Study on reactor vessel coolability of sodium-cooled fast reactor under severe accident condition; Water experiments using a scale model

Ono, Ayako; Kurihara, Akikazu; Tanaka, Masaaki; Ohshima, Hiroyuki; Kamide, Hideki; Miyake, Yasuhiro*; Ito, Masami*; Nakane, Shigeru*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 10 Pages, 2017/04

The water experiment apparatus simulating the thermal hydraulics in a reactor vessel under operating the decay heat removal systems (DHRSs) was fabricated. The theoretical evaluation for similarity and results of basic experiments show applicability for a scale model experiment of a sodium-cooled fast reactor. This paper, moreover, describes the results of flow visualization experiment under operating a dipped-type passive DHX, which is planned to be installed in both a loop type reactor and pool type reactor, and the calculation results using FLUENT comparing with the result of water experiment.

Evaluation on gas entrainment in reactor vessel using 1/1.8th scaled model; Investigation on dominant factors based on occurrence map and mechanism for gas entrainment

Kimura, Nobuyuki; Ezure, Toshiki; Tobita, Akira; Ito, Masami*; Kamide, Hideki

JAEA-Research 2006-068, 56 Pages, 2006/10

JAEA-Research-2006-068.pdf:23.42MB

For an innovative sodium cooled fast reactor, a compact reactor vessel is designed to reduce the construction cost, where sodium flow velocity increases. One of the thermal hydraulic issues in this design is gas entrainment (GE) at free surface in the reactor vessel (R/V). Dipped plates (D/P) are set below the free surface in order to prevent the GE. To evaluate GE, we made the partial apparatus modeled the 90 degree sector of the R/V with a central focus on the hot leg (H/L) pipe circumferentially and region above the D/Ps vertically. We obtained an occurrence map of the GE in order to evaluate the dominant factor for the GE. In the map, it was found that there were two kinds of the GE phenomena. One of the GE occurred at the downstream region of the cold leg pipe. Other one broke out at the region between the H/L pipe and the R/V wall. The mechanisms of the GE at the two regions were clarified by applying the PIV.

Water experiment on gas entrainment in reactor vessel using 1/1.8th scaled model; Evaluation of onset condition and mechanism

Kimura, Nobuyuki; Ezure, Toshiki; Nakayama, Okatsu; Tobita, Akira; Ito, Masami*; Kamide, Hideki

JAEA-Research 2006-005, 45 Pages, 2006/03

JAEA-Research-2006-005.pdf:15.66MB

An innovative sodium cooled fast reactor has been investigated in a frame work of the FBR feasibility study. One of the thermal hydraulic issues in this design is gas entrainment at free surface in the reactor vessel. Dipped plates (D/P) are set below the free surface in order to prevent the gas entrainment. We performed an 1/10th scaled model water experiment for the upper plenum of reactor vessel and flow optimization was done to reduce flow velocity near the free surface. However, previous studies showed that the gas entrainment depends on model scale. Then an 1/1.8th scaled model was also planned to confirm the phenomena in an enough large model. As a test section, 90 degree sector and region between the free surface and the D/P was modeled by 1/1.8th scale. Boundary conditions at D/P gaps and radial cross sections of sector ends were obtained by the 1/10th scaled full sector model. The gas entrainment was not observed in the model under the velocity condition of reactor full power operation at water levels higher than 3% of the normal height from the D/P in the case of double D/Ps geometry (current design). As for the case of single D/P geometry, it was found by the visualization and the velocity measurement that the gas entrainment occurred as the circumferential velocity increased at the water level higher than 50% of the normal height condition. It is shown that the gas entrainment in the reactor vessel will be eliminated in the current design approach.

Hydraulic Experiment on Flow Optimization in Compact Reactor Vessel; Effects of double dipped plates and outer shell of UIS

Nakayama, Oukatsu; Kimura, Nobuyuki; Kamide, Hideki; Ito, Masami*; Sekine, Tadashi*

