Irradiation Room Research Articles

Preliminary test of a newly developed pilot-scale movable microwave drying equipment for the treatment of solid organic waste

This study introduces a developed, movable, and pilot-scale microwave drying equipment with an automatic control system for the treatment of solid organic waste. Based on a previous study, the structure of the reactor and the arrangement of the magnetron were improved to make the material absorb microwave energy more uniformly and efficiently. The equipment added the auxiliary hot plate and air extraction system, which effectively solved the influence of the occurrence condensate water in the microwave irradiation room on the drying efficiency and energy consumption. The microwave drying behavior of the existing constant-power mode was compared with the improved constant-temperature mode. The experimental results showed that the latter mode could effectively solve the partial overheating of the material caused by uneven heating. The constant-temperature mode was more advantageous in product quality, safety, and selectivity. The advantages and disadvantages of the equipment were analyzed by comparing it with the other existing pilot-scale microwave drying equipment. The proposed system showed good performance. Thus, the newly developed mobile microwave drying system has great potential for practical application.

Validation of an indium-based multi-shell neutron spectrometer

A multi-shell neutron spectrometer with indium foil detector (In-MuNS) was developed to evaluate intense neutron fields that are generated in medical accelerators. The response matrix of this new spectrometer was calculated from 1 meV to 100 MeV using MCNP5 v.1.6 with ENDF/B-VIII.0 nuclear data. An experiment with a252Cf source with known emission rate was performed to validate the computational model of the spectrometer. This included detailed modelling of the irradiation room to evaluate the room-scattered field. The contribution of scattered neutrons to the induced activity in the foil reached 30% for the smallest sphere configuration (diameter 5.0 cm). The quotient between the experimental and simulated foil activity remained satisfactorily constant (1.03±0.04) as the sphere diameter varied, demonstrating the validity of the simulation model. In-MuNS proved to be a portable and compact alternative to conventional Bonner spheres.

Simulation of Ozone Concentrations Inside Co60 Industrial Irradiator

Ozone concentration inside industrial irradiators is considered one of the important safety aspects due to its harm effects upon human and its corrosive effects upon metal parts inside irradiation room. Using ozone monogram, phases of ozone concentrations were determined between ozone concentration, air change rate inside irradiation room, volume of radiation room and source activity. The time for motor malfunction was estimated and also using MATLAB software to calculate these parameters.

Radiation protection study for a reloading operation of cobalt 60 sources in the Moroccan ionisation station using the GEANT4 Monte-Carlo simulation code

The operation of reloading the irradiators is considered among the tasks requiring high radiation protection monitoring, to protect the intervening manipulators, the public and the environment. Morocco is among the countries that have a cobalt irradiator, installed at the National Institute of Agricultural Research (NIAR) of Tangier, to carry out research in the field of agronomy. In the beginning, the irradiator used low doses of activity for the study of products only, for treatment of high doses. The NIAR carried out a reload to increase the activity. To perform this, a temporary pool was installed inside the irradiation room to handle the sources safely. A radiation protection study is necessary to ensure the safe operation. This operation requires a height level of exposure. To ovoid the exposer risk, it is proposed to use the Monte Carlo method thanks to its reliability in the dosimetric calculation. This article presents a radiation protection study of the Moroccan irradiator reloading operation using the GEANT4 Monte-Carlo Simulation Code.

Atomic-scale mechanisms of He/V ratio effect on helium bubble hardening in iron for neutron irradiated F/M steels

The helium-to-vacancy (He/V) ratio is a key factor related to the helium bubble hardening mechanisms induced by neutron irradiation in ferritic/martensitic (F/M) steels as advanced nuclear structural materials. According to the helium bubble hardening results in F/M steel irradiated in the spallation neutron source, the interactions between a 1/2<111>{110} edge dislocation and helium bubbles with various sizes of 0.7–3.0 nm in bcc-Fe under irradiation temperatures and room temperature was investigated by using molecular dynamics simulation. The effect of various He/V ratios in the ranges of zero to the highest He/V ratios, 1.85–4.0 of stable helium bubbles with no dislocation loop emission, on the interaction mechanisms was analyzed. The results indicated that the critical resolved shear stress (CRSS) drops rapidly to a very low stress level, and immediately bottoms out and rebounds to a very high stress level, when the He/V ratio increases from 1.0 to the highest He/V ratio. The significant change of CRSS values is not only related to the climbing degree of dislocation after releasing, but also related to the moment when the climb appears. A new repulsion mechanism of interaction between dislocation and bubble was proposed to elucidate the abnormal phenomena of the bottoming rebound of CRSS with a great climbing degree, according to the repelling interaction between helium bubble and superjog of dislocation with both strong compressive stress field.

