|Fig. 1: Highly Enriched Uranium (HEU). (Source: Wikimedia Commons)|
By 1991, the Cold War had come to an end, leaving the newly formed Russian Federation with large stockpiles of highly enriched uranium (HEU) originally intended to create nuclear weapons. These stockpiles, amounting to approximately 500 metric tons, were capable of producing up to 25,000 nuclear warheads.  In an attempt to prevent a Cold War sized nuclear arsenal and deter global proliferation, the Bush administration struck a deal with Russia to convert its surplus HEU to low enriched uranium (LEU) and sell it to the U.S. as fuel for civilian nuclear power plants. Formally titled the "Agreement between the Government of the United States of America and the Government of the Russian Federation Concerning the Disposition of Highly Enriched Uranium Extracted from Nuclear Weapons," this deal effectively transformed tons of Russian HEU into fuel for American electricity generation, leading to the informal program name "Megatons to Megawatts." 
President George H. W. Bush initiated the HEU deal with Russian leaders in October 1991 to address major nuclear proliferation concerns following the drawdown of the Cold War and dissolution of the Soviet Union.  The end of the Cold War fostered an environment that created the potential for nuclear weapons, the fissile material that created them, and Soviet military technical expertise to disperse among terrorist groups, rogue organizations, or nuclear ambitious state actors. While simultaneously addressing American proliferation concerns and energy needs, a deal between the U.S. and Russia opened the door for billions of U.S. dollars to help alleviate the struggling Russian economy and its nuclear industry's lack of government funding. The U.S. and Russia signed a formal agreement in 1993, which required Russia to down-blend 500 tons of HEU over the course of 20 years. 
The Megatons to Megawatts program called for commercial organizations to administer the deal. Therefore, the U.S. Department of Energy created the United States Enrichment Corporation (USEC) to execute the program, and Russia's Ministry for Atomic Energy tapped Techsnabexport (TENEX) to do the same. Enriched uranium fuel used in commercial utilities is valued into two separate components: the physical LEU feedstock and the separative work units (SWUs) involved in the conversion process to enrich the uranium. When purchasing down-blended Russian HEU, the U.S. had originally intended to pay for both the SWU and uranium components in full. However, the U.S. Congress passed a bill in 1996 that privatized USEC and restricted its ability to pay for the uranium component. Without a formal agreement for peaceful nuclear cooperation, Washington and Moscow struggled to find a solution to render appropriate payment for the uranium component. In 1999, an agreement was ultimately reached that allowed USEC to ship an equivalent amount of the uranium component to Russia and solely pay for the SWU component. Completion of the HEU program concluded in 2013, ultimately resulting in the transfer of 500 tons of down-blended Russian uranium to American power plants. 
Typical commercial nuclear fuel is created by enriching naturally occurring uranium to higher composition levels of the fissile isotope uranium-235 (235U). Uranium-238 is the most common isotope found in nature, whereas 235U is found at concentrations around 0.7%. Higher concentrations of 235U are required to be used as nuclear fuel and produce a chain reaction capable of sustaining a steady stream of neutrons necessary for fission. Most commercial nuclear fuel contains uranium at levels around 5% enrichment, whereas nuclear weapons grade uranium is enriched to levels around 90%. In the case of the HEU agreement, Russian weapons grade uranium had to be down-blended to commercial fuel levels. This was achieved by mixing the HEU with natural or low enriched uranium. A processed "button" of enriched uranium is shown in Fig. 1. 
|Fig. 2: Pressurized Water Reactor (PWR). (Source: Wikimedia Commons, courtesy of the NRC)|
The most common type of light water reactor that is used in commercial nuclear power applications is the pressurized water reactor (PWR), as seen in Fig. 2. The PWR utilizes separate primary and secondary systems to isolate the reactor from the turbine and electric generator. Fission reactions inside the reactor heat the primary coolant at high pressures to keep the coolant from boiling. The primary coolant is pumped through the system to a steam generator, where heat is transferred to the secondary system. Operating at a lower pressure than the primary, coolant in the secondary system flashes to steam, turns through a turbine to generate mechanical energy, condenses back to liquid form, and continues to be pumped through the system. Mechanical energy from the turbine is used to turn an electric generator, which supplies electric power to the commercial energy grid. In 2014, the U.S. Energy Information Administration published that commercial nuclear energy accounts for 19% of all electricity generation in the United States. Throughout its tenure, the HEU agreement enabled the U.S. to maintain a steady supply of nuclear fuel to its commercial reactors while simultaneously working to mitigate global proliferation concerns.
The Megatons to Megawatts agreement was perhaps the most successful non-proliferation endeavor to date. In an increasingly dynamic and changing national security landscape, the reduction in the number of nuclear weapons and nuclear capable actors is paramount in ensuring global security. The HEU deal proved that countries can choose to set aside their differences in the presence of greater political and economic interests, even the U.S. and former Soviet Union. As concerns regarding the rapid consumption of fossil fuels and global climate change escalate, nuclear energy should be considered as a renewable substitute for fossil fuel energy production. Future agreements similar to the Megatons to Megawatts program can help diminish the threat of nuclear conflicts while contributing to the continual, and potentially expanding, operation of commercial nuclear power plants throughout the world.
© Christopher DiOrio. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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