Improvements in or relating to fission product detectors

1,011,664. Electrostatic precipitators. COMMISSARIAT A L'ENERGIE ATOMIQUE. Jan. 25, 1963 [Feb. 5. 1962], No. 3276/63. Heading B2J. [Also in Division G1] A detector of fission products in a gas comprises a conveyer member 1 with a plurality of zones on which ionized particles derived from the fission products are collected by electrostatic precipitation and a measuring apparatus such as a # scintillator 33 and a photomultiplier 35 located adjacent the conveyer member 1 for determining the radioactivity of each zone after collection of the particles, the conveyer member having a machined non-deformable plane surface on which the collection zones are located and being arranged to move in its own plane so that a further collection can be made upon a given zone only after a period of time sufficient for such zone to become substantially decontaminated by natural decay of the ionized particles previously collected. In the embodiment shown gas containing the fission products flows through a conduit 28 into a collection chamber 8 formed by an electrostatic precipitator consisting of a block of insulating material having a frusto-conical recess 23 on which is secured a metal electrode 27 having a part-spherical recess 26. A rotatable metal disc 1 forming a conveyer and the other electrode of the precipitator is positioned so that on an annular area of its rim coincident with the apex of the frusto-conical recess 23 circular collection zones, Fig. 1 (not shown), each correspond to the area of the apex. The disc 1 is driven intermittently by a motor so that each zone in sequence is positioned under the chamber 8 to collect ionized particles and is then moved to below a # scintillator 33, the resulting scintillators on which shine through a transparent conduit 34 to a photomultiplier 35. After each zone has completed its cycle and is again under the chamber 8 it has become substantially decontaminated by natural decay. In a further embodiment, the disc 1, Fig. 5 (not shown), is of insulating material, the collection zones are on a metallic layer formed on the annular area of the disc and the electrode of the precipitator is earthed, a negative source of high tension being fed to the metallic layer by a sliding contact. In another embodiment, Fig. 6 (not shown), the disc 1 is of insulating material and the collection zones are on a thin annular area and a negative electrode is placed below the chamber 8 under the annular area.