In a significant development, which drastically changes the terrain of the renewed nuclear power and waste isolation the Department of Energy has withdrawn its license application with the Nuclear Regulatory Commission. This effectively ends the project and begs the question: what, where, when, who and most importantly, why now?
Let's remind ourselves of the basics of how we generate electrical power from uranium. The basic principle is that since uranium decays radioactively -- it's "hot" -- the energy given off by the components of the decaying nuclei can be used to heat water into steam. That steam is then used to drive a turbine, which is connected to a electrical generator.
So let's look at the life cycle of a chunk of uranium. In the previous post, February 19, 2010, we discussed how uranium is isolated from dirt and rock in naturally occurring deposits called uraninite or, commonly, pitchblende. After processing the ore to natural uranium, chemical and/or mechanical processing is needed to purify or enrich the material to isolate the desirable component 235U. (You might recall the role of warehouse-sized fields of centrifuges.) Keep in mind that, when determining the economic feasibility of nuclear power, we need to take into account the cost of all the stages of production, consumption, and isolation of the radioactive material.
Now, once we've isolated the 235U (read "U-235" or "235-U," either way) to low-enriched (anywhere from 4% to 20%) we can think about putting this "hot," radioactive material into a reactor and use it to make electricity to run our mechanized world. The form in which the enriched uranium goes in to the reactor is as nuclear fuel, often shaped in cylinders (which themselves are comprised of fuel pellets) commonly referred to as rods. The rods are placed into the reactor core, in various configurations depending on the reactor, and water under pressure is circulated throughout the chamber, called the reactor core, which removes the heat of the nuclear reaction. There's no mixing of the nuclear fuel with water.
After a period of time, typically on the order of weeks or months, the nuclear fuel is "spent" in the process of the decay of the 235 nuclei which comprise the material. (We'll talk about the quantum mechanics of the process of radioactive decay in the next entry. Promise.) Spent nuclear fuel is also known as waste. Waste is an interesting concept that humans have come up with stuff that we've stopped thinking about. But if you stop thinking about this waste, you're going to get into some trouble.
Dealing with the spent nuclear fuel is -- by far -- the most costly part of generating electricity from radioactive materials. You can't throw it away. It must be isolated. This is where the Yucca Mountain waste repository project came into play. The problem is that the spent nuclear fuel is still hot, literally. While the fuel is "spent" as far as the reactor engineer is concerned (because it has become contaminated with the products of the radioactive element and its activity has fallen below design specification) it's ain't so for us. This stuff is nasty. Still radioactive and toxic to boot. And it remains active for a long time.
So the question is what do you do with it so that it's isolated from flora and fauna (include people in this category, why not?) and doesn't do all the bad things that radiation poisoning can do. (Another topic for a future entry!)
There have been a lot of ideas on how to isolate spent nuclear fuel. All of them are ludicrous. Most of them are economically unfeasible. "Send it to 'outer' space."Or 'the moon.' Forget about giving it to NASA. It's too expensive and what if the Challenger had been loaded up with this junk?
The only idea that's considered feasible economically is burial. Stick it into the ground in a deep hole. And hope. I say "considered" feasible because it's not -- really.
The first problem is the cost of building, storing, maintaining, monitoring, and preventing accidental release of the spent material. If anything goes wrong on a large scale -- water contamination, fire, earthquake, etc. -- we're up you-know-where without a you-know-what. You can't easily "handle" this stuff, after all.
Yucca Mountain was selected by Congress[!!], not by scientific process of elimination, but for overtly political considerations. They said "it's dry enough." Turns out it's not. If water gets near this stuff, usually held in metal barrels the show is over.
More later about the details of the actual storage of spent nuclear fuel.
Showing posts with label uranium. Show all posts
Showing posts with label uranium. Show all posts
Friday, March 12, 2010
Saturday, February 20, 2010
Focus on Iran intensifies
The report released 2010/02/18 by the International Atomic Energy Agency (IAEA) Board of Governors, Implementation of the NPT Safeguards Agreement and relevant provisions of Security Council resolutions 1737 (2006), 1747 (2007), 1803 (2008) and 1835 (2008) in the Islamic Republic of Iran has caused a stir in the media with articles in the New York Times, Washington Post and other papers of record.
