Uranium Extraction: From Mining to Enrichment at 10:36 PM

(Source: http://web.ead.anl.gov/uranium/guide/index.cfm, Depleted UF6 Management Information Network)

The basic steps involved in the process of uranium mining to the production of nuclear reactor fuel are shown in the diagram. Uranium ore is mined, and then transported to a milling facility where it is refined to uranium oxide. The oxide (yellowcake) is then converted to uranium hexafluoride to undergo enrichment. The enriched product can then be processed to reactor fuel for electricity generation via nuclear reactors.

The Big Eagle open pit mines on the south slope of Green Mountain near Jeffrey City, Wyoming. (Picture courtesy of: www.usnrg.com, U.S. Energy Corporation)

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THE STAGES IN MINING AND MILLING

1) EXPLORATION Before mining can actually take place, the uranium ores are located by radiological studies. With the highest-grade deposits buried in deep rock formations, advanced technologies like satellite imagery, geophysical surveys, multi-element geochemical analysis and computer processing are used to search for the deposits. The potential deposits are drilled, and samples are extracted for studies by geologists. It is a long procedure that involves detailed geological and economic evaluation of the grade and characteristics of the orebody. Mining engineers must then develop a mining plan to extract the ore. If the project has potential, environmental impact assessments and the public consultation process begin in order to file applications for regulatory approvals of the project. It is only after permits and licences are in place, that mine activities can begin. It can take decades before a discovery of an orebody can lead to electricity production. For example, Cameco’s McArthur River mine took 12 years to result in commercial production.

2) EXTRACTION Uranium-containing ore is retrieved. Uranium occurs in a variety of ores, and is traditionally mined from open pit or underground mines by drilling and blasting techniques. If the uranium ore is found near the surface, (less than 100 metres deep), the open pit mining method can be used. This method removes the surface soil and rock, and the pit is excavated to access the ore. If the ore is located further below the surface, underground mining methods are more economical. To access the ore, vertical shafts are dug and then tunnels called drifts, are cut directly to the deposit.

The uranium content of the ore is extremely low (usually less than 0.3%), so large amounts of the ore have to be mined. For example, Olympic Dam has an ore grade of 0.05%, which means that for every tonne mined, only 5kg of uranium is retrieved. Thus, large amounts of waste rock are produced during this process. In some cases the ore may be extracted by in situ leaching. This process extracts the uranium from underground by dissolving the uranium from the ore, and then pumping uranium-bearing solution to the surface.

Did you know that uranium is one of the most abundant elements in the earth’s crust? (Picture courtesy of:www.cameco.com, Cameco Corporation)

Cameco’s Key Lake Open Pit Mine in 1994 (Picture courtesty of: www.cameco.com, Cameco Corporation)

3) CRUSHING The ore is usually processed at milling facilities close to the mine site in order to minimize transportation costs, as well as to prevent release of the products into the environment. The ore must be crushed and grinded into smaller fragments. After initial crushing, the ore is passed through a mill which grinds the rock further into a fine powder. It is this process that creates the fine particles that can readily be emitted into the environment. The small size of the rock increases the radioactive surface area, and also makes it difficult to completely isolate from the surroundings.

4) CHEMICAL LEACHING In this process, large amounts of water, sulphuric acid and thickener are added to the ore powder.

The UO2 is oxidised to UO3:

UO3 + 2H+ ====> UO22+ + H2O UO22+ + 3SO42- ====> UO2(SO4)34-

The uranium is able to bond with the acid, and as a result about 90% of the uranium can be separated from the host rock.Sulfuric acid leaching is the most common method, but some mills require alkaline leaching when the ore has basic components which can react heavily with acid.

5) PRECIPITATION and DRYING The uranium solution is purified by ion exchange systems and solvent extration technologies. When the uranium precipitate is extracted from solution, filtered and dried, the product is a yellow uranium oxide (U3O8), called “yellowcake”. Yellowcake contains between 60% and 90% uranium by weight.

6) STORAGE and SHIPPING The yellowcake is then transported to enrichement facilities to be processed to reactor fuel.

Uranium Oxide (Yellow Cake)

Oil-shale extraction technology at 11:17 AM

As a long-term petroleum source, oil-shale reserves are vast but remain elusive. Oil-services giant Schlumberger is aiming to change that with the recent purchase of a radio-frequency (RF)/critical-fluid (CF) extraction technology that unlocks this vast resource and brings it to the surface in a cost-effective and environmentally sound manner.

