X and gamma reference radiation for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy Part 3:Calibration of area and personal dosemeters and the measurement of their response as a function of ene
Some standard content:
GB/T 12162.3—2004/1ISO 4037-3:1999GB/T12162 "X and Y reference radiation for calibration of dosimeters and dose rate meters and determination of their energy response" is expected to be structured in four parts:
-Part 1: Radiation characteristics and generation methods; -Part 2: Dose determination of reference radiation in the energy range of 8keV~1.3MeV and 4MeV~9MeV for radiation protection,
-Part 3: Calibration of site dosimeters and personal dosimeters and determination of their energy response and angular response; -Part 4: Calibration of site dosimeters and personal dosimeters in the field of low-energy X-ray reference radiation. This part is Part 3 of GB/T12162, corresponding to ISO4037-3:1999 "Calibration of site dosimeters and personal dosimeters and determination of their energy response and angular response" (English version). The consistency of this part with ISO4037-3 is equivalent. This part replaces GB/T8994-1988 "Calibration and determination of radiation protection instruments X, exposure rate meters". The main difference between this part and GB/T8994-1988 "Calibration and determination of radiation protection instruments X, Y exposure rate meters" in terms of technical content is: GB/T8994-1988 calibrates protection instruments and exposure rate meters based on exposure. In GB/T8994-1988, both site instruments and personal dosimeters are calibrated directly in free air according to the radiation dose. This part calibrates radiation protection L5] instruments according to the practical quantities [1,2.3,4] (ambient dose equivalent, directional dose equivalent, personal dose equivalent) defined by ICRU (the practical quantities defined by ICRU are based on the fact that the effective dose defined in ICRP Publication No. 60 L6 cannot be directly measured). Therefore, when the site dosimeter is calibrated according to the ambient dose equivalent and directional dose equivalent, it is carried out in free air, and when the personal dosimeter is calibrated according to the personal dose equivalent, it is carried out on the phantom recommended by ISO.
Appendix A of this part is informative.
This part is proposed and managed by China National Nuclear Corporation. The drafting unit of this part is China Institute of Atomic Energy. The main drafters of this part are Wei Kexin, Guo Wen and Li Jingyun. The previous versions of the standard replaced by this part are: GB/T8994-1988. 1
GB/T12162.3-2004/ISO4037-3:1999 X-ray and reference radiation for calibration of dosimeters and dose rate meters and determination of their energy response Part 3: Calibration of site dosimeters and personal dosimeters and determination of their energy response and angular response 1 Scope
This part of GB/T12162 specifies the method of calibrating site dose (rate) meters and personal dosimeters using reference radiation with average energy between 8keV~~1.3MeV and 4MeV9MeV. This part specifies the calibration procedures for different types of dose (rate) meters. For site dosimeters, portable and fixed dose (rate) meters are included; personal dosimeters include whole body and extremity dosimeters. At the same time, the recommended phantoms and conversion factors, uncertainty reports and guidance on the issuance of calibration records and certificates are given. This part also specifies the methods for determining the energy response and angular response of dosimeters. This part does not apply to the on-site calibration of fixed site dosimeters. Note 1: The term dosimeter is a general term for all dosimeters or dose rate meters used for personal or site monitoring. Note 2: Unless otherwise specified, the term kerma in this part refers to free air kerma. 2 Normative references
The clauses in the following documents become clauses of this part through reference to this part of GB/T 12162. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this part. However, parties to an agreement based on this part are encouraged to study whether the latest versions of these documents can be used. For all undated referenced documents, the latest versions apply to this part.
