Gamma Radiation Field Research Articles

Study on the radiation effect of polyether-urethane in the gamma-radiation field

The radiation effect of γ-ray on polyether-urethane foam was studied. The gas products from irradiated samples were analyzed quantitatively and qualitatively by gas chromatography, the thermal property and radical intensity were determined by differential thermal gravimetry and electron spin resonance. The dynamic mechanical property, compression and tensile properties were analyzed. Positron annihilation lifetime of irradiated samples was also measured at room temperature in vacuum. The results show that the general mechanical properties of ETPU sample irradiated by γ-rays at a dose of 8.0·105 Gy is excellent, but there are considerable gas products and a great deal of radicals created, which indicates that the sample has been damaged by radiation. Relatively, the thermal stability of the sample remained fine.

Measurements of the neutron dose near a 15 Mv medical linear accelerator

In this work, simplified recombination methods for routine estimation of dose equivalent in mixed (gamma and neutrons) radiation field outside the irradiation field of linear medical accelerators is considered. The author's earlier reported method of H(10) measurements, involving determination of the recombination index of radiation quality, Q(4) by tissue-equivalent recombination chamber was combined with the new method for determination of the photon to neutron dose ratio D(X)/D(n) from the ratio of ion collection efficiencies measured in the investigated radiation field and in two reference fields of gamma and neutron radiations. The method is suitable when the neutron contribution to the total absorbed dose, D(n)/D, is >3%.

Investigation of the TL response of [formula omitted]: [formula omitted] crystals to X and gamma radiation fields

Double potassium yttrium fluoride crystals doped with optically active rare earth ions have been recently shown to be attractive thermoluminescence (TL) materials for ionizing radiation dosimetry. In this context appropriate studies have been performed to test TL response of K 2 YF 5 crystals doped with Dy 3 + ions to photon radiation fields. Within the framework of this research K 2 YF 5 crystals doped with 0.2, 1.0, 2.0, 5.0 and 10.0 at% Dy 3 + as well as K 2 DyF 5 and undoped K 2 YF 5 crystals have been synthesized under hydrothermal conditions. Polished crystal platelets with thickness of about 1 mm have been irradiated with X and gamma rays in order to study TL sensitivity as well as dose and energy response properties of these compositions in terms of the Dy 3 + concentration. Within this concentration series, K 2 YF 5 crystals doped with 1.0 at% Dy 3 + have been found to have maximum TL response due to a main dosimetric TL peak, which can be deconvoluted in three TL glow peaks centered at 96.4, 104.9 and 130.7 ∘ C , with reasonable linearity behavior over the studied dose range and good reproducibility of dose measurements. The sensitivity increase is observed for previously gamma-sensitized samples and this sensitization process seems also to induce the appearing of the TL glow peak at 130.7 ∘ C . As it has been turned, the linear TL signal coefficient for K 2 Y 0.99 Dy 0.01 F 5 is comparable to that of a CaSO 4 :Mn TL dosemeter, irradiated with a 137Cs gamma radiation source at the same conditions. Photon energy dependence of TL response for K 2 Y 0.99 Dy 0.01 F 5 has been evaluated and it has been found that TL response of this composition to the 41.1 keV X-rays is 30 times higher than that to the 662 keV gamma rays. This fact points out that K 2 YF 5 crystals doped with Dy 3 + have potential as promising materials to be used for low-dose dosimetry in X-rays diagnostic or industrial radiography.

Calibration and characterisation of extremity dosimeters

The increasing use of radiation in the medical field is providing great advances in health improvement. However, these techniques can generate an increase in the number of professionals exposed to radiation. The Brazilian authorities (Brazilian Nuclear Energy Commission ? CNEN) have imposed the monitoring of specific body parts of professionals. One of these obligations is the monitoring of the extremities of these professionals, so as to verify the application of the radiology protection principles through the comparison of the values of dose that are found with the limits permitted by the current legislation. The objective of this paper is the calibration and characterisation of the extremity dosimeters made at CDTN/CNEN in the 'Personal Dose Equivalent for Extremities ? Hp (0.07)' quantity, using a finger simulator in gamma radiation fields and X-ray; and to base the calibration process of the system on the international legislation.

Argentine intercomparison programme for personal dosimetry

An Intercomparison Programme is being carried out in Argentina for individual monitoring services. The programme was designed to test, on a voluntary basis, the performance of the laboratories that provide individual monitoring services for X and gamma radiation fields in the range from low-level dose up to 100 mSv. Irradiations were performed in full accordance with ISO 4037-3 recommendations by the Regional Reference Centre for Dosimetry (CRRD), belonging to Atomic Energy Commission (CNEA) and the Physical Dosimetry Laboratory of the Nuclear Regulatory Authority (ARN). At the same time, several items have been asked to each participant pertaining to the action range, the detectors' characteristics, the laboratory procedures, the existence of an algorithm and its use for the dosemeter evaluation. In this study the evolution of the laboratories' performance throughout the programme, based on ISO 14146 acceptance criteria, is shown.

