chernobyl disaster

Chernobyl Disaster

Dr Nik Nor Ronaidi bin Nik Mahdi

Chernobyl Disaster: The Worst Nuclear Disaster in History

100 times more radioactivity than Hiroshima

Where is Chernobyl?

http://students.vassar.edu/mezegen/Eastern%20Europe%20Map.gif

-In Northern Ukraine-10 miles away from Belarus-80 miles North of Kiev

http://studiohousebooks.co.uk/chernobyl/Chernobyl/chernobyl.html

The Chernobyl Nuclear Power Plant• Located 11 miles north of the city of Chernobyl• Plant consisted of 4 reactors• Produced 10% of Ukraine’s electricity• Construction began in the 1970’s• Reactor #4 was completed in 1983• At the time of the accident, reactors #5 and #6 were in progress.

http://www.rotten.com/library/history/nuclear-incidents/chernobyl

Background

• Type: Reaktor Bolshoy Moshehnosty Kipyashiy (RBMK)

• RBMK, a Russian acronym translated roughly means “reactor (of) high power (of the) channel (type)”

• reactor cooled by water and moderated by graphite

Reactor Schematic

Reactor Plant Scenario1. As the reaction occurs, the uranium fuel becomes

hot2. The water pumped through the core in pressure

tubes removes the heat from the fuel3. The water is then boiled into steam4. The steam turns the turbines5. The water is

then cooled6. Then the process

repeats

What happened?

http://www.ukrainianweb.com/images/chernobyl/chernobyl_reactor.jpg

Saturday, April 26, 1986:

-Reactor #4 was undergoing a test to test the backup power supply in case of a power loss. -The power fell too low, allowing the concentration of xenon-135 to rise.

-The workers continued the test, and in order to control the rising levels of xenon-135, the control rods were pulled out.

What happened? cont’d-The experiment involved shutting down the coolant pumps, which

caused the coolant to rapidly heat up and boil.

-Pockets of steam formed in the coolant lines. When the coolant expanded in this particular design, the power level went up.

-All control rods were ordered to be inserted. As the rods were inserted, they became deformed and stuck. The reaction could not be stopped.

-The rods melted and the steam pressure caused an explosion, which blew a hole in the roof. A graphite fire also resulted from the explosion.

-To save money, the reactor was constructed with only partial containment, which allowed the radiation to escape.

This dispersed large amount of radioactive particulate and gaseous debris containing cesium-137 and strontium-90 which are highly radioactive reactor waste product.

– Workers lack of knowledge of reactor physics and engineering, as well as lack of experience and training

• Delay• The night shift was not prepared to carry

out the experiment • But it was still carried out• The operators seem to have been unaware

of the xenon poisoning

– Insufficient communication between the safety officers and the operators in charge of the experiment

– Disabled all safety systems– Poor quality (typical Soviet

craftsmanship)• Rushed design• A lot of corners cut to meet deadline

– Bonus for meeting deadline

Reasons for the accident

The Reactor After the Explosion

After the explosion, most of the plant is still standing. Some might think from this picture that the disaster wasn’t all that bad, but what makes the Chernobyl disaster the worst in history is the sheer volume of radioactive materials that where spewed across the European continent.

Summary of Facts• April 26, 1986:

– Chernobyl nuclear power plant

• Operator errors cause a reactor explosion

• Explosion releases 190 tons of radioactive gasses into the atmosphere

• Fire starts that lasts 10 days

• People: – 7 million lived in

contaminated areas; 3 million were children

• Wind:– Carries radiation far distances

Chernobyl Catastrophe Victims comprise four main groups

•Group 1: persons involved in the clean-up operations at the Chernobyl Nuclear Plant (liquidators).

•Group 2: Persons evacuated from the exclusion zone in 1986 (evacuees)

•Group 3: Persons resident in the territories monitored (relocation zone) or resident there immediately after the accident (residents)

•Group 4: Children born to parents in Groups 1-3 (offspring).

Immediate Impact

- 231 people were hospitalized immediately due to acute radiation sickness.

- 31 of them eventually died. Most of these people were workers in the plant or local firefighters.

http://www.cmc.ec.gc.ca/~arqidor/ctbto/ctbt3.html

http://er1.org/docs/photos/Disaster/Chernobyl%2002%20robotic%20inspector.jpghttp://www.chernobyl-international.com/aboutchernobyl/fateoftheliquidators.asp

• “Liquidators”– These were firemen who helped

put out the fires and helped clean up the radiation

– Most did not realize the dangers of radiation.