GB/T12162.1 X-ray and reference radiation for calibration of dosimeters and dose rate meters and for determination of their energy response Part 1: Radiation characteristics and generation methods (GB/T12162.1-2000, idtISO4037-1:1996) GB/T12162.2 X-ray and reference radiation for calibration of dosimeters and dose rate meters and for determination of their energy response Part 2: Dose determination with reference radiation in the energy range of 8keV to 1.3MeV and 4MeV to 9MeV for radiation protection (GB/T12162.2--2004, ISO4037-2:1997, IDT) JJF1059 Evaluation and expression of uncertainty in measurement 3 Terms and definitions
The following terms and definitions apply to this part of GB/T12162. 3.1
dose equivalent
The product of the absorbed dose D at the midpoint of the tissue and the quality factor Q, that is: H=QD
The unit of dose equivalent is joule per kilogram (J·kg\1), and the special name is sievert (Sv). For the photon and electron radiation involved in this standard, the quality factor is 1.
ambient dose equivalentH*(10)
The dose equivalent at a point in the radiation field is the dose equivalent produced by the corresponding extended unidirectional field at a depth of 10 mm in the ICRU sphere on the radius opposite to the unidirectional field. The unit of ambient dose equivalent is joule per kilogram (J·kgl), and the special name is sievert (Sv). NOTE: In an extended unidirectional field, the photon fluence and energy distribution in the entire volume involved have the same values as at the check point and the field is unidirectional. 3.3
directional dose equivalent H'(0. 07;2)
The dose equivalent at a point in a radiation field is the dose equivalent produced by the corresponding extended field at a depth of 0.07 mm on a radius of a specified direction α within the ICRU sphere. The unit of directional dose equivalent is joule per kilogram (J kg), the special name is sievert (Sv). NOTE 1: In a unidirectional field, the direction can be represented by the angle α between the radius of the reverse radiation field and the specified radius. When α = 0, H(0.07;α) can also be written as H(0.07).
NOTE 2: In an extended field, the photon fluence and its angle and energy distribution in the volume involved have the same values as at the actual field at the measurement point. 3.4
personal dose equivalentpersonal doseequivalentHp(d)
The dose equivalent of soft tissue at a certain depth d below a specified point on the human body. For weakly penetrating radiation, the skin dose equivalent is taken as a depth of 0.07 mm. The personal dose equivalent at this depth is expressed as Hp(0.07). For strongly penetrating radiation, the dose equivalent at a depth of 10 mm is usually used and expressed in a similar way, i.e. H(10). The unit of personal dose equivalent is joule per kilogram (J·kg-1), the special name is sievert (Sv)). www.bzxz.net
Note: The definition of soft tissue is the same as that in ICRU Report No. 51. 3.5
influence quantityinfluence quantity
influence parameterinfluence parameter
A quantity that affects the measurement result but is not the purpose of the measurement. For example, the reading of a non-sealed ionization chamber dosimeter is affected by the surrounding atmospheric temperature and pressure. Although these two quantities are needed to determine the value of the dose, measuring these two quantities is not the main purpose. 3.6
Reference conditions The conditions used for the performance test of the measuring instrument, that is, the conditions that ensure the validity of the comparison of the measurement results. Note 1: The reference conditions can be considered as a set of influencing quantities whose calibration factors are valid without any correction. Note 2: The quantity to be measured can be freely selected according to the characteristics of the instrument to be calibrated. However, the quantity to be measured must not be an influencing basis. 3.7
Standard test conditions Standard test conditions A set of values (or ranges of values) of influencing quantities or instrument parameters used for radiation field dose measurement or calibration and determination of instrument response.
Note: Ideally, calibration should be performed under reference conditions. However, reference conditions are not always achievable (e.g., pressure of the surrounding air) or are not easily achievable (e.g., ambient temperature), so values within a small interval around the reference conditions are permitted. In principle, the deviation of the calibration factor due to the deviation of the conditions from the reference conditions should be corrected, but in practice, an uncertainty is often set as a criterion for determining which influencing quantities must be corrected or whose effects are only included in the uncertainty. In type testing, the values of influencing quantities not for inspection purposes are fixed within the range of standard inspection conditions. The standard inspection conditions and reference conditions used in this part are given in Tables A.1 and A.2 of Appendix A. 3.8
Calibration conditions The actual conditions during calibration within the range of standard test conditions. 3.9
reference pointreference point
A point on a dosimeter that is placed at the check point during calibration or testing. 2
Note. The measurement distance refers to the distance from the radiation source to the reference point of the dosimeter. 3.10
conventional true value of a quantityGB/T12162.3—2004/ISO4037-3:1999The best estimate of the quantity being measured. This value is determined by a primary or secondary standard; or by a reference instrument calibrated with a primary or secondary standard.
