Sunday, May 3, 2015

Shouldn’t we be thinking of a nuclear future?


From page A10 | June 25, 2014 |

In a romantic attempt to reduce the real threat of global warming, retail sellers of electricity in California will be required in five and a half years to more than double the share of power they get from renewable sources.

Today, approximately 17.1 percent of in-state generation comes from biomass, geothermal, small hydro, wind and solar. Of the power we import from out of state, 12.2 percent is known to be from these technologies. However, almost half of the electricity we import comes from unknown sources. By 2020, renewables are supposed to make up 33 percent of our portfolio.

In 2012, Californians consumed 302,000 gigawatt hours of electricity. We produced 65.9 percent of that and imported the rest.

Most California-generated electricity (61.1 percent) is derived from natural gas. We produce very little from coal (0.8 percent) or oil (0.045 percent). However, of the known sources of electricity we import, 39.5 percent comes from coal-fired plants.

Not all of the power we produce in-state which is not classified as “renewable” dumps greenhouse gases into the atmosphere. Large hydroelectric dams generate 11.7 percent of our electricity; and nuclear power makes up 9.3 percent.

I am not sure why large hydro and nuclear don’t count toward what the state calls its “renewable portfolio standard,” when our ambition is to reduce atmospheric greenhouse gases. Neither of those threatens our climate.

Yet, in the wake of the Fukushima Daiichi disaster of 2011, no one is seriously contemplating adding more nuclear power plants to our mix. The last thing “greens” in California want is to risk the meltdown of a reactor core. Additionally, there remains a question of what to do with nuclear waste.

But what if there were a safer nuclear option? One that required almost no uranium or plutonium, did not employ a light-water reactor which requires its water to be cooled under high-pressure, ran on a commonly available fuel source, produced less than one percent as much waste, and its waste were radioactive for a far-shorter horizon than comes out of today’s conventional nuclear power plants?

The answer may be nuclear power from thorium. Or more precisely, a molten salt-cooled liquid-fluoride thorium reactor.

Back in the 1960s, the United States researched the possibility of using thorium in place of uranium. However, when it was found that thorium was a poor fuel for making nuclear bombs—our primary interest at Oak Ridge National Laboratory—we gave up on its promise as a fuel for electric power production.

Today, basing its technology on what we learned 50 years ago, China is poised to become the world’s leader in these safer, greener power plants. According to The Economist, the Chinese Academy of Sciences expects to fire up a prototype thorium reactor in 2015 using solid fuel. The Shanghai Institute of Applied Physics projects to have one in operation that uses molten thorium fluoride by 2017.

The Chinese are collaborating with a group of nuclear engineers from UC Berkeley, led by Per Peterson. Prof. Peterson, whose funding comes from the U.S. Dept. of Energy, has invited me to his lab next month to see “the work we’re doing in high-temperature reactor technology using fluoride molten salt coolants.”

Peterson’s colleague, Prof. Ehud Greenspan, explained to me that what makes thorium safer than uranium are the molten salt coolants.

“Many people also prefer thorium because the nuclear waste it generates is almost free of plutonium, americium and curium,” Greenspan said. “But the thorium waste is not benign; it requires careful handling.”

Yet dealing with nuclear waste from power plants may have a solution. Since 1999, plutonium waste from nuclear weapons has been safely buried deep under ground in salt beds near Carlsbad, New Mexico.

At the Waste Isolation Pilot Plant, “holes are bored into walls of rooms carved from salt,” according to the New York Times. “At a rate of six inches a year, the salt closes in on the waste and encapsulates it for what engineers say will be millions of years.”

As The Economist reported in April, waste products from a liquid -fluoride thorium reactor “are less hazardous than those of a light-water reactor. There is less than a hundredth of the quantity and its radioactivity falls to safe levels within centuries, instead of the tens of millennia for light-water waste.”

One technical problem with thorium is that it is not fissile. That is, it cannot be split to make a nuclear chain reaction. That’s why it’s bad for making bombs. Instead, according to Wikipedia, in a liquid-fluoride thorium reactor, “thorium and uranium-233 are dissolved in carrier salts, forming a liquid fuel.

“In a typical operation, the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.”

In order to meet the 2020 target for renewables, the California Public Utilities Commission projects a huge increase in solar and wind in the next few years.

Yet even if we meet this mandate, it seems to me there is a need for a safe power source like thorium nuclear, which reliably generates electricity 24 hours a day and does not emit greenhouse gases.

This is especially true if drivers in our state move away from gasoline and diesel engines toward those which run on electricity or hydrogen.

Thorium power may not quite be ready. But once it is, California should be prepared to accept it as a clean source of power which can replace coal, gas and conventional nuclear.

— Rich Rifkin is a Davis resident; his column is published every other week. Reach him at [email protected]



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