• 03/15/2011
    10:40 AM
    David Berlind
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Headlines About Japan's Nuclear Crisis Could Be Way Overblown

An MIT research scientist has released a provocative essay that explains in layman's terms why not to be worried about the problems at Japan's nuclear reactors. The original version cited inaccuracies in media reports, but falls short of blaming the media for being sensationalist.

Since this is not a column about information technology, I had serious doubts about publishing it on InformationWeek. But after sleeping on it last night, seeing this morning's headlines about another explosion at a Japanese nuclear reactor, and hearing people talking about it this morning at my local gym as though all of Japan was going to melt into the sea, I felt as though this was a story that was worth sharing with our readers. In rare cases, the importance of current events outweighs the efficacy of sticking strictly to IT-related stories.

Yesterday, via email, my father emailed me an essay by MIT research scientist Josef Oheman entitled "Why I'm not worried about Japan's nuclear reactors." According to Oheman's profile, "it was an email he sent to his family in Japan. When his cousin posted it on his blog, it went viral." I can understand why.

Even for people like me who understand very little about how nuclear reactors are designed, it does a good job of explaining how the nuclear reactors in question are designed to protect the environment from even the worst of meltdowns.

For example, it explains what a fuel rod is:

"The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 2800 °C. The fuel is manufactured in pellets (cylinders that are about 1 cm tall and 1 com in diameter). These pellets are then put into a long tube made of Zircaloy (an alloy of zirconium) with a failure temperature of 1200 °C (caused by the auto-catalytic oxidation of water), and sealed tight. This tube is called a fuel rod. . . . The solid fuel pellet (a ceramic oxide matrix) is the first barrier that retains many of the radioactive fission products produced by the fission process. The Zircaloy casing is the second barrier to release that separates the radioactive fuel from the rest of the reactor."

The essay goes on to describe another incredibly important safety characteristic of the Japanese reactor's design:

"The containment structure is a hermetically (air tight) sealed, very thick structure made of steel and concrete. This structure is designed, built, and tested for one single purpose: To contain, indefinitely, a complete core meltdown.To aid in this purpose, a large, thick concrete structure is poured around the containment structure and is referred to as the secondary containment."

It talks about how the explosions damaged the reactor building, which serves no purpose in the containment of radioactive material release, and how the nuclear crisis at Chernobyl is not projectable to the Japanese situation due to significant differences in design. Then, it goes on to describe the nature of the explosions that have so many people worried:

"In order to maintain the pressure of the system at a manageable level, steam (and other gases present in the reactor) have to be released from time to time. This process is important during an accident so the pressure does not exceed what the components can handle, so the reactor pressure vessel and the containment structure are designed with several pressure relief valves. So to protect the integrity of the vessel and containment, the operators started venting steam from time to time to control the pressure....Some of these gases are radioactive fission products, but they exist in small quantities. Therefore, when the operators started venting the system, some radioactive gases were released to the environment in a controlled manner (i.e., in small quantities through filters and scrubbers). While some of these gases are radioactive, they did not pose a significant risk to public safety to even the workers on site....

...if there is enough hydrogen gas, it will react rapidly, producing an explosion. At some point during the venting process enough hydrogen gas built up inside the containment (there is no air in the containment), so when it was vented to the air an explosion occurred. The explosion took place outside of the containment, but inside and around the reactor building (which has no safety function). Note that a subsequent and similar explosion occurred at the Unit 3 reactor. This explosion destroyed the top and some of the sides of the reactor building, but did not damage the containment structure or the pressure vessel. While this was not an anticipated event, it happened outside the containment and did not pose a risk to the plant's safety structures."

In consuming this essay, there are a couple of points worth making. They don't suggest that you take the essay with a grain of salt. But the background is helpful in determining the reliability of the information.

First, Josef Oheman is not a nuclear scientist. Second, there was an original version of the essay (the one my father sent to me) that included passages that have since been edited out of the official version that's now published online. For example, the following "reassuring" text was removed:

"A large and thick concrete basin is cast under the pressure vessel (the second containment), which is filled with graphite, all inside the third containment. This is the so-called 'core catcher'. If the core melts and the pressure vessel bursts (and eventually melts), it will catch the molten fuel and everything else."

The original version is also the version that talked about inaccuracies in the media:

"I have been reading every news release on the incident since the earthquake. There has not been one single (!) report that was accurate and free of errors (and part of that problem is also a weakness in the Japanese crisis communication). By "not free of errors" I do not refer to tendentious anti-nuclear journalism -- that is quite normal these days. By "not free of errors" I mean blatant errors regarding physics and natural law, as well as gross misinterpretation of facts, due to an obvious lack of fundamental and basic understanding of the way nuclear reactors are build and operated."

Even though these and other comforting passages have been deleted, the official edited version is far more reassuring than any news report or headline that I have seen and is now published and maintained with updates at MIT's NSE Nuclear Information Hubwhere, according to Oheman's profile, "The original blog will be ... managed by a team of experts from MIT's Department of Nuclear Science and Engineering."

Looking at the portion of the text that has so far survived that department's scrutiny, I personally feel a lot better about what's happening at the Japanese nuclear reactors. For the sake of Japan and the world, I pray that Oheman is right. I also try to reconcile what I've learned from Oheman's essay with the eye-popping headlines that continue to dominate most of the main news sites. Take it from someone who is in the media: they're written to get clicks (just like the headline to this column).


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