kGy Dose Range Research Articles

Truffles decontamination treatment by ionizing radiation

A research project, funded by the Italian Ministry of Research and the European Union, is in progress aimed to develop processes to enhance, by irradiation, the safety and the wholesomeness of fresh products relevant for Italian food industry. Irradiation was performed on truffles, since the bacterial contamination impairs their trade in foreign countries. The microbial population and the shelf life under refrigeration were studied either on samples untreated or on samples submitted to γ-rays in a 1–2.5 kGy dose range. The effect of the treatment was monitored by UV and NMR techniques. Total microbial population and the shelf life prolongation were investigated. The synergistic effect of the dose, the packaging under vacuum and the storage/irradiation temperature resulted in a direct effect on the microbial load, spoilage and shelf life. After the irradiation, small variations in the intensity of some NMR resonances due to aromatic compounds and other unassigned compounds were observed. As confirmed by UV spectrophotometric data, these phenomena seemed to originate from a small degradation of polyphenols; the induced growth of soluble phenols suggested that the 1.5 kGy dose can be considered as the radiation dose threshold beyond which clear chemical modifications on truffles appear.

Thermoluminescence characteristics of BaB 4O 7:Dy phosphor

The polycrystalline powder samples of dysprosium-doped BaB 4O 7:Dy phosphor were prepared by a solid-state reaction in air at high temperature and the thermoluminescence (TL) glow curves and three-dimensional (3D) TL emission spectrum after 60Co gamma-ray irradiation was studied in the 20–130 kGy dose range at 293 K. The emission bands about at 480, 575, 660 and 750 nm were observed in the three-dimensional (3D) emission spectrum. The 3D TL emission spectrum of the BaB 4O 7:Dy is attributed to the characteristic emission from transitions of Dy 3+ ion. That no emission spectrum is observed for Dy 2+ ions is probably due to the emission wavelengths lying outside the measurement range. The distributions of traps produced by the irradiation of gamma-ray can be altered greatly by the change of the concentrations of Dy 3+ ion doped in BaB 4O 7 and peaks temperatures shift to higher temperature, this will be favorable for TL output. The depth of trap E of the main peak of BaB 4O 7:Dy is calculated as 1.38 eV. The influence of the 60Co gamma-ray irradiation doses on thermoluminescence of BaB 4O 7:Dy phosphor and the order of kinetics of TL glow peaks were also discussed. The TL–dose response of the BaB 4O 7:Dy polycrystalline powder sample to gamma-ray radiation in the range from 1 to 100 Gy for clinical dose levels is almost linearity. The experiment results showed that BaB 4O 7:Dy potential use as the materials of gamma-ray thermoluminescence dosimeter (TLD) for clinical dosimetry.

IAEA high-dose intercomparison in 60Co field

Nine high-dose calibration laboratories collaborated with the IAEA in a ‘double-blind’ intercomparison of absorbed dose in the 10–50 kGy dose range. Bureau International des Poids et Mesure undertook the analysis of the results as well as assisted in the development of the protocol. IAEA alanine-ESR transfer dosimeters were used for this intercomparison. The agreement was within 2.0% at 15 kGy and 2.2% at 45 kGy which is very good considering the variety of irradiation conditions employed by the participants. The mean of the dose values measured by the IAEA Dosimetry Laboratory was within 1% of the mean of the dose values stated by the participants for both dose values.

Effects of irradiation on respiration and ethylene production of apple slices

Respiration and ethylene production rates of irradiated apple slices from four apple cultivars were measured for 72 h. Doses less than 1.2 kGy had no effect on rates of CO2 production and O2 consumption, and irradiation at doses between 1.2 and 2.4 kGy had minimal effect for all cultivars. Respiratory response of ‘Idared’, ‘Law Rome’ and ‘Empire’ slices to irradiation was curvilinear, with maximum respiration occurring in the 3–6 kGy dose range. Response of ‘Delicious’ slices was linear over the irradiation dose range (0–11 kGy) studied. Respiratory quotient increased with irradiation dose. The degree of maturity of the slices affected respiratory responses. Irradiation reduced ethylene production of all slices. These results suggest that irradiation doses of up to 2.4 kGy can be used with minimum effect on the respiratory physiology of tissues. © 2000 Society of Chemical Industry

Detergent Powder: Investigation for Feasible Retrospective Dosimetry Using ESR Technique

An Electron Spin Resonance (ESR) study of radiation induced free radicals in the commonly used detergent powder (Surf), was conducted to examine its potential application for retrospective/high level dosimetry, including possible dating of the accidents. The radical ions present in the irradiated detergent powder were identified as arising predominantly from sodium tri poly phosphate (Na3P5O10) and sodium sulphate (Na2SO4). The physical mixture of sodium tri poly phosphate and sodium sulphate in 4:1 ratio was found to give an ESR response, similar to that of the detergent powder. These results suggest that the detergent powder can be used as a dosimeter in the 20 Gy to 18 kGy dose range, spanning over 3 orders of magnitude. The second derivative ESR spectra of the detergent powder irradiated to different doses showed that the relative yield of the radicals is independent of irradiation dose. The decay pattern of radicals when followed as a function of post irradiation days, lead to the idea about the contrasting decay characteristics of the radicals. From the ESR signals of the irradiated detergent samples, it is shown that radiation dose can be evaluated and the radiation incident can be dated with an accuracy of ±10%.

