STUDY ON THE APPLICATION OF RADIOCHEMICAL METHODS TO THE ANALYSIS OF METALS. I. ACTIVATION ANALYSIS OF IMPURITIES IN THE METALLIC SILICON OF HIGH PURITY

Metallic silicon of high purity was irradiated with thermal neutrons to analyze impurities radiochemically. As a result, it was found that the specimens contain an extremely small amount of copper. The quantities of copper were 0.25 approximates 0.32 ppm for the iodide silicon method, and 0.11 approximates 0.14 ppm for the trichlorosilane silicon method. The amihilation radiation of BETA / sup +/ from Cu/sup 64/ was counted with the single channel gamma spectrometer using the well type NaI--Tl gamma detector. The energy calibration and the counting efficiency of BETA /sup +/ were determined by the standard sample of Zn/ sup 65/. With this efficiency, the quantities of copper were determined from the activities of Cu/sup 64/. Chemical separation of copper from the matrix silicon was not carried out. There are many factors that have influence on the determination, such as fluctuations of neutron flux, uncertainty of irradiation time, and self absorption of radiation with the specimen. Consequently, the determination was not carried out by the generally used reference method for the activation analysis, but by the activity measurement method. (auth)