NSE - Nuclear Science & Engineering at MIT


Annular Fuel for PWR

As of end of 2011, NRC had approved 139 power uprates, adding approximately 6,000 MWe of capacity, or 6%, to licensed US plants. In order to achieve higher levels of uprates in PWRs, the Internally and eXternally cooled Annular Fuel (IXAF) was analyzed extensively by an MIT led project that involved Westinghouse, AREVA and AECL. The study concluded that power density in a typical Westinghouse PWR core can be increased by 50%, while matching or improving the thermal margins. The IXAF assembly uses a 13x13 array, instead of Westinghouse 17x17, in the same assembly dimensions. The average fuel temperature is several hundred degrees lower in IXAF. A partial blockage of the inner annular of the fuel rods has acceptable critical heat flux margin. A higher enrichment is needed to allow for the power increase at the same fuel cycle length. The cost per kWhr of annular fuel pellets and cladding will be close to the solid fuel rods. The IXAF design is currently being evaluated through irradiation and mechanical experiments by KAERI for Korean PWR designs.


  1. P. Hejzlar and M.S. Kazimi, “Annular Fuel for High-Power-Density Pressurized Water Reactors: Motivation and Overview,” Nuclear Technology, Vol. 160, pp. 2–15, October 2007.
  2. F. Dandong, P. Hejzlar, M.S. Kazimi, “Thermal-Hydraulic design of high-power-density Annular Fuel in PWRs,” Nuclear Technology Vol. 160, October, 2007.
  3. X. Zhiwen, Y. Otsuka, P. Hejzlar, M.S. Kazimi, J. Driscoll, "High-Performance Annular Fuel Reactor Physics and Fuel Management”," Nuclear Technology, Vol. 160 No. 1, October 2007.
  4. Y. Yuan, M. S. Kazimi, P. Hejzlar, “Thermomechanical Performance of High-Power-Density Annular Fuel,” Nuclear Technology, Vol. 160(1), pp. 135–149, October 2007.
  5. Mujid S. Kazimi, Pavel Hejzlar, et al., “Evaluation of High Power Density Annular Fuel for Korean OPR-1000 Reactor: Final Report”, MIT-NFC-TR-114, March 2010.

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