Shizue Furukawa

Synthesis of purified AlN nano powder by transferred type arc plasma

Nano powder of aluminium nitride (AlN) is one of the materials necessary for developing solid insulating materials with high thermal conductivities. This paper describes the results of chemical equilibrium composition calculations and the results of experiments in synthesizing AlN nano powder using transferred type arc plasma. In order to increase the AlN content in synthesized powder, ammonia was recommended as a reacting/quenching gas, to be blown into aluminium gas in a temperature range between 2000 and 2400 K. The AlN content increased by more than 99% on passing the synthesized powder through ethanol.

Macroscopic stability control experiments with phased antennas in the GAMMA10 tandem mirror

Validity of averaged minimum- B configuration on Magnetohydrodynamics (MHD) stability of the GAMMA10 tandem mirror are studied in the ion cyclotron range of frequency (ICRF)-heated, hot ion mode plasma. It has been observed that the plasma can not be sustained mostly owing to the flute interchange mode when the high power ICRF is applied for the central cell ion heating. As the ratio of the central cell beta to the anchor cell beta increases, the amplitude of the flute interchange mode increases. The anchor cell plasma is also sustained by the another ICRF source in the central cell. The flute type MHD instability in GAMMA10 is well controlled by the phased ICRF antennas in the central cell.

Effects of Copper Vapor on Heat Transfer from Atmospheric Nitrogen Plasma to a Molten Metal Anode

As an object of nitrogen plasma operated with an arc current to 200 A, an arc length about 35 mm, we evaluated heating efficiency from arc plasma to the molten copper anode and the water-cooled solid copper anode. The heating efficiency to the molten anode is smaller than that to the solid anode by about 20%. We focused on copper vapor concentration in plasma as a possible cause for a decrease in heating efficiency, and estimated it by means of the Cu and the N spectral line measurement. Simple numerical analysis, taking into consideration measured copper vapor concentration, suggested that an increase in electrical conductivity due to copper vapor, made the plasma temperature change and consequently caused a decrease in thermal conductivity. We concluded that one of the reasons for a decrease in heating efficiency would be caused by copper vapor contamination.

Investigation of a New Dry Surface Decontamination Technology with Low-Pressure Arc Plasma and Its Application to Pipe-Shaped Test Pieces

We investigated a dry surface decontamination technology using low-pressure arc plasma for radioactive corrosion product films. The low-pressure arc plasma is produced with a transferred-type DC arc discharge that operates under reduced pressure; here, the cathode is the object to be treated. The cathode spots formed inside the low-pressure arc plasma can melt away the metal oxide film on the surface of the object without significantly damaging the metal substrate. One of the major advantages of this technology is its potential to reduce the amount of secondary waste compared with existing technologies, e.g., decontamination with chemical solutions, because it eliminates the need for a medium. In this report, the dependence of the decontamination performance on the type of plasmasource gas was investigated. Argon, hydrogen, chemically active carbon monoxide, and a mixed gas of CF4/O2 were selected. Consequently, a higher Cobalt-60 removal ratio was obtained with smaller electric charges in the hydrogen low-pressure arc plasma. The low-pressure arc plasma was also applied to pipe-shaped test pieces with a corrosion product film. And eventually, a Co removal ratio exceeding 90% was achieved. The applicability of the dry surface decontamination technology with low-pressure arc plasma for radioactive metal waste with a corrosion product film is demonstrated.

Investigation of the removal of nonradioactive corrosion product films using a low-pressure arc

Summary form only given, as follows. Most of radioactive solid wastes generated at time of operations or maintenance of atomic power plants are polluted near their surface. Therefore surface decontamination will make the treatment for final disposal and so on easier. One surface treatment technology using a low-pressure arc (LPA) has attracted considerable attention because it has the advantage of removing metal oxide film on metal used as a cathode selectively and quickly. So it allows removal of radionuclides present on or inside the oxide film found on the surface of radioactive metal wastes along with the oxide film itself. However there are few examples describing the application to the wastes generated from atomic power plants. So we chose four kinds of metal-alloys (SUS304, SUS316L, Inconel600, S50C) which are main materials of LWR metal constitution and formed the nonradioactive corrosion product films (CP) on these substrates by immersing themselves in water under conditions simulating a primary water-cooling line. Then argon LPA was applied to these CP and carbon steel with mill scale on the market.