US3484613A

US3484613A - Irradiation apparatus having a plurality of sources

Info

Publication number: US3484613A
Application number: US568278A
Authority: US
Inventors: Joel Kerjean
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1965-07-30
Filing date: 1966-07-27
Publication date: 1969-12-16
Anticipated expiration: 1986-12-16
Also published as: BE684274A; LU51674A1; CH460190A; GB1094423A; IL26212A; DE1539796A1; SE311959B; ES329710A1; NL6610442A; FR1457434A

Description

Dec. 16,1969 iKeRJeAN 3,484,613

Filed July 27, 1966 v 3 Sheets -Sheet 1 INVENTOR Ja'sL KER EA/v ATTORN E Y5 Dec. 16, 1969 E flE -N 3,484,613

IRRADIATION APPARATUS HAVING A PIJURALITY OF SOURCES Filed July 27, 1966 3 Sheets-Sheet 2 INVENTOR Jez. A EPJEHN ATTORNEYS J. KERJEAN Dec. 1 6, 1969 IRRADIATI'ON APPARATUS HAVING- A PLURALITY OF SOURCES Filed July 27. 1966 sweets-sheet 's r//////// fl//n//////////////////////////r n/r rw an INVENTOR JsL Ks'RJe'AN ATTORNEYS United States Patent ice 3,484,613 IRRADIATION APPARATUS HAVING A PLURALITY 0F SOURCES Joel Ker-jean, Le Vesinet, Yvelines, France, assignor to Commissariat a lEnergie Atomique, Paris, France Filed July 27, 1966, Ser. No. 568,278 Claims priority, applicatiogsFrance, July 30, 1965,

6,7 Int. Cl. G21l1 /00 US. Cl. 250-106 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an irradiation apparatus, particularly for the irradiation of samples under a high 'y flux. Irradiation apparatus of this type are generally made of a protective block of heavy material, in which a central chamber is formed to receive the sample. A plurality of sources is disposed in the chamber, the sources being inserted through channels parallel with the axis of the chamber, the ends of the channels being closed by removable plugs for biological protection.

The production of such an irradiation apparatus delivering a high 7 flux to the sample encounters the following substantial difficulty. An increase in the 'y flux can be obtained by bringing the sources nearer the sample and increasing their number, but, for want of space, it then becomes impossible to provide efficient biological protection in the zone for the introduction of the sources, i.e. at the points at which the channels issue from the outside of the block. Such protection would demand a stepped plug, projecting a long way from the channel and interfering with the plugs of the adjacent channels.

Irradiation apparatus used hitherto are therefore a compromise, which is generally not very satisfactory either from the point of view of protection or of the irradiation fiux than can be obtained with them.

This invention relates to a design for an improved irradiation apparatus that satisfies practical requirements better than previous arrangements, in particular by enabling the 'y flux to be increased in an irradiation chamber by bringing the sources nearer, while maintaining satisfactory biological protection at the points where the source-receiving channels emerge.

According to the invention there is provided apparatus for the irradiation of samples, said apparatus comprising a biological-protection block made of heavy material, an irradiation chamber formed in said block, a removable container for the samples to be irradiated, which can be inserted into said chamber, and a series of removable sources disposed in channels formed in the protection block, said channels entering the chamber and being distributed at equal angular intervals round the axis of the chamber, wherein the channels are disposed according to a family of generatrices of a hyperboloid with one surface whose axis is the same as that of the chamber and whose narrowed portion is placed opposite the container.

In a preferred embodiment of the invention, each source comprises at least two 7 emitter sections separated by an inactive zone, this zone being disposed opposite the 3,484,613 Patented Dec. 16, 1969 narrowed portion of the hyperboloid as occupied by the irradiation-sample container.

The invention will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a basic diagram showing the distribution of the'source-receiving channels along the generatrices of a hyperboloid with one surface;

FIGURE 2 shows diagrammatically the irradiation chamber, the central shaft and one of the source-receiving channels of an irradiation apparatus according to the invention, the protective block being shown in section along a plane passing through the axis of the shaft and the chamber;

FIGURE 3 is a general view of an irradiation means forming an embodiment of the invention given by way of non-restrictive example, shown in partial section along a plane passing through the axis of the shaft for receiving the sample to be irradiated, a single channel being shown for greater simplicity, and

FIGURE 4 is a section along the line IV-IV in FIG- URE 3.

The advantages of the arrangement according to the invention as compared with conventional arrangements with parallel channels will become immediately apparent from a numerical example corresponding to the arrangement in FIGS. 1 and 2. In this arrangement it is assumed that an irradiation having an intensity which 'is of the order of 5 Mrad/h. is to be produced in the chamber 6 in the protection block 8. The chamber has a diameter of 100 mm. and is 350 mm. in height, so that ten sources with an activity per unit of 5,000 curies, distributed over a length of 250 mm. and placed at a radial distance of mm. from the centre of the chamber are required. Under these conditions, if the channels for the introduction of these sources are parallel with thet axis of the chamber '6, their closure plugs 10 should have a diameter of at least 51 mm. in order to provide efficient protection. Such plugs cannot be used, for they would interfere with one another.

