Control of Chemical Forms of Tritium in FLiNaK under Low Flux Neutron Irradiation

The use of the isotopic exchange between tritium produced in molten salts and hydrogen molecules in a sweep gas has been proposed as a way of recovering tritium in a self-cooled molten salt liquid blanket system [1-3]. In the present study, rate coefficients of the isotopic exchange for molten FLiNaK (LiF-NaF-KF) have been evaluated in a series of low flux neutron irradiation experiments with an AmBe neutron source at the OKTAVIAN facility of Osaka University in Japan. Approximately 300 cm3 of FLiNaK were irradiated at 773 K in an Inconel 600 crucible, and tritium released from the free surface of FLiNaK has been swept by a pure He gas or He+H2 (0.1%) gas. The change in the amounts of soluble tritium (TF, HTO) and insoluble tritium (HT) recovered by water bubblers has been evaluated in each sweep gas to evaluate the effectiveness of the tritium recovery with the isotopic exchange

Study on Flow in the Two-Dimensional Curved Diffuser

Curved diffusers are used in pipe lines or in some fluid machineries, such as blades of impeller, a volute casing, or suction duct. The performance of the curved diffuser has a considerable effect on the energy conversion in the pipe lines or the machineries. Furthermore, the volute casing in the pumps or blowers is generally attached to the radial diffuser, so that the flow in the volute or scroll casing has usually very high complexities. The flow in the volute casing will be moderated by the combination of the single curved diffuser and the longitudinal side wall slit duct. However, the studies to the flow in the curved diffuser with the longitudinal slit, were merely conducted in the past ages. In this report, as a step of the study of the flow in the volute casing, experiments of flow in a two-dimensional curved diffuser, which has a small diverging angle and 90° turning angle, were carried out. The time average velocities and velocity fluctuations were measured using a constant temperature hot-wire or split film probe system. It is shown that the flow in the curved diffuser has velocity profiles with gradually variant gradients and attached to the outer side wall, and the profiles of velocity fluctuations have very interesting patterns concernig to the stall and the secondary flow

Tritium Release from Molten FLiNaBe under Low Flux Neutron Irradiation

Release behaviors of tritium from molten FLiNaBe (LiF–NaF–BeF2) have been examined in a series of low flux neutron irradiation experiments with an AmBe neutron source at the OKTAVIAN facility of Osaka University. Tritium released from FLiNaBe is swept by He and Ar gases, and recovered by water bubblers. The recovery rate of tritium released from 300 cm3 of FLiNaBe was 58.0 mBq/h in a steady state, and it was close to the tritium production rate of 58.0 mBq/h calculated by the MCNP6 code. The values of the overall mass transfer coefficients for tritium release from FLiNaBe were close to those for FLiNaK (LiF–NaF–KF) at 773 K. The influence of the diffusivity and the solubility of tritium on the overall mass transfer coefficients has been examined on molten FLiNaBe