AI Measurement Tools
Using one or another detector, AI measuring instruments (dosimetric instruments) are developed, which are divided into three groups.
The first group includes radiation reconnaissance equipment, which serves to detect radioactive contamination and measure the dose rate of a radioactively contaminated area or from any other source of radiation. These tools include dose rate meters. The measurement results obtained using these means make it possible to assess the degree of potential danger of human exposure to radiation.
The second group includes means that serve to measure the magnitude of absorbed doses of gamma and gamma neutron radiation (dosimetric monitoring devices). These include individual dose meters.
The devices of the third group include means for monitoring radioactive contamination of machinery, equipment, property, people, food, water and other objects. These include dose rate meters and radiometric installations (laboratories).
Portable dose rate meter DP-5V. DP-5V - designed for measuring dose rate over a radioactively contaminated area, as well as for measuring radioactive contamination of various objects by gamma radiation. In addition, it allows the detection of beta radiation. Thus, the device is a means of radiation reconnaissance and dosimetric monitoring.
The gamma radiation dose rate measurement range from 0.05 mR/h to 200 R/h is divided into 6 subranges.
The main relative measurement error of the device under normal climatic conditions (0°C and 760 mm Hg) does not exceed 30%. The device remains operational after exposure to transport shaking with an acceleration of 100 m/s2, or a fall from a height of up to 0.5 m. The device consists of two blocks: a detection unit and a measuring console. The detection unit contains gas-discharge counters GS1 and GS2 of various sensitivity and an amplifier. The measuring panel contains an integrating circuit with a microammeter (pointer measuring device).
The weight of the device with the power supply kit is no more than 3.2 kg.
Portable dose rate meter IMD-1. Designed to measure the exposure dose rate of gamma radiation, as well as to detect b - radiation. Available in two modifications: IMD - 1C (stationary) and IMD - 1P (portable), which differ in the length of the cable between the units and the presence of a network power supply.
The measuring range of the device is from 0.01 mR/h to 999 R/h. divided into two subranges “mR/h” and “R/h”. The “mR/h” sub-range detector (SBM-21 – high sensitivity counter) is located in the detection unit. The “R/h” sub-range detector (SI-38G is a low-sensitivity gas-discharge counter) is located in the measuring console.
The weight of the working set of the device (1P – portable version) is 3.3 kg.
Onboard dose rate meter IMD-21B. Device modifications: on-board, on-board automated, stationary, stationary automated.
The device is installed on ground moving objects and is designed to measure the dose rate of gamma radiation and issue a light signal when dose rate thresholds are exceeded.
Measurement range from 1 to 999 R/h. In this range, 5 dose rate threshold values are set (1.5; 10; 50; 100 R/h), when exceeded, a light signal is given.
The operating speed of the device does not exceed 10 s.
Combined dose rate meter– radiometer IMD-12. Designed to measure:
specific b and a - activity of contaminated food, fodder and water;
surfaces b - contamination of objects;
dose rate g - radiation from radioactively contaminated areas and objects.
The measuring range depends on the type of measurement. For example, when determining specific b - activity from 10 –6 to 10 –3 Ci/kg or from 103 to 107 b - particles/cm2min; when measuring dose rates from 0.1 μR/h to 999 R/h.
Scintillation geological exploration device SRP-68-01.
Designed to determine the activity of rocks during geological exploration. It can also be used to measure the dose rate in emergency situations at radiation hazardous facilities to search for the source of radiation.
The measuring range of the device from 0 to 3000 μR/h is divided into 5 subranges: 0-30, 0-100, 0-300, 0-1000, 0-3000 μR/h.
The measuring device is a pointer, has 2 scales: the upper one has divisions from 0 to 100, the lower one has divisions from 0 to 30.
The device kit includes: detection unit; remote controller; headphones. Detector – scintillation with PMT.
Basic dosimetry task is the detection and assessment of the degree of danger of ionizing radiation for the population under various radiation conditions. Dosimetric instruments are used to:
Detection and measurement of exposure and absorbed radiation dose rates to ensure the life of the population;
Measurements of the activity of radioactive substances, radiation flux density; specific, volumetric, surface activity of various objects to determine the need and completeness of decontamination and sanitization;
Measurements of exposure and absorbed radiation doses in order to determine the working capacity and viability of the population in terms of radiation;
Laboratory measurement of the degree of radioactive contamination of food, water, etc.
Classification The identification of dosimetric devices is carried out according to their purpose, the type of sensors, the measurement of the type of radiation, the nature of the electrical signals converted by the device circuit. Almost all modern dosimetric instruments operate based on the ionization method. The main components of the devices are radiation detectors, which are used to detect radiation; electrical circuit for pulse conversion; measuring or recording devices; current sources.
According to their functional purpose, devices are divided into indicators, radiometers, X-ray meters, and dosimeters. The sensors are gas-discharge and scintillation counters. They measure alpha and beta radiation and small levels of gamma radiation. For more accurate measurements, there are stationary radiometers - DP-100, RUB-01-P6, “Beta-2”, etc. Portable ones include “Luch-2”, which is used for the qualitative and quantitative determination of beta and gamma radiation, as well as radiometer-X-ray meter DP-5A, designed to detect and measure the degree of surface contamination with beta and gamma active substances and measure gamma radiation levels.
