A method for measuring uniform regions of directional dose equivalent rate in a beta reference radiation field

Abstract

The present application relates to a kind of β reference radiation field in the uniform area measurement method of directional dose equivalent rate, comprising the following steps: measuring absorption dose rate obtains the uniformity distribution of absorption dose rate in β radiation field;The energy spectrum of β radiation field is measured, and the energy spectrum area distribution of β radiation field is obtained;When the energy spectrum area distribution of β radiation field of β radioactive nuclide changes, the conversion coefficient database of corresponding absorption dose rate-directional dose equivalent rate is established, and the area distribution measurement result of directional dose equivalent rate in β radiation field is obtained;Identify the directional dose equivalent rate uniformity area of β radiation field.The method provided by the present application can solve the problem that there is a certain difference between the directional dose equivalent rate at the measuring point and the PC end indication value when measuring the uniform area of directional dose equivalent rate H' (0.07) in the β radiation field of BSS 2 standard device due to the deformation and aging of flattening filter after long-term use and other factors, causing the change of directional dose equivalent rate uniform area in β radiation field.

Description

Technical Field

[0001] This invention belongs to the field of metrology and testing technology, and specifically relates to a method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field. Background Technology

[0002] Beta absorbed dose is an indispensable part of ionizing radiation metrology. In my country, beta absorbed dose reference radiation is mostly provided by the Beta Secondary Standard Type 2 (BSS2) standard device, which is based on beta radioisotopes. 90 Sr- 90 Y、 85 Kr、 147 The emitted beta rays, after being bundled by the flattened filter, can provide a radiation field with a uniform dose rate within a range of tens of centimeters in diameter at the measurement point, and provide a corresponding reference value at the PC end.

[0003] Directional dose equivalent rate of beta radiation This refers to the dose equivalent produced per unit time at a point in the radiation field, within a radius of Ω and a depth of 0.07 mm in a specified direction within the IRCU sphere, at the corresponding extended field. The unit is Sv / h. Typically, It is the recommended monitoring amount for environmental beta nuclear radiation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for measuring the uniform region of directional dose equivalent rate in a β reference radiation field. This method solves the problem that factors such as deformation and aging of flattened filters after long-term use cause changes in the uniform region of the directional dose equivalent rate in the β radiation field, leading to variations in the directional dose equivalent rate at the measurement point. The problem is that there is a certain difference between the values ​​displayed on the PC and the values ​​displayed on the PC.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field, the method comprising the following steps:

[0006] S1. Measuring absorbed dose rate Obtain the absorbed dose rate in the β radiation field The uniformity of the distribution;

[0007] S2. Measure the energy spectrum of the β radiation field to obtain the energy spectrum region distribution of the β radiation field;

[0008] S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate to obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results;

[0009] S4. Determine the directional dose equivalent rate of the β radiation field. Uniform region.

[0010] Furthermore, step S1 includes the following specific steps:

[0011] S11. Place the sensitive volume center of the ionization chamber at the measurement point at the center of the normal of the β radiation field to ensure that the β rays are incident perpendicularly into the ionization chamber.

[0012] S12. Based on the accumulated charge J fed back by the electrometer connected to the ionization chamber. a Read the data and calculate the absorbed dose rate at the measurement point.

[0013] S13. Taking the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. The step size can be set to 1.0 cm to 2.0 cm to obtain the cumulative charge J at each moving point. a The absorbed dose rate at each moving point was calculated. Thus, the absorbed dose rate in the β radiation field is obtained. The uniformity of the distribution.

[0014] Furthermore, the ionization chamber is a thin-window ionization chamber.

[0015] Furthermore, the energy spectrum of the β radiation field is measured using a SiPIN detector, which is connected to a matching preamplifier, main amplifier, and digital multichannel. The PC connected to the digital multichannel acquires the energy spectrum of the β radiation field through matching software.

[0016] Furthermore, when performing energy spectrum measurements of the β radiation field using the SiPIN detector, a 3 mg·cm² area is placed in front of the SiPIN detector window. 2 Aluminized polyester film.

[0017] Furthermore, when using the SiPIN detector to perform energy spectrum measurements of the β radiation field, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the β radiation field at the current position.

