Nuclear fuel cycle and greenhouse gas emissions

Scientific American has some odd ideas about sustainable development and nuclear energy

Over at Brave New Climate Barry Brook and others have published reviews of an article published in the November issue of Scientific American magazine.

Brook writes that the November 2009 issue of Scientific American has a cover story by Mark Z. Jacobson (Professor, Stanford) and Mark A. Delucchi (researcher, UC Davis). It’s entitled “A path to sustainable energy by 2030” (p 58 – 65; they call it WWS: wind, water or sunlight).

Brook writes that this popular article is supported by a technical analysis, which the authors will apparently submit to the peer-reviewed journal Energy Policy. They have made both papers available for free public download here.

So what do they say? In a nutshell, their argument is that, by the year 2030:

“Wind, water and solar technologies can provide 100 percent of the world’s energy, eliminating all fossil fuels.”

That’s a big claim and it doesn’t stand up to scrutiny. And here’s where the fighting words begin. It is the “no new baseload” claim of FERC chairman Jon Wellinghoff all over again.

In the SCIAM article, the following objection is raised in order to dismiss the fission of uranium or thorium as clean energy:

Nuclear power results in up to 25 times more carbon emissions than wind energy, when reactor construction and uranium refining and transport are considered.

Even worse, author Jacobson raises the cold war heresy that civilian nuclear power is a precursor to nuclear Armageddon and throws in the “environmental effects” of a nuclear war. Outrageous!

I posted a contribution to Brook’s blog as part of the critique of the article, and offer it here as well since there are by now dozens of comments about the SCIAM piece.

The nuclear fuel cycle and its carbon footprint

Every so often the issue of climate impacts of various fuel cycles comes up. In this note I will discuss some aspects of this issue with regard to nuclear energy.

Any credible claim about GHG emissions by energy source needs to do a stocks and flows analysis and mass balance analysis based on BTUs consumed at each stage of the fuel cycle and related to the type/source of energy inputs.

My challenge to people who say wind or solar is less energy intensive than nuclear must also balance the output issue. A nuclear power plant is producing electricity 90-95% of the time. Wind has 30% uptime and solar sometimes as little has half that amount. The energy inputs, and carbon emissions, for wind and solar have to be multiplied by at least a factor of three to compare them to the energy outputs of a nuclear power plant.

The following is a useful outline for someone who wants to tackle the nuclear fuel cycle.

In the nuclear fuel cycle, uranium is mined either through underground methods or via in- situ-recovery (ISR). The primary energy source is electricity so it just depends on where it was generated and how. Once the raw ore from a mine is trucked to a mill, usually within 50-100 Km, it is processed and converted into yellowcake.

As a rule of thumb for this discussion, you get about 4 pounds of uranium from ton of ore. A ton of uranium (2,000 lbs) requires processing 80 tons of ore which is basically four truck loads at 40,000 lbs each. In the case of ISR mines, the yellowcake is usually produced right at the mine cutting out the transport stage for raw ore.

The energy use, and carbon footprint, to produce one ton of yellowcake is the combination of electricity used at the mine, plus transport of ore (diesel fuel), and electricity used at a mill.

Once the yellowcake is produced it is sent to a conversion factory where the uranium, composed of 99.3% U238 and 0.7% U235 is "converted into UF6 or Uranium Hexafluoride.

The primary energy inputs for conversion are the energy to create the fluorine and the electricity to power the equipment to make the UF6.

The UF6 is sent to a uranium enrichment plant. In the plant, centrifuges spin the gaseous UF6 separating the U238 (heavier) from the U235 (lighter) so that the fissionable isotope can be "enriched" in resulting nuclear fuel from 0.7% to 3-5%. A uranium enrichment plant like the new one in Eunice, NM, that will spool up its centrifuges in December will use electricity to power the centrifuges.

During the Manhattan project in World War II an older technology called "gaseous diffusion" was used which is very intensive in terms of use of electricity. The gas centrifuge process which is used by France and the U.S. is 90% more energy efficient than gaseous diffusion.

Once the "enriched uranium" is ready, it is shipped to a fuel fabrication site where it is made into nuclear fuel pellets and fuel rods/bundles.

The "depeleted uranium" is sent to a deconversion plant where the fluorine is separated out from the UF6, purified, and sold to industrial customers including computer chip manufacturers, pharmaceutical companies, and other high tech users.

Electricity, often from nuclear power plants, a carbon emission free source, often powers deconversion plans and fuel fabrication plants.

The remaining U238 is then sent by truck or rail to a licensed disposal site. Note that "depleted uranium" can never be more radioactive that it was in the original ore because it has been stripped of its U235 isotope during the enrichment process.

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If SCIAM had published a stocks and flows analysis, with numbers, then it would have been credible. What they published isn’t science. It is propaganda. The editors of SCIAM ought to be ashamed to have printed it.

Here’s a song in response to the SCIAM article. It is Aretha Franklin singing “Chain of Fools.”

It is a Fox special from 1993 with Smokey Robinson, Rod Stewart and Elton John providing backup on Chain Of Fools. Enjoy the music!

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