JP2576231B2 - Landry Monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a radioactive material handling facility such as a nuclear power plant, which is used to wash radioactive materials on the surface of a measured object such as used clothes before or after washing. The present invention relates to a land re-monitor that performs a contamination test.

(Prior Art) FIG. 2 is a schematic configuration diagram of a conventional land re-monitor.
In the figure, a land re-monitor 1 mainly includes a wire mesh conveyor 2 to be measured, another wire mesh conveyor 3 provided opposite to the conveyor 2, a photoelectric switch 4 including a light emitting element 4A and a light receiving element 4B, radiation detection. Instrument 5,5A, measuring instrument 6,
6A and a signal processing unit (microcomputer) 7 are housed in the land re-monitor body 1A. The light emitting element 4A and the light receiving element 4B of the photoelectric switch 4 are a monitor main body.
It is placed above and below the wire mesh conveyor 2 in 1A, and detects an object to be carried in.

(Problems to be Solved by the Invention) However, the photoelectric switch 4 has a problem that the sensitivity is lowered because the elements 4A and 4B are deteriorated or dust adheres to the lens surfaces thereof. In general, the sensitivity of the photoelectric switch 4 varies depending on the conditions under which the object to be measured can be reliably detected, that is, the thickness and material of the object to be measured. For example, the thinner or the higher the transparency, the better the transmittance of the light beam (beam) of the photoelectric switch 4. Therefore, the object to be measured cannot be detected unless the sensitivity of the photoelectric switch 4 is reduced.
Therefore, the sensitivity of the photoelectric switch 4 needs to be set to an intermediate level between the range in which the object to be measured is detected but the metal wire of the wire mesh conveyor 2 is not detected.

Further, since the detection circuit of the photoelectric switch 4 is turned on / off according to the amount of light received by the light receiving element 4B, if dust accumulates on the lens surfaces of the light emitting element 4A and the light receiving element 4B or the optical axis is shifted, The same condition as when the amount of received light is reduced and the sensitivity is reduced, and the wire mesh conveyor 2 whose transmittance is much better than that of the object to be measured.
There was a risk of detecting the metal element wire. Therefore, the object detection signal of the photoelectric switch 4 is used as a trigger for setting various timings in the measurement operation of the land re-monitor 1, and by detecting the metal element wire of the wire mesh conveyor 2, There is an important problem to be solved in that the land re-monitor 1 may malfunction.

The present invention has been made in consideration of the above circumstances, and provides a land re-monitor that effectively solves the problems of the related art, detects a malfunction due to a decrease in sensitivity of a photoelectric switch that detects an object to be measured, and improves the reliability thereof. With the goal.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides a radiation detection apparatus which is provided to face a wire mesh conveyor and measures radioactive contamination of an object to be measured carried in by the wire mesh conveyor. And a gate circuit to which an output signal of the photoelectric switch is input, and a pulse of an output signal by the object to be measured. A gate control circuit that outputs a gate signal controlled to a pulse length by the element wire of the wire mesh conveyor shorter than the length to the gate circuit, the sensitivity of the photoelectric switch is reduced, and the pulse length of the output signal is reduced by the wire mesh. It is provided with a photoelectric switch sensitivity detection circuit that outputs an alarm signal at a pulse length of the gate signal or less corresponding to the detection of a strand of a conveyor. .

(Operation) By such technical means, in the present invention, the pulse length is controlled by the wire circuit of the wire mesh conveyor, which is shorter than the pulse length of the output signal by the gate circuit to which the output signal of the photoelectric switch is input and the output signal by the device under test. A photoelectric switch sensitivity detection circuit comprising a gate control circuit that outputs a gate signal to the gate circuit reduces the sensitivity of the photoelectric switch, and the pulse length of the output signal corresponds to the metal wire detection of the wire mesh conveyor. By outputting an alarm signal when the length becomes shorter than the length, a malfunction of the land re-monitor is prevented, and the reliability thereof is improved.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of one embodiment of the present invention,
(A) is a block diagram thereof, and (B) is a waveform diagram of the gate signal of (A). In the figure, a photoelectric switch sensitivity detection circuit 8 mainly includes a gate control circuit 9 and a gate circuit 10. The output signal a of the photoelectric switch 4 is input to the gate control circuit 9 and the gate circuit 10, and the gate signal b controlled by the gate control circuit 9 is input to the gate circuit 10. If the pulse length of the output signal a is less than or equal to the pulse length p of the gate signal b, the gate circuit 10 outputs an alarm signal c. Conversely, if the pulse length is longer than p,
An object-under-test detection signal d is output.

Usually, the length of the object to be measured has at least about 100 mm,
Since the diameter of the metal wire of the wire mesh conveyor 2 is 2 mm or less,
The pulse length of the DUT detection signal a of the photoelectric switch 4 is
Significantly different from the pulse length when a metal strand is detected.
Therefore, by paying attention to the pulse length (pulse time) of the detection signal “a”, it is possible to determine the object to be measured and the wire mesh conveyor 2. For this purpose, the pulse length p of the gate signal b of the gate control circuit 9 is selected according to the speed of the wire mesh conveyor 2 and the diameter of the metal element wire. For example, assuming that the pulse length p is 0.5 seconds, a decrease in the sensitivity of the photoelectric switch 4 is reliably detected, and its malfunction is prevented.

(Effect of the Invention) As described above, according to the present invention, the gate circuit to which the output signal of the photoelectric switch is input and the metal wire of the wire mesh conveyor shorter than the pulse length of the output signal from the device under test are provided. By providing a photoelectric switch sensitivity detection circuit including a gate control circuit that outputs a gate signal controlled to a pulse length to the gate circuit, the sensitivity of the photoelectric switch is reduced and the pulse length of the output signal is reduced by the wire mesh conveyor. Since an alarm signal is output at a pulse length equal to or less than the gate signal corresponding to the detection of the metal element wire, the problems of the related art are effectively solved, a decrease in the sensitivity of the photoelectric switch is easily detected, and the malfunction thereof is prevented. This has the effect of improving the reliability.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of the present invention, FIG. 1A is a block diagram thereof, FIG. 1B is a waveform diagram of the gate signal of FIG. 1A, and FIG. FIG. 3 is a schematic configuration diagram of a land re-monitor. 4 ... photoelectric switch, 8 ... photoelectric switch sensitivity detection circuit, 9 ... gate control circuit, 10 ... gate circuit, a ... output signal, b ... gate signal, c ... alarm signal, d ... Object detection signal.

Claims (1)

(57) [Claims] 1. A radiation detector provided opposite to a wire mesh conveyor for measuring radioactive contamination of an object transported by the wire mesh conveyor, and detecting the transport of the object to be measured within a required sensitivity range. In a land re-monitor having a photoelectric switch, a gate circuit to which an output signal of the photoelectric switch is input, and a gate signal controlled to a pulse length by a wire of the wire mesh conveyor shorter than a pulse length of an output signal by the device under test. A gate control circuit that outputs a signal to the gate circuit, wherein the sensitivity of the photoelectric switch is reduced and the pulse length of the output signal is less than or equal to the pulse length of the gate signal corresponding to the wire detection of the wire mesh conveyor. A land re-monitor comprising a photoelectric switch sensitivity detection circuit that outputs a signal.