[0018] Furthermore, the energy spectrum distribution of the β-radioactive nuclide associated with the BSS2 standard device was measured using the SiPIN detector.

[0019] Furthermore, step S3 includes the following specific steps:

[0020] S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained.

[0021] S32. Establish a database of conversion coefficients for the conversion coefficients between absorbed dose rate and directional dose equivalent rate when the distribution of the β radiation field energy spectrum region of β radionuclides changes.

[0022] S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Obtain the directional dose equivalent rate in the β radiation field The regional distribution measurement results.

[0023] Furthermore, step S31 includes the following specific steps:

[0024] S311. Establish a unit mass ICRU tissue sphere model using MCNP;

[0025] S312. Given a monoenergetic β particle with a flux Φ and energy E, an incident particle is incident on a tissue sphere model from a specified orientation d at an incident angle θ.

[0026] S313. Take a small volume element at a surface depth of 0.07 mm along the orientation d direction of the tissue sphere model, simulate and obtain the energy deposition dε and mass dm in the small volume element, and calculate the directional dose equivalent H0′(0.07,T) according to formula (4) in combination with the β particle quality factor Q.

[0027]

[0028] Where H0′(0.07,T) is the small volume element directional dose equivalent at a surface depth of 0.07 mm in the ICRU tissue sphere model under the condition of monoenergetic β particles with given fluence Φ and energy E, and Sv;

[0029] Q is the β-particle quality factor, taken as Q = 1Sv / Gy;

[0030] Energy deposition per unit mass within a small volume element, expressed in J / kg;

[0031] S314. Remove other structures from the tissue sphere model, retaining only the small volume element at 0.07 mm, and obtain the deposition energy of monoenergetic β particles with fluence Φ and energy E within the small volume element, i.e., the absorbed dose D. T0 ;

[0032] S315. Obtain the conversion coefficient H0′(0.07,T) / D of absorbed dose - directional dose equivalent for a small volume element at a surface depth of 0.07 mm of the ICRU tissue - equivalent sphere model under the condition of mono - energetic β particles with a given fluence Φ and energy E T0 , which is the conversion coefficient of absorbed dose rate - directional dose equivalent rate.

[0033] Furthermore, step S32 includes the following specific steps:

[0034] S321. Combine the use of the SiPIN detector to measure the energy - spectrum regional distribution of the β - radioactive nuclide supporting the BSS2 standard device, and calculate the conversion coefficient H′(0.07,T) / D of absorbed dose rate - directional dose equivalent rate corresponding to the change in the energy - spectrum regional distribution of the β - radiation field of the β - radioactive nuclide according to formula (5) T ;

[0035]

[0036] Among them, H′(0.07,T) is the directional dose equivalent of a small volume element at a surface depth of 0.07 mm of the ICRU tissue - equivalent sphere model under the condition of the β - radioactive nuclide supporting the BSS2 standard device, Sv;

[0037] Φ E is the fluence of the energy E of the β - radioactive nuclide supporting the BSS2 standard device, Sv;

[0038] Q is the β - particle quality factor, taking Q = 1 Sv / Gy;

[0039] is the energy deposition per unit mass in the small volume element, J / kg;

[0040] D T,E is the deposited energy of the β - radioactive nuclide supporting the BSS2 standard device with fluence Φ E and energy E in the small volume element, J / kg;

[0041] D T is the deposited energy of the β - radioactive nuclide supporting the BSS2 standard device in the small volume element, J / kg;

[0042] S322. Establish a conversion - coefficient database of the conversion coefficient of absorbed dose rate - directional dose equivalent rate corresponding to the change in the energy - spectrum regional distribution of the β - radiation field of the β - radioactive nuclide. ​​​​​​The beneficial effects of this invention are as follows: Using the uniform region measurement method for directional dose equivalent rate in a β reference radiation field provided by this invention, the absorbed dose rate can be measured... Obtain the absorbed dose rate in the β radiation field The uniformity of the distribution of the beta radiation field was determined; the energy spectrum of the beta radiation field was measured to obtain the spectral distribution of the beta radiation field; a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate was established to determine the directional dose equivalent rate in the beta radiation field when the spectral distribution of the beta radionuclide changes. The regional distribution measurement results; determining the directional dose equivalent rate of the β radiation field. Uniformity region. The method provided by this invention can solve the problem of changes in the uniformity region of the directional dose equivalent rate H′(0.07) in the β radiation field of the BSS2 standard device caused by factors such as deformation and aging of the flattened filter after long-term use, which leads to changes in the directional dose equivalent rate at the measurement point. The problem is that there is a certain difference between the values ​​displayed on the PC and the values ​​displayed on the PC. Attached Figure Description

