scholarly journals Potential benefit of retrospective use of neutron monitors in improving ionising radiation exposure assessment on international flights: issues raised by neutron passive dosimeter measurements and EPCARD simulations during sudden changes in solar activity

2020 ◽  
Vol 71 (2) ◽  
pp. 152-157
Author(s):  
Marina Poje Sovilj ◽  
Branko Vuković ◽  
Vanja Radolić ◽  
Igor Miklavčić ◽  
Denis Stanić
Keyword(s):  
Solar Activity ◽  
High Energy ◽  
Ionising Radiation ◽  
Neutron Dose ◽  
Flight Crew ◽  
Dose Equivalent ◽  
Ambient Dose Equivalent ◽  
Neutron Dose Equivalent ◽  
Neutron Component ◽  
Ambient Dose

AbstractSince air transport became more accessible, more and more people have been exposed to ionising radiation of cosmic origin. Measuring the neutron dose equivalent is a good approximation of total ambient dose equivalent, as neutrons carry about 50 % of the dose at flight altitudes. The aim of our study was to compare our measurements of the neutron component of secondary cosmic radiation dose, taken with passive dosimeters, with the data obtained from a simulation generated by EPCARD software, which is common in assessing flight crew exposure to ionising radiation. We observed deviations (both above and below) from the expected proportion of the neutron component (between 40 and 80 %), which pointed to certain issues with actual passive dosimeter measurement and the EPCARD simulation. The main limitation of the dosimeter are large uncertainties in high energy neutron response, which may result in underestimation of neutron dose equivalent. The main drawback of the software simulation is monthly averaging of solar potential in calculations, which can neglect sporadic high energy events. Since airlines worldwide almost exclusively use software (due to costs and convenience) to estimate the dose received by their crew, it is advisable to retrospectively recalculate the dose taking into account neutron monitor readings when solar activity changes.

scholarly journals Influence of solar activity on ambient dose equivalent H*(10) measured with thermoluminescent dosimeters in Slovenia

2021 ◽  
Vol 72 (1) ◽  
pp. 23-28
Author(s):  
Benjamin Zorko ◽  
Matjaž Korun ◽  
Boštjan Črnič ◽  
Branko Vodenik ◽  
Sandi Gobec
Keyword(s):  
Solar Activity ◽  
General Population ◽  
Nuclear Power ◽  
Correlation Coefficients ◽  
Ionising Radiation ◽  
Population Exposure ◽  
Dose Equivalent ◽  
Thermoluminescent Dosimeters ◽  
Ambient Dose Equivalent ◽  
Ambient Dose

Abstract Ambient dose equivalent H*(10) is measured to assess general population exposure to ionising radiation. From its spatial and time variations it is possible to identify sources of exposure. In Slovenia, semi-annual H*(10) is measured routinely with thermoluminescence dosimeters at 66 locations around the Nuclear Power Plant (NPP) Krško and at 50 other locations covering the rest of Slovenian territory. Since the Chernobyl accident contamination had ceased to contribute to ambient dose equivalents, we have been calculating correlation coefficients between annual mean number of sunspots and annual H*(10). These correlation coefficients were calculated for five locations in western Slovenia and for five annual H*(10) extracted from measurements around NPP Krško. Their ranges between –0.64 and –0.38 suggest a clear negative correlation between solar activity and H*(10). Mean annual H*(10) averted by solar activity in the past two solar maxima reached 0.070 mSv around NPP Krško (155 m.a.s.l.) and 0.132 mSv and 0.180 mSv at Kredarica (2515 m.a.s.l.). Quantifying the influence of the solar activity on the ambient dose equivalent helps us to better understand exposure of the general population to ionising radiation.

Neutron dose evaluation of Elekta Linac at two energies (10 & 18 MV) by MCNP code and comparison with experimental measurements

2014 ◽  
Vol 6 (1) ◽  
pp. 1006-1015
Author(s):  
Negin Shagholi ◽  
Hassan Ali ◽  
Mahdi Sadeghi ◽  
Arjang Shahvar ◽  
Hoda Darestani ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Measurement Data ◽  
Calculated Data ◽  
High Energy ◽  
Neutron Dose ◽  
Dose Assessment ◽  
Photon Flux ◽  
Dose Equivalent ◽  
Monte Carlo Techniques ◽  
Neutron Dose Equivalent

