Chernobyl

Danny Cooke via YouTube

The Chernobyl disaster was the worst nuclear power plant accident in history in terms of cost and casualties,[1][2] and is one of only two classified as a level 7 event (the maximum classification) on the International Nuclear Event Scale (the other being the Fukushima Daiichi nuclear disaster in 2011).[1][3]

The disaster began during a systems test on Saturday, 26 April 1986 at reactor unit 4 of the Chernobyl plant.[1]

There was a sudden power surge, and when an emergency shutdown was attempted, an exponentially larger spike in power output occurred, which led to a reactor vessel rupture and a series of steam explosions.[1][4]

These events exposed the graphite moderator of the reactor to air, causing it to ignite.[1][4]    

The resulting fire sent a plume of highly radioactive fallout (300 times greater than from the Hiroshima atomic bomb)[5]  into the atmosphere. The plume drifted over large parts of the western Soviet Union and Europe.[1]

According to official post-Soviet data,[1][8][9][10] about 60% of the fallout landed in Belarus.

A simplified diagram of the major differences between the Chernobyl RBMK and the most common nuclear reactor design, the Light Water Reactor (LWR).
1. The use of a graphite moderator in a water cooled reactor.
2. A positive steam void coefficient that made the power excursion possible, which blew the reactor vessel.
3. The control rods took 18-20 seconds to be deployed. The control rods had graphite tips that moderated, and therefore increased the fission rate in the beginning of the rod insertion.
4. No reinforced containment building.[1][59][60][61]

The nuclear reactor after the disaster.
Reactor 4 (center).
Turbine building (lower left).
Reactor 3 (center right).[1]

The radiation levels in the worst-hit areas of the reactor building have been estimated to be more than 20,000 roentgens per hour. A lethal dose is around 500 roentgens over 5 hours.[1][11][12]

The fire inside reactor unit 4 continued to burn until 10 May 1986.[1][13]

The fire was extinguished by a combined effort of helicopters dropping over 5000 metric tons of sand, lead, clay, and neutron-absorbing boron onto the burning reactor, and the injection of liquid nitrogen. It is now known that virtually none of the neutron absorbents reached the core.[1][14] 

The abandoned city of Pripyat with Chernobyl plant
in the distance.[1]

The nearby city of Pripyat was not immediately evacuated after the incident. Later, they reported severe headaches and metallic tastes in their mouths, along with uncontrollable fits of coughing and vomiting.[1][15]

After evacuating the city of Pripyat, the following warning message was read on the state TV:

There has been an accident at the Chernobyl Nuclear Power Plant. One of the nuclear reactors was damaged. The effects of the accident are being remedied. Assistance has been provided for any affected people. An investigative commission has been set up.—Vremya, 28 April 1986 (21:00)[1][17]       

On the morning of 27 April, buses arrived in Pripyat to start the evacuation. By 15:00, 53,000 people had been evacuated.[1][18]   

By December 1986, an investigation had ruled out further risk of explosion, and a large concrete sarcophagus had been erected to seal off the reactor unit 4 and its contents.[1][14][19]
    

***

Approximately 100,000 km² of land was significantly contaminated with fallout, with the worst hit regions being in Belarus, Ukraine and Russia.[1][20] 

Sweden and Norway also received heavy fallout when the contaminated air collided with a cold front, bringing rain.[1][21]   

Earth Observing-1 image of the reactor and surrounding
area in April 2009.[1]

The Chernobyl nuclear power plant is located next to the Pripyat River, which feeds into the Dnieper reservoir system. The Dnieper, one of the largest surface water systems in Europe, was (at the time of the explosion) supplying water to Kiev's 2.4 million residents.[1][33]    

Massive silt traps were constructed, along with a 30m-deep underground barrier to prevent groundwater from the destroyed reactor entering the Pripyat River.[1][33] 


In the most affected areas of Ukraine, levels of radioactivity in drinking water caused concern during the weeks and months after the accident,[1][34] though officially it was stated that all contaminants had settled to the bottom "in an insoluble phase" and would not dissolve for 800–1000 years.[1][33]

Still, two months after the disaster, the Kiev water supply was switched from the Dnieper to the Desna River.[1][33] 