[0045] Figure 1 A flowchart illustrating a method for measuring the directional dose equivalent rate in a uniform region within a β reference radiation field, provided as an embodiment of the present invention.

[0046] Figure 2 A schematic diagram of absorbed dose rate uniformity measurement provided for an embodiment of the present invention;

[0047] Figure 3 A schematic diagram of a unit mass ICRU tissue sphere model established using MCNP, provided for an embodiment of the present invention. Detailed Implementation

[0048] The technical solutions in the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0049] It should be noted that in the description of the embodiments of the present invention, the terms "upper," "lower," "front," "rear," "front," "back," "left," "right," "horizontal," "vertical," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] The inventors discovered that flattened filters are prone to deformation and aging after long-term use, causing changes in the uniformity of the beta radiation dose rate at the reference point. However, the reference value at the PC only corrects for the decay of the radiation source itself and environmental factors at the measurement point, which also leads to a difference between the actual value at the measurement point and the reference value at the PC. This change is mainly reflected in two aspects: absorbed dose rate and dose equivalent rate. The uniformity change of absorbed dose rate can be directly measured using a thin-window ionization chamber, but the measurement of dose equivalent rate depends on the energy of beta rays and cannot directly measure the uniformity change.

[0051] like Figure 1-3 As shown, this embodiment provides a method for measuring the directional dose equivalent rate in a uniform region within a β reference radiation field. Specifically, it measures the directional dose equivalent rate within the β radiation field of the BSS2 standard device. A method for measuring a uniform region, the method comprising the following steps:

[0052] S1. Measure the absorbed dose rate to obtain the absorbed dose rate in the β radiation field. The uniformity of the distribution;

[0053] like Figure 2 In the experiment shown, the sensitive volume center of the ionization chamber is placed at the measurement point at the center of the normal to the β radiation field, ensuring that the β rays are incident perpendicularly into the ionization chamber; then, the accumulated charge J is fed back from the electrometer connected to the ionization chamber. a The absorbed dose rate at the measurement point can be calculated by referring to formulas (1) to (3).

[0054]

[0055]

[0056]

[0057] In the formula:

[0058] J a : Cumulative charge, C;

[0059] The average ionization energy of air, eV;

[0060] The ratio of the average mass blocking power of the entrance window of the ionization chamber to that of the air is a constant without dimensions.

[0061] Sensitive volume air mass, m 3 / kg;

[0062] k PT Temperature and pressure correction factor, where P is the ambient air pressure (kPa) and T is the ambient temperature (°C).

[0063] t: Measurement time, in seconds;

[0064] D: Absorbed dose, J / kg;

[0065] Absorbed dose rate, J / kg·h;

[0066] The ionization chamber is a thin-window ionization chamber, and the PTW34045 type thin-window ionization chamber can be selected.

[0067] Specifically, the accumulated charge J reported by the electrometer connected to the ionization chamber. a The reading is obtained by recording the electrometer reading (current I) at the measurement point, and combining this reading with the residence time of the sensitive volume center of the ionization chamber at the measurement point to obtain the cumulative charge J at the measurement point. a .

[0068] Similarly, taking the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. The step size can be set to 1.0 cm to 2.0 cm. Record the electrometer reading at each moving point, and combine it with the dwell time at each moving point to obtain the cumulative charge J at each moving point. a Then, the absorbed dose rate at each moving point is calculated according to formulas (1) to (3). Therefore, the absorbed dose rate in the β radiation field can be obtained. The uniformity of the distribution.