Dosimeters. Designed to determine the total radiation dose (exposure or absorbed), or the corresponding dose rates of gamma or x-ray radiation. Ionization chambers, scintillation counters, etc. are used as detectors (sensors). Stationary dosimeters include SPSS-02, SD-1M, etc. Portable dosimeters - SRP-68-01, KID-2, set of dosimeters DP-24, DK-0 ,2, etc. The industry also produces so-called household (pocket) dosimeters designed to measure exposure dose in the air, i.e. working as X-ray meters (“Master-1”, “Horizon”, “Bela-2”, “Sosna”, etc.). They are used in contaminated areas to control background gamma levels and avoid heavy contamination with cesium-137.
Indicators. These are the simplest devices for detecting radiation and roughly estimating the exposure dose rate (radiation level), mainly gamma and beta radiation. The detector is a gas-discharge counter. This group includes the DP-64 indicator-signaling device, the IMD-21 dose rate meter, etc.
X-ray meters. They are designed to measure the dose rate of X-ray or gamma radiation. The measurement range is from hundredths of a roentgen to several hundred roentgens per hour (R/h). Ionization chambers or are used as sensors. These include the X-ray meter DP-3B, “Cactus”, DP-2, etc.
Radiometers(radioactivity meters). They are used to detect and determine the degree of radioactive contamination of surfaces and equipment with alpha and beta particles; flux density or intensity of radioactive radiation; activity of environmental samples.
PERFORMERS:
Fominykh V.I.(topic leader), Oborin A.V., Sebekin A.P., Uryaev I.A.
INTRODUCED by the USSR State Committee for Standards
Member of Gosstandart OK. Isaev
APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee on Standards dated December 29, 1983 No. 6520
Approved by Decree of the State Standard of December 29, 1983 No. 6520, the introduction date is set
from 01.01.85
These guidelines apply to thermoluminescent dosimetric devices (hereinafter referred to as devices) for measuring the exposure dose of X-ray and (or) gamma radiation with photon energies from 10 keV to 3 MeV, as well as the absorbed and (or) equivalent dose of X-ray and (or) gamma - radiation with photon energy from 10 keV to 10 MeV, and absorbed and (or) equivalent dose of beta radiation with particle energy from 20 keV to 3 MeV in muscle tissue equivalent substance (hereinafter referred to as absorbed and (or) equivalent dose) and establishes methods and means of their initial and periodic verification. Technical characteristics of the devices are given in reference appendix 1. Explanations of the terms used in the standard are given in reference appendix 2.
Note. These guidelines can be used when checking radiophotoluminescent dosimetric instruments.
1. VERIFICATION OPERATIONS
1.1. When performing verification, the following operations must be performed:
external inspection (clause 5.1);
testing (clause 5.2);
determination of the main error (clause 5.3).
2. MEANS OF VERIFICATION
2.1. When carrying out verification of the exposure dose of X-ray and (or) gamma radiation, verification dosimetric installations must be used that meet the requirements of GOST 8.087-81.
2.2. When carrying out verification of the absorbed or equivalent dose of X-ray and (or) gamma radiation, verification dosimetric installations must be used that meet the requirements of GOST 8.087-81, equipped with a phantom made of muscle tissue-equivalent substance (hereinafter referred to as the phantom), certified for absorbed and (or) equivalent dose.
Notes:
1. It is allowed to use devices whose basic relative error is equal to or exceeds 8% of the absorbed or equivalent dose; calibration dosimetric installations that meet the requirements of GOST 8.087-81, equipped with a phantom and certified according to the exposure dose in the phantom at the depth specified in Reference Appendix 3, using conversion coefficients from exposure D 0 to absorbed or equivalent D equivalent doses specified in reference Appendix 4. The relationships between exposure, absorbed and equivalent doses in water are given in Reference Appendix 5. An example of calculating the absorbed and equivalent dose based on exposure dose measurements is given in Reference Appendix 6.
2. It is allowed to verify devices intended for individual dosimetric monitoring of IDK, the main error of which is equal to or exceeds 8% for the maximum absorbed dose in a tissue-equivalent substance and for a standardized equivalent dose, using installations equipped with a tissue-equivalent (water) phantom and a standard dosimeter certified according to exposure dose, using conversion coefficients from exposure dose to maximum absorbed or standardized equivalent doses according to PG605-178-81 “Dosimetric devices. Methods for measuring basic parameters".
2.3. When carrying out verification of the absorbed or equivalent dose of beta radiation, exemplary measures of the absorbed dose of beta radiation must be used in accordance with GOST 8.035-82 in the form of beta radiation sources with appropriate absorbers. Characteristics of sources and sinks are given in reference annexes 3 and 7.
2.4. When performing verification, a barometer in accordance with GOST 23696-79, a thermometer in accordance with GOST 112-78, and a psychrometer in accordance with GOST 6353-52 are used.
3. CONDITIONS OF VERIFICATION AND PREPARATION FOR IT
3.1. When performing verification, the following conditions must be met: ambient temperature (20 ± 5) °C; relative air humidity (60 ± 15)%: atmospheric pressure (101.3 ± 4) kPa; mains supply voltage (220 ± 4.4) V; frequency 50 Hz.
Note. It is allowed to carry out verification at other values of temperature, pressure and relative humidity of the environment, if the verification results are brought to normal conditions in accordance with the requirements of the regulatory framework technical documentation(hereinafter referred to as NTD) for a specific type of device.
3.2. The total background of ionizing radiation during verification should not exceed 0.01 of the value of the measured value corresponding to the lower limit of the measurement range of the device being tested.
3.3. The verification tools and the device being verified are prepared for operation in accordance with the requirements of the regulatory and technical documentation for them.
3.4. It is allowed in certain justified cases, in agreement with the Gosstandart authorities, to carry out verification of devices based on exposure dose in beta radiation fields if there is a methodology that complies with GOST 8.042-72.
