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Fukushima tidslinje: Hvordan et jordskælv udløste Japans atomkatastrofe i 2011

Fukushima tidslinje: Hvordan et jordskælv udløste Japans atomkatastrofe i 2011



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Katastrofen i 2011 ved atomkraftværket Fukushima Daiichi var den værste atomhændelse siden nedsmeltningen i Tjernobyl i det tidligere Sovjetunionen 25 år før.

Det startede med et jordskælv. Det resulterede i 465.000 evakueringer, 360 milliarder dollars i økonomiske tab og øgede strålingsniveauer i Tokyo, 140 miles væk.

Som med de fleste katastrofer måtte flere ting gå galt for at få et så katastrofalt resultat. Nedenfor er en detaljeret redegørelse for hvordan ødelæggelserne udviklede sig.

11. marts 2011: Et jordskælv udfælder krise

14:46: Den vestvendte stillehavsplade, en oceanisk tektonisk plade, siver nedad under den nordamerikanske plade og forårsager et jordskælv 43 miles ud for den nordøstlige kyst af Honshu, Japans mest folkerige ø. Jordskælvet har en styrke på 9,1, hvilket gør det til det største jordskælv i Japans historie-og et af de fem mest kraftfulde jordskælv, der er registreret på verdensplan siden den moderne journalføring begyndte.

15:27: Jordskælvet udløser en tsunami. Den første bølge ankommer til Fukushima Daiichi atomkraftværket i form af en 13 fod høj bølge, som afbøjes af en havmur bygget til at modstå bølger op til 33 fod høje.

15.35: En anden bølge, denne over 50 fod høj, bryder væggen. Det ødelægger havvandspumper, drukner kraftpaneler, der distribuerer energi til vandpumper, og stiger til kældre, hvor backupgeneratorer er anbragt. I fem af de seks reaktorer går AC -strøm tabt; uden strøm kan vandpumper ikke levere den konstante strøm af koldt vand til reaktorernes intens varme kerner. Uden den regelmæssige strøm af kølevand følger der uundgåeligt en nedsmeltning.

LÆS MERE: Tjernobyl -tidslinjen: Hvordan en atomulykke eskalerede til en historisk katastrofe

15.37: Da oversvømmelser har ødelagt generatorens backupbatterier, mister enhed 1 også jævnstrøm. Kontrolrummet for enhed 1 og 2 bliver mørkt og fratager kraftværksoperatører enhver kapacitet til at overvåge de to reaktorer.

Lige inden klokken 18: Et arbejdshold går til 4. sal i enhed 1 -reaktorbygningen uden beskyttelsesbeklædning. Deres dosimetre aflæser strålingsniveauer uden for skalaen, hvilket indikerer, at kernen i enhed 1 er udsat, og dens brændstofstænger er sprængt.

19:03: Statsminister Naoto Kan erklærer en nuklear nødsituation.

21.00: Den japanske regering udsteder evakueringsordrer til de flere tusinde indbyggere, der bor inden for en radius af 3 kilometer fra kraftværket.

12. marts: Evakueringsområde udvides, taget blæser

Kort før kl. 6: Premierminister Kan beslutter at tage til Fukushima. Han beordrer myndighederne til at udvide evakueringszonen til 10 kilometer. Med tabet af kølevæske bygger temperatur og tryk inde i reaktorerne.

10:09: Tokyo Electric Power Company (TEPCO) meddeler, at de har udluftet noget damp fra enhed 1 i et forsøg på at sænke temperaturen og trykket. Udluftningen betyder, at noget radioaktivt materiale er frigivet til luften.

10:58: Enhed 2, det meddeles, er ligeledes blevet ventileret.

15:36: En brinteksplosion blæser taget af enhed 1, sammenfalder betonvægge og efterlader kun stålrammen. Fire arbejdere er såret i eksplosionen. Ud over skaden på arbejderne skader eksplosionen det elektriske kabel, som arbejderne havde lagt med henblik på at genoprette strømmen til enhed 1 og 2. Eksplosionen beskadiger også brandslanger, som arbejderne havde arrangeret, hvilket hæmmer anlæggets evne til at levere kølevæske til reaktorkernen.

Lige før 18.30: Evakueringsområdet udvides til en radius på 20 km.

20:20: TEPCO begynder at injicere havvand i enhed 1 som et erstatnings -kølevæske. Beslutningen om at bruge havvand er dødsstødet for Reactor 1: I modsætning til ferskvand korroderer det uopretteligt pumper og rørledninger. Omtrent på samme tid registrerer Japans Nuclear and Industrial Safety Agency (NISA) skadelige strålingsniveauer af cæsium 137 og jod 131 nær anlægget.

LÆS MERE: Tjernobyl -coverup: Hvordan embedsmænd ødelagde evakuering af en bestrålet by

13. marts

6:23: En NISA -embedsmand meddeler, at nødkølesystemet i Unit 3 -reaktoren er slået fejl.

22:05: TEPCO begynder at injicere havvand i enhed 3.

22:09: TEPCO annoncerer en plan om at injicere havvand i enhed 2, den første nødsituation ved denne reaktor.

14. marts: Eksplosioner fortsætter

11:01: Der er en brinteksplosion ved Unit 3 -reaktoren. 11 arbejdere er såret, og bygningens struktur er alvorligt beskadiget.

15. marts

6:14: Der opstår en brinteksplosion i Unit 2 -reaktoren.

I løbet af dagen: Havvandspumpning fortsætter ved enhed 1, 2 og 3. I nærheden af ​​anlægget måles strålingsniveauerne til 400 millisievert i timen. Til sammenligning udsættes den gennemsnitlige person for omkring 2,4 millisievert stråling om året, hvilket betyder, at strålingen i Fukushima er 1,46 millioner gange stærkere, end den ville være i et gennemsnitligt miljø.

17. marts

Militæret begynder at bruge helikoptere til at dumpe havvand på enhed 3, hvor strålingsniveauerne er på 17 millisievert i timen.

19. marts

Udskiftning af dieselgeneratorer implementeres med succes på enhed 5 og 6 og pumper vand tilbage i disse reaktorkerner. Andre steder bliver omfanget af skader tydeligere: Mælk og vand i det større Fukushima -præfektur viser for høje niveauer af radioaktivt jod.

LÆS MERE: Tjernobyl: 7 mennesker, der spillede en afgørende rolle i verdens værste atomkatastrofe

20. marts: Tingene begynder at stabilisere sig

Temperaturerne stabiliseres på enhed 5 og 6, hvilket medfører en sikker havn under "kolde nedlukningsforhold". Elektrisk strøm er genoprettet til enhed 2.

22. marts

Elleve dage efter den første katastrofe genoprettes elektrisk strøm til kontrolrum i enhed 1 og 2. I spildevandet lige syd for anlægget måles radioaktivt jod til 126,7 gange højere end den lovlige grænse.

25. marts

Enhed 1 -reaktortemperaturen sænkes til 204,5 grader Celsius, sikkert inden for dens designgrænser. Den japanske regering råder de beboere, der er mellem 20 og 30 kilometer væk fra fabrikken, til frivilligt at evakuere området.

LÆS MERE: Hvordan Three Mile Island -ulykken blev gjort endnu værre af en kaotisk reaktion

26. marts

Havvand, der er testet nær anlægget, har 1.250 gange den lovlige grænse for jod 131.

11. april

Et nyt jordskælv med en styrke på 7,0 rammer det østlige Japan. I 50 minutter mister Fukushima strømmen og forhindrer kølevand i at nå enhed 1, 2 og 3.

12. april: Atomic Disaster Declaration

Det Internationale Atomenergiorganisation vurderer Fukushima -krisen til en katastrofe på 7, den højeste af deres skala.

