Nuclear Accidents
Nuclear Accidents And lessons learned
Momina M.
DisclaimerNuclear power plants are prominent and provide
approximately 5.7% of the worlds energy and 13% of the worlds
electricity.There are about 437 nuclear power plants worldwide2
See more at:
http://www.processindustryforum.com/hottopics/nucleardisasters#sthash.8xvYbpMH.dpuf
2
Levels of International Nuclear Events4
Level 7: Major accident[edit]Impact on people and
environmentMajor release of radioactive material with widespread
health and environmental effects requiring implementation of
planned and extended countermeasuresThere 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 (official WHO estimate) 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 permanent 30 kilometres
(19mi) exclusion zone around the reactor was established.Fukushima
Daiichi nuclear disaster, a series of events beginning on 11 March
2011. A month later the Japanese government's nuclear safety agency
rated it level 7.[2][3] Major damage to the backup power and
containment systems caused by the 2011 Thoku 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] A temporary exclusion zone of 20 kilometres (12mi) was
established around the plant as well as a 30 kilometres (19mi)
voluntary evacuation zone;[5] In addition, the evacuation of Tokyo
Japan's capital and the world's most populous metropolitan area,
225 kilometres (140mi) away was at one point considered.[6] See
also 2011 Japanese nuclear accidents.See also: Comparison of
Fukushima and Chernobyl nuclear accidentsLevel 6: Serious
accident[edit]Impact on people and environmentSignificant release
of radioactive material likely to require implementation of planned
countermeasures.There has been only one such event to date:Kyshtym
disaster at Mayak Chemical Combine (MCC) Soviet Union, 29 September
1957. A failed cooling system at a military nuclear waste
reprocessing facility caused a steam explosion with a force
equivalent to 70-100 tons of TNT. About 70 to 80 metric tons of
highly radioactive material were carried into the surrounding
environment. The impact on local population is not fully known, but
at least 22 villages were affected with deadly doses.[7]Level 5:
Accident with wider consequences[edit]Impact on people and
environmentLimited release of radioactive material likely to
require implementation of some planned countermeasures.Several
deaths from radiation.Impact on radiological barriers and
controlSevere damage to reactor core.Release of large quantities of
radioactive material within an installation with a high probability
of significant public exposure. This could arise from a major
criticality accident or fire.Examples:[7]Windscale fire (United
Kingdom), 10 October 1957.[8] Annealing of graphite moderator at a
military air-cooled reactor caused the graphite and the metallic
uranium fuel to catch fire, releasing radioactive pile material as
dust into the environment.Three Mile Island accident near
Harrisburg, Pennsylvania (United States), 28 March 1979.[9] A
combination of design and operator errors caused a gradual loss of
coolant, leading to a partial meltdown. An unknown amount of
radioactive gases were released into the atmosphere, so injuries
and sicknesses that have been attributed to this accident can be
deduced from epidemiological studies but can never be proven.First
Chalk River accident,[10][11] Chalk River, Ontario (Canada), 12
December 1952. Reactor core damaged.Lucens partial core meltdown
(Switzerland), 21 January 1969. A test reactor built in an
underground cavern suffered a loss-of-coolant accident during a
startup, leading to a partial core meltdown and massive radioactive
contamination of the cavern, which was then sealed.[12]Goinia
accident (Brazil), 13 September 1987. An unsecured caesium chloride
radiation source left in an abandoned hospital was recovered by
scavenger thieves unaware of its nature and sold at a scrapyard.
