CN117930314A - Uniformity verification method for personal dose equivalent rate of beta reference radiation field eye crystal - Google Patents
Uniformity verification method for personal dose equivalent rate of beta reference radiation field eye crystal Download PDFInfo
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Abstract
The invention relates to personal dose equivalent rate in beta reference radiation fieldThe uniformity verification method of (2) comprises the following steps: measuring absorption dose rate in beta radiation fieldAnd its uniformity distribution; measuring the energy spectrum of the Sr/Y-90 beta radiation field; when the distribution of the energy spectrum area of the Sr/Y-90 beta radiation field is changed, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate is established to obtain the personal dose equivalent rate in the beta radiation fieldIs a regional distribution measurement; determination of personal dose equivalent rate of Sr/Y-90 beta radiation fieldUniformity region. The method provided by the invention can measure the personal dose equivalent rate of expressing the beta radiation level of human eye crystals in the beta radiation field of a BSS 2 standard deviceWhen the uniformity area is formed, the problems that the directional dose equivalent rate uniform area in the beta radiation field is changed and the personal dose equivalent rate in the beta radiation field is caused due to the factors such as deformation and aging of the flattening filter after long-term use are solvedThe difficulty of a certain difference from the PC end indication value exists.
Description
Technical Field
The invention belongs to the technical field of metering test, and particularly relates to personal dose equivalent rate in a beta reference radiation fieldIs a uniformity verification method of (1).
Background
The radiation absorption dose is a physical quantity used to represent the amount of energy absorbed by an irradiated substance per unit mass when ionizing radiation interacts with the substance. The average energy granted by a substance deposited in an infinitely small volume element by ionizing radiation is the radiation absorption dose, which is the quotient of the energy granted by the mass of the substance in that volume element.
The beta absorbed dose is an integral part of the field of ionizing radiation metering. The Beta absorption dose reference radiation in China is mostly provided by Beta Secondary STANDARD TYPE (BSS 2) standard devices, the Beta absorption dose reference radiation is based on Beta radioactive isotopes 90Sr-90Y、85Kr、147 Pm, and the emitted Beta rays can provide a radiation field with uniform dose rate within the range of tens of centimeters in diameter at a measuring point after flattening the whole beam of the filter.
In workplace or environmental monitoring, the measurement of dose equivalent values is performed in the "no receptor" situation, i.e. the location of interest is one where a person may reside, but in fact no person or model is present at that location, and other objects remote from the receptor and the absorption, scattering, etc. of these objects occur. Personal dose equivalent rate of beta radiationRefers to the dose equivalent per unit time in Sv/h at a given depth of 3mm in human tissue. Generally,/>Is used to express the beta radiation level of the human eye lens.
Disclosure of Invention
In view of the deficiencies of the prior art, it is an object of the present invention to provide a personal dose equivalent rate in a beta reference radiation fieldThe uniformity verification method is used for solving the problem that the personal dose equivalent rate uniform area in the beta radiation field changes due to deformation and aging factors and the like of the flattening filter after long-term use, so that the personal dose equivalent rate/>, in the beta radiation field is causedThe difficulty of a certain difference from the PC end indication value exists.
In order to achieve the above purpose, the invention adopts the following technical scheme: personal dose equivalent rate in beta reference radiation fieldThe uniformity verification method of (2), the method comprising the steps of:
s1, measuring absorption dose rate in beta radiation field And its uniformity distribution;
s2, measuring the energy spectrum of the Sr/Y-90 beta radiation field;
s3, when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field is changed, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate is established, and the personal dose equivalent rate in the beta radiation field is obtained Is a regional distribution measurement;
s4, determining personal dose equivalent rate of Sr/Y-90 beta radiation field Uniformity region.
