Spectrally average conversion coefficients for air kerma to ambient dose equivalent for clinical linear accelerator

2009 ◽  
Vol 67 (1) ◽  
pp. 174-177 ◽  
Author(s):  
Marco A. Frota ◽  
Verginia R. Crispim ◽  
Ademir X. Silva ◽  
Alphonse Kelecom
Keyword(s):  
Linear Accelerator ◽  
Dose Equivalent ◽  
Air Kerma ◽  
Ambient Dose Equivalent ◽  
Conversion Coefficients ◽  
Ambient Dose

DEVELOPMENT OF A NEW SECONDARY STANDARD FOR H*(10)

2020 ◽  
Vol 188 (3) ◽  
pp. 378-382
Author(s):  
K Bairlein ◽  
B Behnke ◽  
O Hupe
Keyword(s):  
Ionization Chamber ◽  
Secondary Standard ◽  
Dose Equivalent ◽  
Air Kerma ◽  
Radiation Fields ◽  
Ambient Dose Equivalent ◽  
Conversion Coefficients ◽  
Aluminium Coating ◽  
Pulsed Fields ◽  
Ambient Dose

Abstract A secondary standard for ambient dose equivalent, H*(10), is necessary for the dissemination of the unit Sievert (Sv), but there is no such standard commercially available currently. Furthermore, the measurement of H*(10) instead of calculating H*(10) from air kerma and conversion coefficients is needed for unknown radiation fields. We developed a prototype of a new secondary standard for H*(10) based on a spherical 1 l ionization chamber for air kerma. This chamber was modified with copper wires at the inner surface to adjust the response of the chamber according to H*(10). Additionally, a Makrolon shell and an aluminium coating were added to optimize the response at energies below 50 keV. The prototype fulfils the requirements given in ISO 4037-2 in the energy range from 12 keV to 7 MeV. In combination with an electrometer, it can be used as area dosemeter, suitable for pulsed fields and for low energy radiation.

ESTABLISHMENT OF A LOW DOSE RATE GAMMA RAY CALIBRATION FIELD FOR ENVIRONMENTAL RADIATION MONITORING DEVICES

2019 ◽  
Vol 187 (1) ◽  
pp. 61-68
Author(s):  
Munehiko Kowatari ◽  
Hiroshi Yoshitomi ◽  
Sho Nishino ◽  
Yoshihiko Tanimura ◽  
Tetsuya Ohishi ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Radiation Monitoring ◽  
Dose Equivalent ◽  
Environmental Radiation ◽  
Air Kerma ◽  
Ambient Dose Equivalent ◽  
Reference Air Kerma Rate ◽  
Monitoring Devices ◽  
Air Kerma Rate ◽  
Ambient Dose

Abstract For routine calibration of dosemeters used for environmental radiation monitoring, a low dose rate 137Cs gamma ray calibration field that fully satisfies the requirement of the ISO 4037 series was established in the Facility of Radiation Standards in Japan Atomic Energy Agency. Two different methods were employed to determine the reference air kerma rate, namely a conventional ionisation chamber and a G(E) function method used a newly developed scintillation spectrometer. To fulfil the requirement of the ISO 4037 and suppress scattering of Cs gamma ray within the room as far as possible, a suitable lead collimator was introduced to limit the irradiation area at test points and placed at the middle height in an irradiation room with a grating floor. From measured results of de-convoluted photon fluence spectrum and the variation of evaluated reference air kerma rates between 1.0 m and 3.0 m from the centre of the source, gamma ray scattering from the room structures was found to be negligible. The reference air kerma rate at distances between1.0 m and 3.0 m could be then interpolated by simply considering the inverse square law of the distance and air attenuation. The resulting Cs gamma ray calibration field could provide ambient dose equivalent rates of 0.7–7.2 μSv h−1 for use with environmental radiation monitoring devices. Finally, we attempted to calibrate a widely used NaI(Tl) scintillation survey metre, obtaining a quite satisfactory calibration factor. These results also imply that such survey metres can be employed to monitor affected areas and assess the progress of decontamination, as they can provide appropriate measurements of the ambient dose equivalent rate.