249 people were contaminated and 4 died.Level 4: Accident with
local consequences[edit]Impact on people and environmentMinor
release of radioactive material unlikely to result in
implementation of planned countermeasures other than local food
controls.At least one death from radiation.Impact on radiological
barriers and controlFuel melt or damage to fuel resulting in more
than 0.1% release of core inventory.Release of significant
quantities of radioactive material within an installation with a
high probability of significant public
exposure.Examples:[7]Sellafield (United Kingdom) five incidents
from 1955 to 1979.[13]SL-1 Experimental Power Station (United
States) 1961, reactor reached prompt criticality, killing three
operators.Saint-Laurent Nuclear Power Plant (France) 1969, partial
core meltdown; 1980, graphite overheating.Buenos Aires (Argentina)
1983, criticality accident on research reactor RA-2 during fuel rod
rearrangement killed one operator and injured two others.Jaslovsk
Bohunice (Czechoslovakia) 1977, contamination of reactor
building.Tokaimura nuclear accident (Japan) 1999, three
inexperienced operators at a reprocessing facility caused a
criticality accident; two of them died.Level 3: Serious
incident[edit]Impact on people and environmentExposure in excess of
ten times the statutory annual limit for workers.Non-lethal
deterministic health effect (e.g., burns) from radiation.Impact on
radiological barriers and controlExposure rates of more than 1 Sv/h
in an operating area.Severe contamination in an area not expected
by design, with a low probability of significant public
exposure.Impact on defence-in-depthNear-accident at a nuclear power
plant with no safety provisions remaining.Lost or stolen highly
radioactive sealed source.Misdelivered highly radioactive sealed
source without adequate procedures in place to handle
it.Examples: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.Davis-Besse Nuclear
Power Station (United States), 2002; negligent inspections resulted
in corrosion through 6 inches (15.24 cm) of the carbon steel
reactor head leaving only 38 inch (9.5 mm) of stainless steel
cladding holding back the high-pressure (~2500 psi, 17 MPa) reactor
coolant.Level 2: Incident[edit]Impact on people and
environment.Exposure of a member of the public in excess of 10
mSv.Exposure of a worker in excess of the statutory annual
limits.Impact on radiological barriers and controlRadiation levels
in an operating area of more than 50 mSv/h.Significant
contamination within the facility into an area not expected by
design.Impact on defence-in-depthSignificant failures in safety
provisions but with no actual consequences.Found highly radioactive
sealed orphan source, device or transport package with safety
provisions intact.Inadequate packaging of a highly radioactive
sealed source.Examples:Blayais Nuclear Power Plant flood (France)
December 1999Asc Nuclear Power Plant (Spain) April 2008;
radioactive contamination.Forsmark Nuclear Power Plant (Sweden)
July 2006; backup generator failure; two were online but fault
could have caused all four to fail.Gundremmingen Nuclear Power
Plant (Germany) 1977; weather caused short-circuit of high-tension
power lines and rapid shutdown of reactorShika Nuclear Power Plant
(Japan) 1999; criticality incident caused by dropped control rods,
covered up until 2007.[14]Level 1: Anomaly[edit]Impact on
defence-in-depthOverexposure of a member of the public in excess of
statutory annual limits.Minor problems with safety components with
significant defence-in-depth remaining.Low activity lost or stolen
radioactive source, device or transport package.(Arrangements for
reporting minor events to the public differ from country to
country. It is difficult to ensure precise consistency in rating
events between INES Level-1 and Below scale/Level-0)Examples:Penly
(Seine-Maritime, France) 5 April 2012; an abnormal leak on the
primary circuit of the reactor n2 was found in the evening of 5
April 2012 after a fire in reactor n2 around noon was
extinguished.[15]Gravelines (Nord, France), 8 August 2009; during
the annual fuel bundle exchange in reactor #1, a fuel bundle
snagged on to the internal structure. Operations were stopped, the
reactor building was evacuated and isolated in accordance with
operating procedures.[16]TNPC (Drme, France), July 2008; leak of
18,000 litres (4,000impgal; 4,800USgal) of water containing 75
kilograms (165lb) of unenriched uranium into the
environment.[17]Level 0: Deviation[edit]No safety
significance.4
Levels of International Nuclear EventsLevel 0
No threat to safety5
Level 7: Major accident[edit]Impact on people and
environmentMajor release of radioactive material with widespread
health and environmental effects requiring implementation of
planned and extended countermeasuresThere 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 (official WHO estimate) 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 permanent 30 kilometres
(19mi) exclusion zone around the reactor was established.Fukushima
Daiichi nuclear disaster, a series of events beginning on 11 March
2011. A month later the Japanese government's nuclear safety agency
rated it level 7.[2][3] Major damage to the backup power and
containment systems caused by the 2011 Thoku 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] A temporary exclusion zone of 20 kilometres (12mi) was
established around the plant as well as a 30 kilometres (19mi)