[0069] S2. Measure the energy spectrum of the β radiation field to obtain the energy spectrum region distribution of the β radiation field;

[0070] Based on absorbed dose rate To determine the uniformity of the distribution, in order to further obtain the directional dose equivalent rate... To obtain a uniform region, the energy spectrum of the β radiation field also needs to be measured.

[0071] The energy spectrum of the β radiation field is measured using a SiPIN detector. In one specific embodiment, the SiPIN detector can be a BA-016-025-1500 model.

[0072] Specifically, when using a SiPIN detector to measure the energy spectrum of the β radiation field, the SiPIN detector is connected to a matching 142A preamplifier, a 575A main amplifier, and an MCA digital multichannel amplifier. The PC connected to the MCA digital multichannel amplifier can directly acquire the energy spectrum of the β radiation field through the matching software.

[0073] Specifically, when using a SiPIN detector to measure the energy spectrum of the β radiation field, a 3 mg·cm² area is placed in front of the SiPIN detector window. 2 The aluminized polyester film is used to shield the light; when the energy spectrum of the β radiation field is measured using a SiPIN detector, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the β radiation field at the current position.

[0074] In one specific embodiment, the energy spectrum distribution of the β radionuclides (Sr / Y-90, Kr-85, Pm-147) associated with the BSS2 standard device was measured using a SiPIN detector.

[0075] S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate to obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results;

[0076] Based on steps S1 and S2 above, the overall distribution of absorbed dose rate and energy spectrum in the β radiation field can be obtained. However, the conversion from absorbed dose rate to directional dose equivalent rate requires appropriate conversion factors. Although ISO 6980-3 provides conversion factors for specific types of β nuclides at specified distances with and without flattening filters, these conversion factors become inapplicable when the β energy spectrum changes due to the aging of the flattening filter. Therefore, to obtain the distribution of directional dose equivalent rate in the β radiation field, a database of absorbed dose rate-directional dose equivalent rate conversion factors needs to be established.

[0077] Specifically, step S3 includes the following steps:

[0078] S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained.

[0079] like Figure 3 As shown, an ICRU tissue sphere model with a unit mass (1 kg) is established using MCNP, which is the equivalent sphere used to simulate human tissue. A monoenergetic β particle with a fluence Φ and energy E is incident on the tissue sphere model from a specified orientation d at an incident angle θ (θ corresponds to the angle between the line d connecting the detector center to the radiation source and the horizontal normal during the movement of the SiPIN detector when measuring the energy spectrum. If the orientation d is horizontal with the β ray, θ = 0). According to the definition of directional dose equivalent, a small volume element is taken at a surface depth of 0.07 mm along the direction of orientation d. The energy deposition dε and mass dm within the small volume element are simulated and obtained. Combined with the β particle quality factor Q (for weakly penetrating β particles irradiated externally, Q = 1Sv / Gy is usually taken), the directional dose equivalent H0′(0.07,T) is calculated according to formula (4).

[0080]

[0081] Where H0′(0.07,T) is the small volume element directional dose equivalent at a surface depth of 0.07 mm in the ICRU tissue sphere model under the condition of monoenergetic β particles with given fluence Φ and energy E, and Sv;

[0082] Q is the β-particle quality factor, taken as Q = 1Sv / Gy;

[0083] Energy deposition per unit mass within a small volume element, J / kg;

[0084] Subsequently, other structures in the tissue sphere model were removed, leaving only a small volume element at 0.07 mm. The deposition energy of monoenergetic β particles with fluence Φ and energy E within this small volume element was obtained, i.e., the absorbed dose D. T0 Therefore, under the condition of monoenergetic β particles with a given fluence Φ and energy E, the conversion coefficient H0′(0.07,T) / D for the absorbed dose-directed dose equivalent of a small volume element at a surface depth of 0.07 mm in the ICRU tissue sphere model is obtained. T0 This is the conversion coefficient between absorbed dose rate and directional dose equivalent rate.

[0085] S32. Establish a database of conversion coefficients for the conversion coefficients between absorbed dose rate and directional dose equivalent rate when the distribution of the β radiation field energy spectrum region of β radionuclides changes.

