Cay (with !ost ,-1.1 gone by decay) showed that about half of the () /! e&acuation Eone and a si!ilar area to the 290 total about 1))) sq /!0 would gi&e an annual dose of () !3& to Carch ()1(>ranceGs ,nstitute for 5adiological *rotection Q 2uclear 3afety (,532) esti!ated that !a"i!u! e"ternal doses to people li&ing around the plant were unli/ely to e"ceed .) !3&Lyr in the #rst year This was based on airborne !easure!ents between .) Carch and : April0 and appears to be con#r!ed by the abo&e #gures ,t co!pares with natural bac/ground le&els !ostly (-. !3&Lyr0 but ranging up to $) !3&Lyr elswhereThe !ain concentration of radioacti&e pollution stretches northwest fro! the plant0 and le&els of Cs-1.< reached o&er . C+qL!( in soil here0 out to .$/! away ,n !id-Cay about 1$0))) residents in a conta!inated area ()-:) /! northwest of the plant were e&acuated0 !a/ing a total of o&er 1))0))) displaced personsThe ,A4A reported on 19 Carch that airborne radiation le&els had spi/ed three ti!es since the earthqua/e0 notably early on 1$th (:)) !3&Lhr near unit .)0 but had stabiliEed since 16th at le&els signi#cantly higher than the nor!al le&els0 but within the range that allows wor/ers to continue on-site reco&ery !easures2,3A esti!ated that about 1.) *+q of iodine-1.1 was released fro! the reactors0 !ostly around 1$ Carch and the two days following ' )16% of the total in&entory ,n .( days this released iodine would ha&e di!inished to one si"teenth of original acti&ity ' 8 *+q 2,3AGs report to ,A4A said that this 1.) *+q of ,-1.1 together with 6 *+q of caesiu!-1.u/ushi!a prefecture pro&ided a further report early in ()1: which said that the ]indirectR deaths in the prefecture were greater than the nu!ber (16)u/ushi!a accident (Cainichi 1L11L1.)3u!!ary? Cany e&acuated people re!ain unable to fully return ho!e due togo&ern!ent-!andated restrictions based on conser&ati&e radiation e"posurecriteria @owe&er0 o&er 1))) pre!ature deaths ha&e been caused by !aintaining the e&acuation beyond a prudent wee/ or so Deconta!ination wor/ is proceeding while radiation le&els decline naturally The ;ctober ()1. ,A4A report !a/es it clear that !any e&acuees should be allowed to return ho!eA 7ournalist article is in line with 92AGs understanding of the situation in ()1$Canaging conta!inated water5e!o&ing conta!inated water fro! the reactor and turbine buildings had beco!e the !ain challenge in wee/ .0 along with conta!inated water in trenches carrying cabling and pipewor/ This was both fro! the tsuna!i inundation and lea/age fro! reactors 5un-o= fro! the site into the sea was also carrying radionuclides well in e"cess of allowable le&els +y the end of Carch all storages around the four units ' basically the !ain condenser units and condensate tan/s ' were largely full of conta!inated water pu!ped fro! the buildings 3o!e 1))) storage tan/s were set up progressi&ely0 including initially .$) steel tan/s with rubber sea!s0 each holding 1()) !. A few of these de&eloped lea/s in ()1.Accordingly0 with go&ern!ent appro&al0 Tepco o&er :-1) April released to thesea about 1)0:)) cubic !etres of slightly conta!inated water ()1$ T+q total) in order to free up storage for !ore highly-conta!inated water fro! unit ( reactor and turbine buildings which needed to be re!o&ed to !a/e safe wor/ing conditions 1nit ( is the !ain source of conta!inated water0 though so!e of it co!es fro! drainage pits 2,3A con#r!ed that there was no signi#cant change in radioacti&ity le&els in the sea as a result of the )1$ T+q dischargeTepco then began transferring highly-radioacti&e water fro! the base!ent ofunit ( turbine hall and cabling trench to the holding tan/ and waste treat!ent plant 7ust south of unit : The water contained . T+qL!. of ,-1.1 and 1. T+qL!. of Cs-1.