voluntary evacuation zone;[5] In addition, the evacuation of Tokyo
Japan's capital and the world's most populous metropolitan area,
225 kilometres (140mi) away was at one point considered.[6] See
also 2011 Japanese nuclear accidents.See also: Comparison of
Fukushima and Chernobyl nuclear accidentsLevel 6: Serious
accident[edit]Impact on people and environmentSignificant release
of radioactive material likely to require implementation of planned
countermeasures.There has been only one such event to date:Kyshtym
disaster at Mayak Chemical Combine (MCC) Soviet Union, 29 September
1957. A failed cooling system at a military nuclear waste
reprocessing facility caused a steam explosion with a force
equivalent to 70-100 tons of TNT. About 70 to 80 metric tons of
highly radioactive material were carried into the surrounding
environment. The impact on local population is not fully known, but
at least 22 villages were affected with deadly doses.[7]Level 5:
Accident with wider consequences[edit]Impact on people and
environmentLimited release of radioactive material likely to
require implementation of some planned countermeasures.Several
deaths from radiation.Impact on radiological barriers and
controlSevere damage to reactor core.Release of large quantities of
radioactive material within an installation with a high probability
of significant public exposure. This could arise from a major
criticality accident or fire.Examples:[7]Windscale fire (United
Kingdom), 10 October 1957.[8] Annealing of graphite moderator at a
military air-cooled reactor caused the graphite and the metallic
uranium fuel to catch fire, releasing radioactive pile material as
dust into the environment.Three Mile Island accident near
Harrisburg, Pennsylvania (United States), 28 March 1979.[9] A
combination of design and operator errors caused a gradual loss of
coolant, leading to a partial meltdown. An unknown amount of
radioactive gases were released into the atmosphere, so injuries
and sicknesses that have been attributed to this accident can be
deduced from epidemiological studies but can never be proven.First
Chalk River accident,[10][11] Chalk River, Ontario (Canada), 12
December 1952. Reactor core damaged.Lucens partial core meltdown
(Switzerland), 21 January 1969. A test reactor built in an
underground cavern suffered a loss-of-coolant accident during a
startup, leading to a partial core meltdown and massive radioactive
contamination of the cavern, which was then sealed.[12]Goinia
accident (Brazil), 13 September 1987. An unsecured caesium chloride
radiation source left in an abandoned hospital was recovered by
scavenger thieves unaware of its nature and sold at a scrapyard.
249 people were contaminated and 4 died.Level 4: Accident with
local consequences[edit]Impact on people and environmentMinor
release of radioactive material unlikely to result in
implementation of planned countermeasures other than local food
controls.At least one death from radiation.Impact on radiological
barriers and controlFuel melt or damage to fuel resulting in more
than 0.1% release of core inventory.Release of significant
quantities of radioactive material within an installation with a
high probability of significant public
exposure.Examples:[7]Sellafield (United Kingdom) five incidents
from 1955 to 1979.[13]SL-1 Experimental Power Station (United
States) 1961, reactor reached prompt criticality, killing three
operators.Saint-Laurent Nuclear Power Plant (France) 1969, partial
core meltdown; 1980, graphite overheating.Buenos Aires (Argentina)
1983, criticality accident on research reactor RA-2 during fuel rod
rearrangement killed one operator and injured two others.Jaslovsk
Bohunice (Czechoslovakia) 1977, contamination of reactor
building.Tokaimura nuclear accident (Japan) 1999, three
inexperienced operators at a reprocessing facility caused a
criticality accident; two of them died.Level 3: Serious
incident[edit]Impact on people and environmentExposure in excess of
ten times the statutory annual limit for workers.Non-lethal
deterministic health effect (e.g., burns) from radiation.Impact on
radiological barriers and controlExposure rates of more than 1 Sv/h
in an operating area.Severe contamination in an area not expected
by design, with a low probability of significant public
exposure.Impact on defence-in-depthNear-accident at a nuclear power
plant with no safety provisions remaining.Lost or stolen highly
radioactive sealed source.Misdelivered highly radioactive sealed
source without adequate procedures in place to handle
it.Examples: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.Davis-Besse Nuclear
Power Station (United States), 2002; negligent inspections resulted
in corrosion through 6 inches (15.24 cm) of the carbon steel
reactor head leaving only 38 inch (9.5 mm) of stainless steel
cladding holding back the high-pressure (~2500 psi, 17 MPa) reactor
coolant.Level 2: Incident[edit]Impact on people and
environment.Exposure of a member of the public in excess of 10
mSv.Exposure of a worker in excess of the statutory annual
limits.Impact on radiological barriers and controlRadiation levels
in an operating area of more than 50 mSv/h.Significant
contamination within the facility into an area not expected by
design.Impact on defence-in-depthSignificant failures in safety
provisions but with no actual consequences.Found highly radioactive
sealed orphan source, device or transport package with safety
provisions intact.Inadequate packaging of a highly radioactive
