scholarly journals A Comparison of Conventional Empirical Formula and MCNPX Code in the Estimations of Photon and Neutron Skyshine Rates for an 18MV Radiotherapy Bunker

2021 ◽  
Author(s):  
Reza Eghdam-Zamiri ◽  
Hosein Ghiasi
Keyword(s):  
Physical Phenomenon ◽  
Ground Level ◽  
High Energy ◽  
Empirical Method ◽  
Control Room ◽  
Dose Equivalent ◽  
High Energy Radiation ◽  
Dose Rates ◽  
Mcnpx Code ◽  
Secondary Neutrons

Purpose: A physical phenomenon, scattering the radiation by the atmosphere above the room to the points at ground level around the linac treatment room is known as skyshine radiation. This study aimed to estimate photon and neutron skyshine from a linac in a high-energy radiation therapy facility. Materials and Methods: The empirical method of NCRP report 151 and MC simulations were employed to estimate skyshine radiation dose from the 18MV linac photon beam. A linac and its bunker were modeled and skyshine dose equivalent from photons and secondary neutrons were derived and compared in the control room, corridor, sidewalk and, parking. Results: The photon skyshine dose rates calculations by the MC method varied from 0.43 µSv/h at the sidewalk to 6.2 µSv/h at the control room. The ratios of NCRP to MCNP calculations varied from 3.58 for the corridor to 16.14 for the control room. For the neutron skyshine dose rate at distances shorter than 20m, it was found to be 10.4 nSv/h and the ratios of the NCRP to MCNP were 1.26 at the control room and 3.34 at the sidewalk. Conclusion: It was concluded that the empirical method overestimates photon and neutron skyshine dose rates in comparison to the MCNPX code. The refinement of the proposed empirical method of NCRP 151 and application of MC methods are strongly suggested for more reliable calculations of skyshine radiations.

scholarly journals Nowcast and forecast of galactic cosmic ray (GCR) and solar energetic particle (SEP) fluxes in magnetosphere and ionosphere – Extension of WASAVIES to Earth orbit

2019 ◽  
Vol 9 ◽  
pp. A9 ◽  
Author(s):  
Tatsuhiko Sato ◽  
Ryuho Kataoka ◽  
Daikou Shiota ◽  
Yûki Kubo ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Energetic Particle ◽  
Solar Energetic Particle ◽  
Cosmic Ray ◽  
Ground Level ◽  
High Energy ◽  
Extended Version ◽  
High Energy Proton ◽  
Dose Rates ◽  
Energy Proton ◽  
Galactic Cosmic Ray

Real-time estimation of cosmic-ray fluxes on satellite orbits is one of the greatest challenges in space weather research. Therefore, we develop a system for nowcasting and forecasting the galactic cosmic ray (GCR) and solar energetic particle (SEP) fluxes at any location in the magnetosphere and ionosphere during ground-level enhancement (GLE) events. It is an extended version of the WArning System for AVIation Exposure to SEP (WASAVIES), which can determine event profiles by using real-time data of the count rates of several neutron monitors (NMs) at the ground level and high-energy proton fluxes observed by Geostationary Operational Environmental Satellites (GOES) satellites. The extended version, called WASAVIES-EO, can calculate the GCR and SEP fluxes outside a satellite based on its two-line element (TLE) data. Moreover, organ absorbed-dose and dose-equivalent rates of astronauts in the International Space Station (ISS) can be estimated using the system, considering its shielding effect. The accuracy of WASAVIES-EO was validated based on the dose rates measured in ISS, as well as based on high-energy proton fluxes observed by POES satellites during large GLEs that have occurred in the 21st century. Agreement between the nowcast and forecast dose rates in ISS, especially in terms of their temporal structures, indicates the usefulness of the developed system for future mission operations.

Radiation-Induced Crosslinking of Chlorobutyl and Polydiene Elastomers. Promotion by Polythiols

1975 ◽  
Vol 48 (5) ◽  
pp. 860-877 ◽  
Author(s):  
R. L. Zapp ◽  
A. A. Oswald
Keyword(s):  
Chain Scission ◽  
High Energy ◽  
Cross Linking ◽  
Crosslinking Reaction ◽  
High Energy Radiation ◽  
Dose Rates ◽  
Radiation Cure ◽  
60Co Source ◽  
Wide Range ◽  
Radiation Induced

Abstract The response of Chlorobutyl (CIIR), an elastomer with 1,1-disubstituted carbon atoms along the polymer chain, to ionizing radiation has been directed toward a predominantly crosslinking reaction by addition of 1–4 phr of thioetherpolythiols (TEPT) prepared by reaction of trivinylcyclohexane or cyclododecatriene with H2S or low-molecular-weight dithiols. From a fundamental viewpoint, the unique feature of the CIIR-TEPT system is the reversal of expected behavior for a polymer molecule containing 1,1-disubstituted carbon atoms when exposed to high energy radiation: instead of chain scission, cross-linking is the predominant physical change to an extent comparable to that obtained from thermal curing processes. The TEPT becomes part of the radiation-cured network, for, as the radiation dose is increased, there is progressive addition of thiol sulfur to the crosslinked network. Concomitantly, there is a progressive reduction in the chlorine content as radiation-induced vulcanization proceeds. These polythiols are also powerful accelerators of radiation-induced cross-linking of polydiene elastomers, especially those with appreciable amounts of pendent vinyl unsaturation, such as conventional SBR. Evidence exists that a blend of CIIR and SBR can be covulcanized by radiation-induced curing in the presence of TEPT. Experiments were conducted with gamma radiation from a 60Co source and with a 1.4 MeV electron beam at dose rates of 20–120 kJ/kg (2–12 megarads). Physical properties of fully compounded polythiol-promoted CIIR systems crosslinked by radiation are lower than comparable thermally cured compounds, but the strengths would be adequate for many applications. Compounding ingredients, especially common accelerators of sulfur vulcanization, provide a wide range of inhibitory action toward radiation precure. However, with selected types, especially organometallic derivatives which are less soluble in the compound, radiation cure can proceed with a minimum of inhibition.