4. SAFETY REQUIREMENTS
4.1. Safety requirements during the preparation and verification of devices must comply with GOST 12.2.007-75, GOST 12.2.018-76, GOST 12.0.004-79, “Rules for the technical operation of consumer electrical installations and safety rules for the operation of consumer electrical installations,” approved by the State Energy Supervision Ministry of Energy USSR, the current basic sanitary rules for working with radioactive substances and other sources of ionizing radiation (OSP 72/80) and the current radiation safety standards (NRB-76).
4.2. Personnel constantly and directly working to verify devices must:
know the methodology for checking instruments and instructions for working with the instruments being verified;
pass the test in safe methods work in the prescribed manner and be allowed to work with sources of ionizing radiation;
undergo a medical examination once a year.
4.3. The area of the working radiation beam must be fenced and marked with radiation hazard signs in accordance with GOST 17925-72.
4.4. When working with beta radiation sources, use protective screens plexiglass, glasses and other personal protective equipment.
4.5. Radiation monitoring to ensure safety and monitoring of personnel exposure is carried out by the Radiation Safety Service in accordance with OSP 72/80.
5. VERIFICATION
5.1. Visual inspection.
5.1.1. At external inspection it must be established: the presence of elements of the device kit and the technical documentation for it; certificates of previous verification; markings of thermoluminescent detection units (hereinafter referred to as detection units):
absence of contamination of the detectors and the heating element of the measuring unit; mechanical damage to detectors, detection units and measuring units.
5.2. Testing.
5.2.1. During testing, the functionality of the measuring unit of the device is checked in accordance with the technical documentation for the device and the required operating mode of the measuring unit is set using a light source.
5.3. Determination of the main error.
5.3.1. During the initial verification, all detection units included in the device are checked. During periodic verification, when the number of detection units is less than 20, all detection units are checked: from 20 to 200 - 20 detection units, and more than 200 - 10% of the total number of detection units of the same type. Detection blocks are selected randomly.
5.3.2. Each detection unit being verified is sequentially placed at the same point in the ionizing radiation field and irradiated with a dose corresponding to 0.1 and 0.7 of the upper limit of each measurement subrange. For single-range devices, the detection unit is also irradiated with a dose corresponding to ten times the value of the lower measurement limit.
Notes:
1. It is allowed to verify devices with a basic relative error of more than 15% on calibration dosimetric installations that meet the requirements of GOST 8.087-81, not equipped with a tissue-equivalent phantom, certified for exposure dose using the conversion coefficients from exposure dose to absorbed dose specified in the technical documentation for the device .
2. Simultaneous irradiation of a group of detection units is allowed if the uniformity of the radiation field is ensured in accordance with GOST 8.087-81.
5.3.3. When calibrating the exposure dose, as well as the absorbed and equivalent doses of devices intended for environmental control, their detection units are irradiated in free air, in the absence of a phantom.
5.3.4. When calibrating the absorbed and equivalent doses of devices intended for individual dosimetric monitoring, their detection units are irradiated on the front surface of the phantom or in free air, bringing the results to the specified irradiation conditions by introducing appropriate correction factors into the measurement results. Irradiation schemes for detection units are given in Reference Appendix 8.
5.3.5. When calibrating medical devices for absorbed and equivalent doses, their detection units are irradiated in a phantom at the depth specified in Reference Appendix 3.
5.3.6. The irradiation time of the devices is chosen so that the additional error of the measured value, due to the finite time of disappearance and appearance of the ionizing radiation field, does not exceed 0.5%.
5.3.7. The main error of the device being verified is determined by comparing the readings of the device being verified from each detection unit from the random sample volume with the value of the exposure, absorbed or equivalent dose of radiation created in the verification dosimetric installation.
5.3.8. The relative basic error of the device (in percent) is determined by the formula
Where? o - confidence relative error of the standard measuring instrument with confidence probability R= 0.95; D 2 o,pr - maximum value from D 2 o,pr,1.
Where D- dose value measured by the device being verified for each detection block from a random sample; D 0 - dose value according to the certificate for a standard calibration dosimetric installation or obtained using a standard device.
5.3.9. The basic error of the device should not exceed the limits of the permissible basic error for this type of device.
5.3.10. If the basic error of the device for at least one detection block out of every 20 random sampling blocks exceeds the limit of the permissible basic error specified in the technical documentation for a device of a particular type, then the operations according to paragraphs. 5.3.1 - 5.3.3. repeat for all detection units included in the device kit. Detection units, during measurements with which the main error of the device exceeds the limit of the permissible main error specified in the technical specifications for a device of a specific type, are not allowed into circulation. If more than 50% of the thermoluminescent detection units are removed, the device is considered to have failed verification. In this case, the serviceability is checked in accordance with the technical documentation for a device of a specific type of measuring unit, and if it is in good working order, the device is equipped with a new set of detection units and re-submitted for verification.
5.3.11. The verification results are recorded in a protocol, the form of which is given in the mandatory Appendix 9. The protocol contains information about the dosimetric device, the dosimetric verification device or source, verification conditions and measurement results.
6. REGISTRATION OF VERIFICATION RESULTS
6.1. Positive results of the state primary verification of dosimetric devices are formalized by an entry in the passport, certified by the signature of the verifier.
6.2. Positive results of periodic verification of dosimetric instruments are formalized by issuing a certificate of the established form. The reverse side of the certificate is given in mandatory Appendix 9.
6.3. Dosimetric devices that do not meet the requirements of these methodological instructions, are not released into circulation and they are issued a notice of unsuitability indicating the reasons.