– Many later died from radiation, because they didn’t wear protection.

– An estimated 8,000-20,000 to date have died (20% from suicide)

• Robots– United States supplied– Specifically designed to enter

reactor core and help build the sarcophagus

The Clean Up

Clean Up

http://library.thinkquest.org/3426/data/emergency/cleanup.efforts.html

Approximately 300,000 to 600,000 liquidators were involved in the cleanup of the 30 km evacuation zone around the plant in the years following the meltdown.

Evacuation-Following the accident hundreds of thousands of people had to be evacuated and between 1990 and 1995 an additional 210,000 people were resettled.

People evacuated:-May 2-3 (1 week later)

10 km area (45,000 people)

-May 4 30 km area (116,000

people)

http://library.thinkquest.org/3426/data/emergency/evacuation.html

-50,000 people from Pripyat, Ukraine were evacuated 2 days after the accident.

Long term Impact• International spread of radioactivity

– detected over all of Europe except for the Iberian Peninsula

– The nuclear meltdown provoked a radioactive cloud which floated over Russia, Belarus, Ukraine and Moldova, but also the European part of the Republic of Macedonia, Croatia, Turkey, Bulgaria, Greece, Romania, Lithuania, Latvia, Finland, Denmark, Norway, Sweden, Austria, Hungary, the Czech Republic and the Slovak Republic, Slovenia, Poland, Switzerland, Germany, Italy, Ireland, France and the United Kingdom (UK).

Long term Impact (cont)• Radioactive release

– Highly radioactive compounds that accumulate in the food chain, such as some isotopes of iodine and strontium are particularly dangerous.

– All of the noble gases, including krypton and xenon, contained within the reactor were released immediately into the atmosphere by the first steam explosion.

– About 55% of the radioactive iodine in the reactor was released, as a mixture of vapor, solid particles and as organic iodine compounds.

– Plutonium’s half life is 24,400 years.

Cycle of Radioactive Materials

• Residual radioactivity in the environment– Rivers, lakes and reservoirs

• Levels of radioactivity (particularly radioiodine: I-131, radiocaesium: Cs-137 and radiostrontium: Sr-90) in drinking water caused concern during the weeks and months after the accident.

• Bio-accumulation of radioactivity in fish were significantly above guideline maximum levels for consumption

– Groundwater• Groundwater was not badly affected since radionuclides with

short half-lives decayed away a long time before they could affect groundwater supplies, and longer-lived radionuclides such as radiocaesium and radiostrontium were adsorbed to surface soils before they could transfer to groundwaters

Long term Impact (cont)

– Fauna and vegetation• pine forest in the 10km2 surrounding of the reactor turned

ginger brown and died, earning the name of the "Red Forest“• Some animals in the worst-hit areas also died or stopped

reproducing.


Socio Economical impact• The affected territories are mostly rural. • The main source of income before the accident

was agriculture• The agricultural sector was the area of the

economy worst hit by the effects of the accident.• A total of 784 320 hectares of agricultural land

was removed from service in the three countries, and timber production was halted for a total of 694 200 hectares of forest.


Socio Economical impact• Restrictions on agricultural production crippled

the market for foodstuffs and other products from the affected areas.

• Even where remediation measures have made farming safe, the stigma of Chernobyl has caused some consumers to reject products from affected areas.


• Health Effects– Thyroid cancers

• A large increase in the incidence of thyroid cancer has occurred among young children and adolescents at the time of the accident and lived in the most contaminated areas of Belarus, the Russian Federation and Ukraine.

• This was due to the released of high levels of radioactive iodine

• Radioactive iodine was deposited in pastures eaten by cows who then concentrated it in their milk which was subsequently drunk by children


• Health effects– Leukaemia and non-thyroid solid cancer

• Ionizing radiation is a known cause of certain types of leukaemia (a malignancy of blood cells).

• An elevated risk of leukaemia was first found among the survivors of the atomic bombings in Japan some two to five years after exposure.

• Recent investigations suggest a doubling of the incidence of leukaemia among the most highly exposed Chernobyl liquidators.

• Reports indicate a small increase in the incidence of pre-menopausal breast cancer in the most contaminated areas, which appear to be related to radiation dose.

• Need confirmation in well-designed epidemiological studies.


• Health effects– Cataracts

• The lens of the eye is very sensitive to ionizing radiation and cataracts are known to result from effective doses of about 2 Sv.

