NaCl pellets for prospective dosimetry using optically stimulated luminescence: Signal integrity and long-term versus short-term exposure

Abstract

Optically stimulated luminescence (OSL) signal properties of pellets from three types of NaCl (two household salts and one analytical grade salt) were investigated for their use in prospective dosimetry. Special attention was given to the OSL signal behaviour with time. The readout protocol was optimised in terms of preheat temperature, and the OSL signal yield of the NaCl pellet with time as well as the fading of the OSL signal with time was investigated. The effects of acute and chronic irradiations were compared. Irradiations and readout were performed using a Risø TL/OSL reader (TL/OSL-DA-15, DTU Nutech, Denmark). The optimal preheat temperature was determined to be 100 ºC, yielding OSL signals similar to a 1 h pause before OSL signal readout. There was no OSL signal fading observed as a function of time, but a decrease in the OSL signal yield of the NaCl pellets with time resulted in an apparent inverse fading when converting the OSL signal to an absorbed dose. For chronic radiation exposures of up to five weeks, the sensitivity of the NaCl pellets was found to be stable. The results of this study show that the use of NaCl pellets for prospective dosimetry is a promising, cost-effective, and accessible complement to commercially available alternatives for accurate absorbed dose determinations.

The 2019–2020 EURADOS WG10 and RENEB Field Test of Retrospective Dosimetry Methods in a Small-Scale Incident Involving Ionizing Radiation

“…The reader is equipped with an internal 90 Sr/ 90 Y source (20 MBq on April 9, 2009) with an absorbed dose rate to NaCl of 0.70 6 0.014 mGy/s at the irradiation position. The readout protocol has been described elsewhere by Waldner et al (60,61). For the NaCl pellets placed in the male ATOM phantom, the organ doses were calculated from absorbed dose to NaCl using the energy dependence ratio of NaCl pellets at 10-mm depth in PMMA, and PMMA at the same depth.…”

“…The dosimeters made from NaCl are not commercially available but are part of an ongoing research project (60)(61)(62)(63).…”

“…The TLDs were reset before irradiation by annealing them for 12 min at 2408C followed by rapid cooling in a -108C freezer. A separate set of 10 TLDs was used for calibration with 50 mGy 60 Co at the SCK CEN Secondary Standard Dosimetry Laboratory LNK. The calibration in terms of 60 Co gamma equivalent air kerma was converted to absorbed dose in tissue or bone.…”

“…A separate set of 10 TLDs was used for calibration with 50 mGy 60 Co at the SCK CEN Secondary Standard Dosimetry Laboratory LNK. The calibration in terms of 60 Co gamma equivalent air kerma was converted to absorbed dose in tissue or bone. The air kerma delivered by the 60 Co calibration irradiation was first converted to absorbed dose in LiF by multiplication with the ratio of the mass energy absorption coefficients of LiF over air.…”

“…The calibration in terms of 60 Co gamma equivalent air kerma was converted to absorbed dose in tissue or bone. The air kerma delivered by the 60 Co calibration irradiation was first converted to absorbed dose in LiF by multiplication with the ratio of the mass energy absorption coefficients of LiF over air. Then the photon energy spectra obtained from the Monte Carlo simulations were used to correct for the different photon energy dependence of the energy deposition in LiF, tissue and bone and the photon energy dependence of the TLD luminescence efficiency (64).…”