ANNEX 1
Information
Thermoluminescent dosimetric devices
|
Detector |
Range |
Basic error, % |
||
|
KDT-1 (UPF-01) “Pakhra” |
2,58 10 -4 - 25,8 |
25 (with a value less than 2.58 10 -3 C/kg) 15 (at a value of more than 2.58 10 -3 C/kg) |
||
|
LiF - single crystal |
5,16 10 -6 - 0,258 |
|||
|
2,58 10 -6 - 25,8 |
40 (with a value less than 2.58 10 -5 C/kg) 20 (if the value is more than 2.58 10 -4 C/kg) |
|||
|
Glass IS-7 |
1,29 10 -4 - 0,258 |
|||
|
For gamma radiation LiF, CaF 2, for beta radiation - indicator |
2,58 10 -5 - 0,258 |
± (10 + 3/A), where A- measured quantity |
||
|
Includes AKB "Seyval" |
2,58 10 -5 - 0,258 |
|||
|
CaSO 4 , ( D V) LiF |
2,58 10 -7 - 25,8 |
10 -3 - 1 10 5 |
||
|
VA-M-30 (GDR) |
LiF (powder) |
2,58 10 -5 - 0,258 |
||
|
VA-M-164 (GDR) |
2,58 10 -5 - 0,258 |
|||
|
VA-M-65 (Czechoslovakia) |
7,74 10 -4 - 0,258 |
|||
|
TLD-750 (Poland) |
2,58 10 -6 - 2,58 |
|||
|
TLD-04TS (VNR) |
LiF, CaF 2, CaSO 4 ( D T) |
|||
|
"Pelle" (VNR) |
CaSO4 ( T m) |
|||
APPENDIX 2
Information
Terms and explanations
1. Thermoluminescent detector (TLD) - according to GOST 14105-76.
2. Thermoluminescent detection unit - a thermoluminescent detector or a set of thermoluminescent detectors placed in a package (cassette, capsule, shell) consisting of elements: housing, correction filters, etc.; a distinctive index (number, set of holes, code, etc.) is indicated on the package body.
3. Thermoluminescent dosimetric device (TLD device) - a set of thermoluminescent detection units and devices for measuring and recording dosimetric information when lighting thermoluminescent detectors, for preparation for measurements (loading, sealing, annealing), a control light source and a radioactive control source.
4. Phantom - a device that simulates a biological object and contains a tissue-equivalent substance sufficient to scatter the radiation beam.
5. Muscle tissue-equivalent substance - a substance that is equivalent in interaction for a given type of ionizing radiation to biological tissue according to GOST 18622-79. For X-ray and gamma radiation, the recommended substance by the BIPM is water.
6. Random sample volume - the number of thermoluminescent detection units randomly selected from the set and subjected to verification.
7. Total background - the value of the absorbed (equivalent) dose during the verification period, caused by extraneous external sources of ionizing radiation.
APPENDIX 3
Information
Characteristics of phantoms recommended for use when calibrating devices based on absorbed radiation dose
1. X-ray and gamma radiation.
1.1. Water phantom with dimensions: 300×300×200 mm.
* Half attenuation layer (HWL) less than 3 mm.
It is allowed to use a solid-state phantom included in the kit of the clinical dosimeter 27012, and, as an equivalent of water 0.07 mm thick, a polyethylene film with a surface density of 70 g/m 2 when the voltage on the tube is less than 50 kV.
2. Beta radiation.
When measuring with beta radiation sources, solid-state phantoms made of polyethylene or organic glass in the form of sheet materials with a surface density of 5 to 3000 g/m 2 are used.
APPENDIX 4
Information
Transition coefficient values f from the exposure dose measured in the phantom to the absorbed dose in water at different energies of X-ray and gamma radiation
|
Radionuclide |
Half Attenuation Layer |
Approximate value of effective energy, keV |
GR · kg Cl -1 |
APPENDIX 5
Information
Relationships between exposure, absorbed and equivalent doses in water, determined under identical conditions at electronic equilibrium
1. The absorbed dose of photon radiation by exposure dose and by the exposure dose rate of photon radiation in gray (Gy) is determined by the formulas
D air = D 0 e, (1)
where e = 33.85 J/C is the average pricing energy in the air; D 0 - exposure dose, C/kg;
D air = P air t. (2)
Absorbed dose rate in air R air in grays divided by second (Gy/s) is determined by the formula
R air = R 0 e, (3)
Where R 0 - exposure dose rate, A/kg; t- time, s;
D water =D" 0 f, (4)
Where D water - absorbed dose in water, Gy; D" 0 - exposure dose at depth d in a water phantom, C/kg (see reference Appendix 3); f- coefficient of transition from exposure dose to absorbed dose in water (see reference Appendix 4).
2. Equivalent photon radiation dose by exposure dose and photon radiation exposure dose rate D eq in sieverts (Sv) under the same conditions is determined by the formula
D eq =D 0 f K (5)
Where TO- quality factor for x-ray or gamma radiation.
Note. Quality factor for X-ray or gamma radiation TO applicable in the case where the spectral composition of the radiation is unknown. In all other cases, the quality factor is used TO, averaged over the LET spectrum in accordance with NRB-76.
D eq = P eq t. (6)
Equivalent dose rate R eq (in Sv/s) is determined by the formula
P eq =P 0 f K. (7)
3. The equivalent dose of beta radiation (in Sv) is determined by the formula
D eq = D b TO, (8)
Where D b is the absorbed dose of beta radiation in the phantom behind a layer of tissue-equivalent substance with a surface density of 70 g/m2, Gy.
Note. For photon and electron radiation TO= 1 (PG 602-4-82 “GSI. Quality factor of ionizing radiation”).
