Kirk Sorensen believes firmly that safe nuclear power can contribute significantly to the world’s energy future – provided that reactors run on liquid thorium fuel rather than on solid uranium as they do today.
Showing the courage of his convictions, Sorensen has quietly launched his own thorium reactor company, called Flibe Energy, in Huntsville, Ala. He aims to have liquid thorium reactors operating within 5 to 8 years.
Sorensen says he wants to “redefine” nuclear, so that it deservedly takes on a clean and safe association, contrary to its long running negative place in popular opinion, as swaths of the public fear the hazards of nuclear waste and nuclear power accidents. The industry is fighting harder than ever to improve nuclear’s image after the meltdown earlier this year at Japan’s Fukushima Daiichi plant.
“After Fukushima, everybody is asking whether nuclear power can be safe,” Sorensen (pictured, below) said in an interview. His resounding answer is “yes.”
But it will take nothing less than for the industry to shift from its conventional reactor designs and from the uranium 235 fuel process on which it began to settle in the 1960s, according to Sorensen.
Instead, he says, it has to adopt a liquid thorium technology similar to what nuclear developers built in the 1960s at Oak Ridge National Laboratory in Tennessee, but that lost out (pictured above).
“In the 40s and 50s they had an expansive definition of what nuclear power was – it wasn’t just solid fuel uranium reactors,” said Sorensen, who is Flibe’s president. “But that’s what it has come to mean now.”
Thorium lost in part because it did not create lethal waste - plutonium - that could be used to make bombs the way uranium did. In the heat of the Cold War, the U.S. government and military demanded such deadly material. (Oak Ridge originated in the 1940s to support the Manhattan Project, which developed the world’s first atomic bomb).
Today, other countries including China and India are pursuing thorium nuclear projects. Sorensen believes that thorium should be the pillar of an American nuclear future, because thorium “is so fundamentally different than every other nuclear story out there right now.”
Because his thorium reactor would not produce plutonium, it would mitigate the chance of nuclear weapons proliferation and eliminate the need for utilities to bury plutonium waste.
Although thorium in some designs does produce plutonium waste, that waste is less hazardous than other mixes of plutonium waste, there's less of it, and it decomposes much faster than conventional waste – hundreds of years rather than thousands or more, according to various thorium proponents.
And thorium-based fuel fissions much more efficiently than does uranium 235, meaning a thorium reactor requires less fuel.
That is in part because the fission cycle runs hotter than conventional uranium cycles, said Sorensen. In the Flibe design, thorium reaction temperatures rise to about 750 degrees Celsius to drive gas turbines, compared to conventional reactors, which tend to reach less than half that temperature and drive less efficient steam turbines, he said.
“The hotter you can get, the more efficiently you can turn heat into electricity,” said Sorensen. “Typical reactors today, they only get about one third conversion efficiency. We can get about half.” He also claims that in his design, thorium “isobreeds”, meaning it creates as much fissile fuel as it burns up.
For Sorensen, the key to making it happen is to deploy an unconventional reactor technology, called a Liquid Fluoride Thorium Reactor (LFTR, pronounced “lifter”). It is a type of molten salt reactor, which uses liquid salt rather than water as its coolant, akin to what Oak Ridge developed.
Flibe’s LFTR uses a liquid fluoride salt to serve both as fuel carrier and coolant. The fuel consists of thorium and uranium 233 – different from the uranium 235 used in conventional reactors. It fissions in the liquid, heats up, and passes through a heat exchanger that conveys the heat to fuel-free liquid fluoride salt that eventually drives the gas turbine.
In the event of a total power loss, a frozen plug melts, allowing the fuel to drain into a passively cooled tank where fission stops. Normally, the plug is kept frozen by an external cooling fan.
The company name, Flibe, comes from the scientific term FLiBe, an anagram and acronym for the molten salt that Sorensen uses, which consists of lithium fluoride (LiF) and beryllium fluoride (BeF2).
Another inherent safety feature of the LFTR is that it runs at normal atmospheric pressure, rather than at the 3000-psi that many conventionally cooled reactors require to keep cooling water in liquid state, Sorensen claimed.
Conventional cooling systems can also require external generators to help pump and recombine water, and those generators can fail such as at Fukushima.
Some of Sorensen’s thorium competitors advocate using thorium in conventional reactors like pressurized water reactors, using thorium in solid fuel form, not liquid. They say that would substantially lower the costs of moving to a new fuel, because it would not entail the high-priced development of new reactors.
Sorensen countered that you only get the full benefits of thorium by applying it in a LFTR type reactor.
Sorensen faces huge hurdles. His project won’t be cheap. Flibe co-founder and chief legal counsel Kirk Dorius estimates it will cost at least $1 billion to develop a modest utility-sized reactor (it’s not clear whether that would mean something around or above a gigawatt of capacity).
So Flibe is initially focusing on smaller, “modular”-sized reactors of around 20 to 30 megawatts. Dorius said even that size would cost “hundreds of millions” for “the first in kind demonstrator reactors” but that “mass production” could slash costs in half within 5 years.
He faces stiff resistance from the status quo, as the nuclear supply chain is heavily vested in solid uranium 235. Likewise, other carbon-free alternatives such as wind and solar are gaining traction. And regulators like the Nuclear Regulatory Commission in the U.S. would have to approve LFTR, which is not assured.
If anyone can pull this off, it’s Sorensen, an impassioned thorium zealot who worked as chief nuclear technologist at Huntsville-based Teledyne Brown until he left earlier this year, and who also runs a blog called EnergyFromThorium.
“It’s a challenge,” said Sorensen. “But what is the end product worth to the world? I’d say the benefit is more than compelling enough to take on the risk. If we don’t change the public’s definition of nuclear power pretty soon, it’s going to become more and more difficult to realize the great potential of nuclear energy.”
Top: Wikimedia Commons (from U.S Federal Government)
Lower: provided by Kirk Sorensen