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Calibrations and irradiations of radiation protection dosemeters according to new recommendation of ICRU (International Commission on Radiological Protection) possible in photon and beta reference radiation fields

30.09.2021

The International Commission on Radiation Units and Measurements (ICRU) has recommended new quantities for radiation protection in its Report No. 95. Values were calculated for these quantities to be able to estimate the consequences for the calibrations or irradiations of radiation protection dosemeters in the newly recommended radiation protection quantities with photon and/or beta radiation.

The International Commission on Radiation Units and Measurements (ICRU) has recommended new measurement quantities for radiation protection in its report No. 95 [1]. However, these have not been officially adopted yet at international (IAEA, International Atomic Energy Agency) or European (EU, European Union) level by a corresponding amendment to the respective radiation protection basic standards. To be able to estimate the possible consequences of such an adoption of the proposed quantities metrologically at an early stage, the values required for this were calculated. With them, calibrations or irradiations of radiation protection dosemeters in the newly proposed radiation protection quantities with photon and/or beta radiation are possible [2],[3].

The calculated values show that a change of the measurands, depending on the type of radiation and energy range, will have a massive impact on the response of previously ideal dose meters, see Figure 1 (for photon radiation) and Figure 2 (for beta radiation):

  • This is true for photon radiation for dosemeters estimating dose in local skin and the dose in the lens of the eye in the rather irrelevant energy range below 10 keV (see Fig. 1, top and middle) and
  • especially for dosemeters estimating effective dose in the important middle energy range up to about 70 keV (see Fig. 1, bottom).
  • For beta radiation, massive changes will occur in the response for dosemeters for the estimation of the dose in the lens of the eye (see Fig. 2, bottom).

Therefore, a change of the official quantities from the current to the new ones, proposed by the ICRU, should only be considered after carefully balancing the advantages against the disadvantages.

 

Fig. 1: Photons radiation: Top: Ratios of the conversion coefficients for the current quantities used to estimate the dose in local skin, Hp(0.07) and H'(0.07), for personal and area dosemeters, respectively, and the corresponding newly proposed quantities, Dp local skin, for a finger ring dosemeter (top left) and for a corresponding area dosemeter, D'local skin, respectively (top right). These ratios represent the response of a corresponding dosemeter with respect to the measurand published in ICRU 95, assuming the respective dosemeter has an ideal response of 1.0 with respect to the corresponding current quantity. In the middle, the corresponding ratios for the current quantities used to estimate the dose in the lens of the eye, Hp(3) and H'(3), and the corresponding newly proposed quantities, Dp lens and D'lens, respectively, for an eye lens dosemeter, are shown. At the bottom, the corresponding ratios for the current quantities used to estimate the effective dose, Hp(10) and H*(10), and the corresponding newly proposed quantities, Hp and H*, for whole-body and area dosemeters, respectively, are shown. The red dashed lines represent the performance requirements for dosemeters according to the corresponding IEC (International Electrotechnical Commission) international standard. The uncertainty bars are mostly smaller than the symbols and therefore not visible.

Fig. 2: Beta radiation: Top: Ratios of the conversion coefficients for the current quantities used to estimate the dose in local skin, Hp(0.07), for personal extremity and whole-body dosemeters, respectively, and the corresponding newly proposed quantities, Dp local skin, for extremity dosemeters (top left) and D'local skin, for whole-body dosemeters (top right). These ratios represent the response of a corresponding dosemeter with respect to the measurand published in ICRU 95, assuming the respective dosemeter has an ideal response of 1.0 with respect to the corresponding current quantity. At the bottom, the corresponding ratio for the current quantity used to estimate the dose in the lens of the eye, Hp(3), and the corresponding newly proposed quantity, Dp lens, for an eye lens dosemeter is shown. The red dashed lines represent the performance requirements for dosemeters according to the corresponding IEC (International Electrotechnical Commission) international standard. The uncertainty bars are mostly smaller than the symbols and therefore not visible.

 

Literature

[1] International Commission on Radiation Units and Measurements: “Operational Quantities for External Radiation Exposure”, Journal of the ICRU 2020, Vol. 20(1) 3‑4, https://doi.org/10.1177/1473669120966224

[2] R. Behrens and T. Otto: “Conversion coefficients from total air kerma to the newly proposed ICRU/ICRP operational quantities for radiation protection for photon reference radiation qualities”, J. Radiol. Prot. in press, 2020, https://doi.org/10.1088/1361-6498/abc860

[3] R. Behrens: “Conversion coefficients from absorbed dose to tissue to the newly proposed ICRU/ICRP operational quantities for radiation protection for beta reference radiation qualities”, J. Radiol. Prot. in press, 2021, https://doi.org/10.1088/1361-6498/abf94f

Contact:

Opens local program for sending emailRolf Behrens, Department 6.3, Working Group 6.34