Gamma Radiation Field Research Articles

Study of the luminescent behavior of Spectrolite + Teflon pellets in 90Sr + 90Y beams

The Spectrolite, from the silicate family, a variety of Labradorite, was already studied in relation to its thermoluminescence (TL) and optically stimulated luminescence (OSL) responses, in high-dose gamma radiation fields; the results indicated their good application as gamma radiation detectors. In the present work, the analyses performed to investigate powdered Spectrolite are presented, by means of the XRD, SEM and EDX techniques. The luminescent behavior of Spectrolite + Teflon samples, in the concentration of 1:1, was studied in beta radiation beams (90Sr + 90Y), using the luminescent phenomena of TL and OSL. The results showed adequate TL and OSL reproducibility of the samples; the dose–response curves for both techniques presented a linear behavior in a range from 0.5 Gy to 1 kGy, and the fading showed that after 150 h there were 46.7% and 31.6% of the remaining signal of samples for TL and OSL responses, respectively. Therefore, the Spectrolite + Teflon pellets may be used in beta radiation dosimetry.

モンテカルロ法による放射線量の簡易計算法

Large amounts of fission products (FP) were released at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electricity Power Company due to the accident, initiated by the tsunami that was triggered by the East Japan Great Earthquake on March 11, 2011. It has been more than five years since the disaster occurred. The radioactivity owing to FP deposited on the grounds, houses, forests and so on have been decreasing steadily by the decay of FP, soil infiltration, weathering effect and the planned decontamination. As a result, the residence restriction areas have been re-organized as areas prepared for evacuation cancellation and it has been allowed for the residents to return to their homes. The conscious surveys for residents showed that they were worrying about the influence of radioactivity to human body. Therefore, it is necessary to let them know sufficient detailed information and knowledge. The decrease of radiation dose depends considerably on the density of the building construction materials, so that it would be desirable for indoor radiation dose rate to be estimated by taking account of housing types and floor plans. This paper deals with a novel method for calculating radiation dose rate within a building and around its surroundings. We employed the Monte Carlo method to calculate gamma ray penetration through various shield configurations and the absorption within an object positioned at an evaluation point. The gamma rays shifted to lower energy levels caused by the Compton scattering, i.e. buildup fluxes, were simply treated using the buildup factor as a function of the mean free path of photons. RADAR-γ code which has been developed on the basis of this study was benchmarked for a simplified geometry case with Cesium 137 deposited on the ground surface. The results were compared with the point-kernel integration code QAD-CGGP-A, which has been widely used in radiative physics analyses to calculate operational exposures and gamma radiation fields through shielding. The results of both methods were in good agreement. It was confirmed that the proposed method could be used for predicting radiation dose rate in the area where FP have been deposited.

Response of exfoliated human buccal epithelium cells to combined gamma radiation, microwaves, and magnetic field exposure estimated by changes in chromatin condensation and cell membrane permeability

Modulation of the biological effects produced by ionizing radiation (IR) using microwave and magnetic fields has important theoretical and practical applications. Response of human buccal epithelium cells to different physical agents (single and combined exposure to 0.5–5 Gy γ-radiation (60Co); microwaves with the frequency of 36.64 GHz and power densities of 0.1 and 1 W/m2, and static magnetic field with the intensity of 25 mT) has been investigated. The stress response of the cells was evaluated by counting heterochromatin granules quantity (HGQ) in the cell nuclei stained with orcein. Membrane permeability was assessed by the percentage of cells stained with indigocarmine (cells with damaged membrane). The increase of heterochromatin granules quantity (HGQ), i.e. chromatin condensation was detected at the doses of 2 Gy and higher. Changes in the cell membrane permeability to indigocarmine expressed the threshold effect. Membrane permeability reached the threshold at the doses of 2–3 Gy for the cells of different donors and did not change with the increase of the dose of γ-radiation. Cells obtained from different donors revealed some individual peculiarities in their reaction to γ-radiation. The static magnetic field and microwaves applied before or after γ-radiation decreased its impact, as revealed by means of HGQ assessment.