The highly anticipated report of the new IAEA director general, Yukiya Amano who took office December 1, 2009 indicates that he'll be taking a hard-line on Iran. This is a strong contrast to the previous IAEA director, Mohamed ElBaradei the Nobel peace prize winner who presided over the agency for twelve years. ElBaradei was viewed unfavorably by the U.S. government, in general. Amano is viewed in a much more positive light, as the reports today in the NYT, WP, and others indicate.
Enough personnel background -- let's get to the nuclear issues. Incidentally, the purpose of this blog is, generally, to assess claims made in the press and by government and other officials regarding nuclear issues: weapons, energy, waste isolation, etc. And whether these claims are true and of possible concern. We take as tenet the observation that nuclear weapons are, from the perspective of science, a weapon without an application. And the observation that politics, at least in these United States of America, is the expression of aggregated perception -- that is, basically, the opposite of science. (I'll take care to develop these two points as the blog evolves.)
Focusing on the NYT article by D. Sanger and W. Broad, the first point of scientific note is the fact that the IAEA report confirms that the Iranians have enriched "small quantities" of uranium to 20%. Of equal import is the observation by Sanger/Broad that the report "makes no assessment of how close it might be to producing a nuclear weapon."
By way of background, let's tackle the question of "enrichment" first. In summary, enrichment is the process of taking uranium the way it's found in nature and processing it into a more pure form. Uranium is a naturally occurring element, found in rock deposits. The concentration of uranium in the ground is tiny so isolating this element takes a lot of dirt and rock and work. The typical way of mining it is open-pit (devastating the natural environment) and the three countries which are the world's largest producers are Canada, Australia, and Kazakhstan. The total world output of uranium is about 100 million pounds per year.
When uranium ore comes out of the ground the uranium is bound up with oxygen (as U3O8, "triuranium octoxide" an "oxide of uranium") and is released by chemical leaching. The resulting powder is brown or black (not yellow, usually) -- this is the "yellowcake" of note in the recent story of Joe Wilson's trip to Nigeria at the behest of the Bush Administration.
Uranium oxide still needs to be processed further to yield more pure forms of the metallic element, 235U the only form which is usable for generating power or making bombs. The reason for this is explained by quantum mechanics and we'll have occasion later to talk about it. The difficulty in isolating or "enriching" the 235U is the same difficulty we had in getting the yellowcake out of the ore that came out of the ground -- scarcity. When we have the yellowcake, the uranium in this powder comes in two varieties. The variety we want, the 235U, constitutes only about 1% of the total amount of uranium. And this uranium is bound up in the molecule U3O8.
The way that the uranium is purified or enriched is a complicated chemical and mechanical separation process which typically uses a large number of large centrifuges. By 'large number' we mean warehouse-sized areas which cover acres. In other words, enrichment facilities are not easy to hide. We'll discuss the details of enrichment in a later entry. (Promises, promises!)
Enriched uranium is classified according to its purity. There are several classes of grading but, basically, there's "low-enriched" and "highly enriched" grades. Low-enriched is less than 20%, sometimes considerably less. Highly enriched is above 20%.
Weapons need 85% and higher enrichment -- a very pure, metallic form of something that started as being bound up in dirt and rocks. The low-enriched form, typically below 20%, what the Iranians have, is only good for generating power.
Returning to the observations made by Sanger/Broad in their NYT article, we see that it's likely that they correctly assess the amount and purity of the uranium that the Iranians possess since these figures square with several sources -- the IAEA, the CIA, and other western government intelligence estimates.
A little more interesting, perhaps, is their observation that the report doesn't say how far the Iranians are in their weapons development program. The short answer is: "many years" -- at minimum, 5 years. At most, 10. (These figures assume that the Iranians would expend huge amounts of capital developing the large facilities we know they don't now have.) It's interesting that the report "makes no assessment." This is a choice, of course, on the part of Amano's IAEA.
My suspicion is that giving the realistic estimate (more than my 5-10 years) takes the punch out of this report. It suggests that we might anticipate a lack of forthright and honest dealing on the part of the new Director.
