Nuclear Power Nuclear Power Plant AccidentsPlant Accidents

Reporters:Reporters:Uyangurin, Mareinne L. Suico, Uyangurin, Mareinne L. Suico, Monica Sharlyn L.Monica Sharlyn L.

Waresa, Daryl Mae B.Waresa, Daryl Mae B.

Chernobyl Nuclear Chernobyl Nuclear Power Plant AccidentPower Plant Accident The Chernobyl accident is the most serious The Chernobyl accident is the most serious

accident in the history of the nuclear accident in the history of the nuclear industry. The Chernobyl nuclear power plant industry. The Chernobyl nuclear power plant is located in Ukraine, 20km south of the is located in Ukraine, 20km south of the border with Belarus. At the time of the border with Belarus. At the time of the accident, the plant had four working reactors.accident, the plant had four working reactors.

The accident occurred on 26 April 1986 when The accident occurred on 26 April 1986 when operators of the power plant ran a test on an operators of the power plant ran a test on an electric control system of one of the reactors. electric control system of one of the reactors.

The accident happened because of a The accident happened because of a combination of basic engineering combination of basic engineering deficiencies in the reactor and faulty deficiencies in the reactor and faulty actions of the operators: the safety systems actions of the operators: the safety systems had been switched off, and the reactor was had been switched off, and the reactor was being operated under improper, unstable being operated under improper, unstable conditions, a situation which allowed an conditions, a situation which allowed an uncontrollable power surge to occur.uncontrollable power surge to occur.

This led to a cascade of events resulting in This led to a cascade of events resulting in a series of explosions and consequent fires a series of explosions and consequent fires that severely damaged the reactor that severely damaged the reactor building, completely destroyed the reactor, building, completely destroyed the reactor, and caused the release of massive amounts and caused the release of massive amounts of radioactive materials over a ten-day of radioactive materials over a ten-day period.period.

The cloud from the burning reactor spread The cloud from the burning reactor spread many types of radioactive materials, many types of radioactive materials, especially iodine-131 and caesium-137, over especially iodine-131 and caesium-137, over much of Europe. Because radioactive iodine much of Europe. Because radioactive iodine disintegrates rapidly, it largely disappeared disintegrates rapidly, it largely disappeared within the first few weeks of the accident. within the first few weeks of the accident. Radioactive caesium however is still Radioactive caesium however is still measurable in soils and some foodstuffs in measurable in soils and some foodstuffs in many parts of Europe. The greatest many parts of Europe. The greatest concentrations of contamination occurred concentrations of contamination occurred over large areas of the Soviet Union over large areas of the Soviet Union surrounding the reactor in what are now the surrounding the reactor in what are now the countries of Belarus, the Russian Federation countries of Belarus, the Russian Federation and Ukraine. and Ukraine.

Before...Before...

After...After...

After...After...

Chernobyl Human Chernobyl Human EffectsEffects

•What caused the nuclear What caused the nuclear crisis?crisis? Problems began when Friday's massive Problems began when Friday's massive

earthquake knocked out electricity at the earthquake knocked out electricity at the Fukushima No 1 power station. Back-up Fukushima No 1 power station. Back-up generators kicked in to pump coolant generators kicked in to pump coolant around the reactor cores to prevent the around the reactor cores to prevent the fuel rods from overheating. The generators fuel rods from overheating. The generators worked for a short time, but were worked for a short time, but were damaged by the ensuing tsunami, forcing a damaged by the ensuing tsunami, forcing a scramble by engineers to fit mobile battery scramble by engineers to fit mobile battery power units. These were insufficient to power units. These were insufficient to cool all of the reactors properly.cool all of the reactors properly.

•Why did the building Why did the building explode?explode?

The makeshift attempt to cool reactor 1 at the The makeshift attempt to cool reactor 1 at the power station failed. Heat from the fuel rods power station failed. Heat from the fuel rods in the reactor core led to a build-up of in the reactor core led to a build-up of superheated water inside.superheated water inside.

On Saturday, engineers released water On Saturday, engineers released water vapour – which contained radioactive caesium vapour – which contained radioactive caesium and iodine – from the pressure vessel as an and iodine – from the pressure vessel as an emergency measure. Superheated water can emergency measure. Superheated water can split into hydrogen and oxygen, and it split into hydrogen and oxygen, and it appears that hydrogen escaped during the appears that hydrogen escaped during the venting procedure and exploded.venting procedure and exploded.

•What damage was What damage was caused?caused?

