What was the Chernobyl disaster?

Answer 1

During the year of 1986 the Chernobyl nuclear power plant that the 4th reactor melted down and formed a radioactive cloud spreading deadly radiation throught the northern Ukrainian and some parts of Russia and it all happened in Chernobyl,Ukraine. The cloud sickened and killed over 3,000 citizens and deformed many more. There are many birth defects in that area today due to the high levels of radiation. The huge population of 50,000 in Pripyat was reduced to an abandoned city. There was a flawed reactor design had also caused a steam explosion and fires releasing about 5% of the radio reactor core into the atmosphere.

Answer 2

On April 26, 1986 the Chernobyl nuclear power plant, in what used to be the Ukranian SSR, the worst nuclear power plant in history occurred. It is still the only nuclear accident that is classified as a major accident, the highest level, by the International Nuclear and Radiological Event Scale.

The basic plan for the day was to do a test with reactor number 4 to try and fix a basic flaw in the plants design. If the plant was ever subject to a power outage, due to an emergency shut down, there would not be sufficient power to run coolant through the reactor for the 50 seconds it took to get the 3 diesel backup generators running. This would result in a meltdown.

To counter act this problem the engineers came up with a solution. The plan was to use the remaining power in the turbines to run the coolant while the backup generators started up. They did three previous tests with this end result in mind all ending in failure. The 26 of April was the fourth test and final test.

The basic plan for the test was to power down the rector to between 700 and 800 MW. Once turned down the steam turbines would be run up to full power. With those things done the steam supply to the turbines would be shut off. The performance of the turbine would be recorded to see if it would provide sufficient power in the case of a power failure. Once the voltage was gone the turbine would then be allowed to spin down to a stop. These plans were told to only the director of the plant and were never approved by the designer or the scientific manager of the plant. This is thought to be one of the major reasons why the experiment continued even when safety parameters were broken.

Powering down the reactor began in the day shift on the 25 April 1986 attaining 1600 MW before a different power plant went offline and the power down had to be postponed until after peak power usage hours. The day shift had left and the evening shift preparing to leave the call to once again start the test came in. The night shift was only supposed to have to deal with heat decay, but now they would be forced to deal with the test itself and were poorly prepared to do so.

Five minutes after midnight on the 26 of April the reactor finally reached the tests operational parameters of 700 MW. But the reactor had a natural buildup of the neutron absorbing isotope xenon-135. This isotope collected more of the loose neutrons in the reactor further powering down further from 700 MW to 500 MW. The operator of the reactor that night was a rookie with only three months experience and he accidentally put the control rods in too far. This absorbed even more neutrons lowering the power level from 500 MW to a measly 30 MW.

This made the test even more dangerous; so the managers decided to extract the control rods to almost there limit. Due to the almost shut down the buildup of xenon-135 was almost immediate and required the removal of more control rods.

All of these factors, as well as the fact that the core temperature and coolant flow was becoming unstable, were causing alarms to start going off in the control room. Of these many alarms the thermal-hydraulic ones were ignored to keep the reactor power level up, by 1 AM the reactor was finally stabilized at 200 MW and setting up for the test resumed.

During the 23 minutes between the stabilization of the reactor and the beginning of the test coolant flow exceeded safety limits causing the reactor to cool down and reduce power yet again. This made the reactor even more unstable in a position that was against the guidelines established by the designers.

The experiment after many delays finally began at 1:23:04 AM. Steam was shut off and the turbines began to run down. The diesel generators were started up and started to take the load off of the turbine, but not fast enough. The rate of flow for the coolant began to slow. The lack of coolant caused steam bubbles to form in the reactor. Unlike most reactors, where steam bubbles hinder the nuclear fission process, this reactor actually increased power level when steam bubbles are introduced. The steam bubbles also weakened the usefulness of water as a neutron absorber causing the reactor to power up even more. This constant powering up caused yet more steam to form. The automatic controls that were in control of the reactor counteracted this by reinserting the control rods.

Thirty-seven second later at 1:23:40 the button to emergency shut down the reactor was pushed. Why the button was pushed is still unknown, but the shutdown put all control rods into the reactor. The control rods began to lower at their slow speed taking upwards of 20 seconds to be put into the reactor. The tip of the control rods were designed poorly and actually caused a increase in power production as they entered the reactor. This caused a massive power strike to occur causing the first explosion.

This explosion caused the control rods to become stuck only inserted about one-third of the way into the reactor. The power generation continued to rise. Everything from here on is all theoretical because the instruments stopped recoding. Many of the parts in the reactor began to rupture as steam build up continued. A massive power spike jumping to at least 10 times its operational limit at 30GW. An explosion from the buildup of steam is what is thought to have happened next. This explosion is what melted the reactor casing and lifted the 2,000 ton upper plate off of it. with the reactor open the remaining coolant escaped as steam and the reactor continued its power clime.

A few seconds after the coolant escaping a second explosion resulting from the release of neutron particles occurred. (There are other less accepted theories about the cause of this explosion) The graphite that the much of the reactor was made of had also caught fire. This fire and the explosion greatly increased the spread of radiation contamination from the site. Burning graphite was ejected from the core landing on various roofs of the plant causing more fires due to the decision to ignore safety regulations and use flammable material for the roofs. One of the roofs that caught fire was the building housing the cooling unit for reactor three which was still running. The decision was made to keep the number three reactor running.

