Nuclear energy has proven to be a clean, carbon free source of energy. Nuclear energy is produced in nuclear reactors where the heat from nuclear fission is captured and converted to electric energy. In the US, the most common type of reactor is the Light Water Reactors (LWR). LWRs use ordinary water as a coolant and also to moderate the nuclear fission. Boiling water reactors and pressurized water reactors are also types of LWRs. Majority of the LWRs use Uranium-235 as an input fuel. There are other reactors that can use a mix of Uranium and Plutonium as a fuel these reactors are called Mixed Oxide Reactors (MOX).
Nuclear reactors can also be broadly classified into open loop fuel cycle and closed loop fuel cycle reactors when classified based on their fuel cycles.
Open Loop Fuel Cycle – Open loop fuel cycle based nuclear reactors use Uranium for nuclear fission reaction only once and once the fuel is used up the spent fuel is stored in interim storage. The spent fuel usually contains a potent concentration of plutonium and uranium and is usually stored in the form of wet or dry storage.
Open fuel reactors are less expensive and are less complex to construct, operate and maintain. As a result they pose a lesser risk to user errros and equipment malfunctions. On the other hand, open cycle nuclear reactors produce nuclear wastes that contain about 93% of Uranium 238 and about 1% of Plutonium that are radioactively potent and hence require nuclear storage that is monitored and is safe for a long time. Also, reuse of uranium and plutonium may be a better option considering that their global prices are increasing.
Closed Loop Fuel Cycle – Closed loop fuel cycle based nuclear reactors reprocess the spent fuel and reuse the spent fuel in the same reactor or a different reactor in a closed loop. Spent fuel generated out of a nuclear fission reaction mostly contains plutonium and uranium and some elements that are not useful for further power production. The plutonium and uranium are recycled in a closed loop nuclear reactor and hence high level nuclear waste is generated that contains materials with smaller half-lives.
Closed loop reactors tend to have very high level of efficiency because of re-use of spent fuel. As a result, the cost of fuel is less expensive. The quantities of high level radioactive wastes are minimized and provide options for improved waste management. On the other hand, closed loop reactors tend to be more complicated than open loop reactors because of the additional reprocessing facilities that are required. This would also result in higher expenses for construction and maintainence and a higher risk of malfunction or user errors. Finally, reprocessing technologies have a risk of proliferation because of the purification process where plutonium can be enriched to weapon grade plutonium.
Past presidents viz. President Ford, President Carter and President Clinton have expressed oppositions to commertial reprocessing on the grounds that nuclear reprocessing poses a high risk of proliferration. President Carter put an end to commertial reprocessing when he vetod ERDA Authorization Act of 1978. Investors who had invested in the Barnwell plant lost their investment and after that there was no push towards reprocessing either from policy or the industry.
President Reagan lifted the ban on commertial reprocessing in 1981 however there was no investment in reprocessing facilities or research. In the meantime, countries like France, Japan, Russia and the UK have built reprocessing plants for reuse of nuclear wastes. In 2006, DOE started an Advanced Fuel Cycle Initiative program to demonstrate proliferation resistant reprocessing of plutonium. A consortium of four companies were awarded grants by the DOE for research and development of proliferation resistant reprocessing facilities.
In 2009, the DOE stated that Alternative Fuel Cycles, like the Closed Loop Fuel cycle, posses significant advantages in terms of efficient waste management, higher fuel efficiency and lower exposure towards raising Uranium prices. However, it has also stated that further research is required towards plutonium reprocessing that is resistant towards proliferation. A study by MIT in 2011 stated that, at current Uranium prices, it is not economically viable to convert existing facilities to Closed Loop Fuel Cycles. However, it has recommended that efficiency of existing Open Loop reactors should be increased. It has also stated that further R&D is required for waste management and full closed loop reactors.
From DOE’s statements and from 3rd party reports and analyses, it can be concluded that the status quo will be maintained for nuclear fuel cycles in the US. Further research will be funded and conducted for alternate fuel cycles, waste management and proliferation resistant reprocessing of plutonium.
NRC : Backgrounder on MOX Reactors (http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/mox-bg.html)
Alice Clamp, “Toward an Integrated Fuel Cycle”, 2008 (http://mydocs.epri.com/docs/CorporateDocuments/EPRI_Journal/2008-Spring/1016422_NuclearFuelCycle.pdf)
The IEEE, “Nuclear Reactor Types”, 2005 (http://www.carnegieendowment.org/static/npp/reports/nuclear_reactors.pdf)
Buzz Savage, Office of Nuclear Energy, US DOE, “DOE Perspective on Advanced Nuclear Fuel Cycles”, 2009 (http://www.nrc.gov/public-involve/conference-symposia/ric/past/2009/slides/presentations/wed-1230-200-nuclear-fuel-cycle-update/presentation-format/nmss-savage-slides.ppt)
Luis Reyes, US DOE, “Regulatory and Resource Implications of a Department of Energy spent Nuclear Fuel Recycling Program”, 2006
MIT, “The Future of Nuclear Fuel Cycle – An Interdisciplinary MIT Study”, April 2011
Anthony Andrews, “Nuclear Fuel Reprocessing : US Policy Development”, CRS Report for Congress, Congressional Research Service, Library of Congress, 2008 (http://www.fas.org/sgp/crs/nuke/RS22542.pdf)