The blast tore the roof off the building The blast tore the roof off the building and damaged surrounding walls. Four and damaged surrounding walls. Four workers were injured. Japanese workers were injured. Japanese authorities told the International authorities told the International Atomic Energy Authority that the Atomic Energy Authority that the explosion happened outside the explosion happened outside the reactor's primary containment vessel, reactor's primary containment vessel, which appears to be intact. which appears to be intact.

•What is the radiation What is the radiation risk?risk? Japan's Nuclear and Industrial Safety Agency Japan's Nuclear and Industrial Safety Agency

(Nisa) reported higher levels of radiation (Nisa) reported higher levels of radiation around the power station over the weekend and around the power station over the weekend and the presence of caesium-137 and iodine-131 in the presence of caesium-137 and iodine-131 in the air. These are radioactive isotopes produced the air. These are radioactive isotopes produced in fission reactions. The isotopes were released in fission reactions. The isotopes were released when steam was vented from the reactor.when steam was vented from the reactor.

Monitors around the site recorded a radiation Monitors around the site recorded a radiation level of 500 microSieverts per hour on Saturday level of 500 microSieverts per hour on Saturday afternoon, a quarter of the annual dose the afternoon, a quarter of the annual dose the general population is exposed to due to natural general population is exposed to due to natural background radiation. The level of radiation at background radiation. The level of radiation at the power station's main gate fell on Sunday to the power station's main gate fell on Sunday to a very low level of 3.2 microSieverts.a very low level of 3.2 microSieverts.

•Have people been Have people been exposed to radiation?exposed to radiation?

At least nine people have tested positive for At least nine people have tested positive for radiation exposure near Fukushima, but a radiation exposure near Fukushima, but a Nisa official said that number could rise to Nisa official said that number could rise to between 70 and 160. Radioactivity can cause a between 70 and 160. Radioactivity can cause a variety of health problems, from a reddening variety of health problems, from a reddening of the skin and increased cancer risk to fatal of the skin and increased cancer risk to fatal radiation sickness. Health officials distributed radiation sickness. Health officials distributed potassium iodide pills, which protect against potassium iodide pills, which protect against thyroid cancers, to residents near the power thyroid cancers, to residents near the power station. Those unable to leave were advised to station. Those unable to leave were advised to limit their exposure by staying indoors and limit their exposure by staying indoors and switching off air conditioning or wearing a switching off air conditioning or wearing a protective mask if outside. protective mask if outside.

•Are the other reactors Are the other reactors safe?safe?

On Sunday, engineers vented steam from On Sunday, engineers vented steam from reactor 3 and began pumping in sea water reactor 3 and began pumping in sea water after its cooling system failed.Authorities after its cooling system failed.Authorities said there was a risk of an explosion similar said there was a risk of an explosion similar to that in reactor 1. Sea water was being to that in reactor 1. Sea water was being readied to pump into reactor 2.readied to pump into reactor 2.

A separate state of emergency was A separate state of emergency was announced at the nearby Onagawa nuclear announced at the nearby Onagawa nuclear power station amid increased levels of power station amid increased levels of radiation, but Japanese officials said this had radiation, but Japanese officials said this had been carried on the wind from Fukushima.been carried on the wind from Fukushima.

•When will the power When will the power station be safe?station be safe?

The strategy of pumping sea water into nuclear The strategy of pumping sea water into nuclear reactors is untested. It could take several days to reactors is untested. It could take several days to bring the temperature and pressure of the bring the temperature and pressure of the reactor cores down to within safe limits.reactor cores down to within safe limits.

If the cooling fails, the reactors could overheat If the cooling fails, the reactors could overheat and cause a total meltdown of the radioactive and cause a total meltdown of the radioactive fuel rods in the core. This would only lead to a fuel rods in the core. This would only lead to a major release of radiation if the reactor's major release of radiation if the reactor's containment vessel was breached.containment vessel was breached.

The Japanese authorities have classified The Japanese authorities have classified the situation as a level 4 "accident with the situation as a level 4 "accident with local consequences" on the International local consequences" on the International Nuclear and Radiological Event Scale.The Nuclear and Radiological Event Scale.The scale runs from zero for a deviation in scale runs from zero for a deviation in normal operations to seven for a major normal operations to seven for a major accident. The Three Mile Island incident accident. The Three Mile Island incident in 1979 was a five and Chernobyl in 1986 in 1979 was a five and Chernobyl in 1986 was a seven on the scale.was a seven on the scale.

So, here are some images So, here are some images in the Fukushima Nuclear in the Fukushima Nuclear

Power Plant…Power Plant…

Fukushima Power Plant (upper view)Fukushima Power Plant (upper view)

Fukushima Power Plant Fukushima Power Plant parts …parts …

Before …Before …

After …After …

Explode !Explode !!!

Fire !!Fire !!