Location of Chernobyl Nuclear Power Plant Accident
On April 26, 1986, at 1:23 a.m. local time, reactor number four at the Chernobyl Nuclear Power Plant in the
The plume drifted over extensive parts of:
Large areas of
It was the worst nuclear power plant disaster ever, resulting in a severe release of radioactivity into the environment. Two people died in the initial steam explosion, but most deaths from the accident were attributed to radiation.
The cost of the disaster is estimated to be around $200 billion USD, making
According to the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO), 56 direct deaths and an estimated 4,000 extra cancer deaths have been attributed to the disaster.
The Chernobyl Exclusion Zone and other limited areas remain off limits. The majority of affected areas are now considered safe for economic activity and settlement.
The Accident
The accident occurred on April 26, 1986, when reactor four suffered a massive, catastrophic power excursion. This resulted in a steam explosion, tearing the top from the reactor, exposing the core, and dispersing large amounts of radioactive particulate and gaseous debris (mostly Strontium-90 and Cesium-137). This allowed oxygen to contact the hot core, which contained 1,700 tons of combustible graphite moderator. The burning graphite moderator increased the emission of the radioactive particles.
The radioactivity was not contained by any type of containment vessel, and radioactive particles were carried by the wind across international borders.
Crisis Management
Radiation Levels
The radiation levels in the worst-hit areas of the reactor building are estimated to have been 5.6 rontgen per second (R/s), or 20,000 R/hr. A lethal dose is around 500 rontgen over 5 hours; some workers received fatal doses within several minutes.
Due to faulty dosimeters (equipment to measure rontgens) or dosimeters which only read low levels of rontogens, the reactor crew chief assumed that the reactor was intact. Operating under this assumption, the chief and his crew stayed in the reactor building until morning trying to pump water into the reactor.
None wore protective gear, and most died from radiation exposure within three weeks.
Fire Containment
Shortly after the accident, firefighters arrived to try to extinguish the fire. They were not told how dangerous the smoke and debris were. They were not told that the fire involved the reactor.
The fires were extinguished by 5 a.m., but many firefighters received high doses of radiation. The fire inside reactor no. 4 continued to burn until May 10, 1986. It was finally extinguished by dropping tons of sand, lead, and clay onto the burning reactor and injecting liquid nitrogen.
Causes of the Disaster
There were two official explanations of the accident:
- Flawed operators explanation
Placed the blame on the power plant operators - Flawed design explanation
Placed the blame on flaws in the reactor design, especially the control rods
Effects of the Disaster
- International spread of radioactivity
- Radioactive release
- Human cost
237 people suffered from acute radiation sickness
31 died within the first 3 months after the disaster
135,000 evacuated from the area - Environmental costs
Radioactive contamination of aquatic systems
Four square kilometers of pine forest in the immediate vicinity of the reactor turned brown and died
Some animals in the worst-hit areas died or stopped reproducing
All work on the unfinished reactors at
Disaster's Effect on Human Health
· 57 direct deaths in the accident itself
· 4,000 additional cancer cases due to the accident
· Primarily thyroid cancer
· No increase in the rate of birth defects or abnormalities
· No increase in solid cancers
· Possibility of tens of thousands of cases of thyroid cancer in the future.
source: abovetopsecret
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