Advanced high-temperature reactor neutronic core design

The Advanced High-Temperature Reactor (AHTR) is a 3400 MWth fluoride-salt-cooled high-temperature class design concept intended to serve as a central generating station type power plant. This paper focuses on preliminary neutronic design studies performed at Oak Ridge National Laboratory (ORNL) during fiscal year 2011. After a brief presentation of the AHTR design concept, the paper summarizes several neutronic studies. An optimization study for the AHTR core is first presented, and a design that reaches a single-batch fuel length of just over 2 years is chosen as reference. The temperature and void coefficients of reactivity are then analyzed for a few configurations of interest, and, in all cases analyzed, the isothermal temperature coefficient is proved to be negative. A discussion of the limiting factors due to the fast neutron fluence follows. The neutronic studies conclude with a discussion of the control and shutdown options. The studies presented confirm that sound neutronic alternatives exist for the design of the AHTR to maintain full passive safety features and reasonable operation conditions. While significant technology development and demonstration remain, the basic design concept appears sound and tolerant of much of the remaining performance uncertainty. No fundamental impediments have been identified that would prevent widespread deployment of the concept.