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Nagata, Takemitsu

Saikuru Kiko Giho, (28), p.80 - 84, 2005/09

https://jopss.jaea.go.jp/search/servlet/search?4017546

no abstracts in English

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Nagata, Takemitsu

Saikuru Kiko Giho, (28), p.95 - 98, 2005/09

https://rdreview.jaea.go.jp/gihou/pdf3/n28-17.pdf

ACROSS (Accurately Controlled Routinely Operated Signal System) is a method to investigate any change of physical state in the Earth's interior using accurately controlled seismic ans/or electromagnetic sources. We preliminary obtained Pg, Sg, and possible plate boundary reflected PxP phase using one-moth long stacking data up to nearly 70 km distance. The seismic reflection experiment across the central Japan revealed the strong PxP reflection phase from 30-40 km deep of the Philippine Sea Plate boundary around the Tokai Region, Japan (Iidaka et al., 2003). The same seismic exploration line crossed the area where many active faults distribute. One of the big issues for revealing the loading process for active faults is to examine the process in the lower crust around active faults. To examine the seismic exploration records obtained by Iidaka et al. (2003), we noticed the presence of strong phases, which can be explained as PxP reflection from the plane at 20 km deep around the Atera fault, which is one of the most active faults in Japan. The phases are identified by a number of explosions on the survey line from north to south of this region. One of high possibilities for the 20km reflector is the detachment in the lower crust. The high velocity contrast can explain such PxP reflection phase. We evaluated the possibility to observe such phase by the ACROSS transmission from the present source located in Toki city and may conclude to be able to observe such phase and its temporal change, if the seismometers are placed 50-100km distance north of this region. We also generated synthetic seismograms to confirm the detection. In addition to seismic ACROSS, electrometric ACROSS method may identify the strong-reflection source and its temporal change using resistively analysis around the Tokai Region, Japan. This approach can give high possibility to watch the change of physical state beneath the active faults and it may contribute for the earthquake forecasting.

Thermal-hydraulic investigation on core and fuel assembly of severaI fast reactor design concepts

Ohshima, Hiroyuki; ; *; *

JNC TN9400 2001-111, 192 Pages, 2001/09

JNC-TN9400-2001-111.pdf:10.04MB

The feasibility study (Phase I) has been carried out at JNC to build up new design concepts of commercialized fast reactors from the viewpoint of economy, safety, effective use of resources, reduction of environmental burden and nuclear non-proliferation. This report describes the results of the investigation related to core/fuel-assembly thermal-hydraulics that was performed in fiscal 2000 as a part of the feasibility study. A numerical analysis method was developed for the coated-particle-type fuel assembly in the helium-gas-cooled fast reactor and a parametric study was performed using it. It revealed that with proper form pressure losses at inlet and outlet surfaces of the fuel region it is possible to control flow distribution under the rated power operation condition and that the decay heat removal may fail if the natural circulation is driven only by heat generation in the fuel region. A detailed numerical analysis of local fuel region was also carried out. The characteristics of coolant flow/temperature fields, particle-surface temperature distribution and the maximum temperature in the fuel particle were grasped and the applicability of the pressure drop correlation to such porous media was onfirmed. A subchannel analysis code ASFRE was applied to calculations of flow and temperature fields in a fuel assembly with inner duct in sodium cooled reactors, which is examined for re-criticality elimination. The calculation results showed that the peak coolant temperature was higher than that of the normal fuel assembly (without inner duct) under the same power-to-flow ratio condition and its temperature difference becomes much larger as the number of fuel pins decreases.The same tendency was observed in the case of lateral skew power profile in the fuel assembly.In this case, the difference of the peak temperatures between fuel assemblies with/without inner duct is almost proportional to the peaking factor. A parametric analysis was carried out for an ...

Thermal-hydraulic of partially blocked fuel subassembly with porous media

; Ohshima, Hiroyuki; Yamaguchi, Akira

JNC TN9400 2001-019, 97 Pages, 2000/10

JNC-TN9400-2001-019.pdf:3.73MB

The analysis code for investigations of local subassembly phenomena, which has been recognized as an issue of local subassembly accidents, has been required and developed at JNC. It is desirable for the analysis code to be applicable to various blockage conditions and random position of the blockage formation and to evaluate conservatively on the safety assessment with high accuracy, In this study, for the purpose of verifying the application and issues of the subchannel analysis code ASFRE-IV which evaluates thermal hydraulic phenomena in the porous blockage regions, the ASFRE-IV validation analysis was carried out on the basis of the data of an experiment investigation on a local porous blockage in a fuel subassembly performed by Reactor Engineering Groop, O-arai Engineering Center, JNC. Calculational results indicated that ASFRE-IV could reproduce the coolant temperature profile in a fuel subassembly and the peak temperature in the local subchannel conservatively.

Thermal-Hydraulic investigation on severaI fast reactor design concepts

Ohshima, Hiroyuki; Sakai, Takaaki; ; Yamaguchi, Akira; Nishi, Yoshihisa*; Ueda, Nobuyuki*; *

JNC TN9400 2000-077, 223 Pages, 1999/05

JNC-TN9400-2000-077.pdf:6.24MB

The feasibility study (Phase l) is being carried out at JNC to build up new design concepts of practical fast reactors (FRs) from the viewpoint of economy, safety, effective use of resources, reduction of environmental burden and non-proliferation. This report describes the results of the investigation, related to decay heat removal, core/fuel-assembly thermal-hydraulics and thermal-hydraulic correlations, that was performed in fiscal l999 as a part of the feasibility study. ln the study of the decay heat removal, the effects of several design parameters on the performance of the reactor vessel auxiliary cooling system (RVACS) in a middle-scale sodium-cooled FR were clarified by using a plant dynamic analysis code. The upper limit of RVACS performance was preliminarily estimated at approximately 0.50.6 MWe. Numerical methods for the plant dynamic analysis of gas-and heavy-metal-cooled FRs were also developed. They were applied to the preliminary calculations of the transition from scram to natural circulation and the transient characteristics in tentative plant design concepts were clarified. ln addition, a dimensionless number indicating natural circulation performance was deduced for the comparison of several plant design concepts. With respect to the core/fuel-assembly thermal-hydraulics, numerical analysis methods were improved for the pin-type fuel assembly of gas-and heavy-metal-cooled FRs, the coated-particle- type fuel assembly of helium-gas-cooled FR, and the ductless core of sodium-and heavy-metal-cooled FRs. As preliminary evaluations, thermal-hydraulics in the heavy-metal-cooled FR fuel assembly was compared with sodium-cooled one and thermal-hydraulic analyses of carbon-dioxide- and helium-gas-cooled FR fuel assemblies were performed. The analysis for the fuel assembly with inside duct of sodium-cooled FR was also carried out. The correlations of pressure loss and heat transfer coefficient were investigated for the thermal-hydraulic ...