BackgroundHappened in April 26, 1986 at

1:23a.m.

has been called the biggest socio-economic catastrophe in peacetime

history

50% of the area of Ukraine is in some way contaminated

Over 200,000 people had to be evacuated and resettled while 1.7 million people were directly affected by the

disaster

The death toll attributed to Chernobyl , including people who died from cancer

years later, is estimated at 125,000

The total costs including cleanup, resettlement, and compensation to

victims has been estimated to be roughly $200 Billion

Reason of the accident

-officially attributed to power plant operators who violated plant procedures and were

ignorant of the safety requirements needed.

Figure: The Chernobyl nuclear plant in Ukraine, apparently after they started to build the sarcophagus in the aftermath of the disaster. The nuclear disaster itself had

happened on 26 of April 1986.

Chernobyl AccidentThe worst commercial nuclear accident in history occurred during a test at the Chernobyl nuclear power plant.

lies near the Belarus-Ukraine border

The plant's Unit 4 reactor was rocked by a steam explosion,

Followed by a hydrogen explosion and a fire resulting in temperatures over 2,000°C. 

The 1,000 ton reactor lid was blown off the core, the nuclear fuel rods melted

More than 100 times the radiation of Hiroshima and Nagasaki combined was released into the atmosphere over the 10 days that the fire burned.

Many of the small towns and villages close to Chernobyl were rendered uninhabitable

Radioactive fallout from the accident was detected all over Europe. 

Figure: There is an “Exclusion Zone” of 30km (19 miles) radius surrounding the destroyed reactor ( which was located nearer to Pripyat than Chernobyl).

Officially, nobody is allowed to live in “Exclusion Zone”.

FIGURE: LOCATION OF CHERNOBYL

Figure: Reactor 4, Chernobyl Nuclear Power Plant, Ukraine

The Reactor and Accident in Chernobyl-4

Disabling of automatic shutdown mechanisms, preceded the attempted test early on 26 April.

Plants known to be very unstable at low power settings.

Reactor crew preparing for a test to determine how long turbines would spin and supply power following a loss of

main electrical power supply

Releasing fission products to the atmosphere

The fuel elements ruptured and the resultant explosive force of steam lifted off the cover plate of the reactor

When the operator moved to shut down the reactor from its unstable condition arising from previous errors, a peculiarity

of the design caused a dramatic power surge.

As flow of coolant water diminished, power output increased.

A total of about 14 EBq (1018 Bq) of radioactivity was released, half of it being biologically-inert noble gases.

Over 1200 tonnes of Graphite - burned for 9 days, causing the main release of radioactivity into the environment.

Causing the graphite moderator to burst into flames.

Second explosion threw out fragments of burning fuel and graphite from the core and allowed air to rush in

Figure: Reactor diagram.

Figure: The damaged Chernobyl unit 4 reactor building

Summary

Figure : The events are summarized in the reactor power/chronology.

Cause of Chernobyl

Two official explanations of the Chernobyl accident:

-Flawed operators explanation

-Operators were not informed about problems

with the reactor

Flawed operating explanation

• Having a mistake or weakness• Ignorant of safety requirement• Lack of experience and training• Insufficient communication• Overconfident : only normal electrical test • Choosing cheapness over safety

Second factor is the operators were not informed about problems with the reactor.

The designers knew that the reactor was dangerous in some conditions but intentionally

concealed this information.

The Chernobyl accident in 1986 was the result of a flawed reactor design that was

operated with inadequately trained personnel and without proper regard for

safety

Apart from that the two official explanations, the causes of the accident is say to be cause

by the poor design of the plant.

Poor Design of Plant• Partial containment was bypassed

and went out on the top of reactor core.•Hot fuel and graphite were exposed to air

•Cesium and radioactive Iodine

Poor Design Of Plant(Partial Containment)

FACTThe April 1986 disaster at the Chernobyl nuclear power plant in the Ukraine was the product of a flawed Soviet reactor

Design coupled with serious mistakes made by the plant operators in the context of a system where training was minimal.It was a direct consequence of Cold War isolation and the resulting lack of any safety culture.

The precise causes of the accident are still uncertain, but it is generally believed that

the series of incidents that led to the explosion, fire and nuclear meltdown at

Chernobyl was caused by a combination of reactor design flaws and operator error.

The explosion at Chernobyl acted like a volcano, blowing radioactive particles far

into the sky.

(a) International Spread of Radioactivity

Wind moved the plume, or cloud of radioactive particles, all around the world.

Even worse, when the plume passed by several countries, it began to rain, and

nuclear fallout hit the ground.

Large areas of Belarus, Ukraine, Russia and beyond were contaminated in varying

degrees.

(b) Health of Plant WorkersAccording to Ukrainian health ministry officials,

125,000 people have died as a result of the accident, and more deaths are expected.

In the aftermath of the accident, 237 people suffered from acute radiation sickness. Most of these were fire and rescue workers trying to bring the accident under control

Two people died in the initial steam explosion, but most deaths from the accident were attributed to radiation.

135,000 people were evacuated from the area, including 50,000 from Pripyat.

Most of them received high doses of radiation, average around 100 mSv. Some 20,000 of them received about 250 mSv and a few received 500 mSv.

(c) Delayed Health Effects

Man and young boy operated for thyroid cancer after Chernobyl nuclear accident.

Paralyzing fatalism

One of the most delayed effects of the radiation is the induction of cancer.

For example: Solid cancers among Russian liquidators whom exposed to more than 150 mSv.

The people in the area of contamination have suffered a paralyzing fatalism.

