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Why Fukushima isn’t Like Cernobil

Despite media hype about the radiation dangers, the Fukushima nuclear crisis won't end like

Chernobyl, Alexander Sich tells The Diplomat.

By The Diplomat

Is the kind of massive radiation release that occurred with Chernobyl possible at the Fukushima

plant?

 No, it can’t have that kind of massive release. It simply can’t do that. The question is to what extent the

zirconium alloy, which clads the fuel pellets, is damaged in the core, and how much of the fuel hasfailed. And I don’t necessarily mean melted , I mean failed . There’s been an ambiguous use of the word

‘melting’ applied to the core. But when people talk about meltdown, they should be very specific about

what they mean by the word.

At Fukushima, there are four primary barriers to releases: the fuel zircalloy cladding, a pressure vessel,an inner containment structure, and a confinement building. To a large extent, the core material seems

to be contained. Apart from, of course—and this is where the speculation runs wild—there’s the

question of the source of the radiation they’re detecting in certain areas where water has accumulated.

Indications today are that it isn’t the cores. They’ve been dumping or spraying tremendous amounts of 

water onto and into the damaged buildings, so surely someone is considering this water as a possiblesource.

But until they go in and see, we have little more than speculation to go on, because they don’t know to

what extent—if any—the cores are damaged, and they don’t know to what extent the pressure vesselsare damaged, although that’s unlikely. They also don’t know to what extent the pipes are damaged, and

they don’t know to what extent the lower portion of the containment building is damaged. So, on the

one hand, I can’t speculate on what is going on inside. But even so, and given what nuclear engineersknow in terms of the plant layout, it’s just not true that it’s a Chernobyl situation.

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So, you’d say it was unfair to draw parallels between Fukushima and Chernobyl?

They are very, very different and it’s very unfair to draw that parallel. There are two parts to this. One

is the myths that currently surround Chernobyl. The other is the sheer difference between the incidents

 —the causes of the accidents and the structural, engineering and physics differences.

For a start, there are three or four primary and important differences between the two reactor designs.The first is the difference between the Western Light Water Reactors—pressurized water reactors and

(like those at Fukushima) boiling water reactors—and the plant at Chernobyl.

Western Light Water Reactors are water cooled and water moderated. The first one is simple—water is

used to cool the fuel, to take away the heat, to eventually create steam and then after that makeelectricity. It’s the water moderation that’s the very important difference. What moderation means is

that the water is used to slow down neutrons in the core and make them accessible for the reaction to

take place. In the Chernobyl type reactor, water is a coolant, but it’s not a moderator—the moderator isgraphite, and that points to one important design and structural difference.

In the Light Water Reactor core, apart from the fuel itself, it’s virtually all metal. You have the fuel

contained in a special kind of zirconium alloy, there’s the stainless steel vessel, and the super structure

is metal. In the Boiling Water Reactor (BWR) that you find at Fukushima, you have a reactor pressure

vessel that’s approximately six inches thick steel—it’s basically a big kettle that contains the core. Inthe Chernobyl reactor, there was no pressure vessel. So right there, there are two very big differences— 

the BWR is contained in a very robust pressure vessel, the Chernobyl reactor was not. The BWR 

reactor is a singular metallic vessel, while the Chernobyl reactor is approximately 1700 individual pressure tubes piercing about 2,000 tonnes of graphite. Western LWRs contain essentially no graphite.

Those are very big differences.

Photo Credit: Flickr / Daveeza

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The third very big difference is that all Light Water Reactors have some sort of containment structure

or containment building. The Chernobyl type reactors, of which there are 11 still operating, have nocontainment building. The final difference between them is basically an operational one. The BWR iscontrolled by both control rods and coolant jets that form a ring around the reactor—inside the reactor 

 pressure vessel but around the core—and by basically turning up or slowing down the speed of those

 pressure pumps you can adjust the power. It’s a very nice way of doing it. And also the size of theBWR core is about 2.5 metres in diameter and about 3.7 metres in height. The Chernobyl reactor, in

contrast, is 11.8 metres in diameter and 7 metres in height. It’s a very big reactor, and that’s what I

mean by the operational differences.The Chernobyl reactor is a ‘decoupled’ core, which means one side of the core doesn’t always ‘know’

what the other side is doing neutronically. What that means is that the reactor operators need to keep a

very close eye on what’s going on in the Chernobyl type reactors. That isn’t the case for Western

reactors. In those, one side of the core ‘knows’ fairly well what the other side is doing and it naturallyadjusts.

