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SummaryPNNL has proposed the Atoms for Peace Reactor (AFPR-100) concept as a 100 MWe, inherently safe, proliferation-resistant reactor that would be ideal for deployment to nations with emerging economies that decide to select nuclear power for the generation of carbon-free electricity. The basic concept of the AFPR is a water-cooled fixed particle bed, randomly packed with spherical fuel elements. The cylindrical core is approximately 3 m in height and 3 m in diameter, and consists of a series of four annular rings containing the spherical fuel elements. The reactor core is cooled by single-phase water flow within the particle bed at such a low rate that the bed will not fluidize. The concept incorporates a 20+ year core life requirement to enhance the proliferation resistance attribute associated with reactor. The ability to achieve an ultra long core life greatly reduces the need to handle fresh and spent fuel on site during the life of a plant, which in turn will greatly simplify safeguards oversight and the associated cost.The concept relies heavily on the use of existing technology which is one advantage over other small reactor concepts currently being pursued. The ultra long core life is achieved by an innovative new spherical cermet fuel element, which relies on the use of common fuels, materials, and fabrication techniques, albeit in a somewhat novel way. The design of this new innovative fuel is the subject of this report. The feasibility of fabricating such a fuel will be discussed in a later report.The new spherical cermet fuel consists of coated UO 2 kernels embedded in a zirconium, or zirconium hydride, matrix which is then overcoated with a protective outer fuel-free layer as shown. The spherical cermet fuel elements are envisioned to be 10-15 mm in diameter. The spherical cermet fuel element provides structural stability over a service life of about 20 years and appears to be fabricable with existing technology. In general, the spherical fuel cermet fuel elements offer the following advantages over existing rodded fuel technology:• high thermal conductivity, • low fuel temperatures, • good fission product retention, and • good performance at high burnup.Analyses of reactor physics performance parameters show that the spherical cermet fuel elements enable long core lifetime, easily-tailored power distribution, and attractive spent fuel isotopic composition. A fresh fuel enrichment of 12% provides sufficient initial reactivity to maintain criticality for at least 20 years of operation without refueling. The low fuel temperatures allow for higher burnup to be achieved due to reduced fission gas release and corrosion of the outer protective layer. The fuel average burnup for iv the core over a 20 year period is about 53 GWD/MTU. A fuel free coating layer made of Zr (or Zr-base alloys such as Zr-1Nb) was selected to ensure good performance over a 20 year lifetime. The resultant plutonium isotopic composition is similar to that contained in commercial light water reactor spent fuel.Evaluation of therm...

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