Further, the step S1 includes the following specific steps:
S11, placing the sensitive volume center of the ionization chamber at a measuring point of the normal center of the Sr/Y-90 beta radiation field, and ensuring that beta rays vertically enter the ionization chamber;
S12, calculating the absorption dose rate at the measuring point according to the accumulated charge J a reading fed back by an electrometer connected with the ionization chamber and the formulas (1) - (3)
Wherein:
j a: accumulating an amount of charge, C;
Average ionization energy of air, eV;
The ratio of the average mass blocking power of the ionization chamber entrance window and the air is constant without units;
air mass of sensitive volume, m 3/kg;
k PT: a temperature air pressure correction factor, wherein P is the ambient air pressure, kPa; t is ambient temperature, DEG C
T: measuring time, second;
D: absorbed dose, J/kg;
Absorption dose rate, J/(kg·h);
S13, taking a measuring point as a center, moving the sensitive volume center of the ionization chamber by 20.0cm along the upper, lower, left and right directions on a vertical plane where the sensitive volume center of the ionization chamber is positioned, setting the moving step length to be 1.0 cm-2.0 cm, obtaining the accumulated charge quantity J a at each moving point position, and calculating the absorption dose rate at each moving point position Thereby obtaining the absorption dose rate/>, in the beta radiation fieldIs a uniform distribution of (a).
Further, the energy spectrum of the Sr/Y-90 beta radiation field is measured by adopting a SiPIN detector; the SiPIN detector is connected with a matched preamplifier, a main amplifier and a digital multichannel.
Further, when the SiPIN detector is adopted to carry out the energy spectrum measurement of Sr/Y-90 beta radiation field, the front window of the SiPIN detector is covered with an aluminized polyester film of 3mg cm 2.
Further, the sensitive volume center of the SiPIN detector is placed at a position coincident with the sensitive volume center of the ionization chamber; an H p (3) phantom is placed immediately behind the SiPIN detector.
Further, when the SiPIN detector is used for carrying out energy spectrum measurement of Sr/Y-90 beta radiation field, the absorption dose rate is equal to that in the step S1The uniformity distribution measurement method of the (2) is consistent, namely after each 1 group of accumulated charge readings are measured in the ionization chamber, the sensitive volume center of the SiPIN detector is placed at a position which coincides with the sensitive volume center of the ionization chamber, and the SiPIN detector is replaced to measure and record the energy spectrum area distribution of the Sr/Y-90 beta radiation field at the current position.
Further, the step S3 includes the following specific steps:
S31, simulating and establishing human tissues and an H p (3) phantom by using MCNP to obtain a calculation method of a conversion coefficient of the absorption dose rate-the personal dose equivalent rate;
S32, establishing a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field changes;
S33, combining the measurement points obtained in the step S1 and the absorption dose rate at each moving point Obtaining the personal dose equivalent rate/> in the Sr/Y-90 beta radiation fieldIs a measurement of the regional distribution of (a).
Further, step S32 includes the following specific steps:
s321, combining the energy spectrum region distribution result of the Sr/Y-90 beta radioactive nuclide matched with the BSS2 standard device measured by adopting the SiPIN detector, and calculating according to a formula (5) to obtain a conversion coefficient H p(3,T)/DT of the absorption dose rate-personal dose equivalent rate corresponding to the change of the energy spectrum region distribution of the beta radiation field of the Sr/Y-90 beta radioactive nuclide under the H p (3) phantom;
wherein H p (3, T) is a small volume element personal dose equivalent of 3mm depth inside the human tissue model when the Sr/Y-90 beta radionuclide is irradiated, and Sv;
Phi E is the fluence of energy E of Sr/Y-90 beta radionuclide, m -3;
Q is the beta particle quality factor, taking q=1 Sv/Gy;
Energy deposition for unit mass in small volume element, J/kg;
d T,E is the deposition energy of Sr/Y-90 beta radionuclide with fluence phi E and energy E in the small volume element, J/kg;
d T is the deposition energy of Sr/Y-90 beta radionuclide in the small volume element, J/kg;
S322, establishing a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field changes.
Further, the step S33 includes the following specific steps:
the measuring points obtained in the step S1 and the absorption dose rate at each moving point are measured The measurement result is multiplied by the conversion coefficient H p(3,T)/DT of the corresponding absorption dose rate-personal dose equivalent rate in the conversion coefficient database of the absorption dose rate-personal dose equivalent rate, and the personal dose equivalent rate/>, at the measurement point and each moving point, is calculatedThereby obtaining the personal dose equivalent rate/>, in the beta radiation fieldIs a region distribution of (a).