For example: Within an organization, the measurement results obtained by a secondary standard instrument are regarded as the conventional true value of the quantity being measured. Note: The conventional true value is usually considered to be close enough to the true value that the difference is considered insignificant for a given purpose. 3.11
reference directionreferencedirection
A specified direction in the coordinate system where the dosimeter is located, relative to which the angle of the radiation incident direction in a unidirectional radiation field is given. 3.12
reference orientationreference orientation The orientation of the dosimeter when the radiation direction coincides with the reference direction of the dosimeter. 3.13
point of test
A point in the radiation field where the reference point of the dosimeter is placed during calibration or testing, and where the agreed true value of the quantity being measured is known.
responseresponse
The ratio of the indicated value M of the dosimeter to the agreed true value of the quantity being measured at the test point. Usually the type of response should be stated. For example: Response relative to the ambient dose equivalent H*(10): R= M/H*(10)
Note 1: The response may change with the magnitude of the quantity being measured, in which case the dosimeter is said to have a nonlinear response. Note 2: The response usually changes with the energy and directional distribution of the radiation being measured. Therefore, the response is usually regarded as a function R(Q,E) of the energy E of the monoenergetic radiation being measured and the direction Q of the unidirectional radiation being measured. R(E) is the energy response, R(Q) is the angular response, and 2 can be expressed as the angle α between the reference direction of the dosimeter and the direction of the external unidirectional radiation field.
Note 3: If the dosimeter contains multiple detectors, and is exposed in a radiation field with different energies and radiation directions, the algorithm for evaluating its response may not be a simple addition. For example, the contribution to the dose equivalent has two parts, H1 and H2, and the sum of the two response readings may be different from the reading of a single exposure with H1 + H2, that is, MHI + MH: ≠MH, + Hz. In this case, the function R(Q, E) in the above note is not sufficient to characterize the characteristics of the dosimeter in all radiation fields. 3.15
calibration
Quantitatively determine the relationship between the dosimeter reading and the measured value under a set of controlled standard test conditions. Note: Usually, the calibration conditions are a set of standard test conditions (see Appendix A.1). Routine calibration to verify the calibration done by the manufacturer or to verify whether the calibration factor is sufficiently stable during continuous long-term use of the dosimeter can be carried out under simplified conditions. Generally speaking, routine calibration methods are formulated based on the results of type tests. Routine calibration is often used to give a batch calibration factor or a single-machine calibration factor. 3.16
Calibration factorcalibration factor
The conventional true value H of the quantity measured by the dosimeter divided by the dosimeter reading M (corrected to reference conditions). For example: The calibration factor for personal dose equivalent is given by the following formula: N = H,(d)/M
Note 1: The calibration factor N is dimensionless when the dosimeter indicates the quantity being measured. When the dosimeter accurately indicates the conventional true value, its calibration factor is 1. Note 2: The reciprocal of the calibration factor is equal to the response under reference conditions. The calibration factor is only relative to the reference conditions, while the response can be for any3
GB/T 12162.3—2004/ISO 4037-3:1999 conditions during measurement.
Note 3: The value of the calibration factor may change with the value of the quantity being measured. In this case, the dosimeter is said to have a nonlinear response. 3.17
Normalization
Calibration factor multiplication by a factor in order to give a better estimate of the value of the quantity being measured within a certain range of influence quantities Note: Normalization may be performed when the dosimeter is regularly used under conditions different from the reference conditions. In this case, the normalization should be based on the difference between the response under the reference conditions and the normal operating conditions.
kerma todoseequivalent conversioncoefficienthk
The quotient of the dose equivalent H at a point in the radiation field and the air kerma K. hk - H/K.
