Nuclear Disasters

A Historical Look

The International Nuclear and Radiological Event Scale

Major AccidentLevel 7

• Major release of radioactive material with widespread health and environmental effects requiring implementation of planned andextended countermeasures.

Serious AccidentLevel 6

• Significant release of radioactivematerial likely to require implementation of planned countermeasures.

Accident withWider Consequences

Level 5

• Limited release of radioactive materiallikely to require implementation of some planned countermeasures.• Several deaths from radiation.

Accident withLocal Consequences

Level 4

• Minor release of radioactive materialunlikely to result in implementation ofplanned countermeasures other thanlocal food controls.• At least one death from radiation

Serious IncidentLevel 3

• Exposure in excess of ten times thestatutory annual limit for workers.• Non-lethal deterministic health effect(e.g., burns) from radiation.

IncidentLevel 2

• Exposure of a member of the publicin excess of 10 mSv.• Exposure of a worker in excess of thestatutory annual limits

AnomalyLevel 1 No threat to the environment

Effects of Radiation Exposure

• Although a dose of just 25 rems causes some detectable changes in blood, doses to near 100 rems usually have no immediate harmful effects.

• Doses of 300 rems or more cause temporary hair loss, fever, diarherea, damage to nerve cells and the cells that line the digestive tract. Severe loss of white blood cells, reduces production of blood platelets.

• Half of all people exposed to 450 rems die, and doses of 800 rems or more are always fatal.

Tokaimura, Japan Sept. 30, 1999 INES Rating: 4

Tokaimura, Japan Sept. 30, 1999 INES Rating: 4

• A batch of highly-enriched uranium was prepared for a nuclear reactor that had not been used in more than three years. The operators had not been trained in how to handle uranium that was so highly enriched.

• They put far more uranium into the solution in a precipitation tank than is allowed. The tank was not designed for this type of uranium.

Tokaimura, Japan Sept. 30, 1999 INES Rating: 4

• Only when the tank was drained of the solution could the critical reaction be stopped, but by then, it was too late for two of the three operators working with the uranium, as they died of radiation.

• Less than a hundred workers and people who lived nearby were hospitalized for exposure to radiation, and 161 people who lived within 1,000 feet of the plant were evacuated, according to the World Nuclear Association.

Three Mile Island, Harrisburg, PA March 28, 1979 - INES Rating: 5

Three Mile Island, Harrisburg, PA March 28, 1979 - INES Rating: 5

• It all began with a simple plumbing break down. A small valve opened to relieve pressure in the reactor malfunctioned and failed to close. This caused cooling water to drain, and the core began to overheat.

• The machines monitoring conditions inside the nuclear core provided false information, so plant operators shut down the very emergency water that would have cooled the nuclear core and solved the problem.

Three Mile Island, Harrisburg, PA March 28, 1979 - INES Rating: 5

• The core began to overheat, and reached 4,300 degrees Fahrenheit. The water nearly reached the fuel rods, which would have caused a full meltdown of the core.

• Plant operators several hours later to instruct them to turn the water back on, and conditions stabilized.

• The NRC determined that no one had died of causes related to the incident.

Kyshtym, Soviet Union Sept. 29, 1957 INES Rating: 6

Kyshtym, Soviet Union Sept. 29, 1957 INES Rating: 6

• Soviet scientists were frantically trying to catch up to the Americans after World War II when they began construction of the Mayak nuclear facility.

• Soviet nuclear knowledge had many holes, so it was impossible to know whether some decisions made in the construction were safe. As it turned out, many of those decisions seriously compromised the plant's facility.

Kyshtym, Soviet Union Sept. 29, 1957 INES Rating: 6

• Initially, the plant's operators simply dumped the nuclear waste into a nearby river, before a storage facility for that waste opened in 1953. The storage facility began to overheat, and a cooler was soon added, but it was poorly constructed.

• In September 1957, the cooling system in a tank containing about 70 tons of radioactive waste failed, and the temperature started to rise. This caused a non-nuclear explosion of dried waste.

Kyshtym, Soviet Union Sept. 29, 1957 INES Rating: 6

• There had been a significant release of radioactive material into the environment. The radioactive cloud spread out for hundreds of miles to the northeast.

• The Soviet government was forced to evacuate 10,000 people in the affected area after reports surfaced of people's skin literally falling off. The radiation is estimated to have directly caused the deaths of 200 people due to cancer.

Chernobyl, Soviet Union (now Ukraine)April 26, 1986 INES Rating: 7

Chernobyl, Soviet Union (now Ukraine)April 26, 1986 INES Rating: 7

• During a routine test, the plant's safety systems were turned off to prevent any interruptions of power to the reactor. The reactor was supposed to be powered down to 25 percent of capacity.

• The reactor's power fell to less than one percent, and so the power had to be slowly increased to 25 percent. Just a few seconds after facility operators began the test, however, the power surged unexpectedly and the reactor's emergency shutdown failed. What followed was a full-blown nuclear meltdown.

Chernobyl, Soviet Union (now Ukraine)April 26, 1986 INES Rating: 7

• The reactor's fuel elements ruptured and there was a violent explosion. The fuel rods melted after reaching a temperature over 3,600 degrees Fahrenheit. The graphite covering the reactor then ignited and burned for over a week, spewing huge amounts of radiation into the environment.

• About 200,000 people had to be permanently relocated after the disaster

Chernobyl, Soviet Union (now Ukraine)April 26, 1986 INES Rating: 7

• The Chernobyl release polluted the countryside much more than 10 Hiroshimas would have done.

• Many people died from the explosion and even more from the effects of the radiation later. The World Health Organization reported the actual number of deaths related to Chernobyl was about 9,000.

• Still today, people are dying from the radiation caused by the Chernobyl accident. The estimated total number of deaths will be 16,000.

The nuclear cloud enveloped all of Europe. Belarus received about 60% of the contamination.

Effects of Chernobyl