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Thursday, November 28, 2013

Big Engineering 56 Thorium Reactors

         I am not convinced that reactors using thorium are going to answer all the alleged problems of current nuclear reactors. Still less am I going to say that "environmentalists" who now say nice words about thorium reactors would do so if they were ready to deploy.

         On the other hand thorium is 4 times more common than uranium and reactors produce less plutonium, a matter of importance in a world where proliferation is a fear and appears to be considerably easier to design passive safety systems for.

"Thorium reactors would be cheap. The primary cost in nuclear reactors traditionally is the huge safety requirements. Regarding meltdown in a thorium reactor, Rubbia writes, “Both the EA and MF can be effectively protected against military diversions and exhibit an extreme robustness against any conceivable accident, always with benign consequences. In particular the [beta]-decay heat is comparable in both cases and such that it can be passively dissipated in the environment, thus eliminating the risks of “melt-down”. Thorium reactors can breed uranium-233, which can theoretically be used for nuclear weapons. However, denaturing thorium with its isotope, ionium, eliminates the proliferation threat.
Like any nuclear reactor, thorium reactors will be hot and radioactive, necessitating shielding. The amount of radioactivity scales with the size of the plant. It so happens that thorium itself is an excellent radiation shield, but lead and depleted uranium are also suitable. Smaller plants (100 megawatts), such as the Department of Energy’s small, sealed, transportable, autonomous reactor (SSTAR) will be 15 meters tall, 3 meters wide and weigh 500 tonnes, using only a few cm of shielding."

     Note the admission that most nuclear costs are regulatory rather than engineering.

    I am actively not saying that we should hold back deployment of the reactors we can currently build by one day to push these on but we don't have to.

   Designing thorium reactors should pose no insuperable difficulties, after all

"The liquid-fluoride thorium reactor, developed at Oak Ridge National Laboratory in Tennessee during the late 1960s, ran successfully for five years before being axed by the Nixon administration. The reason for its cancellation: it produced too little plutonium for making nuclear weapons. Today, that would be seen as a distinct advantage. Without the Cold War, the thorium reactor might well have been the power plant of choice for utilities everywhere."

     If it could be done 50 years ago when world computer capacity was less than one good laptop today, it can easily be done now.

     I have previously suggested building a factory to mass produce small reactors. Such could easily be retooled to build thorium ones when available (or perhaps better, a second assembly line built alongside). Reactors described above as 3m wide (width of a shipping container) and 15m long are road transportable (or by airship) and could be sold for immediate turnkey operation. If they do not produce plutonium they could be sold to virtually anybody which would help make the entire world wealthy (and the country churning out such reactors on a production line, distinctly rich).

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