Further, in step S4, a region having a deviation of not more than + -5% from the personal dose equivalent rate of the measurement point is selected, which is identified as the personal dose equivalent rate of the beta radiation fieldUniformity region.
The beneficial effects of the invention are as follows: personal dose equivalent rate in beta reference radiation field provided by the inventionCan be verified by measuring the absorption dose rate/>, in the beta radiation fieldAnd its uniformity distribution; measuring the energy spectrum of the Sr/Y-90 beta radiation field; when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field is changed, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate is established to obtain the personal dose equivalent rate/>, in the beta radiation fieldIs a regional distribution measurement; determination of personal dose equivalent Rate/>, of Sr/Y-90 beta radiation fieldUniformity region. The method provided by the invention can measure the personal dose equivalent rate of expressing the beta radiation level of human eye crystals in the beta radiation field of a BSS2 standard deviceWhen the uniformity area is formed, the problem that the directional dose equivalent rate uniformity area in the beta radiation field changes due to deformation and aging factors of the flattening filter after long-term use and the like, so that the personal dose equivalent rate/>, in the beta radiation field, is caused is solvedThe difficulty of a certain difference from the PC end indication value exists.
Drawings
FIG. 1 is a graph of personal dose equivalent rate in a beta reference radiation field provided in an embodiment of the inventionA flow diagram of the uniformity verification method of (2);
FIG. 2 is a graph showing absorbed dose rate in a beta radiation field according to an embodiment of the present invention A measurement schematic;
FIG. 3 is a schematic diagram of an energy spectrum measurement of a beta radiation field provided by an embodiment of the present invention;
Fig. 4 is a schematic diagram of a human tissue and H p (3) phantom created using MCNP according to an embodiment of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other examples obtained by those skilled in the art without making any inventive effort based on the examples in the present invention are within the scope of protection of the present invention.
It should be noted that, in the description of the embodiments of the present invention, terms such as "upper", "lower", "front", "rear", "front", "back", "left", "right", "horizontal", "vertical", "inner", "outer", and the like indicate orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The inventor finds that the flattening filter is easy to deform and age after long-term use, so that the uniformity of the beta radiation dose rate at the reference point is changed, but the reference value at the PC end only corrects the decay of the radioactive source and the environmental factors of the measuring point, and the actual value of the measuring point is different from the reference value at the PC end. The change is mainly reflected in the aspects of absorption dose rate and dose equivalent rate 2, the uniformity change of the absorption dose rate can be directly measured by the thin-window ionization chamber, but the measurement of the dose equivalent rate depends on the energy of beta rays, and the uniformity change cannot be directly measured.
Personal dose equivalent rate due to beta radiationIs used for representing the dose equivalent level generated by the unit time of the actual radiation field at the depth of 3mm in a human body (or a sphere model), and in the beta standard radiation field of a BSS2 standard device, only the energy of Sr/Y-90 is used for controlling the personal dose equivalent rate/>Contributing, other nuclides are not enough in energy and do not contribute. In addition, an H p (3) phantom (PMMA cylinder of 20cm x 20 cm) was placed immediately behind the SiPIN detector to simulate total reflection of the human head in the Sr/Y-90 beta radiation field.
As shown in fig. 1-3, the present embodiment provides a personal dose equivalent rate in a beta reference radiation fieldUniformity verification method of (2), namely, in Sr/Y-90 beta radiation field, the dose equivalent rate/>, for individualsThe uniformity verification method of (2), the method comprising the steps of:
s1, measuring absorption dose rate in beta radiation field And its uniformity distribution;
As shown in the experiment of fig. 2, the sensitive volume center of the ionization chamber is placed at the measuring point of the normal center of the Sr/Y-90 beta radiation field, so that the normal incidence of beta rays to the ionization chamber is ensured; then, based on the accumulated charge J a reading fed back by the electrometer connected to the ionization chamber, the absorption dose rate at the measurement point can be calculated by referring to the formulas (1) to (3)
Wherein:
j a: accumulating an amount of charge, C;
Average ionization energy of air, eV;
The ratio of the average mass blocking power of the ionization chamber entrance window and the air is constant without units;
air mass of sensitive volume, m 3/kg;
k PT: a temperature air pressure correction factor, wherein P is the ambient air pressure, kPa; t is ambient temperature, DEG C
T: measuring time, second;
D: absorbed dose, J/kg;
Absorption dose rate, J/(kg·h);
Wherein, the ionization chamber is a thin window ionization chamber, and a PTW34045 type thin window ionization chamber can be selected.
