need to be carried out for each individual reactor, and the challenges encountered can be very different for different reactors.
U.S. REACTOR CONVERSION CASE STUDIES
The following three case studies of U.S. research reactor conversions are summarized in this chapter:
• Paul Wilson (University of Wisconsin) reported on the successful conversion of the University of Wisconsin research reactor (UWNR) (Wilson, 2011).
• Thomas Newton (Massachusetts Institute of Technology) reported on the status of conversion plans for the Massachusetts Institute of Technology Reactor (MITR) (Newton, 2011).
• David Cook (Oak Ridge National Laboratory; ORNL) reported on the status of conversion plans for the High Flux Isotope Reactor (HFIR) (Cook, 2011).
These reactors are quite different: MITR is planned to be the first research reactor to convert to using high-density uranium-molybdenum (UMo) monolithic LEU fuel and is considered to be a relatively straightforward conversion for a high-performance reactor. In contrast, HFIR is planned to be the last U.S. domestic reactor to convert to LEU fuel and is likely to pose far greater conversion challenges. Current approaches and plans for converting these reactors are described in the following sections.
University of Wisconsin Nuclear Reactor
UWNR is a 1 megawatt (MW) TRIGA pool reactor (see Chapter 1) housed on the University of Wisconsin campus in Madison, Wisconsin. Its primary mission is the training of undergraduate and graduate nuclear engineering students; however, it is also used to perform research, including irradiation for neutron activation analysis.
The reactor first went critical as a 10 kilowatt (kW) LEU-fueled reactor in 1961 and, following several power upgrades, was converted to HEU fuel in 1979. It was converted back to LEU fuel 30 years later, successfully achieving criticality in 2009. At that time, UWNR was converted from using 70 percent enriched TRIGA-FLIP (Fuel Life Improvement Program) fuel to TRIGA LEU 30/20 (30 percent uranium by weight, 20 percent enriched) fuel. The new LEU fuel is, like the previous FLIP fuel, a standard TRIGA-type