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A reliable and well-characterized dosimetry system which is traceable to the international measurement system, is the key element to quality assurance in radiation processing with cobalt-60 gamma rays, X-rays, and electron beam. This is specifically the case for health-regulated processes, such as the radiation sterilization of single use medical devices and food irradiation for preservation and disinfestation. Polyethylene is considered to possess a lot of interesting dosimetric characteristics. In this work, a detailed study has been performed to determine the dosimetric characteristics of a commercialized high-density polyethylene (HDPE) film using Fourier transformed infrared spectrometry (FTIR). Correlations have been established between the absorbed dose and radiation induced infrared absorption in polyethylene having a maximum at 965 cm−1 (transvinylene band) and 1716 cm −1 (ketone-carbonyl band). We have found that polyethylene dose-response is linear with dose for both bands up to1000 kGy. For transvinylene band, the dose-response is more sensitive if irradiations are made in helium. While, for ketone-carbonyl band, the dose-response is more sensitive when irradiations are carried out in air. The dose-rate effect has been found to be negligible when polyethylene samples are irradiated with electron beam high dose rates. The irradiated polyethylene is relatively stable for several weeks after irradiation.

Nickel-doped poly vinyl alcohol (PVA) films were developed for potential application in industrial sectors like radiation processing. We report in this paper the results of an experimental investigation of 60Co source γ-radiation effect on colorimetric, structural and morphological properties of PVA films doped with 0.5% Ni2+ ions (PVA/Ni2+). The PVA/Ni2+ films were irradiated by different gamma-radiation doses varying from 5 to 100 kGy. Color modification of films were studied using L∗, a∗ and b∗ color space measurements as function of the γ-dose and post-irradiation time. The visual change in all samples was verified by microstructure analysis, Fourier transforms infrared (FTIR) spectroscopy, X-Rays diffraction (XRD) and scanning electron microscopy (SEM). The color space exhibited a linear dose response at a dose ranging from 5 to 50 kGy, and then it reached saturation for higher γ-doses. The calculated color changes (ΔE) show a linear dose response relationship from 9.90 to 115.02 in the dose range from 0 to 50 kGy. It showed also the activation of stable color centers. The variability of the color change did not exceed 3% during 80 h (h) post-irradiation. Furthermore, the microstructure analysis evidenced that the color modification due to the optical activation of nickel-oxide (NiO) color center were obtained by complexing Ni2+ ions in irradiated PVA films. The obtained results inspire the possibility to use PVA films for the control process in industrial radiation facilities in dose range 5–50 kGy.

International centers based on research reactors (ICERR) project supported by IAEA, offers training and research in the application of advanced nuclear reactor technology. In this context of the project, alanine dosimeters were irradiated under mixed neutron/gamma irradiation in the core of the MINERVE research reactor at the CEA Cadarache. The integrated dose of the alanine was measured by electron spin resonance spectrometry with reference to an absorbed dose in water from a 60Co gamma-ray beam. Neutron and gamma dose components were calculated using the MCNP code. The neutron dose and relative effectiveness ( R E n ) for neutrons was evaluated using FLUKA code and Track Structure Theory (TST) formulations of alanine response towards irradiations with ions produced by neutron interactions with alanine. R E n values were found to be between 0.516 and 0.538. The measured dose was compared to the calculation results. The best agreement between the alanine integral measurements and model predictions (0.4%) was obtained by using the Cucinotta alanine detector response model.

A new hybrid monolithic silica xerogel containing sucrose has been synthesized via the sol–gel method. The resulting sucrose silica xerogels were exposed to gamma radiation with a dose in the range of 10–100 kGy. The effect of gamma rays on the physical and structural properties of sucrose silica xerogels was investigated by Fourier transform infrared spectroscopy (FTIR) and UV visible spectroscopy. The results of FTIR spectroscopy show that the irradiation process causes changes in the network's structure by inducing defects. The UV visible spectra present three main band defects; E′ center, Non-Bridging Oxygen Hole center (NBOHC) and carbonyl radicals in irradiated sucrose silica xerogel samples. Additionally, the results show that the values of optical band gap energy depend on irradiation. Therefore, generated defects suggest that the behavior of sucrose silica xerogels was modified from an insulator (Eg=5.82 eV) to a semiconductor (Eg=3.16 eV) under gamma irradiation.

