Friday, April 11, 2008

Thorium EROEI

Yesterday, On the Oli Drum Nuclear debate my friend Keith Akers ask, "but in 10 or 50 years will we be dealing with really low-grade ore that is barely justifiable (or not justifiable at all) in EROEI terms? "

I answered,

"As for Thorium EROEI. First lets establish a basis of comparison. A 1000 MWe coal fired power plant will burn 500 tons of coal per hour under full load. If the EROEI of the coal burned were greater less than 1, the fuels used in the mining, processing and transportation of coal, could be more economically used in generating electricity than mining coal. Therefore the coal has a positive EROEI by a significant margin. 500 tons of thorium can supply all of the energy needed to run 500 1 GW reactors for a year. If it takes the same amount of energy to dig Lemhi Pass Thorium out of the earth as it takes to mine the coal. The relation of the thorium EROEI to the coal EROEI is 24 X 365 X 500 X (coal EROEI). 12,500,000 tons of coal were minded in the US during 2006. This coal provided about 35% of American electricity. In contrast the 600,000 tons assured thorium reserve at Lemhi Pass, could provide all the energy required by the American economy for 400 years."

(I found a report of an EROEI for coal of 11. Plugging in the formula, the given a similar energy input per an equivalent weight unit of thorium, we get an Lemhi Pass thorium EROEI of 48,180,000. Other Oil Drum coal EROEI figures from Charles Hall's April 8th post range from 30 to >100. The EROIE calculation based on 30 for coal is 131,400,000. Calculating at less than 100, we arrive at >438,000,000. Eventually we might work down to ore of around 50 PPM thorium that would last for many, many, many thousand of years. Mining 50 PPM thorium would get us down to an EROEI of 8333. If we simply started to dig up rock and dirt and extract thorium from them we would ene up with an EROEI of 1666.)

"Now consider the famous case of the Rossing mine EROEI which has been discussed on the Oil Drum in the past. The Rossing mine produces uranium ore that assays at 300 PPM. Martin Sevior, who has posted on The Oil Drum in the past demonstrated that the EROEI of the Rossing mine was 500. That is for every unit of energy invested at Rossing 500 could be harvested from the Uranium at a nuclear plant. But there is a problem here. Most of the energy that will be harvested at the nuclear plant will be from U-235. A smaller amount of energy will come from Pu-239 that is produced by nuclear transmutation inside the reactor."

"The potential EROEI of the Uranium mined at Rossing is 100 times greater than what is extracted using LWRs. So potentially the uranium ore at the Rossing mine could produce an EROEI of 50,000. This is at a uranium concentration of 300 PPM."

"Now the thorium at Lemhi Pass is of a purity of between 25% to 63% of the ore. In other words a concentration many orders of magnitude greater than the uranium concentration of Rossing ore. Clearly then we would have to be working with a concentration of fissionable or fertile isotopes far smaller than that found at Rossing before EROEI becomes a serious consideration. I hope this helps."

Update: Comments on The Oil Drum Nuclear Debate is officially closed. The debate can be found here.

4 comments:

charlesH said...

charles,

You said: "In contrast the 600,000 tons assured thorium reserve at Lemhi Pass, could provide all the energy required by the American economy for 400 years."

If we move beyond Lemhi Pass to less rich ore what kind of EROEI are we looking at? What if we extracted thorium from sea water (unlimited reserve)?

Kirk Sorensen said...

Thorium doesn't tend to dissolve in seawater like uranium does. This site shows that there's practically no thorium in seawater.

No worries. There's so much thorium on earth that we'll never run out, unless we're wasteful with it and don't use it effectively.

Charles Barton said...

Charles H., Thorium is an abundant element, and contains an enormous amount of energy. Even if you mined rocks that contained only a few parts per million of thorium, the energy return would be better than mining coal. Thorium is an inexhaustible resource.

ZZR said...

There seems to be an error in your coal production data, the US production in 2006 was about 1055 million tonnes.

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