sealed source.Examples:Blayais Nuclear Power Plant flood (France)
December 1999Asc Nuclear Power Plant (Spain) April 2008;
radioactive contamination.Forsmark Nuclear Power Plant (Sweden)
July 2006; backup generator failure; two were online but fault
could have caused all four to fail.Gundremmingen Nuclear Power
Plant (Germany) 1977; weather caused short-circuit of high-tension
power lines and rapid shutdown of reactorShika Nuclear Power Plant
(Japan) 1999; criticality incident caused by dropped control rods,
covered up until 2007.[14]Level 1: Anomaly[edit]Impact on
defence-in-depthOverexposure of a member of the public in excess of
statutory annual limits.Minor problems with safety components with
significant defence-in-depth remaining.Low activity lost or stolen
radioactive source, device or transport package.(Arrangements for
reporting minor events to the public differ from country to
country. It is difficult to ensure precise consistency in rating
events between INES Level-1 and Below scale/Level-0)Examples:Penly
(Seine-Maritime, France) 5 April 2012; an abnormal leak on the
primary circuit of the reactor n2 was found in the evening of 5
April 2012 after a fire in reactor n2 around noon was
extinguished.[15]Gravelines (Nord, France), 8 August 2009; during
the annual fuel bundle exchange in reactor #1, a fuel bundle
snagged on to the internal structure. Operations were stopped, the
reactor building was evacuated and isolated in accordance with
operating procedures.[16]TNPC (Drme, France), July 2008; leak of
18,000 litres (4,000impgal; 4,800USgal) of water containing 75
kilograms (165lb) of unenriched uranium into the
environment.[17]Level 0: Deviation[edit]No safety
significance.5
6 Levels of International Nuclear EventsLevel 4Release of
radioactive materialAt lease one death from radiation0.1% release
of core inventoryHigh probability of significant public
exposure
Level 7: Major accident[edit]Impact on people and
environmentMajor release of radioactive material with widespread
health and environmental effects requiring implementation of
planned and extended countermeasuresThere 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 (official WHO estimate) 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 permanent 30 kilometres
(19mi) exclusion zone around the reactor was established.Fukushima
Daiichi nuclear disaster, a series of events beginning on 11 March
2011. A month later the Japanese government's nuclear safety agency
rated it level 7.[2][3] Major damage to the backup power and
containment systems caused by the 2011 Thoku 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] A temporary exclusion zone of 20 kilometres (12mi) was
established around the plant as well as a 30 kilometres (19mi)
voluntary evacuation zone;[5] In addition, the evacuation of Tokyo
Japan's capital and the world's most populous metropolitan area,
225 kilometres (140mi) away was at one point considered.[6] See
also 2011 Japanese nuclear accidents.See also: Comparison of
Fukushima and Chernobyl nuclear accidentsLevel 6: Serious
accident[edit]Impact on people and environmentSignificant release
of radioactive material likely to require implementation of planned
countermeasures.There has been only one such event to date:Kyshtym
disaster at Mayak Chemical Combine (MCC) Soviet Union, 29 September
1957. A failed cooling system at a military nuclear waste
reprocessing facility caused a steam explosion with a force
equivalent to 70-100 tons of TNT. About 70 to 80 metric tons of
highly radioactive material were carried into the surrounding
environment. The impact on local population is not fully known, but
at least 22 villages were affected with deadly doses.[7]Level 5:
Accident with wider consequences[edit]Impact on people and
environmentLimited release of radioactive material likely to
require implementation of some planned countermeasures.Several
deaths from radiation.Impact on radiological barriers and
controlSevere damage to reactor core.Release of large quantities of
radioactive material within an installation with a high probability
of significant public exposure. This could arise from a major
criticality accident or fire.Examples:[7]Windscale fire (United
Kingdom), 10 October 1957.[8] Annealing of graphite moderator at a
military air-cooled reactor caused the graphite and the metallic
uranium fuel to catch fire, releasing radioactive pile material as
dust into the environment.Three Mile Island accident near
Harrisburg, Pennsylvania (United States), 28 March 1979.[9] A
combination of design and operator errors caused a gradual loss of
coolant, leading to a partial meltdown. An unknown amount of
radioactive gases were released into the atmosphere, so injuries
and sicknesses that have been attributed to this accident can be
deduced from epidemiological studies but can never be proven.First
Chalk River accident,[10][11] Chalk River, Ontario (Canada), 12
December 1952. Reactor core damaged.Lucens partial core meltdown
(Switzerland), 21 January 1969. A test reactor built in an
underground cavern suffered a loss-of-coolant accident during a
startup, leading to a partial core meltdown and massive radioactive
contamination of the cavern, which was then sealed.[12]Goinia
accident (Brazil), 13 September 1987. An unsecured caesium chloride
radiation source left in an abandoned hospital was recovered by
scavenger thieves unaware of its nature and sold at a scrapyard.
