NUCLEAR

ACCIDENT

Nuclear accidents and nuclear inci

dent

⦿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.

Nuclear accidents and nuclear inci

dent

⦿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.

International Nuclear

Event Scale

Level 0: Deviation

⦿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.

Level 1: Anomaly

⦿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.

Level 2: Incident

⦿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

Level 3: Serious incident

⦿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

Level 4: Accident with local

consequences

⦿Impact on people or the environment. Minor

release of radioactive material that may be

required, albeit unlikely, measures of oppositio

n. At least one death by radiation.

Radiological damage and control barriers. Molt

en fuel or damaged and release significant

amounts of radiation with probability of public

exposure.

Example: Accident Accident Tokaimura nuclea

r reactor RA-2, Argentina

Level 5: Accident with wider

consequences

⦿Impact on people or the environment. Limited release of

radioactive material

that mightrequire measures of opposition. Several deaths fr

om radiation.

Example: Windscale Fire, 1 3 Goiânia.2 Radiological

Accident

Radiological 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.

Level 6: Serious accident

⦿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

Level 7: Major accident

⦿Impact on people and

environmentMajor release

of radioactive material with

widespread health and

environmental effects

requiring implementation of

planned and extended -

countermeasures

Level 7: Major accident

⦿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.

Level 7: Major accident

⦿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

Out of scale

⦿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 effects of

an accidental exposure

⦿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 a

nd 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 (dizzine

ss, disorientation) and cancer

s of many types

Excess of 10 000 mSv safe Death

END