Thorium fuel cycle : potential benefits and challenges

In this paper the authors review 25 original Small and Medium sized Reactor designs currently under development, licensing procedure or in operation. Technology overview, safety features and ability to mitigate proliferation are considered. In order to show common research trends and highlight the features of particular designs the authors choose to classify the reactors according to used technology and cooling medium. The main requirement for a new reactor design is to secure inherent and passive safety features, thus different ways to achieve it are shown. The Pressurized Water Reactor (PWR) is the most advanced and most commonly used technology. In PWR, passiveness and inherency of safety features are ensured by integrating steam generators inside the Reactor Pressure Vessel (RPV). It eliminates possibility of Loss of Cooling Accident (LOCA); moreover the technology allows swift removal of heat produced during normal or accidental conditions. Heavy Water Reactors (HWRs) are also in operation, however, the design process of improving emergency cooling system is ongoing. The design of Supercritical Water Reactor (SCWR) based on Canadian HWR is reviewed including the ongoing development in novel leakage detection method and material improvement. Liquid Metal Cooled Reactors (LMCR) are in advanced stage of research and development focusing on lead and sodium as the coolants. LMCR are secured from LOCA accidents due to low operating pressure and integration of the most elements in RPV. In case of Advanced Gas-Cooled Reactors (AGCR) the literature indicates several possible system integrations related to high operating temperature under development. AGCRs are able to use fully passive systems during all events due to their low power density. Furthermore, it is noted that the use of innovative reactor designs can mitigate proliferation concerns to an acceptable level. The authors identify the common research trend among all designs as the fuel cycle evaluation and optimization.

Small and Medium sized Reactors (SMR): A review of technology

Increased fuel burn up in a CANDU thorium reactor using weapon grade plutonium

Feasibility study for the plutonium denaturing by utilizing minor-actinide transmutation in light water reactors has been performed. And the intrinsic feature of proliferation resistance of plutonium has been discussed based on IAEA's publication and Kessler's proposal. The analytical results show that not only 238Pu but also other plutonium isotopes with even-mass-number have very important role for denaturing of plutonium due to their relatively large critical mass and noticeably high spontaneous fission neutron generation. With the changes of the minor-actinide doping ratio in U—Pu mix oxide fuel and moderator to fuel ratio, it is found that the reactor-grade plutonium from conventional light water reactors can be denatured to satisfy the proliferation resistance criterion based on the Kessler's proposal but not to be sufficient for the criterion based on IAEA's publication. It has been also confirmed that all the safety coefficients take negative value throughout the irradiation.

https://www.tandfonline.com/doi/pdf/10.1080/18811248.2005.9726376

Denaturing of Plutonium by Transmutation of Minor-Actinides for Enhancement of Proliferation Resistance

Performance of the Gas Turbine – Modular Helium Reactor fuelled with different types of fertile TRISO particles

Neutronic features of the GT-MHR reactor

GT-MHR project high-temperature reactor neutronic issues and ways to resolve them

The GT-MHR reactor core is characterized by flexibility of neutronic characteristics at the given average power density and fixed geometrical dimensions of reactor core. Such flexibility makes it possible to start the reactor operation with one fuel cycle, and then to turn to another type of core fuel load without changes of main reactor elements: fuel block design, core and reflector size, control rod number etc. Preliminary analysis re-indicates the commercial viability of the GT-MHR, part of which is due to the ability to accommodate different fuel types and cycles. This paper presents the results of studies of the neutronic characteristics of reactor cores using different fuel (low- and high-enriched uranium, MOX fuel). Comparison of different fuel cycles is carried out for a three-batch refueling option with respect to following characteristics: discharged fuel burnup, reactivity change during one partial cycle of fuel burnup, consumption of fissile isotopes per unit of produced energy, power distribution, reactivity effects, control rods worth. It is shown, that the considered options of fuel loads provide the three-year fuel campaign (with accounting of capacity factor {approx} 0,8) without change of core design, number and design of control rods at transition from the one fuel type tomore » another. (authors)« less

Yu.P. Sukharev

Papers

Neutronic features of the GT-MHR reactor

GT-MHR project high-temperature reactor neutronic issues and ways to resolve them

Possibility of Different Fuel Cycles Usage in GT-MHR