11. maj

Evakuerede, der har forladt hjem inden for 20 kilometer fra Fukushima, får to timer til at vende tilbage til vigtige dokumenter eller ejendele, der er efterladt i den første hast med deres evakuering.

2. februar 2012

Næsten et år efter katastrofen annoncerer landsbyen Kawauchi - en af ​​ni evakuerede kommuner mindre end 20 kilometer fra fabrikken - planer om genåbning til foråret.


Hvordan går det med oprydningen?

Ti år senere forbliver flere byer i det nordøstlige Japan uden for grænser. Myndighederne arbejder på at rydde op i området, så beboerne kan vende tilbage.

Store udfordringer er tilbage. Titusinder af arbejdere vil være nødvendige i løbet af de næste 30 til 40 år for sikkert at fjerne atomaffald, brændstofstænger og mere end en million tons radioaktivt vand, der stadig opbevares på stedet.

Men nogle beboere har besluttet aldrig at vende tilbage, fordi de frygter stråling, har bygget nye liv andre steder eller ikke vil tilbage til det sted, hvor katastrofen ramte.

Medierapporter i 2020 sagde, at regeringen kunne begynde at frigive vandet - filtreret for at reducere radioaktivitet - i Stillehavet allerede næste år.

Nogle forskere mener, at det enorme hav ville fortynde vandet, og at det ville udgøre en lav risiko for menneskers og dyrs sundhed. Miljøgruppen Greenpeace sagde imidlertid, at vandet indeholder materialer, der potentielt kan skade menneskeligt DNA.

Tjenestemænd har sagt, at der ikke er taget en endelig beslutning om, hvad de skal gøre med væsken.


Tidslinje for Japan's jordskælv, tsunami og atomkatastrofe i 2011

TOKYO (AP) - Torsdag markerer 10 -året for et massivt jordskælv, en tsunami og en atomkatastrofe, der ramte Japans nordøstlige kyst. Her er en tidslinje over begivenhederne:

- 11. marts 2011: Et jordskælv med en styrke på 9,0 rammer kysten klokken 14.46 og udløser en tårnhøj tsunami, der når land inden for en halv time. Tsunamien smadrer ind i atomkraftværket Fukushima Daiichi, ødelægger dets kraft- og kølesystemer og udløser nedsmeltninger ved tre reaktorer.

- 12. marts: En brinteksplosion sker ved anlæggets reaktor nr. 1 og sender stråling ud i luften. Beboere inden for en radius på 20 kilometer beordres til at evakuere. Lignende eksplosioner sker i to andre reaktorer i løbet af de følgende dage.

- 12. april: Japan hæver ulykken til kategori 7, det højeste niveau på den internationale nukleare og radiologiske begivenhedsskala, fra en tidligere 5, baseret på stråling frigivet til atmosfæren.

-24. april: Regeringen udpeger en eksklusionszone på 2 kilometer (1,25 kilometer) omkring atomkraftværket, der spænder over ni kommuner.

- 16. december: Efter at arbejdere i flere måneder kæmpede med at stabilisere anlægget, erklærer Japan en "kold nedlukning" med kernetemperaturer og pres ned til et niveau, hvor atomkædereaktioner ikke forekommer.

-23. juli 2012: En uafhængig undersøgelse, der er udpeget af en regering, konkluderer, at atomulykken var forårsaget af mangel på tilstrækkelig sikkerhed og krisestyring fra fabriksoperatøren, Tokyo Electric Power Co., slap overvågning af nukleare tilsynsmyndigheder og samarbejde.

- 1. april 2014: Evakueringsordren lempes for en by vest for det ødelagte atomkraftværk. Dele af mindst otte andre kommuner får lov til at genåbne i løbet af de næste tre år, selvom antallet af tilbagevendte stadig er lavt på grund af mangel på job og langvarige strålingsproblemer.

-22. december: TEPCO fuldender fjernelsen af ​​alle brugte nukleare brændstofstænger fra reaktorkølingens pool nr. 4, en indledende milepæl i anlæggets årtier lange nedlukning.

-2015-2019: Små robotter udstyret med kameraer og sensorer sendes ind i de beskadigede reaktorer, men giver kun begrænset udsigt over det meget radioaktive smeltede brændstofrester. Det gør planerne for fjernelse vanskeligere.

- 10. februar 2020: Et regeringspanel anbefaler kontrolleret udsætning i havet af hurtigt stigende mængder lækket radioaktivt kølevand på Fukushima -anlægget. TEPCO siger, at dets lagerkapacitet på 1,37 millioner tons vil være fuld i efteråret 2022.

- 10. december: Politiet siger, at dødstallet fra katastrofen, hovedsageligt fra tsunamien, når 18.426, heraf 2.527, hvis rester ikke er fundet.

- 13. februar 2021: Et jordskælv med en styrke på 7,3 rammer ud for Fukushima -kysten og efterlader en død og sårede mere end 180 mennesker. Det forårsager mindre skader på atomkraftværket.

-6. marts: Statsminister Yoshihide Suga besøger Fukushima og lover at fremskynde dekontamineringsindsatsen, så alle resterende forbudte zoner kan genåbnes, men giver ikke en tidsramme.


Jordskælv og tsunami i Japan: Tidslinje

(CNN) -Her er et minut-for-minut kig på det ødelæggende jordskælv og tsunami, der ramte Japan fredag ​​og efterfølgende bekymringer over skader på atomkraftværker. (Alle tider og datoer er lokal japansk tid).

Størrelse 8,9 jordskælv 231 miles nordøst for Tokyo, Japan i en dybde på 15,2 miles.

Jordskælvet er femte største i verden (siden 1900) og det største jordskælv, der nogensinde har ramt Japan.

Pacific Tsunami Warning Center udsender tsunamivarsel for Stillehavet fra Japan til den amerikanske vestkyst. Tsunami -advarsler lyder i mere end 50 lande og territorier. .

Inden for en time efter jordskælvet skyller en mur af vand op til 30 fod høje over den japanske kyst.

Biler, både og tog er fejet væk. Bygninger kollapser. Veje og motorveje er afskåret. Brande bryder ud mange steder.

Ulykkesrapporter begynder at komme. Kyodo News Service rapporterer om mindst 32 døde.

Den japanske regering erklærer nødsituation for atomkraftværk nær Sendai, 180 miles fra Tokyo. Japan har 54 atomkraftværker.

4 atomkraftværker tættest på jordskælvet lukkes.

Det rapporteres, at kølesystemet ved Fukushima -atomrapporten ikke virker: Myndighederne siger, at de gør det bedst.

Flere tusinde mennesker, der bor inden for halvanden kilometer fra anlægget, beordres at evakuere.

Japansk beboer beskriver evakuering af atomvåben 83 efterskælv på 21 timer i Japan Galleri: Massivt jordskælv rammer Japan

Politiet melder om at finde 200 - 300 lig i kystbyen Sendai.

60.000 - 70.000 byboere evakueret til krisecentre.

Rigspolitiet steg det bekræftede dødsfald til 93.

En brand ved atomkraftværket Onagawa er slukket ifølge International Atomic Energy Agency.

Der rapporteres om brande i mindst tre japanske præfekturer (Hakodate, Chiba, Miyagi). Et olieraffinaderi stod i flammer nær Tokyo.

En dæmning bryder i Fukushima -præfekturet og vasker masser af hjem væk.

4 millioner hjem i Tokyo og de omkringliggende områder er uden strøm.

Kyodo News Service sætter antallet af bekræftede dødsfald på 137.

Delta aflyser 29 fly til og fra Tokyo.

American Airlines omdirigerer seks flyvninger på vej til Tokyo til andre lufthavne.

Den amerikanske flåde annoncerer flytning af syv skibe mod Japan for at hjælpe nødhjælpsindsatsen.