Specifically, the method for obtaining the accumulated charge amount J a fed back by an electrometer connected with the ionization chamber comprises the following steps: the electrometer reading (i.e., current I) at the measurement point is recorded, combined with the residence time of the sensitive volume center of the ionization chamber at the measurement point, to obtain the accumulated charge amount J a at the measurement point.
Similarly, the measuring point is taken as the center, the sensitive volume center of the ionization chamber is respectively moved by 20.0cm along the upper direction, the lower direction, the left direction and the right direction on a vertical plane where the sensitive volume center of the ionization chamber is located, the moving step length can be set to be 1.0 cm-2.0 cm, the reading of the electrometer at each moving point position is recorded, and the accumulated charge quantity J a at each moving point position is obtained by combining the residence time at each moving point position. Then, the absorption dose rate at each moving point is calculated according to the formulas (1) - (3)Thereby, the absorption dose rate/>, in the beta radiation field can be obtainedIs a uniform distribution of the particles.
S2, measuring the energy spectrum of the Sr/Y-90 beta radiation field;
According to absorbed dose rate For further acquisition of individual dose equivalent rate/>It is also desirable to measure the energy spectrum giving the Sr/Y-90 beta radiation field (i.e. the spectral region distribution of the Sr/Y-90 beta radiation field, or the beta radiation field spectral region distribution of the Sr/Y-90 beta radionuclide).
The energy spectrum of the Sr/Y-90 beta radiation field is measured by using a SiPIN detector. In a specific embodiment, the SiPIN detector may be selected from the model BA-016-025-1500.
Specifically, when SiPIN detector is used for measuring the energy spectrum of Sr/Y-90 beta radiation field, siPIN detector is connected with matched 142A preamplifier, 575A main amplifier and MCA digital multichannel, and PC end connected with MCA digital multichannel can directly obtain the energy spectrum of Sr/Y-90 beta radiation field by matched software.
Specifically, as shown in fig. 3, when using SiPIN detector to measure the energy spectrum of Sr/Y-90 beta radiation field, covering 3mg cm 2 aluminized polyester film on the front window of SiPIN detector to avoid light; the center of the sensitive volume of SiPIN detector is placed at a position coincident with the center of the sensitive volume of the ionization chamber (i.e. the center of the sensitive volume of SiPIN detector is placed at the measurement point of the normal center of the Sr/Y-90 beta radiation field, ensuring that the beta rays are perpendicularly incident on the SiPIN detector), and the H p (3) phantom (Φ20cm×20cm PMMA cylinder) is placed immediately behind the SiPIN detector. When the SiPIN detector is used for carrying out the energy spectrum measurement of the Sr/Y-90 beta radiation field, the absorption dose rate is equal to that in the step S1After each measurement of 1 group of accumulated charge readings in the ionization chamber, the sensitive volume center of the SiPIN detector is placed at a position coincident with the sensitive volume center of the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum area distribution of the Sr/Y-90 beta radiation field at the current position (i.e. the sensitive volume center of the SiPIN detector is moved by 20.0cm along the up, down, left and right directions on the vertical plane where the sensitive volume center of the SiPIN detector is located with the measurement point as the center), each movement point is coincident with the sensitive volume center of the ionization chamber, and the energy spectrum area distribution of the Sr/Y-90 beta radiation field at each movement point is recorded). Moreover, the H p (3) body model moves along with the SiPIN detector at the same time, and the relative position between the H p (3) body model and the SiPIN detector is kept unchanged.
