Human-induced Hazard

Hazards can be manmade as well as natural. Probably the most famous manmade disaster is the Chernobyl Nuclear accident in 1986. Although the accident was before the birth of most IB students it is ongoing hazard so can be considered contemporary.

Chernobyl is located in the Ukraine, north west of the capital city Ukraine. The Ukraine is located in eastern Europe. However, at the time of the accident the Ukraine was part of the USSR (Union of Soviet Socialist Republics) and only became independent again in 1991 with the collapse of the USSR. The Ukraine has a population of about 46 million, although this figure is declining because of negative population growth (natural decrease). The Chernobyl nuclear accident took place at 01.23am local time on the 26th April 1986. The accident actually happened when scientists at the plant were testing the plants safety procedures. The Chernobyl nuclear accident is considered to be the worst nuclear accident in history. It is one of only two nuclear accidents to be classified level 7 on the International Nuclear Events Scale. The second accident is the much more recent one at the Fukushima Daiichi Nuclear plant in Japan caused by the 2011 earthquake and tsunami.

The Accident

As mentioned above the accident actually happened during an emergency practice. Prior to the explosion the power was cut to the power station to stimulate a power failure. Emergency generators did power up to continue the flow of cold water to keep the nuclear fuel cool. However, because of the time delay between power failure and the generators kicking and because of a power surge once the generators did kick in overheating occurred leading to a series of explosions. It was reactor 4 that experienced the series of explosions releasing radioactive fuel and radioactive material into the atmosphere and surrounding area.

The radiation levels in the worst hit areas of the reactor building were estimated to be 5.6 roentgens (a unit of measurement for exposure to radiation) per second, which is the equivalent to more than 20,000 roentgens and hour. A lethal dose of radiation is around 500 roentgens over 5 hours, so in some areas workers received lethal doses in minutes.

External fires around the plant were extinguished within 5 hours, but fires within the reactor continued until 10th May 1986. Helicopters were used to drop sand, clay and lead onto the reactor, but also firefighters on the ground were used. The firefighters were not warned about the dangers of radiation and most of them died later because of radiation poisoning.

Despite the massive radiation leak the nearby town of Pripyat was not evacuated for over 24 hours. The town had a population of around 50,000 at the time of the accident. When the evacuation warning eventually came, people were told that it would only be temporary and that they should leave all their belongings behind. However, a 30km exclusion zone still exists around the town, although some older residents have now chosen to move back.

As well as causing a massive radiation leak around the plant, a radioactive cloud was also released into the atmosphere. The USSR authorities did not notify the world straight away of the accident and it was actually another power station in Sweden that first detected the cloud. The cloud contained 400 times more radioactive material than the Hiroshima bomb that hit Japan. All of Europe received fallout from the cloud, although it is estimated that up to 50% fell on Russia, Belarus and the Ukraine.

As with any nuclear accident it is difficult to fully assess all the deaths and injuries accountable to the accident. However, it is estimated that 237 suffered acute radiation sickness and 52 died in the months following the accident. In total 135,000 people were evacuated from the area. The number of cancer cases blamed on the accident range from 2,000 to 100,000. The range is so big because it is hard to know how many would have caught cancer had there not been a leak. As well as the affects on humans, lakes, reservoirs and rivers received fallout as well as forests and animals. Many of the nearby animals died of cancers or became sterile.

To try and stop the leakage of radioactive material a giant container (called a sarcophagus) was built over the burnt out reactor. However, scientists now believe that the sarcophagus is leaking and another one needs to be built over the top of the old one.

It is estimated that it will be another 200 years until the land around Chernobyl is fully usable gain and up to 20,000 years until it is fully normal. As mentioned earlier an exclusion zone does exist, but up to 10,000 residents have returned. It is claimed that the evacuated are has turned into a bit of a wildlife sanctuary with animals adapting and now lynx, boar, wolves, bears, bisons and eagle owl being found in the area. However, others argue that this is not the case.

The Chernobyl Nightmare Revisited - BBC article

Wildlife defies Chernobyl radiation - BBC article

Chernobyl's wildlife sanctuary - BBC article

Chernobyl New Radiation Shield Funding Fall Short - BBC article


For a case study on the Australian wildfires (many started by humans) go to: Measuring Disasters.