Monte Carlo study of a 60Co calibration field of the Dosimetry Laboratory Seibersdorf

The gamma radiation fields of the reference irradiation facility of the Dosimetry Laboratory Seibersdorf with collimated beam geometry are used for calibrating radiation protection dosemeters. A close-to-reality simulation model of the facility including the complex geometry of a 60Co source was set up using the Monte Carlo code MCNP. The goal of this study is to characterise the radionuclide gamma calibration field and resulting air-kerma distributions inside the measurement hall with a total of 20 m in length. For the whole range of source-detector-distances (SDD) along the central beam axis, simulated and measured relative air-kerma values are within +/-0.6%. Influences on the accuracy of the simulation results are investigated, including e.g., source mass density effects or detector volume dependencies. A constant scatter contribution from the lead ring-collimator of approximately 1% and an increasing scatter contribution from the concrete floor for distances above 7 m are identified, resulting in a total air-kerma scatter contribution below 5%, which is in accordance to the ISO 4037-1 recommendations.

Features of the radioactive decay of Mössbauer isotopes in the presence of an intrinsic gamma-radiation field

A limit for the concentration of radioactive nuclei (3 × 1014 1/cm3) of the Mössbauer emitters 119mSn and 125mTe below which the earlier demonstrated effect of the collective nuclear decay vanishes is experimentally found in the framework of a study aimed at the control of the decay of nuclear levels. A general theoretical concept of the phenomenon is presented. Based on this concept, the parameters of the nonexponential decay are numerically estimated. The notion of the width of the Mössbauer γ photon is introduced.

Measurements of fast neutrons in Hiroshima by use of 39Ar

The survivors of the A-bomb explosions over Hiroshima and Nagasaki were exposed to a mixed neutron and gamma radiation field. To validate the high-energy portion of the neutron field and thus the neutron dose to the survivors, a method is described that allows retrospective assessment of the fast neutrons from the A-bombs. This is accomplished by the extraction of the noble gas argon from biotites separated from Hiroshima granite samples, and then the detection of the (39)Ar activity that was produced by the capture of the fast neutrons on potassium. Adjusted to the year 1945, activities measured in the first samples taken at distances of 94, 818, 992, and 1,173 m from the hypocenter were 6.9+/-0.2, 0.32+/-0.01, 0.14+/-0.02, and 0.09+/-0.01 mBq/g K, respectively. All signals were significantly above detector background and show low uncertainties. Considering their uncertainties they agree with the calculated (39)Ar activation in the samples, based on the most recent dosimetry system DS02. It is concluded that this method can be used to investigate samples obtained from large distances in Hiroshima, where previous data on fast neutrons are characterized by considerable uncertainties. Additionally, the method can be used to reconstruct the fast neutron fluence in Nagasaki, where no experimental data exist.

Evaluation of reproductibility and detection limit of CaSO4: dy radiation detectors

Measurement response of thermoluminescent dosimeter, TLD, used by workers or placed at positions where gamma radiation field could be in action affecting biological tissues, should be completely characterized, in order to achieve the radiation quantity with precision and confidence. Among the evaluations concerned to its characterization, the detector reproductibility is of fundamental importance, because detectors present inside the TLD will be used many times in routine. Reproductibility is studied by repeated exposure to the same radiation field. The minimum detection limit is another important characteristics of a TLD. In this work evaluations of reproductibility and minimum detection are presented, for dosimeters produced at IPEN.

Phantom evaluations of a dedicated dual-head scintimammography system

Results of aboratory evaluations are presented of the dual-head scintimammography system using two opposed and co-registered compact gamma heads. The system is intended for clinical studies imaging suspicious lesions in a compressed breast. The studies were performed using 5 cm and 6 cm compressed breast phantoms with lesion sizes from 6 to 10 mm and lesion to breast tissue activity ratios from 6 to 10. Two imagers with a field-of-view (FOV) of 15 cm×20 cm were placed on the opposite sides of the breast phartoms. In some studies anthropomorphic torso phantom was used to simulate realistic scatter gamma radiation field. Two types of parallel-hole lead collimators were employed. Combining the co-registered images from both detector heads resulted in an over two-fold increase in lesioin contrast in the central plane of the phantom and substantially increased detection sensitivity over the whole breast volume, especially of asymmetrically placed small lesions. The results confirm the important advantage of a co-registoed two-head scintimammography system over a single head system in lesion detection and localization.

