Fukushima vs Chernobyl vs Three Mile Island

Years after the disaster, some claim that Fukushima radiation is still going to cause widespread death.

by Brian Dunning

Filed under Environment, General Science, Health

Skeptoid #397
January 14, 2014
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Also available in Russian

Fukushima Chernobyl Three Miles Island
Three Mile Island
Photo: United States Department of Energy

In March of 2011, an undersea earthquake sent tsunamis thundering across Japan, killing nearly 20,000 people and creating the most expensive natural disaster in history. Among the casualities was the Fukushima Daiichi Nuclear Power Plant, which was almost completely submerged by the tsunamis; an unprecedented event. Power was lost (obviously), cooling systems stopped, and the net result was a complete meltdown of three of the plant's reactor cores. It was a perfect storm of worst case scenarios. And now, even years afterward, some are calling it a worldwide radiation disaster, worse than even Chernobyl, that will produce a staggering death count for decades or even centuries. Today we're going to evaluate these assertions and see if we can separate fact from fiction.

With the shocking end-of-the-world-scenario headlines — such as "Your Days of Eating Pacific Ocean Fish Are Over" and "28 Signs That The West Coast Is Being Absolutely Fried With Nuclear Radiation From Fukushima" — either Fukushima was the worst environmental disaster ever, or some of the worst misinformation ever is being trumpeted. To find out which, we'll put it into context with the two other best known nuclear disasters: the 1986 explosion of a reactor at the Chernobyl plant in the Ukraine, and the 1979 partial meltdown of a reactor at the Three Mile Island plant in Pennsylvania.

The most important technical point to understand about various reactor kinds is the moderator. The moderator is a substance that slows down the fast neutrons being shed by the radioactive uranium fuel, converts the kinetic energy into thermal energy, and turns them into slow, thermal neutrons. A thermal neutron is much more likely to strike another uranium nucleus. This allows a chain reaction, in which the fuel produces enough heat to power a conventional steam generator. Most nuclear reactors use water as the moderator. Put uranium fuel rods into water, in the proper configuration, and you'll get a chain reaction.

Chernobyl, however, was a very different type of machine. It was what we call an atomic pile, the devices first designed during World War II to produce plutonium for atomic weapons. The atomic pile is literally a pile of graphite blocks, half a meter long and a quarter meter square, with a hole bored through the long axis. These graphite blocks were used as the moderator.

The problem with building a reactor out of graphite blocks is that graphite burns. Contain burning graphite within a concrete structure, and it explodes. This is exactly what happened at Chernobyl, and it's exactly why nobody would ever build a graphite-moderated reactor today; the whole reactor core was literally a bomb waiting to go off.

Three Mile Island and Fukushima were both water moderated reactors. This was one of the most significant safety improvements of the early 1950s. Fukushima's basic design is one of the earliest, called a BWR (boiling water reactor). The moderating water, which is also the cooling water, is directly boiled and drives a steam generator. The reason the Fukushima accident happened is that all sources of power were destroyed by the tsunami, including backups, backups, and their backups; and without the pumps to keep the system circulating, the cooling water boiled completely away, and the fuel melted. For months, firehoses sprayed water into the open reactors to prevent open flames from pumping radioactive smoke into the atmosphere. This contaminated water was barely containable; it leaked into the ocean, and was stored in anything that could be used as a tank.

Three Mile Island's design was a step newer, called a PWR (pressurized water reactor), and is of the same basic type as most existing plants. The main incremental safety feature here is that the core is kept pressurized to prevent the water from being able to boil; and as water's temperature goes up, its ability to moderate neutrons goes down. Thus the system is self-regulating: If the core gets too hot, it stops working efficiently, so it cools back down.

But like any system, this one was prone to breakdowns and human error. A broken valve allowed coolant water out of the core, and a confusingly designed instrument panel fooled operators into thinking the opposite was happening, who then let more out. By the time they figured it out, enough damage had been done that radioactive water had been able to mix with the separate water that runs through the steam generators. That radioactive steam was then released through the plant's filtration system, which removed nearly all the dangerous contaminants.

Fortunately, at Three Mile Island, only a tiny amount of radiation was released. It was an expensive cleanup and repair, but it was effectively contained; none of the containment structures were breached. There were no injuries, nobody within 16 kilometers received more than a chest x-ray's worth of radiation, and epidemiological studies predicted zero eventual deaths.

