JPH04108451A - Method for enhancing reliability of electron beam irradiation - Google Patents

Abstract

PURPOSE:To uniformize packing density by measuring and sorting the density and distribution per unit area of an object prior to irradiation of the object with an electron beam and getting rid of the deficiency and excess of exposure. CONSTITUTION:When an object A to be irradiated passes through a soft X-ray generation equipment (generating part) 1, the signal of a penetrating X-ray dose from a detection part 2 is transmitted to a signal processing part 3, converted into a digital signal matching the surface density of the object A to be irradiated, and transferred to an arithmetic part 4. A minimum penetrating X-ray dose for a specified electronic energy lower than a data value measured in advance is considered inappropriate, and the arithmetic part 4 instructs a fractionation equipment 5 to remove the object A to be irradiated from a transfer line for fractionation processing. Further, the arithmetic part 4 judges the distribution of the digital signal, calculates an accelerating voltage value matching it, and gives instructions to an electron beam generating part 7, thereby avoiding excessive irradiation. Thus, the packing density can be uniformized.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for improving the reliability of electron beam irradiation as an alternative to radiation irradiation using cobalt-60 gamma rays. The present invention relates to a method for improving the reliability of electron beam irradiation by adjusting selection and electron energy accordingly.

<Prior art> In general, the use of radiation irradiation using cobalt-60 gamma rays to sterilize certain objects (e.g. medical tools, bio-related laboratory equipment, etc.) has become established worldwide.
Various contract irradiation facilities are in operation in various countries. However, recently, easy-to-handle electron beam irradiation is becoming more popular.

In this case, the electron beam is a flow of electrically generated high-speed electrons, and is radiation that can be processed at high output and at high speed. On the other hand, the penetration power depends on the electron energy, with 3Mev energy being 0.9 grams per square centimeter (approximately 2.5 times when irradiated from both sides), and 5MeV energy being 1.6 grams per square centimeter. Senna Kogata (irradiation from both sides, f
, - about 2.5 times). This value is cobalt 60
When irradiating gamma rays on both sides, approximately 20 grams per square centimeter is irradiated, and if the uniformity of the dose (expressed as the value obtained by dividing the highest dose by the lowest dose) during packaging is allowed to increase, even more per unit area can be irradiated. It is possible to irradiate objects with high density. Based on this large difference in penetrating power, the conventional method of electron beam irradiation is to measure the dose of the irradiation target in the packaging or container brought in by the contractor prior to industrial irradiation, and to optimize the irradiation target arrangement.・Operation conditions for the electron beam generator have been established, and from now on, large-scale irradiation will be carried out on the condition that it be brought in in packaging using the same packing method.

In other words, the current situation is to prevent insufficient irradiation doses only by providing explanations to contractors prior to irradiation and contract conditions.

<Problem to be solved by the invention> However, in reality, the object of irradiation inside the container may be due to overfilling by a contractor who does not have sufficient recognition of the difference in the penetrating power of gamma rays and electric r-beams, or due to vibrations during transportation. Even if the irradiation dose is insufficient due to a partial (-part product) increase in density per medium area due to unevenness of the object, or if there is a change in the shape, material, etc. of the product irradiated with the electron beam. There is a possibility that the irradiation dose may be insufficient for some products due to not requesting irradiation Q7 TFI determination prior to irradiation and not notifying the irradiation contractor.

In view of the above-mentioned circumstances, the present invention provides a method that does not produce products with insufficient dose due to excessive density per unit area, and furthermore, adjusts the irradiation conditions by linking the voltage of the electron beam generator with the density per unit area. The object of the present invention is to provide a method for improving the reliability of electron beam irradiation that solves the above-mentioned problems by optimizing the method and preventing excessive irradiation.

Means for Solving the Problems> The present invention, prior to irradiating an object with an electron beam, measures and sorts the density per unit area of the object and its distribution, and selects products with insufficient or excessive irradiation IiI amount. It is absolute.

Specifically, the projected area and weight of the irradiation target are measured and selected before loading onto the irradiation line, the irradiation target is irradiated with soft X-rays, and the intensity distribution of the transmitted X-rays is measured. Accordingly, the materials are sorted prior to being loaded onto the irradiation line.

Furthermore, the object to be irradiated is irradiated with soft X-rays, and the optimal electron energy for each irradiation batch is automatically instructed to the electron beam generator from the measurement of the intensity distribution of the transmitted X-rays and the calculation of the intensity distribution. This prevents irradiation.

