Submitted By: James H. Thomas
Nuclear power as a sustainable, environmentally-sound source of electricity is enjoying a comeback in terms of public opinion, but it still faces public and environmental challenges. On the one hand, the near zero-carbon emissions characteristic of nuclear power plants is attractive to industry and environmentalists alike. On the other hand, concerns remain about potentially-harmful environmental effects of the uranium-based fuels that make it possible.
Nearly all of the concern with nuclear power has focused upon the back end of the fuel cycle, namely the storage and disposal of spent fuel as high-level waste. While spent fuel has been the major focus issue surrounding nuclear power, there is actually another disposal issue at the front end of the fuel cycle: that of dealing with the large quantities of depleted uranium hexafluoride, which is a by-product of the uranium enrichment process.
Since the beginning of the nuclear power era approximately 60 years ago, there has never been an economical solution for the management of the large quantities of these depleted UF6 tails. And yet, an anticipated shift in the near future from foreign to domestic enrichment of uranium will result in a significant increase in depleted UF6 tails produced in the U.S..
A new commercial concept for an environmentally friendly de-conversion process is currently being advanced. The process design extracts high purity fluoride from the depleted tails using their patented process. This process is environmentally-friendly, energy saving, and it allows new and useful products to be created as a result.
A Brief Overview of Nuclear Fuel Cycle
To understand the meaning of “depleted” uranium and de-conversion, it is useful to have an overview of the nuclear fuel cycle.
A form of uranium, enriched in the U235 isotope, is used as fuel in nuclear reactors. In order to use uranium as a nuclear fuel, it must first be enriched, as follows:
1. Uranium that is mined from the earth is converted into uranium oxide or “yellow cake.”
2. The yellow cake is converted to UF6 gas through a multi-step chemical process using various chemicals, including fluorine. In the process, the uranium is converted into UF6 gas.
3. The UF6 gas is passed through a enrichment process at an enrichment facility. In the enrichment process, the U235 atoms present in the UF6 gas are enriched significantly from their naturally-occurring levels.
4. The enriched UF6 is then processed into uranium oxide and fabricated into nuclear fuel.
5. However, about 90% of the UF6 emerges from the enrichment process as depleted UF6, or “tails,” in which the concentration of the U235 atom has been greatly reduced to the level that is not economically or feasibly useful for further enrichment to reactor fuel.
The depleted UF6 tails mentioned in step 5 above have historically been stored in large steel cylinders and ignored for years, or even decades. In the U.S. alone, there is already in excess of 1.6 billion pounds of stored depleted UF6 stored in enough cylinders that if you were to line them up end-to-end they would stretch for more than 130 miles.
At the present time, a vast amount of the enriched uranium required to fuel the existing U.S. nuclear reactors actually is imported from overseas. There is, however, a significant shift in effect towards domestic commercial uranium enrichment. Therefore, the proper management and storage of these domestically-produced depleted UF6 tails will become an important issue confronting the nuclear industry.
Direct Disposal of Depleted Tails is Not Acceptable
Depleted UF6 is a chemical form of uranium that cannot be directly disposed because it is chemically reactive. Therefore, in order to dispose of depleted UF6, some or all of the fluorine must be removed in a de-conversion process. This de-conversion process changes the uranium to a non-reactive (or less-reactive) oxide state. In this new granular or powder, solid state, the depleted uranium can be disposed in approved and licensed low-level radioactive waste landfills.
Historically, there has been little or no economic incentive for de-conversion since the fluorine has effectively been wasted. However, the anticipated dramatic growth in U.S. commercial enrichment creates a need to address the management of depleted UF6 produced from commercial enrichment companies and the new de-conversion process can extract value.
A Green De-Conversion Solution for the Nuclear Fuel Cycle Industry
The de-conversion process design is both environmentally-friendly and economically-valuable. The process utilizes a proprietary Fluorine Extraction Process (FEP) to produce high-purity fluoride gas. FEP can be used to produce a variety of economically-viable pure fluoride gases.
There are several aspects of this new depleted uranium de-conversion process that clearly demonstrate its role as a “green solution” for the front end of the nuclear fuel cycle.
First, de-conversion itself is effectively a recycling process in which valuable fluoride material is recovered from the depleted uranium.
Second, some of the products produced by fluorine extraction are used in manufacturing thin films and photovoltaic (PV) materials for solar applications.
Third, producing fluoride products using FEP will save millions of pounds of CO2 emissions because of the energy efficiency of this process compared to conventional production methods.
As the nuclear fuel enrichment process increasingly takes place on U.S. soil, the Fluorine Extraction Process will offer a solution which is both environmentally-friendly and economically-valuable.
