scholarly journals Neutron spectrometry at low fluence rates for radiation protection at the AMANDE facility

2020 ◽  
Vol 225 ◽  
pp. 05005
Author(s):  
V. Lacoste ◽  
M. Petit ◽  
V. Gressier
Keyword(s):  
Radiation Protection ◽  
Control Room ◽  
Dose Equivalent ◽  
Neutron Spectrometry ◽  
Concrete Wall ◽  
Experimental Hall ◽  
Bonner Sphere ◽  
Ambient Dose Equivalent ◽  
Ambient Dose ◽  
Made In

A neutron spectrometry campaign was carried out in the AMANDE accelerator control room. These measurements had several objectives, one of which was to verify the possibility of determining, with the HERMEIS Bonner sphere system, very low fluence and ambient dose equivalent rates. These measurements were also expected to provide comparison values with calculations, performed with MCNPX 2.6.0, used for modeling the whole facility and to verify the radiological zoning implemented. Neutrons of 3.3 MeV then 15 MeV were produced in the experimental hall of AMANDE and measurements were made in the control room, behind a 40 cm thick concrete wall. The ambient dose equivalent rates derived from the measured spectra are respectively of the order of 0.2 and 10 μSv/h, which are in agreement with a LB6411 surveymeter data also involved.

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.

scholarly journals Occupational exposure to Am-Be neutron calibration source mounted in OB26 shielding container

Nukleonika ◽  
2014 ◽  
Vol 59 (3) ◽  
pp. 97-103 ◽  
Author(s):  
Kamil Szewczak ◽  
Slawomir Jednorog
Keyword(s):  
Occupational Exposure ◽  
Reference Points ◽  
Radiological Protection ◽  
Individual Dose ◽  
Control Room ◽  
Dose Equivalent ◽  
Calibration Source ◽  
Equivalent Rate ◽  
Ambient Dose Equivalent ◽  
Ambient Dose

Abstract Laboratory for Dosimetric and Radon Instruments Calibration which is a part of Central Laboratory for Radiological Protection (CLRP) in Warsaw is equipped with 241Am-Be neutron calibration source with activity of 185 GBq since 1999. The capsule was mounted in the OB26 type shielding container. The control room is separated from the above source by a concrete wall of 0.5 m in thickness. The calibration hall is adjacent to one side of the offi ce room. To comply with the requirements of the radiological protection system, the occupational exposure of persons that are working both in the offi ce and control room needs to be assessed. Two methods were involved for ambient dose equivalent rate determination. The active instrument measurements (AIMs) performed with the Berthold LB6411 neutron probe and the Monte Carlo simulation method (MCS) based on MCNP5 code. These estimations were completed for fi ve reference points. Additionally the γ radiation component was measured by RSS131 ionisation chamber. An increased value of the ambient dose equivalent rate from neutrons was observed in two reference positions. The fi rst observation was done in the control room while the second one in the offi ce room. Expected individual dose equivalents were evaluated based on the results of the AIM and on the expected working time in particular reference points. The annual individual dose equivalent associated with calibration activities using mentioned neutron source was estimated at maximum 0.8 mSv.

NEUTRON SPECTRUM UNFOLDING USING VARIOUS COMPUTER CODES: A COMPARISON

2021 ◽  
pp. 128-133
Author(s):  
Thiệm
Keyword(s):  
Neutron Spectrum ◽  
Neutron Fluence ◽  
Dose Equivalent ◽  
Spectrum Unfolding ◽  
Bonner Sphere ◽  
Ambient Dose Equivalent ◽  
Computer Codes ◽  
Neutron Spectrum Unfolding ◽  
Spectrometer System ◽  
Ambient Dose

Dosimetric quantities at various distances from a 30 cm diameter polyethylene sphere moderated 241Am-Be source were investigated using the Bonner sphere spectrometer system. The different international commercial unfolding codes were applied to unfold the neutron spectrum, and their shapes were compared to each other. Additionally, the integrated neutron fluence rates overall spectrum and fractional neutron fluence rates were deduced and compared between the results obtained from different unfolding codes. As an important quantity applying in radiation safety assessment, the neutron ambient dose equivalent rates were also calculated and compared to each other to verify the utility feasibilities of the codes.