<Operation> In order to perform the above method, the density per unit area is measured in the irradiation line loading and conveying part, and in conjunction with this, the irradiation object sorting device or the density per unit area and density distribution measurement are performed. It is a combination of the device and the voltage control device for the electron beam generator.

For example, the average density per unit area of powder, granule, or sheet-like objects that can be considered uniform depending on the filling method can be determined from the reading of a weighing scale installed on the conveyance unit and the projected area of the irradiation object.
In actual operation, the projected area of a container storing objects to be irradiated is constant in the same batch, so it is sufficient to measure only the weight, and it is sufficient to select overfilling objects by automatic strain Jiijf. Depending on the purpose of electron beam irradiation, such as sterilization, it is not permissible to lower the dose below the specified dose for any part of the product. In such cases, it is not permissible to determine whether irradiation is possible by measuring the average density per unit area. In this case, the density distribution per unit area may be measured by irradiating the object with X-rays and measuring the amount of transmitted X-rays in each part. The sterilization dose can be guaranteed by sorting the packaging of irradiation objects whose density per unit area exceeds the limit value for electron beam irradiation, even if only partially, using a sorting device based on the X-ray transmission image. However, in electron beam irradiation, the contribution of scattered radiation is large, so if the density per middle surface of the minimal part is high, it may be acceptable, so the dose distribution M1 is determined for each product. Is it necessary to set standards for line transmission images and selection?

Furthermore, if the density per unit area of the irradiation target is smaller than the areal density suitable for double-sided irradiation, there is a range of areal density in which the irradiation target in the center of the container will be over-irradiated due to the characteristics of the electron beam. .

In such a case, more uniform irradiation can be achieved by lowering the electron energy and selecting the optimum energy. To select such an optimal electron energy, calculate the optimal electron energy by calculating the X-ray transmission intensity,
It is only necessary to automatically instruct the electron beam generator, thereby making it possible to prevent excessive dose irradiation.

<Example> The following is a description of an apparatus for carrying out the method of the present invention based on the drawings.

The drawing uses the X-ray transmission method, and there are no particular restrictions on the method of transporting the object to be irradiated with the electron beam.
This shows a commonly used conveying method using roller conveyor hair.

That is, the main equipment combination of the present invention is a soft X-ray generator (hereinafter referred to as generation section 1) that serves as a unit area density measurement device, and a sensor that detects the amount of soft X-rays that has passed through the irradiation object. The X-ray detection unit (hereinafter referred to as
A detection unit (referred to as a detection unit 2) is installed above and below the conveyance unit 9, which is the irradiation line of the roller conveyor, and analyzes electrical signals from the detection unit, that is, a digital processing device for digitizing the dose intensity of each part relative to the reference intensity. (hereinafter referred to as signal processing unit 3), determines whether or not irradiation is appropriate for the digital signal,
Or the optimum conditions for the electron beam generator, i.e., an electronic computer section and a control device t (hereinafter referred to as arithmetic section 4) for determining the accelerating voltage, and a classification for distinguishing whether irradiation is suitable or not based on a signal from the arithmetic section 4. It consists of a device 5 and irradiation object transport equipment.

The arrangement relationship between the irradiation target A, the generation section 1, and the detection section 2 is 10 to 1 from the same direction as the irradiation direction of the electron beam generator.
Place the generator 1 so that it will be irradiated with soft X-rays of 00 kV, and place the X1lTV on the opposite side of the generator 1 across the irradiation target A.
A detection unit 2 consisting of a camera system and an image processor is installed. The signal processing section 3 and the calculation section 4 do not need to be placed near the generation section 1 and the detection section 2 as long as the signal from the detection #1 is properly sent. The sorting device 5 is installed in a conveyance section 9 that serves as a receiving conveyor, and a stockyard 12 of objects unsuitable for irradiation is installed on the side of the sorting device 5.
1, the conveying section 9 at the tip of the stockyard 11 has a branching section 9b to form a rotating conveying section 9a, and an irradiating section 8 is disposed in the middle of the rotating conveying section 9a. Upper part (
An electron beam generating section 7 (which may be connected to the arithmetic section 4 via an electron beam control section 6 as required) faces the side or the bottom depending on the configuration of the transport system.

