Sustainable Energy Recovery with Resources.

I hope to come back and do a follow up on my phosphate post. What I hope to show, that the assumptions of my first post were wrong. That phosphate is a sustainable resource, and that futhermore phosphate can probably be sustained with a positive energy recovery. Many low grade phosphate ore deposits can be expected to have other minerals present also in low grades. This will mean that future phosphate mines will produce a variety of minerals. One of the minerals that will be recoverable will be thorium. Thorium recovery will pay the energy bill for mining the low grade or many times over. Thus if thorium recovery is included in low grade ore phosphate mining, a sustainable amount of phosphate can be recovered prior to the end of human life on the earth. There will always be enough energy recovered from phosphate mining to pay for the energy invested in the mine many times over.

As far back as 1943, Manhatten project scientists including Phil Morrison, Harrison Brown and Alvin Weinberg began to understand the energy implications of nuclear energy. Weinberg later wrote:

Phil Morrison could hardly contain his excitement as he showed me his calculations. If uranium were burned ion a breeder, the energy released through fission would exceed the amount of energy required to extract the residual 4 ppm of uranium from granitic rock.

Morrison's discovery was to have a profound impact on Weinberg for the rest of his long and illustrious career. Harrison Brown, another Manhattan project scientist, also contributed to Weinberg's vision. Brown, along with James Bonner and John Weir wrote "The Next Hundred Years", a book about future resources.

Weinberg was not alone. By the 1950's M. King Hubbert was talking about recovery of uranium and thorium from the rocks.

Hubbert reminds us,

When a U-235 atom is struck by a neutron, it breaks into fragments known as fission products which consist of other atoms near the middle of the table of atomic numbers, and also releases neutrons which strike other U-235 atoms, thereby maintaining a chain reaction. Each fission releases, on the average, 200-million electron volts of heat which, like the heat of combustion of coal or oil, can be used to drive a steam power plant.

The objections to the sole use of U-235 are its scarcity and the large amounts of energy required to separate it from U-238. Hence, very great importance attaches to the possibility of converting the fertile materials, U-238 and Th-232, into fissionable materials by means of the breeder reaction. The breeder reaction for U-238 is shown schematically in Figure 26. In this case, the neutrons from the fissioning of U-235 are used to cause a radioactive transformation of U-238 to Pu-239 which is then fissionable. By a similar reaction Th-232 can be converted to U-233 which is also fissionable. It has been experimentally demonstrated that both of these reactions are possible and are capable of producing from the fertile materials more fuel material than is consumed. Thus, in principle, by means of properly developed breeder reactors, it is possible to consume whole uranium and thorium. In the subsequent discussion it will be assumed that complete breeding will have become the standard practice within the comparatively near future.

Now for the energy that is released by the fissioning of a given amount of uranium (or thorium). As indicated in Table 2, the fissioning of 1 gram of U-235 releases 2.28 x 104 kw-hr of heat, which is equivalent to the heat of combustion of 3 tons of coal or of 13 barrels of oil. One pound of U-235 is equivalent to 1400 tons of coal or 6000 barrels of oil. Within narrow limits the same values are valid for U-238 and for thorium.

Then Hubbert points to the magnitude of the Uranium resource:

the so-called "low-grade" ores are the phosphate rocks and the black shales which have uranium contents in the range of 10 to 300 and 10 to 100 grams per metric ton, respectively. Even so, such rocks are equivalent to 90 to 900 tons of coal or 390 to 3900 barrels of oil per metric ton for the phosphates, and to 30 to 300 tons of coal or 130 to 1300 barrels of oil per metric ton of rock, for the black shales. Even granite, as has been pointed out by Harrison Brown (1954) and by Brown and Silver (1955), contains about 13 grams of thorium and 4 grams of uranium per ton, which is equivalent to about 50 tons of coal or 220 barrels of petroleum per metric ton of granite.

What quantity of uranium in rocks of these various types may there be? An indication of the order of magnitude may be obtained by a glance at the map in Figure 28. The Colorado plateau, which is the principal producer of the high-grade ores, has an estimated ultimate reserve of the order of 50>000 to 100,000 metric tons of uranium. The large supplies, however, are to be found in the so-called "low-grade" ores of the phosphate rocks and he black shales. The Phosphoria formation alone, it is estimated from a recent paper by McKelvey and Carswell (1955), contains about ?400 million tons of uranium. Another 0.5 million tons, at least, can be obtained from the phosphate rocks of Florida and the neighboring states.

The Chattanooga shale in Tennessee contains a stratum, the Gassaway member, about 5 meters thick whose average content of uranium is about 70 grams per metric ton (Kerr, 1955). With a density of 2.5 metric tons per cubic meter, this would amount to about 175 grams of uranium per cubic meter, or to 875 grams per square meter for the total thickness of the member. Then for an area of a square mile the uranium content of this member would be 2.3 X 109 grams or 2300 metric tons. This does not sound impressive, and in fact, as compared with contents of the more familiar metallic ores, it is a trifling amount; nevertheless, the energy content of this member per square mile is equivalent to 30 billion barrels of oil, or to five East Texas oil fields. Uranium-rich black shales of Devonian-Mississippian age, which correlate with the Chattanooga, are widespread in the Mid-Continent area as well as in Tennessee and the neighboring states. In addition, the Sharon Springs member of the Pierre shale of Cretaceous age occurring in an extensive area of North and South Dakota east of the Black Hills is also rich in uranium. No attempt has been made to determine the amount of minable uranium which these shales must contain, but since their areal extent amounts to several hundred thousands of square miles, their uranium content would appear to be as much as several hundred million metric tons.

Although Hubbert had very little to say about the magnatude of Thorium resources, They can only be described as magnificent. WASH-1097 reported the United States Uranium and Thorium resources. Note that while Hunnadt said little of thorium, WASH-1097 reported that for five hundred 1969 dollars a pound, the United States Thorium reserve amounted to three billion tons:
Clearly then if there are enormous amounts of recoverable uranium and thorium in so called low grade ores around the world. The USAEC's estimated $500 in 1969 would be $2900. 45 tons of Southern Appalachian coal cost about $2900 during the winter of 2009. One pound of thorium or in a LFTR or uranium in an IFR would produce the energy equivalent of 1400 tons of coal. Thus the AEC's estimate of a 3 billion ton thorium and a 2 billion ton uranium reserve was based on a recovery cost for thorium that was only 3% of the current cost of coal. If the recovery price for thorium at concentrations of no more than 50 PPM would be 3% of the recovery price for coal. An enormous amount of uranium would also be recoverable at highly attractive prices as an adjunct to the recovery of very low grade mineral ore. For example, gamma ray readings form 131 Fort Worth gas wells indicated a uranium concentration of from 10 to 30 ppm in the enormous Barnett Shale formation. Researchers have suggested that the Barnett Shale formation also contains a rich supply of phosphate. Thus the co-recovery of phosphate and uranium from Barnett Shale seems possible, with more than acceptable EROEI (energy return on energy invested) levels. i have not been able to determine the thorium content of Barnett shale.

Scientists have postulated since 1943 that an enormous amount of energy from supposibly low grade Thorium and Uranium ores, at acceptable EROEI levels. The recovery of large amounts of nuclear raw materials including uranium and thorium appears possible with favorable EROEI. It would also appear that latge amounts of supposably rare minerals such as phosphate are also present along with thorium and uranium in riock formations such as the Barnett shale formation of North Texas. The potential to co-recover these minerals should receive furthr investigation.