Strålingsniveauet i Fukushima nr. 1 atomkraftværk rapporterede stigende.

Præsident Obama siger, at Japans premierminister ikke fortalte ham noget tegn på strålingslækager fra sit lands atomkraftværker.

Den japanske handelsminister Banri Kaieda siger, at der kan forekomme lille strålingslækage ved atomkraftværket i Fukushima.

Rigspolitiet bekræftede dødstallet til 151.

Japans gader uigenkendelige efter jordskælv

Udenrigsminister Hillary Clinton meddeler, at US Air Force -flyene er på vej til Japan med kølevæske til atomkraftbuksen i Fukushima. Rapporten om, at flyene bar kølevæske, viser sig senere at være fejlagtig.

Jordskælv på 6,2 rammer Nagano og Niigata -præfekturerne ifølge US Geological Survey.

Elektricitetsselskabets embedsmænd meddelte, at de muligvis vil udlufte radioaktiv luft fra atomkraftværket i Fukushima for at undgå nedbrud af reaktorens indeslutningsfartøjer.

Nuklear nødsituation erklæret på atomkraftværket Fukushima Daiichi.

Tjenestemænd rapporterer, at jordskælvet og tsunamien afbrød plantens elektriske strøm, og at backupgeneratorer var blevet deaktiveret af tsunamien.

Kommer af daggry afslører miles af motorveje lukket af jordskælvet.

13.000 mennesker rapporterede strandet i Narita lufthavn, yderligere 10.000 i Tokyos Haneda lufthavn.

Rigspolitiet satte nu dødstal på mindst 184.

Endnu et jordskælv --- et af en række i løbet af de sidste 24 timer --- rammer vestkysten af ​​Honshu. Skælvet havde en styrke på 6,3.

Tokyo Electric Power IC. siger, at radioaktive stoffer kunne have lækket ved Fukushima No, 1 atomkraftværk. Japans Nuclear and Industrial Safety Agency siger, at stråling nær plantens hovedport er mere end otte gange normalt niveau.

Tsunamier skyller fortsat i land på Japans nordøstlige kyst.

Dødstallet er nu på mindst 427.

Udenrigsminister siger, at 25 lande, herunder USA, har tilbudt bistand, herunder redningsteam og nødhjælp.

Tokyo Power Co. siger, at kølesystemer på tre af de fire enheder i sit Fukushima Daini -anlæg er slået fejl.

Mindst 6 millioner hjem - 10 procent af Japans husstande er uden elektricitet, ifølge landets ambassadør i USA.

Butikker begynder at løbe tør for mad, vand og benzin, da masser af indbyggere i det nordlige Japan strømmer sydpå fra deres jordskælvsramte hjembyer.

Dødstallet stiger til mindst 900 ifølge NHK -udsendelsesnetværket.

Redningsmænd kæmper for at trække overlevende fra sammenbrudte hjem, madvand og brande.

En lille mængde radioaktivt cæsium er flygtet fra et atomkraftværk i Fukushima præfektur, ifølge Japans atom- og industriorganisation. Tjenestemænd siger, at lækagen kunne have været forårsaget af smeltning af en brændstofstang.

Tokyo Electric Company siger, at en eksplosion på fabrikken i Fukushima Daiichi sårede fire arbejdere. (Kyodo News Agency vil senere citerer el -virksomhedens embedsmænd for at sige, at eksplosionen fik taget af en reaktor til at kollapse.)

Teknikere arbejdede på at indeholde temperaturer på to japanske atomkraftværker, hvor kølesystemer var blevet lammet af katastrofen.

I USA siger atomekspert Robert Alvarez (Institute for Policy Studies in Washington) situationen og har potentiale for katastrofe. & Quot

US Geological Survey siger, at jordskælvet ser ud til at have flyttet Japans hovedø --- hele øen-med 8 fod og forskudt jorden på sin akse.

Evakueringsområdet omkring Fukushima Daiichi atomkraftværk strakte sig til 20 kilometer (ca. 12,5 miles.)

Myndighederne insisterer på, at der ikke var blevet udsendt skadelige gasser ved eksplosionen ved atomkraftværket i Fukushima. De gav eksplosionen skylden på & quot vanddamp, der var en del af køleprocessen. & Quot

Brande rapporterede på mere end 200 steder i 12 af Japans præfekturer.

Amerikanske marinefly og helikoptere sendes fra baser i Okinawa for at hjælpe med hjælp.

Strålingsniveauer på Fukushima Daiichi -anlægget rapporteres at være faldet, da embedsmænd forbereder sig på at oversvømme indeslutningsstrukturen med havvand for at bringe temperaturen ned.

Myndighederne lægger planer om at distribuere jodtabletter --- en behandling for at forhindre strålingsforgiftning-til beboere i nærheden af ​​to beskadigede atomkraftværker.

Omkring 9500 mennesker --- halvdelen af ​​befolkningen-rapporteres at være uden regnskab i byen Minamisanriku på Japans Stillehavskyst.

En kabinetsembedsmand siger, at sammenbruddet af væggene i en bygning på fabrikken i Fukushima Daiichi ikke beskadigede reaktoren og dens indeslutningssystem.

Mange områder oplever blackouts, da kraftværker lukkes af sikkerhedsmæssige årsager. Antallet af huse uden strøm er ifølge kraftselskabet nede på godt 5 millioner.

Mere end 83.000 mennesker, der bor inden for 5 km fra to kraftværker, påbegynder en evakuering, der er beordret af regeringen.

50.000 japanske selvforsvarsstyrker, 190 fly og 25 skibe er blevet indsat for at hjælpe med redningsindsats, meddelte forsvarsministeriet.

Tv -stationen NHK rapporterer, at forsvarsministeriet havde sendt et team med speciale i radioaktiv forurening til en kommandopost i nærheden af ​​anlægget, hvor der var sket en strålingslækage.

Benzinsalget i Tokyo er begrænset til 20 liter (5,3 gallon) pr. Bil.

Tre personer (tilfældigt udvalgt ud af 90) tester positivt for strålingseksponering i Fukushima præfektur.

Der er nyheder om, at japanske myndigheder har informeret International Atomic Energy Agency (IAEA) om, at eksplosionen ved Fukushima Daiichi -anlægget fandt sted uden for det primære indeslutningsfartøj. Tokyo Power Company siger, at indeslutningsskibets integritet ikke er blevet kompromitteret. Havvand blandet med Bor injiceres for at afkøle systemet.

SENERE SØNDAGMORGEN

En embedsmand siger, at der kan opstå en nedsmeltning på det beskadigede anlæg, hvilket udløser frygt for en udbredt frigivelse af radioaktivt materiale. I mellemtiden mislykkedes en anden reaktor på samme anlæg søndag morgen - hvilket bragte antallet af enheder der, der oplever store problemer med at køle radioaktivt materiale, til tre


Tidslinje for Japans 2011 jordskælv, tsunami og atomkatastrofe

TOKYO (AP) - Torsdag markerer 10 -året for et massivt jordskælv, tsunami og atomkatastrofe, der ramte Japans nordøstlige kyst. Her er en tidslinje over begivenhederne:

- 11. marts 2011: Et jordskælv med en styrke på 9,0 rammer kysten klokken 14.46 og udløser en tårnhøj tsunami, der når land inden for en halv time. Tsunamien smadrer ind i atomkraftværket Fukushima Daiichi, ødelægger dets kraft- og kølesystemer og udløser nedsmeltninger ved tre reaktorer.

- 12. marts: En brinteksplosion sker ved anlæggets reaktor nr. 1 og sender stråling ud i luften. Beboere inden for en radius på 20 kilometer beordres til at evakuere. Lignende eksplosioner sker i to andre reaktorer i løbet af de følgende dage.

