RU168002U1 - MONITOR FOR DETECTING MOVING RADIOACTIVE OBJECTS - Google Patents

Abstract

The invention relates to devices for detecting ionizing radiation and can be used to control the movement of radioactive objects on automobile and railway highways. Technical result: the ability to detect radioactive objects in traffic streams with speeds up to 100 km / h. The claimed technical result is achieved due to that a new type of injection scintillation plates is used with holes for the installation of optical fibers located across the plate, in the location of the grooves, which increases the amount of collected scintillation light and, accordingly, provides the ability to detect radioactive objects in traffic streams with high speeds, as well as the fact that it is equipped with an adaptive control system that measures the deviation of the signal frequency from the background value when threshold values are exceeded values, generates the corresponding signal and monitors the operation of the monitor, data archiving and communication with the dispatch computer.

Description

The utility model relates to devices for detecting ionizing radiation and can be used to control the movement of radioactive objects on automobile and railway highways.

The invention is known US 2008067390 A1 (hereinafter "the detector"), which relates to the traditional method of manufacturing detectors for the detection of radioactive objects. The sensitive volume (scintillator) in this detector is made by block polymerization. This is a rather long and laborious process, including the mechanical processing of scintillator blocks (milling, polishing). The collection of light in this case is carried out either directly to the photodetectors (Fig. 5A), or using transparent optical fibers (Fig. 5B, 5C, 5D). There are no grooves or holes in the scintillator. Such a light collection requires high transparency of the scintillator used. This requirement of transparency and, accordingly, light collection efficiency limits the maximum volume of the scintillator in the detector to about 15 liters. In the detector (Fig. 5A), the scintillator volume is 2.5 L, in the detectors (Fig. 5B and Fig. 5C) is 4.2 L and in the detector (Fig. 5D) is about 2.8 L. The detector, due to the fact that it uses a plastic scintillator with a short emission time, is capable of detecting radioactive objects moving at a speed of 20 miles per hour (ie, about 30 km / h) ([0069]). The invention describes the location of the detectors in the portal monitors relative to the monitoring zone ([0071]). It is understood that in order to ensure the necessary dimensions of the control zone in height and width, as well as the necessary sensitivity of the portal monitor, several detectors are included in its composition. This entails a significant increase in cost, since each detector is equipped with two photodetectors with appropriate electronics, power systems, etc.

Known portal for the detection of radioactive objects in traffic streams (patent RU 86322). Its design uses a large sensitive

scintillator area. This is achieved by the fact that

- an assembly of scintillation plates made according to original technology by injection molding on injection molding machines is used as a sensitive element;

- as a light-collecting and light-conducting element, a spectroscopic optical fiber (hereinafter referred to as optical fiber) is used;

- the optical fiber is laid in grooves with a depth of 2.5 mm along the entire length of the scintillation plate with a step of 10 mm.

A disadvantage of the known device is the ability to detect radioactive objects in traffic streams with speeds of up to 60 km / h.

The known device does not allow to detect radioactive objects in traffic streams with speeds of more than 60 km / h.

The technical result of the claimed utility model: the ability to detect radioactive objects in traffic streams with speeds of up to 100 km / h.

The essence of the utility model is illustrated by drawings.

In FIG. 1 shows a structural diagram of the proposed monitor for detecting moving radioactive objects, where 1 is the detecting part (sensitive element and photodetectors), 2 is the voltage multiplier for photodetectors, 3 is the control system controller, 4 is the sensor that the object crosses the control zone border, 5 is the network video camera 6 - computer, 7 - network hub, 8 - local area network.

In FIG. 2 shows a structural device of the detecting part of the monitor, where 1 is an assembly of scintillator plates with holes for optical fiber; 2 - two photodetectors; 3 - optical fiber.

In FIG. 3 shows a diagram of a voltage multiplier for a photodetector, where 1 is a photodetector; 2 - capacitive diode voltage multiplier; 3 - boost

transformer; 4 - transistor gate; 5 - master generator; 6 - control circuit; 7 - digital-to-analog converter; 8 - amplifier; 9 - a comparator; 10, 11 - voltage stabilizers.

The claimed technical result is achieved due to:

- replacing the assembly of scintillation plates with grooves located along the plate with a sensitive element consisting of an assembly of scintillation plates with holes for installing optical fiber made across the plate, which can significantly reduce the consumption of optical fiber, increase the amount of collected scintillation light, which, accordingly, provides the ability to detect radioactive objects in traffic streams with high speeds;

- sharing a large area monitor and high sensitivity with an adaptive control system.

The sensitive element of the utility model consists of special design scintillation plates made by injection molding. There are pins with a diameter of 5 mm on one side of each plate, and holes of the same diameter are located on the opposite side, which ensures that the plates are fastened to each other according to the principle of “lock” or “LEGO”. The holes for installing the optical fiber are perpendicular (across) the surface of the plate at a distance of 8.9 mm from each other. The size of the scintillation plate is 250 mm × 50 mm × 5 mm.