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.

Samples of commercial silicate glass have been subjected to ion exchange by silver ions. The ion exchange was performed at 320 °C for periods from two minutes to one hour, in a molten mixture of AgNO3 and NaNO3 with a molar ratio of 1:99, 5:95 and 10:90. The ion exchange process was followed by different treatments: thermal annealing, gamma irradiation and their combined role in order to initiate the synthesis and control of silver aggregates in the surface of the glass matrix. UV-Visible absorption spectrometry results indicated that various states of silver existing in these glasses depend on heat treatment conditions. The silver ions (Ag+) exist in almost all conditions, neutral silver atoms (Ag0) exist only in samples subjected to heat treatment in the range of 250–450 °C, neutral silver aggregates (Ag0) produced by thermal annealing at 550 °C were responsible for the absorption bands observed from 305, 350 and 450 nm, respectively. The effect of gamma irradiation in doses from 10 to 100 kGy and thermal annealing on glass samples was also investigated. The main modification induced by gamma rays on the structure of silicate glass was the creation of colour centres, Non-Bridging Oxygen Hole Centres (NBOHCs) and trapped electrons. The (NBOHCs) defects caused the absorption of light. The Ag+ ions trapped electrons to form neutral silver Ag0. The first step of silver aggregation was observed, following the irradiation by gamma rays, as well as after thermal annealing. After annealing at 550 °C, silver atoms spread out over glass surface to form silver aggregates. An absorption band at 430 nm was observed characterizing the Surface Plasmon Resonance (SPR) of silver aggregates. The calculated average radius increases from 0.9 to 1.35 nm as the annealing time increased from 10 to 490 min. The average radius of nanoparticles varied as a function of absorbed dose. Unexpectedly, 10 kGy was found to be the optimally absorbed dose corresponding to the maximum of the nanoparticle’s average radius. The average radius of nanoparticles was decreased at a higher dose.

The Tunisian Beta irradiation facility (LINAC, CIRCE III) has been put into operation at the end of 2009. Such facility is designed essentially for sterilization of medical devices and conservation of foodstuff. The delivery and validation of a specified dose are key concerns of operators of electron beam irradiation facilities. In order to adjust the treatment conditions and to control the optimal operation of the accelerator, it is necessary to evaluate the absorbed dose and its distribution within material in the radiation field. Consequently, aspects from installation qualification to operation qualification are described together with the associated process variables. Technical parameters that directly influence the absorbed dose distribution in the product were examined by dosimetric measurements and compared to the data specified by the facility manufacturer. Two dosimeter types were used for measurements: radiochromic B3 and cellulose triacetate films.

In some irradiation facilities, dosimeters may receive their total absorbed dose in two or more absorbed-dose increments. Some interruptions may be planned, for example multiple irradiations may be used to avoid increasing irradiation temperature in electron beam accelerators. Other interruptions may be the result of unplanned irradiator shutdowns. Dose fractionation effects from both planned and unplanned interruptions should be quantified by determining the effect for different dose fractions and interruption times between successive irradiations. This work describes experiments carried out on the response of Gammachrome YR PMMA dosimeters to both single fractions and fractionated doses (two absorbed-dose increments separated by different intervals of time: 0.5, 1, 2, and 24 h). Specific absorbance measurements were carried out as a function of post-irradiation time, following the completion of irradiation in the total doses, from 20 to 250 min. Our work demonstrates that specific absorbance as a function of post-irradiation time depends significantly on total dose and the fractionation time. For measurements taken 2 h after irradiation, it was found that relative response variations due to dose fractionation were between −3% and +2% for dosimeters irradiated to 0.2 kGy and from −1.34% to −4% for those irradiated to 2 kGy.

