Purpose and composition of devices DP-22V and DP-24

Sets of individual dosimeters DP-22V and DP-24 , with direct-reading pocket dosimeters DKP-50A, designed to control the exposure doses of gamma radiation received by people when working in areas contaminated with radioactive substances or when working with open and closed sources of ionizing radiation.

A set of dosimeters DP-22V ( Fig. 11.) consists of a charger 1 type ZD-5 and 50 individual pocket dosimeters directly showing 2 types DKP-50a. Unlike DP-22V, the set of dosimeters DP-24 (Fig. 11, b) has five dosimeters DKP-50A.

Charger 1 is intended for charging DKP-50A dosimeters. In the ZD-5 case, the following are measured: a voltage converter, a high-voltage rectifier, a potentiometer-voltage regulator, a light bulb for illuminating the charging socket, a micro-switch and batteries.

On the top panel of the device are: potentiometer knob 3, charging socket 5 with a cap 6 and battery compartment cover 4. Power is supplied from two dry cells of the 1.6-PMC-U-8 type, which ensure continuous operation of the device for at least 30 hours at a current consumption of 200 mA . The voltage at the output of the charger is continuously adjustable within ou480 to 250 V.

Direct-reading pocket dosimeter DKP-50A is designed to measure exposure doses of gamma radiation. Structurally, it is made in the form of a fountain pen (Fig. 12). The dosimeter consists of a duralumin housing 1, which contains an ionization chamber with a capacitor, an electroscope, a reading device and a charging unit.

The main part of the dosimeter is a small-sized ionization chamber 2, to which a capacitor 4 with an electroscope is connected. The outer electrode of the camera-capacitor system is a duralumin cylindrical body 1, the inner electrode is an aluminum rod 5. The electroscope forms a curved part of the inner electrode (holder) and a platinized sighting thread (movable element) glued to it 3. In the front of the case there is a reading device – a microscope with 90x magnification, consisting of an eyepiece 9, an objective 12 and a scale 10. The scale has 25 divisions (from 0 to 50). The price of one division corresponds to two roentgens. The scale and eyepiece are fixed with a shaped nut.

In the back of the case there is a charging part, consisting of a diaphragm 7 with a movable contact pin 6. When pressed, pin 6 closes with the internal electrode of the ionization chamber. When the load is removed, the contact pin by the diaphragm returns to its original position. The charging part of the dosimeter is protected from contamination by a protective frame 8. The dosimeter is attached to a pocket of clothing using holder 11.

Rice. 11. Set of dosimeters DP-22V

Rice. 12. Pocket dosimeter DKP-50A

2.2. The principle of operation of devices DP-22; DP-24

The operating principle of a dosimeter is similar to that of a simple electroscope. In the process of charging the dosimeter, the reticle 3 of the electroscope deviates from the internal electrode 5 under the influence of electrostatic repulsion forces. The deflection of the thread depends on the applied voltage, which, during charging, is regulated and selected so that the image of the target thread is aligned with the zero of the scale of the reading device.

When exposed to gamma radiation on a charged dosimeter, an ionization current occurs in the working volume of the chamber. The ionization current reduces the initial charge of the capacitor and the chamber, and, consequently, the potential of the inner electrode.

The change in the potential measured by the electroscope is proportional to the exposure dose of gamma radiation. Changing the potential of the inner electrode leads to a decrease in the electrostatic repulsion forces between the reticle and the electroscope holder. As a result, the sighting thread approaches the holder, and its image moves along the scale of the reading device. Holding the dosimeter against the light and observing the thread through the eyepiece, you can at any time count the received exposure dose of radiation.

2.3. The procedure for working with devices DP-22 and DP-24

Dosimeter DKP-50A provides measurement of individual exposure doses of gamma radiation in the range from 2 R to 50 R at an exposure dose rate of 0.5 R/h to 200 R/h. Self-discharge of the dosimeter under normal conditions does not exceed two divisions per day.

The DKP-50A dosimeter is charged before going to work in the area of radioactive contamination (gamma radiation effects) in the following order:

– unscrew the protective frame of the dosimeter (cork with glass) and the protective cap of the ZD-5 charging socket;

– turn the charger potentiometer knob to the left until it stops;

– insert the dosimeter into the charging socket of the charger, the backlight of the charging socket and high voltage turn on;

– observing through the eyepiece, slightly press the dosimeter and, turning the potentiometer knob to the right, set the thread to “ 0 ” of the scale, then remove the dosimeter from the charging socket;

– check the position of the thread in the light: its image should be at the “ 0 ” mark, wrap the protective frame of the dosimeter and the cap of the charging socket.

The exposure dose of radiation is determined by the position of the thread on the scale of the reading device. The report must be made with the thread in a vertical position in order to exclude the influence of weight deflection of the thread on the dosimeter reading.

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