- 12. april: Japan hæver ulykken til kategori 7, det højeste niveau på den internationale nukleare og radiologiske begivenhedsskala, fra en tidligere 5, baseret på stråling frigivet til atmosfæren.

-24. april: Regeringen udpeger en eksklusionszone på 2 kilometer (1,25 kilometer) omkring atomkraftværket, der spænder over ni kommuner.

- 16. december: Efter at arbejdere i flere måneder kæmpede med at stabilisere anlægget, erklærer Japan en "kold nedlukning" med kernetemperaturer og pres ned til et niveau, hvor atomkædereaktioner ikke forekommer.

-23. juli 2012: En uafhængig undersøgelse, der er udpeget af en regering, konkluderer, at atomulykken var forårsaget af mangel på tilstrækkelig sikkerhed og krisestyring fra fabriksoperatøren, Tokyo Electric Power Co., slap overvågning af nukleare tilsynsmyndigheder og samarbejde.

- 1. april 2014: Evakueringsordren lempes for en by vest for det ødelagte atomkraftværk. Dele af mindst otte andre kommuner får lov til at genåbne i løbet af de næste tre år, selvom antallet af tilbagevendte stadig er lavt på grund af mangel på job og langvarige strålingsproblemer.

-22. december: TEPCO fuldender fjernelsen af ​​alle brugte nukleare brændstofstænger fra reaktorkølingens pool nr. 4, en indledende milepæl i anlæggets årtier lange nedlukning.

-2015-2019: Små robotter udstyret med kameraer og sensorer sendes ind i de beskadigede reaktorer, men giver kun begrænset udsigt over det meget radioaktive smeltede brændstofrester. Det gør planerne for fjernelse vanskeligere.

- 10. februar 2020: Et regeringspanel anbefaler kontrolleret udsætning i havet af hurtigt stigende mængder lækket radioaktivt kølevand på Fukushima -anlægget. TEPCO siger, at dets lagerkapacitet på 1,37 millioner tons vil være fuld i efteråret 2022.

- 10. december: Politiet siger, at dødstallet fra katastrofen, hovedsageligt fra tsunamien, når 18.426, heraf 2.527, hvis rester ikke er fundet.

- 13. februar 2021: Et jordskælv med en styrke på 7,3 rammer ud for Fukushima -kysten og efterlader en død og sårede mere end 180 mennesker. Det forårsager mindre skader på atomkraftværket.

-6. marts: Statsminister Yoshihide Suga besøger Fukushima og lover at fremskynde dekontamineringsindsatsen, så alle resterende forbudte zoner kan genåbnes, men giver ikke en tidsramme.


Ti år siden atomkatastrofen i Fukushima

11. marts 2011 var en frygtelig dag for Japan. Naturkatastrofer førte til en menneskeskabt katastrofe, som landet stadig håndterer. I dag er det 10 år siden, at en tsunami udløste verdens værste atomkatastrofe siden 1986.

Den eftermiddag ramte det mest kraftfulde jordskælv i Japans historie i havet ud for landets østkyst. Jordskælvet med en styrke på 9,0 fik en række tsunamier til at ramme Japans østkyst. Omkring 18.000 mennesker blev dræbt af disse tsunamier.

Den 11. marts 2011 ramte det mest kraftfulde jordskælv i Japans historie#8217s i havet ud for landets østkyst. Jordskælvet med en styrke på 9,0 fik en række tsunamier til at ramme Japans østkyst. Omkring 18.000 mennesker blev dræbt af disse tsunamier.
(Kilde: Maximilian Dörrbecker /Connormah/W.Rebel [CC BY-SA 3.0], via Wikimedia Commons.)

Men tsunamierne bragte også andre problemer. Fukushima Daiichi atomkraftværk er bygget lige ved kanten af ​​havet i byen Ōkuma, i Fukushima -distriktet. Anlægget skaber atomkraft.

Atomenergi
Atomkraft skabes ved at splitte atomer i en atomreaktion – den samme videnskab bag atomvåben. Atomkraft producerer giftigt affald, som skal håndteres og opbevares med stor omhu.
Den store fare ved atomkraft er stråling. Hvis noget er “radioaktivt ” betyder det, at det afgiver stråling. Stråling er energi, der rejser i bølger. Høje strålingsniveauer kan forårsage sygdom eller endda døden. Det kan også påvirke menneskers og dyrs DNA.
Fordi atomreaktioner skaber enorme mængder varme, skal atomreaktorerne, hvor reaktionerne sker, konstant afkøles.

For sikkerheds skyld blev Fukushima -kraftværket lukket ned, så snart jordskælvet blev opdaget. Da strømmen gik ud, måtte fabrikken regne med sine backup -elektriske generatorer for at køle reaktorerne.

Da en tsunami-bølge på 46 fod (14 meter) skyllede over anlægget, stoppede dets backupgeneratorer med at fungere. De oversvømmede reaktorer begyndte langsomt at blive overophedede. I løbet af de næste par dage smeltede tre af fabrikkens reaktorkerner ned, og der var tre store eksplosioner.
(Kilde: Digital Globe [CC BY-SA 3.0], via Wikimedia Commons.)

Men da en tsunami-bølge på 46 fod (14 meter) skyllede over anlægget, stoppede dens backupgeneratorer også. De oversvømmede reaktorer begyndte langsomt at blive overophedede. I løbet af de næste par dage smeltede tre af fabrikken ’s fire reaktorkerner ned, og der var tre store eksplosioner.

Stråling begyndte at flygte fra anlægget. Regeringen lukkede et område inden for 20 kilometer fra anlægget. Over 150.000 mennesker blev tvunget til at forlade deres hjem.

Stråling begyndte at flygte fra anlægget. Regeringen lukkede et område inden for 20 kilometer fra anlægget. Over 150.000 mennesker blev tvunget til at forlade deres hjem. Ovenfor måneder efter ulykken studerer en videnskabsmand skader på reaktor 3.
(Kilde: Greg Webb, IAEA Imagebank [CC BY-SA 2.0], via Wikimedia Commons.)

Det var ti år siden. Siden da har Japans regering brugt over 300 milliarder dollars på at komme sig efter jordskælvet, tsunamier og atomulykken.

Nogle områder omkring Fukushima-anlægget er stadig lukkede, men meget af det blev genåbnet for et par år siden. Forskere fra FN siger, at radioaktiviteten fra katastrofen sandsynligvis ikke vil forårsage fremtidige sundhedsproblemer for mennesker i området.

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Regeringen lukkede området omkring anlægget. Over 150.000 mennesker blev tvunget til at forlade deres hjem. Nogle områder omkring Fukushima-anlægget er stadig lukkede, men meget af det blev genåbnet for et par år siden. Ovenfor et af de lukkede områder i 2016.

Alligevel vendte de fleste mennesker, der plejede at bo i området, tilbage og vendte tilbage. I 2019 besluttede virksomheden, der ejer kraftværket, at lukke det permanent. Rengøring af stedet forventes at tage 40 år.

Gruppen Greenpeace, der arbejder for at beskytte miljøet, siger, at strålingsniveauerne er for høje i mange af de genåbnede områder. Gruppen siger, at regionen ikke kan vendes tilbage til det normale.

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I 2019 besluttede virksomheden, der ejer kraftværket, at lukke det permanent. Rengøring af stedet forventes at tage 40 år. De enorme bunker i dette billede er radioaktivt snavs, der er blevet opsamlet som en del af oprydningsindsatsen.

Et stort spørgsmål om oprydningen er, hvor alt det radioaktive materiale skal hen. Det er et problem, ethvert atomkraftværk står over for. Fukushima -anlægget har et ekstra problem. Der er så meget radioaktivt vand på anlægget, at der ikke er plads nok til at gemme meget mere.