The fire department arrived on scene and started trying to put out the fires. Most of the fires were finally put out around 5:00 AM. The fire in reactor number 4 continued to burn for two weeks. Many substances were dropped on the reactor too put out the fire; the substances weight came to around 5000 metric tons.

Pripyat, the nearby town, was evacuated on April 27. The Soviet Union refused to admit there was a problem until radiation alarms went off in a nuclear power plant in Sweden. Still they refused to tell the whole truth, telling evacuees there's only been an accident at the nuclear plant.

Underneath the reactor there was two levels of bubbler pools that were used by the emergency coolant system. Above them a molten mess of concrete, graphite, fuel, and other materials had formed a lava like substance. If the lava like substance burned through the floor the water in these bubbler pools would cause yet another steam explosion. To stop this from happening three men swam through radioactive water to turn the valves to release the water from the pools. They were successful; two of the men later died of radiation poisoning.

The radioactive debris was collected by people wearing radiation suits. A concrete "sarcophagus" was erected around the reactor; then it was coved in sand, lead, and boric acid. 239 people from around Chernobyl were treated for acute radiation sickness; 31 of these people died within three months of treatment. Other effects of the disaster include the fact that to this day thousands of livestock and wild boar around Europe have been found to be contaminated with too much radioactivity it be safe for human consumption. Funds for erecting a better shelter than the current "sarcophagus" have been collected since 1997.

Answer 3

Chernobyl was a nuclear power plant in the former Soviet Union. On 26 April 1986, it suffered a massive failure which caused it to spread radioactive waste across large parts of Europe.

The accident began with a steam explosion that caused a fire, more explosions, and a subsequent nuclear meltdown. This caused clouds of radioactive debris to be released, and the damaged containment vessel started leaking radioactive matter which drifted over parts of the western Soviet Union, Eastern Europe, Scandinavia, UK, and even the eastern United States.

31 people died, 28 of them from acute radiation exposure at the time. It is estimated that another 125,000 could ultimately be affected directly. Between 100,000 and 200,000 people were evacuated from Chernobyl and surrounding areas. It was predicted that over the ensuing 70 years, there would be a 2% increase in cancer rates in the population.

The incident was believed to have been caused by power plant operators who violated plant procedures and were unaware of the safety requirements. It was 400 times more powerful than the Hiroshima bomb. Many of the surrounding areas had to be evacuated and won't be habitable until around 400-900 years from now because there are still very high levels of radiation in the ground and water.

Chernobyl was finally shut down completely in 2000.
On the 26th of April, 1986 there was a nuclear accident at the Chernobyl Nuclear Power Plant in Ukraine.

The exact time of the accident was recorded as 1:23:44am when a power surge caused a steam explosion which significantly damaged reactor number four. This initial damage caused a second explosion which had two potential causes:

1. The ignition of a mixture of hydrogen gas and air

2. A criticality incident or run away fission event

Current evidence suggests that the latter event occured which ultimately destroyed the roof of the reactor causing the release of radioactive material into the environment.

This is a very brief summary of the disaster and much more detail can be found in the related links.
On the 26th of April, 1986 there was a nuclear accident at the Chernobyl Nuclear Power Plant in Ukraine.

The exact time of the accident was recorded as 1:23:44am when a power surge caused a steam explosion which significantly damaged reactor number four. This initial damage caused a second explosion which had two potential causes:

1. The ignition of a mixture of hydrogen gas and air

2. A criticality incident or run away fission event

Current evidence suggests that the latter event occured which ultimately destroyed the roof of the reactor causing the release of radioactive material into the environment.

This is a very brief summary of the disaster and much more detail can be found in the related links.

Answer 4

Alright, you must read this entire article please to understand all of the terrible Chernobyl accident.

Nuclear energy is released by the splitting of the atom, called fission. One nucleus of uranium or plutonium is shot at an atom to split it up, to create more nuclei (plural of nucleus) to go on and split more atoms and so on and so forth. This all creates a great deal of heat. Since this whole process is happening in water, it heats up the water which creates steam to turn a turbine to create electricity. However, we must control the heat otherwise it will overreact and explode. We use control rods to do this. The control rods can be dipped in and out of the water to control the temperature. However, at Chernobyl the control rods melted. There was nothing the workers could do. The heat got out of control and boom, that's what you call a meltdown (this term is used in textbooks but is not an official term by the International Atomic Energy Agency). For specifics, it's reactor #4 that had the accident.

Answer 5

The nuclear power plant at Chernobyl in the USSR exploded. There was a massive explosion in a main reactor which caused widespread radiation which spread throughout most of the world due to it reaching the high altitude winds which travel almost everywhere.

Within a few months most if not all of the fire fighters, scientists and other involved in cleaning up the aftermath of the explosion were dead from radiation poisoning.

Please visit the link below for more information about the Chernobyl Noble Disaster.

Answer 6

On April 26th 1986 there was a disaster at the Chernobyl Nuclear Power Plant, however it was not in Russia but the Ukraine, a separate state/country.

Answer 7

in 1986 it caught fire and exploded.