Dose equivalent measurements in a strongly pulsed high-energy radiation field

2004 ◽  
Vol 110 (1-4) ◽  
pp. 759-762 ◽  
Author(s):  
S. Mayer ◽  
N. Golnik ◽  
J. E. Kyllonen ◽  
H. G. Menzel ◽  
Th. Otto
Keyword(s):  
Radiation Field ◽  
High Energy ◽  
Dose Equivalent ◽  
High Energy Radiation ◽  
Energy Radiation

scholarly journals The neutron dose equivalent around high energy medical electron linear accelerators

2014 ◽  
Vol 29 (3) ◽  
pp. 207-212 ◽  
Author(s):  
Marina Poje ◽  
Ana Ivkovic ◽  
Slaven Jurkovic ◽  
Gordana Zauhar ◽  
Branko Vukovic ◽  
...  
Keyword(s):  
Neutron Radiation ◽  
Medical Personnel ◽  
Dose Dependence ◽  
High Energy ◽  
Neutron Dose ◽  
Dose Equivalent ◽  
Linear Accelerators ◽  
Dose Rates ◽  
Neutron Dose Equivalent ◽  
Conservative Estimation

The measurement of neutron dose equivalent was made in four dual energy linear accelerator rooms. Two of the rooms were reconstructed after decommissioning of 60Co units, so the main limitation was the space. The measurements were performed by a nuclear track etched detectors LR-115 associated with the converter (radiator) that consist of 10B and with the active neutron detector Thermo BIOREM FHT 742. The detectors were set at several locations to evaluate the neutron ambient dose equivalent and/or neutron dose rate to which medical personnel could be exposed. Also, the neutron dose dependence on collimator aperture was analyzed. The obtained neutron dose rates outside the accelerator rooms were several times smaller than the neutron dose rates inside the accelerator rooms. Nevertheless, the measured neutron dose equivalent was not negligible from the aspect of the personal dosimetry with almost 2 mSv a year per person in the areas occupied by staff (conservative estimation). In rooms with 15 MV accelerators, the neutron exposure to the personnel was significantly lower than in the rooms having 18 MV accelerators installed. It was even more pronounced in the room reconstructed after the 60Co decommissioning. This study confirms that shielding from the neutron radiation should be considered when building vaults for high energy linear accelerators, especially when the space constraints exist.

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.

Modeling the Effects of O-sulfonation on the CID of Serine

2020 ◽  
Author(s):  
Kenneth Lucas ◽  
George Barnes
Keyword(s):  
Sulfo Group ◽  
High Energy ◽  
Empirical Method ◽  
Side Chain ◽  
Energy Structure ◽  
Direct Dynamics ◽  
Theoretical Mass ◽  
Intermolecular Proton Transfer ◽  
Dynamics Simulations ◽  
Semi Empirical

We present the results of direct dynamics simulations and DFT calculations aimed at elucidating the effect of \textit{O}-sulfonation on the collision induced dissociation for serine. Towards this end, direct dynamics simulations of both serine and sulfoserine were performed at multiple collision energies and theoretical mass spectra obtained. Comparisons to experimental results are favorable for both systems. Peaks related to the sulfo group are identified and the reaction dynamics explored. In particular, three significant peaks (m\z 106, 88, and 81) seen in the theoretical mass spectrum directly related to the sulfo group are analyzed as well as major peaks shared by both systems. Our analysis shows that the m\z 106 peaks result from intramolecular rearrangements, intermolecular proton transfer among complexes composed of initial fragmentation products, and at high energy side-chain fragmentation. The \mz 88 peak was found to contain multiple constitutional isomers, including a previously unconsidered, low energy structure. It was also seen that the RM1 semi empirical method was not able to obtain all of the major peaks seen in experiment for sulfoserine. In contrast, PM6 did obtain all major experimental peaks.

Photo-degradation of monoazo dye blue 13 using advanced oxidation process

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Aqueous Solution ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
High Energy ◽  
Uv Exposure ◽  
H2o2 Concentration ◽  
Oxidizing Agent ◽  
Photo Degradation ◽  
High Energy Radiation ◽  
Uv Lamp

The high energy radiation overcome the bonding of solute in a solution and H2O2 acts as an oxidizing agent and generates a free radical in the solution which results in photo-degradation by converting the solute in to simple form and resultantly, colored substance under the effect of photo-degradation becomes colorless. The photo-degradation of monoazo dye Blue 13 in an aqueous solution was investigated using a laboratory scale UV lamp in the presence of H2O2 and for maximum degradation of dye, the independent parameter UV power, UV exposure time, pH and H2O2 concentration were optimized. It was found that neither UV in the presence of H2O2 is able to degrade Blue 13 under optimum condition. The results revealed that the use of both UV and H2O2 have pronounced effect on the discoloration of dyes which could be used for management of textile effluents contain waste dyes.

scholarly journals Challenges and Opportunities for CsPbBr3 Perovskites in Low- and High-Energy Radiation Detection

2021 ◽  
pp. 1290-1314
Author(s):  
Lotte Clinckemalie ◽  
Donato Valli ◽  
Maarten B. J. Roeffaers ◽  
Johan Hofkens ◽  
Bapi Pradhan ◽  
...  
Keyword(s):  
Radiation Detection ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Challenges And Opportunities
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