Regeringen siger, at den har filtreret det meste af strålingen fra vandet og planlægger at frigive vandet tilbage i havet. Fiskere og grupper som Greenpeace kan ikke lide den idé. De er bange for, at strålingen vil skade havlivet og før eller siden kommer tilbage til mennesker.

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Et stort spørgsmål om oprydningen er, hvor alt det radioaktive materiale skal hen. Der er så meget radioaktivt vand på anlægget, at der ikke er plads nok til at gemme meget mere. Regeringen siger, at den planlægger at frigive vandet tilbage i havet.

Selvom Fukushima Daiichi -katastrofen skete for 10 år siden, fortsætter dens virkninger i dag og vil kunne mærkes langt ud i fremtiden.

Vidste du…?
Mange tror, ​​at atomkraft vil være et vigtigt redskab til at bekæmpe klimakrisen. Når atomkraft fungerer korrekt, skaber den langt mindre luftforurening end kul eller olie. Men atomkraft producerer altid radioaktive materialer. Spørgsmålet er, om mennesker sikkert kan kontrollere, opbevare og indeholde disse materialer, selv i lyset af enorme, uventede naturkatastrofer.

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Tidslinje for Japans 2011 jordskælv, tsunami og atomkatastrofe

TOKYO - Torsdag markerer 10 -året for et massivt jordskælv, tsunami og atomkatastrofe, der ramte Japans nordøstlige kyst. Her er en tidslinje over begivenhederne:

- 11. marts 2011: Et jordskælv med en styrke på 9,0 rammer kysten klokken 14.46 og udløser en tårnhøj tsunami, der når land inden for en halv time. Tsunamien smadrer ind i atomkraftværket Fukushima Daiichi, ødelægger dets kraft- og kølesystemer og udløser nedsmeltninger ved tre reaktorer.

- 12. marts: En brinteksplosion sker ved anlæggets reaktor nr. 1 og sender stråling ud i luften. Beboere inden for en radius på 20 kilometer beordres til at evakuere. Lignende eksplosioner sker i to andre reaktorer i løbet af de følgende dage.

- 12. april: Japan hæver ulykken til kategori 7, det højeste niveau på den internationale nukleare og radiologiske begivenhedsskala, fra en tidligere 5, baseret på stråling frigivet til atmosfæren.

-24. april: Regeringen udpeger en eksklusionszone på 2 kilometer (1,25 kilometer) omkring atomkraftværket, der spænder over ni kommuner.

- 16. december: Efter at arbejdere i flere måneder kæmpede med at stabilisere anlægget, erklærer Japan en "kold nedlukning" med kernetemperaturer og pres ned til et niveau, hvor atomkædereaktioner ikke forekommer.

23. juli 2012: En uafhængig undersøgelse, der er udpeget af en regering, konkluderer, at atomulykken var forårsaget af mangel på tilstrækkelig sikkerhed og krisestyring fra værkets operatør, Tokyo Electric Power Co., slap overvågning af nukleare tilsynsmyndigheder og collusion.

- 1. april 2014: Evakueringsordren lempes for en by vest for det ødelagte atomkraftværk. Dele af mindst otte andre kommuner får lov til at genåbne i løbet af de næste tre år, selvom antallet af tilbagevendte stadig er lavt på grund af mangel på job og langvarige strålingsproblemer.

-22. december: TEPCO fuldender fjernelsen af ​​alle brugte nukleare brændstofstænger fra reaktorkølingens pool nr. 4, en indledende milepæl i anlæggets årtier lange nedlukning.

-2015-2019: Små robotter udstyret med kameraer og sensorer sendes ind i de beskadigede reaktorer, men giver kun begrænset udsigt over det meget radioaktive smeltede brændstofrester. Det gør planerne for fjernelse vanskeligere.

— Feb. 10, 2020: A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. TEPCO says its 1.37 million ton storage capacity will be full in fall 2022.

— Dec. 10: Police say the death toll from the disaster, mostly from the tsunami, reaches 18,426, including 2,527 whose remains have not been found.

Indlæser.

— Feb. 13, 2021: A magnitude 7.3 earthquake hits off the Fukushima coast, leaving one dead and injuring more than 180 people. It causes minor damage at the nuclear plant.

— March 6: Prime Minister Yoshihide Suga visits Fukushima and pledges to accelerate decontamination efforts so all remaining no-go zones can be reopened, but doesn’t give a timeframe.


Læs mere

The disaster also caused level 7 meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex, situated about 140 miles north of Tokyo.

Here is everything you need to know about it.

Hvad skete der?

Damage to the plant had already been caused by the massive earthquake, which sent its three nuclear reactors into automatic shut down as a safety measure.

But the reactors were not prepared for the tsunami waves that followed, and as the diesel generators and battery back-ups that were supposed to cool the reactor cores failed, temperatures began to rise uncontrollably.

Hydrogen gas was released, causing large explosions which sent all three reactors into meltdown, spewing radiation and forcing 150,000 people from their homes, many of whom will never return.

No-one was killed from the explosions themselves, but 35 people were injured and the incident sparked a major nuclear ordeal. The disaster was eventually classified at the same severity level as the 1986 explosion at Chernobyl.

Could the disaster have been prevented?

An official inquiry found that Tokyo Electric Power (Tepco) – the company running the station – had failed to plan for the very foreseeable dangers of earthquakes and tsunamis, and had no evacuation plan in place.

And in 2012, a panel criticised the response of Tepco, regulators and then Prime Minister Naoto Kan, who had resigned the year before after criticism of his handling of the disaster.

“The Fukushima nuclear power plant accident was the result of collusion between the government, the regulators and Tepco, and the lack of governance by said parties,” the panel said.

Regulators had been reluctant to adopt global safety standards that could have helped prevent the disaster: "Across the board, the commission found ignorance and arrogance unforgivable for anyone or any organisation that deals with nuclear power,” said the panel.

It also found evidence that damage from the earthquake, and not just the ensuing tsunami, could not be ruled out as a cause of the incident in one of the world’s most quake-prone nations.

“We have proved it cannot be said that there would have been no crisis without the tsunami,” Katsuhiko Ishibashi, seismologist and panel member, said.

What is the area like today?

Many people still have an image of the negative situation of Fukushima Prefecture shortly after the region was hit by the disaster-caused nuclear plant accident.

This has hindered Fukushima's recovery and prevented various countries and regions from lifting import restrictions on agricultural and other products from Japan.

It took six years and a huge clean-up effort before most of the residents evacuated from the area were allowed to return, and today there remains a “core zone” which is still too dangerous for 50,000 inhabitants to be allowed back.

The mammoth clean-up operation is still ongoing, with a crew of over 5,000 people. Independent estimates put the final bill for the project at over £550 billion, and current predictions suggest it may be another 30 years before the site is fully cleaned up.

But recovery has been steadily progressing, and earlier this month the Reconstruction Agency – a government agency overseeing work on recovery from the Great East Japan Earthquake – opened the Fukushima Updates website.

The aim of the site is to accurately and clearly send out information in English regarding questions and concerns that people may have over the safety of Fukushima and Japan.

Intended as a forefront tool to disseminate the latest information on Fukushima, the site responds in a Q&A format to questions and concerns that people may have over the current situation of Fukushima, and the safety of Japanese food products.


