RU110507U1 - RADIOACTIVE CONTAMINATION DEVICE - Google Patents

Abstract

 1. A device for monitoring radioactive contamination, including beta detectors, gamma radiation detectors, a recording device, characterized in that foswich detectors for combined registration of beta and gamma radiation and recording devices with separation of beta and gamma signal channels are introduced into the device -radiation, while the fosvich detector consists of two scintillation plates with different luminescence times, equal area, 1: 4 thickness ratio, planarly interconnected with a PMT, fixed in a geome an insulating surface center scintillation plates, and in a recording device included separate pulse counting circuit of the beta and gamma channels measuring and automatically compensating for background gamma radiation. ! 2. The device according to claim 1, characterized in that the location of the detectors is made according to the continuous surface of the sensitive part with a maximum (solid) coverage of the contaminated surface. ! 3. The device according to claims 1 and 2, characterized in that the assembly of the beta scintillation and gamma scintillation plates in the fosvich detector is made with the same solid measurement angles.

Description

The invention relates to the field of radiation protection control and measuring devices, namely to stationary devices for radiometric monitoring of surface contamination of personnel, intended to notify visually or by sound, or both, that a certain value exceeds a certain value of the presence of radioactive contamination on the body ( including the face, feet, surfaces of the hands and head), overalls, safety shoes, and other personal protective equipment), as well as measure values in a given range not.

Known stationary signal measuring device for monitoring radioactive contamination of personnel, designed to signal the excess of the established threshold levels of contamination of the skin and clothing with beta-active radionuclides "Installation control RZB-05" (Prospect, Pyatigorsk plant "Impulse").

The installation consists of two stationary detection devices UDZB-03I 350 × 420 × 280 mm and UDZB-04I 500 × 630 × 170 mm and one remote detection unit 140 × 355 × 65 mm, an information processing device. The installation allows you to control the contamination of the hands, feet and, using a remote detection unit, body surfaces and clothing of staff with beta-active radionuclides, as well as the issuance of signals about exceeding or not exceeding the specified level of contamination.

The disadvantages of the known device is that there are only two detectors with a small total area, as a result of which automatic control of contamination is carried out only for arms and legs and there is no possibility of simultaneous control of the surface of the whole body, and manual control using an external detection unit requires a long time and is subjective. measurement process. In addition, the device does not allow measuring gamma radiation, has a narrow range of controlled values of the flux density of β particles, a high threshold for detecting contamination due to the low sensitivity of beta detectors. and does not have automatic gamma background compensation.

Another well-known technical solution is the "Installation of surface pollution control for personnel RZB-204" (Prospectus of the company "RADICO"), designed to control the presence of beta pollution from personnel leaving the controlled access area. This installation has a significantly improved geometry of the location of the detectors compared to the previous analogue, allowing you to cover most of the controlled surface of the body.

The disadvantages of this device are the lack of gamma radiation control and the lack of automatic gamma background compensation.

The closest device of the same purpose to the claimed device according to the totality of signs is the "Installation control RZB-04-04" (Prospect, Pyatigorsk plant "Impulse").

The unit is designed to control the contamination of the skin and clothing of staff with beta-active radionuclides and the issuance of light and sound signals about exceeding or not exceeding the specified level of contamination. Records contamination of the following parts of the body: back of the head, face, shoulder blades, chest, back, stomach, buttocks, left hand, right hand, left calf, right calf, left knee, right knee, left foot, right foot.

The device contains separate beta detectors, gamma detectors located in different places and a recording device.

The disadvantages of the known technical solution adopted for the prototype is that beta detectors control only individual parts of the body and do not allow control to cover the entire surface of the body, which significantly reduces the sensitivity of detection of contamination. Another drawback is the use of only a few gamma detectors located at a distance from the beta detectors having different solid angles and detection efficiency, which does not allow for efficient automatic gamma compensation and reduces the sensitivity of detection of contamination by gamma radionuclides. In addition, separate identification of beta and gamma alarms is not carried out.

The aim of the invention is to increase the accuracy of determining the level of contamination of both beta and gamma-radionuclides, the identification of the type of radiation, the coverage of the control area of the largest possible surface of the human body, reducing the time of monitoring, reducing the dependence of the measured values on the changing gamma background.

