To date, the nuclear accidents at the Chernobyl (1986) and Fukushima Daiichi (2011) nuclear power plants, are the only INES level 7 nuclear accidents.[1][2]

Chernobyl and Fukushima nuclear accidents

The following table compares the Chernobyl and Fukushima nuclear accidents.

Plant Name Chernobyl Fukushima Daiichi
LocationSoviet Union (Ukrainian Soviet Socialist Republic) 51°23′22″N 30°05′57″E / 51.38946°N 30.09914°E / 51.38946; 30.09914Japan 37°25′32″N 141°01′18″E / 37.4255°N 141.0216°E / 37.4255; 141.0216
Date of the accidentApril 26, 1986March 11, 2011
INES Level77
Plant commissioning date19771971
Years of operation before the accident9 years (plant)
  • 2 years (Unit 4)[3]
40 years (plant)
  • 40 years (Unit 1)
  • 37 years (Unit 2)
  • 35 years (Unit 3)
  • 33 years (Unit 4)
Electrical outputplant (net): 3700 MWe (4 reactors)
reactors (net): 925 MWe (Units 1–4)		plant (net): 4546 MWe (6 reactors)
reactors (net): 439 MWe (Unit 1), 760 MWe (Units 2–5), 1067 MWe (Unit 6)
Type of reactorRBMK-1000 graphite moderated, 2nd generation reactor without containmentBWR-3 and BWR-4 reactors with Mark I containment vessels
Number of reactors4 on site; 1 involved in accident6 on site; 4 (and spent fuel pools) involved in accident; one of the four reactors was empty of fuel at the time of the accident.
Amount of nuclear fuel in affected reactors1 reactor—190 tonnes (t, metric tons = 210 U.S. short tons): spent fuel pools not involved in incident[4]4 reactors—854 tonnes (t, metric tons): 81 t in Unit 1 reactor, 111 t in Unit 2 reactor, 111 t in Unit 3 reactor, 0 t in Unit 4 reactor (defueled), 59 t in Unit 1 spent fuel pool (SFP), 119 t in Unit 2 SFP, 104 t in Unit 3 SFP, and 269 t in Unit 4 SFP[lower-alpha 1]
Cause of the accidentProximate cause was human error and violation of procedures. The unsafe reactor design caused instability at low power due to a positive void coefficient and steam formation. When an improper test was conducted at 1:00 am at low power, the reactor became prompt critical. This was followed by a steam explosion that exposed the fuel, a raging fire, and a core meltdown. The fire lasted for days to weeks, and there is controversy over whether it was the fuel burning, nuclear decay heating or whether the graphite moderator that made up most of the core was involved. See Chernobyl Disaster, Note 1, for more discussion.The plants were not designed with consideration of such a large tsunami concurrently occurring with the ground sinking. Subsequent review did not lead to mitigation. A major earthquake and tsunami caused the destruction of power lines and backup generators. Once the plants were without external power and the generators were flooded, a catastrophic decay heat casualty ensued, leading to major reactor plant damage including meltdowns and explosive loss of reactor containment.
Maximum level of radiation detected300 Sv/h shortly after the explosion in vicinity of the reactor core.[8]530 Sv/h inside Unit 2 containment vessel in 2017 according to Japan Times.[9]
Radioactivity releasedAccording to IAEA, total release was 14 EBq (14,000 PBq).[10] 5.2 EBq (5,200 PBq) in iodine-131 equivalent [11][12]As of 2014, a peer reviewed estimate of the total was 340–780 PBq, with 80% falling into the Pacific Ocean.[13] Radiation continues to be released into the Pacific via groundwater.
Area affectedAn area up to 500 kilometres (310 mi) away contaminated, according to the United Nations.[14][15][16]Radiation levels exceeding annual limits seen over 60 kilometres (37 mi) to northwest and 40 kilometres (25 mi) to south-southwest, according to officials.
Exclusion Zone Area30 km20 km (30 km voluntary) extending north-west to 45 km in the downwind direction to Iitate, Fukushima[17]
Population relocated335,000 (About 115,000 from areas surrounding the reactor in 1986; about 220,000 people from Belarus, the Russian Federation and Ukraine after 1986)154,000[18]
Population returnedNone122,000[19]
Direct fatalities from the accidentTwo immediate trauma deaths; 28 deaths from Acute Radiation Syndrome out of 134 showing symptoms; four from an industrial accident (helicopter crash); 15 deaths from radiation-genic thyroid cancers (as of 2005);[20] as many as 4000 to 90000 cancer related deaths.[21]1 confirmed cancer death attributed to radiation exposure by the government for the purpose of compensation following opinions from a panel of radiologists and other experts, medical sources pending for long-term fatalities due to the radiation.
Current statusAll reactors were shut down by 2000. The damaged reactor was covered by a hastily built steel and concrete structure called the sarcophagus. A New Safe Confinement structure was installed in November 2016, from which the plant will be cleaned up and decommissioned.Cold shutdown declared on 16 December 2011, but decommissioning is likely to take 30 to 40 years.[22][23] All fuel rods in reactor 4 pool removed. Fukushima disaster cleanup is ongoing.

