Numerical analysis of unsteady phenomena in upper plenum and hot-leg piping system of advanced loop-type sodium cooled fast reactor

Takaya, Shigeru; Fujisaki, Tatsuya*; Tanaka, Masaaki

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 5 Pages, 2016/07

https://doi.org/10.1115/PVP2016-63845

JAEA is conducting R&D of an advanced loop-type sodium cooled fast reactor. The cooling system is planned to be simplified by employing a two-loop configuration and shortened piping with less elbows than Monju in order to reduce construction costs. The design increases flow velocity in the hot-leg piping and induces large flow turbulence around elbows. Therefore, flow-induced vibration is one of main concerns. The flow field in the hot-leg piping is affected by flow disturbance at the inlet, so it is important to evaluate flow field including the upper plenum. In this study, we analyzed unsteady fluid flow by using an integrated model of the upper plenum and the hot-leg piping system. Unsteady Reynolds averaged Navier-Stokes simulation with Reynolds stress model was used. In general, the simulation results obtained by using the integrated model show a similar tendency with the experiment results of 1/3 scaled-model of hot-leg piping with deflect flows. The coupling effect of swirling and deflected flows seems to be not significant although further investigation is needed.

Experimental Study on Thermalhydraulics in Thermal Striping Phenomena; Comparison of Temperature Fluctuations between Sodium and Water

Kimura, Nobuyuki; Miyake, Yasuhiro*; Miyakoshi, Hiroyuki; Nagasawa, Kazuyoshi*; Igarashi, Minoru; Kamide, Hideki

JNC TN9400 2003-077, 96 Pages, 2003/06

JNC-TN9400-2003-077.pdf:3.96MB

A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for structural integrity and reactor safety.Thermal conductivity of sodium is approximately 100 times larger than that of water. Thus, temperature fluctuation characteristics will be different between sodium, which is used as a coolant of a fast reactor, and water, which is used in general industries. In this study, a comparison of convective mixing among jets was performed in parallel triple wall jets with the same geometries between sodium and water. The discharged velocity in the sodium experiment was experimental parameter and set at the same velocity and the same Reynolds number in comparison with the water experiment. And also, the velocity ratio among the triple jets was varied to change flow pattern. It was seen that the water jets were mixed in slightly closer region to the nozzle than in sodium jets. As for the power spectrum densities (PSD) of temperature fluctuation, the PSD of sodium was similar to the PSD of water under the same discharged velocity condition. At the neighborhood of the wall, the lower frequency component in the PSD of sodium decreased in comparison with the PSD of water. It was shown that the amplitude and frequency characteristics obtained by rain-flow method, which was important to evaluate structural damage by the thermal fatigue, were identical between sodium and water overall. These experimental results show that water experiment could simulate the frequency and the amplitude in temperature fluctuation characteristics in the sodium cooled reactor.

Experimental study on thermal striping; Sodium experiment of paranel triple jets

Kimura, Nobuyuki; ; Miyake, Yasuhiro*; ; Kamide, Hideki

JNC TN9400 2001-063, 338 Pages, 2001/03

JNC-TN9400-2001-063.pdf:12.28MB

A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing among jets causes thermal fatigue in structural components, is of importance for reactor safety. It is necessary for quantity of thermal striping phenomena to evaluate occurrence of temperature fluctuation, decay of temperature fluctuation near structures and transfer of temperature fluctuation from fluid to structures. The structural safety is clarified, based on the above information. In this study, a sodium experiment of parallel triple jets configuration was performed in order to evaluate temperature fluctuation characteristics in fluid, tansfer characteristics of temperature fluctuation from fluid to structure and toward inner structure. As for the experimental geometry, a cold jet on center and hot jets on both sides flowed vertically and along the wall. The temperature fluctuation intensity near the wall decreased as the discharged velocity of the jet decreased. The power spectrum density of the temperature fluctuation could be evaluated using Strouhal number based on the discharged velocities of the jets. In this experiment, the temperature fluctuation characteristics were independent of the discharged temperature difference of the jets and the bulk temperature. The temperature fluctuation intensity at the neighborhood of the wall decreased approximate 0.8 times in comparison to that at the furthest position from the wall. The temperature fluctuation in the structure could be predicted by the non-stationary heat conduction equation. Thus, the temperature fluctuation characteristics on the structural surface were predicted based on the measured data in the structure. The decay rate of the temperature fluctuation from the fluid to the structure decreased as the frequency of the temperature fluctuation increased. And the decay rate decreased as the discharged velocity increased. The phase delay of the temperature fluctuation, in which the temperature ...