Note 1: The conversion factors given in Chapters 5 and 6 are based on the average of the spectral distribution of monoenergetic data from ICRP Publication 74 [17]. Note 2: The conversion factors from air kerma to dose equivalent must indicate the type of dose equivalent, such as ambient dose equivalent, directional dose equivalent and personal dose equivalent. The conversion factor hk is energy dependent and, for H,(10;α) and H'(0.07;α), also dependent on the directional distribution of the incident radiation. It is therefore possible to consider the conversion factor as a function h(E) of the monoenergetic photon energy E at several angles. This set of basic data given in this way is often called the conversion function.
back-scatter factorback-scatter factorThe ratio of the air kerma rate in front of a phantom to the free air kerma rate at the same location. Note 1: The field considered here is unidirectional and the direction of incidence is orthogonal to the phantom surface. Note 2: The value of the back-scatter factor depends on the position of the check point (and the distance from the phantom surface and the beam axis), the beam diameter, the size of the phantom, as well as the material and the radiation energy.
4 General calibration procedure for field and personal dosimeters 4.1 General principles
4.1.1 Radiation quality
All radiation quality used shall be generated and selected in accordance with the requirements of GB/T 12162.1. Generally, the radiation quality should be selected according to the energy, dose or dose rate range given by the tested dosimeter. Table 1 shows all the radiation qualities specified in GB/T12162.1 and their average energy E of the fluence spectrum. In Table 1, for X-radiation, the letters F, L, N, W and H represent the fluorescence, low air kerma, narrow spectrum, wide spectrum and high air kerma series of radiation qualities, respectively, followed by the element symbol of the radiator of fluorescence radiation or the generation potential of filtered beam X-radiation. The reference radiation generated by the radiation source is represented by a combination of the letter S and the element symbol of the radionuclide. The reference radiation generated by the nuclear reaction is represented by the letter R followed by the element symbol of the target element that emits the radiation. The dose measurement of these radiation fields should be carried out in accordance with GB/T12162.2. The radiation quality specified in Table 1
Radiation quality
Radiation quality
Radiation quality
Radiation quality
Radiation quality
Radiation quality
Radiation quality
Radioactive nuclides
Radiation quality
Indicates the averaging of the entire fluence spectrum.
4.1.2 Conversion factors
Table 1 (continued)
Radiation quality
Radiation quality
GB/T 12162.3—2004/ISO 4037-3: 1999 Radiation quality
High energy photon radiation
12C(p,p)\C
19 F(p,α)160
(n,y) capture of Ti
(n,y) capture of Ni
Radiation quality
In Chapter 5, Chapter 6 and Appendix A of this Part.2, the irradiation distance is the distance from the focal spot of the X-ray tube (or the geometric center of the radiation source) to the check point (on which the reference point of the calibrated dosimeter should be placed). For X-ray fluorescence radiation and RC, RF, R-radiation, the irradiation distance is the distance from the center of the radiator or the surface of the target producing the radiation to the check point. If a range of distances is given in the table, the conversion factors in the above table can be used without correction within this distance range. The symbols used in the expressions of conversion factors in Chapter 5, Chapter 6 and Appendix A.2 of this part are explained as follows using hk (0.07; E, α) as an example: h (0.07; E, α) refers to the conversion factor for the directional dose equivalent of photon radiation with energy E from the air kerma K. The angle between the reference direction of the dosimeter and the radiation direction is α. If the superscript "1" is replaced by an asterisk, it means the ambient dose equivalent, and if it is replaced by the letter "p" and written as a subscript, it means the personal dose equivalent. For radiation with a certain spectral width, the symbol F is replaced by the letter designating the particular series of reference radiations in accordance with Table 1, i.e. F, I, N, WHS or R. The values of the conversion factors for monoenergetic radiation given in Tables 2, 8, 15, 21, 27 and Table A.3 of this standard [16] are considered to be free of uncertainty. Unless otherwise stated, the conversion factors given in other tables of Clauses 5 and 6 should be considered to be accompanied by a standard uncertainty of 2 %. This uncertainty arises from the difference between the spectrum used to calculate the conversion factor and the spectrum actually present at the test point [8]. For tube voltages below 30 kV, and especially for high air kerma series, the values of the actual conversion factors h(10;F) and hpk(10;E,α)) for a given test set-up may deviate by more than 2 % from the nominal values given