Large-scale individual thyroid monitoring following nuclear accidents by means of non-spectrometric devices

Abstract

In order to properly respond to an emergency caused by an accident in a nuclear power plant with a spread of radionuclides in the atmosphere, we propose a field procedure to perform a large-scale individual thyroid monitoring of internal contamination due to inhalation of 131I, by means of non-spectrometric equipment, in particular dose rate meters. Specific attention is paid to the individual monitoring of children, because of the very high radiosensitivity of the child’s thyroid to the carcinogenic effects of ionising radiation. The device performance was evaluated by measuring mock iodine sources provided in the Child and Adult Thyroid Monitoring After Reactor Accident (CAThyMARA) intercomparison and, just for a scintillator dose rate meter, by means of 60 s acquisitions of healthy volunteers’ thyroids. All the devices showed a remarkable accuracy in quantification of equivalent 131I activity in the thyroids of persons of all ages. The selected scintillator dose rate meter showed detection limit values resulting in a maximum committed equivalent dose to thyroid HT, assuming an acute 131I inhalation occurred five days before the measurement, equal to 10 mSv (related to five-year-old children). Considering the level of HT values associated with the calculated detection limit activities, the proposed procedure has a significant sensitivity to be used for fast internally thyroid monitoring in nuclear or radiological emergencies, allowing daily monitoring a large amount of individuals.

Thyroid doses in Ukraine due to 131I intake after the Chornobyl accident. Report I: revision of direct thyroid measurements

“…The conversion coefficient, C a , of a device depends on anthropometry of the measured individual, i.e., thyroid size and thickness of tissue overlying the thyroid gland, which both depend on age (e.g., Beaumont et al 2018;Venturini 2003;Vilardi et al 2018;Yunoki 2019). Agespecific C a -values for the most commonly used Ukraine gamma-spectrometers (i.e., the GTRM-01ts and the NK which accounted for 70.5% of all spectrometric measurements) were calculated in this study using Monte Carlo simulations of photon and electron transport (Briesmeister 1997).…”

Large-scale individual monitoring of internal contamination by gamma-emitting radionuclides in nuclear accident scenarios

“…Such investigation is even more useful when it can be performed in the field and on a large number of people. The measurement campaigns carried out following the Fukushima accident are a great example of such a situation, and several techniques have been examined with the aim of optimising dose assessments for members of the public [1][2][3][4].…”

“…Measurements specific to the thyroid gland can be performed with a rate meter (a widely used instrument). This technique possesses adequate sensitivity for mass screening when measurements are performed at least two days after radioiodine incorporation [3]. However, for achieving short-lived iodine radioisotope ( 132 I, 133 I, 134 I and 135 I) identification and quantification as well, the application of spectrometric methods with high-energy resolution detectors is required (mandatory if measurements are performed earlier) [3].…”

“…This technique possesses adequate sensitivity for mass screening when measurements are performed at least two days after radioiodine incorporation [3]. However, for achieving short-lived iodine radioisotope ( 132 I, 133 I, 134 I and 135 I) identification and quantification as well, the application of spectrometric methods with high-energy resolution detectors is required (mandatory if measurements are performed earlier) [3]. In such a context, the spectrometric equipment is fully capable of assessing the level of thyroid contamination due to all the radioiodine isotopes.…”

“…This method can also be optimised by performing measurements in an ad hoc site. Moreover, the spectrometric method proposed here can be carried out in conjunction with the thyroid measurements proposed by Vilardi et al in [3]. The combined use of both methods allows us to decrease the time needed to identify persons who may urgently need medical treatment and follow-up [5,6].…”