Optimized Core Design of a Supercritical Carbon Dioxide-Cooled Fast Reactor

Abstract

Spurred by the renewed interest in nuclear power, Gas-cooled Fast Reactors (GFRs) have received increasing attention in the past decade. Motivated by the goals of the Generation-IV International Forum (GIF), a GFR cooled by supercritical carbon dioxide (S-CO 2 ), fueled with Light Water Reactor spent fuel transuranics, and directly coupled with a Brayton cycle is under investigation as part of a larger research effort at MIT. While the original GFR chosen by the GIF is a 600MWh version using Helium as a coolant, the work presented here is for a 2400 MWd, core using S-CO 2 as a coolant, which has comparable thermal efficiency (-45%) at much lower temperatures (650"C v. 850 0 C) A reactor core for use in this direct cycle S-CO 2 GFR has been designed which satisfies established neutronic and thermal-hydraulic steady state design criteria, while concurrently supporting the Gen-IV criteria of sustainability, safety, proliferation, and economics. Use of innovative Tube-in-Duct (TID) fuel has been central to accomplishing this objective, as it provides a higher fuel volume fraction and lower fuel temperatures and pressure drop when compared to traditional pin-type fuel. Further, this large fuel volume fraction allows for a large enough heavy metal loading for a sustainable core lifetime without the need for external blankets, enhancing the proliferation resistance of such an approach.Use of Beryllium Oxide (BeO) as a diluent is explored as a means for both power shaping and coolant void reactivity (CVR) reduction in fast reactors. Results show that relatively flat power profiles can be maintained throughout a batch-loaded "battery" core life using a combination of enrichment and diluent zoning, due to the slight moderating effect of the BeO. Combining BeO diluent with the innovative strategy of using a thick volume of S-CO 2 coolant as the radial reflector yields negative CVR values throughout core life, a rare, if not unique accomplishment for fast reactors. The ability to maintain negative CVR comes from a combination of the effects of spectral softening due to the BeO diluent and the enhanced leakage upon voiding of the S-CO 2 radial reflector.In support of assessing the neutronic self-controllability of this core, a simple first-order steady state design metric is developed, modified from other established methodology to suit the uniqueness of this core concept. The results of this analysis show that the core will passively shut itself down without violation of established core thermal limits in the event of several limiting Anticipated Transients Without SCRAM (ATWS) scenarios, except for a Loss of Coolant Without SCRAM at End of Core life. Since most of the requisites for passive core shutdown have been demonstrated within the parameter uncertainties of current estimates, the candidate core design is deemed sufficiently safe. Further, design solutions for fixing this deficiency are proposed.Alternative cores using traditional pin-type fuel and innovative Internally-Cooled Annular Fuel (ICAF) have also be...

ECONOMIC VIABILITY TO BeO-UO2FUEL BURNUP EXTENSION

“…According to research results at MIT (Massachusetts Institute of Technology), the relationship of a monotonic increasing function exists between beryllium content and burnup within the limit of fixed burnup when the BeO-UO2 fuel is loaded in the nuclear reactor. In other words, a linear relationship between beryllium content and burnup exists from 45 MWD/kg of burnup to 85 MWD/kg of burnup [17]. These values result from the assumption that nuclear fuel is appropriately placed in the core.…”

Supercritical CO2 direct cycle Gas Fast Reactor (SC-GFR) concept.

“…The concept offers a potential cost-effective alternative to other advanced reactors that have been proposed. Concepts similar to this have been proposed by the Massachusetts Institute of Technology (Pope, 2004;Handwerk, 2007;Pope, et al, 2009) and the Tokyo Institute of Technology (Kato, et al, 2004).…”

“…Appropriate design of emergency cooling systems could allow for effective core cooling available for long periods of time. (Weaver and Khalil, 2002), another by the Tokyo Institute of Technology (TIT) (Kato, et al, 2004), a third by the Massachusetts Institute of Technology (MIT) (Pope, 2004;Handwerk, 2007;Pope, et al, 2009), and the last by the French Commissariat a l'Energy Atomique (CEA) (Dumas, et al, 2007). A fifth paper by British Nuclear Fuels (BNFL) (Newton and Smith, 2001) was reviewed that described a GFR based on the British Advanced Gas Fast Reactor.…”

The credit analysis of recycling beryllium and uranium in BeO-UO2nuclear fuel

“…In Equation (18), the cost for each area is discounted by considering the rate of inflation and multiplying the quantity required with the unit cost [13]. For example, the uranium cost is estimated as in Equation (8). Second, when spent nuclear fuel is reprocessed, the disposal cost for radioactive waste generated in such processes is included.…”

“…According to previous work, the materials not intimately mixed are far from having high burn-up rates as a nuclear fuel [8]. Thus, the homogenizing (mixing) process is regarded as one of the important processes in BeO-UO 2 nuclear fuel fabrication.…”