< 3o!e 1() !.Lday of fresh water was being in7ected into unit ( reactor core and this replenished the conta!inated waterbeing re!o&ed0 as in the other unitsTepco built a new wastewater treat!ent facility to treat conta!inated water The co!pany used both 13 proprietary adsorbtion and >rench con&entional technologies in the new 1()) !.Lday treat!ent plant A supple!entary and si!pler 3A55S plant to re!o&e caesiu! using Iapanese technology and !ade by Toshiba and 3haw Aroup was installed and co!!issioned in August ()11 These plants reduce caesiu! fro! about $$ C+qLJ to $$ /+qLJ ' about ten ti!es better than designed Desalination is necessary on account of the seawater earlier used for cooling0 and the 1()) !.Lday desalination plant produces :8) !. of clean water while orce considering the options,n ()1: a new Burion strontiu! re!o&al syste! was co!!issioned This is !obile and can be !o&ed around the tan/ groups to further clean up water which has been treated by AJ*3About .)) of the 9.) storage tan/s are built fro! fanged steel panels with rubber seals0 and one of these lea/ed signi#cantly in !id-()1. At the end of Cay ()1$0 1)8 !.Lday of clean water was being circulated through each reactor (1-.) Collected water fro! the!0 with high radioacti&ity le&els0 was being treated and re-used The cu!ulati&e treated &olu!e was then 1(.( !illion cubic !etres ,n storage on site was ::(0 in&ol&e!entThe ,nternational 5esearch ,nstitute for 2uclear Deco!!issioning (,5,D) was set up in August ()1. Iapan by IA4A0 Iapanese utilities and reactor &endors0 with a focus on >u/ushi!a 1-:,n 3epte!ber ()1. ,5,D called for sub!issions on the !anage!ent of conta!inated water at >u/ushi!a ,n particular0 proposals were sought for dealing with? the accu!ulation of conta!inated water (in storage tan/s0 etc)Kthe treat!ent of conta!inated water including tritiu! re!o&alK the re!o&al of radioacti&e !aterials fro! the seawater in the plantGs .) ha harbourK the !anage!ent of conta!inated water inside the buildingsK !easures to bloc/ groundwater fro! fowing into the siteK and0 understanding the fow of groundwater 5esponses were sub!itted to the go&ern!ent in 2o&e!ber,n Dece!ber ()1. ,5,D called for inno&ati&e proposals for re!o&ing fuel debris fro! units 1-. about ()(),n August ()1: the 2uclear Da!age Co!pensation and Deco!!issioning >acilitation Corporation (2D>) was set up by go&ern!ent as a planning body with !anage!ent support for 5QD pro7ects0 ta/ing o&er ,5,DRs planning role ,t will wor/ closely with ,5,D0 whose focus now is on de&eloping !id- and long-ter! deco!!issioning technologies 2D> will also wor/ closely with Tepco >u/ushi!a Daiichi DQD 4ngineering Co which has responsibility for operating the actual deco!!issioning wor/ there The 2D> will be the !ain body interacting with go&ern!ent (C4T,) to i!ple!ent policy>u/ushi!a Daiichi $Q61nits $ Q 60 in a separate building0 also lost power on 11 Carch due to the tsuna!i They were in Gcold shutdownG at the ti!e0 but still requiring pu!pedcooling ;ne air-cooled diesel generator at Daiichi 6 was located higher and so sur&i&ed the tsuna!i and enabled repairs on 3aturday 19th0 allowing full restoration of cooling for units $ and 6 9hile the power was o= their core te!perature had risen to o&er 1))XC (1(8XC in unit $) under pressure0 and they had been cooled with nor!al water in7ection They were restored to coldshutdown by the nor!al recirculating syste! on ()th0 and !ains power was restored on (1-((nd,n 3epte!ber ()1. Tepco co!!enced wor/ to re!o&e the fuel fro! unit 6 *ri!e Cinister Abe then called for Tepco to deco!!ission both units Tepco announced in Dece!ber ()1. that it would deco!!ission both units fro! the end of 7anuary ()1: 1nit $ is a u/ushi!a site The ()1. Iapan trade de#cit was I*S 11$ trillion,nquiries and reports? the accident itself and deco!!issioning,n ;ctober ()1: the 25A published its Analy)i) of the 4E(CO 1u/u)hi!a Daiichi N(S Accident0 ,nteri! 