JNC TN9400 2005-032, 103 Pages, 2005/03

JNC-TN9400-2005-032.pdf:33.44MB

On the FBR feasibility study, an innovative sodium cooled fast reactor has been investigated in Japan Nuclear Cycle Development Institute. In order to reduce the construction cost of reactor, the compact reactor vessel is designed. Gas entrainment at the free surface is one of issues to be solved because of high velocity in the upper plenum vessel. We performed an 1/10th scaled model water experiment for the upper plenum of reactor vessel and investigated flow fields in the plenum in order to optimize flow. In the last experiment, we established flow optimization structures for reduction of flow toward to the free surface and restraint on the vortex cavitations near H/L inlet, i.e., plug into the dipped plate hole to install a fuel handling mechanism (FHM) and a flow splitter at vessel wall. In this report, effects of double dipped plates (D/Ps) and outer shell of upper inner structure (UIS) are investigated. In the result, we could confirm that the double D/P structure set below the free surface is effective to reduce flow toward the free surface between reactor vessel wall and guide tube of fuel transfer machine. An FHM plug, which has a step structure at mid height between double D/Ps, showed that it reduced flow velocity through the gap between the plug and the D/P. A perforated outer shell was set around the UIS to reduce vortex strength developed from the cold legs to the hot leg intake and also to restrain the vortex cavitation. It was shown that the onset condition of vortex cavitation at reactor vessel wall was reduced and the cavitation occurred easily. At the cold leg the onset condition of the caviation was not advanced. The flow distribution through the perforated outer shell should be optimized.

Hydraulic experiment for compact reactor vessel; Measurement of flow field and flow optimization in upper plenum

Kimura, Nobuyuki; Hayashi, Kenji; Ito, Masami*; Sekine, Tadashi*; Igarashi, Minoru; Sato, Hiroyuki; Kamide, Hideki

JNC TN9400 2003-032, 214 Pages, 2003/03

JNC-TN9400-2003-032.pdf:111.0MB

An innovative sodium cooled fast reactor has been investigated on the FBR feasibility study. The design of the reactor is undergoing in order to reduce the construction cost of the reactor. For example, thermal output is increased against the reactor size and an upper inner structure (UIS) has a slit for the arm of the fuel-handling machine to simplify the fuel exchanging system. The dipped plates (D/P) are set below the free surface to prevent gas entrainment at free surface. We performed an 1/10th scaled model water experiment for the upper plenum of reactor vessel and investigated flow fields in the plenum in order to optimize flow. In the upper plenum, all of main components were set up as well as the reactor design. In addition, the D/P has a hole in front of the slit of the UIS to insert the fuel handling machine(FHM). As the experimental parameters, the core outlet velocity was varied from the condition of the Froude number similarity to the same value as the real reactor. The local velocity was measured by the particle image velocimetry and the ultrasound Doppler velocimetry. In the experimental results, gas entrainment at the free surface was not observed in the range from the Froude number similarity condition to the same velocity condition as the real reactor. However, the free surface was bulged on a large scale in front of the UIS slit. At the neighborhood of the H/L intake, three vortex cavitations were observed. The vortex cavitations were broken out under the same cavitation coefficient condition based on the H/L velocity as that in the real reactor. A vertical rib was set on the reactor vessel wall near the H/L inlet to restrict the rotating flow at the neighborhood of the H/L. As the result, the vortex cavitation at the region between the reactor vessel wall and the H/L was supressed under the same cavitation factor condition as the real reactor. A vertical cylinder, named FHM plug, was installed to close the hole in the D/P fbr FHM.

Development of energy recognizable type gamma camera mounted on the unmanned helicopter II, 2; Field test around the Fukushima Daiichi NPP site

Shikaze, Yoshiaki; Torii, Tatsuo; Nishizawa, Yukiyasu; Yoshida, Mami*; Shimazoe, Kenji*; Jiang, J.*; Takahashi, Hiroyuki*; Kurosawa, Shunsuke*; Kamada, Kei*; Yoshikawa, Akira*; et al.

no journal, , 

no abstracts in English

Study on cooling process of decay heat removal systems in a reactor vessel of sodium-cooled fast reactor by scaled water experiments; Flow visualization experiments simulating operation of decay heat removal systems under a severe accident

Ono, Ayako; Kurihara, Akikazu; Tanaka, Masaaki; Ohshima, Hiroyuki; Miyake, Yasuhiro*; Ito, Masami*; Nakane, Shigeru*

no journal, , 

Thermal-hydraulic phenomena driven by natural circulation in a reactor vessel was investigated by using scaled model water experiments simulating a reactor vessel in order to enforce of safety and optimize design and operation of decay heat removal systems under normal operation and severe accident conditions. Through the flow visualization tests, the behavior of cold fluid from the dipped-type heat exchanger and cooling process of the core and debris in the vessel were revealed.