Mutation in newly born children

The topic of the children of Chernobyl is most shocking and awful.

By year 2000, about 4000 cases of thyroid cancer had been diagnosed in exposed children.

These children have to take painful procedures every day to postpone the fatal moment.

Chromosome aberrations causing mutations.

The increase in leukemia is even worse where there are dozens of cases of leukemia among the children.

The radioactive contamination of aquatic systems therefore became a major issue in the immediate aftermath of the

accident.

(d) Residual Radioactivity In The EnvironmentRivers, lakes and reservoirs

The Chernobyl nuclear power plant lies next to the Pripyat River which feeds into the Dnieper River reservoir system, one of the largest surface water systems in Europe.

In the most affected areas of Ukraine, levels of radioactivity in drinking water caused concern during the weeks and

months after the accident.

Groundwater

Groundwater was not badly affected by the Chernobyl accident since radionuclides with short half-lives decayed away a long time before they

could affect groundwater supplies.

Longer-lived radionuclides such as radiocaesium and radiostrontium were adsorbed to surface soils

before they could transfer to groundwaters.

Flora and fauna(i)Flora• After the disaster, four square kilometres of pine forest in the

immediate vicinity of the reactor turned ginger brown and died, earning the name of the “Red Forest”

• Local pine trees grow huge pine cones, pine needles of the needle-like leaves 10 times heavier than normal.

• Some fruits and vegetables also affect which causes the oddly shaped of potato, tomato and so on.

Flora and fauna(ii) Fauna• Radiation has affected animals living near the site of

Ukraine's Chernobyl nuclear disaster.• A major effect on the livestock was mutation.• The livestock was culled and buried.

Figure above: A cow that experiencing mutations. This co

having a cleft lip.

Figure above: These animals suffering from a serious effect of

mutation

Apartment buildings swimming pools, hospitals and other buildings were all abandoned, and everything

inside the buildings were left behind, including records, papers, TVs, children's

toys, and clothing, etc.

Residents were only allowed to take away a suitcase full of documents, books and clothes that were not

contaminated.

Many factory and farms stopped.

The whole site was shutdown.

People were facing homelessness .

(e) Normal Life and Work

(f) Cost

The accident, about US$400 Million was spent on improvements to the remaining reactors at Chernobyl, considerably enhancing their safety.

The total costs including cleanup, resettlement, and compensation to victims has been estimated to be roughly US$200 Billion.

In the 1986 to 1989 industrial and agricultural losses and insurance payments total about US$36 Billion spent during this period

The fire brigade of Pripyat was able to extinguish all the fire, except the graphite fire inside Reactor 4.

 (a) Fighting the Fire

Eventually, the graphite fire was extinguished by using sand, boron, dolomite, clay and lead from airdrops onto the burning reactor by helicopter.

The fire inside Reactor No. 4 continued to burn until 10 May 1986.

The nearby city of Pripyat was not immediately evacuated. - a government committee was formed to investigate the accident.

(b) Evacuation

The evacuation was begun a day after the explosion, as the committee faced with ample evidence of extremely high levels of radiation and a number of cases of radiation exposure.

(c) SarcophagusEven after the fire had been extinguished, radioactive particles were still escaping from the reactor core itself.

The Soviets devised a plan to cover the entire reactor with a shell that was to be able to exist forever. The shell was deemed the Sarcophagus.

Within it, there is about 200 tons of highly radioactive material which poses an environmental hazard until it is better contained.

Chernobyl before the accident

Chernobyl at the time of the accident

Chernobyl with the Sarcophagus around Reactor Number 4

Figure above: Before, During, and After figures of the Chernobyl buildings 3 & 4.

At first, the robots are sent for the task.- robots are malfunctioned because transistors are unable to work

properly in radioactive environments.

(d) Clean-up Efforts

Since this did not work, volunteers are sent for the task. -only allowed to be in the power station for 90 seconds or less

-exposure to the radiation in a long period would overwhelm their nervous system and subsequently killed them.

The decontamination process took place from May until the beginning of winter, 1986.

Any movable objects near the plant were buried.

About 60,000 buildings had to be washed with special chemicals, and even some roofs had to be

replaced.

Special chemicals were sprayed on streets to immobilize

radioactive particles.

Today, Pripyat and the surrounding area are not safe for human habitation.

The radioactivity in the damaged reactor would

need to be contained for 100,000 years to ensure safety.

However, the sarcophagus was designed to last for only about 30 years.

This would be a tough challenge not only for today, but for many future generations.

The Chernobyl disaster - is the worst nuclear power plant disaster

in history. - resulted in a severe release of

radioactivity following a massive power excursion which destroyed the reactor.

Achieving Optimum Nuclear Safety

To achieve optimum safety, nuclear plants should operate using a 'defence-in-depth' approach, with multiple safety systems supplementing the natural features of the reactor core.Key aspects of the approach are:

high-quality design & construction,

equipment which prevents operational disturbances or human failures and errors developing into problems,

comprehensive monitoring and regular testing to detect equipment or operator failures,

redundant and diverse systems to control damage to the fuel and prevent significant radioactive releases,

provision to confine the effects of severe fuel damage (or any other problem) to the plant itself.

Control Measure Ensure the design of the reactor or rods are safely design and

tested before initiated uses of the design.  Preparation for Emergency Responds Plans for immediate

evacuation.

Hiring workers that are trained educated and discipline to their work in controlling the nuclear reactor.

Making sure that the workers are observe by their supervisor or by safety officer that are assign to ensure no unwanted event occurs.

Frequent maintenances to any broken and unusable machine or unsafe built design of the reactor.

THE END

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