in the tables of Clauses 5 and 6. Radiation qualities that are sensitive to small changes in the energy distribution and the corresponding conversion factors are highlighted in the corresponding tables by way of notes. In this case, the 2% uncertainty may not be sufficient and a proper uncertainty assessment or more reliable conversion factor values may be required. If the radiation quality listed in Table 1 is not included in the table of conversion factors hk(10;E) and h(10;E,α), this means that no reliable value can be given. NOTE: For low energy photons, when the air kerma is mainly contributed by the low energy part of the spectrum, small differences in the energy distribution can lead to significant changes in the conversion factor, because the main contribution of the air kerma comes from the low energy part of the spectrum, while the main contributions of h" (10) and h, (10) come from the high energy part of the spectrum [19]. Differences in energy distribution from one experimental arrangement to another may be caused by many factors, such as anode angle, anode surface roughness, tungsten evaporation on the tube window, the use of a monitoring ionization chamber in the beam, deviations of filter thickness from nominal thickness, the distance from the focal spot to the test point air and the atmospheric pressure during the measurement. For fluorescence radiation, the need to reduce the scattered radiation contribution to an acceptable level may require optimization of the test conditions by using thin radiators or/and reducing the tube voltage. 5
GB/T 12162.3—2004/1SO 4037-3: 19994.1.3 Standard test conditions
Calibration and determination of the response (see 4.1.4) shall be carried out under standard test conditions. The range values of the standard test conditions for radiation-related influencing quantities and other influencing quantities are given in A.1 and A.2 respectively. 4.1.4 Variation of influencing quantities
When the effect of a variation of an influencing quantity on the response is determined by measurement, the other influencing quantities should be kept at a fixed value within the standard test conditions, otherwise an explanation should be given.
Note: In some cases, it is important to vary the influencing quantity in such a way that the response of the instrument being tested remains constant. For example, when testing the energy response of a counter tube dosimeter over a dose rate range where the counter tube has a significant dead time, it is desirable that the test be carried out under conditions of constant reading indication rather than constant dose rate. For so-called super-linear displays of thermoluminescent dosimeters The same applies. However, it should also be noted that it is usually recommended to perform instrument verification under conditions where the instrument dose or dose rate response is essentially linear. 4.1.5 Verification points and reference points
The reference point of the dosimeter should be placed at the verification point during measurement. The manufacturer should give the reference point and reference direction of the dosimeter. The reference point should be marked on the surface of the dosimeter. If this is not possible, it should be stated in the accompanying documents of the dosimeter. All distances from the radiation source to the dosimeter are considered to be the distance from the radiation source to the dosimeter reference point. If the calibrated dosimeter has no information on the reference point or reference direction, it should be determined by the calibration laboratory and stated in the calibration certificate. Note: In the case of a point source and no scattered radiation and photon absorption, the dose rate is inversely proportional to the square of the distance 1. A position deviation of △1 of the dosimeter reference point in the beam along the beam direction at a distance of 1 will result in a calibration factor of 2△l/1 Relative error A position deviation of △^ between the reference point and the beam axis in the direction perpendicular to the beam axis will result in a relative error of (A)/l)\. When there is scattered radiation and the radiation source has a certain linearity, the above approximation is limited to the case where the values of △ and I are very small compared to 1.
4.1.6 Rotation axis
When determining the angular response, it is necessary to rotate the field dosimeter or personal dosimeter to measure the entire body model. In order to determine the change of response with the direction of radiation injection, the dosimeter should be rotated around at least two rotation axes. The two rotation axes should be perpendicular to each other and pass through the reference point of the dosimeter. Figure A.1 gives an example of geometric conditions. 4.1.7 Status of the calibrated dosimeter
Before calibration, the dosimeter should be checked to confirm that it is in good working condition and free of radioactive contamination. The operating procedures and working methods of the dosimeter should be carried out according to the instructions.