Radioactive contamination discharge

Report date Place Period Iodine-131
(TBq)		 Caesium-137
(TBq)		 Source
from to from to
2002 Chernobyl 25 April – June 1986 1,600,000 1,940,000 59,000 111,000 NEA[24]
22 March 2011 Fukushima 12 – 15 March 2011 400,000 3,000 30,000 ZAMG[25]
2 April 2011 Fukushima 12 – 19 March 2011 10,000 700,001 1,000 70,000 ZAMG[26]
12 April 2011 Fukushima 11 March – 5 April[27] 150,000 12,000 NSC[28]
12 April 2011 Fukushima 11 – 17 March 2011 130,000 6,100 NISA[28]
7 June 2011 Fukushima 11 – 17 March 2011 160,000 15,000 NISA[29]
24 Aug. 2011 Fukushima 11 March – 5 April 130,000 11,000 NSC[30]
15 Sept. 2011 Fukushima March – September 100,000 200,000 10,000 20,000 Kantei[31]
Report date Place Period Amount
(TBq)		 Source
12 April 2011 Chernobyl 25 April – June 1986 5,200,000 NISA[28]
12 April 2011 Fukushima 11 March – 5 April 2011 630,000 NSC[27][28]
12 April 2011 Fukushima 11 – 17 March 2011 370,000 NISA[28]
April 2011 Fukushima 4 April 2011 154 NSC[27]
25 April 2011 Fukushima 24 April 2011 24 NSC[27]
6–7 June 2011 Fukushima 11 – 17 March 2011 770,000 NISA[32]>[29]
7 June 2011 Fukushima 11 – 17 March 2011 840,000 NISA,[33] press printing[32]
17 August 2011 Fukushima 3–16 August 2011 0.07 Government[34]
23 August 2011 Fukushima 12 March - 5 April 2011 630,000 NISA[35]
Report date Period Into the sea
(TBq)		 Source
direct indirect
21 May 2011 1 – 6 April 2011 4,700 Tepco[36]
End of August 2011 March – August 2011 3,500 16,000 JMA[37]
8 September 2011 March – April 2011 15,000 Scientist Group[38]
29 October 2011 21 March – 15 July 2011 27,100 IRSN[39]

See also

Notes

  1. ↑ 183.3 kg/assembly;[5] 400 assemblies in reactor 1, 548 assemblies in reactors 2&3, 0 assemblies in reactor 4, total of 1496 assemblies in reactors 1-4;[5][6] 292 assemblies in Unit 1 spent fuel pool (SFP), 587 assemblies in Unit 2 SFP, 514 assemblies in Unit 3 SFP, 1331 assemblies in Unit 4 SFP, total of 2724 assemblies in spent fuel pools 1-4.[7]