Northern Japan’s nuclear emergency

Of significant concern following the main shock and tsunami was the status of several nuclear power stations in the Tōhoku region. The reactors at the three nuclear power plants closest to the quake’s epicentre were shut down automatically following the temblor, which also cut the main power to those plants and their cooling systems. However, inundation by the tsunami waves damaged the backup generators at some of those plants, most notably at the Fukushima Daiichi (“Number One”) plant, situated along the Pacific coast in northeastern Fukushima prefecture about 60 miles (100 km) south of Sendai. With power gone, the cooling systems failed in three reactors within the first few days of the disaster, and their cores subsequently overheated, leading to partial meltdowns of the fuel rods. (Some plant workers, however, attributed at least one partial meltdown to coolant-pipe bursts caused by the earthquake’s ground vibrations.) Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and burned sizable holes through the floor of each vessel, which partially exposed the nuclear material in the cores. Explosions resulting from the buildup of pressurized hydrogen gas in the outer containment buildings enclosing reactors 1, 2, and 3, along with a fire touched off by rising temperatures in spent fuel rods stored in reactor 4, led to the release of significant levels of radiation from the facility in the days and weeks following the earthquake. Workers sought to cool and stabilize the damaged reactors by pumping seawater and boric acid into them.

Because of concerns over possible radiation exposure, Japanese officials established an 18-mile (30-km) no-fly zone around the facility, and an area of 12.5 miles (20 km) around the plant was evacuated. The evacuation zone was later extended to the 18-mile no-fly radius, within which residents were asked to leave or remain indoors. The appearance of increased levels of radiation in some local food and water supplies prompted officials in Japan and overseas to issue warnings about their consumption. At the end of March, seawater near the Daiichi facility was discovered to have been contaminated with high levels of radioactive iodine-131. The contamination stemmed from the exposure of pumped-in seawater to radiation inside the facility this water later leaked into the ocean through cracks in water-filled trenches and tunnels between the facility and the ocean.

In mid-April Japanese nuclear regulators elevated the severity level of the nuclear emergency at the Fukushima Daiichi facility from 5 to 7—the highest level on the scale created by the International Atomic Energy Agency—placing the Fukushima accident in the same category as the Chernobyl accident, which had occurred in the Soviet Union in 1986. Radiation levels remained high in the evacuation zone, and it was thought that the area might be uninhabitable for decades. However, several months after the accident, government officials announced that radiation levels in five towns located just beyond the original 12.5-mile evacuation zone had declined enough that they could allow residents to return to their homes. Although some people did come back, others stayed away, concerned about the amount of radioactive materials still in the soil. Attempts were made in several of those areas to remove contaminated soil. In December 2011 Japanese Prime Minister Noda Yoshihiko declared the Fukushima Daiichi facility stable after the cold shutdown of its reactors had been completed.

In the years following the accident, numerous leaks at the facility occurred at the site where contaminated reactor cooling water was stored. A significant leak occurred in August 2013 that was severe enough to prompt Japan’s Nuclear Regulation Authority to classify it as a level-3 nuclear incident.


Timeline of Events at Japan's Fukushima Nuclear Reactors

A 9.0-magnitude earthquake (originally estimated at 8.9) struck off the coast of Honshu, Japan, and an enormous tsunami followed shortly after. Eleven nuclear reactors at the four nearest power plants automatically shut down upon sensing ground accelerations, stopping the nuclear fission of uranium in their cores. Nuclear fuel requires continued cooling even after a plant is shut down, though, because residual fission products continue to decay and produce a huge amount of heat. The Japanese plants use continually-pumped water, which absorbs a great deal of heat, to cool their nuclear reactors.

The earthquake knocked out the electricity at the Fukushima Daiichi plant run by Tokyo Electric Power Company (TEPCO). Emergency diesel generators were used to pump water to cool Reactor Units 1, 2 and 3, which had been operating at the time of the quake, but an hour later, the back-up generators were knocked out by tsunami flooding.

Insufficient power meant that water could not be pumped through the nuclear cores quickly enough. As the water inside the reactors heated up too high and started boiling, the water level dropped inside the cores, and the pressure rose from the steam. TEPCO declared a state of emergency. Japanese authorities ordered the evacuation of residents within a three-kilometer radius of Fukushima Daiichi, and told people within a 10-kilometre radius to remain indoors. This was a precautionary measure because, at that point, there had been no release of radiation from the nuclear power plant. The containment vessels housing the reactor vessels were withstanding the increase in pressure inside.

Workers at Fukushima Daiichi worked desperately to restore the diesel generators, and to hook up mobile power sources in order to pump sufficient water to cool the three hot reactors. Units 1 and 2 were both experiencing water level drops and rises in pressure, but the water level in all three reactor vessels remained above the fuel elements at the end of March 11.

A fire broke out at a nuclear power plant in Oganawa immediately after the earthquake. This was soon extinguished, and that plant saw no further problems.

At 9 am local Japan time, the pressure within the containment vessel of Fukushima Daiichi Unit 1 was as high as 840 kPa, compared to reference levels of 400 kPa. Officials vented the vessel to lower its pressure. The released water vapor was filtered to retain most of the radiation within the containment, but because the vapor had been through the reactor core, a certain release of radioactive substances such as caesium-137 and iodine-131 was inevitable. Tepco was also preparing to relieve pressure for Units 2 and 3.

An explosion occurred at Unit 1, blowing off the roof and walls of the concrete structure built around it and leaving a naked steel structure behind. Four workers were injured. Tepco tamped down initial panic and confusion by explaining that the external building structure does not act as the containment, which is an airtight steel structure within, and that the containment was not damaged in the explosion. Hydrogen gas which had burned off of cladding around the fuel rods inside the reactors was the main substance released.

When radiation levels reached 500 microsieverts per hour around the facility due to pressure venting, non-radioactive potassium iodide tablets were brought into the area, but not distributed. Potassium iodide is quickly taken up by the body and its presence prevents the absorption of iodine-131 should people be exposed to it. The evacuation radius was also incrementally increased, eventually expanding to a 20-km radius around the facility. The injection of seawater into parts of the building near the reactor started at 8.20pm local time and was followed by the addition of boric acid, which inhibits nuclear reactions.

The nearby Fukushima Daini power plant encountered problems for the first time after safely shutting down four operational reactor units the day before. Daini Unit 1's isolation cooling system, supplemented by a back-up water condensate system, had been operating normally, but the back-up system stopped working at 5.32am local time when its suppression chamber reached 100 degrees Celsius. Residents within 10 kilometers of Daini were evacuated in case Tepco were to need to vent the containments of Daini units. The number of evacuees around both sites stood at 185,000.

The containment of Reactor Unit 3 at Fukushima Daiichi was vented again in order to lower the pressure inside. Water levels in all three reactors were continuing to drop. Following the failure of a high pressure injection system and other attempts to cool the plant, injection of water, and later seawater, started.

Japanese officials said they believed a partial meltdown had probably occurred in at least two of the nuclear reactors, due to water levels having fallen below the level of the fuel rods inside them. [Infographic: What Is a Nuclear Meltdown?]

At Fukushima Daini Unit 1, plant operators were able to restore a residual heat remover system to cool the reactor, and workers at Units 2 and 4 were working to restore the same residual heat removal systems. Unit 3 was in a safe, cold shutdown. Radiation dose rate measurements observed at four locations around the plant's perimeter over a 16-hour period on 13 March were all normal.

Throughout the day, all Fukushima Daiichi reactors were still being powered by mobile power generators on site, because power via off-site power supply or backup diesel generators had still not been restored.

A skeleton crew of 50 workers were continuing to inject seawater and boron into the reactor vessel to cool the reactor at Unit 1, while the reactor core in Unit 2 was being cooled through reactor core isolation cooling, a procedure used to remove heat from the core, via mobile power generators. The reactor water level was lower than normal but remained steady.

A seawater-boric acid combination continued to be injected into Unit 3. Water levels inside the reactor vessel increased steadily for a while but later stopped increasing for an unknown reason. The concentration of hydrogen was increasing inside the containment building, and a hydrogen explosion occurred at Unit 3 at 11:01 am local Japan time, injuring 11 workers. The primary containment vessel was not damaged.

Fortunately, prevailing winds were moving away from the Japanese coast to the East, carrying any radioactive materials released by venting and explosions out to sea.

