Showing posts with label nuclear crisis. Show all posts
Showing posts with label nuclear crisis. Show all posts

Biggest nuclear accidents
Today marks the 25th anniversary of the nuclear accident at Chernobyl. In light of that, and the story continuing to unfold at Japan's Fukishima plant, we'll look at three of the worst nuclear plant disasters. First, to give some context, here's how the International Nuclear and Radiological Event Scale (INES) classifies each type of event:


Level 7 disaster
Major release of radioactive material; widespread health and environmental effects

Level 6 accident
Significant release; requires planned countermeasures

Level 5 accident
Limited release; several deaths from radiation

Level 4 accident
Minor release

Level 3 incident
Exposure in excess of 10 times the annual limit for workers; possible burns from exposure

Level 2 incident
Exposure of statutory annual limits

Level 1: Anomaly
Definition

Chernobyl
Date: April 26, 1986

Level: 7 on INES

Comparison: TheChernobyl plant accident  released significantly more radiation into the atmosphere than the Hiroshima bombing during World War II. How does that compare with the Fukishima event?

What happened:

* Plant operators carrying out technical experiment switched off key safety systems
* Explosion blew off the reactor's 2,000-ton steel and concrete lid
* No secondary containment vessel
* Casualties
* Videos of the disaster

Aftermath:

* Reactor later entombed since has developed cracks and is being replaced by new structure
* An 18-mile (30-km) exclusion zone remains in force
* You can visit the Chernobyl Museum in Kiev; tours are also offered inside the exclusion zone


Note: At the time of the accident, Chernobyl was located in the Soviet Union

Three Mile Island
Date: March 28, 1979

Level: 5 on INES

Comparison: Three Mile Island  is said to have released a very low level of radiation. Some figures say the average exposure was equivalent to a common medical procedure.

What happened:

* Pump failed to circulate cooling water
* Efforts to ease pressure on reactor backfired when an open valve caused more coolant to pour out
* Rising temperatures caused hydrogen explosion in reactor building; 45 percent of the nuclear fuel rods melted
* After more than two hours, backup valve was shut, stopping leak; later reactor pump turned back on, temperature lowered
* Casualties – none
* Watch videos about the event


Aftermath:

* One of the plant's reactors was permanently shut down; the other is licensed to operate well into the future

Fukushima


Date: March 11, 2011

Level: Initially 4 on INES, upgraded to level 7 on April 12

Comparison: According to Japanese officials, the radiation levels near the plant ) rose to roughly twice those that constitute an emergency situation.

What happened:

* 9.0-magnitude earthquake and following tsunami caused three of the six reactors at Fukushima plant to shut down
* Tsunami destroyed backup diesel generators, cut off pumps that circulate coolant around reactor cores
* Reactors overheated, causing partial meltdowns; explosions have damaged outer buildings
* Casualties

Aftermath:

* The latest on the disaster
* The evacuation zone has been recently extended

 source

Chernobyl disaster 25 years
April 26, 1986 an explosion occurred on the fourth unit of Chernobyl nuclear power plant, located on the territory of the Ukrainian SSR. The reactor was completely destroyed, and the environment were released large quantities of radioactive substances. The accident is regarded as the largest of its kind in the history of nuclear power, as alleged by the number of dead and injured from the consequences of people and the economic damage. At the time of the accident in Chernobyl nuclear power plant was the most powerful in the Soviet Union. 31 people died during the first three months after the accident, late effects of irradiation, revealed over the next 15 years, have killed 60 to 80 people. 134 people suffered radiation sickness to varying degrees of gravity, more than 115 thousand people from the 30-km zone were evacuated.
an explosion and fire at the Chernobyl power plant in the Ukraine became the world's worst nuclear accident.

Huge quantities of radioactive contamination were released into the atmosphere, which drifted over much of western Russia and Europe. While 31 deaths are directly attributed to the accident, the World Health Organisation believed the accident can be linked to 4,000 fatalities, while Greenpeace puts the figure at over 200,000.