1 Becquerel (Bq) = 1 event of radiation emission per second.[63]

The Sievert (Sv), is the unit of radiation absorption in the International System of Units (SI). The Sievert takes into account the relative biological effectiveness (RBE) of ionizing radiation, since each form of such radiation—e.g., X-rays, gamma rays, neutrons—has a slightly different effect on living tissue.[64]

10 Sv - Risk of death within days or weeks.[63]

1 Sv - Risk of cancer later in life (5 in 100).[63]

Guideline maximum levels for radio-caesium in fish vary from country to country but are approximately 1000 Bq/kg in the European Union.[1][35]   

In small "closed" lakes in Belarus and the Bryansk region of Russia, concentrations in a number of fish species varied from 100 to 60,000 Bq/kg during the period 1990–92.[1][36][37]  

After the disaster, four square kilometers of
pine forest directly downwind of the reactor
turned reddish-brown and died, earning the
name of the "Red Forest".[62]

After the disaster, 4 square kilometers of pine forest directly downwind of the reactor turned reddish-brown and died, earning the name of the "Red Forest".[1][39]  

A robot sent into the reactor itself returned with samples of black, melanin-rich radiotrophic fungi that are growing on the reactor's walls.[1][41]

Some animals in the worst-hit areas also died or stopped reproducing. Horses left on an island in the Pripyat River 6 km from the power plant died when their thyroid glands were destroyed by radiation doses of 150–200 Sv.[1][40]

Some cattle on the same island died and those that survived were stunted because of thyroid damage. The next generation appeared to be normal.[1][40]  

Piglet with dipygus at Ukrainian National
Chernobyl Museum in Kiev.[1]

On farms in Narodychi District of Ukraine, in the first four years of the disaster. nearly 350 animals were born with gross deformities such as missing or extra limbs, missing eyes, heads or ribs, or deformed skulls; in comparison, only three abnormal births had been registered in the five years prior.[1][22][23][24][25][26][27]

Of the 440,350 wild boar killed in the 2010 hunting season in Germany, over 1000 were found to be contaminated with levels of radiation above the permitted limit of 600 becquerels per kilogram, due to residual radioactivity from Chernobyl.[1][42]  

1,914 sheep located in 18 of Norway’s municipalities still needed to be given uncontaminated feed for a period of time before slaughter during 2012. This was a decrease from the 117 municipalities initially affected during 1986.[1][43]  

In the United Kingdom In the immediate aftermath of the disaster in 1986, a total of 4,225,000 sheep had their movement restricted across a total of 9,700 farms, in order to prevent contaminated meat entering the human food chain.[1][44] 

The restrictions applying in Scotland were lifted in 2010, whilst those applying to Wales and Cumbria were lifted during 2012, meaning no farms in the UK remain restricted because of Chernobyl fallout.[1][45][46] 

Iodine-131 and caesium-137 are responsible for most of the radiation exposure received by the general population.[1][28][29][30][31]   

In the aftermath of the accident, 237 people suffered from acute radiation sickness (ARS), of whom 31 died within the first three months.[1][10][32]

The 2005 Chernobyl Forum[47] report revealed thyroid cancer among children to be one of the main health impacts. In that publication more than 4000 cases were reported. The report also noted an increase in psychological problems among the affected population.[1][48]   Dr Michael Repacholi, manager of WHO's Radiation Program reported that the 4000 cases of thyroid cancer resulted in nine deaths.[1][49] 

Since 1991 large social and political changes have occurred within the affected regions and these changes have had significant impact on the administration of health care, on socio-economic stability, and the manner in which statistical data was collected in the years following the disaster.[1][50]

***

The three remaining reactor units—vital to Ukraine's electricity needs—continued to operate for some years.[58]

In 1991, a fire broke out in the turbine building of unit 2; [1][51] the authorities subsequently declared the unit damaged beyond repair and was taken offline.