[0086] Combined with the energy spectrum region distribution results of the β radioactive nuclides (Sr / Y-90, Kr-85, Pm-147) supported by the BSS2 standard device measured by the SiPIN detector in step S2, the H′(0.07,T) / D corresponding to the change in the energy spectrum region distribution of the β radiation field of the three β radioactive nuclides is calculated respectively according to formula (5). T That is, when the energy spectrum region distribution of the β radiation field changes (the change in the energy spectrum region distribution of the β radiation field caused by factors such as flattening filter deformation and aging) for each β radioactive nuclide, the conversion coefficient H′(0.07,T) / D of the absorbed dose rate - directional dose equivalent rate of the small volume element at the surface depth of 0.07 mm of the ICRU tissue equivalent sphere model can be obtained. T .

[0087]

[0088] Among them, H′(0.07,T) is the directional dose equivalent of the small volume element at the surface depth of 0.07 mm of the ICRU tissue equivalent sphere model under the condition of the β radioactive nuclide supported by the BSS2 standard device, Sv;

[0089] Φ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0095] S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Obtain the directional dose equivalent rate in the β radiation field Regional distribution measurement results;

[0096] According to formula (6), the absorbed dose rate at each measurement point and each moving point obtained in step S1 is calculated. The measurement result is multiplied by the corresponding absorption dose rate to directional dose equivalent rate conversion factor H′(0.07,T) / D from the database. T The measurement results of the directional dose equivalent rate H′(0.07) at the measurement point and each moving point can be directly calculated.

[0097]

[0098] Therefore, the directional dose equivalent rate in the β radiation field can be obtained. The regional distribution measurement results.

[0099] S4. Determine the directional dose equivalent rate of the β radiation field. Uniform region;

[0100] The area whose directional dose equivalent rate deviation from the measurement point (center location) does not exceed ±5% can be considered as the directional dose equivalent rate of the β radiation field. Uniform region.

[0101] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for measuring the directional dose equivalent rate in a uniform region within a β reference radiation field, characterized in that, The method includes the following steps: S1. Measuring absorbed dose rate Obtain the absorbed dose rate in the β radiation field The uniformity of the distribution; S2. Measure the energy spectrum of the β radiation field to obtain the energy spectrum region distribution of the β radiation field; S3. Establish a database of conversion coefficients between absorbed dose rate and directional dose equivalent rate to obtain the directional dose equivalent rate in the β radiation field. Regional distribution measurement results; S4. Determine the directional dose equivalent rate of the β radiation field. Uniform region.

2. The method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 1, characterized in that, Step S1 includes the following specific steps: S11. Place the sensitive volume center of the ionization chamber at the measurement point at the center of the normal of the β radiation field to ensure that the β rays are incident perpendicularly into the ionization chamber. S12. Based on the accumulated charge J fed back by the electrometer connected to the ionization chamber. a Read the data and calculate the absorbed dose rate at the measurement point. S13. Taking the measurement point as the center, on the vertical plane where the sensitive volume center of the ionization chamber is located, move the sensitive volume center of the ionization chamber 20.0 cm in each of the four directions: up, down, left, and right. The step size can be set to 1.0 cm to 2.0 cm to obtain the cumulative charge J at each moving point. a The absorbed dose rate at each moving point was calculated. Thus, the absorbed dose rate in the β radiation field is obtained. The uniformity of the distribution.

3. The method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 2, characterized in that, The ionization chamber is a thin-window ionization chamber.

4. The method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 2, characterized in that, The energy spectrum of the β radiation field is measured using a SiPIN detector, which is connected to a matching preamplifier, main amplifier, and digital multichannel. The PC connected to the digital multichannel acquires the energy spectrum of the β radiation field through matching software.

5. The method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 4, characterized in that, When performing energy spectrum measurements of the β radiation field using the SiPIN detector, a 3 mg·cm² area is placed in front of the SiPIN detector. 2 Aluminized polyester film.

6. The method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 4, characterized in that, When performing energy spectrum measurements of the β radiation field using the SiPIN detector, the absorbed dose rate in step S1 is compared with that in step S1. The method for measuring the uniformity distribution is the same as that for the SiPIN detector, which is placed at the same position as the sensitive volume center of the ionization chamber. After each set of cumulative charge readings is measured in the ionization chamber, the SiPIN detector is replaced to measure and record the energy spectrum distribution of the β radiation field at the current position.

