Caveat: It seems I have to put a warning sign on this post. I am not a nuclear physicist and the opinions on this post are personal and are not professional, scientific advice on radiation or its effects.
I’ve had a crash course in nuclear physics this week. I took basic Physics in university, but my major was History, so I never really got into it. This interconnected world sure makes it easy to learn informally though.
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 core is then placed in the pressure vessel. The pressure vessel is a thick steel vessel that operates at a pressure of about 7 MPa (~1000 psi), and is designed to withstand the high pressures that may occur during an accident. The pressure vessel is the third barrier to radioactive material release.
The entire primary loop of the nuclear reactor – the pressure vessel, pipes, and pumps that contain the coolant (water) – are housed in the containment structure. This structure is the fourth barrier to radioactive material release. 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.
Both the main containment structure and the secondary containment structure are housed in the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosions, but more to that later).
Then I read today on the MIT site that, “Radiation levels on the edge of the plant compound briefly spiked at 8217 microsieverts per hour but later fell to about a third that.” What’s a microsievert, I asked myself, and how dangerous are 8217 of them? I was able to find out via Wikipedia that:
1 Sv = 1000 mSv (millisieverts) = 1,000,000 µSv (microsieverts) = 100 rem = 100,000 mrem (millirem)
And I further read that at 250,000 µSv ”Some people feel nausea” and at 1,000,000 µSv there is “Mild to severe nausea”. Makes 8,217 µSv look pretty small to me.
The mainstream media reports tell a different story. Here’s one from the Canadian Broadcasting Corporation:
Most of the attention in the past three days has been focused on Daiichi units 1 and 3. A complete meltdown — the melting of the radioactive core — could release radioactive contaminants into the environment and pose major, widespread health risks.
There is no mention of radiation levels, or what would happen in the event of a core meltdown [containment], in this story and in many others by the CBC and other mainstream media/entertainment sources.
There are some characteristics of a nuclear fission reactor that will be common to every nuclear fission reactor. They will always have to contend with decay heat. They will always have to produce heat at high temperatures to generate electricity. But they do not have to use coolant fluids like water that must operate at high pressures in order to achieve high temperatures. Other fluids like fluoride salts can operate at high temperatures yet at the same pressures as the outside. Fluoride salts are impervious to radiation damage, unlike water, and don’t evolve hydrogen gas which can lead to an explosion. Solid nuclear fuel like that used at Fukushima-Daiichi can melt and release radioactive materials if not cooled consistently during shutdown. Fluoride salts can carry fuel in chemically-stable forms that can be passively cooled without pumps driven by emergency power generation. There are solutions to the extreme situation that was encountered at Fukushima-Daiichi, and it may be in our best interest to pursue them.
This is why it’s so important to be a self-directed learner. Who stands to benefit by the stuff that’s being Pushed to you? Advertisers? Whether it’s news or education, we have the networks that can help us figure things out. It just takes a little effort.
It’s not just the media, either. This weekend I came across an article in The Atlantic, Lies, Damn Lies and Medical Science that showed that “as much as 90 percent of the published medical information that doctors rely on is flawed”. We need to think for ourselves.
Update 16 March: The CSMonitor (almost mainstream media!) is providing some good in-depth reporting:
Good coverage by The Guardian – Japan Nuclear Crisis Live Updates
I must say that the mainstream press are stepping up on this.
18 March: From a science journalist: Nuclear power won’t kill you