This leads to the final point. In a Western Light Water Reactor, there’s something called a negative

feedback principle at work. If a Light Water Reactor heats up for whatever reason, the reaction actually

slows down—it’s worse for the reaction if the reactor gets too hot. In the Chernobyl reactor, it worksthe opposite way in certain power ranges. In other words, the hotter the reactor gets, the more you boil

water. The more you boil water, the more you introduce steam voids, the more you introduce steam

voids, the faster the reaction goes. This has been largely addressed since the Chernobyl accident by theRussians. Still, it doesn’t take a rocket scientist to understand that you don’t want such a situation

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 because of the positive feedback. I’m not saying it happens all the time, but in certain power ranges it’s

true. This isn’t possible in a Light Water Reactor.

So all those things together are a rough summary of how different they are in terms of structure. That

leads to the second thing I mentioned, which are the causes of the accidents.

At Fukushima, the earthquake didn’t cause the accident, but caused the reactors to automaticallyshutdown. The systems worked—they went subcritical. The problem was that the ensuing tsunami

devastated some equipment on the outside of the plant that was supposed to ensure continued core

cooling. Unfortunately, that equipment got damaged and that’s why in the past week the Japanese have been pulling power lines to the reactors and restarting those things.

At Chernobyl, what caused the accident was 1) what I just mentioned before, the kind of inherent flaws

in the reactor design and 2) external production pressures to conduct what was ironically a safety

experiment. The accident occurred on April 26, 1986, just a few days before May Day, which in theformer Soviet Union was a very big national holiday. And they were being pressured to produce as

much electricity as possible so they could get their bonuses, and also this safety experiment so they

could get their bonuses. In fact, the dispatcher in Kiev, about a day before the accident, ordered the

reactor crew not to go down on power as they needed another nine hours of production.

So there was this external stuff going on. And the final thing that caused the accident was the errors onthe part of the operators—they intentionally overrode safety precautions, safety barriers and interlocks.

They did that because they were pressured to do this experiment. All this means that the two accidents

are vastly different. At Chernobyl you had a massive, massive release of radioactivity. While we stilldon’t have the numbers for Fukushima, I would compare it maybe to a matchstick and a stick of 

dynamite. It’s a crude analogy, but it gives you some insight.You mentioned some myths surrounding Chernobyl. How have these impacted the view of events

surrounding Fukushima?

Unfortunately, certain interested parties have been employing sensationalist rhetoric, inaccuracies, and

outright hoaxes regarding Fukushima. I refuse to dignify with comments SMS hoaxes in the

Philippines as well as a map, purportedly from Australia, predicting lethal dose rates affecting thewestern coast of the United States. Nonsense—that’s all these are.

But then there’s Congressman Ed Markey of Massachusetts who warned of ‘another Chernobyl’ and

 predicted ‘the same thing could happen here (the United States),’ and then proceeded to call for an

immediate suspension of licensing procedures for a new generation safer reactor design. I find thatrepugnant.

Michio Kaku, a theoretical physicist from the City College of New York who studies string theory, is

also out of his depth when it comes to nuclear reactors. He’s not a nuclear engineer, and yet that hasn’t

stopped him making borderline hysterical statements during interviews. Kaku claimed, for example,that a ‘China Syndrome’ was possible, that the ‘(Chernobyl) vessel and roof blew out

simultaneously’—factually incorrect on both counts: Chernobyl-type RBMK reactors have no reactor 

 pressure vessel.

Also, without providing a shred of evidence, Kaku asserted ‘We’re still seeing people dying of that(Chernobyl) reactor accident.’ He’s no doctor nor health physicist. Kaku also claimed the situation ‘had

gone from bad to worse…the reactor is in free fall, and you have three simultaneous meltdowns, and a

raging spent fuel pond that could explode.’ Most troubling was Kaku’s careless recommendation, ‘If Ihad the ear of the Japanese prime minister I would recommend the Chernobyl option (dumping

materials from helicopters).’ In fact, dropping tons of materials from helicopters high in the air onto

debris and inner reactor building structures might well compromise the integrity of structures designed

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to contain releases in the first place.