In a specific embodiment, siPIN detectors are used to measure the spectral region distribution of the Sr/Y-90 beta radionuclide associated with the BSS2 standard device.
S3, when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field is changed, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate is established, and the personal dose equivalent rate in the beta radiation field is obtainedIs a regional distribution measurement;
Based on the above steps S1, S2, the absorbed dose rate can be obtained And the overall distribution of the energy spectrum in the Sr/Y-90 beta radiation field, the conversion of the absorbed dose rate to the personal dose equivalent rate also requires an appropriate conversion factor. Although the conversion coefficient of Sr/Y-90 beta nuclides at a specified distance with or without a flattening filter is given in the ISO 6980-3 standard, the conversion coefficient in the ISO 6980-3 standard is no longer applicable when the beta spectrum changes due to aging of the flattening filter. Therefore, in order to obtain the distribution of the personal dose equivalent rate in the Sr/Y-90 β radiation field, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate needs to be established when the distribution of the energy spectrum region of the Sr/Y-90 β radiation field changes.
Specifically, step S3 includes the following specific steps:
S31, simulating and establishing human tissues and an H p (3) phantom by using MCNP to obtain a calculation method of a conversion coefficient of the absorption dose rate-the personal dose equivalent rate;
As shown in fig. 4, the MCNP is utilized to establish human tissue and an H p (3) phantom, the human tissue is closely attached to the phantom, and the central normal directions of the human tissue and the H p (3) phantom are consistent; the single-energy beta particles with the given fluence phi and energy E are respectively incident into the human tissue model and the phantom from an incidence angle of 0 degrees. According to the definition of the personal dose equivalent, taking a small volume element at the depth of 3mm in the human tissue model along the horizontal direction of the radiation field, simulating and obtaining energy deposition dε and mass dm in the small volume element, combining the quality factor Q of beta particles (for externally irradiated weak penetrating beta particles, Q=1 Sv/Gy is usually taken), and calculating to obtain the personal dose equivalent H p0 (3, T) according to a formula (4).
Wherein H p0 (3, T) is a small volume element personal dose equivalent, sv, at the depth of 3mm in the human tissue model under the condition of single-energy beta particles with given fluence phi and energy E;
Q is the beta particle quality factor, taking q=1 Sv/Gy;
Energy deposition for unit mass in small volume element, J/kg;
Then, other structures in the tissue sphere model are removed, only a small volume element at the position of 3mm is reserved, and the deposition energy of the monoenergetic beta particles with the fluence phi and the energy E in the small volume element, namely the absorbed dose D T0 is obtained. Therefore, the conversion coefficient H p0(3,T)/DT0 of the absorption dose-personal dose equivalent of the small volume element at the depth of 3mm in the human tissue model under the condition of the single-energy beta particle with the given fluence phi and energy E is obtained, and the conversion coefficient is the conversion coefficient of the absorption dose rate-personal dose equivalent rate.
S32, establishing a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field changes;
Combining the energy spectrum region distribution result of the Sr/Y-90 beta radionuclide, which is obtained by adopting a SiPIN detector to measure in the step S2 and is matched with a BSS2 standard device, calculating according to a formula (5) to obtain a conversion coefficient H p(3,T)/DT of the absorption dose rate-personal dose equivalent rate corresponding to the change of the energy spectrum region distribution of the beta radiation field of the Sr/Y-90 beta radionuclide under the H p (3) phantom; the conversion coefficient H p(3,T)/DT of the absorption dose rate of small volume element at the depth of 3mm in the human tissue model and the personal dose equivalent rate can be obtained when the distribution of the beta radiation field energy spectrum area of the Sr/Y-90 beta radionuclide (the distribution of the beta radiation field energy spectrum area is changed due to the factors such as deformation and aging of a flattening filter) is changed.