In addition, an irradiated product sorting and unloading section 10 is provided after the irradiation section 8 of the rotary conveyance section 9a, and a reversing machine 13 is installed in the rotary conveyance section 9a after the irradiated product selection and unloading section 10, and both sides are irradiated. It becomes a transport line that makes it possible to

Next, the flow of the irradiation target will be described in detail. First, the irradiation target A placed on the conveyance section 9 of the roller conveyor is passed through the generation section 1. At this time, the transmitted X-ray dose signal from the detection section 2, which is installed on the opposite side of the generation section 1, is sent to the signal processing section 3, converted into a digital signal according to the areal density of the irradiation target, and sent to the calculation section 4. passed on.

In addition, the irradiation unit is determined to be unsuitable if the minimum transmitted X-ray dose for the specified electron energy is less than a pre-measured data value, and a calculation is made to the sorting device 5 to remove the irradiation target from the conveyance line. Separation processing can be easily performed by giving instructions from section 4. Furthermore, over-irradiation can be avoided by determining the distribution of the digital signal in the calculation section 4, calculating an accelerating voltage value corresponding to the distribution, and instructing the electron beam generation section 7.

In addition, the irradiation target A that requires double-sided irradiation is not discharged from the irradiated product sorting and unloading section 10 of the rotary conveyance section 9a, but is conveyed and rotated as it is and supplied to the reversing machine 13. The object A to be irradiated is rotated by 180°, the branch #9b is turned, and the object A is again carried into the irradiation section 8, where it is irradiated with an electron beam. That is,
By carrying the electron beam into the irradiation section 8 again, it becomes possible to irradiate the object A with an electron beam from the opposite side, and it is possible to process an object with a surface density 2.5 times that of single-sided irradiation.

<Effects of the Invention> As mentioned above, the method for improving the reliability of electron beam irradiation of the present invention consists of two types: a gravimetric method and an X-ray transmission method, and the gravimetric method measures only the average median areal density. Therefore, it can be effectively applied to purposes such as polymer modification, where the uniformity of packing density is guaranteed for powder, granule, plate, etc., and the electron beam irradiation effect can be evaluated based on the average dose. Moreover, various commercially available products can be used for weight measurement during transportation, and they have the advantage of being inexpensive.

On the other hand, the X-ray transmission method can measure the density distribution per 1J1 area in packaging in detail, so it can be used not only for the above-mentioned polymer modification, but also for sterilization of processed products where even a partial dose is not acceptable. Optimal. In this case, it is necessary to thoroughly test the relationship between X-ray transmittance and sterilization, and to measure in advance the spread of the electron beam in the container filled with the product. In view of the purpose of the present invention, unlike an X-ray baggage inspection system, it is not necessary to display the image on a CRT, but the amount of X-ray transmitted through each part is sent as an electrical signal to a computer for processing, and the object to be irradiated is It is sufficient to perform separation of the electron beams or control the acceleration voltage of the electron beam generator. Therefore, it has the advantage of being widely applicable and highly reliable under any product conditions.

[Brief explanation of the drawing]

The drawing is a schematic diagram of an apparatus for carrying out the method of the invention. 1... Generation section, 2.-Detection section, 3... Signal processing section,
4... Arithmetic unit, 5... Sorting device, 6... Electron beam control unit, 7... Electron beam generation unit, 8... Irradiation unit,
9... Conveyance section, 10... Irradiated product sorting and unloading section, 1
1... Irradiation part target stock yard, 12... Irradiation unsuitable target stock yard, 13... Inversion II. Patent applicant: Raje Kogyo Co., Ltd. Agent
Human Tail Mat Yuki Male - Ketsukuri Dingho - ■ ÷ 1 ((Voluntary submission) October 30, 1990

Claims (1)

[Claims] 1. Prior to irradiating an object with an electron beam, the density per unit area of the object and its distribution are measured and selected to eliminate products with insufficient or excessive irradiation dose. A method for improving the reliability of electron beam irradiation. 2. The method for improving the reliability of electron beam irradiation according to claim 1, wherein the projected area and weight of the irradiation target are measured and selected before being loaded onto the irradiation line. 3. The method for improving the reliability of electron beam irradiation according to claim 1, wherein the object to be irradiated is irradiated with soft X-rays and the intensity distribution of the transmitted X-rays is measured to select the objects before loading onto the irradiation line. 4. The object to be irradiated is irradiated with soft X-rays, and the optimal electron energy for each irradiation batch is automatically instructed to the electron beam generator from measurement of the intensity distribution of the transmitted X-rays and calculation of the intensity distribution. A method for improving the reliability of electron beam irradiation.