249 people were contaminated and 4 died.Level 4: Accident with
local consequences[edit]Impact on people and environmentMinor
release of radioactive material unlikely to result in
implementation of planned countermeasures other than local food
controls.At least one death from radiation.Impact on radiological
barriers and controlFuel melt or damage to fuel resulting in more
than 0.1% release of core inventory.Release of significant
quantities of radioactive material within an installation with a
high probability of significant public
exposure.Examples:[7]Sellafield (United Kingdom) five incidents
from 1955 to 1979.[13]SL-1 Experimental Power Station (United
States) 1961, reactor reached prompt criticality, killing three
operators.Saint-Laurent Nuclear Power Plant (France) 1969, partial
core meltdown; 1980, graphite overheating.Buenos Aires (Argentina)
1983, criticality accident on research reactor RA-2 during fuel rod
rearrangement killed one operator and injured two others.Jaslovsk
Bohunice (Czechoslovakia) 1977, contamination of reactor
building.Tokaimura nuclear accident (Japan) 1999, three
inexperienced operators at a reprocessing facility caused a
criticality accident; two of them died.Level 3: Serious
incident[edit]Impact on people and environmentExposure in excess of
ten times the statutory annual limit for workers.Non-lethal
deterministic health effect (e.g., burns) from radiation.Impact on
radiological barriers and controlExposure rates of more than 1 Sv/h
in an operating area.Severe contamination in an area not expected
by design, with a low probability of significant public
exposure.Impact on defence-in-depthNear-accident at a nuclear power
plant with no safety provisions remaining.Lost or stolen highly
radioactive sealed source.Misdelivered highly radioactive sealed
source without adequate procedures in place to handle
it.Examples: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.Davis-Besse Nuclear
Power Station (United States), 2002; negligent inspections resulted
in corrosion through 6 inches (15.24 cm) of the carbon steel
reactor head leaving only 38 inch (9.5 mm) of stainless steel
cladding holding back the high-pressure (~2500 psi, 17 MPa) reactor
coolant.Level 2: Incident[edit]Impact on people and
environment.Exposure of a member of the public in excess of 10
mSv.Exposure of a worker in excess of the statutory annual
limits.Impact on radiological barriers and controlRadiation levels
in an operating area of more than 50 mSv/h.Significant
contamination within the facility into an area not expected by
design.Impact on defence-in-depthSignificant failures in safety
provisions but with no actual consequences.Found highly radioactive
sealed orphan source, device or transport package with safety
provisions intact.Inadequate packaging of a highly radioactive
sealed source.Examples:Blayais Nuclear Power Plant flood (France)
December 1999Asc Nuclear Power Plant (Spain) April 2008;
radioactive contamination.Forsmark Nuclear Power Plant (Sweden)
July 2006; backup generator failure; two were online but fault
could have caused all four to fail.Gundremmingen Nuclear Power
Plant (Germany) 1977; weather caused short-circuit of high-tension
power lines and rapid shutdown of reactorShika Nuclear Power Plant
(Japan) 1999; criticality incident caused by dropped control rods,
covered up until 2007.[14]Level 1: Anomaly[edit]Impact on
defence-in-depthOverexposure of a member of the public in excess of
statutory annual limits.Minor problems with safety components with
significant defence-in-depth remaining.Low activity lost or stolen
radioactive source, device or transport package.(Arrangements for
reporting minor events to the public differ from country to
country. It is difficult to ensure precise consistency in rating
events between INES Level-1 and Below scale/Level-0)Examples:Penly
(Seine-Maritime, France) 5 April 2012; an abnormal leak on the
primary circuit of the reactor n2 was found in the evening of 5
April 2012 after a fire in reactor n2 around noon was
extinguished.[15]Gravelines (Nord, France), 8 August 2009; during