Discussion on Fire Risk Assessment for Irradiation Room

In order to study fire hazards, the reason that we chose 60Co round irradiation room of stacking is just because it is very typical. Ignition temperatures of several radiation cargo can be sequentially gotten by experiment. Both numerical simulation and experiment were adopted to research the rule of change in smoke temperature under source blockage. The fire scenario was simulated to discuss temperature field by FDS. The results I have seen show that temperatures of fire smoke in round irradiation room rose rapidly at 0.5h in the early stage of source blockage. Temperature field in irradiation room gradually comes to stability as time goes on, and the temperature is rising very slowly. The temperature will reach the ignition temperature of radiation cargo, 3.56 days after source blockage. Some radiation cargo may be ignited and cause a fire.

Design of a BNCT irradiation room based on proton accelerator and beryllium target

Preliminary studies for the design of an accelerator-based BNCT clinical facility are presented. The Beam Shaping Assembly neutron activation was evaluated experimentally and with Monte Carlo simulations. The activations of patient, air and walls in the room, the absorbed doses by the patient and the in-air dose distributions were evaluated. Based on these calculations, different walls compositions were tested to optimize the environmental conditions. Borated concrete, advantageously reducing the thermal flux in the room, was proven the best choice.

Monte Carlo validation of dose mapping for the Tunisian Gamma Irradiation Facility using the MCNP6 code

In this paper, we develop a three-dimensional configuration of the Tunisian Gamma Irradiation Facility (TGIF) to determine the spatial distribution of gamma absorbed dose rates in the irradiation area at the 60Co source rack. The results are obtained by using the MCNP6 code. Experimental measurements of the gamma absorbed dose rate are performed in order to be compared with the calculated results. Two dosimetry systems are employed to perform measurements: red and amber perpex and cellulose triacetate (CTA). The results of MCNP6 simulations are compared to the absorbed dose measurements for the following experiments: (1) estimation of the 60Co source rack position, (2) isotropy verification of gamma-ray emission, (3) isodose curves of the absorbed dose rate inside the irradiation room, (4) absorbed dose rate distribution in air on four vertical planes, (5) absorbed dose rate distribution in air on four horizontal planes versus increasing distance from the source axis. The root mean square error (RMSE) is employed to check the discrepancy between MCNP6 simulation and dose measurements. The values of RMSE for all experiments vary from 0.5 to 2.6%, showing good agreements between the measured and calculated results. This agreement reveals that the developed model of the TGIF is accurate. It inspires the possibility to use the model on an irradiation processing and a reload of the facility.

Development of an effective dose calculation method for the downstairs room of a linac facility

ABSTRACT An effective dose calculation method is important in the design of efficient shields in radiation facilities. Some analytical methods have been shown to provide a simple and quick design analysis; however, no suitable method exists that can be applied to a room located directly under an X-ray irradiation room. We propose a new analytical method that uses the multiple reflection ratio predetermined by a Monte Carlo simulation and the differential dose albedo given by the Chilton–Huddleston semi-empirical equation. Our method is verified by comparison with the Monte Carlo simulation, performed for the case of an electron linac facility with an accelerated energy of 10 MeV, where the shielding floor has a thickness of 1.6–2.0 m and the downstairs room has a height of 0.5–1.5 m. The difference between the effective X-ray doses in the downstairs room calculated via the proposed analytical method and the Monte Carlo simulation is less than 25% when the horizontal distance from the X-ray beam to the evaluation point exceeds 3 m and the evaluation point is set at half of the height of the room. The new analytical method can be efficiently and accurately applied to the calculation of the effective dose.

Microdosimetric characterization of clinical carbon-ion beams using synthetic diamond detectors and spectral conversion methods.

To investigate for the first time the potentialities of obtaining microdosimetric measurements in scanned clinical carbon-ion beams using synthetic single crystal diamond detector and to verify the spectral conversion methods. Microdosimetric measurements were performed at different depths in a water phantom at the therapeutic scanned carbon-ion beam of the National Center of Oncological Hadrontherapy (CNAO) in Pavia, using waterproof encapsulated diamond microdosimeter developed at "Tor Vergata" University. A monoenergetic carbon-ion beam of 195MeV/μ scanned over a square field of 2×2cm2 was used. Experimental microdosimetric spectra were compared with those obtained with a propane-filled Tissue Equivalent Proportional Counters (TEPCs) microdosimeter in the same facility at the same conditions. To this purpose, the spectra in diamond were converted to the spectra that would have been collected with a propane-filled cylindrical sensitive volume by means of a novel analytic methodology, recently developed at MedAustron. The microdosimetric spectra acquired by the diamond microdosimeter show different shapes in the 10keVµm-1 ÷103 keVµm-1 lineal-energy range at different water depths. In spite of the high counting rate, no spectral distortion, due to pile-up events and polarization effects, were observed. The experimental spectra have a low detection threshold of about 6keVµm-1 due to the electronic noise in the irradiation room. The comparison between the spectra converted to propane from diamond detector and the spectra collected directly with propane-filled TEPC shows a good agreement in the whole lineal-energy range. Furthermore this comparison confirms that diamond detector response is LET independent. The frequency- and dose-mean lineal energy values were also assessed for all spectra. The frequency-mean values obtained with diamond microdosimeter at different depths scales rather well with the absorbed dose values. Microdosimetric characterization of a synthetic single crystal diamond detector in high-energy scanned carbon-ion beams was performed. The results of the present study showed that this detector is suitable for microdosimetry of clinical carbon ion beams. In addition, the good agreement between the converted diamond spectra and those obtained with TEPC provides the first experimental validation of the spectra conversion methodologies as valuable tools for the comparison of spectra collected with different detectors.