References

  1. ↑ "The INES scale". laradioactivite.com. Retrieved 7 September 2023.
  2. ↑ "Fukushima Daiichi Accident - World Nuclear Association". world-nuclear.org. Retrieved 7 September 2023.
  3. ↑ "PRIS - Reactor Details". www.iaea.org. Retrieved 14 July 2016.
  4. ↑ "Chernobyl Accident And Its Consequences - Nuclear Energy Institute". www.nei.org. Nuclear Energy Institute. Retrieved 9 April 2017. - note that figures were converted into US tons
  5. 1 2 Fukushima: Background on Reactors. February 2012. Retrieved 4 September 2014. - 183.3 kg / assembly
  6. ↑ International Atomic Energy Agency (IAEA) (August 2015). "The Fukushima Daiichi Accident: Technical Volume 2/5 - Safety Assessment" (PDF). International Atomic Energy Agency (IAEA). p. 74. Retrieved 1 May 2017.
  7. ↑ International Atomic Energy Agency (IAEA) (August 2015). "The Fukushima Daiichi Accident: Technical Volume 1/5 - Description and Context of the Accident" (PDF). International Atomic Energy Agency (IAEA). p. 66. Retrieved 1 May 2017.
  8. ↑ B. Medvedev (June 1989). "JPRS Report: Soviet Union Economic Affairs Chernobyl Notebook" (Republished by the Foreign Broadcast Information Service ed.). Novy Mir. Archived from the original on 24 March 2011. Retrieved 27 March 2011.
  9. ↑ "Fukushima radiation level highest since March 11". The Japan Times Online. 3 February 2017.
  10. ↑ "Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine. The Chernobyl Forum: 2003–2005 Second revised version" (PDF). IAEA. 1 April 2006. Retrieved 25 April 2019.
  11. ↑ Three Mile Island, Chernobyl, and Fukushima, A comparison of three nuclear reactor calamities reveals some key differences. IEEE. 1 November 2011. doi:10.1109/MSPEC.2011.6056644.
  12. ↑ "Chernobyl Accident 1986". World Nuclear Association. 1 June 2013. Retrieved 25 April 2019.
  13. ↑ Steinhauser, Georg; Brandl, Alexander; Johnson, Thomas E. (2014). "Comparison of the Chernobyl and Fukushima nuclear accidents: A review of the environmental impacts". Science of the Total Environment. 470–471: 800–817. Bibcode:2014ScTEn.470..800S. doi:10.1016/j.scitotenv.2013.10.029. PMID 24189103.
  14. ↑ "ANNEX J. Exposures and effects of the Chernobyl accident" (PDF). United Nations UNSCEAR. 2000. Retrieved 27 June 2019.
  15. ↑ "Figure XI. Surface ground deposition of caesium-137 released in Europe after the Chernobyl accident [D13]" (PDF). United Nations UNSCEAR Report. 2000.
  16. ↑ "Figure VI. Surface ground deposition of caesium-137 released in the Chernobyl accident [I1, L3]" (PDF). United Nations UNSCEAR Report. 2000.
  17. ↑ "Fukushima: Radiation Exposure". World Nuclear Association. February 2016. Retrieved 4 February 2017.
  18. ↑ "Reconstruction Agency". www.reconstruction.go.jp. Retrieved 25 May 2016.
  19. ↑ "Fukushima Residents Return Despite Radiation". www.scientificamerican.com. Retrieved 6 October 2019.
  20. ↑ "Health effects due to radiation from the Chernobyl accident (Annex D of the 2008 UNSCEAR Report)" (PDF). UNSCEAR. 2011.
  21. ↑ "WHO | Chernobyl: The true scale of the accident".
  22. ↑ Kaushik, Kavyanjali (7 April 2011). "UPDATE 1-Toshiba proposes to scrap Fukushima nuclear plant-Nikkei". Reuters. Retrieved 27 July 2013.
  23. ↑ Justin Mccurry (10 March 2014). "Fukushima operator may have to dump contaminated water into Pacific". The Guardian. Retrieved 10 March 2014.
  24. ↑ Archived 2012-03-18 at the Wayback Machine2002, archived from Original on 20 April 2011, retrieved on 6 April 2011.
  25. ↑ Archived 14 September 2011 at the Wayback Machine(in German). ZAMG, 22 March 2011, archived from Original on 20 April 2011, retrieved on 20 April 2011.
  26. ↑ Archived 27 February 2012 at the Wayback Machine(in German). In: www.zamg.ac.at. Zentralanstalt für Meteorologie und Geodynamik, 2 April 2011, archived from Original on 20 April 2011, retrieved on 2 April 2011.
  27. 1 2 3 4 Archived 30 January 2012 at the Wayback Machine. JAIF / NHK, 26 April 2011, archived from Original on 27 April 2011, retrieved on 27 April 2011.
  28. 1 2 3 4 5 Archived 28 March 2012 at the Wayback Machine. NISA/METI, 12 April 2011, archived from Original on 12 April 2011, retrieved on 12 April 2011.
  29. 1 2 Archived 4 April 2012 at the Wayback Machine. NISA/Kantei, 7 June 2011, archived from Original, retrieved on 8 June 2011.
  30. ↑ Archived 19 April 2012 at the Wayback Machine. In: Atoms in Japan. JAIF, 5 September 2011, archived from Original, retrieved on 20 December 2011.
  31. ↑ Archived 30 January 2012 at the Wayback Machine. Kantei, 15 September 2011, archived from Original, retrieved on 17 December 2011. Spent fuel pool measurement on page 205, 207, 210 and 214; total release on page 449.
  32. 1 2 Archived 9 April 2011 at the Wayback Machine. NHK, 6 June 2011, archived from Original, retrieved on 6 June 2011.
  33. ↑ Archived 4 April 2012 at the Wayback Machine. NISA/Kantei, 7 June 2011, archived from Original, retrieved on 14 June 2011.
  34. ↑ Archived 30 January 2012 at the Wayback Machine. JAIF / NHK, 18 August 2011, archived from Original, retrieved on 21 August 2011. Converted from 200 MBq/h in a two-week period.
  35. ↑ Earthquake Report – JAIF, No. 182. JAIF / NHK, 23 August 2011, archived from Original Archived 2011-11-14 at the Wayback Machine, retrieved on 31 August 2011.
  36. ↑ Archived 26 May 2011 at the Wayback Machine. Tepco, 21 May 2011, archived from Original, retrieved on 23 May 2011.
  37. ↑ Dagmar Röhrlich: Archived 4 November 2011 at the Wayback Machine(in German). In: dradio.de, Forschung Aktuell. Deutschlandfunk, 5 September 2011, archived from Original, retrieved on 7 September 2011; 1 000 000 000 000 Becquerel = 1 TBq.
  38. ↑ Archived 19 April 2012 at the Wayback Machine. JAIF / NHK, 9 September 2011, archived from Original, retrieved on 11 December 2011.
  39. ↑ Archived 17 January 2012 at the Wayback Machine. JAIF / NHK, 30 November 2011, archived from Original, retrieved on 20 December 2011.
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