GB1231396A

GB1231396A -

Info

Publication number: GB1231396A
Application number: GB3514567A
Authority: GB
Priority date: 1967-07-31
Filing date: 1967-07-31
Publication date: 1971-05-12

Abstract

1,231,396. Monitoring radio-activity. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. July 31, 1968 [July 31, 1967], No.35145/67. Heading G1A. [Also in Divisions B1 and G6] The radio-activity of a gas stream, e.g. from the stack of a nuclear reactor, is monitored for isotopes which might enter and be retained in the human body by passing the stream through a filter medium on which these isotopes are adsorbed, and for isotopes which introduce radio-activity into the air so that the human body becomes subjected to irradiation from the ambient atmosphere, by detecting the beta and gamma emitters in the gas stream after it has passed through the filter medium. A sample of gas is drawn through duct 4 from the main flow 2 to the stack 1, by a pump 3. The gas sample passes through a duct section 7c packed with charcoal dust, which retains any radio-active iodine in the gas stream. The activity is measured by a pair of scintillation counters 7a. The unit 7 may be provided with automatic apparatus for renewing the charcoal in section 7c with a fresh charge, the used charcoal falling into bin 24. This apparatus is detailed in Fig. 3 (not shown). A differential pressure switch 5 senses when there is a gas flow in section 7c. The gas stream is filtered of charcoal dust by filter 10 and then enters beta monitor 8 comprising a scintillation detector using an anthracene crystal. After this the gamma activity is measured by a pair of scintillation counters 9a. One of the counters of each pair 7a, 9a is provided with a shielding block 7b, 9b formed with slots 7d, 9d through which the radiation reaches the detector. This reduces the sensitivity of the counter with respect to that of its twin and thereby enables the investigation of different activity ranges by the two counters. The blocks each contain a further slot at right angles to slots 7d, 7d in which is located a standard gamma source, This can be moved, by a solenoid, into the main slot 7d, 9d so as to enable calibration or checking of the detector system.