• The production of cataracts is directly related to the dose. The higher the dose the faster the cataract appears.

• Chernobyl cataract studies suggest that radiation opacities may occur from doses as low as 250 mSv.

– Cardiovascular disease• A large Russian study among emergency workers has suggested

an increased risk of death from cardiovascular disease in highly exposed individuals.

• While this finding needs further study with longer follow-up times, it is consistent with other studies, for example, on radiotherapy patients, who received considerably higher doses to the heart.


• Health effects– Mental health and psychological effects

• High levels of stress, anxiety and medically unexplained physical symptoms continue to be reported among those affected by the accident.

– Reproductive and hereditary effects and children's health

• Birth defects, infertility


Economic cost• The scale of the burden is clear from the wide range of costs

incurred, both direct and indirect:– Direct damage caused by the accident;– Expenditures related to:

• Actions to seal off the reactor and mitigate the consequences in the exclusion zone;

• Resettlement of people and construction of new housing and infrastructure to accommodate them;

• Social protection and health care provided to the affected population; • Research on environment, health and production of clean food; • Radiation monitoring of the environment; and • Radioecological improvement of settlements and disposal of radioactive waste.

– Indirect losses relating to the opportunity cost of removing agricultural land and forests from use and the closure of agricultural and industrial facilities; and

– Opportunity costs, including the additional costs of energy resulting from the loss of power from the Chernobyl and the cancellation of Belarus’s nuclear power programme.

Economic cost (cont)• Coping with the impact of the disaster has placed a

huge burden on national budgets. • In Ukraine, 5–7 % of government spending each

year is still devoted to Chernobyl-related benefits and programmes.

• In Belarus, government spending on Chernobyl amounted to 22.3% of the national budget in 1991, declining gradually to 6.1% in 2002. Total spending by Belarus on Chernobyl between 1991 and 2003 was more than USD 13 billion.

What has been done to reduce exposure in contaminated areas?

• The Soviet and Commonwealth of Independent States (CIS) authorities introduced a wide range of short and long term environmental countermeasures to mitigate the accidents negative consequences:– Decontamination of settlements in contaminated regions– Exclusion of contaminated pasture grasses from animal

diets and rejection of milk based on radiation monitoring data.

– Feeding animals with “clean” fodder– Application of Cs-binders, such as Prussian blue, to prevent

contamination of milk and meat

What has been done to reduce exposure in contaminated areas?

• Restrictions:– Restrictions on public and forest worker access as a

countermeasure against external exposure; – Restricted harvesting of food products such as game, berries and

mushrooms by the public that contributed to reduction of internal doses. In the CIS countries mushrooms are a staple of many diets and, therefore, this restriction has been particularly important;

– Restricted collection of firewood by the public to prevent exposures in the home and garden when the wood is burned and the ash is disposed of or used as a fertilizer; and

– Alteration of hunting practices aiming to avoid consumption of meat with high seasonal levels of radiocaesium.

– restriction of drinking water and changing to alternative supplies.– Restrictions on consumption of freshwater fish

Lessons learned from Chernobyl • The scale of the material and the financial losses in mitigating the

consequences of the Chernobyl accident provide compelling evidence of the extremely high price of errors and shortcomings when ensuring the safety of nuclear power plants and of the need for strict compliance with international safety requirements during their design, construction and operation.

• The cost of ensuring the safety of nuclear facilities is significantly lower than that of dealing with accident consequences. Large-scale man-made accidents cause great social and economic damage to countries located in their area of influence. Hundreds of billions of US dollars’ worth of direct and indirect damages have been reported by Belarus, Russia and Ukraine as a result of the Chernobyl nuclear power plant accident over the past 20 years.

• The accident has shown the importance of strict compliance with the basic and technical safety principles for nuclear power plants, of continuous safety analysis of operating nuclear power plants and of their early upgrading in order to eliminate deviations, of active study and the introduction of leading world experience, and of taking thorough account of the human factor.

• The accident has demonstrated the need to establish and support a high-level national emergency response system in case of man-made accidents.

Lessons learned from Chernobyl

THaNK YoU

Content

• Chronology - The site and accident sequence• The release and nature of radionuclide• Estimation of exposure• Human health effects – clinical manifestation

and acute vs chronic effects• Agricultural and environmental impacts• Potential residual risks• Lessons learnt• Studies done related to Chernobyl disaster

chernobyl disaster

Technology