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Calibration and testing of a portable NaI(Tl) gamma-ray spectrometer-dosimeter for evaluation of terrestrial radionuclides and 137Cs contributions to ambient dose equivalent rate outdoors

Ramzaev, Valery; Barkovsky, Anatoliy; Bernhardsson, Christian LU and Mattsson, Sören LU (2017) In Radiatsionnaya Gygiena 10(1). p.18-29
Abstract
A commercially available NaI(Tl) based spectrometer-dosimeter has been used to separate contributions of the terrestrial radionuclides (238U series, 232Th series and 40K) and 137Cs to the total ambient dose equivalent rate (ADER), Ḣ*(10) , outdoors. The device had been initially calibrated by the manufacturer to measure: 1) the total ADER; 2) activity concentrations of 226Ra, 232Th, 40K and ‘effective’ activity concentration of the terrestrial radionuclides, ACeff, in soil, agricultural raw materials, forestry products and construction materials; and 3) ground contamination density by 137Cs. In order to derive a... (More)
A commercially available NaI(Tl) based spectrometer-dosimeter has been used to separate contributions of the terrestrial radionuclides (238U series, 232Th series and 40K) and 137Cs to the total ambient dose equivalent rate (ADER), Ḣ*(10) , outdoors. The device had been initially calibrated by the manufacturer to measure: 1) the total ADER; 2) activity concentrations of 226Ra, 232Th, 40K and ‘effective’ activity concentration of the terrestrial radionuclides, ACeff, in soil, agricultural raw materials, forestry products and construction materials; and 3) ground contamination density by 137Cs. In order to derive a conversion
coefficient from ACeff to the ADER stipulated by the terrestrial radionuclides (ADERTRN), two series of additional calibration measurements were performed. The calibration measurements were conducted at 27 outdoor locations in the center of St.-Petersburg and in the Leningradskaya region (background areas). The conversion coefficient from ACeff to ADERTRN of 0.51 (nSv h–1)/(Bq kg–1) has been obtained using a regression analysis of experimental data. The intrinsic noise of the spectrometer and its response to cosmic radiation at sea level has been estimated to 7 nSv h–1. The calibration factors must be used with
caution and only for detectors similar to the one employed in this study (assembly based on a NaI(Tl) single crystal, 63 mm in diameter and 63 mm in length). The spectrometer-dosimeter and experimentally derived calibration coefficients have been tested in field at seven sites in the south-western districts of the Bryansk region that had been heavily contaminated by Chernobyl fallout. The contribution of 137Cs to the total ADER varies between 40% and 95%. The preliminary results of the measurements confirm
the potential of in situ gamma-ray spectrometry for assaying natural and artificial components of the ambient dose equivalent rate outdoors. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
gamma-ray, spectrometer, NaI(Tl), dosimeter, ambient dose equivalent rate, terrestrial radionuclides, K-40, Ra-226, Th-232, Cs-137
in
Radiatsionnaya Gygiena
volume
10
issue
1
pages
18 - 29
ISSN
1998-426X
DOI
10.21514/1998-426X-2017-10-1-18-29
language
English
LU publication?
yes
id
392d7103-f37c-4a1f-87af-32105a0c4d8c
date added to LUP
2018-01-04 11:34:45
date last changed
2018-01-08 11:37:39
@article{392d7103-f37c-4a1f-87af-32105a0c4d8c,
  abstract     = {A commercially available NaI(Tl) based spectrometer-dosimeter has been used to separate contributions of the terrestrial radionuclides (<sup>238</sup>U series, <sup>232</sup>Th series and <sup>40</sup>K) and <sup>137</sup>Cs to the total ambient dose equivalent rate (ADER), Ḣ<sup>*</sup>(10) , outdoors. The device had been initially calibrated by the manufacturer to measure: 1) the total ADER; 2) activity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K and ‘effective’ activity concentration of the terrestrial radionuclides, A<sub>Ceff</sub>, in soil, agricultural raw materials, forestry products and construction materials; and 3) ground contamination density by <sup>137</sup>Cs. In order to derive a conversion<br/>coefficient from AC<sub>eff</sub> to the ADER stipulated by the terrestrial radionuclides (ADER<sub>TRN</sub>), two series of additional calibration measurements were performed. The calibration measurements were conducted at 27 outdoor locations in the center of St.-Petersburg and in the Leningradskaya region (background areas). The conversion coefficient from AC<sub>eff</sub> to ADER<sub>TRN</sub> of 0.51 (nSv h<sup>–1</sup>)/(Bq kg<sup>–1</sup>) has been obtained using a regression analysis of experimental data. The intrinsic noise of the spectrometer and its response to cosmic radiation at sea level has been estimated to 7 nSv h<sup>–1</sup>. The calibration factors must be used with<br/>caution and only for detectors similar to the one employed in this study (assembly based on a NaI(Tl) single crystal, 63 mm in diameter and 63 mm in length). The spectrometer-dosimeter and experimentally derived calibration coefficients have been tested in field at seven sites in the south-western districts of the Bryansk region that had been heavily contaminated by Chernobyl fallout. The contribution of <sup>137</sup>Cs to the total ADER varies between 40% and 95%. The preliminary results of the measurements confirm<br/>the potential of in situ gamma-ray spectrometry for assaying natural and artificial components of the ambient dose equivalent rate outdoors.},
  author       = {Ramzaev, Valery and Barkovsky, Anatoliy and Bernhardsson, Christian and Mattsson, Sören},
  issn         = {1998-426X},
  keyword      = {gamma-ray,spectrometer,NaI(Tl),dosimeter,ambient dose equivalent rate,terrestrial radionuclides,K-40,Ra-226,Th-232,Cs-137},
  language     = {eng},
  number       = {1},
  pages        = {18--29},
  series       = {Radiatsionnaya Gygiena},
  title        = {Calibration and testing of a portable NaI(Tl) gamma-ray spectrometer-dosimeter for evaluation of terrestrial radionuclides and <sup>137</sup>Cs contributions to ambient dose equivalent rate outdoors},
  url          = {http://dx.doi.org/10.21514/1998-426X-2017-10-1-18-29},
  volume       = {10},
  year         = {2017},
}