Wherein H p (3, T) is a small volume element personal dose equivalent of 3mm depth inside the human tissue model when the Sr/Y-90 beta radionuclide is irradiated, and Sv;
Phi E is the fluence of energy E of Sr/Y-90 beta radionuclide, m -3;
Q is the beta particle quality factor, taking q=1 Sv/Gy;
Energy deposition for unit mass in small volume element, J/kg;
d T,E is the deposition energy of Sr/Y-90 beta radionuclide with fluence phi E and energy E in the small volume element, J/kg;
d T is the deposition energy, J/kg, of Sr/Y-90 beta radionuclide in a small volume element.
Furthermore, according to the conversion coefficient H p(3,T)/DT of the absorption dose rate-personal dose equivalent rate of the small volume element at the depth of 3mm inside the human tissue model when the distribution of the beta radiation field energy spectrum region of the Sr/Y-90 beta radionuclide is changed, a corresponding conversion coefficient database of the absorption dose rate-personal dose equivalent rate when the distribution of the Sr/Y-90 beta radiation field energy spectrum region is changed can be established.
S33, combining the measurement points obtained in the step S1 and the absorption dose rate at each moving pointObtaining the personal dose equivalent rate/> in the Sr/Y-90 beta radiation fieldIs a regional distribution measurement;
According to formula (6), the measurement points obtained in step S1 and the absorbed dose rate at each of the moving points are calculated The measurement result is multiplied by the conversion coefficient H p(3,T)/DT of the corresponding absorption dose rate-personal dose equivalent rate in the conversion coefficient database of the absorption dose rate-personal dose equivalent rate, so that the personal dose equivalent rate/>, at the measurement point and each moving point, can be directly calculatedAnd measuring the result.
Thus, the personal dose equivalent rate in the beta radiation field can be finally obtainedIs a measurement of the regional distribution of (a).
S4, determining personal dose equivalent rate of Sr/Y-90 beta radiation fieldA uniformity region;
The personal dose equivalent rate of the beta radiation field can be identified by selecting the area with the personal dose equivalent rate deviation of less than +/-5% from the measuring point (center position) Uniformity region.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. Personal dose equivalent rate in beta reference radiation fieldIs characterized in that the method comprises the following steps:
s1, measuring absorption dose rate in beta radiation field And its uniformity distribution;
s2, measuring the energy spectrum of the Sr/Y-90 beta radiation field;
s3, when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field is changed, a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate is established, and the personal dose equivalent rate in the beta radiation field is obtained Is a regional distribution measurement;
s4, determining personal dose equivalent rate of Sr/Y-90 beta radiation field Uniformity region.
2. Personal dose equivalent rate in beta reference radiation field according to claim 1The uniformity verification method of (1) is characterized in that the step S1 comprises the following specific steps:
S11, placing the sensitive volume center of the ionization chamber at a measuring point of the normal center of the Sr/Y-90 beta radiation field, and ensuring that beta rays vertically enter the ionization chamber;
S12, calculating the absorption dose rate at the measuring point according to the accumulated charge J a reading fed back by an electrometer connected with the ionization chamber and the formulas (1) - (3)
Wherein:
j a: accumulating an amount of charge, C;
Average ionization energy of air, eV;
The ratio of the average mass blocking power of the ionization chamber entrance window and the air is constant without units;
air mass of sensitive volume, m 3/kg;
k PT: a temperature air pressure correction factor, wherein P is the ambient air pressure, kPa; t is the ambient temperature, and the temperature is DEG C T: measuring time, second;
D: absorbed dose, J/kg;
Absorption dose rate, J/(kg·h);
S13, taking a measuring point as a center, moving the sensitive volume center of the ionization chamber by 20.0cm along the upper, lower, left and right directions on a vertical plane where the sensitive volume center of the ionization chamber is positioned, setting the moving step length to be 1.0 cm-2.0 cm, obtaining the accumulated charge quantity J a at each moving point position, and calculating the absorption dose rate at each moving point position Thereby obtaining the absorption dose rate/>, in the beta radiation fieldIs a uniform distribution of (a).
3. Personal dose equivalent rate in beta reference radiation field according to claim 2The uniformity verification method of (1) is characterized in that the energy spectrum of the Sr/Y-90 beta radiation field is measured by adopting a SiPIN detector; the SiPIN detector is connected with a matched preamplifier, a main amplifier and a digital multichannel.