4.1.8 Electron Range Effects
Electrons with energies exceeding 65 keV and 2 MeV can penetrate 0.07 mm and 10 mm of ICRU tissue, respectively. Therefore, when the photon reference radiation field may produce electrons with energies equal to or higher than the above, the electron range effect should be considered. A more detailed discussion is given in Appendix A, 3. The following is the procedure for handling this situation. For the quantities H(0.07) and H.(0.07), within the energy range covered by Tables 2 to 7, Tables 15 to 26, and Tables A.3 to A.8. Due to the presence of air and other materials (such as monitoring ionization chambers), electron balance is fully established at the reference depth when the photon energy is below 250 keV L10]; when determining the response at higher energies, calibration under electron balance conditions becomes meaningless and is replaced by calibration in a suitable electron reference radiation field 191, and no special attention is required for electron balance. Appendix A.3 gives an advanced explanation. For the calibration of energies from S-Cs to 9MeV and with the quantities H*(10) and H(10), the conventional true value of the air kerma at the check point should first be determined in accordance with the provisions of GB/T12162.2. Then the reference point of the dosimeter is placed at the check point and a PMMA (plexiglass) plate of sufficient thickness to ensure complete electronic balance is placed in front of the dosimeter (site instrument) or the combination of the dosimeter and the phantom (personal dosimeter). When considering the correction for the change in the radiation field due to the introduction of the plexiglass plate, the conversion coefficient should be multiplied by the correction factor kpMMA given in Table 14 and Table 33. The cross-section of the plexiglass plate should be 30cmX30cm and the thickness should be the values given in Table 14 and Table 33. Note: For irradiation with a phantom or some site dosimeters, the plexiglass plate should be placed at a certain distance in front of the dosimeter or the combination of the dosimeter and the phantom so that the plexiglass plate does not need to be rotated when determining the angular response. 4.2 Methods for determining calibration factors and responses
4.2.1 Operation of standard instruments
The operation of standard instruments shall be consistent with the calibration certificate and the instrument manual, such as zero adjustment, warm-up time, battery check, application of range or scale 6
The calibration cycle of standard instruments shall comply with relevant national regulations. GB/T 12162.3—2004/ISO 4037-3:1999The instrument shall be measured regularly using a radionuclide test source or a calibrated radiation field to determine that the reproducibility of the standard instrument is within ± 2% of the value given in the certificate. If necessary, corrections shall be made for the decay of the radiation source and the deviation of the air density from the reference conditions. When calibration is performed by substitution, the use (see 4.2.3.1 and 4.2.3.2) or non-use (see 4.2.2.1 and 4.2.2.2) of the monitor shall be determined based on the output stability of the radiation source.
Standard instruments can be of two types: those that measure more basic dosimetric quantities, such as air kerma, and those that directly measure quantities used for calibration. For instruments of the first type, the appropriate conversion factor h is used in the formulas of 4.2.2 to 4.2.5, and for instruments of the second type, the conversion factor h is l.
4.2.2 Measurements without monitors
Normally, reference radiation fields produced by radionuclides do not require monitors. However, for X-ray reference radiation fields, the use of monitors is generally recommended. 4.2.2.1 Calibration
This procedure can be used when the air kerma rate of the radiation field can remain stable within a certain range during the calibration period. The detector of the dosimeter is then placed at the same checkpoint as the standard instrument and irradiated for the same time. The calibration factor N of the dosimeter can be expressed as: hNAMA
Where:
N--calibration factor of the calibrated dosimeter; h--conversion coefficient from air kerma to dose equivalent; NA--calibration factor of the standard instrument;
M^-measurement value of the standard instrument, that is, the reading value multiplied by the correction factor for the difference in air density; Ms--measurement value of the calibrated dosimeter, that is, the reading value multiplied by the correction factor for the difference in air density. 4.2.2.2 Determination of energy response and angular response Under conditions that are not necessarily the same as the reference conditions, the response of the dosimeter is given by the following formula: Mg(E,α)
R(E,α) =
h(E,a)NAMAkek
（2）
In formula (2), kE and k are correction factors for the readings to take into account the differences in the radiation quality and radiation direction of the standard instrument under reference conditions and actual measurement conditions. The other symbols have the same meanings as in 4.2.2.1. The response of the dosimeter is often given as a relative response r relative to the response under reference conditions: r = R.
