AAAAAAAAHHHH! Turn it off! Turn it off! Turn it off!
Disclosure: I am not a nuclear physicist but I do have the equivalent of a MS degree in nuclear engineering from a classified (as in secret) U.S. nuclear laboratory.
A week ago I was sitting here writing my blog in the aftermath of the Japanese devastation: Billions of dollars of damage, at least 10,000 fatalities, and parents finding their deceased children or elderly parents in smashed vehicles and destroyed buildings.
What is the media absolutely obsessed with? Why of course, something they know absolutely nothing about. I have never seen such an onslaught of talking heads blathering about things for which they have no expertise. Zero. A woman on TV, a “nuclear industry journalist” talks about “nuclear fire”. What the hell is that? There is no such thing. A common fire is carbon and/or hydrogen getting together with oxygen to form the diabolical carbon dioxide and water vapor, and heat. This DOES NOT HAPPEN in nuclear anything. Note some pure metals burn, as in colorful fireworks, but a damaged reactor core is not fireworks.
In another broadcast, one talking head called the Fukushima incident a national security issue, to the United States. You have got to be kidding me. I’ll tell you what a threat to national security is: ethanol. That’s right. Nothing will turn out rebellion like food shortages, which sparked the Egyptian chaos.
Other sensationalizing includes talking about the nuclear danger while showing pictures of natural gas explosions at an oil refinery. Nice. One hundred percent, no connection and no comparison.
How many people have died as a result of the boogeyman, direct nuclear radiation at Fukushima? Zero that I am aware of. Nobody died from Three Mile Island either. Even Chernobyl, the most massive nuclear power plant disaster ever only caused about 50 deaths per The Guardian (UK) and Time magazine. More on Chernobyl later.
Even if you are an intelligent but nuclear-ignorant reader, you have to ask yourself, what are they talking about? For instance, the Wall Street Journal reports that at one point radiation levels at the gate of the nuclear complex in Fukushima was 11,000 microsieverts per hour equivalent to what a person receives in 11 years. What?! They are comparing a rate (in units per time), to units. It’s like saying I drove 90 miles per hour to work today, the equivalent of what I would drive in a week. What?
It goes on to say the Nuclear Regulatory Commission’s dose limit is 10,000 microsieverts “per nuclear event”. What is that? The reader doesn’t know but it sounds scary and sells. The average person gets 6,200 microsieverts per year from background junk – by just being alive and on planet earth. People working with radiation on the job are limited to 50,000 per year. Add all that up and tell me what you get. It’s all hype.
Although I have not heard because the press knows nothing, it sounds as though the Fukushima nukes are boiling water reactors. Although I believe most nukes in the U.S. are not boiling water reactors, the Fukushima and U.S. reactors are thermal nuclear. A thermal nuclear reactor simply means the fuel Uranium isotope U-235 will absorb a “thermal” neutron and become unstable. When it becomes unstable, it fissions, splitting into two daughter products; an array of atoms from all over the periodic table. With daughter products come other radiation, namely alpha and beta particles, gamma rays, neutrons, and of course, a lot of heat (E=mc^2 stuff).
A thermal neutron is one that has given up most of its kinetic energy after it was emitted from a fission or puked out of an unstable daughter atom of some sort. They lose energy by bouncing off water molecules like billiard balls. The water serves as the moderator, as in, lessening the intensity of something – and it is also the coolant that takes heat from the reactor to generate steam. Once neutrons are released, they are either absorbed by the fuel to make more fissions, leak out of the reactor core, or get absorbed by control rods or “poisons”.
A nuclear reactor is a highly stable system. If it weren’t, it would be a bomb. Therefore, a reactor WILL NOT EXPLODE!!!! So what were the explosions at Fukushima then? I’ll get to that.
Nearly all neutrons released are instantaneously released upon fission of U-235. These are called prompt neutrons. A tiny fraction are delayed neutrons that have an average of seven seconds (roughly) delay between a fission and their release. Without the delayed neutrons, a reactor would be unstable, it would go prompt supercritical – boom. The delay provides just the right balance so the system can have feedback and self correct. How does it do this? Fluctuations in water density. When heat transfer is reduced (less turbine power and electricity production), the water moderator/coolant gets hotter and less dense. Fewer water molecules in the reactor mean fewer collisions for neutrons. More of them leak out of the reactor. Fewer are absorbed by U-235 to fission and produce heat. The coolant cools, gets a bit denser and the fuel starts to give off more energy again. Beautiful.
