Comparing Fukushima, Chernobyl, Three Mile Accidents: Q&A

By Adi Narayan
Mar 17, 2011

March 15 (Bloomberg) — Radiation leaks from Tokyo Electric Power Co.’s earthquake-stricken reactors in northeastern Japan represent the worst nuclear power accident since the meltdown at Chernobyl, Ukraine, almost 25 years ago, scientists say.

Military helicopters are dumping water on containers holding spent uranium fuel to prevent them from overheating after the March 11 earthquake and tsunami disabled a cooling system, Tokyo Electric spokesman Kaoru Yoshida told reporters yesterday. Once exposed, the spent fuel rods may catch fire and melt, spewing radiation into the atmosphere.

“Radiation levels are extremely high, which could possibly impact the ability to take corrective measures,” U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko told a congressional panel in Washington yesterday.

Here are answers to some frequently asked questions about the accidents at Fukushima, Chernobyl in 1986 and Three Mile Island, Pennsylvania, in 1979. The information is drawn from the U.S. Nuclear Regulatory Commission in Washington, the World Health Organization in Geneva and interviews with radiation safety experts in the U.S., Australia and India.

Q: How do the three accidents compare?

A: The event at Fukushima is ongoing. The disaster now ranks 6 on a 7-step international scale for nuclear accidents, according to Andre-Claude Lacoste, head of France’s nuclear safety authority.

The International Atomic Energy Agency hasn’t updated the original rating of 4 on its website. Three Mile Island was rated 5 and Chernobyl was rated 7. Each additional point on this scale represents a factor of 10, so the accident at Three Mile Island was 1/100th as serious as Chernobyl, according to the agency.

Q: How did the reactors differ?

A: Fukushima’s 40-year-old reactor No. 2 used nuclear fission to heat water into steam, which powered a turbine. Such units are called boiling water reactors.

In the plant at Three Mile Island, pressurized water is pumped into the reactor core, where it gets heated. The hot water is then sent to a steam generator which is located outside the uranium-containing chamber. Both the Fukushima and Three Mile reactors had steel casings to protect nuclear fuel.

Fuel inside Chernobyl’s unit 4 wasn’t protected by steel. The reactor’s graphite buffer, used to slow high-speed subatomic particles, caught fire. The Fukushima and Three Mile reactors used water for the same purpose.

Q: What happened at Three Mile Island?

A: On March 28, 1979, unit 2 suffered a partial meltdown after water meant for cooling the uranium fuel was released from the containment chamber due to an equipment malfunction. There was no explosion and radioactive materials weren’t released into the environment because the chamber didn’t rupture.

Q: What happened at Chernobyl?

A: The accident was caused by a power surge that led to overheating at reactor No. 4. A resultant fire and explosions caused the containment roof to cave in and sent radioactive debris, including pieces of fuel rod, spewing into the air, destroying a nearby forest.

Radiation outside the blast area was about 50 times greater than the peak inside Fukushima, and at least 31 workers and firefighters died within a few months. An estimated 4,000 children and adolescents developed thyroid cancer after consuming milk contaminated with radioactive iodine, I-131.

Q: What are the sources of radiation at Fukushima?

A: Fuel rods at the plant’s No. 1 and No. 2 reactors, both of which were operating at the time of the temblor, may have been damaged, Tokyo Electric said. Pressure in the containment chamber of unit No. 2 fell yesterday, indicating that radiation may have been released after an explosion on March 15.

Radiation is also leaking from spent fuel rods stored in a pool near reactors No. 3 and No. 4. Water in the pool has evaporated due to radioactive heat, exposing the uranium- containing rods to the atmosphere. The exposed rods can emit radiation and give out radioactive iodine and cesium, both of which are cancer-causing agents.

A worker at the edge of the pool would receive a fatal radiation dose in 16 seconds, said David Lochbaum, a nuclear physicist for the Union of Concerned Scientists and a former Nuclear Regulatory Commission safety instructor.

There are six reactors in the Fukushima complex, of which three were operating at the time of the earthquake.

  1. #1 by nightfish3 on Thursday, 17 March 2011 - 7:10 pm

    and our morons here is building two reactors ,why don’t they build it next to putrajaya..a full bunch of jerks!! I will protest to my last breath.

