[FoRK] PopSci: Can Next-Generation Reactors Power a Safe Nuclear Future?
sdw at lig.net
Thu Mar 24 10:22:24 PDT 2011
It’s too early to begin tallying the lessons learned in Japan, but technically speaking most of what’s gone wrong with Fukushima
Daiichi's 1970s-era reactors has already been learned and accounted for in the latest nuclear power plant technology.
Keeping a nuclear plant safe means keeping it cool in any circumstances, including those in which man-made or natural disaster
knocks out the usual cooling methods. This highlights the importance of safety features built into so-called Generation III-plus
nuclear plant models, the latest feasible plant designs. These redundant and passive safety systems work without the help of an
operator, or even electricity, during times of duress, be it man-made or natural.
Generation III-plus includes a handful of high-tech plant designs, many of which still await regulatory approval. Others, like
France-based Areva’s Evolutionary Power Reactor (EPR) and Westinghouse’s AP1000 (both are pressurized water reactors) are
already under construction, and they are designed to withstand exactly the crisis the 40-year-old Japanese reactors are failing
to deal with, whether operators are around to trigger emergency countermeasures or not.
“The new reactors really have a lot of features that were not available thirty, forty years ago,” says Michael Podowski, a
visiting professor in MIT’s department of nuclear engineering and an expert on nuclear plant safety systems. “These new advanced
reactors will employ more passive safety systems that will make them safe without any external intervention.”
Areva is currently building four EPR reactors, two in China and two in Europe. The design includes four independent redundant
cooling systems, two of which are engineered to survive an airplane crash.
Westinghouse’s AP1000 packs a battery of passive systems that use natural air flow, gravity, and other natural phenomena to
remove pumps and valves from the equation; if the plant begins to overheat these measures will automatically cool the core for
up to three days with no external intervention whatsoever.
Truly safe, secure nuclear power requires plants that simply cannot melt down, and that means going smaller rather than bigger.
Podowski thinks one potential future relies on many smaller, distributed nuclear plants--so-called small modular reactors--that
would contain a small amount of nuclear material, power a small area of the grid, and be protected by a smattering of passive
Because these reactors don’t concentrate too much heat in one place, no active cooling systems would be necessary to cool
them--excess heat would be dispersed in the ambient air. By definition, Podowski says, these small reactors will be safer.
“The small reactors are inherently safe because nothing can happen at the small reactors,” Podowski says. “If something goes
wrong they will be shut down automatically, the heat will be dispersed, and it will bring itself basically to a neutral state
where there will be nothing coming in or out.”
Will such a future come to pass? No matter how one slices any future energy portfolio, nuclear is a major piece. A further
generation of reactors--so-called Generation IV reactors--already exist on paper and explore the possibilities of advanced
cooling systems and other technologies that could make nuclear plants even more productive and safer, though none are expected
to become reality for another 20 years or so. In the meantime, engineers are experimenting with all kinds reimagined nuclear
plant paradigms, from floating nuclear power stations
that are immune to seismic calamity to subterranean systems that are already safely buried deep beneath the ground.
Whether or not the pursuit of these designs is blunted by the Fukushima Daiichi event remains to be seen. Dr. Yaron Danon, a
professor of nuclear engineering at Rensselaer Polytechnic Institute, is waiting to see whether the Japanese crisis will have
the same effect on young people that previous nuclear accidents had on prior generations.
“It’s interesting to see how young people will react to this, the ones who don’t remember Chernobyl or Three-Mile island," Danon
says. "Will they say we shouldn’t build or will they try to design better reactors?”
The Japanese crisis is a human tragedy and an opportunity to learn from past mistakes and re-evaluate the future, he notes, but
giving up on the nuclear age in its adolescence would be a mistake.
“I don’t see a reason why we should eliminate this technology,” Danon says. “When someone dies in a car accident we don’t stop
using cars. We work to make them safer.”
Development of Tiny Thorium Reactors Could Wean the World Off Oil In Just Five Years
ThoriumOne ton of thorium can produce as much energy as 200 tons of uranium and 3.5 million tons of coal, according to the
former director of CERN.
An abundant metal with vast energy potential could quickly wean the world off oil, if only Western political leaders would
muster the will to do it, a UK newspaper says today. The Telegraph makes the case
thorium reactors as the key to a fossil-fuel-free world within five years, and puts the ball firmly in President Barack Obama's
Thorium, named for the Norse god of thunder, is much more abundant than uranium and has 200 times that metal's energy potential.
Thorium is also a more efficient fuel source -- unlike natural uranium, which must be highly refined before it can be used in
nuclear reactors, all thorium is potentially usable as fuel.
The Telegraph says thorium could be used as an energy amplifier in next-generation nuclear power plants, an idea conceived by
Nobel laureate Carlo Rubbia, former director of CERN.
Known as an accelerator-driven system, it would use a particle accelerator to produce a proton beam and aim it at lump of heavy
metal, producing excess neutrons. Thorium is a good choice because it has a high neutron yield per neutron absorbed.
Thorium nuclei would absorb the excess neutrons, resulting in uranium-233, a fissile isotope that is not found in nature.
Moderated neutrons would produce fissioned U-233, which releases enough energy to power the particle accelerator, plus an excess
that can drive a power plant. Rubbia says a fistful of thorium could light up London for a week.
The idea needs refining, but is so promising that at least one private firm is getting involved. The Norwegian firm Aker
Solutions bought Rubbia's patent for this thorium fuel cycle, and is working on his design for a proton accelerator.
The Telegraph says this $1.8 billion (£1.2 billion) project could lead to a network of tiny underground nuclear reactors,
producing about 600 MW each. Their wee size would negate the enormous security apparatus required of full-size nuclear power
After a three-decade lull, nuclear power is enjoying a slow renaissance in the U.S. The 2005 energy bill included $2 billion for
six new nuclear power plants, and this past February, Obama announced $8.3 billion in loan guarantees for new nuclear plants.
But nuclear plants need fuel, which means building controversial uranium mines. Thorium, on the other hand, is so abundant that
it's almost an annoyance. It's considered a waste product when mining for rare-earth metals.
Thorium also solves the non-proliferation problem. Nuclear non-proliferation treaties (NPT) prohibit processes that can yield
atomic bomb ingredients, making it difficult to refine highly radioactive isotopes. But thorium-based accelerator-driven plants
only produce a small amount of plutonium, which could allow the U.S. and other nations to skirt NPT.
The Telegraph says Obama needs a Roosevelt moment, recalling the famous breakfast meeting when Albert Einstein convinced the
president to start the Manhattan Project. A thorium stimulus could be just what the lagging economy needs.
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