Oil shale is a type of sedimentary rock that contains solid bituminous material, known as kerogen, that releases oil or gas when heated. While oil-shale deposits are found in many places around the world, the largest deposits by far reside in the Rocky Mountain region of the U.S. Oil-shale reserves are estimated at nearly 2 trillion bbl in the states of Colorado, Utah and Wyoming alone, according to the U.S. Department of Energy. This quantity would be sufficient to meet U.S. demand at current levels for the next 250 years.

However, successfully harvesting this vast resource has been technically, economically, and environmentally challenging. The most common methods of recovering oil shale include a mining step, in which the shale is mined from the surface or underground and then transported to a facility for further processing. The waxy, solid nature of the shale necessitates a heating process, known as retorting, to release the trapped oil and allow it to flow out of the rock matrix.

The large environmental and processing costs associated with this method of oil-shale extraction have prevented it from becoming a major petroleum source. According to an Environmental Impact Statement (EIS) prepared by the U.S. Department of the Interior's Bureau of Land Management, the environmental impacts include emission of greenhouse gases during mining and processing, disturbance of mined lands, need for disposal of the spent shale, use of water resources, and impacts on air and water quality. These factors contribute to the relatively high cost of producing oil from shale, which the EIS estimates at greater than USD60/bbl.

raytheon-rf-cf-web.jpgThe RF/CF extraction technology developed by Raytheon and technology partner CF Technologies aims to lower these environmental and processing impacts dramatically by employing an in-situ retorting process. In this process, wells are drilled into the shale strata using standard drilling equipment. Raytheon's RF transmitters (which have been used extensively for radar and guidance systems) are then lowered into the well. The transmitters emit a radio signal at a frequency that uniformly heats the shale and liquefies the trapped petroleum.

Supercritical carbon dioxide is then pumped into the heated shale formation to extract the oil from the rock and carry it to a producing well. At the surface, the carbon dioxide is separated from the oil, reprocessed, and pumped back into the injection wells. The recovered oil is sent for further processing and refining.



Raytheon estimates that this combination of RF technology to heat the shale followed by a critical-fluid flush to bring the oil to the surface will result in significant environmental benefits and cost savings over other shale-extraction methods. The technology can retrieve 4 to 5 bbl of oil for every barrel consumed during the extraction process, while other in-situ retorting processes reportedly extract only 1.5 to 3 bbl for every barrel consumed.

In addition, the RF/CF technology enables extraction to start 1 to 2 months after the transmitters are activated. Other in-situ methods using in-ground electrical heating systems may take 2 to 3 years to heat the shale sufficiently for oil to flow.

The sale to Schlumberger promises to open up new application areas for this technology and is part of a Raytheon initiative to expand its RF and communication-systems technologies to a customer base outside of the security and defense arenas. Four years ago, Raytheon created the Mission Innovation group within its Integrated Defense Systems (IDS) division, which had a goal of focusing mature defense capabilities to address challenges in energy exploration and the environment.

"Schlumberger is the world leader in bringing new technology to the field for the exploration and production of oil," said Lee Silvestre, vice president of the Mission Innovation group of Raytheon IDS. "Its acquisition of this technology is an important milestone in Raytheon's approach to applying proven technology that can unlock potential in adjacent markets."

To learn more about this oil-extraction technology, contact Raytheon.

The Global Pursuit for Nuclear Fuel at 8:12 PM

Brazil plans expansion to uranium enrichment

Brazil plans to invest $1.8 billion to expand its capability to enrich uranium for commercial nuclear reactors. A conservative estimates is this level of investment could add at least 1-1.5 million SWU/year to its production rate.

Brazilian Energy minister Edisao Labao told local news media the country has 1.1 million tons of uranium to draw on to supply the plant. He said the objective of the new uranium enrichment facilities is to make Brazil self sufficient in its supply of nuclear fuel.

Brazil has manufacting capabilities to take the enriched uranium, as UF6, covnert its to solid powder, and complete production of fuel pellets and assemblies for commercial nuclear reactors. The intial conversion of Yellowcake to UF6 is carried out for Brazil by Areva in France.