Note: Relative responses are usually used to describe angular and energy responses (see 3.2.10). 4.2.3 Measurements using monitors
4.2.3.1 Calibration
（3）
Moderate changes in the air kerma rate over time can be corrected by using monitors and sequential irradiation standard instruments and dosimeters. This technique is often used in X-ray devices to correct for changes in the air kerma rate when the standard instrument and the dosimeter are alternately placed at the checkpoint. The measurement values MA and M of the standard instrument and the dosimeter placed successively at the checkpoint should correspond to the measurement values of the monitor. The calibration factor N can be expressed as:
(MA)(mB
Ng hNA(
where:
mA is the measurement value of the monitor when the standard instrument is irradiated; mB is the measurement value of the monitor when the calibrated dosimeter is irradiated. The meaning of h and NA is shown in 4.2.2.1.
·(4)
Note 1: In practice, if the standard instrument and the calibrated dosimeter are irradiated successively in a very short time and the environmental conditions of the monitor remain unchanged, it is not necessary to adjust 7
GB/T 12162.3—2004/IS0 4037-3:1999 The readings of the monitor are corrected to the reference conditions. Note 2: When the monitor has good long-term stability (see 8.2 of GB/T 12162.2), the monitor calibrated with the standard instrument can be used as the transfer instrument. 4.2.3.2 Determination of energy response and angular response (see 4.2.2.2) Under conditions that are not necessarily the same as the reference conditions, the response of the dosimeter is given by the following formula: mAMB (E, α) || tt || R (E, α) =
h(E,a)NAmgMAkek.
The relative response is given by formula (3).
4.2.4 Measurement of simultaneous exposure of standard instrument and dosimeter 4.2.4.1 Calibration
In some cases (see note below), calibration can be performed by placing the standard instrument and the calibrated dosimeter symmetrically relative to the radiation field axis at the same distance from the radiation source and irradiating them simultaneously. The distance between the two detectors should be large enough to ensure that the reading of one instrument is affected by no more than 2% by the other instrument.
In order to eliminate the influence of radiation field asymmetry, the two instruments should be exchanged and the measurement should be repeated, and the geometric mean of their readings should be taken. The calibration factor NB is given by the following formula:
MA)(MA)
NghNAN
V(M/(MB /2
The meaning of symbols in formula (6) is the same as in 4.2.2.1, and the subscripts 1 and 2 refer to the first irradiation and the second irradiation respectively. (6)
Note: This procedure is mainly used in cases where there is no phantom calibration, such as field instrument calibration. In particular, it is used for reference radiation generated by accelerators or when non-collimated sources are used (see GB/T12162.1).
4.2.4.2 Determination of angular response and energy response Under conditions that are not necessarily the same as the reference conditions, the response of the dosimeter is given by the following formula: [(Mn(F,a)(M(E,a)
R(E,α) =
h(E,a)NAkrk. N
The meaning of symbols is the same as in 4.2.2.1 and 4.2.2.2, and the subscripts 1 and 2 refer to the first irradiation and the second irradiation respectively. The relative response is obtained by formula (3).
4.2. 5 Determination of calibration factors and responses in radiation fields of known ? For radiation fields with known air kerma rates, the calibration factor N of the dosimeter is expressed as: Ne = M.
where:
K. — air kerma;
Mg measured value of the dosimeter (under reference conditions); h has the meaning as in 4.2.2.1.