APPENDIX 6
Information
Example of calculating absorbed and equivalent dose based on exposure dose measurements
Let the exposure dose of X-ray radiation with an effective photon energy of 29 keV at a depth of 0.07 mm of a tissue-equivalent phantom be equal to R 0 = 2,58 10 -4 C/kg. Using the value e = 33.85 J/C, using formula (1) of Appendix 5, you can determine the absorbed dose in the air D air = 2.58 10 -4 33.85 = 0.873 10 -2 Gr.
Knowing the value of the coefficient f= 33.7 Gy kg/C given in reference Appendix 4 for an effective energy of 29 keV, and the value of the quality factor TO= 1, using formulas (4) and (5) of Appendix 5, we determine the absorbed dose in water and the equivalent dose D water = 2.58 10 -4 33.7 = 0.869 10 -2 Gy; D eq = 2.58 · 10 -4 · 33.7 1 = 0.869 10 -2 Sv.
APPENDIX 7
Information
Characteristics of beta radiation sources recommended for use as exemplary measures of the absorbed dose of beta radiation when calibrating instruments
APPENDIX 8
Information
Irradiation schemes for thermoluminescent detection units when checking devices for absorbed and equivalent dose of X-ray and gamma radiation
In the pictures: 1 - radiation source; 2 - diaphragm; 3 - thermoluminescent detection units; 4 - a plexiglass phantom with water (from the IDMD-1 device); 5 - plexiglass holder
APPENDIX 9
Mandatory
Form of the reverse side of the verification certificate
|
1. Verification of the thermoluminescent dosimetric device was carried out using a verification dosimetric installation of type ____________________ ______________________ (or using a reference radiation source at based on the radionuclide ___________). 2. Irradiation conditions _____________________________________________________ (without collimator, contact, standard __________________________ collimator) 3. When checking the device, the detection units were located ___________________ (in the air, in a phantom: water, solid-state type...) ___________________________________________________________________________ (on the front surface of the phantom, at a depth... mm) 4. The readings from the reference light source on the ________________ scale are ______________________. 5. Relative main error of a thermoluminescent dosimetric device in the range of ________________ values of the exposure (absorbed, equivalent) dose of _________________ radiation, equipped with a set of thermoluminescent detection units of type _____________________________ based in the amount of __________ pcs. (in a cassette, without a cassette), does not exceed the value specified in the technical documentation for the device - % ( R = 0,95). |
|
1. Verification operations. 1 2. Verification means. 2 3. Verification conditions and preparation for it. 2 4. Safety requirements. 3 5. Conducting verification. 3 6. Registration of verification results. 5 Appendix 1. Thermoluminescent dosimetric devices... 5 Appendix 2. Terms and explanations. 5 Appendix 4. Transition coefficient values f from the exposure dose measured in the phantom to the absorbed dose in water at different energies of x-ray and gamma radiation. 6 Appendix 5. Relationships between exposure, absorbed and equivalent doses in water, determined under identical conditions at electronic equilibrium. 7 Appendix 6. Example of calculating absorbed and equivalent dose based on exposure dose measurements.. 8 Appendix 7. Characteristics of beta radiation sources recommended for use as exemplary measures of the absorbed dose of beta radiation when calibrating instruments. 8 Appendix 8. Irradiation schemes for thermoluminescent detection units when checking devices for absorbed and equivalent dose of X-ray and gamma radiation. 8 |
Portable dose rate meter DP-5V . Designed to measure dose rate over a radioactively contaminated area, as well as to measure radioactive contamination of various objects by gamma radiation. In addition, it allows the detection of beta radiation. Thus, the device is a means of radiation reconnaissance and dosimetric monitoring.
The gamma radiation dose rate measurement range from 0.05 mR/h to 200 R/h is divided into 6 subranges with measurement limits:
I. subrange - 5…200 R/h,
II. sub-range - 500…5000 mR/h,
III. sub-range - 50…500 mR/h,
IV. sub-range - 5…50 mR/h,
V. subrange - 0.5…5 mR/h,
VI. subrange - 0.05…0.5 mR/h.
The dose rate is counted during measurements on 1 subrange on the lower scale, and on all other subranges - on the upper scale, followed by multiplication by the corresponding subrange multiplier.
The main relative measurement error of the device under normal climatic conditions (0 0 C and 760 mm Hg) does not exceed 30%. The device remains operational after exposure to transport shaking with an acceleration of 100 m/s 2 , falling from a height of up to 0.5 m. The device is powered by three 1.6 PNC elements (one of them for illuminating the scale). One set of elements ensures continuous operation time of up to 55 hours. The technical life of the device is at least 2500 hours. The service life is at least 15 years. Longest time establishing a reliable value of the device readings does not exceed 45 s. Warm-up time of the device is at least 1 minute.
The device consists of two blocks: a detection block and a measuring panel. The detection unit contains gas-discharge counters GS1 and GS2 of various sensitivity and an amplifier. The measuring panel contains an integrating circuit with a microammeter (pointer measuring device).
The weight of the device with the power supply kit is no more than 3.2 kg.
Portable dose rate meter IMD-1. Designed to measure the exposure dose rate of gamma radiation, as well as to detect radiation. Available in two modifications: IMD - 1C (stationary) and IMD - 1P (portable), which differ in the length of the cable between the units and the presence of a network power supply.
The measuring range of the device from 0.01 mR/h to 999 R/h is divided into two subranges “mR/h” and “R/h”. The “mR/h” sub-range detector (SBM-21 - high sensitivity counter) is located in the detection unit. The “R/h” sub-range detector (SI-38G - low-sensitivity gas-discharge counter) is located in the measuring console.