7. A method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field according to claim 4, characterized in that, The energy spectrum distribution of the β-radioactive nuclide associated with the BSS2 standard apparatus was measured using the SiPIN detector.

8. A method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field according to claim 7, characterized in that, Step S3 includes the following specific steps: S31. Using MCNP simulation to establish an ICRU tissue sphere model, a method for calculating the conversion coefficient of absorbed dose rate to directional dose equivalent rate is obtained; S32. Establish a database of conversion coefficients for the conversion coefficients between absorbed dose rate and directional dose equivalent rate when the distribution of the β radiation field energy spectrum region of β radionuclides changes. S33. Combining the measurement points obtained in step S1 with the absorbed dose rate at each moving point. Obtain the directional dose equivalent rate in the β radiation field The regional distribution measurement results.

9. A method for measuring the directional dose equivalent rate in a uniform region in a β reference radiation field according to claim 8, characterized in that, Step S31 includes the following specific steps: S311. Establish a unit mass ICRU tissue sphere model using MCNP; S312. Given a monoenergetic β particle with a flux Φ and energy E, an incident particle is incident on a tissue sphere model from a specified orientation d at an incident angle θ. S313. Take a small volume element at a surface depth of 0.07 mm along the orientation d direction of the tissue sphere model, simulate and obtain the energy deposition dε and mass dm in the small volume element, and calculate the directional dose equivalent H0′(0.07,T) according to formula (4) in combination with the β particle quality factor Q. Where H0′(0.07,T) is the small volume element directional dose equivalent at a surface depth of 0.07 mm in the ICRU tissue sphere model under the condition of monoenergetic β particles with given fluence Φ and energy E, and Sv; Q is the β-particle quality factor, taken as Q = 1Sv / Gy; Energy deposition per unit mass within a small volume element, expressed in J / kg; S314. Remove other structures from the tissue sphere model, retaining only the small volume element at 0.07 mm, and obtain the deposition energy of monoenergetic β particles with fluence Φ and energy E within the small volume element, i.e., the absorbed dose D. T0 ; S315. Under the condition of monoenergetic β particles with given fluence Φ and energy E, obtain the conversion coefficient H0′(0.07,T) / D of the absorbed dose-directed dose equivalent of a small volume element at a surface depth of 0.07 mm in the ICRU tissue sphere model. T0 This is the conversion coefficient between absorbed dose rate and directional dose equivalent rate.

10. A method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field according to claim 9, characterized in that, Step S32 includes the following specific steps: S321. Combining the measurement of the energy spectrum region distribution of the β radionuclide in the BSS2 standard device using the SiPIN detector, the conversion coefficient H′(0.07,T) / D corresponding to the change in the energy spectrum region distribution of the β radiation field of the β radionuclide is calculated according to formula (5). T ; Wherein, H′(0.07,T) is the small volume element directional dose equivalent at a surface depth of 0.07 mm in the ICRU tissue sphere model under the condition of β radionuclide with BSS2 standard device, Sv; Φ E The fluence of the energy E of the β radionuclide for the BSS2 standard device, Sv; Q is the β-particle quality factor, taken as Q = 1Sv / Gy; Energy deposition per unit mass within a small volume element, J / kg; D T,E For the injection volume Φ E The deposition energy of a β-radioactive nuclide in a small volume element, E, for the BSS2 standard device; J / kg. D T Deposition energy of β-radionuclides in small volume elements for the BSS2 standard device, J / kg; S322. Establish a database of conversion coefficients for the conversion coefficients between absorbed dose rate and directional dose equivalent rate when the distribution of the β radiation field energy spectrum of β radionuclides changes.

11. A method for measuring the directional dose equivalent rate in a uniform region of a β reference radiation field according to claim 1, characterized in that, In step S4, the area where the deviation of the directional dose equivalent rate from the measurement point does not exceed ±5% is selected and identified as the directional dose equivalent rate of the β radiation field. Uniform region.

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