At the opposite end of the spectrum was Chernobyl. Since the plant openly exploded, a huge amount of very dangerous radioactive debris was spread over a large area. Two people were killed outright by the explosion, and a few dozen first responders were dead of acute radiation poisoning within three months. Estimates of eventual deaths vary wildly, with the most extreme coming from anti-nuclear activists; but the best epidemiological studies predict about 4,000 eventual cancer deaths in the region.

Reactors produce a lot of radioactive elements, but the two we care most about are iodine-131 (131I) and cesium-137 (137Cs). 131I is very dangerous, but fortunately it also has a very short half life of 8 days. After 10 half lives, or about 80 days, it's basically gone and no longer a threat. Three Mile Island produced about 560 GBq (gigabecquerels) of 131I; Chernobyl produced about 3 million times as much, about 1760 PBq (petabecquerels).

Where does Fukushima fit between those two? At the high end, about 500 PBq. That's about a million times more than Three Mile Island, and about a third of Chernobyl. But things were done very differently. The area around Fukushima was very quickly evacuated and prophylactic iodine was distributed just as fast. Neither of these things were done at Chernobyl in a timely manner. The result was that in those first few weeks when the 131I presented a risk, lots of people near Chernobyl were exposed, and almost nobody was exposed in Fukushima.

Then there's the 137Cs, which is the long term threat about which bloggers and reporters expressed so much fear in the years following Fukushima. No significant amount was released at Three Mile Island because it was filtered out; but at Chernobyl, 85 PBq were scattered over the surrounding area. It has a half life of 30 years, which is a really long time; and it's why we're probably going to have to wait for a few more 30-year half lives to go by before the area around Chernobyl will be safe to move back in. At Fukushima, 137Cs was in the smoke from burning fuel and was in the cooling water sprayed into the damaged cores. A maximum of 15 PBq, just over a sixth as much as Chernobyl, was released into the environment. How much 137Cs does it take to produce 15 PBq of radiation?

About 4.7 kilograms. That's a lump a little smaller than a tennis ball.

1 gram of 137Cs = 3.214 TBq (terabecquerels of radiation)
A becquerel is the equivalent radiation of one neutron decaying per second.

Now, don't think that sounds like an absurdly small amount. 4.7 kilograms is a lot of atoms; if spread into an atomically thin pancake it could easily cover the entire world.

As with all dangerous radioactive elements, we've done a lot of study on the health effects of 137Cs. Although it has a radioactive half life of 30 years, it has a biological half life of 70 days. 70 days is the time it takes for animals like us to get half of it out of our system. That can be accelerated to just 30 days with treatment. From animal testing done in the 1970s, we know that 140 MBq per kilogram of body weight is a lethal dose. So with a little algebra, we know that Fukushima's 4.7 kg was enough 137Cs was enough to kill one and a half million people (assuming 80 kg people).

So here's the big "BUT..." — almost none of the will ever find its way into anyone's body. The Fukushima contamination is detectable all over the world, and it's probably in the bodies of everyone living on the planet. That's the nature of entropy. There is a lot of it in the water stored in tanks at the Daiichi power plant and in the soil in the evacuated zone, but the rest of it has been carried by water and atmospheric currents everywhere.

Our oceans contain one and a half billion cubic kilometers of water. Dilute Fukushima's 4.7 kilograms into that, and every cubic kilometer of water would contain less than one thousandth of a lethal dose. In other words, to die from Fukushima's radiation, you will need to drink one thousand cubic kilometers of seawater, and somehow manage to absorb every atom of 137Cs from it. But if you're looking only to eventually get cancer, then you might be able to do so on only a few hundred cubic kilometers of the Pacific.

But if you tried to do that, you would already die one million times over from just the primordial radioactive elements that exist naturally in our oceans; more than 15 zettabecquerels (a million petabecquerels) of naturally occurring potassium-40, rubidium-87, uranium-238, and so on.

This is the central thesis of science reporters who have been desperately trying to respond to scientifically illiterate fearmongerers printing headlines like "Your Days of Eating Pacific Ocean Fish Are Over" and "28 Signs That The West Coast Is Being Absolutely Fried With Nuclear Radiation From Fukushima". Our planet's entropy has, long ago, already rid itself of any credible threat from the Fukushima radiation, outside of the immediate evacuation zone. Fishing has long been suspended from Daiichi's vicinity, so there is no way that eating a legally caught fish can give you any significant Fukushima radiation.

Tip Skeptoid $2/mo $5/mo $10/mo One time

The Fukushima disaster will probably end up being the most expensive industrial accident and cleanup in history, but it has certainly not been among the most dangerous, thanks largely to Japan's prompt action. The newest World Health Organization assessment concludes:

...No discernible increase in health risks from the Fukushima event is expected outside Japan. With respect to Japan, this assessment estimates that the lifetime risk for some cancers may be somewhat elevated above baseline rates in certain age and sex groups that were in the areas most affected.