5 Special calibration procedures for site instruments
5.1 General principles
· (7)
These principles apply to the calibration of portable and fixed site dosimeters in reference radiation. Site dosimeters include active and passive devices. These principles do not apply to the in situ calibration of fixed mounted site dosimeters. Site dosimeters should be calibrated in free air (without phantoms). Measurements of the response may need to be made in the energy range 8 keV to 9 MeV and at different irradiation distances depending on the irradiation equipment. 5.3.1 and 5.3.2 contain data on the conversion factor h from air kerma to practical quantities H (10) and H, (10) for the reference radiation specified in GB/T 12162.1. 5.3.1.1 and 5.3.2.1 give the conversion factors for the unscattered conditions of a parallel broad beam of monoenergetic photons. In practice, calibration is always performed in a diverging beam. The conversion factors are therefore given relative to a reference distance between the radiation source and the test point. When the reference distance is given together with the radiation incident direction α, α is the angle between the reference orientation of the dosimeter and the actual orientation in the radiation field.
5.2 Quantities to be measured
GB/T 12162.3—2004/ISO 4037-3:1999 For field instruments, the quantities to be measured shall be the ambient dose equivalent H* (10) and the directional dose equivalent H (0.07). 5.3 Conversion coefficients
Conversion coefficients from air kerma to H' (0.07): 5.3.1
Conversion coefficients for monoenergetic radiation are shown in Table 2;
Conversion coefficients for fluorescence radiation and 241Am are shown in Table 3; conversion coefficients for low air kerma rate series are shown in Table 4; conversion coefficients for a narrow spectrum series are shown in Table 5;
Conversion coefficients for a broad spectrum series are shown in Table 6;
Conversion coefficients for high air kerma rate series are shown in Table 7. Conversion factors from air kerma to H* (10): 5.3.2
Conversion factors for monoenergetic radiation are shown in Table 8;
Conversion factors for fluorescence radiation are shown in Table 9;
Conversion factors for low air kerma rate series are shown in Table 10; conversion factors for narrow spectrum series are shown in Table 11; conversion factors for wide spectrum series are shown in Table 12; conversion factors for high air kerma rate series are shown in Table 13; conversion factors for radionuclides and high-energy reference radiation are shown in Table 14. Table 2
2Conversion factor hk(0.07; E, α) of the air kerma K in the ICRU sphere to dose equivalent H(0.07) for monoenergetic parallel photon radiation (extended field)hk(0. 07; E, a)/(Sv/Gy)
E/(keV)
GB/T 12162.3—2004/ISO 4037-3: 1999E/(keV)
Table 2 (continued)
h'k(0.07; E, a)/(Sv/Gy)
Note: The energy range covered by Tables 2 to 14 is limited to the approximate range within which electron balance is reliably established at a depth of 0.07 mm. For higher
energies, the quantity H' loses its value, so the higher energy range H' is the limited quantity. Table 3
For the radiation quality (extended field) specified in GB/T12162.1, the conversion coefficients hk (0.07; F, α) and hk (0.07; S, α) of the air kerma in the ICRU sphere to the dose equivalent H (0.07), reference distance 2mhx (0.07; F, a) and hx (0.07; S, a)/(Sv/Gy) radiation quality
irradiation distance/m
1.0～1.0~
fF-Nd|F-Srn
F-Au|F-Pd
radiation quality
irradiation distance/m
0. 000.00
Table 3 (continued)
GB/T12162.3-2004/IS04037-3:1999h'(0.07;F,a) and h'k(0.07;S,α)/(Sv/Gy)F-Mo
For the radiation quality (extended field) specified in GB/T12162.1, the kerma K of air in the ICRU sphere. Conversion coefficient h'k (0.07; L, α) to dose equivalent H (0.07), reference distance 2mh'k(0.07; l., a)/(Sv/Gy)
Radiation quality
Irradiation distance/m
1. 0~2. 01. 0~ 2. 01. 0~ 2. 01. 0~ 2. 01,1.0~3.01.0~3.01
1.0~3.01.0~3.01.03.01.0~3.01.00.93
For the radiation quality (extended field) specified in GB/T12162.1, the kerma K of air in the ICRU sphere. Conversion coefficient h (0.07; N, α) to dose equivalent H (0.07), reference distance 2mh'r (0.07; N.α) / (Sv / Gy) | | tt | | radiation quality | | tt | | irradiation distance / m | | tt | | N-250N-300
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.