Partly what drove this view is the well-known video footage of helicopters flying over Chernobyl

dropping material on the core. But the fact is that they never hit the core. What they were bombing was

something that was burning off to the side of the reactor. The second myth about Chernobyl is that thesarcophagus—what they built on top of the reactor—is some kind of monolithic concrete structure that

has recently cracked and is releasing radiation. This isn’t true. It’s not a monolithic structure; it was

more like a steel tent. This myth about concrete is one of the most pernicious ones about Chernobyl.But I worked for a team on site that is building a new sarcophagus so that the clean-up anddecommissioning efforts of the Soviet-built sarcophagus can take place with a much-reduced risk of 

spreading contamination. They are taking the old one down because it was built on debris, and so no

one knows what the actual robustness of that structure.

What have you made of the media coverage of the situation in Japan?

I think the press needs to be very careful about which talking heads they choose to comment on the

accident. Unfortunately, the press doesn’t usually understand the big difference between a theoretical

 physicist and a nuclear engineer. But the difference is roughly like comparing a general practitioner to a brain surgeon—a brain surgeon needs to know the brain inside out, while a general practitioner can

only make general comments about the brain. So, theoretical physicists can make general comments,

 but can hardly comment on the specifics of important nuclear reactor design details. I would thereforeurge the media to identify BWR specialists who understand the Three Mile Island incident inside out,

and who understand very well the Chernobyl accident in Ukraine and the Windscale accident in Britain

so that sober and serious and correct information can be provided to the public.

The second thing I would urge is some caution and not to criticize the Japanese. I’m not saying themedia itself is doing this, but it certainly tends to permit ‘air time’ a kind of sensationalist criticism of 

the Japanese, and I’m not sure they deserve it. The Japanese are doing the best they can in a very

difficult situation. I’m not saying they are spot-on perfect with everything they do. But, I wouldn’t

criticize. I would try to help them, I would bring in specialists, I would do what is possible, and of course ask the Japanese to provide as much information—including verifiable numbers—as they can.

I’ve been keeping track of the media, and in the early days, up to a week after the accident,sensationalist headlines abounded. But then you would look through the actual articles trying to look 

for numbers, and few if any were provided. For example, you find today’s story about how ‘levels of iodine have been detected in Massachusetts’. But you have to provide a number—provide a

comparison before saying something. Radioactive iodine and other contaminants were released in far 

greater quantities in Windscale in England, for example, or Chernobyl, and certainly by theatmospheric testing of nuclear weapons.

If you’re talking trace amounts, then you’re talking trace amounts. After all, our bodies are radioactive.

You get a dose of radioactivity when you sleep next to your spouse. Are we talking about those kinds of 

levels or something else? So I would like to see some circumspection. Of course, never stop askingquestions. But ask for numbers.

 Alexander Sich is an associate professor of physics at Franciscan University of Steubenville in Ohio.Sich was the first American researcher to investigate the Chernobyl reactor meltdown on site. The

views expressed are his own.

 

Chernobyl, Fukushima Nuclear Plant, Tohoku Earthquake, Tokyo, Tsunami 

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• Victor

April 3, 2011 at 4:21 am

I say is too soon to draw rational conclusions. Let the japanese and other nuclear engineers do

the work that urgently need to be done. Once things are under control let us conduct worldhearings and an independente investigation about what happened. Then we will be able to make

ourinds up. In the mean time take much of what the media healines as tragedy-basedinfotainment, not information. Let us not forget that US style media have succeeded into

 paralizing the US as an industrial country where they do not wanto to do any industrial

innivation for fear of lawsuits, this is why even Apple will be unable to manufacture the Iphonein the US; the technology is simply not available in the US.

Victor ben Abraham

Reply 

• Nasu

April 1, 2011 at 8:37 pm

I live in Fukushima. Regardless of what all the experts say, the earthquake and tsunami have

caused massive damage to people’s lives, homes, schools, roads, etc. With all the information

from the Japanese media (TV and radio), and the news from sources outside Japan, it’s verydifficult to paint an accurate picture of what’s going on. I live within 60km to 70km of the

reactors, food and water is questionable, but said to be safe. Hearing the figures about radiation

in food and water here is mentally exhausting. What information is accurate? Some of my

Japanese friends question whether the government is not telling the whole truth, while othersare trust the government completely. What can be said to be 100% accurate is, the Japanese

governement is doing there best to get the situation under control. This earthquake and tsunami

has changed Fukushima prefecture forever. It will never be the same again.

Reply 

• The Rad Rider

April 2, 2011 at 5:28 am

Dear Nasu :

My best wishes are with you and your people but my wishes don’t change things.

If they did, this would never have occurred. The best that I can hope for at this time is

that we don’t let something like this happen again.

Take Care

Reply 

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