What about those explosions at Fukushima? Spent fuel is not like a half burned log. It essentially looks the same as fresh fuel but its composition changes slightly after all the U-235 fissions occur. But it is radioactive, which simply means daughter products are still puking out alpha and beta particles, neutrons, gammas, and relatively low levels of heat. At Fukushima, spent fuel is kept in a pool above the reactors apparently. Why? No idea. But the radiation ionizes the water that keeps it cool and shields radiation. Ionization of water produces hydrogen, which is explosive, and takes practically nothing to set off. This caused the explosions and release of low level radiation to the atmosphere.
How about the fuel? Both the spent fuel and the fuel still in the reactors need to be cooled because of the decay heat. Otherwise, they will melt, sort of like a pillar of wax. The fuel will NOT explode. Remember, to maintain a chain reaction, to remain critical, requires water to moderate neutrons. If there is no water, the neutrons all get away BUT there is also no cooling. If there is no water and there is not enough air cooling, fuel damage (distortion) may occur, but I don’t know if it would melt. It would have to exceed 3,300F – pretty hot – ~600F hotter than the melting point of steel. Regardless, it isn’t going to melt through to the core of the earth like Doctor Evil’s subterranean nuclear-tipped Vulcan drill, and explode.
How about the radiation? Radiation is given off by physical matter. It isn’t a mysterious uncontrollable cloud of cancer. Direct radiation from the nuclear plant falls off with the cube of distance from it. For example, to reduce exposure in half, one would have to move from 1.0 mile to only about 1.25 miles away. At 2 miles you would only get about 12% of the radiation compared to one mile.
This radiation hype reminds me of the lead-tainted toys from China. While there is no excuse for having lead contaminating toys, it is harmless, unless you grind it up and mix it in Johnnie’s oatmeal or he snorts it like cocaine. Similarly, a person almost has to come in physical contact with or ingest radioactive material. Radon, which Iowa has more of than any other state, has to be inhaled and by chance the radon has to release a harmful alpha particle while it’s in your lungs. The radon isn’t harmful. The particles it spits off are and they have to be spit out while in your lungs.
Practically anything will stop alphas and betas; skin for example will. Alpha and beta damage typically requires ingestion. Neutrons are more penetrating but water will knock these down quickly, which is why water is used outside the reactor to shield neutrons from getting away. Gammas can have a lot of energy and may take thick lead or concrete to stop – hence lead shielding around reactors. Damage can occur just by being in close proximity to gammas. Just don’t carry things like Cobalt 60 in your pockets. So like the powdered lead, for the general public danger from Fukushima is really only going to come from radioactive air-borne contamination. How do things get air borne? An explosion is a good way but explosions occurring at these plants are due to hydrogen as discussed above. It is nothing like a bomb where all daughter products are released and air borne. Radioactive daughter products are likely well contained in the fuel at Fukushima. Daughter products, many of which are gaseous, would first need to blister and rupture the fuel pellets and THEN get out of the fuel’s cladding. However, blisters are not going to grow when the reactor is shut down as these were.
Get a grip. The chance of adverse health effects from nuclear power plants is less than being attacked by terrorists, which is much lower than dying in a plane crash, which is much lower than being struck by lightening, which is much, much lower than dying in a car crash. If you are concerned about nuclear plant health effects, you ought to also be on the lookout for man-eating chickadees, and certainly bananas, which are radioactive by nature.
Lastly, the only time “Chernobyl” should be used in reference to this Fukushima incident is, “Fukushima bears no resemblance to Chernobyl, whatsoever.” Chernobyl was a carbon, not water, moderated reactor. When carbon gets too hot, unlike water, it ignites – go boom. Chernobyl had no containment vessel either. The reactor actually blew to bits.
written by Jeffrey L. Ihnen, P.E., LEED AP