4. A personal dose equivalent rate in a beta reference radiation field according to claim 3The uniformity verification method is characterized in that when the SiPIN detector is adopted to conduct energy spectrum measurement of Sr/Y-90 beta radiation field, an aluminized polyester film of 3mg cm 2 is covered on the front window of the SiPIN detector.
5. A personal dose equivalent rate in a beta reference radiation field according to claim 3The uniformity verification method is characterized in that the sensitive volume center of the SiPIN detector is placed at a position coincident with the sensitive volume center of the ionization chamber; an H p (3) phantom is placed immediately behind the SiPIN detector.
6. The beta reference intra-radiation personal dose equivalence rate of claim 5The uniformity verification method is characterized in that when the SiPIN detector is adopted to conduct energy spectrum measurement of Sr/Y-90 beta radiation field, the method is similar to the absorption dose rate/>, in the step S1The uniformity distribution measurement method of the (2) is consistent, namely after each 1 group of accumulated charge readings are measured in the ionization chamber, the sensitive volume center of the SiPIN detector is placed at a position which coincides with the sensitive volume center of the ionization chamber, and the SiPIN detector is replaced to measure and record the energy spectrum area distribution of the Sr/Y-90 beta radiation field at the current position.
7. The beta reference intra-radiation personal dose equivalence rate of claim 6Is characterized in that the step S3 comprises the following specific steps:
S31, simulating and establishing human tissues and an H p (3) phantom by using MCNP to obtain a calculation method of a conversion coefficient of the absorption dose rate-the personal dose equivalent rate;
S32, establishing a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field changes;
S33, combining the measurement points obtained in the step S1 and the absorption dose rate at each moving point Obtaining the personal dose equivalent rate/> in the Sr/Y-90 beta radiation fieldIs a measurement of the regional distribution of (a).
8. The beta reference intra-radiation personal dose equivalence rate of claim 7Is characterized in that step S32 includes the following specific steps:
s321, combining the energy spectrum region distribution result of the Sr/Y-90 beta radioactive nuclide matched with the BSS2 standard device measured by adopting the SiPIN detector, and calculating according to a formula (5) to obtain a conversion coefficient H p(3,T)/DT of the absorption dose rate-personal dose equivalent rate corresponding to the change of the energy spectrum region distribution of the beta radiation field of the Sr/Y-90 beta radioactive nuclide under the H p (3) phantom;
wherein H p (3, T) is a small volume element personal dose equivalent of 3mm depth inside the human tissue model when the Sr/Y-90 beta radionuclide is irradiated, and Sv;
Omega E is the fluence of energy E of Sr/Y-90 beta radionuclide, m -3;
Q is the beta particle quality factor, taking q=1 Sv/Gy;
Energy deposition for unit mass in small volume element, J/kg;
D T,E is the deposition energy of Sr/Y-90 beta radionuclide with fluence omega E and energy E in the small volume element, J/kg;
d T is the deposition energy of Sr/Y-90 beta radionuclide in the small volume element, J/kg;
S322, establishing a conversion coefficient database of the corresponding absorption dose rate-personal dose equivalent rate when the distribution of the energy spectrum region of the Sr/Y-90 beta radiation field changes.
9. The beta reference intra-radiation personal dose equivalence rate of claim 8Is characterized in that the step S33 includes the following specific steps:
the measuring points obtained in the step S1 and the absorption dose rate at each moving point are measured The measurement result is multiplied by the conversion coefficient H p(3,T)/DT of the corresponding absorption dose rate-personal dose equivalent rate in the conversion coefficient database of the absorption dose rate-personal dose equivalent rate, and the personal dose equivalent rate/>, at the measurement point and each moving point, is calculatedThereby obtaining the personal dose equivalent rate/>, in the beta radiation fieldIs a region distribution of (a).
10. Personal dose equivalent rate in beta reference radiation field according to claim 1In step S4, a region having a deviation of not more than + -5% from the personal dose equivalent rate of the measurement point is selected, and the region is identified as personal dose equivalent rate/>, of the beta radiation fieldUniformity region.
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