The highly anticipated report of the new IAEA director general, Yukiya Amano who took office December 1, 2009 indicates that he'll be taking a hard-line on Iran. This is a strong contrast to the previous IAEA director, Mohamed ElBaradei the Nobel peace prize winner who presided over the agency for twelve years. ElBaradei was viewed unfavorably by the U.S. government, in general. Amano is viewed in a much more positive light, as the reports today in the NYT, WP, and others indicate.
Enough personnel background -- let's get to the nuclear issues. Incidentally, the purpose of this blog is, generally, to assess claims made in the press and by government and other officials regarding nuclear issues: weapons, energy, waste isolation, etc. And whether these claims are true and of possible concern. We take as tenet the observation that nuclear weapons are, from the perspective of science, a weapon without an application. And the observation that politics, at least in these United States of America, is the expression of aggregated perception -- that is, basically, the opposite of science. (I'll take care to develop these two points as the blog evolves.)
Focusing on the NYT article by D. Sanger and W. Broad, the first point of scientific note is the fact that the IAEA report confirms that the Iranians have enriched "small quantities" of uranium to 20%. Of equal import is the observation by Sanger/Broad that the report "makes no assessment of how close it might be to producing a nuclear weapon."
By way of background, let's tackle the question of "enrichment" first. In summary, enrichment is the process of taking uranium the way it's found in nature and processing it into a more pure form. Uranium is a naturally occurring element, found in rock deposits. The concentration of uranium in the ground is tiny so isolating this element takes a lot of dirt and rock and work. The typical way of mining it is open-pit (devastating the natural environment) and the three countries which are the world's largest producers are Canada, Australia, and Kazakhstan. The total world output of uranium is about 100 million pounds per year.
When uranium ore comes out of the ground the uranium is bound up with oxygen (as U3O8, "triuranium octoxide" an "oxide of uranium") and is released by chemical leaching. The resulting powder is brown or black (not yellow, usually) -- this is the "yellowcake" of note in the recent story of Joe Wilson's trip to Nigeria at the behest of the Bush Administration.
Uranium oxide still needs to be processed further to yield more pure forms of the metallic element, 235U the only form which is usable for generating power or making bombs. The reason for this is explained by quantum mechanics and we'll have occasion later to talk about it. The difficulty in isolating or "enriching" the 235U is the same difficulty we had in getting the yellowcake out of the ore that came out of the ground -- scarcity. When we have the yellowcake, the uranium in this powder comes in two varieties. The variety we want, the 235U, constitutes only about 1% of the total amount of uranium. And this uranium is bound up in the molecule U3O8.
The way that the uranium is purified or enriched is a complicated chemical and mechanical separation process which typically uses a large number of large centrifuges. By 'large number' we mean warehouse-sized areas which cover acres. In other words, enrichment facilities are not easy to hide. We'll discuss the details of enrichment in a later entry. (Promises, promises!)
Enriched uranium is classified according to its purity. There are several classes of grading but, basically, there's "low-enriched" and "highly enriched" grades. Low-enriched is less than 20%, sometimes considerably less. Highly enriched is above 20%.
Weapons need 85% and higher enrichment -- a very pure, metallic form of something that started as being bound up in dirt and rocks. The low-enriched form, typically below 20%, what the Iranians have, is only good for generating power.
Returning to the observations made by Sanger/Broad in their NYT article, we see that it's likely that they correctly assess the amount and purity of the uranium that the Iranians possess since these figures square with several sources -- the IAEA, the CIA, and other western government intelligence estimates.
A little more interesting, perhaps, is their observation that the report doesn't say how far the Iranians are in their weapons development program. The short answer is: "many years" -- at minimum, 5 years. At most, 10. (These figures assume that the Iranians would expend huge amounts of capital developing the large facilities we know they don't now have.) It's interesting that the report "makes no assessment." This is a choice, of course, on the part of Amano's IAEA.
My suspicion is that giving the realistic estimate (more than my 5-10 years) takes the punch out of this report. It suggests that we might anticipate a lack of forthright and honest dealing on the part of the new Director.
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