Atomic Numbers

If a pair of recently-approved nuclear reactors is built in Georgia, they would be the first new additions to America’s fleet of atomic power stations in nearly thirty years. A look at some numbers reveals that we need to be building more such installations, faster – at least on the order of a couple per year – if we expect to meet our burgeoning electricity demand. Those same numbers reveal that such a nuclear building boom is necessary even as we bring other power generation technologies to full capacity.

The total U.S. electrical generating capacity is 1,075,677 megawatts (MW). The U.S. Department of Energy tells us we’ll need 30 percent more power by 2035, for a total of 1,398,380 MW. We need to find another 322,703 MW somewhere.

Any honest discussion of large-scale electricity generation should include an evaluation of each technology’s “capacity factor,” which takes into account its actual vs. potential output. Capacity factor is not just a simple measure of how long a power station stays “on line,” but of how much power it supplies when it is. This is important in evaluating its suitability as a baseload power provider.

Capacity factor is the ratio, expressed as a percentage, of a power station’s actual output over a period of time – usually a year – and its output if it had operated constantly at its full installed capacity. A station with an installed, or “nameplate,” capacity of 100 megawatts would produce 876,000 megawatt-hours of electricity in a year if it ran at full capacity 24 hours a day. But if it produces only 700,000 megawatt-hours in that year, it would have an annual capacity factor of 80 percent. Capacity factor is affected most directly by maintenance requirements and fuel availability (remember – water, wind and sunlight are also fuel).

Here are the capacity factors for today’s current technologies:

Solar, photovoltaic panels: 20%-30%
Wind turbines: 20%-40%
Solar, heliostats and molten sodium: ~65%
Hydroelectric dams, run-of-river: 65%
Coal: 74%
Hydroelectric dams with reservoirs: 90%
Geothermal: 90%-98%
Nuclear: 95%-98%

By the numbers, both types of hydroelectric installations plus geothermal and nuclear are our best bets for reliably meeting the energy challenge, with nuclear development being crucial. Of the others listed above, photovoltaic solar installations and wind farms are just not generating a lot of investor interest given their low capacity factors, and it will be about 10-15 years before solar molten sodium technology (using stored heat to drive steam turbines) is producing power from just a handful of plants. And it’s fair to say that fossil fuels – coal in particular – are high on no one’s list.

America’s total geothermal potential, according to United States Geological Survey, is 95,000 to 150,000 megawatts. Geothermal generating stations already have 3,153 MW on line, so 146,847 MW is waiting in the wings.

Today 2,400 dams provide about 10 percent of America’s electricity, with an installed capacity totaling around 80,000 megawatts. The DOE estimates that between new construction and upgrades of current installations, there is another 30,000 megawatts of domestic hydroelectric capacity available. But that would require developing a whopping 5,677 separate sites.

With just 104 reactors, nuclear generating stations currently provide nearly double the electricity from hydro. There are another 28 reactors currently proposed, with a combined capacity of more than 31,000 megawatts. Unlike wringing the last remaining capacity out of geothermal or hydroelectricity, that increase would be just the beginning.

If we add geothermal’s remaining potential capacity to that of a totally optimized hydroelectric industry, we are still 145,856 megawatts short of our projected need.

Our only choices for reliable power generation would be to increase our burning of fossil fuels by 26 percent (from the current 559,352 MW to 705,208 MW), or build another 80 or 90 nuclear generating stations – or more, because unlike hydro and geothermal, this is one power source that can’t be “built out.”

Of course, more reactors – even little modular ones – mean more waste. Right now the United States is seeking suitable permanent storage for the 50,000 metric tons of spent nuclear fuel that’s accumulated to date. While that sounds like a lot, it is not so much bulky as it is dense. Stacked uniformly on a football field, the pile would be just one meter high. But with technology now on the horizon that pile could be made to disappear. Areva, the world’s largest nuclear energy company, says it is developing a special waste-burning reactor that could reduce the stockpile by up to 99 percent.

Bill Gates has also taken a high-stakes hand. As a principal investor in TerraPower, Gates is betting on a new type of unit called a traveling wave reactor. A TWR operates differently from other types in that the entire core does not undergo fission at the same time. Instead, only a localized area reacts as fuel is shuffled to it slowly. The core itself is all low-grade fuel – it will work just fine using the unprocessed waste from conventional reactors and can even use natural, un-enriched uranium.

The TerraPower design is expected to be so efficient that its TWR could operate for up to 100 years on a single load of fuel. The company expects to have a prototype in the 300 megawatt range producing commercial power in ten years, and has a design for a 1000 megawatt model as well.

But the truth is, nobody ever attacks nuclear power generation for being inefficient. It’s simply that radiation scares people. Among the ways nuclear technology can deliver a dose are routine releases during plant operation, plant accidents, accidents in transporting nuclear materials and the escape of nuclear waste from confinement. Dr. Bernard Cohen, Professor Emeritus of Physics at the University of Pittsburgh, offers the probabilistic assessment that all of those events combined carry a risk of having one’s lifespan shortened by less than an hour. He goes on to state that electricity generation by fossil fuels shortens our lives by up to 40 days.

It is important to note that nuclear generating stations are nowhere close to being our worst radiation threat. The 3.5 million tons of coal burned to produce one gigawatt of power contains more than five tons of uranium, an alarming amount of which is released into the environment in fly ash. U.S. Secretary of Energy Dr. Steven Chu (Nobel Prize, Physics, 1997) says a typical coal plant emits 100 times more radiation than a nuclear facility. Considering that just one ounce of uranium fuel contains the energy of four tons of coal, just 27 tons of uranium would produce that same gigawatt with an orders-of-magnitude reduction in released radiation.

If you’re still with me by this point, you’ve read a lot of numbers. Those numbers constitute an empirical call to action on several energy fronts, with one in particular. By the numbers, accelerated expansion of America’s nuclear power generating capacity can no longer be regarded as just optional. It is a necessity.