Reactor unit 1 was decommissioned in November 1996 as part of a deal between the Ukrainian government and international organizations such as the International Atomic Energy Agency (IAEA) to end operations at the plant.[1]

On 15 December 2000, then-President Leonid Kuchma personally turned off reactor unit 3 in an official ceremony, shutting down the entire site.[1][52]  

Two years later, roughly 15,000 Ukrainian workers were still working within the Zone of Exclusion, maintaining the plant and performing other containment- and research-related tasks.[1][53] 

On 12 February 2013 a 600 m2 section of the roof of the turbine-building, adjacent to the sarcophagus, collapsed.[1][56][57] 

Entrance to the sealed zone around Chernobyl[1]

In 2011 Ukraine opened up the sealed zone around the Chernobyl reactor to tourists who wish to learn more about the tragedy that occurred in 1986.[1][54][55] 

   

The following excerpt is from, Decommissioning of Chernobyl Units Approaches | February 2014 | World Nuclear News:[58]

"Work to bring units 1 to 3 into care and maintenance will be carried out in six stages between 2014 and 2028. … For the period between 2028 and 2046, the most contaminated equipment will be removed from the units, while the reactors themselves will be dismantled between 2046 and 2064. … The decommissioning of units 1-3 is being carried out separately from that of the destroyed unit 4, which is expected to take many years longer to complete."

***

Fin

Updates & Related

Chernobyl: At site of world's worst nuclear disaster, the animals have returned / Science Daily / October 5, 2015

View The Ruins of Chernobyl by Drone Popular Science / December 1, 2014

Rise in Wildfires May Resurrect Chernobyl's Radiation / New Scientist / February 9, 2015

Chernobyl Trees Barely Decompose, Study Finds / Live Science / March 24, 2014

References 

[1] http://en.wikipedia.org/wiki/Chernobyl_disaster

[2] Nuclear and radiation accidents#Nuclear power plant accidents

[3] Black, Richard (12 April 2011). "Fukushima: As Bad as Chernobyl?". BBC. 

[4] "Table 2.2 Number of people affected by the Chernobyl accident (to December 2000)" (PDF). The Human Consequences of the Chernobyl Nuclear Accident. UNDP and UNICEF. 22 January 2002. p. 32.

[5] BBC - Horizon – Series 32 “Fall Out From Chernobyl” - (April 1996)

[6] "Table 5.3: Evacuated and resettled people" (PDF).The Human Consequences of the Chernobyl Nuclear Accident. UNDP and UNICEF. 22 January 2002. p. 66. 

[7] ICRIN Project (2011). International Chernobyl Portal chernobyl.info. 

[8] Environmental consequences of the Chernobyl accident and their remediation: Twenty years of experience. Report of the Chernobyl Forum Expert Group ‘Environment’. Vienna: International Atomic Energy Agency. 2006. p. 180.ISBN 92-0-114705-8. 

[9] "Assessing the Chernobyl Consequences". International Atomic Energy Agency.

[10] "Chernobyl: the true scale of the accident". Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts. 

[11] "Cross-sectional view of the RBMK-1000 main building". 

[12] A. S. Djatlov:31; 247–48

[13] (January 1996). "DOE Fundamentals Handbook – Nuclear physics and reactor theory" (PDF). 1 of 2, module 1. United States Department of Energy. 61-73

[14] Zeilig, Martin (August–September 1995). "Louis Slotin And 'The Invisible Killer'". The Beaver 75 (4): 20–27. 

[15] (Russian) Video footage of Chernobyl disaster on 28 April on YouTube

[16] Schmemann, Serge (1986-04-29). "Soviet Announces Nuclear Accident at Electric Plant". The New York Times. pp. A1.

[17] American TV-footage about Chernobyl

[18] (Ukrainian) Presidential Decree #501/2011 "For distinguishing with the state awards of Ukraine"

[19] Collecting History (1986-04-26). "Medal for Service at the Chernobyl Nuclear Disaster". Collectinghistory.net. 

[20 ] "Tchernobyl, 20 ans après" (in French). RFI. 24 April 2006.

[21] Gray, Richard (22 April 2007). "How we made the Chernobyl rain". Telegraph (London) 43–44, 78

[22] Wertelecki, W. (2010). "Malformations in a Chornobyl-Impacted Region". Pediatrics 125 (4): e836–43.doi:10.1542/peds.2009-2219. PMID 20308207.

[23] Dancause, Kelsey Needham; Yevtushok, Lyubov; Lapchenko, Serhiy; Shumlyansky, Ihor; Shevchenko, Genadiy; Wertelecki, Wladimir; Garruto, Ralph M. (2010). "Chronic radiation exposure in the Rivne-Polissia region of Ukraine: Implications for birth defects". American Journal of Human Biology 22 (5): 667–74. doi:10.1002/ajhb.21063.PMID 20737614.

