Nuclear accidents

Laura Rodriguez3°BBEnglish – Daniela Segui2011ITSP

A nuclear accident or nuclear incident, depending on the severity, is known toinadvertent releases of radioactive materials, accidental or radioactivity levels likely to harm public health.

Is described as a nuclear accident or incident according to its severity and its impacton the population and the environment.

Radiological accidents can happen at a nuclear plant or outside, ie in a facility thatconducts a nuclear activity (hospitals, research laboratories ...) or due to the loss of a radioactive source, or by spreading involuntary or voluntary radioactive substances intothe environment.

To measure the severity of an event, there is an international scale: INES scale.

No safety significance. Examples: 4 June 2008: Krško, Slovenia: Leakage from the

primary cooling circuit. 17 December 2006, Atucha, Argentina: Reactor

shutdown due to tritium increase in reactor compartment. 13 February 2006: Fire in Nuclear Waste Volume

Reduction Facilities of the Japanese Atomic Energy Agency (JAEA) in Tokaimura.

Impact on the defense in depth. Greater exposure to legal limits annual member of the public, minor problems with security elements and components to defense in depthremaining and theft or loss of a source of low-level radioactivity.

Impact on people and the environment. Exposure of a member of the public to more than 10 mSv and exposure of a worker in excess of legal limits annually.Radiological damage and control barriers. Radiation level in an operational area of more than 50 mSv / h and radioactive contamination within the facility is not prepared in thedesign.Impact on the defense in depth.Example: Incident at nuclear plant Asco

Impact on people and the environment. Exhibition of 10 or more times the legal annuallimit for workers and non-lethal effects produced by radiation.Radiological damage and control barriers. Exhibition of more than 1 Sv / h in a work zone.Impact on the defense in depthExample: THORP plant Sellafield (United Kingdom) – 2005.

Paks Nuclear Power Plant (Hungary), 2003; fuel rod damage in cleaning tank.

Vandellos Nuclear Power Plant (Spain), 1989; fire destroyed many control systems; the reactor was shut down

Impact on people or the environment. Minor release of radioactive material that may be required, albeit unlikely, measures of opposition. At least one death by radiation.Radiological damage and control barriers. Molten fuel or damaged and release significant amounts of radiation with probability of public exposure.Example: Accident Accident Tokaimura nuclear reactor RA-2, Argentina

Impact on people or the environment. Limited release of radioactive material that mightrequire measures of opposition. Several deaths from radiation.Example: Windscale Fire, 1 3 Goiânia.2 Radiological AccidentRadiological damage and control barriers.There is serious damage to the reactor core and causes the release of radioactivematerial in a facility that generates risk of public exposure that could result from acritical accident or fire.Example: Accident at Three Mile Island.

Impact on people and environment Significant release of radioactive material likely to

require implementation of planned countermeasures.

There has been only one such event to date: Kyshtym disaster at Mayak, Soviet Union, 29

September 1957. A failed cooling system at a military nuclear waste reprocessing facility caused a steam explosion that released 70–80 tons of highly radioactive material into the environment. Impact on local population is not fully known. This is the only accident to go over 5 on the scale besides Chernobyl and Fukushima

Impact on people and environmentMajor release of radio active material with widespread health and environmental effects requiring implementation of planned and extended countermeasures

There have been two such events to date:Chernobyl disaster, 26 April 1986. A power surge during a test procedure resulted in a criticality accident, leading to a powerful steam explosion and fire that released a significant fraction of core material into the environment, resulting in a death toll of 56 as well as estimated 4,000 additional cancer fatalities among people exposed to elevated doses of radiation. As a result, the city of Chernobyl (pop. 14,000) was largely abandoned, the larger city of Pripyat (pop. 49,400) was completely abandoned, and a 30 km exclusion zone was established.

Fukushima I nuclear accidents, a series of events beginning on 11 March 2011. Rated level 7 on 11 April 2011 by the Japanese government's nuclear safety agency.[2][3] Major damage to the backup power and containment systems caused by the 2011 Tōhoku earthquake and tsunami resulted in overheating and leaking from some of the Fukushima I nuclear plant's reactors. Each reactor accident was rated separately; out of the six reactors, three were rated level 5, one was rated at a level 3, and the situation as a whole was rated level 7.[4] An exclusion zone of 20 km was established around the plant as well as a 30 km voluntary evacuation zone

There are also events of no safety relevance, characterized as "out of scale".

Examples:17 November 2002, Natural Uranium Oxide Fuel Plant at the Nuclear Fuel Complex in Hyderabad, India: A chemical explosion at a fuel fabrication facility.

29 September 1999: H.B. Robinson, United States: A tornado sighting within the protected area of the nuclear power plant (NPP).

5 March 1999: San Onofre, United States: Discovery of suspicious item, originally thought to be a bomb, in nuclear power plant.

The severity of effects increases with the dose, duration and age of the person. In case of accident, the doctor determined from the dose received medical examinations.

Exhibition Severity Symptoms

Some millisieverts  only possible long-term

Several hundred millisieverts

No immediate effect Possible temporary nausea and slight fever

Between 1 000 and 2 000 millisieverts

remarkable medical Effect

 vomiting, fatigue,fever, risk of infection,

cancer

Between 2 000 and 4 000 millisieverts

serious medical Effect 

vomiting, fever, digestive disorders, bleeding, hair loss,

leukemia, other cancers

Between 4 000 and 10 000 millisievertsand

 probability greater than 50% death,

property damage neurological (dizziness, disorientation) a

nd cancers of many types

Excess of 10 000 mSv  safe Death