Development of a simplified seismic tomography survey system

Sugita, Yutaka; Sanada, Hiroyuki; Aizawa, Takao*; Ito, Shunichiro*

JAEA-Research 2011-043, 25 Pages, 2012/02

JAEA-Research-2011-043.pdf:3.18MB

A simplified seismic velocity survey system was developed for the repeat performance of surveys in conjunction with tunnel excavation, to monitor the various changes that occur in a rock mass around tunnels or galleries as they are excavated in the deep underground. The simplified seismic velocity survey system developed consists of a hammer to transfer seismic energy to the borehole wall and receivers installed and anchored in the borehole, and then backfilled. The hammer is operated with compressed air, necessitated by the potential presence of flammable gas such as methane. The system developed was used in the EDZ Experiment in a horizontal tunnel in the Horonobe URL. Changes in seismic velocity were monitored during and after excavation of the tunnel and the tomograms obtained are high quality. These results show that the system developed can provide the information needed to monitor the development and the variations in an EDZ.

Multi-offset VSP Survey in Area of Granite distribution

Niinuma, Iwao*; Aizawa, Takao*; Ito, Shunichiro*

JNC TJ7400 2005-042, 344 Pages, 2004/03

JNC-TJ7400-2005-042.PDF:50.98MB

A Vertical Seismic Profiling(VSP), Geophysical Logging and Borehole televiewer (BHTV) were performed in borehole 03RT-03. The objectives of this work are to obtain of the elastic wave response corresponding to fractures and fault zones in the granite, and to understand the application of VSP technique to survey continuity of fault zones or fractures in granite. The contents of this survey were presented in this report. In VSP survey, five shot points were set along the direction of borehole drilling. VSP processing and 3D imaging of seismic reflector were performed in order to obtain the continuity and directivity of fault zones or fractures. The events in seismic processing section, corresponding to fault zone or fractures in the granite, accepted by core information. The results of those processing were compared with the geological information acquired from the data of Geophysical logging and BHTV.

New small sodium leak detection system, 2; An Experiment of moving fluid ionization detector and laser leak detector in fast breeder reactor Monju

Okazaki, Koki*; Naito, Susumu*; Nakayama, Kunihiko*; Makino, Shunichiro*; Shigeyama, Musashi*; Kuwako, Akira*; Izumi, Mikio*; Ito, Jun*; Okada, Hisashi*; Muto, Keitaro

no journal, , 

In fast breeder reactor (FBR), it is important to detect a small sodium leak surely for safety. As the coolant sodium used in FBR is low pressure, a small leak occurs from a crack before a pipe breaks, therefore it is possible to detect a sodium leak so as to shutdown a reactor before a pipe completely breaks. The sodium leaking from piping of cooling system reacts with oxygen etc. including with the ambient gas to form aerosols. In the second coolant system of the prototype liquid metal FBR Monju, the ambient air around piping is drawn into radiative ionization detector (RID). When sodium aerosols are detected by RID, chemical analysis of aerosols and the viewing of the leak point are carried out, then sodium leak is confirmed. As the signal of RID depends on temperature strongly and RID detects the aerosols which do not include sodium, the improvements of RID are demanded for reliability. Moving fluid ionization detector (MID) and laser leak detector (LLD) have been developed to improve these points. MID can reduce the dependence for temperature of the signal strength, and LLD can detect sodium atoms which are included in aerosols by means of laser-induced breakdown spectroscopy. An experiment was carried out for validating sodium leak detection system with MID and LLD under real environment installed in the second coolant system of Monju. In the experiments, sodium was not leaked, and ambient air around piping of the secondary coolant system was introduced through actual sampling line and measured by MID and LLD. In addition a sodium level in the ambient air was measured by means of ion chromatography. The experiment showed that the background signals of MID and LLD were stable and low and that the sodium level due to the background of salinity (NaCl) contained in the ambient air was lower than three orders of magnitude than the sodium level for small sodium leak. The plant applicability of MID and RID was validated by this experiment.