Brazil is completing its third reactor, Angra 3, which is expected to enter revenue service in 2015. The government plans to build another four reactors in the next 20 years,

Brazilian nuclear trade press also reported that Brazil plans to export some of its enriched uranium to China and South Korea. Brazilian officials are especially interested in China's market given its ambitious plans to build at least 40 GWe of new nuclear energy power stations in the next 10 years,

UK Proposes using plutonium stocks for MOX fuel

(NucNet) The UK government has proposed using the country’s civilian separated plutonium stocks in mixed-oxide (MOX) fuel for nuclear reactors.

As part of a consultation that was launched on 7 February 2011 the government proposed long-term management options for the country’s civil plutonium stocks.

The three options are:

1. to reuse it in MOX fuel;
2. to immobilize it and dispose of it as waste; and
3. continued long term storage.

The government said its “preliminary view” is that the best option is to reuse the plutonium in MOX fuel.

It said MOX fuel fabrication is a proven and available technology that offers greater certainty of success, while allowing use of the inherent energy resource of the plutonium.

The UK is storing about 112 tonnes of civil separated plutonium. This amount includes about 28 tonnes of material belonging to overseas customers.

In the 1950s plutonium separation was carried out in the UK for defense purposes. In the 1960s when it was thought that fossil fuels would run out, this plutonium was made available as fuel for fast reactors.

Eventually, in 1994, the UK abandoned almost all research into fast reactors because it decided they would not be commercially viable in the foreseeable future.

South Korea pursues spent fuel reprocessing

A contentious negotiation with the U.S. is easing as South Korea agreed to a 10-year joint study to develop spent fuel reprocessing capabilities. It would modify a 1974 accord South Korea signed with the U.S. to not develop this technology.

Since then South Korea has developed a growing fleet of successful nuclear power plants and also entered the global market as an exporter of its designs.

In the latest round of talks, South Korea is said to be proposing development of pyro- processing methods for recycling its spent fuel. The extracted uranium and plutonium would be fabricated into MOX fuel.

(Update 02/11/11: While there is nothing in the news from South Korea about fast reactors, it would seem more likely the output of pyroprocessing would be to produce a new uranium oxide fuel for this type of reactor rather than MOX for an LWR.)

The method does not produce a pure stream of plutonium which makes it attractive in terms of nonproliferation objectives. The Korea Atomic Energy Institute is providing the technical development of the method.

The U.S. contribution will likely come from Argonne National Laboratory which has done R&D work on a pyro-processing technology. (image below via ANL)

High Oil Prices Make Renewable Energy Viable - But Also Grows The Oil Supply at 10:01 PM

People talk a lot about alternative fuels being more viable with oil at such high prices. It also, however, makes other, more exotic, fossil fuel extraction techniques viable. This piece in the UK’s Independent outlines how oil reserves are understated because certain known fields are too expensive to extract at this time - and therefore are excluded from oil reserve projections (an important point that I would wager that many investors don’t understand).

The risk for green investors (and the environment for that matter) is that, if true, tapping oil reserves such as these could grow oil supply over current projections (even if its at these current high prices) - driving out the peak oil scenario longer than anticipated by Wall Street. (This is the kind of stuff investors and analysts miss all the time).

Cool Chart from Oil and Gas Journal Too…

Product Innovation at 11:19 AM

Historically, vertical flight has required a compromise between hover performance and forward speed. If you look at efficiency vs. speed image on the right; the desired helicopter attributes (good hover efficiency, low speed controllability, low downwash, hover endurance) fall to the left of the plot. High disk loading aircraft such as Harriers and JSF, fall on the right of the plot: while fast, their hovering capabilities are limited, and their operational costs tend to increase due to the required power loading. Sikorsky is focused on creating an aircraft that operates to the right on this scale: providing more speed without compromising the essential attributes that make helicopters valuable.

The Sikorsky X2 TECHNOLOGY™ demonstrator aircraft will incorporate several new technologies and demonstrate them in a flight environment. These technologies include an integrated Fly-by-Wire system that allows the engine/rotor/propulsor system to operate efficiently, with full control of rotor rpm throughout the flight envelope, high lift-to-drag rigid blades, low drag hub fairings, and Active Vibration Control. In addition, the aircraft will be used as a 'flying wind tunnel' to determine the main rotor to propulsor aerodynamic interaction, shaft angle optimization for performance, and blade tip clearance for a range of maneuvers. This will allow optimization of the X2 TECHNOLOGY™ suite for future products.

Sikorsky is well on its way in completing the design of the X2 TECHNOLOGY™ Demonstrator with important milestones right on the horizon.