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Environment

Trouble With Thorium

March 1, 2010 | A version of this story appeared in Volume 88, Issue 9

"Reintroducing Thorium" was extremely interesting (C&EN, Nov. 16, 2009, page 44). Judging from this article, thorium has tremendous potential to provide the energy that society desperately needs without causing massive environmental problems or the potential for further nuclear weapons proliferation.

Naturally, I wondered why no one else was talking about this topic, particularly while the Copenhagen negotiations were taking place. A search for "thorium" in the New York Times led to a column called "Ask AP," in which Associated Press writers research topics in response to reader requests. AP energy writer Mark Williams researched thorium and reached conclusions that were very different from those of the C&EN article. He quoted Ed Lyman of the Union of Concerned Scientists, who said that "a lot of the hype that one hears about thorium fuel is indeed too good to be true" and that thorium cannot replace uranium and plutonium.

He also cites Felix Killar of the Nuclear Energy Institute who said that fission of thorium still produces uranium and plutonium that could be used for nuclear weapons, just in smaller quantities. Killar also said that thorium also does produce waste, and there still would be the need for long-term disposal. Killar did not mention, as the C&EN article did, that thorium waste would only be radiotoxic for tens of years as compared with thousands of year for uranium waste.

The C&EN article commented that thorium proponents are favoring blogs, podcasts, and Google TechTalks over peer-reviewed journal articles for getting the word out about thorium. Given the skepticism expressed by the two AP sources mentioned above, I wonder if avoidance of peer-reviewed journals by these authors is a sign that something is fishy. Of course, it could also mean merely that they want to reach a much wider audience than that of a nuclear chemistry journal.

I hope that C&EN will continue to follow this topic aggressively and also look into the reasons for the apparent skepticism of the AP sources. If thorium indeed has the wonderful potential described in the C&EN article, we need to push as fast as possible in developing these technologies. If those who stand to gain most by maintaining the status quo are purposely trying to distract us from advancing these technologies, we need to expose these people for what they are. And if charlatans are trying to scam investors by distorting the truth about the potential of these technologies, this also needs to come to light.

I will look to C&EN as one presumably objective and knowledgeable source of information on this topic. For the record, I have no background in nuclear chemistry and, to my knowledge, no investments in thorium technology.

John M. Wetzel
Albany, Ohio

"Reintroducing Thorium" startled me in several respects. My first thought was that these new proponents of using thorium for nuclear power generation were "reinventing the wheel," because that approach had been studied quite extensively decades ago. Then I saw that these proponents state that the "idea never took hold primarily because thorium-fueled reactors don't provide the opportunity to make and collect materials that can be used to build nuclear bombs."

That statement is not only of questionable technical accuracy (U-233, which is produced by irradiating thorium, can be used to build nuclear bombs), but also, it appears to me, it amounts to a fanciful reinvention of history to suit their own political purposes. They say that Pu-239, which is produced by irradiation of uranium, was a much-needed bomb material at that time; that is true, but they don't say that the Pu-239 that is present in spent power reactor fuels is diluted by such large quantities of other plutonium isotopes that it was not desired for use in bombs.

I believe there were many technical reasons for a thorium fuel cycle not being pursued; if these new proponents have overcome these technical issues, good for them, but they shouldn't present false conclusions about reasons for earlier decisions. It was also disconcerting to read that these proponents prefer not to publish papers in conventional journals, but instead write blogs, post podcasts, and give Google TechTalks; it appears that they could profit greatly from the review process employed by conventional journals.

John L. Swanson
Richland, Wash

As good as thorium power is on paper, one should not assume all that the virtues claimed for it aren't already, in uranium reactors, far enough off the drawing board that they deprive fossil-fuel vendors and governments of billions in fossil-fuel revenue every week.

Heavy-water reactors, for instance, burn unenriched uranium. Like thorium, it is nearly inexhaustible.

The recent uranium price spike, although it topped out at less than $4.00 per barrel of petroleum equivalent, triggered a prospecting effort that has been finding more than 100 million bbl of petroleum equivalent per day. And all varieties of power reactor seem, in practice, to have been perfect in their immunity to involvement in nuclear weapons proliferation, despite lacking this immunity in theory.

G. R. L. Cowan
Cobourg, Ontario

"Reintroducing Thorium" is a little too uncritical when it passes along the rosy opinions of thorium enthusiasts. Here are some of the not-so-fine points the reporter's sources failed to tell him: The article states that "at no point in the thorium cycle, from mining thorium minerals to preparing and 'burning' reactor fuel to managing the waste, can fuel or waste products be converted into nuclear bomb materials."

This is wrong for at least three reasons: First, although a thorium reactor can indeed be operated to produce as much fissile fuel as it consumes, it has limited breeding potential. So each new reactor must be primed with fissile material from elsewhere—meaning either plutonium from today's reactors or enriched uranium.

Second, any kind of reactor can be used to create weapons-quality plutonium by irradiating special uranium-containing fuel elements for short periods and then separating the resulting Pu-239. Thorium reactors are no exception.

Third, isotopically pure U-233 is a good bomb material. Some thorium enthusiasts like to point out that the U-233 is usually contaminated with U-232, rendering it too radioactive to make a bomb; however, it is quite feasible to use chemical means to separate the 27-day Pa-233 from the fuel and then let it decay into isotopically pure U-233. In fact, that very process is part of some proposed thorium fuel cycles.

In other words, for assurance that a nuclear power program is not being subverted, there must be effective international oversight of all enrichment and fuel-processing activities, regardless of reactor type.

The article states that thorium "is roughly four times more abundant than uranium." When used in fast reactors, uranium itself is inexhaustible.

The article states that thorium "does not need to undergo a costly and complex enrichment process to render it usable in a nuclear reactor." This is misleading. A source of U-235 or Pu-239 would be needed as long as new thorium reactors continued to come on-line.

The article says that "although waste products from thorium usage are radioactive, radiotoxicity persists for just tens of years rather than thousands of years as uranium waste does." It quotes David LeBlanc, "a staff physicist at Carleton University, in Ottawa, and a nuclear reactor specialist, [pointing] out several safety-related differences between [liquid fluorine thorium reactors] and today's commercial reactors." Both of those statements wrongly assume that thorium reactors would be in competition with thermal reactors (the kind that are in use today), but thorium technology is far from mature.

Although the thorium cycle offers a clean, feasible, and possibly economical way to generate electricity, it is farther in the future than its main competitor, the Integral Fast Reactor (IFR). Continued development of the thorium cycle would not be unreasonable, but avoiding prompt demonstration of IFR technology would be a mistake. There is lots of room for healthy competition as reactor deployment proceeds.

George S. Stanford
Downers Grove, Ill.

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