On the other hand, if the arrangement shown in FIGS. 1 and 2 is used, in which the channels 12 are inclined at 1830 to the vertical, the plug-receiving apertures 10 are distributed over a circle with a diameter of 410 mm., and this arrangement prevents any interferences and provides satisfactory protection against the radiation of the sources 13. Furthermore, in contrast to arrangements with parallel channels, only the protective material in a massive form is then present round the plug 14 which closes the shaft 16 providing access to the chamber 6, a zone that is weakened from the protection point of view by the presence of clearance and metal sheets for the guidance and reception of the heavy protection material.

In FIGS. 3 and 4, which show an irradiation means A according to the invention, the elements corresponding to those already shown in FIGS. 1 and 2 have the same reference number, for simplicity. The irradiation means A comprises a protection block 8 in three

parts

18, 20 and 22, which will be described in detail one after the other. The main part 18 is a block of heavy material, for example lead, disposed between an outer jacket 26 and an inner jacket made of sheet metal. The inner jacket defines the limit of the irradiation chamber 6, a shaft 16 providing access to the chamber, and a guide conduit 24 forming an extension of the shaft 16. To prevent the accumulation of ozone in the atmosphere of the chamber 6, circulation piping is provided, comprising an air-inlet conduit 28 and a conduit 30 for discharge into the atmosphere, having an ozone-decomposing means and a filtering means 32 for checking dust. To remove the heat released in the heavy material by the adsorption of 'y radiation, a coil 34 is immersed in this material and through which cooling water circulates in the direction shown by the arrows 1.

Ten source-receiving channels 12, only one of which is shown in FIGS. 3 and 4 for the sake of clarity, are also formed in the main part 18. These channels project a long way into the chamber and can be closed by biologicalprotection plugs provided with seals and each carrying a vessel which receives the source.

To make the flux as constant as possible in the space in the chamber 6 occupied by the samples to be irradiated, it is preferable to divide each source into two sections situated on either side of the median plane; as a result, a very slightly accentuated fiux minimum is obtained at the centre, instead of a maximum. Each source may, for example, be composed of two sections of 2,500 curies, using cobalt 60 as an emitter, each section being 100 mm. long and separated by an inactive section of 50 mm. of aluminium; this produces a useful volume with a height of 150 mm. and a diameter of 80 mIn., in which the flux is within 10% of 5 Mrad/h.

The sample-carrying container is formed by a plunger 36 with a central compartment surrounded by two protection elements occupied by heavy material, the top element forming the plug 14. The plunger 36 can be inserted in the shaft and removed therefrom by means of a control mechanism which will be hereinafter described.

The bottom part 20 of the protection block 8 is a base, which is preferably formed separately from the part 8 so that the weight can be split up during transport. The thickness of this base, which comprises a lead-filled casing 38, is determined, of course, according to the protection that can be provided by the ground on which the means A is placed.

The top part 22 provides protection at the top, particularly against radiation leakages occurring when the plunger 36 is raised. This part 22 is formed by a bell made of heavy material enclosed in a double-walled jacket, and it has pivoted doors 40 and 42 (FIG. 4) providing access to the irradiated samples when the plunger is raised. The top part 22 covers the plugs of the channels 12 and provides supplementary protection.

The three

parts

18, 20 and 22 are held as one unit by a frame 44 carrying the control mechanisms, shown in FIG. 3, which will now be described.

The control mechanisms comprise a rack 46 secured to the plunger 36 and meshing with a pinion 48 driven by a gear motor 50. A balancing counterweight 52 carried by a winch 54 limits the forces that have to be applied. Endof-stroke limit stops (not shown) determine the top and bottom positions of the plunger. A manual control (not shown) can be used to control the plunger if a breakdown should occur.

What is claimed is:

1. Apparatus for the irradiation of samples comprising a block of radiation absorbent material,

an irradiation chamber formed in said block,

a container for the samples to be irradiated, said container being removably supported within said chamher,

a plurality of rectilinear channels formed in said block, said channels extending into said chamber and being located along a family of generatrices of a hyperboloid having a surface whose axis is the same as that of said chamber and whose narrowed portion is opposite the container located in said chamber; and

a plurality of sources removably supported within said channels.

2. Apparatus as described in claim 1 wherein each source comprises two sections occupied by y-ray emitters, said sections being separated by a zone of inactive material which is oriented opposite said chamber when said source is supported within said channel.

3. Apparatus as described in claim 2 wherein said container has an extended portion on either side, said extended portion being comprised of 'y-ray absorbing material.

4. Apparatus as described in claim 3 including an access shaft formed in said protection block for the introduction of said container into said chamber and a conduit formed in said block opposite said shaft for the guidance of said container.

5. Apparatus as described in claim 4 wherein each of the channels into said chamber is of a suflicient length to accommodate the entire portion of the source within said chamber.

References Cited UNITED STATES PATENTS 3,132,251 5/1964 Maud et a1. 3,153,725 10/1964 Attix. 3,310,676 3/1967 Haram.

ARCHIE R. BORCHELT, Primary Examiner US. Cl. X.R. 250-108