[24] Møller, Anders Pape (April 1998). "Developmental Instability of Plants and Radiation from Chernobyl". Oikos(Nordic Ecological Society) 81 (3): 444–48.doi:10.2307/3546765. JSTOR 3546765

[25] Saino, N.; Mousseau, F.; De Lope, T. A.; Saino, A. P. (2007). "Elevated frequency of abnormalities in barn swallows from Chernobyl". Biology Letters 3 (4): 414–17.doi:10.1098/rsbl.2007.0136. PMC 1994720.PMID 17439847.

[26] Weigelt, E.; Scherb, H. (2004). "Spaltgeburtenrate in Bayern vor und nach dem Reaktorunfall in Tschernobyl".Mund-, Kiefer- und Gesichtschirurgie 8 (2): 106.doi:10.1007/s10006-004-0524-1.

[27] Bennett, Burton; Repacholi, Michael; Carr, Zhanat, eds. (2006). Health Effects of the Chernobyl Accident and Special Health Care Programmes: Report of the UN Chernobyl Forum, Expert Group "Health" (PDF). Geneva: World Health Organization (WHO). ISBN 978-92-4-159417-2. 

[28] Chapter II The release, dispersion and deposition of radionuclides - Chernobyl: Assessment of Radiological and Health Impact. Oecd-nea.org. 

[29] Chernobyl source term, atmospheric dispersion, and dose estimation, EnergyCitationsDatabase, 1 November 1989.

[30] Cesium-137: A Deadly Hazard. Large.stanford.edu (2012-03-20).

[31] Mould 2000, p. 29. "The number of deaths in the first three months were 31[.]"

[32] Marples, David R. (1988). The Social Impact of the Chernobyl Disaster. New York, NY: St Martin’s Press.

[33] Chernobyl: Catastrophe and Consequences, Springer, Berlin ISBN 3-540-23866-2 p. 60-67.

[34] Kryshev, I.I. (1995). "Radioactive contamination of aquatic ecosystems following the Chernobyl accident".Journal of Environmental Radioactivity 27 (3): 207.doi:10.1016/0265-931X(94)00042-U.

[35] Fleishman, David G.; Nikiforov, Vladimir A.; Saulus, Agnes A.; Komov, Victor T. (1994). "137Cs in fish of some lakes and rivers of the Bryansk region and north-west Russia in 1990–1992". Journal of Environmental Radioactivity 24 (2): 145. doi:10.1016/0265-931X(94)90050-7.

[36] EURATOM Council Regulations No. 3958/87, No. 994/89, No. 2218/89, No. 770/90

[37] "Environmental consequences of the Chernobyl accident and their remediation" PDF IAEA, Vienna

[38] Wildlife defies Chernobyl radiation, by Stefen Mulvey, BBC News

[39] The International Chernobyl Project Technical Report, IAEA, Vienna, 1991.

[40] "'Radiation-Eating' Fungi Finding Could Trigger Recalculation Of Earth's Energy Balance And Help Feed Astronauts".

[41] "25 Jahre Tschernobyl: Deutsche Wildschweine immer noch verstrahlt – Nachrichten Wissenschaft – WELT ONLINE". Die Welt (in German). 18 March 2011. 

[42] "Record low number of radioactive sheep". The Local(The Local Europe AB). 23 September 2013. 

[43] "Fortsatt nedforing etter radioaktivitet i dyr som har vært på utmarksbeite – Statens landbruksforvaltning". SLF. 30 June 2010. 

[44] Rawlinson, Kevin; Rachel Hovenden (7 July 2010)."Scottish sheep farms finally free of Chernobyl fallout".The Independent. 

[45]  "Post-Chernobyl disaster sheep controls lifted on last UK farms". BBC News (BBC). 1 June 2012. Retrieved1 November 2013.

[46]  Food Standards Agency (29 November 2012). "Welsh sheep controls revoked". 

[47] "Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts". Chernobyl Forum assessment report. Chernobyl Forum. .

[48] Chernobyl: the true scale of the accident, Joint News Release WHO/IAEA/UNDP, 5 SEPTEMBER 2005

[49] "UNSCEAR – Chernobyl health effects". Unscear.org. 

[50] Shlyakhter, Alexander; Wilson, Richard (1992). "Chernobyl andGlasnost: The Effects of Secrecy on Health and Safety".Environment: Science and Policy for Sustainable Development 34 (5): 25.