The operating speed of the device is from 6 to 60 s in the “mR/h” subrange, and from 1.5 to 15 s in the “R/h” subrange, depending on the dose rate.
The main relative error of the device is no more than + 25% (only at values of 0.1 mR/h and 0.1 R/h, 0 0 C and 760 mm Hg).
The device is resistant to repeated mechanical shocks with an acceleration of 150 m/s 2 .
The device is powered by 4 elements of type A-343; from a DC power supply or batteries with a voltage of 11 to 30V via a power supply; from the network alternating current via the power supply. The operating time of one set of A-343 elements is at least 100 hours.
Resource - 10,000 hours. Service life before write-off - 12 years.
The composition of the working device of the kit: detection unit (IMD - 1-1), measuring panel (IMD - 1-3), power supplies IMD - 1-2 (from the on-board network), IMD - 12-6 (from alternating current). Readings are taken on the measuring console using a digital display. The device has an audible alarm.
The weight of the working set of the device (1P - portable version) is 3.3 kg.
Onboard dose rate meter IMD-21B. Device modifications: on-board, on-board automated, stationary, stationary automated.
The device is installed on ground moving objects and is designed to measure the dose rate of gamma radiation and issue a light signal when dose rate thresholds are exceeded.
Measurement range from 1 to 999 R/h. In this range, 5 dose rate threshold values are set (1.5; 10; 50; 100 R/h), when exceeded, a light signal is given.
The operating speed of the device does not exceed 10 s.
The main relative error is:
P = 20 R and - 1%
where P and is the value of the measured quantity.
Power supply from battery voltage 12V and 24V.
Operating life - 5000 hours. Meter life - 25000 hours.
The device includes 2 blocks: a detection block (detector - ionization chamber), a measurement and reading block. The countdown is carried out using a digital display.
The weight of the on-board version kit is 7 kg.
Combined dose rate meter - radiometer IMD-12. Designed to measure:
specific and - activity of contaminated food, fodder and water;
surfaces - contamination of objects;
dose rate - radiation from radioactively contaminated areas and objects.
The measuring range depends on the type of measurement. For example, when determining specific activity from 10 - 6 to 10 - 3 Ci/kg or from 10 3 to 10 7 - particles/cm 2 min.; when measuring dose rates from 0.1 μR/h to 999 R/h.
The measurement error of the device may be:
specific activity of radionuclides in food, fodder, water up to 80% relative to radiation from a strontium-90 + yttrium-90 source;
surfaces - contamination no more than 50% relative to - radiation source strontium-90 + yttrium-90;
gamma radiation dose rate is not more than 25% relative to cesium-137 radiation.
The response time also depends on the type of measurement and can be up to 1000 s when measuring activity and up to 15 s when measuring dose rate.
The weight of the set in storage boxes is about 66 kg.
IMD-12 set includes:
measuring console IMD-12-1 (with digital display);
gamma radiation detection unit IMD-12-2 (detectors - gas-discharge counter SBM-21 and GS SI-38G);
detection unit IMD-12-3 (detector - gas-discharge counter SBM-19);
detection unit IMD-12-4 (scintillation detector with PMT);
power supply unit IMD-12-6 (from AC and DC mains).
The detection units are alternately connected to the measuring console depending on the purpose of the measurement (determination of - activity, - activity, radiation dose rate).
Scintillation geological exploration device SRP-68-01.
Designed to determine the activity of rocks during geological exploration. It can also be used to measure the dose rate in emergency situations at radiation hazardous facilities to search for the source of radiation.
The measuring range of the device from 0 to 3000 μR/h is divided into 5 subranges: 0-30, 0-100, 0-300, 0-1000, 0-3000 μR/h.
The measuring device is a pointer, has 2 scales: the upper one has divisions from 0 to 100, the lower one has divisions from 0 to 30.
The device kit includes: detection unit; remote controller; headphones. The detector is scintillation with PMT.
The device is powered by nine 343 elements.
The weight of the working kit is 3.7 kg.
Dose rate meters used by the public.
In recent years, especially after the Chernobyl disaster, the population began to show increased interest in the radiation situation. At the same time, we should not forget that the population is exposed to radiation from low-intensity and man-made background radiation sources.
The value of natural background radiation varies depending on the area or area of the city and is generally 0.05 - 0.2 μSv/h (5-20 μrem/h). In anomalous places where granite masses, soils or water sources containing elevated concentrations of natural radionuclides pass close to the surface, near houses lined with granite, it reaches 0.4 μSv/h (40 μrem/h).
The radiation level corresponding to the natural 0.1 - 0.2 μSv/h (10-20 μrem/h) is considered normal. Levels above 0.6 μSv/h (60 μrem/h) are considered elevated. The population should be guided by these values when using household appliances.
If the dose rate exceeds 1.2 µSv/h (120 µrem/h), it is recommended to move away from the area or stay there for no more than six months per year.
If the dose rate exceeds 2.5 µSv/h (250 µrem/h), stay should be limited to three months per year.
If 7 µSv/h (700 µrem/h) is exceeded - one month.
Household appliances for the population are a special class of devices designed for the population to assess the radiation situation on the ground, in residential and working premises and other places. They can assess contamination of food and water. In this case, the assessment of radioactive contamination (specific or volumetric activity) of food and water is carried out by direct measurement at a distance of 1-5 cm from the object under study with a mass of at least 1 kg or a volume of at least 1 liter based on the difference in the measurement results of radiation from the object and the radiation fund.
Background radiation should not exceed 0.1-0.2 μSv/h (10-20 μR/h).