Clearly it wasn't good, but if you want to be able to develop proper response plans, you have to understand the correct facts about the situation. Absurdly exaggerated and sensationalized reports do not help anyone; rather they increase confusion, and decrease our ability to respond to such events appropriately.

Correction: An earlier version of this incorrectly stated that the control rods were not inserted at Fukushima due to the power failure following the tsunami. They were, in fact, automatically inserted after the earthquake, before the tsunami struck.

Brian Dunning

© 2014 Skeptoid Media Copyright information

References & Further Reading

Buesseler, K., Aoyama, M., Fukasawa, M. "Impacts of the Fukushima Nuclear Power Plants on Marine Radioactivity." Environmental Science and Technology. 1 Jan. 2011, Volume 45, Number 9931.

Hsu, J. "Fukushima's Radioactive Ocean Plume to Reach US Waters by 2014." Live Science. Tech Media Network, 30 Aug. 2013. Web. 9 Jan. 2014. <http://www.livescience.com/39340-fukushima-radioactive-plume-reach-us-2014.html>

NEA. Chernobyl: Assessment of Radiological and Health Impacts. Paris: Nuclear Energy Agency, 2002.

UMSHPS. "Radioactivity in Nature." The Health Physics Society. University of Michigan, 6 Feb. 2004. Web. 10 Jan. 2014. <http://www.umich.edu/~radinfo/introduction/natural.htm>

Unterweger, M., Hoppes, D., Schima, F. "New and Revised Half-Life Measurements Results." Nuclear Instruments and Methods in Physics. 1 Jan. 1992, Number A312: 349.

WHO. Health risk assessment from the nuclear accident after the 2011 Great East Japan earthquake and tsunami. Geneva: World Health Organization, 2013.

Reference this article:
Dunning, B. "Fukushima vs Chernobyl vs Three Mile Island." Skeptoid Podcast. Skeptoid Media, 14 Jan 2014. Web. 29 Aug 2015. <http://skeptoid.com/episodes/4397>


10 most recent comments | Show all 70 comments

Brian, I'm not sure if you are familiar with Thunderf00t on YouTube, but he is a well known atheist who has spent many years debunking creationism.

He also, lately, has been doing some videos on the uproar over Fukushima, and has been using real science (as usual) to debunk all these insane fears of radiation from the plant. Thunderf00t is an actual scientist with two PhD's - one in chemistry, I believe, and the other in physics. He has worked at at various nuclear facilities and cyclotrons, and he sure as heck knows his stuff.

I suggest that you check out his videos debunking all the conspiracy theories on radiation from Fukushima, going over the absolute misuse of information by those decrying how Fukushima is the worst disaster we've ever seen (and the outright lies of even mislabeling actual data maps). He also explains what radiation poisoning actually is, and takes conspiracy theorist videos to task, ripping them apart bit by bit.

Just go to his channel (Thunderf00t) on YouTube and you'll see a selection of videos he's recently posted about this whole affair. It's not only entertaining, but informative as well.

Nathaniel Harari, Haifa, Israel
February 24, 2014 8:31am

This article was articulate and provides an ease of mind through facts. I was pleased to see which direction it went and read all the comments. Though many corrections were made about the scientific aspects... in general, the big point was made clear: Fear mongering does nothing.

With that said, I offer my input. I live in Japan and was here during the earthquake. I have family and friends abroad who freaked out after the incident telling me to get out and even now give me links about radiation levels and how I am at risk being here. I can report that everything in Japan is back to normal and no one is living in fear. They are more concerned with the Olympics and celebrity gossip.

From what I see... The Japanese government has their flaws.. completely uninforming the public about the situation in Fukushima (total opposite of fear mongering, but complete ignorance... which is not good either) and making little progress in maintaining the situation. However, they haven't given up (especially knowing that the world is watching AND pointing the finger at them).

So living here, the one rule I make myself live by is to proceed with caution, but not live in fear. I won't go to a sushi buffet and drink tons of Fukushima sea water, but I will be picky about what I consume and read the news (listening to what's said with a grain of salt. Media makes its money on fear mongering. It's a business afterall).

Emi, Tokyo, Japan
March 6, 2014 4:42pm

Paul said: "Aggregating mutating every single cell of life that particle touches. It only takes one particle of plutonium to mutate, aggregating in the gonads of males. "

That is not how radioactivity works. Radioactive atoms are dangerous because when they decay, they release particles that can damage our cells-- aka ionizing radiation. However, until they decay, the atoms are completely harmless. After they decay they are similarly harmless.