Fast digitizing techniques applied to scintillation detectors

A 200 MHz 12-bit fast transient recorder card has been used for the digitization of pulses from photomultipliers coupled to organic scintillation detectors. Two modes of operation have been developed at ENEA-Frascati: a) continuous acquisition up to a maximum duration of ∼ 1.3 s corresponding to the full on-board memory (256 MSamples) of the card: in this mode, all scintillation events are recorded; b) non-continuous acquisition in which digitization is triggered by those scintillaton events whose amplitude is above a threshold value: the digitizing interval after each trigger can be set according to the typical decay time of the scintillation events; longer acquisition durations (>1.3 s) can be reached, although with dead time (needed for data storage) which depends on the incoming event rate. Several important features are provided by this novel digital approach: high count rate operation, pulse shape analysis, post-experiment data re-processing, pile-up identification and treatment. In particular, NE213 scintillators have been successfully used with this system for measurements in mixed neutron (n) and gamma ( γ ) radiation fields from fusion plasmas: separation between γ and neutron events is made by means of a dedicated software comparing the pulse charge integrated in two different time intervals and simultaneous neutron and γ pulse height spectra can be recorded at total count rates in the MHz range. It has been demonstrated that, for scintillation detection applications, 12-bit fast transient recorder cards offer improved performance with respect to analogue hardware; other radiation detectors where pulse identification or high count rate is required might also benefit from such digitizing techniques.

Investigation on the chemical behaviour of a crown ether irradiated in high gamma radiation fields

Summary The performance, after irradiation at high gamma radiation doses, of the material known under the commercial name SrResin (Eichrom Industries, USA), consisting of a crown ether, 4,4′(5′)-bis(t-butyl-cyclohexane)-18-crown-6, in a solution of 1-octanol absorbed in a polymeric support, has been characterised. The matrix, disposed in columns moistened with dilute HNO3 or imbibed with 8 M HNO3, was irradiated with a 60Co radiation field at doses from 2 kGy up to 40 kGy, and the separative properties of the columns were measured through the barium–strontium separation. Although the effects of the irradiation are displacement of the elution volumes and an increase of losses of the elements, quantitative separation of barium and strontium is still feasible.

Adsorption on insulator materials enhanced by D implantation

Abstract Many insulator materials used in ITER are exposed to a gas phase composed of D, T and a plasma with hydrocarbons, Fe and other particles combined with the presence of an intense neutron and gamma radiation field. Some of these materials (Al2O3 and SiO2) are implanted at room temperature with low energy D and H ions in order to simulate some of the DT gas effects. The implantation is characterized using optical absorption and elastic recoil detection analysis (ERDA) techniques. It is observed that ion implantation as well as electron or gamma irradiation increases the surface scattering and the concentration of C and H adsorbed at the surface, suggesting that a radiation-induced surface degradation process is taking place and an increase of the surface adsorption capability. The effect is higher for higher dose implantation and for lower energy.

Galvanic Corrosion between the Nuclear Waste Disposal Container Material Pairs of Copper-Nickel Alloys and Carbon Steel in Salt Brines

Abstract In the present work, the galvanic corrosion of candidate disposal container material pairs of Cu-Ni 90-10/TStE355 carbon steel (CS) and Cu-Ni 70-30/TStE355 steel (contact specimens), respectively, has been investigated in two disposal-relevant salt brines at 150°C, both without gamma irradiation and in the presence of a gamma radiation field of 10 Gy/h (irradiated brine environment only for Cu-Ni 70-30/TStE355 steel). The results of the long-term immersion experiments up to 1.5 years indicate that in the sodium chloride (NaCl)-rich test brine, both with and without gamma radiation, the coupled material pairs form stable corrosion protective surface layers, and, therefore, no galvanic corrosion occurs. In the magnesium chloride (MgCl2)-rich Q-brine, however, both in unirradiated and irradiated environments, the corrosion surface layers formed on the steel show localized corrosion attack, and, subsequently, galvanic corrosion occurs. This results in localized corrosion on the less noble coupled CS ...

Multifractal characterization of airborne geophysical data at the Oak Ridge facility

Scaling analyses on geophysical measurements of electrical conductivity, gamma radiation, and magnetic fields, at the Oak Ridge Reservation were conducted. The electrical conductivity and magnetic data exhibited multifractality in the north-south and east-west directions. The radiation data were observed to be non-scaling; a variogram with a sill was found to be more appropriate. The scaling of the EC and magnetic was generally within a range smaller than the maximum distance selected, as periodicity dominated at the larger distances. The electrical conductivity had anisotropy in the scaling of their variograms. But the magnetic data appear to have an isotropic scaling. The underlying statistics of the fields were near Gaussian for the electrical conductivity, but essentially Gaussian for the magnetic data. In environmental hydrogeology, knowledge of the spatial distribution of the intrinsic permeability, K, is very helpful in understanding the transport and spreading of contaminant plumes. Our previous studies have shown that the subsurface permeability, K, is multifractal. Detailed measurement of K is costly. Hence, large data sets of value collected both on a fine scale and over large distances are rare. In this study, we hypothesize that geophysical data could be used indirectly as a surrogate measurement for K, for obtaining statistical information on scale limited K data, and perhaps, directly at sites where K and electrical conductivity are correlated.

