The Worst Nuclear Disaster of the 20th Century

What was Chernobyl?

Chernobyl was a nuclear power plant in the Ukraine just south of the town of Pripyat. the complex consisted of four nuclear reactors of RBMK-1000 design, with two more under construction at the time of the accident. The first four were operational at the time of the disaster. The reactors used 2% U-235 uranium dioxide fuel.

What Happened?

In 1986, the Soviets were conducting a test on reactor 4 of the complex. The test was to determine how long the reactor turbines would spin when the main electricity to the reactor was turned off. Prior to the test, operators had turned off the automatic shutdown systems of the reactor, leaving it in very unstable condition for the test. The introduction of the very hot fuel combined with the cooling water caused the fuel to fragment. This caused pressure to rise dramatically. It even caused the 1000 ton reactor cap to rupture, jamming all the control rods. Emergency water caused intense steam generation, eventually leading to an explosion and the release of fission materials. Seconds later, another explosion released incandescent graphite and fuel channel fragments.     

Controlling The Damage

The following half a day was spent pumping 200-300 tonnes of water per hour into the intact half of the reactor core. This was abandoned due to the fear of flooding into zones 1 and 2. The next few weeks were spent helicoptering 5000 tonnes of boron, dolomite, sand, clay and lead to quell the fire. Chernobyl was the worst civilian controlled nuclear disaster in history. The disaster released all of the xenon gas, about half of the iodine and cesium, and at least 5% of the remaining radioactive material in the Chernobyl 4 reactor core (which had 192 tonnes of fuel) into the atmosphere and downwind areas for 10 days. The town of Pripyat was evacuated and to this day remains a ghost town.

The Facts and Figures

One of the strangest parts of the disaster was the casualty figure. Only 56 people died from the meltdown directly. The future is where this disaster earns its credit. the ranges of people expected to die from the radiation range from 4,000 to 500,000. Nothing is certain in this case.The difficulty is proving who actually dies from radiation. this explains the massive range in the death toll predictions. Chernobyl also increased cancer and deformity rates in the affected regions drastically. The cost of total loss is $15 billion so far.   

What was learned?

The Chernobyl Disaster called for the immediate revision of Eastern European nuclear reactor design. Several improvements were made to all existing RBMK reactors still in operation. In fact, several joint ventures made by both the United States and post- Soviet Russia helped improve all nuclear reactors. Main changes were made in the cooling processes in older reactors.




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