the annual fuel bundle exchange in reactor #1, a fuel bundle
snagged on to the internal structure. Operations were stopped, the
reactor building was evacuated and isolated in accordance with
operating procedures.[16]TNPC (Drme, France), July 2008; leak of
18,000 litres (4,000impgal; 4,800USgal) of water containing 75
kilograms (165lb) of unenriched uranium into the
environment.[17]Level 0: Deviation[edit]No safety
significance.6
7 Levels of International Nuclear EventsLevel 7Major release of
radioactive materialSeveral deaths from radiationWidespread impact
on environment and public health
Level 7: Major accident[edit]Impact on people and
environmentMajor release of radioactive material with widespread
health and environmental effects requiring implementation of
planned and extended countermeasuresThere 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 (official WHO estimate) 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 permanent 30 kilometres
(19mi) exclusion zone around the reactor was established.Fukushima
Daiichi nuclear disaster, a series of events beginning on 11 March
2011. A month later the Japanese government's nuclear safety agency
rated it level 7.[2][3] Major damage to the backup power and
containment systems caused by the 2011 Thoku 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] A temporary exclusion zone of 20 kilometres (12mi) was
established around the plant as well as a 30 kilometres (19mi)
voluntary evacuation zone;[5] In addition, the evacuation of Tokyo
Japan's capital and the world's most populous metropolitan area,
225 kilometres (140mi) away was at one point considered.[6] See
also 2011 Japanese nuclear accidents.See also: Comparison of
Fukushima and Chernobyl nuclear accidentsLevel 6: Serious
accident[edit]Impact on people and environmentSignificant release
of radioactive material likely to require implementation of planned
countermeasures.There has been only one such event to date:Kyshtym
disaster at Mayak Chemical Combine (MCC) Soviet Union, 29 September
1957. A failed cooling system at a military nuclear waste
reprocessing facility caused a steam explosion with a force
equivalent to 70-100 tons of TNT. About 70 to 80 metric tons of
highly radioactive material were carried into the surrounding
environment. The impact on local population is not fully known, but
at least 22 villages were affected with deadly doses.[7]Level 5:
Accident with wider consequences[edit]Impact on people and
environmentLimited release of radioactive material likely to
require implementation of some planned countermeasures.Several
deaths from radiation.Impact on radiological barriers and
controlSevere damage to reactor core.Release of large quantities of
radioactive material within an installation with a high probability
of significant public exposure. This could arise from a major
criticality accident or fire.Examples:[7]Windscale fire (United
Kingdom), 10 October 1957.[8] Annealing of graphite moderator at a
military air-cooled reactor caused the graphite and the metallic
uranium fuel to catch fire, releasing radioactive pile material as
dust into the environment.Three Mile Island accident near
Harrisburg, Pennsylvania (United States), 28 March 1979.[9] A
combination of design and operator errors caused a gradual loss of
coolant, leading to a partial meltdown. An unknown amount of
radioactive gases were released into the atmosphere, so injuries
and sicknesses that have been attributed to this accident can be
deduced from epidemiological studies but can never be proven.First
Chalk River accident,[10][11] Chalk River, Ontario (Canada), 12
December 1952. Reactor core damaged.Lucens partial core meltdown
(Switzerland), 21 January 1969. A test reactor built in an
underground cavern suffered a loss-of-coolant accident during a
startup, leading to a partial core meltdown and massive radioactive
contamination of the cavern, which was then sealed.[12]Goinia
accident (Brazil), 13 September 1987. An unsecured caesium chloride
radiation source left in an abandoned hospital was recovered by
scavenger thieves unaware of its nature and sold at a scrapyard.
