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FUKUSHIMA DAIICHI

NUCLEAR PLANT

DISASTER.

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Accident cause

11/03/2011, 2:46 p.m. local

time near the Japanese

island of Honshu was an

earthquake of 9 on the

Richter scale.The quake had an impact

on section of north-east

coast of Japan where they

are located a series of

nuclear power plants(NPP).

Nuclear reactors have

been shut down properly.

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NPP DAIICHI before the earthquake

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Timing of Reactor Events

Earthquake Begins Fri. 2:46 PM JSTReactor shuts down Fri. 2:48 PM JST

Off-grid, diesels provide power Seconds later

Reactor cooled by emergency systems After diesels start

Tsunami fails diesel generators Fri. ~3:45 PM JST

Battery powers control of steam-driven Reactor CoreIsolation Cooling (RCIC) and automatic depressurization

After diesels fail

Battery power exhausted Sat. ~12:00 AM JST

Report of suppression pool (wet well) becoming saturated Sat. ~2:00 AM JST

Containment pressure 0.6 MPa (0.4 MPa normal) Sat. ~2:00 AM JST

Steam vented from reactor to Refueling Bay Sat. 5:30 AM JST

Water level drops to top of active fuel -

Core oxidation occurs, releasing hydrogen -

Hydrogen Explosion/Deflagration Sat. 3:36 PM JST

Seawater injection begins Sun 8:20 PM JST

Slide 4

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INSIDE A REACTOR

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CORE

Suppression Systems 21

The Defense

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SAFETYLEVELS OF

RADIATION

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CHERNOBYL NUCLEARPOWER PLANT DISASTER.

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Chernobyl

Built in1978-

1979

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CHERNOBYL NPP

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25-26 April 1986

Engineers on the evening shift

at Chernobyl's number four

reactor began an experiment to

see whether the cooling pump

system could still function using

power generated from the

reactor under low power should

the auxiliary electricity supply

fail.

However, too many rods were

lowered and output dropped too

quickly, resulting in an almost

complete shutdown.

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Safety systems disabled

Concerned by possible instability,

engineers began to raise therods to increase output. At 0030

the decision was taken to carry

on. By 0100 power was still only

at about 7%, so more rods were

raised.

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The engineers continued to

raise rods. By 0123, power had

reached 12% and the testbegan. But seconds later, power

levels suddenly surged to

dangerous levels.

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With power at roughly 100 times

normal, fuel pellets in the core

began to explode, rupturing thefuel channels. At about 0124,

two explosions occurred,

causing the reactor's dome-

shaped roof to be blown off and

the contents to erupt outwards

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The Disaster

01:23:48

1st explosion

01:23:55

2nd explosion

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April 26, 1986: Chernobyl nuclear

power plant Operator errors cause areactor explosion

Explosion releases 190

tons of radioactive

gasses into the

atmosphere Fire starts that lasts 10

days

People: 7 million lived in

contaminated areas; 3million were children

Wind: Carries radiation far

distances

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