抄録
The development of SuperCritical Water-cooled Reactors (SCWRs) is currently undertaken worldwide as part of the Generation-IV International Forum (GIF) initiative. SCWRs will operate at high operating temperatures and pressures: outlet temperatures up to 625℃ and pressures of 25 MPa. Since the development of SCWRs is in the conceptual-design stage, there are still various design issues that need to be addressed. The fuel-bundle configuration is not yet finalized; however, bundles with larger number of elements coupled with smaller element outside diameters seem to be preferred for use in SCWRs due to high fuel centerline temperatures. The most recent bundle designs for pressure channel SCWRs consists of 54 and 64 elements in total. The 54-element bundle has 53 heated fuelled elements (9.5-mm OD), and the 64-element bundle has 63 heated fuelled elements (9.13-mm OD). Both bundle designs have one unheated central element (20-mm OD). These new fuel bundles with Thoria fuel were analyzed. Thoria nuclear fuel, also known as Thorium dioxide (ThO_2), is currently considered as the primary choice in some SCWRs. The objective of this study is to examine the possibility of using Thoria as the nuclear fuel in SCWRs. Also, Thoria possesses a slightly higher thermal conductivity compared to that of Uranium dioxide (UO_2), which may help to decrease the fuel centerline temperature. Additionally, thorium is widely distributed in nature and is approximately three times as abundant as Uranium.