[51] IAEA's Power Reactor Information System polled in May 2008 reports shutdown for units 1, 2, 3 and 4 respectively at 30 November 1996, 11 October 1991, 15 December 2000 and 26 April 1986.

[52] Чернобыль, Припять, Чернобыльская АЭС и зона отчуждения. ""Shelter" object description". Chornobyl.in.ua.

[53] "Information Notice No. 93–71". Nrc.gov.

[54] "Tours of Chernobyl sealed zone officially begin". TravelSnitch. TravelSnitch. 18 March 2011.

[55]  "NOVARKA and Chernobyl Project Management Unit confirm cost and time schedule for Chernobyl New Safe Confinement". 8 April 2011.

[56]  Ukraine: Chernobyl nuclear roof collapse 'no danger', BBC News, 13 February 2013

[57] Baryakhtar, V.; Gonchar, V.; Zhidkov, A.; Zhidkov, V. (2002). "Radiation damages and self-sputtering of high-radioactive dielectrics: spontaneous emission of submicronic dust particles". Condensed Matter Physics 5 (3{31}): 449–471. doi:10.5488/cmp.5.3.449.

[58] http://www.world-nuclear-news.org/WR-Decommissioning-of-Chernobyl-units-approches-1902144.html

[59] "INSAG-7 The Chernobyl Accident: Updating of INSAG-1" (PDF).
[60] "Chernobyl - Assessment of Radiological and Health Impacts" (PDF).
[61] Chernobyl Accident
[62] Wildlife defies Chernobyl radiation, by Stefen Mulvey, BBC News

[63] http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html

[64] http://www.britannica.com/EBchecked/topic/543504/sievert-Sv

Other Resources

http://www.telegraph.co.uk/news/worldnews/europe/germany/11068298/Radioactive-wild-boar-roaming-the-forests-of-Germany.html

http://www.nbcnews.com/news/world/chernobyl-disaster-leaves-radioactive-wild-boars-roaming-germany-n193596

“Chernobyl Pig” https://www.youtube.com/watch?v=Q8Isr-BtKvI

http://en.wikipedia.org/wiki/Pripyat

Image Credits

"Chernobyl Disaster" by Soviet Authorities. Via Wikipedia - http://en.wikipedia.org/wiki/File:Chernobyl_Disaster.jpg#mediaviewer/File:Chernobyl_Disaster.jpg

"View of Chernobyl taken from Pripyat zoomed" by Jason Minshull - Image:View of Chernobyl taken from Pripyat.JPG. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:View_of_Chernobyl_taken_from_Pripyat_zoomed.JPG#mediaviewer/File:View_of_Chernobyl_taken_from_Pripyat_zoomed.JPG

"Chernobyl-LWR-comparison" by Tungsten - self-made, data from IAEA: INSAG-7 The Chernobyl Accident: Updating of INSAG-1. Vienna, 1992; NEA:Chernobyl - Assessment of Radiological and Health Impacts. Pariisi, 2002; Nakao, M.: Chernobyl Accident. University of Tokyo, 2006.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Chernobyl-LWR-comparison.PNG#mediaviewer/File:Chernobyl-LWR-comparison.PNG

"Kiev-UkrainianNationalChernobylMuseum 15" by Vincent de Groot - http://www.videgro.net - Own work. Licensed under GFDL via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Kiev-UkrainianNationalChernobylMuseum_15.jpg#mediaviewer/File:Kiev-UkrainianNationalChernobylMuseum_15.jpg

"Red Forest Hill" by Timm Suess - Flickr: Red Forest Hill. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Red_Forest_Hill.jpg#mediaviewer/File:Red_Forest_Hill.jpg

"Entrance to zone of alienation around Chernobyl" by Slawojar - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Entrance_to_zone_of_alienation_around_Chernobyl.jpg#mediaviewer/File:Entrance_to_zone_of_alienation_around_Chernobyl.jpg

"VOA Markosian - Chernobyl02" by VOA Photo / D. Markosian - D. Markosian: One Day in the Life of Chernobyl, VOA News, photo gallery.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:VOA_Markosian_-_Chernobyl02.jpg#mediaviewer/File:VOA_Markosian_-_Chernobyl02.jpg

"Chernobyl, Ukraine" by Jesse Allen - NASA Earth Observatory. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Chernobyl,_Ukraine.jpg#mediaviewer/File:Chernobyl,_Ukraine.jpg