The manufacture of scintillation plates by injection molding on injection molding machines is technologically advanced and does not require additional machining. As the basis used industrial granular polystyrene. The collection of light is carried out using spectroscopic optical fibers with a diameter of 1 mm passing through the scintillator. These fibers have high transparency (the attenuation length of light is more than 3 m), which ensures uniformity of light collection from large volumes of the scintillator about 15%. In the claimed utility model, the scintillator area is 2 square meters, the volume is 100 l. The sensitivity of the monitor directly depends on the volume of the scintillator.

The light collection efficiency depends on the method of laying the fiber in the scintillator. In the previous version of the monitor (patent RU 86322), the fibers were laid in grooves located on the surface of the scintillation plates. Tests of prototypes of plates showed that the use of holes instead of grooves increase the light collection by 20-25%, ceteris paribus. Therefore, a new mold was made for the production of plates with holes located at a distance of 8.9 mm from each other (design optimum), and a full-scale monitor sample was made using these plates. Tests confirmed the correctness of the choice.

The proposed utility model uses a large-volume plastic scintillator (100 l, 200 cm × 100 cm × 5 cm) and is capable of detecting radioactive objects moving at a speed of up to 100 km / h. This technical result is also facilitated by the sensor that enters the adaptive system when the object crosses the border of the control zone, which, when the vehicle enters the control zone, sends a signal to compare the newly measured frequency with the background frequency that was before this event.

The proposed utility model has two photodetectors (if one of the systems fails, the model remains operational). In the monitor, as photodetectors, photoelectric multipliers (PMTs) are used with a photocathode with a diameter of up to 50 mm and a quantum sensitivity of up to 20% in the wavelength region of 490 nm.

As a power source for the photodetector, a circuit based on the principle of the Cockroft-Walton voltage multiplier with a low-voltage supply of +/- 18 V is used (the block diagram is shown in Fig. 3). Measurements showed that this circuit provides power stability at the level of 10 ^-3 .

Adaptive control system provides:

- monitor health monitoring,

- fixing the entrance of the measured object into the control zone,

- television surveillance of the control zone,

- control of the radiation level of the object,

- the inclusion of an alarm signal in case of exceeding the radiation level of the measured object threshold value,

- regulation of the threshold value,

- data archiving,

- communication with the computer control room.

The adaptive control system includes: a controller, a network video camera, a sensor crossing the boundary of the control zone by an object, a computer, and a network hub.

The controller performs the following functions:

- measuring the frequency of signals from a detecting device,

- control of analog voltage detectors,

- issuing analog voltages to the detectors,

- measurement of ambient temperature,

- record the necessary status signals,

- control of the temperature regime of the unit,

- ADDRESS block addressing,

- computer information transfer,

- issuing a sound signal.

The adaptive system works as follows: a computer evaluates the background level (background frequency) for a certain time before the object passes by the monitor. The accumulation time of the background signal for determining the frequency and the response level are adjustable. After the signal from the intersection sensor about the entrance of the object to the controlled zone, the system measures the new frequency for several seconds. When you save (or decrease due to screening the background radiation by an object) frequency or a slight excess of the frequency, the computer sends a signal to the system operator that there are no radiation sources, and passes the object. If the threshold frequency is exceeded:

- the computer generates an alarm to the operator,

- The computer generates an alarm signal in the control room and records the corresponding video signal from the video camera until the object leaves the controlled area.

In addition, the computer monitors the status of the equipment and maintains a data archive.

Scintillation light occurs when passing through scintillation plates of ionizing radiation from radioactive objects. A photodetector with a high-voltage power source converts light pulses into electrical ones. The comparator cuts off the noise, and the shaper provides a TTL level pulse corresponding to each light flash, i.e. every gamma quantum.

Background frequency from units to tens of kHz is unstable in time. The control system estimates the background level for a certain time before the object passes by the detector. The accumulation time of the background signal and the response level are adjustable.

After a signal about the object entering the controlled area, the system measures a new frequency for one to two seconds. When the frequency is saved (reduced due to screening of the background radiation by the object) or slightly exceeded, a signal of the absence of radiation sources is generated.

If the threshold frequency is exceeded, an alarm signal is generated, the corresponding video signal is recorded until the object leaves the monitored zone. All data is archived.

The technical result of the utility model is ensured by replacing the scintillator plates with more efficient ones in light collection (using plates from an injection scintillator with holes for installing optical fiber at a distance of 8.9 mm from each other) and equipping the monitor with an adaptive control system.

In addition, the use of the claimed utility model, in comparison with known devices, can significantly reduce the consumption of fiber, which reduces the cost of the utility model and, at the same time, ensures the detection of radioactive objects in traffic streams with speeds up to 100 km / h.

Claims (1)

A monitor for detecting moving radioactive objects, characterized in that an assembly of scintillation plates fastened to each other by the principle of “lock” or “LEGO” with holes for installing optical fiber located across the plate at a distance of 8.9 mm is used as a sensitive element from each other, as well as the presence of two photodetectors and an adaptive control system consisting of a controller, a network video camera, an object crossing the border of the control zone, a computer and a network hub.