It is only the decay process that produces any damage. Any radioactive atoms you ingest will either decay while they are in you, in which case they will add to your radiation dose, or they will pass through harmlessly, or remain in you after you die and then be reintroduced back into the environment from where they came.

It is true that the body can concentrate some forms of radioactivity (rather than getting rid of it as a wast product), and that this can be passed up the foodchain, but your implication that an atom of plutonium will ionize every atom it comes close to for 80 million years is outright false.

davea, Canada
March 19, 2014 11:32am

3 have happened in my life time

cumdumpster, uk
May 20, 2014 7:32am

I lived in Japan from 2009 until 2012.
I was actually in the area where the Earthquake hit strongest (Well, just north but still, it registered an 8.5 there) and I got my fair dosage of radiation (But I'm still only kind of glowing in the dark). However, I would like it to be noted that after the earthquake and tsunami, there was no major worry about the ocean water being too irradiated to swim in.

In fact, since I was one of the CBRN guys, I organized a training day where our unit would go out to the beach and do some training. On top of the days training, we ended it with a bit of a radiation sample reading. We took the water, tested it, and then showed it to the soldiers gathered around. Then, from one of the coolers, I pulled out some water bottles and tested the water in there. The result: No radiation above back round levels.

The point, I emphasized, was that as soldiers we have to believe what the facts are and how to check them, I then tied this into our daily workloads in which, as intel folk, we have to be able to interpret what the data we get says, as failure to do so can result in lives being lost or bad guys getting away.

Overall, I think the result had its' desired effect: Only 2 of the guys still believed that the Pacific ocean was doomed.

Meanwhile, everyone else got into the water and did some swimming fun to cool down after a hot training day.

Mission successful.

Amy, Misawa
June 14, 2014 11:30pm

This Video has been recently circulated..
Has anyone seen this?

Could anyone comment on its accuracy or scientific validity? ..
it raises some interesting points ...shown on the footage...

If it is indeed authentic,
it raises some completely contradictory scientific viewpoints to this Skeptoid article..

The people quoted on the Video appear to be officials and scientific atomic researches who quantifiably and strictly refute the stories that Fukashima is safe by any standard.

Can any one verify this video as authentic and accurate?

mystazsea, Melbourne Victoria
June 16, 2014 1:05am

I am a nobody, no college degree or any type of professional anything. I appreciate all of your comments. As a grandmother at home who likes to read, it is great to see a wide array of comments. Makes us THINK!

Carolyn3009, 78266
November 6, 2014 8:29am

BWR reactors aren't bad. GE just got NRC approval for a new BWR reactor, the ESBWR.
So I utterly disagree with the statement that PWR are safer than BWR.
There are dozens of reactors just like Fukushima, they are perfectly safe to operate as long as their emergency generators don't fail. That's why there are 3 emergency diesel generators plus grid connections (at least 4 electricity sources apart from the reactor's own main turbine). The problem was TEPCO murderous negligence.
Operating a nuclear reactor in a earthquake/tsunami/hurricane/typhoon areas shouldn't be permited to braindead operators.
Anyhow, both the latest PWR (AP1000) and BWR (ESBWR) incorporate passive safety features that allow them to shutdown safety and dissipate decay heat passively, so they don't depend on any electricity (from the main grid or from generators) to avoid both a Fukushima situation. And reactors designed in the 80s/90s still depend on emergency generators but are more robust.
The real area of concern is the structure of solid fuel for water cooled reactors when things go waywire. Water + Zyrconium + Heat produces lots of hydrogen gas, that's what caused the chemical explosions that destroyed the secondary containment in Chernobyl. Graphite is still used in many operational reactors in the world, and it isn't considered such a serious risk, as it takes oxygen to burn the graphite, gas cooled reactors don't have water or oxygen inside the secondary containment.

Marcelo Pacheco, Brazil
December 3, 2014 9:18pm

there are still millions of gallons of contaminated water stored on site, the reactor is still melting down. Do not underplay the magnitude of the disaster. There are plenty of ways to generate electricity other than fission reactors, that do not produce waste that is potentially harmful if not properly contained for thousands of years.
Yes, exaggeration is not good, because it gives the opportunity for articles like this to refute some claims, thereby implying that all is rosy when it is not.

Keith, south africa
January 1, 2015 2:31pm

Keith.. I'd happily buy a house there.. surf, fish and garden..

Mulga Gill, Sydney
June 29, 2015 12:50am

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