Wednesday, September 30, 2009

Is Nuclear Energy Renewable?

Broad support for nuclear energy is growing. The once maligned energy source is finding new friends across the political and social landscape from California Governor Arnold Schwarzenegger to Bob Geldolf of the Boomtown Rats. Conservatives Sarah Palin and Rush Limbaugh have been talking up nuclear energy for some time. Now even people like liberal columnist Thomas Friedman and Dr. Patrick Moore, one of the founders of Greenpeace are advocating a nuclear expansion. All this is happening because people are becoming more educated about nuclear energy. They are beginning to view the anti-nuclear crowd as close-minded and unable to acknowledge the differences between nuclear weapons and the peaceful, safe uses of nuclear energy.

With this kind of support building, it's time to answer an important question...

Is Nuclear Energy Renewable ?

It's an important question because "renewable energy" is viewed by governments, policy makers and opinion leaders as the path to a cleaner, safer world. In addition, "renewable portfolio standards," designed to reduce carbon emissions and cut fossil fuel consumption by forcing utilities to generate part of their power from renewable sources, ignore the carbon-free contribution made by nuclear energy facilities. Permitting utilities to credit nuclear energy towards meeting renewable portfolio standards would help the nation meet greenhouse gas reduction targets more quickly and more cheaply.

It's time to examine the definition of "renewable" and determine if nuclear energy deserves to receive the RENEWABLE seal of approval.

First let's look at the definition of RENEWABLE. The Energy Information Administration, a non-partisan section of the US Department of Energy, is tasked with providing "policy-neutral data, forecasts, and analyses to promote sound policy making, efficient markets, and public understanding regarding energy and its interaction with the economy and the environment." The EIA defines "renewable energy," as “Energy sources that are naturally replenishing but flow limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time." The EIA currently recognizes biomass, hydro, geothermal, solar, wind, ocean thermal, wave action and tidal action as renewable energy sources.

There are three key phrases in the renewable energy definition: "naturally replenished", "virtually inexhaustible" , and "limited in the amount of energy available per unit of time."
We'll evaluate the attributes of nuclear energy against each of these three criteria to determine if nuclear meets this definition of renewable.

Criteria 1: Is nuclear energy naturally replenished?

Nuclear energy is naturally replenished under the certain conditions. Most people view nuclear fission as a man-made phenomena, and would be surprised to learn about the Oklo Natural Nuclear Reactor.

The Oklo reactor was a naturally occurring fission reactor that operated in west Africa up until about 1.7 billion years ago. Not only did scientists discover that nuclear fission has occurred in nature, they also determined that "breeding" occurred naturally in the Oklo reactor. "Breeding" is what scientists and engineers call the process by which nuclear fuel is naturally replenished as a reactor operates. The Oklo reactor was an amazing natural machine that ran, produced heat, and bred some of it's own fuel for 2 billion years!

Breeding nuclear fuel is not just a hypothetical possibility; mankind has already demonstrated breeding on a commercial scale. In fact, the final core that ran in the Shippingport reactor in PA was an experimental breeder core. Analysis of the Shippingport core after five years of operation proved that there was more fuel present at the end of life than when they started it up. In fact, after five years the core was still going strong and was shut down only because the experiment had ended.

Thus, criteria 1 is met because through the process of breeding nuclear energy is naturally replenished.

There are other arguments that support the "naturally replenished" criteria. For example, some scientists and engineers believe that uranium can be commercially extracted from seawater. Since rain and erosion naturally washes uranium out of rocks and into the sea where it would be collected, the rain provides an additional mechanism naturally replenishing our nuclear fuel supply.

Finally, nuclear fuel can be recycled through "re-processing" in which impurities are removed from used nuclear fuel. This allows the fuel to be reused over and over again greatly extending its life and increasing the amount of energy extracted from it. While this is not a natural process, it further supports the concept of a fuel supply that can be replenished.

Criteria 2: Is nuclear energy "virtually inexhaustible?"

Some anti-nuclear groups argue that the supply of uranium will limit the expansion of nuclear energy. According to the European Nuclear Society, there are sufficient known uranium reserves to power the world's reactors for "several decades." That would certainly NOT support the "virtually inexhaustible" criteria, but that is not the whole story. This statistic accounts for only "known" uranium reserves. Uranium is a fairly abundant mineral and most experts believe there is a lot more uranium available that will be discovered when market demand rises and there is economic incentive for prospectors and mining companies to search for more. There are recent examples to support this belief. For example, just one newly discovered uranium vein under a Virginia farm contains enough ore to power all the reactors in the USA for two years.

The limited supply argument also completely ignores the existence of thorium, another fissile element that is even more abundant that uranium. There is sufficient thorium to run our entire electric grid on nuclear fission for more than 1000 years. Thorium has many useful properties that make it an excellent fuel for commercial reactors, but that is beyond the scope of this discussion (go to Energy From Thorium for more info).

Finally, as breeder reactors become more commonplace the ability for nuclear fuel to be naturally replenished will add to the already abundant fuel supply.

Criteria 2 is met:
taking into account the abundance of uranium and thorium, recycling, and breeding, the nuclear fuel supply is virtually inexhaustible. With the use of already demonstrated technologies mankind is unlikely to ever run out of fuel for nuclear reactors.

Criteria 3: Is Nuclear Energy "Limited"?

The final criteria the EIA uses to describe renewable energy is "limited in the amount of energy available per unit time." This is an interesting criteria because the use of the word "limited" is highly subjective. All energy sources are "limited" because each provides a finite amount of energy per second, minute, or hour. It's even more curious to consider why the EIA would establish a criteria that conflicts with a goal of any usable energy source: to be available WHEN needed and IN THE AMOUNT needed? The use of "limited" in this context describes an attribute of existing renewables (wind, solar, tidal, geothermal, and biomass) rather than a criteria by which other energy sources should be measured for entry into the club. In fact, it can be argued that "limited" is an undesirable attribute rather than a criteria. For these reasons we won't consider "limited" a criteria energy sources must meet to be considered renewable, but rather an attribute to describe the existing inventory of renewable energy sources.

When compared to low density, intermittent energy sources, nuclear energy is a superior on-demand, large scale energy source.


While the US government does not presently characterize nuclear energy as a renewable energy source, there is an undeniable scientific basis for considering nuclear energy "renewable" because
  • nuclear energy is naturally replenished, and

  • nuclear energy is virtually inexhaustible
In fact, nuclear energy is a superior renewable energy source because it meets these criteria and it is available on demand in large, controllable quantities.

Based on the above Energy Information Administration and policy makers should recognize that nuclear energy is a renewable energy source. In addition, existing and proposed Renewable Portfolio Standards should be revised to allow full credit for nuclear generated electricity. Doing so will foster creation of a level playing field in which technologies can succeed or fail based on their technical merits, costs, and benefits provided.

Printable Version (pdf)

1 comment:

Canon said...

"ignores the existence of thorium, another fissile element"

Thorium is not fissile. It is fertile, exactly the same as uranium. As with uranium, it can be used to sustain a nuclear reaction, as long as there is sufficient fissile starter material.

In the case of uranium, this starter material consists of the tiny amount of fissile isotope uranium-235 resident in naturally-occurring uranium, which is then concentrated (or "enriched").

In natural thorium, there is no such resident fissile isotope. Fissile material, such as enriched uranium or plutonium, must be added to thorium in order to make and sustain a nuclear reaction.