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| MOX | |
|---|---|
| Name | MOX |
| Caption | Mixed oxide fuel pellet |
| Formula | Variable (PuO2 + UO2) |
| Phase | Solid |
| Density | ~10.5–11.5 g/cm³ |
| Melting point | ~2800–3000 °C (approximate) |
| Uses | Nuclear reactor fuel, plutonium disposition |
MOX is a form of nuclear fuel composed of a blend of plutonium dioxide and uranium dioxide used in thermal and fast reactors. Developed to utilize surplus plutonium from weapons programs and spent nuclear fuel, MOX has been adopted by utilities, research institutions, and governments to extend uranium resources and to manage fissile materials from disarmament agreements. Its deployment involves complex interactions among reactor vendors, national laboratories, regulatory bodies, and international organizations.
MOX emerged from collaborations among entities such as CEA (French Alternative Energies and Atomic Energy Commission), BNFL, Westinghouse Electric Company, AREVA (now Framatome), and national laboratories including Los Alamos National Laboratory and Idaho National Laboratory. Early programs linked to treaties and initiatives like the Strategic Arms Reduction Treaty and the Plutonium Management and Disposition Agreement shaped large-scale plans in countries including France, United Kingdom, Russia, United States, Japan, and Germany. Reactor designs by vendors such as AREVA, Westinghouse, General Electric, and Siemens were adapted to accept MOX fuel assemblies in commercial plants like Koeberg Nuclear Power Station, Takahama Nuclear Power Plant, and Koeberg-type reactors. Research institutions such as Argonne National Laboratory and universities including Imperial College London and Tsinghua University have published studies on irradiation behavior, thermal properties, and neutronics.
MOX fuel typically contains plutonium oxide (PuO2) blended with uranium oxide (UO2) with plutonium fractions ranging from a few percent up to ~10–12% by weight, tailored to reactor type and core design. Production facilities and projects include plants at Sellafield, Cadarache, Rokkasho Reprocessing Plant, La Hague, and the former Hanford Site. Fabrication methods involve powder blending, pellet pressing, sintering, and assembly fabrication in gloveboxes under stringent safeguards overseen by agencies like the International Atomic Energy Agency and national regulators such as the Nuclear Regulatory Commission. Feedstock plutonium can originate from spent fuel reprocessing campaigns by companies like Cogema and remnant material from demilitarization programs coordinated among Department of Energy (United States), Ministry of Defence (United Kingdom), and Rosatom. Advanced concepts investigate incorporation of depleted uranium from enrichment facilities such as Eurodif and Centrifuge Technology into MOX matrices.
MOX is used in light-water reactors (LWRs), pressurized water reactors (PWRs), boiling water reactors (BWRs), and fast neutron reactors including prototypes developed at BN-600, BN-800, and experimental facilities such as Phénix and Superphénix. Utilities including Électricité de France and operators like Tokyo Electric Power Company have irradiated MOX assemblies for plutonium disposition and fuel diversification. In reactor cores, MOX modifies neutron spectra and reactivity coefficients; analytical models from organizations such as OECD Nuclear Energy Agency and World Nuclear Association provide benchmark data. Fast reactor programs in France, Russia, and Japan aim to employ MOX-like fuels for closed fuel cycle strategies and to transmute long-lived actinides, linking research to facilities like Monju and international projects coordinated under GIF (Generation IV International Forum).
Safety assessments for MOX involve criticality control, radiological inventory evaluations, and thermal-hydraulic analyses overseen by authorities such as Office for Nuclear Regulation (UK), Nuclear Regulation Authority (Japan), and Autorité de sûreté nucléaire (France). High plutonium content impacts dose coefficients and post-accident source terms considered in studies by Sandia National Laboratories and Paul Scherrer Institute. Environmental considerations include lifecycle analyses comparing MOX recycling to direct disposal pathways, with input from organizations like European Commission research programs and United Nations Scientific Committee on the Effects of Atomic Radiation. Decommissioning and waste streams interact with repositories such as facilities evaluated under programs like Onkalo (Finland) and national radioactive waste agencies including Nagra (Switzerland).
Economic viability of MOX is influenced by uranium market prices, enrichment capacity from operators like Urenco Group, fabrication costs at plants like Capenhurst, and policy incentives under treaties including the Non-Proliferation Treaty. Cost-benefit analyses by entities such as International Energy Agency and consulting groups like Nuclear Energy Institute compare MOX recycling with once-through cycles. Political decisions in countries like Germany, Sweden, Belgium, and Spain have alternately supported or restricted MOX deployment due to public opinion, regulatory rulings, and budgetary constraints, with strategic inputs from ministries such as Ministry of Economy and Finance (France) and Ministry of Trade and Industry (Japan).
Transport of MOX fuel is regulated under frameworks managed by International Maritime Organization, International Civil Aviation Organization, and national agencies including Federal Motor Carrier Safety Administration-equivalent bodies. Casks designed by firms like Holtec International and Transnuclear meet standards by International Atomic Energy Agency for shielding, criticality safety, and thermal performance. Storage solutions encompass reactor spent fuel pools, dry cask systems deployed by utilities such as Entergy and interim facilities like Centrale de La Hague's holdings; long-term options interface with national disposal plans exemplified by Yucca Mountain (project) debates and Scandinavian repository programs.
International governance of MOX involves safeguards and monitoring by the International Atomic Energy Agency, export controls under arrangements like the Nuclear Suppliers Group, and bilateral agreements reflected in pacts between United States and Russian Federation on plutonium disposition. Non-proliferation policy discussions engage institutions including Council on Foreign Relations, Carnegie Endowment for International Peace, and legal instruments such as conventions negotiated at the United Nations. Multinational projects and technology transfers have been conducted under cooperative frameworks linking national agencies like DEN (Japan), CEA (France), and DOE (United States), while commercial deployments remain subject to national licensing by bodies such as ONR (UK) and judicial review in courts of countries like Germany and Japan.
Category:Nuclear fuel