The specified task (or the indicated technical result) is achieved by the fact that in the stationary device for monitoring radioactive contamination, which includes beta detectors, gamma radiation detectors and a recording device, phoswich detectors for combined detection of beta and gamma radiation and recording devices with separation are introduced channels of beta and gamma radiation signals, while the fosvich detector consists of two scintillation plates with different emission times, equal area, 1: 4 thickness ratio, plan connected to each other and to a PMT, mounted in the geometric center of the surface of the scintillation plates, and the recording device includes a separate pulse counting circuit for beta and gamma channels for measuring and automatic compensation of background gamma radiation, and the location of the detectors is made according to the solid surface sensitive parts with a maximum (continuous) coverage of the contamination surface being monitored.

Figure 1 shows a General view of the panel fosvich detectors of the installation, from which it can be seen that the design of the proposed detectors allows you to implement a scheme of their location with a continuous sensitive surface and with a maximum solid angle of detection of the contaminated surface of contamination. This is achieved by the fact that the design of the proposed fosvich detectors with a PMT located in the geometric center of the surface of the scintillation plates does not have any protruding elements beyond their lateral contour and allows the installation of detectors close to each other with a minimum non-sensitive area. In this case, the beta-scintillation plate and the gamma-scintillation plate have the same solid angles of measurement, which is essential when automatic compensation of the gamma-ray count of beta particles is introduced.

Figure 2 is a schematic representation of a fosvich detector, consisting of the main nodes:

1) beta scintillation plate,

2) gamma scintillation plate,

3) photomultiplier tube PMT,

4) a recording device with channel separation.

Realization of the necessary functional capabilities of the developed fosvich detector required that the scintillation fosvich detector have two scintillation plates with different luminescence times, equal area and having common optical contact with the PMT. The main requirements imposed on scintillation plates are to allow the separation of beta and gamma radiation when working in mixed fields of ionizing radiation, as well as high light output. In the proposed fosvich detector, the beta-radiation scintillation plate (position 1 in FIG. 1) has a much longer emission time than the gamma-ray scintillation plate (position 2 in FIG. 1). In addition, the ratio of the thickness of the scintillation plates 1: 4 allows to achieve high detection efficiency of both beta and gamma radiation with an optimal value of gamma compensation of the count on the beta channel.

To implement the functionality of the developed fosvich detector, a separate pulse counting scheme for beta and gamma measurement channels and automatic compensation of background gamma radiation is included in the recording device.

Figure 3 shows a functional diagram of a recording device with separation of channels for separate pulse counting by beta and gamma measurement channels and automatic compensation of background gamma radiation, which shows:

1) Fast amplifier

2) Spectrometric amplifier

3) The discriminator of the lower level of the gamma channel

4) The discriminator of the lower level of the channel gamma compensation

5) The discriminator of the lower level of the beta channel

6) Gamma channel pulse selection circuit

7) Gamma compensation pulse selection circuit

8) Beta channel impulse selection circuit

9) Gamma channel match pattern

10) Beta Channel Match Scheme

11) Single gamma channel

12) One-channel beta channel

13) Digital-to-Gamma Converter

14) Digital-to-analog beta channel converter

The pulses from the PMT anode arrive at the fast amplifier (1), where they are amplified with the maximum possible shape preservation and from the output are fed to the inputs of the three discriminators of the lower level of the DND (3,4,5) and the spectrometric amplifier (2). The spectrometric amplifier (2) provides amplification and pulse formation for the analysis of the measured spectra from the output of the OutputA by an amplitude pulse analyzer. The lower level discriminators (DNU) select pulses with an amplitude of a higher value of the reference voltages specified by the digital-to-analog DAC (13, 14) and Voп converters supplied to the DNU reference inputs. From the output of the DNU (3), the pulses are sent to the gamma channel pulse sampling circuit (6), in which short pulses are selected that arise as a result of the interaction of ionizing radiation with a gamma scintillation plate. From the output of DNU (5), the pulses arrive at the beta-channel pulse sampling circuit (8), which selects long-duration pulses resulting from the interaction of ionizing radiation with a beta-scintillation plate. The gamma compensation pulse selection circuit (7) works the same as the gamma channel pulse selection circuit (6), selecting short pulses of short duration and differs in that the pulses to its input come from the DND of the gamma compensation channel (4), which has independent value of the reference voltage Vop. This solution allows you to independently change the sensitivity of the registration of the gamma channel and the amount of gamma compensation by the ability to separately set the values of the reference voltage.