249 people were contaminated and 4 died.Level 4: Accident with
local consequences[edit]Impact on people and environmentMinor
release of radioactive material unlikely to result in
implementation of planned countermeasures other than local food
controls.At least one death from radiation.Impact on radiological
barriers and controlFuel melt or damage to fuel resulting in more
than 0.1% release of core inventory.Release of significant
quantities of radioactive material within an installation with a
high probability of significant public
exposure.Examples:[7]Sellafield (United Kingdom) five incidents
from 1955 to 1979.[13]SL-1 Experimental Power Station (United
States) 1961, reactor reached prompt criticality, killing three
operators.Saint-Laurent Nuclear Power Plant (France) 1969, partial
core meltdown; 1980, graphite overheating.Buenos Aires (Argentina)
1983, criticality accident on research reactor RA-2 during fuel rod
rearrangement killed one operator and injured two others.Jaslovsk
Bohunice (Czechoslovakia) 1977, contamination of reactor
building.Tokaimura nuclear accident (Japan) 1999, three
inexperienced operators at a reprocessing facility caused a
criticality accident; two of them died.Level 3: Serious
incident[edit]Impact on people and environmentExposure in excess of
ten times the statutory annual limit for workers.Non-lethal
deterministic health effect (e.g., burns) from radiation.Impact on
radiological barriers and controlExposure rates of more than 1 Sv/h
in an operating area.Severe contamination in an area not expected
by design, with a low probability of significant public
exposure.Impact on defence-in-depthNear-accident at a nuclear power
plant with no safety provisions remaining.Lost or stolen highly
radioactive sealed source.Misdelivered highly radioactive sealed
source without adequate procedures in place to handle
it.Examples: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.Davis-Besse Nuclear
Power Station (United States), 2002; negligent inspections resulted
in corrosion through 6 inches (15.24 cm) of the carbon steel
reactor head leaving only 38 inch (9.5 mm) of stainless steel
cladding holding back the high-pressure (~2500 psi, 17 MPa) reactor
coolant.Level 2: Incident[edit]Impact on people and
environment.Exposure of a member of the public in excess of 10
mSv.Exposure of a worker in excess of the statutory annual
limits.Impact on radiological barriers and controlRadiation levels
in an operating area of more than 50 mSv/h.Significant
contamination within the facility into an area not expected by
design.Impact on defence-in-depthSignificant failures in safety
provisions but with no actual consequences.Found highly radioactive
sealed orphan source, device or transport package with safety
provisions intact.Inadequate packaging of a highly radioactive
sealed source.Examples:Blayais Nuclear Power Plant flood (France)
December 1999Asc Nuclear Power Plant (Spain) April 2008;
radioactive contamination.Forsmark Nuclear Power Plant (Sweden)
July 2006; backup generator failure; two were online but fault
could have caused all four to fail.Gundremmingen Nuclear Power
Plant (Germany) 1977; weather caused short-circuit of high-tension
power lines and rapid shutdown of reactorShika Nuclear Power Plant
(Japan) 1999; criticality incident caused by dropped control rods,
covered up until 2007.[14]Level 1: Anomaly[edit]Impact on
defence-in-depthOverexposure of a member of the public in excess of
statutory annual limits.Minor problems with safety components with
significant defence-in-depth remaining.Low activity lost or stolen
radioactive source, device or transport package.(Arrangements for
reporting minor events to the public differ from country to
country. It is difficult to ensure precise consistency in rating
events between INES Level-1 and Below scale/Level-0)Examples:Penly
(Seine-Maritime, France) 5 April 2012; an abnormal leak on the
primary circuit of the reactor n2 was found in the evening of 5
April 2012 after a fire in reactor n2 around noon was
extinguished.[15]Gravelines (Nord, France), 8 August 2009; during
the annual fuel bundle exchange in reactor #1, a fuel bundle
snagged on to the internal structure. Operations were stopped, the
reactor building was evacuated and isolated in accordance with
operating procedures.[16]TNPC (Drme, France), July 2008; leak of
18,000 litres (4,000impgal; 4,800USgal) of water containing 75
kilograms (165lb) of unenriched uranium into the
environment.[17]Level 0: Deviation[edit]No safety
significance.7
A deeper look intoTokaimura, JapanThree Mile Island, United
States of AmericaFukushima, Japan8
Tokaimura, Japan (1999) 9
Uranium 235
Design - Geometrical control
Direct cause of disaster16 kg of high enriched uranium filled in
precipitation basin which can be filled with no more than 2.9
kg.10
Tokaimuru precipitation tank 11
Tokaimuru precipitation tank
12
Point of criticality?Uncontrolled nuclear fission:
Self-sustainingIntense gamma and neutron radiation13