  2. #2 by yhsiew on Thursday, 17 March 2011 - 8:40 pm

    Video System For Nuclear Plant

    One of the problems with the Fukushima Daiichi nuclear plant in Japan is that the plant does not have any camera system. As a result, the engineers do not know whether the fuel rods have melted or whether the spent fuel rods are above water-level and exposed to air. This makes troubleshooting of the plant extremely difficult. Their engineers can only fix the plant by trial and error.

    After the Three Mile Island nuclear accident in US, the US government passed a law to require all US nuclear plants to have a camera system installed.

    By today’s technology, I do not think it is that difficult to insert a video sensor into the nuclear reactor to check what is going on inside. A long pair of leads can be attached to the video sensor so that a portable electronic viewing unit can be connected to the other end of the leads to allow the engineer to observe, at a safe distance, what is going on inside the nuclear reactor.

  3. #3 by Godfather on Thursday, 17 March 2011 - 8:55 pm

    Singapore Straits Times, December 16, 2017:

    The Singapore Government today activated its emergency plan to relocate a substantial number of its population to Western Australia, China and other Pacific locations. The emergency laws have been invoked to make it compulsory for all non-essential personnel to get on to aircraft chartered by the government for this purpose. This follows the worsening situation in Malaysia where two nuclear reactors near Kuantan have exploded, sending a mushroom cloud visible for 100 kilometres in every direction.

    The nuclear facility in Malaysia, built in 2013 by the ruling administration amid charges of massive kickbacks by the Russian contractor, was to have been commissioned earlier this year, but disputes between the Russian contractor and its Malaysian subcontractors have contributed to the delay in commissioning. The recent explosions followed the sudden seizure of the salt-water pumps, resulting in serious spikes in temperature of the reactors. The Russian contractor could not react in time as the roof of the nuclear facility also collapsed due to incessant rain during the north-east monsoon.

    Efforts to reach the Malaysian government also failed as it was reported that the entire administration had already flown themselves and their dependents to the United Kingdom.

    It is expected that serious radiation levels will reach Singapore in 24 hours, and the government has decreed that all Singaporeans below the age of 30 and above the age of 60 have to evacuate from the city state. The rest of the Singaporeans have been supplied with protective gear against radiation.

  4. #4 by yhsiew on Thursday, 17 March 2011 - 9:57 pm

    After the Chernobyl accident (reactor vessel rupture), the Russian government sent 600,000 workers to seal the reactor pile. Some 4,000 of these workers eventually died of cancer or leukemia (check this evening’s China Press, page B7).

    The American army is sending an unmanned plane to fly over the Fukushima Daiichi nuclear plant in Japan. The infrared equipment on the plane will take picture of what is going on in the reactor room.

    Airfare to fly from Tokyo to Kuala Lumpur has increased from RM1,800 to RM4,000 and from Tokyo to Beijing has increased from around RM1,600 to RM8,360.

  5. #5 by tak tahan on Thursday, 17 March 2011 - 11:02 pm

    Cintanegara is in Japan now,according to pundits,trying hard to figure out how to handle the crisis.By the time our nation plans to build nuclear plants,we will be relief that cintanegara is already well equipped with the speciaty knowledge to bulldoze the launching of the nuclear plants.By the way.he also managed to negotiate through close tender his fruit juice for the cooling double-effect.Wa..chiak beh liau!

  6. #6 by undertaker888 on Friday, 18 March 2011 - 7:59 am

    no worry. in bolehland apa pun boleh. if we need water to cool down the reactor during a crisis, we have bomoh to do that. the ministry will employ some bomohs to call for rain. RM5billion should do the job.

    if that doesn’t work, we have our propanda minister nazri and perkosa telling us that we have another Malaysia Guinness world record. the highest radiation leak after chernobyl. so all Malaysian should be proud. Yeh!!! Boleh.

  7. #7 by k1980 on Friday, 18 March 2011 - 10:18 am

    Jib: “Cooling the reactors? Tak ada masalah. Here in Malaysia, the roofs are built to leak, so rainwater can always flow down to cool the reactors in case of meltdown. Clever, isn’t it?”

  8. #8 by littlefire on Friday, 18 March 2011 - 11:31 am

    Uncle Lim, other countries already advice or evacuate their people from Japan due to radiation concern. But why our G is still only standby mode?

    While Egypt can sent plane trip just to fetch all the students back so fast.. Why not Japan? We do have students, people working there right?

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