Equipment for Monitoring Some Radioactive Isotopes and Groups of Isotopes in Gas Discharges

This review discusses the special features of the measurement and monitoring of certain radioactive isotopes and groups of isotopes in gas discharges at establishments involved with the use of atomic energy, and describes the principles of operation and design of the corresponding industrial equipment produced in the USSR. It is demonstrated that In certain cases the sample taken must be divided into its separate components (gas, vapour, aerosols, condensate) before their activity is measured. Depending on the type of establishment, radioactive gases are monitored by argon-41 or by the group of isotopes of krypton and xenon. Radioactive iodine is monitored by measuring the activity of its aerosol phase collected by a fibre filter and of its vapour phase collected by a chemosorption filter. Beta aerosols are monitored as a group either with automatic compensation for the daughter products of radon and thoron or by separating the long-lived component by employing delay-time. Close attention is paid to the monitoring of long-lived alpha-active isotopes (uranium, plutonium, etc.). For this purpose a scintillation alpha spectrometry instrument is used with automatic compensation for the natural radiation background of the aerosols. The authors describe instruments intended for the continuous monitoring of multi-component discharges, beta-active gases and aerosols of radioactive iodine and long-lived alpha-active isotopes. They also describe an instrument with a pulsed ionization chamber, intended for measuring low alpha activities of aerosol samples and determining their precise isotopic composition. In all the equipment described, the aerosol particles are deposited on fibre filters of Petryanov fabric, which include special thin filters suitable for alpha spectrometry of the dispersed phase of aerosols, and also chemosorption filters for collecting iodine vapours. (author)