The reactors Units 1, 2 and 3 of the Fukushima Daini nuclear power plant were pronounced to be in cold shutdown status, meaning the pressure of the water coolant in the three reactors was around atmospheric level and the temperature was below 100 degrees Celsius. Under these conditions, the reactors were considered to be safely under control. Unit 4 was not yet in a cold shutdown.

A dose rate of 11.9 millisieverts (mSv) per hour was recorded early on March 15 and a 0.6 millisieverts (mSv) per hour rate was recorded six hours later, suggesting radiation levels were dropping off. Cooling via seawater injections was ongoing in all three units.

The spent fuel storage pond at the Unit 4 reactor of the Fukushima Daiichi nuclear power plant, which was thought to be in a cold shutdown, caught on fire. Radioactivity was being released directly into the atmosphere, and radiation doses of up to 400 millisieverts per hour were briefly reported between Units 3 and 4. That hourly dose is approximately 100 times the amount of background radiation the average person absorbs in a year.

The spent fuel fire was extinguished two hours after it began, and radiation levels dropped off again shortly after. Authorities said the fire may have been caused by an earlier hydrogen explosion. An explosion at the Unit 2 reactor at the Fukushima Daiichi plant had occurred at around 6:20 am local Japan time.

The 400 mSv per hour recorded radiation level caused workers to be temporarily evacuated, but they were later called back in. Officials advised residents within 30 km of Fukushima Daiichi to stay indoors.

It was determined that the hydrogen explosion at Unit 2 may have affected the integrity of its primary containment vessel, which would mean greater radiation leaks to the environment.

By the end of March 15, all units at Fukushima Daini had been brought to a cold shutdown.

The pressure inside Unit 3 suddenly plunged, suggesting that either the gauges were malfunctioning or its containment vessel may have cracked. Radiation doses of about 250 millisieverts an hour had been detected 100 feet above the plant.

Early in the day, the water level in Unit 5 at Fukushima Daiichi, which was loaded with fuel but thought to be in a cold and safe shutdown, was found to be dropping. Diesel generators from Unit 6 were brought over to Unit 5 to pump its cooling system.

Due to ongoing power failures, temperatures at spent fuel pools at Fukushima Daiichi were rising by approximately 1 degree Celsius per day. The hottest was the pool near Unit 4, which was at 84 degrees Celsius. According to IAEA experts, a typical spent fuel pool temperature is kept below 25 ?C under normal operating conditions, which requires a constant power source.

Japanese Defense Minister Toshimi Kitazawa announced that Special Defense Forces helicopters planned to drop water onto the spent fuel rods near Unit 3, and officials were preparing to spray water into Unit 4 from ground positions.

Tepco confirmed that several workers had been injured over the previous few days. At least 17 workers had experienced some radiation exposure, and one worker suffered "significant" radiation exposure while venting a reactor unit. Two workers are missing.

Four helicopters dropped water on the spent fuel rods of Unit 3, but this had little effect on their temperature. Military fire trucks later began spraying cooling water on them. Unit 3 was considered to be a greater threat than Unit 4, because it is the only one loaded with a mixed fuel known as MOX &ndash which contains plutonium-239, a more dangerous radioactive material than depleted uranium-238.

An external grid power line cable was successfully attached to Unit 2. Power will be turned on in Unit 2 as soon as workers finish spraying of water on Unit 3.

For the first time, Japanese officials admit that burying the damaged nuclear power plants in sand and concrete - the method used to seal huge radiation leakages from the Chernobyl meltdown in 1986 - maybe be the only way to prevent a massive radiation release.

"It is not impossible to encase the reactors in concrete. But our priority right now is to try and cool them down first," an official from the plant operator, Tokyo Electric Power Co, told a news conference. Officials said they still hoped to fix a power cable to at least two reactors to restart water pumps needed to cool overheating nuclear fuel rods at the Fukushima Dai-ichi plant.

New reports trickle out that, immediately after the nuclear damage was detected, Japan turned down an offer from the United States to provide technical support for cooling and dismantling the damaged reactors. At that point, Japanese officials said, the government and TEPCO still believed they could handle the situation themselves.

Meanwhile, Japan fallout reaches California but, according to an official, radiation is miniscule, far below health threat levels.

March 19 - 20:

Workers continued spraying Units 1, 2 and 3 with seawater and worked to reconnect the power supply to Unit 2 (which would then act as a hub to power Unit 1) in order to operate their cooling systems.

Unit 1's containment vessel appeared to be intact and pressure inside was restored, but the containments of Units 2 and 3 are both thought to have cracked during explosions in previous days. White smoke was seen to be emerging from both vessels, but seemed to diminish over time.

The spent fuel pools in Units 3 and 4 are still dangerously hot, and helicopters have continued dropping water on them.

The reactor cores and spent fuel pools of Units 5 and 6, which were in a cold shutdown at the time of the March 11 earthquake and had not since been problematic, began to heat up. Workers have turned on generators to pump water through them and have drilled holes in the roofs of their containment buildings to prevent the hydrogen explosions that damaged other units in previous days.

The Japanese government has advised evacuees who live within a 20 km radius of the Fukushima Daiichi plant to take iodide pills after heightened levels of radioactive iodine-31 were found in milk and vegetables grown in the area.

The containment vessels of Reactor Units 2 and 3, which were suspected of having cracked in explosions, have been found to be intact.

Seawater injection is continuing in Units 1, 2 and 3. Plant officials said off-site power was about to be restored to Units 1 and 2, and had already been restored to Units 3 and 4. Restored power will allow normal cooling operations to resume in the reactors. A U.S. Nuclear Regulatory Commission (NRC) official described the situation at the Fukushima plant as "on the verge of stabilizing."

The NRC is planning a 90-day review of reactor safety to assess natural disaster preparations at 104 U.S. nuclear plants, some of which use the same model as the Fukushima plant. A report on the NRC&rsquos initial findings will be released after 30 days. Bill Borchardt, executive director of operations at NRC, said he and his commission do not expect to find any significant weaknesses.

Efforts to restore electricity to the Fukushima Daiichi plant in order to resume normal operation of its cooling system were sidetracked by rising temperatures at Unit 2's spent fuel pool. Steam was seen spewing from the pool. If water were to boil away and leave the spent fuel rods exposed, they would melt, sending radioactive materials into the air, so workers had to focus on cooling the pool down by spraying it with water.

A power line connected to Reactor Units 1 through 4 may be damaged, so technicians are working on fixing it while other workers continue to pump water through the Units via fire hoses.

Elevated levels of radioactive iodine and cesium have also been detected in the seawater near Fukushima, though not elevated enough to pose a direct threat to human health according to experts. The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) have begun carrying out comprehensive measurements of the radioactivity in the marine environment. Sea water sampling from eight locations will be sampled and their radionuclide concentrations and dose rates will be analysed by the Japan Atomic Energy Agency (JAEA). Results will be provided on 24 March.

Radiation levels surpassing 400 times the normal level had been detected in soil about 25 miles from the Fukushima plant, according to the government's Science Ministry. Though drastically higher than normal, this is also said not to pose an immediate health risk.

Workers continue their efforts to reconnect power to the plant, after temporarily evacuating due to higher than normal levels of radioactivity being detected around a smoking fuel pool near Reactor Unit 2. Off-site electricity is connected to a transformer in Unit 2, but technicians must conduct diagnostic tests to determine the integrity of the reactor's electrical systems before turning them on. When Unit 2 is powered up, workers will move to Unit 1, which sustained some damage during a hydrogen explosion and may take more time to get going.

Units 3 and 4 have not been hooked up to power yet, despite previously reports to the contrary. There is concern about the too-hot spent fuel pools at both units. Units 5 and 6 are hooked up to off-site power, and are not causes for immediate concern.