LessonsNot designed to counter criticality (lack of geometrical
design)Built in the middle of residential areaPossibility of
criticality accidents was not included when site review was
doneUnqualified workers 14
Three mile Island, usaMarch 28, 19793:58 am15
Violent Shaking of pumps
15
Decision?Coolant turned off.EffectCore heating up to 2000OC +At
5000OC rods would melt and burn through the 8 inch thick steel
reactor into the groundConcurrent activities Poor communication
between operators and experts due to single phone lineRadiation
detected in control roomMarch 28, 19797:15 am16
Still trying to stabilize Radiation on top of containment high
enough to kill a man in 20 secondsMarch 28, 197910:17 amRadiation
leaking out of the plant March 28, 197911:00 amContact made! Pumps
restarted March 28, 19797:33 pmCoolant sample required to assess
situationPublic given no details. March 29, 19798:30 am17
Basement filled with radioactive water giving off radioactive
gasOrdered to vent gas into atmosphere March 29, 19798:30
amEvacuation! March 30, 19798:00 amLarge amounts of hydrogen gas at
the top of the containment dome April 1, 197910:00 am
Disaster averted.18
LessonsKnow what each button and light represents in the control
roomPoor planningDesigners were not accessibleExperts were not
accessible 19
Fukushima, JapanEarthquake with 9.0 magnitude 5 nuclear plants
in disaster zone (Fukushima was the largest)Power loss Emergency
generators turned onMarch 11, 20112:46 pmTsunami warning March 11,
20112:5520
Fukushima, JapanEarthquake with 9.0 magnitude 5 nuclear plants
in disaster zone (Fukushima was the largest)Power loss Emergency
generators turned onMarch 11, 20112:46 pmTsunami warning March 11,
20112:5521
Tsunami hitsAll power lost Two workers die March 11, 20113:27 pm
Power plant evacuated one team stayed behindRequired mobile power
generators but transport was difficultMarch 11, 20113:37 pm Battery
packs and car batteries used to make key readingsPressure inside
core risingMarch 11, 20116:08 pm22
Tsunami hitsAll power lost Two workers die March 11, 20113:27 pm
Power plant evacuated one team stayed behindRequired mobile power
generators but transport was difficultMarch 11, 20113:37 pm Battery
packs and car batteries used to make key readingsPressure inside
core risingMarch 11, 20116:08 pm23
Minister advised operators to release steam from the valves
March 11, 20117:03 pm Valves had to opened manually, difficult to
locate themCracked reactor (of 15 cm steel) was discovered Plant
will without power March 11, 20119:00 pmPressure in reactor 1 was
so high that it was feared that the reactors might explode24
Evacuation!March 12, 20116:00 am Poor communication between
managers and operators Valves still not openMarch 12, 20117:00
pmValves opened March 13, 201110:16 am
March 13, 20113:36 pmReactor 1 explodesReactor 2 and 3 damaged
25
Fukushima 50 still has no control over the reactor March 13,
201111:01 pm Explosion in building 4 causes a fireMarch 14,
20116:00 am26
LessonsFlaws in original design more concerned with risk of
EarthquakeTsunami walls were too low Poor location of diesel
generators Thin layer of Zirconium around the rods in the reactor
which over heated and became highly reactive27
https://www.youtube.com/watch?v=fyIBlygNlcchttp://america.aljazeera.com/content/dam/ajam/images/articles_2014/06/european_nuclear_power_plant_a.jpghttps://en.wikipedia.org/wiki/International_Nuclear_Event_Scalehttp://www.ucsusa.org/clean_energy/our-energy-choices/energy-and-water-use/water-energy-electricity-cooling-power-plant.html#.Vk_afYRifuJhttp://www.ucsusa.org/clean_energy/our-energy-choices/energy-and-water-use/water-energy-electricity-nuclear.html#.Vk_agYRifuJhttps://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disasterhttps://www.youtube.com/watch?v=gWPnJanzvjIhttp://www.prn.usm.my/old_website/mainsite/headline/poison/oct99.htmlhttp://www.world-nuclear.org/info/safety-and-security/safety-of-plants/tokaimura-criticality-accident/http://www.energyadvocate.com/tokai.htmhttp://www.sciencedirect.com/science/article/pii/0891391957900190https://en.wikipedia.org/wiki/Nuclear_reactor_safety_systemshttps://chemtrailsplanet.files.wordpress.com/2012/12/fukushima-tsunami.jpghttp://www.occupy.com/sites/default/files/field/image/fukushima_nuclear_2-other.jpghttps://en.wikipedia.org/wiki/National_Research_Universal_reactorhttps://upload.wikimedia.org/wikipedia/commons/2/2d/RA6cab.jpghttps://es.wikipedia.org/wiki/Accidente_nuclear_del_reactor_RA-2https://en.wikipedia.org/wiki/Criticality_accidenthttps://en.wikipedia.org/wiki/Forsmark_Nuclear_Power_Planthttps://en.wikipedia.org/wiki/1999_Blayais_Nuclear_Power_Plant_floodhttp://nuclear-energy.net/situation/nuclear-power-argentina.htmlhttps://en.wikipedia.org/wiki/Krko_Nuclear_Power_Plant#/media/File:2010_floods_in_Slovenia_(15).jpghttps://en.wikipedia.org/wiki/International_Nuclear_Event_Scale#Level_0:_Deviationhttp://brainlagoon.com/2013/01/08/5-worst-nuclear-accidents-in-history-2/https://www.e-education.psu.edu/egee102/node/1929
References28
