GB989647A - Improvements in or relating to gamma radiation monitors - Google Patents

Abstract

989, 647. Gamma radiation monitors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. June 12, 1963 [June 27, 1962], No. 24600/62. Heading G1A. Gamma radiation from a fluid is monitored by apparatus comprising a gamma radiation detector unit 1, and a vessel 2 for containing a sample of said fluid, the vessel 2 being provided with walls arranged such that the interior side wall surfaces of the vessel cannot be seen by the detector unit 1. Liquid from a process stream flows into the vessel 2 by a pipe 14 and out again by pipe 17. The vessel 2 is of frustro-conical shape the angles between the side walls and the top of the vessel being such that y-radiation from the walls cannot pass up a collimating tube 27 to the detector unit 1. The detector unit consists of a NaI crystal and a photomultiplier housed in a cylindrical casing 22 surrounded by lead shields 23, 24. The output from the photomultiplier is fed via an amplifier/E.H.T. generator to a transistorised ratemeter (not shown) where the count rate may be displayed linearly and logrithmically. To prevent splashed liquid from reacting the collimating tube a replaceable polythene window 28 mounted on a rotatable turntable 30 is interposed between the tube 27 and the top of the vessel 2. Two other windows on the turntable, consisting of a second polythene window used for comparison with the first polythene window to see if it has been contaminated, and a standard gamma source respectively, may be brought into position between the tube 27 and the vessel 2 by rotation of the turntable 30 by air operated rams in a housing 33. A set of interchangeable collimator tubes 27 of different diameters may be provided for varying gamma activities.