Following the accident, the city of Pripyat close to the Chernobyl plant had to be evacuated of its entire population in a matter of hours. The images in this gallery show Pripyat and the surrounding area today, 25 years on from the disaster.

The sarcophagus covering the damaged fourth reactor at the Chernobyl nuclear power plant is seen in this photograph behind a building decorated with a graffiti in Prypiat. The city was only evacuated of residents on 27 April 1986, a full 24 hours after the accident.

A child's gas mask and a shoe are seen at a kindergarten in the abandoned city of Prypiat. Residents were told they would only be away from the city for three days. 25 years on, humans are still forbidden to enter Prypiat.

The shattered remains of the control room for reactor number four at the Chernobyl nuclear power plant in Ukraine. The explosion was caused by a sudden power output surge, made worse by an emergency shutdown that prompted a reactor vessel to rupture. This exposed to the graphite moderator of the reactor to air, causing it to ignite. The resulting fire sent a plume of highly radioactive smoke fallout into the atmosphere.
The interior of a kindergarten in Prypiat. Thinking they would only be away for a short time, most of the residents of the city left their personal belongings behind, which are still there today.
Ekaterina Kozel pushes a trolley with food to her house in the almost abandoned village of Tulgovichi, near the 19-mile exclusion zone around the Chernobyl nuclear reactor. The zone was established soon after the disaster, and is controlled by the Administration of the Alienation Zone within Ukraine's Ministry of Emergencies and Affairs of Population Protection from Consequences of Chernobyl Catastrophe.
Toys are seen scattered on the floor inside a kindergarten in Prypiat.
An empty swimming pool in Prypiat.
An aerial view of the abandoned village of Krasnoselie, in the state radiation ecology reserve in the 19-mile exclusion zone around the Chernobyl nuclear reactor, some 243 miles south-east from Minsk, Belarus. The territory of the zone is polluted unevenly. There are some areas of hyperintensive pollution, caused by wind and rain spreading radioactive dust at the time of the accident, and subsequently by numerous burial sites for various material and equipment used in decontamination.

Engineer Sergei Horloogijn measures a radiation dosage rate, as workers clear the forest near the village of Babchin, near the exclusion zone around the Chernobyl nuclear reactor. Approximately 3,000 workers are employed within the zone. They do not live inside the zone, but work shifts.
A Belarussian guard opens a gate at checkpoint 'Maidan' of the state radiation ecology reserve in the exclusion zone around the Chernobyl nuclear reactor. Access to the zone for brief visits is possible. Guided tours are available to the public from Kiev or by applying directly to ChernobylInterInform, a department of zone administration.
A combination of images, taken in 1982 and on 31 March 2011, show views of the city of Prypiat before and after the accident at the Chernobyl nuclear power plant.
Ekaterina Kozel cries in her house in the near-abandoned village of Tulgovichi. A few residents, including Kozel, continue to refuse to leave the area surrounding the exclusion zone, insisting they have lived in the region all their life and have no desire to move away. They receive little or no support from the local authorities.

Another combination of images, taken in 1982 and on 24 February 2011, showing the city of Prypiat.
A weather-worn monument commemorating second world war Soviet soldiers stands in the abandoned city of Pripyat.
Daubings on a wall in Pripyat. Although the city was evacuated of its residents on 27 April, the general population of the Soviet Union was not informed of the disaster until 29 April.
Children's toys and gas masks, covered by radioactive dust, lie on bed frameworks in an abandoned kindergarten in the ghost town of Pripyat.
A combination of images, taken in 1982 and on 31 March 2011 (bottom), showing a street in the abandoned city of Prypiat. Pripyat was founded in 1970 to house workers for the Chernobyl plant, and was officially proclaimed a city in 1979. Its population before the accident was around 50,000. Its population today is zero.