The present paper reports the results of the colorimetric study of gamma-irradiated epoxy-resin films. Epoxy-resin samples were irradiated by gamma-rays with doses varying from 1 to 50 kGy. Color changes of epoxy-resin were observed and studied by the measurements of the variation of the L∗, a∗, b∗ as function of dose and post-irradiation time. Where L∗ is a measure of the magnitude of brightness from black to white, parameter a∗ describe the relative amounts of red and green, and parameter b∗ describes the relative amounts of yellow and blue color. Color changes (ΔE) were also calculated. They indicated a marked dependence of the absorbed doses showing the optical activation of the color centers. It was found that color changes (ΔE) due to absorbed dose increase from 6 to 50. Color change showed a low variability which did not exceed 3% for the measurements carried out between 1 and 72 h. The obtained results revealed that epoxy-resin films can be used as a new routine dosimeter or irradiation indicator in dose range 1–50 kGy.

Reference Standard Dosimeters are used to calibrate radiation environments and routine dosimeters. It can also be used in routine dosimetry applications for radiation processing where higher quality dosimetry measurements are required. Electron Spin Resonance (ESR) is a well-established Reference Standard Dosimetry system in industrial applications of ionising radiation, and its use is also proposed in radiation therapy and accident dosimetry. In the present experimental work, PGA solid state dosimeter (SSD) has been investigated using ESR spectroscopy to study the gamma radiation response of this material and to evaluate its dosimetric characteristics: dose response, room temperature fading, heat treatment effect during post-irradiation storage. Results obtained up to now confirm that PGA seems to be suitable material for ESR dosimetry applications.

A commercial glass has been investigated using UV–Vis spectrophotometry to study the gamma radiation response of this material andto evaluate its dosimetric characteristics: dose response, room temperature fading, effect of relative humidity during post-irradiation storage,temperature during irradiation and the dose rate effect. The overall uncertainty was also estimated.The obtained results demonstrate that the influence quantities on the glass response might be very significant and suitable corrections areindispensable.© 2008 Elsevier Ltd. All rights reserved. Keywords: Commercial glass; Gamma rays; Dosimetry; Environment effects 1. Introduction Several kinds of dosimeters are widely used for the processcontrol of the radiation processing applications such as steril-ization of medical devices, food preservation and other appli-cations. Especially dosimeters based on the radiation-inducedcolouration properties are also extensively used for the routinemeasurements of the absorbed dose. Most radiation processesare conducted under a wide variety of surrounding atmosphericconditions and, in fact, the response of dosimeters is signifi-cantly influenced by temperature during irradiation and doserate (McLaughlin et al., 1989). Since environmental conditionsmaydifferbetweencalibrationandpracticaluses,responsevari-ations of routine dosimeters with the surrounding conditionsmust be determined in order to correct such systematic errors.Some investigators have done researches on an availablewindow glass as a high dose dosimeter (Caldas and Teixeira,2002; Rodrigues, 2002). A suitable response has been shownwhen evaluated by spectrophotometer at specified wavelengthsin visible spectrum. The radiation induced colouration inglass can be affected by many environmental factors including

A commercial window glass has been investigated as a routine high dose dosimeter for gamma irradiation. The irradiated samples showed rapid fading at room temperature immediately after irradiation. This short-term rapid fading was followed by a slow fading at long-term. This strong initial fading is a problem for dosimetry purposes. However, when the dosimeter is measured at the same time interval after irradiation, it maintains proportionality to dose. Calibration curves have to be used for different time intervals after irradiation. In order to improve post-irradiation stability dosimeters were submitted to different post-irradiation thermal treatments from (−20) up to 150 °C. After that, optical absorbance measurements were carried out up to 2 months at room temperature. The heating at 150 °C for 20 min was found to be the most suitable procedure for the removal of unstable entities responsible for the initial rapid fading. Due to these heat treatments, variation of response was found almost negligible 24 h after irradiation for several months. Calibration curves demonstrated the applicability of this glass as routine dosimeter in the dose range of 0.5–90 kGy.