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

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.

Impact of ion source stability for a medical accelerator

MedAustron is a synchrotron-based hadron therapy center located in Lower Austria. Accelerated proton beams with energies of 62–252 MeV/u are used to treat patients since 2016. The carbon ion beam is currently under commissioning and will provide treatment in 2019 with energies of 120–400MeV/u. Two of the four irradiation rooms are used for clinical treatment while the preparation of the Gantry beam line is ongoing. Proton beams of up to 800 MeV will be provided for non-clinical research. The Injector features three identical ECRIS from Pantechnik, two of which are used to generate the proton and the carbon beam respectively. The medical environment of the accelerator puts strict requirements on the ion source long-term stability operation. The extracted beam current from the source allow for maximum current fluctuations on the order of ±2.5% on continuous run. In this work we discuss the impact of the ion source performances on the characteristics and stability of the entire accelerator. Further, we discuss the latest progress on carbon commissioning and the future perspectives with particular emphasis on the source requirements.

Neutron spectra from Neutron Standards Laboratory (LPN/CIEMAT) sources with two Bonner sphere spectrometers

The Neutron Standards Laboratory (LPN: Laboratorio de Patrones Neutrónicos) of the Ionizing Radiation Metrology Laboratory (LMRI) of the CIEMAT (Centro de Investigaciones Energéticas Medioambientales y Tecnológicas) has two calibration neutron sources, 241Am-Be and 252Cf. Studies to verify the shielding of the facility and to characterize the neutron field in the irradiation room have been carried out using Monte Carlo methods. However, spectral measurements were not performed yet. In this study, we measured the total and direct neutron spectra of both calibration neutron sources. Two different Bonner Sphere Spectrometers (BSS) systems were allocated to 115 cm from the sources, on the calibration bench, with and without the shadow cones (SC). From the count rates obtained with both BSS systems (BSS-6LiI and BSS-3He), the total neutron spectrum and direct neutron spectrum were unfolded. Total and direct spectra obtained for the 241Am-Be and 252Cf sources with the MCNPX and different BSS systems, unfold codes and response matrices presented similar shape and are consistent with each other.

CHARACTERIZATION OF THE EPITHERMAL NEUTRON FIELD PRODUCED BY p+7Li REACTION IN A TANDEM ACCELERATOR USING A BONNER SPHERE SPECTROMETER.

The proton beam produced in the Nuclear Physics line of the tandem accelerator of the Centro Nacional de Aceleradores was used to generate a neutron field. In particular, 1.912 MeV protons were used to produce well-known epithermal neutrons through the p+7Li → n+7Be reaction. The aim of the work was to characterize this field while testing the performance of a Bonner sphere spectrometer in the epithermal range. Measurements were performed in four locations at different angle (0°, 30°, 60° and 90°) from beam incidence direction in order to study the angular dependence of the field. Both a parametric and numerical unfolding methods were tested to process the counts of the central detectors and obtain the energy distribution of the neutron fluence. In addition, a Monte Carlo simulation was carried out to complete the study and provide a guess spectrum for numerical unfolding. It was found that the fluence rate and mean energy decrease as the angle from beam direction increases. Total fluence was 2.75, 1.36, 0.366 and 0.216 cm-2 per charge collected in the target at 0°, 30°, 60° and 90°, respectively. Mean energy of the field ranges from 46 to 17 keV at 0° and 60°, respectively. In all cases, given that the irradiation room is so large, the contribution of thermal neutrons to the field is small. Regarding the unfolding, the total fluences estimated by all methods were in agreement within the uncertainties.

Computational model of gamma irradiation room at ININ.

In this paper, we present a model of the gamma irradiation room at the National Institute of Nuclear Research (ININ is its acronym in Spanish) in Mexico to improve the use of physics in dosimetry for human protection. We deal with air-filled ionization chambers and scientific computing made in house and framed in both the GEANT4 scheme and our analytical approach to characterize the irradiation room. This room is the only secondary dosimetry facility in Mexico. Our aim is to optimize its experimental designs, facilities, and industrial applications of physical radiation. The computational results provided by our model are supported by all the known experimental data regarding the performance of the ININ gamma irradiation room and allow us to predict the values of the main variables related to this fully enclosed space to within an acceptable margin of error.