A new spectrophotometric readout for the alanine-triphenyl tetrazolium chloride system for high-dose dosimetry

The electron spin resonance (ESR) readout of radical concentration in irradiated L -alanine is well known as a transfer dosimetry system, however, the high cost of the ESR equipment is a serious handicap for large-scale routine application. In this study the reaction between irradiated L -alanine powder and aqueous solution of triphenyl tetrazolium chloride (TTC) was studied. The radical produced by irradiation of alanine reacts during the dissolution with TTC forming pink-colored formazans with absorption maxima around 401 and 487 nm. This readout method can be used in the 2–200 kGy dose range.

Use of the dichromate solution as a dosimeter for high dose and high dose rate

The radiolytic reduction of Cr(VI) in N 2O-saturated aqueous solutions has been investigated over a large range of pH by steady state radiolysis. At pH 3 in the presence of formate as scavenger for ·OH, G(−Cr(VI)) is higher than the expected yield and a strong dose rate effect is observed. The solution cannot be used for dosimetry at this pH. The proposed mechanism to explain the enhanced response and the dose rate dependence involves the reduction of the unstable radiolytically produced Cr(IV) by HCO 2 −. At pH 9.2 the reaction between Cr(IV) and formate is absent and no dose rate effect was observed up to 70 kGy min −1, which makes this system particularly attractive as a dosimeter in the 0.1–10 kGy dose range. Radiation chemical aspects relating to the use of this system as a high-dose and high-dose rate chemical dosimeter are discussed.

Radiation-chemical reaction of 2,3,5-triphenyl-tetrazolium chloride in liquid and solid state

In pulse radiolysis of 2,3,5-triphenyl-tetrazolium chloride (TTC) at around 360 nm fast formation of intermediate tetrazolium radical was observed under both oxidizing and reducing conditions. In the latter case bimolecular formation of formazan, absorbing at around 480 nm, was observed. This reaction is accompanied by combination to the diformazan dimer, absorbing over the spectral range 500–550 nm. A polyvinyl-alcohol-based TTC film was produced and tested for dosimetry purposes: it gave a measurable response in the 1–100 kGy dose range by evaluating the 50 μm thick TTC films at the absorption maximum of 493 nm.

黄色ＰＶＡフィルム線量計の１５０‐３００ｋｅＶ電子線線量測定への応用

Dose response characteristics of polyvinyl alcohol (PVA) films (thickness: about 20μm) dyed with methylene blue (MB) or methyl orange (MO) were studied and these films were applied to depthdose profile measurements for low-energy electrons (150 - 300 ke V) . Dose responses were measured in terms of optical density change of spectral peak at 662 and 434 nm for MB/PVA and MO/PVA, respectively. The dose response curves show good linearity in kGy dose-range up to about 30 kGy for MB/PVA film and to about 300 kGy for MO/PVA film. The measured depth-dose profiles were in relatively good agreement with those obtained by calculations using EDMULT code.

Simultaneous Thermal Bleaching and TL Measurements on LiF:Mg,Ti

Abstract The aim of this paper is to study the correlation of optical absorption bands and thermoluminescence peaks in LiF:Mg,Ti. Contrary to the numerous earlier publications related to this field, the present work uses a direct experimental approach. It reports on simultaneous thermal bleaching and thermoluminescence measurements on differently doped LiF:Mg,Ti single crystals in the 10-100 kGy dose range. The advantage of this technique is that the thermal bleaching curve of a given absorption band can be directly compared to the TL glow curve, since both were measured on the same sample, at the same time. This paper presents data on the 310, 350 and 380 nm absorption bands. The analysis reveals that all three bands strongly correlate with TL peaks 2 and 3, while they show no significant bleaching at the temperatures above peak 3. In addition the bleaching characteristics of the 350 nm band depend strongly on the Mg content of the sample.

Simultaneous Thermal Bleaching and TL Measurements on LiF:Mg,Ti

The aim of this paper is to study the correlation of optical absorption bands and thermoluminescence peaks in LiF:Mg,Ti. Contrary to the numerous earlier publications related to this field, the present work uses a direct experimental approach. It reports on simultaneous thermal bleaching and thermoluminescence measurements on differently doped LiF:Mg,Ti single crystals in the 10-100 kGy dose range. The advantage of this technique is that the thermal bleaching curve of a given absorption band can be directly compared to the TL glow curve, since both were measured on the same sample, at the same time. This paper presents data on the 310, 350 and 380 nm absorption bands. The analysis reveals that all three bands strongly correlate with TL peaks 2 and 3, while they show no significant bleaching at the temperatures above peak 3. In addition the bleaching characteristics of the 350 nm band depend strongly on the Mg content of the sample.

Electron paramagnetic resonance studies of γ-irradiated corn

γ-irradiated corn samples in the range 0.1.–2.0 kGy dose range were studied by the EPR technique. The signal consists of one structureless line with a width of 0.82±0.02 mT and a g-factor of 2.004±0.002. The intensity of this line shows a linear dependence in this dose range. The corn samples were ground prior to irradiation. Before grinding the samples did not show any EPR signal. After grinding they present a free radical EPR line with the same characteristics as that produced by the γ rays. The stability of these centers as a function of the temperature and time after irradiation was investigated. Analysis of these results suggest the presence of only one type of radical produced by both the mechanical and irradiation processes.

Kinetic Analysis of Al2O3:Mg,Y Glow Curves

Abstract The thermoluminescence of differently doped Al2O3:Mg, Y phosphors was measured in the 6.5 Gy - 6.5 kGy dose range. The glow curves were deconvoluted using a computerised least squares fitting method. The results show at least four different peaks, contributing to the thermoluminescence of Al2O3:Mg,Y in the 300-800 K temperature region. Most of the peaks are second order, indicating strong retrapping of the thermally untrapped charge carriers. Trap parameters for the deconvoluted glow peaks are given.