Measuring readings when measuring food and water up to a level of 3.7 kBq/kg (10 - 7 Ci/kg, Ci/l) corresponds to approximately 10-15 µR/h and vice versa.
If the level of 3.7 kBq/kg, corresponding to radioactive contamination of food products, is exceeded, it is recommended to refuse food consumption or limit consumption to half the normal diet.
To solve these problems, dozens of dosimetric instruments have currently been developed for the population, of which the most selected successful models and their serial production was mastered. The most successful of them are devices of the DRG-0.1-T “Bella” type (“Bella”, “Sosna”, “Raton”, DBG-06T, RKSB-104). The range of their measurements, depending on the type, reaches 10,000 µR/h (“Bella”, “Jupiter”, “Sosna” - from 10 to 10,000 µR/h; IMD-70 - from 20 to 10 5 µR/h).
They use from one to four SBM-20 gas-discharge counters as detectors. Power is supplied from elements of the Krona type, A-316. The continuous operation time from one set of power supplies ranges from 100 to 500 hours.
The time for collecting information (measurement time) generally does not exceed 25-60 s. The weight of the devices is within 250-400 g.
Dose meter ID-1 designed to measure absorbed doses - and mixed - neutron radiation.
The device kit includes ten ID-1 dose meters and a ZD-6 charger, which are placed in a special case.
Structurally, the dose meter ID-1 is made in the form of a fountain pen with a metal body. Mounted inside the case are: an ionization chamber with a volume of about 1 cm 3 (detector), a microscope, a scale, an electroscope, and an additional capacitor.
The charger is used to charge the ionization chamber and the dose meter capacitor. The charger uses 4 piezoelectric elements as a power source. In a charged dose meter, the electroscope filament is set to “0” on the scale.
The operating principle of ID-1 is that when it is exposed to ionizing radiation, ions are formed in the volume of an ionization chamber charged to a certain voltage, which, under the influence of an electric field, acquire directional movement and, upon reaching the electrodes, are neutralized. As a result, the charge of the camera and the charge on the additional capacity are reduced by an amount proportional to the radiation dose. The electroscope thread moves along the scale and shows the value of this dose (which is why the dosimeter is called direct-reading) in rads. The measurement range of absorbed doses is from 20 to 500 rad.
The main relative error of the device is 20% in the range from 50 to 500 rad. The convergence of measurement readings when repeatedly irradiated with the same dose is 4%.
The average failure-free operation time of the set is no less than 5000 hours. Service life is no less than 15 years. The weight of the kit in the case is 2 kg, the weight of the dosimeter is 40 g.
Set individual dosimeters DP-22V (DP-24) designed for measuring individual doses of gamma radiation using pocket direct-reading dosimeters DKP-50A (similar in design to ID-1 dose meters). The DP-22V (DP-24) set includes 50 (5) individual dosimeters DKP-50A and a charger ZD-5, which are stored and transported in a shipping box. The operating principle of the DKP-50A dosimeter does not differ from the operating principle of ID-1.
The measurement range of DKP-50A is from 2 to 50 R. The error is 10%.
Nutrition charger carried out from two sources 1.6ПМЦ-У-8. The operating time of one set of power sources is 30 hours. The weight of the dosimeter is 30 g, the weight of the set is 5.6 kg.
Set of dose meters ID-11 designed to measure absorbed doses and mixed neutron radiation for the purpose of primary diagnosis of the severity of radiation injuries.
The standard set includes 500 pcs. ID-11 dose meters (detectors) and measuring device.
The dosimeter uses a silver-activated aluminophosphorus glass plate as a detector.
Operating principle of ID-11. When the detector is exposed to radiation, luminescence centers are formed in it, the number of which is proportional to the absorbed dose. When the detector is illuminated with ultraviolet light (in the IU-1 measuring device), the centers luminesce in orange with an intensity proportional to the absorbed dose, which is recorded in the measuring device.
The basis of the measuring device is a photometric unit, consisting of a loading device of a sealed compartment with a FEU-84, an ultraviolet light lamp LUF-4 and four light filters.
The range of measurements of the absorbed dose by the device is from 10 to 1500 rad.
Measuring device with a digital readout of the measured dose value. Its warm-up time before measurements is 30 minutes. Continuous operation time is 20 hours. The dose measurement time of one ID-11 does not exceed 30 s.
The main relative measurement error does not exceed 15% when measuring at least 6 hours after irradiation.
The detector has the ability to accumulate a dose during repeated irradiation and maintain it for at least 12 months. and allows multiple dose measurements with an accuracy not exceeding the main error.
The failure-free operation time of IU-1 is 1000 hours, its technical life is 10,000 hours. The weight of IU-11 does not exceed 23 g, IU-1 - 18 kg.
Set of thermoluminescent dosimeters KDT-02M.
Designed to measure exposure dose and indicate radiation. Several modifications of the kit are available: KDT-02M, KDT-02M-01, KDT-02M-02.
The kit includes: a set of dosimeters DPG-02, DPG-03 and DPS-11; thermoluminescent conversion device UIF-02M, detector irradiator and a set of plates.
The DPG-02 and DPS-11 dosimeters include three polycrystalline detectors based on lithium fluoride. The DPS-11 dosimeter differs from the DPG-02 dosimeter in that it (DPS-11) has a window covered with foil for registration of particles.
The DPG-03 dosimeter includes 3 polycrystalline detectors based on magnesium borate.
The detectors are tablets with a diameter of 5 mm and a thickness of 0.9 mm.
