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Article Citation - WoS: 13Citation - Scopus: 14Utilization of Nuclear Waste Plutonium and Thorium Mixed Fuel in Candu Reactors(Wiley, 2016) Sahin, Sumer; Sarer, Basar; Celik, YurdunazSpent nuclear fuel out of conventional light water reactors contains significant amount of even plutonium isotopes, so called reactor grade plutonium. Excellent neutron economy of Canada deuterium uranium (CANDU) reactors can further burn reactor grade plutonium, which has been used as a booster fissile fuel material in form of mixed ThO2/ PuO2 fuel in a CANDU fuel bundle in order to assure reactor criticality. The paper investigates incineration of nuclear waste and the prospects of exploitation of rich world thorium reserves in CANDU reactors. In the present work, the criticality calculations have been performed with 3-D geometrical modeling of a CANDU reactor, where the structure of all fuel rods and bundles is represented individually. In the course of time calculations, nuclear transformation and radioactive decay of all actinide elements as well as fission products are considered. Four different fuel compositions have been selected for investigations: 95% thoria (ThO2) + 5% PuO2,. 90% ThO2 + 10% PuO2,. 85% ThO2 + 15% PuO2 and. 80% ThO2 + 20% PuO2. The latter is used for the purpose of denaturing the new U-233 fuel with U-238. The behavior of the criticality k8 and the burnup values of the reactor have been pursued by full power operation for similar to 10 years. Among the investigated four modes, 90% ThO2 + 10% PuO2 seems a reasonable choice. This mixed fuel would continue make possible extensive exploitation of thorium resources with respect to reactor criticality. Reactor will run with the same fuel charge for similar to 7 years and allow a fuel burnup similar to 55 GWd/ t. Copyright (C) 2016 John Wiley & Sons, Ltd.Article Citation - WoS: 3Citation - Scopus: 6Reactivity and Kinetic Parameter Evolutions for the Core Height and Boron Concentration of the Fixed Bed Nuclear Reactor(Wiley, 2018) Ha Van Thong; Do Thi Nguyet Minh; Sahin, Sumer; Truong Huy Hoang; Sefidvash, FarhangThis article focuses on calculation of reactivity and kinetic parameters in different states (different core heights and boron concentrations in the coolant water) of the fixed bed nuclear reactor (FBNR). The numerical calculations are performed with the SRAC code. Uranium dioxide (UO2) with U-235 enrichment grade of 5% is used as spherical fuel pellets in the TRISO fuel type. The core height is changed by a core height level limiter. The main results of this study can be summarized as follows: The effective neutron multiplication coefficient is varied with the core height and boron concentration in the coolant water. When there is no-boron in the coolant water and the core height is over 120 cm, the reactor control can be carried out by the movement of a core height level limiter, without the fine control rods in the core center; but when there is a boron concentration, the reactor may be controlled by the level limiter at the lower core heights. The kinetic parameters (the prompt-neutron lifetime and effective delayed neutron fraction) of the reactor also are changed to the reactor core height and to the boron concentration in the coolant water. Copyright (c) 2016 John Wiley & Sons, Ltd.