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.

scholarly journals Monte Carlo Simulations of Neutron Ambient Dose Equivalent in a Novel Proton Therapy Facility Design

2020 ◽  
Vol 6 (4) ◽  
pp. 29-37
Author(s):  
Uwe Titt ◽  
Enzo Pera ◽  
Michael T. Gillin
Keyword(s):  
Monte Carlo ◽  
Radiation Protection ◽  
Proton Therapy ◽  
Facility Design ◽  
Dose Equivalent ◽  
Treatment Room ◽  
Dose Limits ◽  
Ambient Dose Equivalent ◽  
Ambient Dose ◽  
Proton Therapy Facility

Abstract Purpose The neutron shielding properties of the concrete structures of a proposed proton therapy facility were evaluated with help of the Monte Carlo technique. The planned facility's design omits the typical maze-structured entrances to the treatment rooms to facilitate more efficient access and, instead, proposes the use of massive concrete/steel doors. Furthermore, straight conduits in the treatment room walls were used in the design of the facility, necessitating a detailed investigation of the neutron radiation outside the rooms to determine if the design can be applied without violating existing radiation protection regulations. This study was performed to investigate whether the operation of a proton therapy unit using such a facility design will be in compliance with radiation protection requirements. Methods A detailed model of the planned proton therapy expansion project of the University of Texas, M. D. Anderson Cancer Center in Houston, Texas, was produced to simulate secondary neutron production from clinical proton beams using the MCNPX Monte Carlo radiation transport code. Neutron spectral fluences were collected at locations of interest and converted to ambient dose equivalents using an in-house code based on fluence to dose-conversion factors provided by the International Commission on Radiological Protection. Results and Conclusions At all investigated locations of interest, the ambient dose equivalent values were below the occupational dose limits and the dose limits for individual members of the public. The impact of straight conduits was negligible because their location and orientation were such that no line of sight to the neutron sources (ie, the isocenter locations) was established. Finally, the treatment room doors were specially designed to provide spatial efficiency and, compared with traditional maze designs, showed that while it would be possible to achieve a lower neutron ambient dose equivalent with a maze, the increased spatial (and financial) requirements may offset this advantage.

scholarly journals Neutron calibration field at Institute for Nuclear Science and Technology

2016 ◽  
Vol 6 (4) ◽  
pp. 1-7
Author(s):  
Ngoc Thiem Le ◽  
Ngoc Quynh Nguyen ◽  
Quang Tuan Ho ◽  
Van Giap Trinh ◽  
Tuan Khai Nguyen ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Science And Technology ◽  
Free Field ◽  
Dose Equivalent ◽  
Nuclear Science ◽  
Bonner Sphere ◽  
Ambient Dose Equivalent ◽  
Bonner Sphere Spectrometer ◽  
Ambient Dose ◽  
Good Agreement

In this study, a neutron calibration field of a 241Am-Be standard source at the Institute for Nuclear Science and Technology is characterized in terms of neutron spectral fluxes and neutron ambient dose equivalent ( ) rates based on ISO 8529 recommended generalized fit method together with measurements using a Bonner Sphere Spectrometer and MAXED unfolding techniques. The total, direct and scattered neutron components as well as rates and neutron spectral fluxes are separated from each other. The direct  rates and neutron spectral fluxes in the free field as functions of distances from the source are also theoretically calculated based on the neutron source strength. The comparison between experimental data and theoretical calculations of the  rates and neutron spectral fluxes shows good agreement within 3%, this has confirmed the reliability of the field characterization process and its applicability in the practical calibration works for neutron survey meters.

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