Patent Number: 042119286
Section: summary

THE PRIOR ART As is shown in FIG. 1 of the accompanying drawings, systems for the handling of radioactive material 1 involve the provision of a storage unit 2 having a mass 3 of radiation-shielding material with a passage 4 through it, in which the radioactive material can be safely stored when not in use, as is shown in FIG. 1 at A, and from which the radioactive material can be moved to a use location, as for making a radiograph, as is shown in FIG. 1 at C. Typically, the radioactive material 1 is connected to drive means comprising a flexible cable 5 in a guide tube 6. The guide tube is generally provided in three essentially equal-lengths 6A, 6B and 6C, each of which can be disconnectibly coupled to the storage unit 2. Under control of a reel and crank arrangement 7 the drive cable 5 pushes the radioactive material out of the passage 4 and through the third guide tube 6C to a snout 8 located where the radiograph is to be made, as shown in FIG. 1 at B and C. The portion of drive cable 5 in the second guide tube 6B supplies the cable necessary to fill the first and third guide tubes 6A and 6C when a radiograph is being made. A disconnectible coupler 9 is fitted in the drive cable 5 so that when the radioactive material 1 is in the stored position the drive cable can be parted outside the storage unit for uncoupling the cable 5 and the guide tubes 6A and 6B from the storage unit. The part of drive cable 5 between the coupler 9 and the radioactive material 1 is known as the leader 11, and the coupling apparatus 10 between the guide tubes 6A and 6B and the storage unit 2 generally contains means to lock the leader against movement through the passage 4 when the drive means are uncoupled and removed. U.S. Pat. Nos. 3,147,383 and 3,593,594 describe prior systems in which these features are found. When the passage 4 through the storage unit is curved as shown in FIG. 1 the mere location of the radioactive material 1 in the middle part of the passage provides storage which shields the region surrounding the storage unit from radiation emitted by the radioactive material. The provision of a curved passage through the mass 3 of radiation-shielding material is, however, more costly than the provision of a straight-through passage, and the conduit which defines the curved passage is subject to wear after the parts holding and guiding the radio-active material have been pushed through it repeatedly. An early system for exposing a body of radioactive material by moving a rod through a straight passage is described in Gilks U.S. Pat. No. 2,551,491. In the patent a substantial part of the shielding material is moved away from the storage unit, to make the exposure. A form of straight-through exposure system which provides for locating the body of radio-active material remote from the storage unit, under control of a crank-type manipulator as shown in FIG. 1, is illustrated in British Pat. No. 712,009, of Stein; that system, however, uses two separate shielding masses, one rotatable inside the other, in a complex structure, to move the radioactive material from a shielded storage position to a posture in which it can be moved to an exposure position. It also shows a primitive claw-type coupling/decoupling mechanism for the drive cable which does not provide access for manipulating a cable coupling/decoupling mechanism of the more reliable modern form, as is illustrated, for example, in U.S. Pat. No. 3,237,977. A need exists for a modern system for handling radioactive material which incorporates a storage unit having a straight-through passage in its radiation-shielding mass and is compatible with current requirements of safety, utility, convenience, and lost cost. GENERAL NATURE OF THE INVENTION The present invention provides a storage unit for a system of the general type illustrated in FIG. 1 wherein the passage through the radiation shielding material is straight, the storage unit being fittable at a first end with a coupler of modern design for the drive cable and manipulating means, and at the second end with conduit means to guide the radioactive material to a location where a radiograph is to be made. A shutter or cover is provided for the second end, with interlock means to block the second end of the straight passage when the radioactive material is stored in the storage unit. The shutter is mounted on the storage unit for sliding movement transverse to the second end of the passage between first and second limits, the shutter in said first limit blocking the second end, the shutter having a hole through it which registers with the passage when the shutter is in the second limit. Shutter-retaining means are provided within the passage adjacent the second end, and resilient means cooperate with the retaining means and said storage unit for urging the retaining means to project an end-part toward the shutter. Means are provided in the shutter for receiving this end-part when the shutter is in the second limit, and thereby retaining the hole in register with the passage. Means coupled to the capsule are provided for pulling the retaining means away from the shutter against the action of the resilient means under control of the manipulating means, for withdrawing the end-part from the receiving means, and thereby permitting the shutter to move toward the first limit, again blocking the second end.