Several undyed and dyed polymer films are commercially available for dosimetry in intense radiation fields, especially for radiation processing of food and sterilisation of medical devices. The effects of temperature during irradiation and post-irradiation stability, on the response of these dosimeters are of importance to operators of irradiation facilities. The present study investigates the effects of temperature during irradiation by 2.2 MeV electrons beam accelerator and post irradiation storage on the response of several types of dosimeter films. All dosimeters showed a significant effect of temperature during irradiation and post-irradiation storage.

The present paper reports the results of the study on the effect of the fractionation dose on the response of Red-Perspex dosimeter. Several experiments were carried out by combining the two factors: number of fractionation and storage time between fractions. Dosimeters were irradiated by gamma-rays to total doses of 10 and 40 kGy. These doses were delivered as single fraction, as well as in five fractions separated by different intervals of time: 1, 24 h and stored at 10 or 40 °C between successive irradiation. Three batches of Red-Perspex dosimeters (KS, GB, and EB) were used in this study. The relative specific response of dosimeters indicates a marked dependence of the number of fractionation and storage time. It was found that response variations due to dose fractionation can reach 18% in particular at high storage time and high temperatures. The dose fractionation effect has been found to be dependent of the batches. The obtained results allowed us to determine the necessary corrections for estimating doses with high accuracy.

International audience; Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO 3 and NaNO 3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 °C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy.

The interactions of ionizing radiation with glass matrix produce ionization, excitation, and atomic displacement. The main modification induced during ┛, X rays, or electron irradiation on the glass structure is the creation of stable defects and the changes of the valence state of lattice atoms or of the incorporated impurities in glass. Some of the modified electronic configurations or defects cause preferential light absorption. Thus, glass becomes coloured and consequently these defects are called "colour centres". These centres are of many types and depending on the glass composition (Yokota, 1954, 1956) and are associated with optical absorption bands and EPR signals. The change of optical properties of glasses when subjected to ionizing radiation has been investigated by many authors due to wide applications of this kind of material. The earlier studies were focused on ways to prevent the darkening in glasses used in reactor or hot-cell windows and optical devices (Friebele, 1991). Recently, many studies have been concentrated on the application of the irradiation induced colour to develop recyclable colour glasses which is of great interest in the glass industry from the economical and environmental point of view (Sheng et al., 2002a). In addition to the applications mentioned above, the ionizing radiation induced colour centres in some glasses have been found wide application in radiation dosimetry (Farah et al., 2010; Fuochi et al., 2008, 2009; Mejri et al., 2008). This material is very interesting for dosimetry and very useful for many applications such as food irradiation, sterilization of medical devices, radiation treatment of industrial and municipal waste-water and radiation processing of materials. In the present work, we investigated the effect of the irradiation dose and thermal annealing on the formation and the decay of the induced colour centres in gamma irradiated silicate

Optical absorption investigation in a silicate glass before and after gamma irradiation was performed in the range 350–800 nm to study the induced colour centres to evaluate this potential as radiation‐sensitive material for dose measurements. The radiation induced bands are observed around 410 and 600 nm leading. The intensities of the overall absorption spectra are observed to increase progressively with increasing doses between 1 and 1200 kGy. The influence of isothermal annealing on the formation and the decay of the induced colour centres has been investigated. The activation energy characteristic of the annealing process was calculated from Arrhenius equation. The obtained values are equal to 0.251 and 0.310 eV for the 410 nm band and 0.261 and 0.353 eV for the 600 nm one. The similarity of these values for both bands suggests that the related optical transitions correspond to the same type of Non‐Bridging‐Oxygen Hole Centres (NBOHCs): (≡Si–O°) in different configurations.