05/00092 Atmospheric dispersion of argon-41 from a nuclear research reactor: measurement and modelling of plume geometry and gamma radiation field: Lauritzen, B. et al. International Journal of Environment and Pollution2003, 20, (1–6), 47–54

05/00092 Atmospheric dispersion of argon-41 from a nuclear research reactor: measurement and modelling of plume geometry and gamma radiation field: Lauritzen, B. et al. International Journal of Environment and Pollution2003, 20, (1–6), 47–54

Super radiation hard vacuum phototriodes for the CMS endcap ECAL

The energy resolution σ / E of the electromagnetic calorimeter (ECAL) in the energy range of 50–500 GeV is defined mainly by two terms: stochastic α / √ E and constant C . The photoreadout of the CMS Endcap ECAL consists of vacuum phototriodes (VPT), which are broadening a signal from n p photoelectrons characterized by the excess noise factor F = n p ( σ / E ) 2 . The technical specification of the CMS ECAL requires the value of F to be smaller than 4 in the CMS LHC environment during 10 years of detector operation. In this paper we present results of the VPT performance study in a magnetic field up to 4 T, in a gamma radiation field of 0–50 kGy and in a neutron fluence of 7 × 10 15 n / cm 2 . The standard phototriodes FEU-188 with faceplates from UV glass used in CMS ECAL as well as VPTs with super radiation hard cerium-doped glasses were investigated at the 60 Co gamma facility, a neutron generator and a nuclear reactor in the Petersburg Nuclear Physics Institute (PNPI). The dependence of the VPT gain and the excess noise factor in magnetic fields on the fine-mesh plane orientation has also been studied.

Radiometric modeling through the combined use of the EDR gamma scanner and the VISIPLAN dose assessment tool

In this paper, we present the work performed on the integration of a new gamma scanner prototype, known as EDR, with a 3D-dose assessment software tool called VISIPLAN. It is one of the first approaches to merge gamma imaging instrumentation and a 3D-dose assessment program into a combined operative hardware–software solution for the characterization of a site in the field of radiation protection. The main features of the scanner design are presented here, together with a representative part of the tests performed during its characterization. The EDR directional sensitivity is determined for two gamma radiation fields originating from 137Cs and 60Co sources and forms the basis for the interpretation of the gamma scans using VISIPLAN. The combination of a 3D-source model and the detailed instrument response function can determine the source activities from the gamma scans, and also enables in a second step, the simulation of the dose-rate field on the site. The integration of the two tools was tested in a laboratory and validated in an industrial facility.

Super radiation hard vacuum phototriodes for the CMS endcap ECAL

The energy resolution σ / E of the electromagnetic calorimeter (ECAL) in the energy range of 50–500 GeV is defined mainly by two terms: stochastic α / √ E and constant C. The photoreadout of the CMS Endcap ECAL consists of vacuum phototriodes (VPT), which are broadening a signal from n p photoelectrons characterized by the excess noise factor F = n p ( σ / E ) 2 . The technical specification of the CMS ECAL requires the value of F to be smaller than 4 in the CMS LHC environment during 10 years of detector operation. In this paper we present results of the VPT performance study in a magnetic field up to 4 T, in a gamma radiation field of 0–50 kGy and in a neutron fluence of 7 × 10 15 n / cm 2 . The standard phototriodes FEU-188 with faceplates from UV glass used in CMS ECAL as well as VPTs with super radiation hard cerium-doped glasses were investigated at the 60Co gamma facility, a neutron generator and a nuclear reactor in the Petersburg Nuclear Physics Institute (PNPI). The dependence of the VPT gain and the excess noise factor in magnetic fields on the fine-mesh plane orientation has also been studied.

Compound dual radiation action theory for 252Cf brachytherapy.

The existing dosimetry protocol that uses the concept of RBE for 252Cf brachytherapy contains large uncertainties. A new formula has been developed to correlate the biological effect (i.e. cell survival fraction) resulting from a mixed n + gamma radiation field with two physical quantities and two biological quantities. The formula is based on a pathway model evolved from that of the compound-dual-radiation-action (CDRA) theory, previously proposed by Rossi and Zaider. The new model employs the recently published data on radiation-induced DNA lesions. The new formula is capable of predicting quantitatively the synergistic effect caused by the interactions between neutron events and gamma ray events, and it is intended to be included into a new dosimetry protocol for future 252Cf brachytherapy.