Transcript NUCLEAR MELTDOWN! Three Mile Island and Chernobyl

NUCLEAR MELTDOWN!
Three Mile Island and
Chernobyl
Draw Backs to Nuclear Power
• Thermal Pollution
• Nuclear Waste
• Meltdowns
– Three Mile Island
– Chernobyl
What is a Meltdown
• A meltdown occurs if a reactor loses
coolant water, exposing the reactor core.
• The temperature reaches 2800°C, the fuel
melts, and becomes a white-hot molten
mass.
• This melts its way through all the
containment vessels to the earth below
Three Mile Island
• March 29th ,1979
• Harrisburg, PA
What Happened
• Cleaning a feed water tank
– Clogged, tried to blow out the clog with an air
compressor
• Compressor lines had been connected to
a water line
– Water went into the air lines
Continued…
• Water caused the valves to close
(designed not to close, but never wired)
• Heat and pressure built up (couldn’t vent)
• Water couldn’t reach the
generators(valves closed!)
• Back-up valves had been closed a week
earlier (they were never closed)
• Indicator light covered with something…
And then what?
• A second indicator light showing a false
OK signal
• Operators struggled with mixed signals
from control panel…
• Finally realized the valve problem and
opened them.
Results
• Containment building flooded with
radioactive water
• Tremendous build up of steam and gas
(hydrogen and possibly oxygen)
• Worried of possible explosion- made the
decision to release radioactive gas into the
atmosphere
• Water had also been released, fuel rods
were damaged.
• No immediate deaths …
Chernobyl
• April 26, 1986
• former USSR (now Ukraine)
What Happened?
• Test to see if the plant could produce
enough power to run itself during a power
outage
• But not everyone was informed…
• Lack of cooling and too much pressure
caused a power surge (massive heat)
What happened continued…
• There were two explosions:
– The first explosion was a steam explosion
– Second explosion under debate- hydrogen?
– fuel, core components, structural items sent
into atmosphere
– Radioactive and “hot” material set into
atmosphere
– The plume of smoke went 1 km into the air
The Fires
• Several broke out after the explosions
• The fires - normal and graphite.
• Graphite fire caused the biggest release of
radiation
• Graphite fires too hot for water.
• Dropped 5000 tons of boron, dolomite,
sand, clay and lead to extinguish the
graphite fire.
• Extinguished finally after 20 days.
Radiation Release
• It is estimated that all of the xenon gas, about
half of the iodine and cesium, and at least 5% of
the remaining radioactive material in the reactor
core was released. Most of the released material
was deposited close by as dust and debris , but
the lighter material was carried by wind over the
Ukraine, Belarus, Russia and to some extent
over Scandinavia and Europe.
• Iodine-131 and cesium-137 were the main
radioactive hazards.
In Conclusion
• “…reactor design was poor from the
point of view of safety and
unforgiving for the operators”
• killed more than 30 people
immediately
• high radiation levels in the
surrounding 20-mile radius
• 135,00 people had to be evacuated
• 64% of all Ukrainian thyroid cancer
patients age 15 of younger live in the
most contaminated regions.
What are the chances Today?
• The chances of this happening have been
estimated at one in 100 million 'reactor years’.
– A fuel meltdown might be expected once out of
20,000 years of reactor operation.
– In 2 out of 3 meltdowns there would be no deaths.
– In 1 out of 5 meltdowns there would be 1000
deaths,
– In 1 out of 100,000 meltdowns there would be
50,000 deaths.
• Air pollution from coal-burning power plants causes
tens of thousands of deaths a year.
• There would have to be 25 meltdowns a year for
nuclear power to be as dangerous as coal.
Nuclear Power Sites in U.S.
Daily Radiation
Where you live
Radiation Survey