Medical linear accelerators, besides the clinically high energy electron and photon beams, produce other secondary particles such as neutrons which escalate the delivered dose. In this study the neutron dose at 10 and 18MV Elekta linac was obtained by using TLD600 and TLD700 as well as Monte Carlo simulation. For neutron dose assessment in 2020 cm2 field, TLDs were calibrated at first. Gamma calibration was performed with 10 and 18 MV linac and neutron calibration was done with 241Am-Be neutron source. For simulation, MCNPX code was used then calculated neutron dose equivalent was compared with measurement data. Neutron dose equivalent at 18 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 3.3, 4, 5 and 6 cm. Neutron dose at depths of less than 3.3cm was zero and maximized at the depth of 4 cm (44.39 mSvGy-1), whereas calculation resulted  in the maximum of 2.32 mSvGy-1 at the same depth. Neutron dose at 10 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 2.5, 3.3, 4 and 5 cm. No photoneutron dose was observed at depths of less than 3.3cm and the maximum was at 4cm equal to 5.44mSvGy-1, however, the calculated data showed the maximum of 0.077mSvGy-1 at the same depth. The comparison between measured photo neutron dose and calculated data along the beam axis in different depths, shows that the measurement data were much more than the calculated data, so it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry in linac central axis due to high photon flux, whereas MCNPX Monte Carlo techniques still remain a valuable tool for photonuclear dose studies.

scholarly journals Neutrons along the labyrinth of high energy medical accelerators: Effect of wall materials

2019 ◽  
Vol 21 ◽  
pp. 169
Author(s):  
M. Fakinou ◽  
I. E. Stamatelatos ◽  
J. Kalef-Ezra
Keyword(s):  
Monte Carlo ◽  
Cost Effective ◽  
High Energy ◽  
Wall Material ◽  
Mcnp Code ◽  
Dose Equivalent ◽  
Concrete Wall ◽  
Ambient Dose Equivalent ◽  
Wall Materials ◽  
Ambient Dose

Neutron streaming along the labyrinth of a generic bunker of an 18MV medical accelerator was evaluated. Monte Carlo simulations using MCNP code were performed to calculate neutron ambient dose equivalent along the labyrinth. The effect of plain, borated and barites concrete wall material, as well as borated concrete and plywood (Celotex), as neutron absorbing wall liners, was examined. The results of the study suggest that plywood can provide a cost effective material to attenuate neutron streaming along the labyrinth.

Superheated drop detector for determination of neutron dose equivalent to patients undergoing high-energy x-ray and electron radiotherapy

1993 ◽  
Vol 20 (3) ◽  
pp. 781-787 ◽  
Author(s):  
Ravinder Nath ◽  
Ali S. Meigooni ◽  
Christopher R. King ◽  
Stuart Smolen ◽  
Francesco d'Errico
Keyword(s):  
High Energy ◽  
Neutron Dose ◽  
Dose Equivalent ◽  
X Ray ◽  
Neutron Dose Equivalent ◽  
Electron Radiotherapy

scholarly journals Development of neutron survey meter using prescila neutron probe

2021 ◽  
Vol 8 (4) ◽  
pp. 26-33
Author(s):  
Hong Luong Thi ◽  
Phong Nguyen Tien ◽  
Bich Pham Thi ◽  
Huyen Nguyen Du
Keyword(s):  
High Energy ◽  
Energy Response ◽  
Dose Equivalent ◽  
Directional Response ◽  
Neutron Probe ◽  
Ambient Dose Equivalent ◽  
The Relationship ◽  
Non Destructive ◽  
Proper Operation ◽  
Ambient Dose

This paper presents the design and validation of a neutron survey meter. The meter consists of a PRESCILA neutron probe (with good sensitivity, directional response, gamma rejection, and enhanced high-energy response to 20 MeV) and an electrometer developed at Non-Destructive Evaluation center. The homogeneity response of the PRESCILA neutron probe was investigated as a function of distances from the 241Am - 9Be source in order to obtain the appropriate distance for accurate count-rate measurements using the neutron survey meter. A system consists of the PRESCILA neutron probe and the Ludlum Model 2326 electrometer was then used for measuring neutron ambient dose equivalent rates in the range from 50 cm to 200 cm with the step of 25 cm. The relationship between the count-rates and neutron dose equivalent rates (in the distance ranged from 50 to 200 cm) were deduced to validate the proper operation of the neutron survey meter.

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