Fuel of the Future: Smaller, Safer Nuclear Power

China’s HRT-10 Pebble Bed Reactor (image: mit.edu)

All life on Earth depends on nuclear power. The Sun is a giant fusion furnace, and what energy on Earth doesn’t come in one way or another from the Sun comes from radioactive decay at Earth’s core. If it wasn’t for nuclear reactions, Earth would be a cold, lifeless rock. Long decried as unsafe or somehow unnatural, nuclear energy is as natural as solar or geothermal energy, both of which come from nuclear reactions. And as for safety, that’s an engineering issue—just as it’s possible to build either unsafe or safe boilers and furnaces, depending on the design and care with which they’re constructed, it’s possible to build either unsafe or safe reactors.
There are in fact highly promising reactors not merely in development, but which have years or even decades of safe operation behind them. One of the most promising is the pebble bed reactor (PBR) in which the fuel is made up tiny particles of radioactive material embedded within inert shells.

Cross section of a fuel pellet or “pebble,” showing tiny reactive particles embedded within a graphite shell. (image: ens-newswire.com)

What makes a pebble bed reactor safer than traditional reactors? First, their reactions slow above a certain temperature. They literally can’t go critical (overheat and cause a “meltdown”)—if coolant is lost, the temperature will rise; and as temperature rises, the reaction slows down. They will hit an equilibrium temperature and stay there, with no need for expensive or complicated safety equipment that can itself be a source of failure.

Second, unlike conventional reactors which typically use water or other liquids for cooling, PBRs use gas, such as non-reactive helium. Not only does helium not absorb radioactivity as readily as water, making it inherently safer, but if there is a leak, the lighter-than-air helium will simply float away, cutting off the coolant and slowing the reaction.  Third, PBRs can use less enriched fuel than do conventional reactors, reducing the risk of nuclear proliferation—their fuel, whether spent or active, can’t be turned into atomic weapons.

Also PBRs, can be built small and modular, as a Wall Street Journal opinion piece by Bob Metcalfe explained.  This allows them to tailored to the need, built more inexpensively, and installed where energy is required. That last element—the ability to install small reactors wherever you need them—puts PBRs ahead of solar, wind, hydroelectric, or geothermal, which have to be built where the Sun shines brightly without cloud cover, the wind blows, rivers flow, or the Earth’s heat rises near the surface.

PBR safety is not theoretical; it’s been put to the test. For example, a German PBR ran for 750  weeks—over two decades—and even had its coolant deliberately cut off without any meltdown or other significant problems. The Chinese HTR-10 pictured above has been in operation since 2000 without issue.

More generally, as is often forgotten, there is actually a wealth of experience in running small reactors under challenging conditions without problems. The U.S. Navy, has been operating nuclear-powered submarines and aircraft carriers since the 1960s. They’ve sailed nuclear reactors through typhoons and into harm’s way without incident.

In some important ways, nuclear power is an ideal power source. For example, it is completely non-carbon emitting, so it does not contribute to global warming. (In contrast, a conventional coal plant might emit 4 million tons of carbon dioxide per year.) Also, the United States has the world’s fourth-largest uranium deposits, and two of the top three nations—Canada and Australia—are fast friends.  Both energy independence and national security (from not having to rely on unfriendly regimes) would be enhanced by greater reliance on nuclear power.

There are large hurdles to exploiting nuclear energy. One is waste disposal, though there are a number of proposed schemes for it. The reason those plans have not come to fruition is the second barrier: public opinion. More than any other energy source, nuclear power is subject to NIMBY—“not in my back yard.” This makes choosing locations for reactors and waste disposal facilities difficult.
The third big barrier is the regulatory climate. Passing a camel through a needle is less difficult than getting a new commercial reactor design approved in the U.S. Not one new commercial reactor has been approved in the last 30 years, and several companies exploring the potential of PBRs or other advanced reactor designs estimate that the approval process alone could take $50mm of capital—with no guarantee at all of success. That makes it very difficult to line up the necessary funding; who wants to put that much money on the line, subject to a hostile bureaucracy? This last hurdle, though, is one the administration could change with the stroke of pen if it chose.

The more alternative power sources we develop, the less carbon we’ll emit, the less we’ll rely on nations that don’t have our interests at heart, and the more we’ll be able to preserve fossil fuel, a finite resource, for those uses it does best (like transportation). Maybe it’s time to recognize that nuclear power, as much as solar or wind, is an alternative worth exploring; maybe it’s time for an administration committed to energy independence and reversing global warming to encourage, not discourage, safe nuclear energy.