JPS62190481A - Dosage meter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. (Industrial Field of Application) The present invention comprises at least one radiation detection device, and a radiation detector configured to allow a gas to flow through the detection device. The present invention relates to a radiometer for measuring radiation of a flowing gas, which is equipped with measurement filters arranged opposite to each other.

(Prior Art) This type of radiation meter is widely used today to measure the radiation dose in the spent air or exhaust air of nuclear power-related equipment. The exhaust air contains radioactive aerosols in the middle part (
The signal passes through a measurement filter held in an intermediate 5tore. The radiation emitted from this measurement filter is detected within a normal radiation detection device.

Since radiation detection devices are highly sensitive, they can detect even extremely small radiation exposures.

(Problems to be Solved by the Invention) However, such a radiation detection device has a problem in that it must measure radiation exposure even in the event of an accident. If such an accident were to occur, the operating range of a highly sensitive radiation detection device would be far exceeded, and the detection device would become "overloaded" and therefore unable to provide accurate measurement results.

As a solution to this problem, it has been proposed to install two types of radiation measurement devices with different measurement ranges, one for normal measurements and the other for accidents. Naturally, such a solution involves considerable extra expense.

It is therefore an object of the present invention to provide an improved version of the above-mentioned method, which guarantees high measurement sensitivity with the smallest possible amount in normal measurements and allows higher radiation exposures to be measured accurately in the event of an accident. Our objective is to provide the following types of radiometers.

(Means for Solving the Problems) The radiation meter of the present invention includes at least one radiation detection device and a measurement filter arranged opposite to the detection device through which gas flows. A radiometer for measuring radiation of a flowing gas, comprising: a radiating surface (radiating 5urf) of a filter for the measurement;
ace) and an effective surface (ef) of the at least one detection device.
The above-mentioned object is achieved by means of changing the relationship between the 5 surface and the 5 surface in a predetermined manner.

The basic idea of the invention is therefore to enable a defined change in the ratio between the emitting surface of the measuring filter and the effective surface of the detection device located opposite thereto. This can be achieved by varying the volume in front of the detector or by means of a diaphragm that shields some of the radiation from the measurement filter to the detector. As soon as the radiation measured by the detection device exceeds a predetermined value, either the volume is reduced or the size of the opening of the diaphragm is reduced.

A preferred embodiment of the invention uses a diaphragm. This embodiment will also be explained in the description of the examples below.

All of the technical matters shown in the claims, the detailed description of the invention, and the drawings constitute essential parts of the present invention, each individually or in any desired combination.

(Example) Exhaust is supplied to the radiation meter 1 through an annular gas supply line 11.
Sent to 0. The gas supply line 11 has a cylindrical gas port 12 and a plurality of gas outlets indicated by arrows 13 . The exhaust air or gas flows through the gas outlet 13 and past the measuring filter 14 . A measuring filter 14 faces the gas outlet 13 and is made, for example, of a glass fiber mat. . In this embodiment, measurement filter 1
4 is held by a sintered metal plate 15. Sintered metal plate 15 is gas permeable and presents virtually no resistance to flow. A funnel-shaped gas collector 16 is provided downstream of the sintered metal plate 15, and a cylindrical gas outlet 17 is provided behind the funnel-shaped gas collector 16.

In this embodiment, a plurality of radiation detection devices 18 to 20 stacked on top of each other are arranged facing the measurement filter 14 (above the gas supply line 11 in FIG. 1). The detection device 1 located closest to the measurement filter 14
8 is designed for alpha radiation. Above it is a detection device 19 for β-rays. Finally, at the top there is a detection device 20 designed for gamma rays.

Between the detection device 19 and the detection device 20, there is a [Pertinax] impermeable to β rays.
A J disk 21 is provided. The upper side of the detection device 20 is covered with a temporary 22 made of steel or the like.

The basic structure and mode of operation of these detection devices 18-20 are known in principle. Each detection device uses a so-called "counting gas" such as a mixture of argon and methane.
ting gas) J is supplied. In this embodiment, this counting gas is supplied to the three detection devices 18-20 by a common branch passage 23. Each detector chamber is provided with a respective counting gas outlet 24-26. In principle, the counting gas is ionized by radiation,
The ions generate electrical signals at the corresponding electrodes of the detection device. In this example, from the electrode there is a wiring line fIA28 to 30.
are drawn out respectively. Furthermore, high voltage is applied to each detection device via wiring 27. In the illustrated embodiment, all three sensing devices have the same high voltage applied to them. However, it is also possible to apply different high voltages to each detection device.