5eport A pro&isional translation in 4nglish was published in >ebruary ()1$ This focuses on a nu!ber of questions which re!ained une"plained in the ()1( 2ational Diet ,n&estigation Co!!ission reportA nu!ber of earlier reports were published in ()11-1(?,n Cay ()11 a tea! of 18 e"perts fro! 1( countries spent a wee/ at the plant on behalf of the ,nternational Ato!ic 4nergy Agency (,A4A)0 and its #nal report was presented to the ,A4A Cinisterial Conference in Fienna in Iune4arly in Iune ()11 the independent ,n&estigation Co!!ittee on the Accident at the >u/ushi!a 2uclear *ower 3tations (,CA2*3)0 a panel of ten e"perts0 !ostly acade!ics and appointed by the Iapanese cabinet0 began !eeting ,t has two technological ad&isers An initial report was published in Dece!ber ()11 and a #nal report in Iuly ()1( The panel set up four tea!s to underta/e in&estigations on the causes of the accident and ensuing da!age and on !easures to pre&ent the further spread of da!age caused by the accident0 but not to pursue the question of responsibility for the accidentThe national Diet later set up a legally-constituted 2uclear Accident ,ndependent ,n&estigation Co!!ission (2A,,C0 or 2ational Diet ,n&estigation Co!!ission) of ten !e!bers which started its wor/ in Dece!ber ()11 ;ne of the purposes of 2A,,C is to pro&ide suggestions including the Tre-e"a!ination of an opti!al ad!inistrati&e organiEationU for nuclear safety regulation based on its in&estigation of the accident 2A,,C reported in Iuly ()1(0 harshly criticiEing the go&ern!ent0 the plant operator and the countryRs national culture After conducting 9)) hours of public hearings and inter&iews with !ore than 101)) people and &isiting se&eral nuclear power plants0 the co!!issionRs report concluded that the accident was a T!an!ade disaster0U the result of Tcollusion between the go&ern!ent0 the regulators and To/yo 4lectric *ower CoU ,t said the Troot causes were the organiEational and regulatory syste!s that supported faulty rationales for decisions and actionsU The 2A,,C criticiEed the regulator for insu8ciently !aintaining independence fro! the industry in de&eloping and enforcing safety regulations0 the go&ern!ent for inadequate e!ergency preparedness and !anage!ent0 and Tepco for its poor go&ernance and lac/ of safety culture The report called for funda!ental changes across the industry0 including the go&ern!ent and regulators0 to increase openness0 trustworthiness and focus on protecting public health and safetyThe 2A,,C Chair!an wrote? 69hat !ust be ad!itted ' &ery painfully ' is that this was a disaster GCade in IapanG ,ts funda!ental causes are to be found inthe ingrained con&entions of Iapanese culture? our refe"i&e obedienceK our reluctance to question authorityK our de&otion to Gstic/ing with the progra!GK our groupis!K and our insularityU The !indset of go&ern!ent and industry led the country to a&oid learning the lessons of the pre&ious !a7or nuclear accidents at Three Cile ,sland and Chernobyl 6The consequences of negligence at >u/ushi!a stand out as catastrophic0 but the !indset that supported it can be found across Iapan ,n recogniEing that fact0 each of us (e&ery Iapanese citiEen) should refect on our responsibility as indi&iduals in a de!ocratic society62A,,C reported that Tepco had been aware since ())6 that >u/ushui!a Daiichi could face a station blac/out if fooded0 as well as the potential loss ofulti!ate heat sin/ in the e&ent of a !a7or tsuna!i @owe&er0 the