Th/U-233 multi-recycle in PWRs.

Abstract

EXECUTIVE SUMMARYThe use of thorium in current or advanced light water reactors (LWRs) has been of interest in recent years. These interests have been associated with the need to increase nuclear fuel resources and the perceived non-proliferation advantages of the utilization of thorium in the fuel cycle. Various options have been considered for the use of thorium in the LWR fuel cycle including: (1) its use in a once-through fuel cycle to replace non-fissile uranium or to extend fuel burnup due to its attractive fertile material conversion, (2) its use for fissile plutonium burning in limited recycle cores, and (3) its advantage in limiting the transuranic elements to be disposed off in a repository (if only Th/U-233 fuel is used). The possibility for thorium utilization in multi-recycle system has also been considered by various researchers, primarily because of the potential for near breeders with Th/U-233 in the thermal energy range.The objective of this project is to evaluate the potential of the Th/U-233 fuel multi-recycle in current LWRs, with focus this year on pressurized water reactors (PWRs). In this work, approaches for ensuring a sustainable multi-recycle without the need for external source of makeup fissile material have been investigated. The intent is to achieve a design that allows existing PWRs to be used with minimal modifications. In all cases including homogeneous and heterogeneous assembly designs, the assembly pitch is kept consistent with that of current PWRs (21.5 cm used). Due to difficulties encountered with keeping the PWR design intact, the potential modifications (other than assembly pitch) that would be needed for PWRs to ensure a sustainable multi-recycle system have been investigated and characterized. Additionally, the implications of the use of thorium on the LWR fuel cycle are discussed.Investigations have been conducted to assess the feasibility of both homogeneous and heterogeneous PWR assemblies to achieve Th/U-233 fuel multi-recycle. The conclusions from the study are:1. A practical sustainable fuel cycle required by this study cannot be achieved with a homogeneous PWR assembly within the parameter space of initial U-233 content and reasonable moderator to fuel volume ratio (MR) obtained by varying the fuel pin size.2. A 17-by-17 heterogeneous assembly design achieved the following attributes and partially met the requirements defined in this study for sustainable Th/U-233 multi-recycle: a. A derated core power of 1000 MWt.b. A 2.7-year cycle length with sustainable fissile inventory (assuming 3-batch fuel management).c. Discharge burnup of 18 GWd/t, which is significantly lower than the burnup of current PWRs.d. The Th/U-233 system requires hard neutron spectra to support high conversion of Th-232. The neutron spectra of both the seed and the blanket region are harder compared to the standard thermal systems.e. Compared to the used nuclear fuel (UNF) of the standard PWR uranium-dioxide (UOX) fuel system, the high level waste (HLW) of the Th/U-233 multi-recycle system has...

Updated and revised neutron reaction data for 233 U

“…For the improvement of nuclear energy, 233 U is an important material in Th/U fuel cycle applications. The neutron reaction data of 233 U play an important role in the framework of studies concerning new fuel cycles and nuclear waste disposal, as well as other nuclear fields [1][2][3].…”