The output signals of the detection devices are each sent to an evaluation circuit 31 via lines 28 to 30. The circuit 31 is provided with a display device, a recording device, or both. It is also possible to perform signal processing such that the ratio of α, β, and γ rays can be determined from each signal. The output signal of the detected value W18 may include a signal ratio due to β rays and γ rays.

Similarly, the output signal of the detection device 19 may still contain a signal proportion due to gamma radiation. Therefore, individual radiation proportions can be determined by signal processing such as differentiation.

In one embodiment of the invention, a diaphragm 32 is arranged between the measurement filter 14 and the next adjacent detection device 18 . In an exemplary particularly preferred embodiment, the diaphragm 32 is connected to the sensing device 18 and the gas supply line 11.
It is located between. In this case, the diaphragm 32 has two windows 33, 34 with different opening sizes. The large window 33 corresponds to the entire surface of the measuring filter 14 or of the detection device. On the other hand, the small window 34 can be made extremely small, for example, about one tenth of the area of the window 33.

The diaphragm 32 is displaceable by a displacement mechanism 35. The displacement mechanism 35 is actuated by a drive 36 such that in one extreme position the window 33 is located opposite the measuring filter 14 and in the other extreme position the window 34 is active. The displacement can also be a linear movement. Further, the diaphragm may be moved by rotation, tilting, or other methods.

Evaluation circuit 31 has limit value warning elements for the signals transmitted by lines 28-30. As soon as such a limit value is exceeded, an electrical signal appears on line 37, for example similar to a comparator, which forces the drive 36 (e.g. an electric motor) to move the diaphragm from one limit position to the other. Make it move. As a result, the measurement range of the detection device is switched. In the case shown, a small window 34 is useful. This means that the radiation reaches the detection device only via this window 34. The respective position of the diaphragm is stored in the evaluation circuit 31, so that it is only necessary to multiply the measurement results of the detection devices 18-20 by a factor corresponding to the ratio of the opening cross-sections of the windows 33,34.

In one embodiment of the invention, the diaphragm is constructed of aluminum approximately 3 mm thick and shields only alpha and beta radiation. In this case, therefore, "switching the range"
is performed only for detection devices 18 and 19.

According to another embodiment, the diaphragm is made of lead approximately 7-3 cm thick, thereby also shielding gamma radiation.

The illustrated diaphragm could be replaced by an infinitely adjustable diaphragm, such as an annular diaphragm similar to those commonly used in photographic machines. Similarly,
It is also possible to move or swing one or two plates without apertures longitudinally in the beam path in a manner analogous to a slit diaphragm to cut off a portion of the radiation.

(Effects of the Invention) As described above, according to the present invention, a radiation meter that has the desired high sensitivity in normal measurements and provides accurate measurement results in the event of an accident can be realized with an extremely simple configuration. can do.

4.7 ゛L Figure 1 is a schematic cross-sectional view of one embodiment of the radiometer of the present invention.

14... Measurement filter, 18-20... Radiation measuring device, 31... Evaluation circuit, 32... Diaphragm,
33...large window, 34...small window, 35...
Displacement mechanism, 36... drive device.

that's all

Claims (1)

[Claims] 1. Radiation of a flowing gas, comprising at least one radiation detection device and a measuring filter arranged opposite to the detection device through which the gas flows. A radiometer for measuring , comprising means for varying in a predetermined manner the relationship between the emission surface of the measurement filter and the effective surface of the at least one detection device. 2. The radiometer according to claim 1, wherein said means is an adjustable diaphragm arranged between said measurement filter and said at least one radiation detection device. 3. The invention further comprises an evaluation circuit which changes the diaphragm to a smaller diaphragm window by means of a drive device and an adjustment mechanism when the radiation detected by the at least one radiation detection device exceeds a predetermined value. The radiometer according to scope 1 or 2. 4. The radiometer according to claim 2 or 3, wherein the diaphragm is a plate that is displaceably supported and has at least two windows with different opening sizes. 5. The radiometer according to claim 2 or 3, wherein the window of the diaphragm is continuously variable. 6. The radiometer according to any one of claims 2 to 5, wherein the diaphragm is made of aluminum. 7. The radiometer according to claim 6, wherein the diaphragm has a thickness of 3 mm. 8. Claim 2, wherein the diaphragm is made of lead.
The radiometer according to any one of Items 1 to 5. 9. The radiometer according to claim 8, wherein the diaphragm has a thickness of 70 to 80 mm. 10. Three radiation detection devices for different types of radiation are arranged in a stack in the beam path, said diaphragm being such that at least one type of radiation passes only through the window of the diaphragm. A radiometer according to any one of claims 1 to 9, which is made of a material. 11. The radiometer according to claim 10, wherein the types of radiation are α rays, β rays, and γ rays.