Depending on the complete set of supplies, the device may include:
the KDT-02M set includes 100 dosimeters DPG-02, DPG-03, DPS-11;
set KDT-02-01 - 1000 dosimeters DPG-03, 200 dosimeters DPS-11;
the KDT-02M-02 set includes 1260 DPG-03 dosimeters and 260 DPS-11 dosimeters.
The principle of operation of KDT-02M is the same as that of ID-11, only the excitation of the accumulated energy in the detectors is carried out not by illumination, but by heating (thermoluminescence).
The characteristics of dosimeters DPG-02, DPG-03, DPS-11 are given in Table 3.
Table 3.
where P and is the measured dose, P.
The time for taking readings from one detector is about 70 s, and from three detectors no more than 3 minutes.
Timely detection of radioactive contamination, determination of the degree of its impact on the safety and activities of enterprise personnel and the population is the most important task of the radiation reconnaissance and dosimetric monitoring system. The radiation reconnaissance and dosimetric monitoring system includes forces and means.
Forces refer to organizational structures that engage in intelligence and control. These include: observation and laboratory control network institutions (hydrometeorological stations, sanitary and epidemiological surveillance centers, veterinary laboratories, agrochemical laboratories, facility laboratories, institutes, etc.), radiation and chemical observation posts and other intelligence formations, laboratories, industrial enterprises, administrative structures of civil defense, etc.
The means of radiation reconnaissance and dose control include dosimetric instruments with which certain structures are equipped. It is dosimetric instruments that mainly determine the effectiveness of radiation reconnaissance and control.
Dosimetric instruments for measuring ionizing radiation (IR):
Radiometers– are used to measure the flux density and dose rate of radiation, as well as the activity of radionuclides.
Spectrometers– are intended to study the distribution of radiation by energy, charge, mass of AI particles, that is, for detailed analysis samples of any materials, sources of AI.
Dosimeters– used to measure individual equivalent dose and dose rate of X-ray, beta and gamma radiation in the energy range from 50 keV to 2-3 MeV. Common models: DKG and DKS (individual), MKS (dosimeter-radiometer) - differ in accuracy class and options (domestic or professional), number and type of detectors, design (portable or stationary), etc.
The following are usually used as a radiation detector:
- chamber-ionization gas-discharge Geiger-Muller counters type SBM-20 (standard, beta filter - two-layer, made of copper and lead, shields the sensor on all sides);
- SBM-21 (insensitive to low-energy gamma radiation and almost does not react to betta);
- end counters Beta-1/5 (window made of mica) - the most accurate, and more expensive, compared to the two above.
A wide range of measurements, the highest possible accuracy and operational reliability are found only in full-featured devices of normal size and professional class, but their price is significantly higher than that of household models.
Professional equipment options:
- mode of operational monitoring of specific activity of 137Cs in liquid and bulk samples in field conditions;
- the ability to measure the flux density of alpha and beta particles from contaminated surfaces, the ambient dose equivalent rate and the dose of X-ray and gamma radiation;
- non-volatile memory and reading of recorded data on a display or personal computer;
- the possibility of further retrofitting the device with additional detection units, as necessary
Rules for operating dosimetric devices
Do not drop and protect from dust, moisture and aggressive gases getting into the housing, otherwise the settings will be lost and the device will fail (this also applies to external detection units). Industrial, professional-grade radiometers and dosimeters can operate at high humidity (up to 90-100%, at +25 degrees), but inexpensive household appliances can only operate at up to 70-80% and they must somehow be protected from water and water vapor condensation (place in soft polyethylene, hermetically sealed under a film, through which you could turn on the toggle switches and press the buttons). Do not disassemble, do not break the seal, ... only in this case there will be accuracy. The time to establish the operating mode (“warming up the device”) is approximately 10 seconds.Measurement accuracy of dosimetric instruments
Radiometric instruments are characterized by a significant scatter of readings (up to plus/minus 20-40%). These devices also take a long time to measure. To improve the convergence of results, at least up to +/- 10-15%, increase the number and time of measurements (including the use of duplicate devices). Manufacturers reduce instrument error by increasing sensitivity - increasing the number and quality of ionizing radiation detectors (gas-discharge counters or various types of scintillators made of crystals, special plastic or ceramics) in radiometric devices, which significantly affects the cost of the set.Additional errors of dosimetric instruments
Additional errors (dispersion of readings) of the device are caused by the following reasons:- temperature other than room temperature changes parameters electrical diagram- up to +/- 15%
- high humidity and condensation - up to +/- 10%
- battery discharge - up to +/- 10%
- variations (short-period) of cosmic radiation and X-rays - hundredths to tenths of a microsievert per hour
// they all act integrally (in total)
Periodic verification and calibration is carried out once a year - this is the standard verification interval for equipment. Household radiometers, dosimeters - can be checked against new, recently purchased or just verified devices by carrying out parallel measurements in the increased accuracy, "on a level field."
Measurement results obtained using a household appliance (even with acceptable, fairly high accuracy) cannot be used for official conclusions by government agencies. To do this, you need professional, certified equipment that has passed state verification and, in fact, a qualified specialist, an operator who will correctly take measurements, perform calculations and document the research results.
Calculation example
In a certain place, a radioactive background from gamma radiation was recorded equal to 50 μR/hour (50 μrad/hour; 0.5 μGy/hour; 0.5 μSv/hour)
Staying there for 1 hour, a person will receive an equivalent dose (ED) of 50 μrem (corresponding to 0.5 microsievert).
For a year this will be: ED = 50 μR/hour * 8760 hour = 438000 μRem = 438 mRem = 4.48 mSv/year - almost at the limit of the permissible absorbed dose (should be “no more than 5 millisieverts in a single year from any five-year time interval”) .