NEUTRON FIELD CHARACTERISTICS AT RADIATION METROLOGY LABORATORY OF STUK.

Radiation metrology laboratory at Radiation and Nuclear Safety Authority (STUK) is Finnish national laboratory for ionizing radiation. In order to establish personal dose equivalent available for neutron calibration service, a project was started to evaluate the neutron reference fields in the present facility. The irradiation room conditions were characterized in order to establish reference conditions for personal dose equivalent. To verify the validity of the calculations, ambient dose equivalent rates and room return were measured and calculated for 241AmBe and 252Cf sources. First results of Monte Carlo calculations and measurements are presented in this article.

An Analysis of Radiation Penetration through the U-Shaped Cast Concrete Joints of Concrete Shielding in the Multipurpose Gamma Irradiator of BATAN

An analysis of radiation penetration through the U-shaped joints of cast concrete shielding in BATAN’s multipurpose gamma irradiator has been carried out. The analysis has been performed by calculating the radiation penetration through the U-shaped joints of the concrete shielding using MCNP computer code. The U-shaped joints were a new design in massive concrete construction in Indonesia and, in its actual application, it is joined by a bonding agent. In the MCNP simulation model, eight detectors were located close to the observed irradiation room walls of the concrete shielding. The simulation results indicated that the radiation levels outside the concrete shielding was less than the permissible limit of 2.5 μSv/h so that the workers could safely access electrical room, control room, water treatment facility and outside irradiation room. The radiation penetration decreased as the density of material increased.

INTERNATIONAL COMPARISON EXERCISE ON NEUTRON SPECTRA UNFOLDING IN BONNER SPHERES SPECTROMETRY: PROBLEM DESCRIPTION AND PRELIMINARY ANALYSIS.

This article describes the purpose, the proposed problems and the reference solutions of an international comparison on neutron spectra unfolding in Bonner spheres spectrometry, organised within the activities of EURADOS working group 6: computational dosimetry. The exercise considered four realistic situations: a medical accelerator, a workplace field, an irradiation room and a skyshine scenario. Although a detailed analysis of the submitted solutions is under preparation, the preliminary discussion of some physical aspects of the problem, e.g. the changes in the unfolding results due to the perturbation of the neutron field by the Bonner spheres, is presented.

Treatment planning system and patient positioning for boron neutron capture therapy

To perform boron neutron capture therapy (BNCT), a type of radiotherapy, a neutron source as a treatment device and peripheral devices such as a treatment planning system (TPS), patient setting device, and neutron monitor are needed. In particular, a TPS is indispensable software in radiotherapy and enables the simulation of a treatment with neutron beam irradiation with a patient’s three-dimensional model based on the patient’s medical images. In addition, the system supports the determination of suitable irradiation conditions for each patient. The patient setting device works to realize the irradiation conditions determined during treatment planning in the actual irradiation room just before irradiation.

White Blood Cell Count and C-Reactive Protein Variations After Posterior Surgery With Intraoperative Radiotherapy for Spinal Metastasis.

Retrospective case series. To evaluate the feasibility of blood test parameters [white blood cell (WBC) count and C-reactive protein (CRP)] for predicting and diagnosing postoperative infection after posterior surgery with intraoperative radiotherapy (IORT) for spinal metastasis. Posterior surgery with IORT is effective for treating spinal metastasis, as we previously reported. However, the procedure requires that the patient be transferred from the operating room to the irradiation room. In addition, the patient's general status is often poor, and the risk of postoperative infection is high. A total of 279 patients who underwent IORT for the treatment of spinal metastasis between August 2004 and June 2013 were included in this study. The WBC count (/10 μL) and CRP level (mg/dL) were recorded in all patients preoperatively and on alternative days for up to 7 days after surgery. We assessed the development of surgical-site infection (SSI) for up to 1 month after surgery. SSI occurred in 41 patients (14.7%). The preoperative WBC count and CRP level did not differ between the infected and noninfected patients. The WBC counts on postoperative day (POD) 1 and POD 7 and the CRP levels on POD 7 were significantly higher in the infected patients (8.8 vs. 10.0, P=0.04; 6.1 vs. 8.8, P=0.002; 3.89 vs. 9.50, P<0.001). A receiver-operating characteristic curve analysis of the WBC count and CRP level for detecting SSI showed cutoff values of 9.6 (WBC count, POD 1), 6.5 (WBC count, POD 7), and 5.0 (CRP level, POD 7). A high WBC count and CRP level on POD 7 may be used to predict or detect SSI. In particular, a CRP level of 5.0 mg/dL on POD 7 strongly suggests the future development of SSI (sensitivity: 78%, specificity: 74%).