Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2015 (Contract research)

Sanada, Yukihisa; Munakata, Masahiro; Mori, Airi; Ishizaki, Azusa; Shimada, Kazumasa; Hirouchi, Jun; Nishizawa, Yukiyasu; Urabe, Yoshimi; Nakanishi, Chika*; Yamada, Tsutomu*; et al.

JAEA-Research 2016-016, 131 Pages, 2016/10

JAEA-Research-2016-016.pdf:20.59MB

By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the East Japan earthquake and the following tsunami occurred on March 11, 2011, a large amount of radioactive materials was released from the NPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter was conducted around FDNPS. In addition, background dose rate monitoring was conducted around Sendai Nuclear Power Station. These results of the aerial radiation monitoring using the manned helicopter in the fiscal 2015 were summarized in the report.

Investigation on slit jet through upper internal structure (UIS) in highly compact vessel of sodium-cooled fast reactor

Kamide, Hideki; Aizawa, Kosuke; Oshima, Jun*; Nakayama, Okatsu*; Kasahara, Naoto

Journal of Nuclear Science and Technology, 47(9), p.810 - 819, 2010/09

https://doi.org/10.3327/jnst.47.810

Development of advanced loop type sodium cooled fast reactor is under going. An upper internal structure (UIS) has a radial slit to reduce the reactor vessel diameter. This UIS slit allows a high velocity from the core fuel subassemblies and influences the gas entrainment in the reactor vessel and also the delayed neutron precursor sampling for a failed fuel detection and location system. Then flow visualization and velocity measurements were carried out in an 1/10 scale water test model. The velocity measurement using particle image velocimetry showed that velocity in the slit region was accelerated at the heights of the UIS horizontal plates and kept higher value at the middle height of the upper plenum. Numerical simulation using a commercial CFD code was also carried out for this complex geometry of UIS to know adequate simulation method. The comparisons of velocity profiles in the UIS between the experiment and analysis showed good agreements.

Study on thermal stratification in a compact reactor vessel; Effects of Richardson number and upper plenum geometries

Nakayama, Okatsu; Ogawa, Hiroshi*; Kimura, Nobuyuki; Hayashi, Kenji; Tobita, Akira; Kamide, Hideki

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 8 Pages, 2007/04

Water experiment using an 1/10th scaled upper plenum model was carried out to investigate thermal stratification after a scram in a compact reactor, which has high velocity local flow in the upper plenum. The experiments showed that the rising speed of the stratification interface was dependent on Richardson number and the temperature gradient of the stratification interface was also influenced by the temperature difference and fluctuation. Furthermore, the temperature gradient could be reduced greatly by changing position of structure in the upper plenum.

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.

Treatment test of decontamination wastes using a pilot-scale pyrolysis furnace, 2; Heat-treatment test of phytoremediation wastes

Nakashio, Nobuyuki; Osugi, Takeshi; Iseda, Hirokatsu; Koakutsu, Takanori; Okoshi, Minoru; Tokizawa, Takayuki; Nakayama, Shinichi; Kimura, Takeshi*

no journal, , 

no abstracts in English