regulator0 2,3A0 ga&e no instruction to the co!pany to prepare for se&ere fooding0 and e&en told all nuclear operators that it was not necessary to plan for station blac/out During the initial response to the tsuna!i0 this lac/ of readiness forstation blac/out was co!pounded by a lac/ of planning and training for se&ere accident !itigation *lans and procedures for &enting and !anual operation of e!ergency cooling were inco!plete and their i!ple!entation ine!ergency circu!stances pro&ed &ery di8cult as a result 2,3A was also criticised for its 6negligence and failure o&er the years6 to prepare for a nuclear accident in ter!s of public infor!ation and e&acuation0 with pre&iousgo&ern!ents equally culpable Then TepcoRs di8culty in !itigation was co!pounded by go&ern!ent interference which under!ined 2,3A;n < Iune ()11 the go&ern!ent sub!itted a u/ushi!a Daiichi 2uclear *ower 3tation0 with ti!eline This 9u/ushi!a0 the serious accident would not ha&e happened0 underlining the need for greater international regulatory collaboration,n April ()1( the 13 4lectric *ower 5esearch ,nstitute (4*5,) published 1u/u)hi!a Daiichi Accident 5 4echnical Cau)al 1actor Analy)i)0 which identi#ed the root cause beyond the fooding and its e=ects as a failure to consider the possibility of the rupture of co!binations of geological fault seg!ents in the &icinity of the plant,n >ebruary ()1$ the ,A4A co!pleted its third re&iew !ission (as follow-up tothat of late ()1.0 and in&ol&ing so!e 18) e"perts fro! :( ,A4A !e!ber states and other organiEations o&er two years) and reported on deco!!issioning to C4T, ,n Cay ()1$ its #nal report was deli&ered to !e!ber states0 to be published in 3epte!ber ,t was broadly positi&e regarding progress since ()1.0 but said that so!e challenging issues re!ain,t contained ad&isory points on topics such as long-ter! radioacti&e waste !anage!ent0 !easures concerning conta!inated water0 and issues related to the re!o&al of used fuel and fuel debris,nquiries and reports? radiation e=ectsA preli!inary report fro! the 9orld @ealth ;rganisation (9@;) in Cay ()1( esti!ated the radiation doses that residents of Iapan outside the e&acuated areas recei&ed in the year following the accident The reportGs headline conclusion is that !ost people in >u/ushi!a prefecture would ha&e recei&ed a radiation dose of between 1 and 1) !3& during the #rst year after the accident This co!pares with le&els of about (: !3& they would ha&e recei&ed fro! una&oidable natural sources ,n two places the doses were higher ' between 1) and $) !3&0 still below any har!ful le&el Al!ost all were Tbelow the internationally-agreed reference le&el for the public e"posure due to radon in dwellingsU (about 1) !3&Lyr)The 12 3cienti#c Co!!ittee on the 4=ects of Ato!ic 5adiation (123C4A5) inCay ()1( reported that despite s/in conta!ination of se&eral wor/ers0 no clinically-obser&able e=ects ha&e been reported and there is no e&idence of acute radiation in7ury in any of the ()011$ wor/ers who participated in TepcoRs e=orts to !itigate the accident at the plant 4ighteen 123C4A5 !e!ber states pro&ided u/ushi!a are e"pected on a&erage to recei&e less than 1) !3& due to the accident o&er their whole lifeti!e0 co!pared with the 1u/ushi!aGs before they restart following any shutdown0 including for routine chec/s These were in two stages0 and are described in the Iapan paperThe go&ern!ent then created a separate 2uclear 5egulatory Agency (25A) under the authority of the 4n&iron!ent Cinistry and co!bining the roles of 2,3A and 23C0 co!!issioned in 3epte!ber ()1( A new 2uclear 5egulatory Co!!ission (25C) replaced the 23C and will re&iew the e=ecti&eness of the 25A and be responsible for the in&estigation of nuclear accidents