In Tokyo, iodine-131 was detected in water samples at a level of 210 becquerels per liter. The recommended limit for infants is 100 becquerels per liter, and for adults, the limit is 300 becquerels. Japan's Health Ministry said it was unlikely that there would be negative consequences to infants who drank the contaminated water, but that it should be avoided if possible.

Shipment of raw milk and parsley from Ibaraki Prefecture, adjacent to Fukushima, was suspended. Shipments of 11 contaminated vegetables from Fukushima Prefecture ended on Monday (March 21).

Radioactive iodine found in water in Tokyo dropped back to safe levels after being considered dangerous for consumption by infants the day before, according to city authorities. The level fell to 79 becquerels per liter (Bq/L) and is considered safe for consumption by both infants and adults. In Japan, 100 Bq/L is safe for infants and 300 Bq/L is safe for adults. These limits are much stricter than those in the U.S., where infants are allowed to drink water containing radioactivity as high as 300 Bq/L, and adults are allowed to drink water with 3,000 Bq/L of radioactivity.

At the Fukushima Daiichi plant, 140 miles north of Tokyo, workers are still pumping seawater onto spent fuel pools at all six nuclear reactors, using a combination of sprayhoses, pump trucks, and water injection through functional cooling lines. The temperature of the fuel pool at Unit 2, the most worrisome of them all, climbed to 52 degrees Celsius on March 23 but has since dropped back to 47 degrees C. Spent fuel pools are normally kept under 25 degrees C.

Three contracted workers at Unit 3 were exposed to elevated levels of radiation, and were taken to hospital with beta-radiation burns on their feet and legs. The workers purportedly ignored the readings of their dosimeters while treading through contaminated water, believing the meters to be giving inaccurate readings.

The number of workers at the Fukushima Daiichi nuclear power plant found to have received more than 100 millisieverts of radiation dose totalled 17. These include the three contract workers, and fourteen Tepco employees.

Japanese officials have begun assisting the evacuation of citizens in a larger radius around the Fukushima nuclear plant. They are now encouraging people living within 19 miles to leave. The mandatory evacuation radius remains at 12 miles around the plant, but the new extended radius for assisted evacuations suggests the officials do not consider the situation at the plant to be on the verge of stabilizing.

An official said there is evidence that the reactor vessel housing Unit 3 is damaged. Unit 3 is the reactor that burns mox fuel, a mix of uranium and plutonium, so there are grave concerns that these two dangerous substances could be released to the environment.

Fortunately, the effects of iodine-131 leaked to the environment appears not to have done significant thyroid damage in the first round of tests conducted March 24 and announced March 25. The thyroid glands in 66 children were examined at the Kawamata Town Health Center (40-50 km from Fukushima Daiichi) and Kawamata Town Yamakiya Branch Office (30-40 km from Fukushima Daiichi NPP). According to a press release form the Nuclear and Industrial Safety Agency, the results indicate that the dose rate "of all the 66 children including 14 infants from 1 to 6 years old had no big difference from the level of background and was at the level of 'no problem' in the view of the Nuclear Safety Commission."

The three contracted workers who were admitted to hospital March 24 for radiation exposure will be released on Monday. Rethy Chem, human health director at the International Atomic Energy Agency (IAEA), told a news conference that this means they were probably not seriously harmed.

With power not yet back on at the plant, manual seawater injection is continuing into Units 1, 2, 3 and into the spent fuel pool of Unit 3. The spent fuel pool of Unit 4 is being sprayed with seawater. Workers are still attempting to restore the cooling systems in the reactors.

March 26 - 27:

Over the weekend, workers switched from pumping sea water through the reactor cooling lines to using freshwater, which is less corrosive and leaves less deposits. The temperatures in the reactor pressure vessels of Units 1 to 3 all stabilized. Unit 1 was the hottest at 144 degrees-C. The pressures in the three vessels also stabilized at or around atmospheric pressure. Units 5 and 6 stayed in a cold shutdown with approximately stable temperatures and pressures. (The reactor vessel in Unit 4 contained no fuel rods at the time of the earthquake.)

White smoke was seen emanating from the spent fuel pools at Units 3 and 4, possibly carrying with it radioactive materials. Workers continued spraying the spent fuel pools with seawater.

Technicians managed to get all six units hooked up to off-site power. The lights are on in several of the units' control rooms, but individual components still needed to be checked before the electric cooling system could be energized.

Gamma radiation dose-rates, measured in the Tokyo region at 8 locations, ranged from 0.08 to 0.15 microsievert per hour, which is within or slightly above the normal background according to the International Atomic Energy Agency (IAEA). At distances of 30 to 41 km from the Fukushima nuclear power plant, the dose-rates ranged from 0.9 to 17 microsievert per hour - higher than the normal background.

Radiation levels in the Pacific Ocean were also assessed at several locations. According to the IAEA, the contamination at these locations is influenced by aerial deposition of fallout as well as by the migration of contaminated seawater from the discharge points at the reactor. The measured radiation doses rates above the sea remain consistently low (between 0.04 and 0.1 microsievert per hour).

The state of the reactors themselves is much the same as on preceding days, as are efforts to restore electricity to the reactors. Before switching on full power, workers must remove water from the reactor turbine buildings. Unfortunately, in doing this, they discovered some bad news.

Radiation measuring 1,000 millisieverts per hour was detected in water in an overflow tunnel outside Unit 2's turbine building. (For comparison's sake, the maximum dose allowed for workers at the plant is 250 millisieverts per year). The tunnel leads to an opening just 180 feet from the sea, according to Hidehiko Nishiyama, deputy director-general for the Nuclear and Industrial Safety Agency. Contaminated water was also found at tunnels leading from the Unit 1 and 3 reactors, though with much lower levels of radiation.

The nuclear safety agency also reported that radioactive iodine 131 was detected March 27 at a concentration 1,150 times the maximum allowable level in a seawater sample taken about a mile north of the drainage outlets of Units 1 through 4. The amount of cesium 137 found in water 1,000 feet from plant was 20 times the normal level, the same level as readings taken a week ago.

No fishing has been allowed in this area since the earthquake, so, presumably, no contaminated food has entered the food chain via the sea.

Yukiya Amano, IAEA Director General, says that the situation at the Fukushima nuclear power plant remains very serious. Workers are focusing on removing water that had previously been sprayed on the containment vessels and spent fuel pools, and safely storing it. The reactor buildings must be dried out before electrical cooling systems can be powered back up. Because the water inside them has become contaminated by proximity to the nuclear fuel, it must be stored and slowly decontaminated rather than released to the environment.

Plutonium, one of the most dangerous radioactive substances, has been found in soil samples near the nuclear plant. According to the IAEA, "Traces of plutonium are not uncommon in soil because they were deposited worldwide during the atmospheric nuclear testing era. However, the isotopic composition of the plutonium found at Fukushima Daiichi suggests the material came from the reactor site, according to Tepco officials. Still, the quantity of plutonium found does not exceed background levels . tracked over the past 30 years." [Find out why plutonium is more dangerous than uranium]

Officials publically acknowledged for the first time that Reactor Units 1 through 4 at the Fukushima Daiichi nuclear power plant will have to be permanently scrapped. The multi-billion dollar facilities have sustained too much damage by earthquakes, explosions, and seawater corrosion to ever function again.

They cannot be abandoned yet, however. Workers are still manually cooling the fuel in the facilities via freshwater injection. They are also pumping contaminated water out of the reactors' turbine buildings and into condensed water storage tanks in order to let the turbine buildings try out before restoring electric cooling systems.

This article was provided by Life's Little Mysteries, a sister site to LiveScience. Follow Natalie Wolchover on Twitter @nattyover


Se videoen: Fukushima Uncensored - Documentary HD (August 2022).