From the outputs of the selection circuits (6, 8), the pulses arrive at the inputs ВХ1 of the corresponding coincidence circuits (9, 10), which transmit pulses to the inputs of the single-vibrator (11, 12) in the absence of inhibit signals at the inputs of ВХ2. The ban signal on VX2 of the gamma channel coincidence circuit (9) arrives during the appearance of a pulse at the output of the beta channel pulse sampling circuit (8), while prohibiting gamma channel counting. The BX2 inhibit signal of the beta channel coincidence circuit (10) is received during the appearance of a pulse at the output of the gamma compensation pulse selection circuit (7), while prohibiting beta channel counting and providing automatic gamma background count compensation while registering gamma quantum beta scintillation plate and gamma scintillation plate. From the outputs of single vibrators (11, 12), pulses of the required duration are fed to the counting inputs CLKg and CLKb of the microcontroller counters and for gating the amplitude pulse analyzer (gamma strobe and strobe beta) when measuring amplitude spectra in the coincidence mode. Thus, this scheme provides a separate count of pulses on the beta and gamma channels of measurement and automatic compensation of the background gamma radiation.

Figure 4 shows the waveforms of the pulses at the input of the separation circuit when the detection device is irradiated with mixed beta and gamma radiation. You can notice that the difference between the spectral components of the pulses is very significant, which allows us to separate them by the duration of the pulses.

The difference in the times of luminescence emission and the recording device with channel separation makes it possible to distinguish the following situations:

- beta particles were completely absorbed by a thin scintillator (1);

- the beta particle retained the energy fraction during the passage of the thin scintillator and was completely absorbed in the gamma scintillator (2);

- the gamma photon was completely absorbed in the gamma scintillator (2);

- the gamma photon was partially absorbed in the beta scintillator and completely absorbed in the gamma scintillator.

Figure 5 shows the amplitude spectra of the source Cs-137, measured in various modes:

- total spectrum from scintillation gamma and beta plates,

- beta spectrum with beta channel momentum control,

- gamma spectrum with gamma channel impulse control.

The shape of the total spectrum recorded by scintillation gamma and beta plates is very complex and is due to the sum of beta and gamma radiation from the Cs-137 source.

On the beta spectrum with beta-channel momentum control, the peak of internal conversion electrons (EEC - 512 keV) and part of the spectrum, which decreases in intensity with increasing electron energy of continuous beta radiation, are clearly manifested. The Compton spectrum from the gamma line (Compton - 662 keV) of the Cs-137 source is visible on the gamma spectrum with control of gamma channel pulses. Thus, the circuit of the recording device with channel separation implements the functions of separating the types of radiation and provides a separate account when the detection device is irradiated with mixed beta and gamma radiation.

Thus, the technical result of the claimed invention can be expressed in the achievement and improvement of the following parameters:

- increasing the sensitivity of R _β to beta radiation: the ratio of the readings of the counting rate of the detector N to the measured quantity A (hours / cm ² * min), R _β = N / A,

- increasing the sensitivity of R _γ to gamma radiation: the ratio of the readings of the counting rate of the detector N to the measured quantity A (1 / Bq), R _γ = N / A,

- increasing the limits of registration of beta radiation with the specified gamma background,

- an increase in the zone of control of the surface of the human body,

- reduction of control time,

- the implementation of a separate gamma or beta alarm in mixed gamma beta radiation fields,

- Improving ergonomics and efficiency in the manufacture and operation.

Claims (3)

1. A device for monitoring radioactive contamination, including beta detectors, gamma radiation detectors, a recording device, characterized in that foswich detectors for combined registration of beta and gamma radiation and recording devices with separation of beta and gamma signal channels are introduced into the device -radiation, while the fosvich detector consists of two scintillation plates with different luminescence times, equal area, 1: 4 thickness ratio, planarly interconnected with a PMT, fixed in a geome an insulating surface center scintillation plates, and in a recording device included separate pulse counting circuit of the beta and gamma channels measuring and automatically compensating for background gamma radiation. 2. The device according to claim 1, characterized in that the location of the detectors is made according to the continuous surface of the sensitive part with a maximum (solid) coverage of the contaminated surface. 3. The device according to claims 1 and 2, characterized in that the assembly of the beta scintillation and gamma scintillation plates in the fosvich detector is made with the same solid measurement angles.