Patent GB-1133197-A (GB)
Title: Method of and apparatus for the irradiation of fluids, granules or powders
IPC: G21K5/02
Filed: 1966-02-28
Abstract: 1,133,197. Irradiating fluids, granules or powders. SAINT-GOBAIN TECHNIQUES NOUVELLES. 28 Feb., 1966 [26 Feb., 1965; 2 Feb., 1966], No. 8685/66. Heading H5R. Fluids, granules or powdered materials are irradiated by being passed through an arrangement of tubes positioned around a radio-active source within a shield chamber, whereby each molecule or particle of material is caused to follow the same path and remain within the irradiation field for the same length of time so as to receive substantially the same radiation dose, the escape of radiation outside the chamber being substantially prevented by the arrangement of tubes and the rate of flow of the material through the tubes being controlled at the discharge end of the tubes according to the radiation dose desired. The radiation source is preferably elongated in shape and is disposed vertically, and the flow of the material through the tubes may also be regulated according to the nature and density of the material. The tubes used may be shaped internally so that each layer of material passing through the tubes moves without substantially changing shape and makes at least one complete turn on itself while being subjected to irradiation. Preferably, the material follows a helical path through the tube which path is twisted around a zone which remains empty of material to be irradiated, which zone may be a cylindrical zone coaxial with the helical path. The chamber may contain at least two groups of tubes, the first group being distributed round the radiation source, the tubes of the other group or groups being placed to mask the gaps between the tubes of the first group. Fig. 1 shows one embodiment of a suitable apparatus being a chamber 1 into which material is fed by a screw 4 to be distributed by tubes 6 into tubes 11 having helical paths 9 and 10 around which the material circulates being withdrawn by tube 13, screw 14, weighing machine 16 and conveyer 17. Tube 13 is rotated in member 12 to be aligned with the various tubes 11 and the speed of rotation governs the rate of withdrawal, this speed being regulated via the weighing machine 16. Fig. 2 shows Fig. 1 in plan and Fig. 5 shows in plan an alternative arrangement where the chamber 1 is rectangular and two groups of tubes 140 and 142 of differing dimensions are situated in the chamber. This embodiment, Fig. 4 (not shown), has a different feed arrangement comprising two vertical tubes connected by a horizontal section forming a baffle, this section being shielded to stop radiation escaping in a vertical direction. A different withdrawing means is also used, namely each tube discharges into a chamber containing a rotatable paddle wheel 178 divided perpendicularly to its axis of rotation 160 (Fig. 7) into a number of sections 174- 177 having compartments 180, each section being fed at will through the appropriate orifice in the rectangular grid formed by members 163-167, which orifices may be selectively closed by sliding members 169-172. If desired, the tubes through which the material to be irradiated is passed may be coiled around a hollow cylinder aligned with the axis of the chamber. As seen from Figs. 2 and 5, the source may be a cylindrical array 23a, 23b or comprise rectangular plates. These sources also comprise a number of sections which are retractable into a container having a length equal to that of one of the sections. Thus, for example in Fig. 1, the source comprises three sections attached to plate 25, 26 and 27 and retractable by withdrawing and removing the conveyer thread 4, and extension piece 29 (Fig. 3, not shown) into cylindrical container positioned in the place of hopper 5, when shielding elements 22 and 20 are utilized as the top and bottom of the container. Fig. 4 (not shown) illustrates a container positioned on the floor of the chamber into which the array of rectangular source plates is collapsed.