scholarly journals Correlation between calculated and measured values of gamma dose rate in air in forests contaminated with 137Cs: the remote period after the Chernobyl accident

2020 ◽  
Vol 12 (4) ◽  
pp. 37-46 ◽  
Author(s):  
Valery P. Ramzaev ◽  
Anatoly N. Barkovsky
Keyword(s):  
Vertical Distribution ◽  
Dose Rate ◽  
Chernobyl Accident ◽  
Gamma Dose ◽  
Dose Equivalent ◽  
Air Kerma ◽  
Equivalent Rate ◽  
Ambient Dose Equivalent ◽  
Air Kerma Rate ◽  
Ambient Dose

In 2015–2016, 13 forest and 7 virgin grassland plots located in the south-western districts of the Bryansk region were surveyed. The aim of the work was to experimentally test the possibility of using a method for calculating the dose rate of gamma radiation in air in radioactively contaminated forests in a remote period after the Chernobyl accident. According to the results of gamma-spectrometric analysis of soil samples obtained at the sites in another study, the values of inventory and vertical distribution of 137Cs in the upper 20 cm layer were established. In this paper, these data were used to calculate the air kerma rate using a method taken from literature. In addition, at the sites of soil sampling, ambient dose equivalent rate in air was measured, and the contribution of 137Cs to the total gamma dose rate was determined with a field gamma spectrometer-dosemeter. The measured values of the ambient dose equivalent rate from 137Cs correlated positively and statistically significantly with the calculated values of the air kerma rate. The Spearman correlation coefficient was 0.989 (P < 0.01) for the location “forest” and 0.893 (P < 0.05) for the location “grassland”. There was no statistically significant difference between the “forest” and “grassland” locations when analyzing the ratio of the measured dose rate values to the calculated dose rate values (the Mann-Whitney U test, P > 0.05). Results of this work show that, when calculating gamma radiation dose rate in air in forests at a remote stage after the Chernobyl accident, it is enough to know the 137Cs inventory in the upper 20 cm soil layer and a detailed picture of vertical distribution of the radionuclide in this layer. The presence of woody biomass can be neglected. This dose rate estimate is conservative. However, a degree of overestimation of the dose rate in air is small, within +10%, which is quite acceptable for determining the external effective dose rate for an individual in the radioactively contaminated forest.

scholarly journals Characteristics of Simulated Workplace Neutron Standard Fields

2020 ◽  
Vol 30 (1) ◽  
pp. 71
Author(s):  
Le Ngoc Thiem ◽  
Nguyen Ngoc Quynh ◽  
Dang Thi My Linh ◽  
Phan Thi Huong
Keyword(s):  
Standard Uncertainty ◽  
International Standard Organization ◽  
Dose Equivalent ◽  
Bonner Sphere ◽  
Ambient Dose Equivalent ◽  
Conversion Coefficients ◽  
Standard Organization ◽  
Spectrometer System ◽  
Ambient Dose

This paper presents the development of simulated workplace neutron standard fields at the Institute for Nuclear Science and Technology with the 241Am-Be source moderated by polyethylene spheres with diameters of 15 cm and 30 cm. The characterization of the standard fields (in terms of neutron fluence rates and neutron ambient dose equivalent rates) was performed using Bonner sphere spectrometer system together with MAXED and FRUIT unfolding codes. The related quantities such as neutron dose equivalent-averaged energies and fluence-to-ambient dose equivalent conversion coefficients were also determined. The discrepancies of values are satisfied the standard uncertainty criteria as recommended by the International Standard Organization 12789 series. It implies that the simulated workplace neutron standard fields can be applied in the practical works for calibration purposes.

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