Indirect method to monitor the site size of sealed TEPCs

Tissue equivalent proportional counters (TEPCs) can be used as radiation monitors in different radiation environments, including on board of a spacecraft or aircraft. Usually, the gas density of the counter is set to simulate site sizes of 1 μm or 2 μm. However, especially for sealed counters which should be operative for long time without being refilled, the gas density inside the counter could change significantly. The immediate consequence of density variations is a gas gain shift. This in turn is not a serious problem, because the gas gain can be measured and corrected by increasing the bias voltage. A more critical consequence of an increase of the density is that the shape of the microdosimetric spectrum changes, affecting the response of the detector. Consequently, this limits the reliability of sealed TEPC over time, especially because the gas pressure is not directly monitored. Therefore, the aim of this study is to propose an experimental procedure to estimate the TEPC sensitive-site size by performing two independent measurements, one in a gamma radiation field and the other one in a neutron field. The results show that it is possible to assess the site size of sealed TEPCs with an accuracy of 5%.

A DOSE CALCULATION MODEL APPLICATION FOR INDOOR EXPOSURE TO TWO-LAYER WALLS GAMMA IRRADIATION: THE CASE STUDY OF CERAMIC TILES

A calculation model for determining the indoor dose due to building materials with significant concentration of radioactivity has been applied to the case study of ceramic tiles; the model allows the contribution of bearing walls and wall covering materials to be calculated. The model is implemented in FORTRAN 77 and provides a quantification of the gamma radiation field (in terms of external dose rate in air, nGyh-1) inside a room with known dimensions. Application model results have been validated both by comparison with the results obtained by other authors and by experimental measurements. Model sensitivity and performances have been analysed and lastly the case studies focused on ceramic tiles have been proposed.

Neutron-Irradiated Samples as Test Materials for MPEX

Plasma-material interaction is a major concern in fusion reactor design and analysis. The Material Plasma Exposure eXperiment (MPEX) will explore plasma-material interaction under fusion reactor plasma conditions. Samples with accumulated displacement damage (characterized by displacements per atom) produced by fast neutron irradiations in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory will be studied in the MPEX facility. This paper presents assessments of the calculated induced radioactivity and resulting radiation dose rates of a variety of potential fusion reactor plasma-facing materials, e.g., tungsten. The scientific code packages Monte Carlo N-Particle (MCNP) and Standardized Computer Analyses for Licensing Evaluation (SCALE) were used to simulate irradiation of the samples in HFIR. This included the generation and depletion of nuclides in the material and the subsequent composition, activity levels, gamma radiation fields, and resultant dose rates as a function of cooling time. A challenge of the MPEX project is to minimize the radioactive inventory in the preparation of the samples and the sample dose rates for inclusion in the MPEX facility.

RETRACTED ARTICLE: Characterization of Gamma Irradiated Low and High Density Polyethylene Using the FTIR and DSC Technique

Polyethylene is available in different grades such as low density polyethylene (LDPE) and high density polyethylene (HDPE). The linearity of low density of it is very important. In this study two grades of polyethylene were irradiated with a uniform field of gamma radiation. All the samples were punched in dumbbell shape. The effects of gamma radiation on the polymers were analyzed by FTIR spectroscopy, tensile test and differential scanning calorimetry. Experimental data showed that the melting point and elastic modulus of HDPE increased up to a certain level of irradiation and then decreased, but for LDPE did not change any more.

New approach to neutron spectrometry with multi element scintillator

A recently developed scintillator has been investigated for possible use as a dual detector for neutron and gamma spectrometry. A 7Li-enriched version of the scintillator has been investigated. The 35Cl(n,p)35S nuclear reaction provides a possibility for fast neutron detection. The sensor has been mounted on a photomultiplier tube controlled with a miniature electronics board and irradiated in different gamma and neutron radiation fields. A series of experiments has been carried out with different gamma energies as well as well with mono-energetic neutrons from a KN Van de Graaff accelerator, and the pulse height spectra have been measured. To clarify different features observed on the response functions of the detector, a Monte Carlo model of the scintillator has been built using MCNP6 and emitted charged particles have been tracked. The simulation data along with the experiments are analyzed, compared and reported.

Durability and shielding performance of borated Ceramicrete coatings in beta and gamma radiation fields

Ceramicrete™, a chemically bonded phosphate ceramic, was developed for nuclear waste immobilization and nuclear radiation shielding. Ceramicrete products are fabricated by an acid–base reaction between magnesium oxide and mono potassium phosphate. Fillers are used to impart desired properties to the product. Ceramicrete’s tailored compositions have resulted in several commercial structural products, including corrosion- and fire-protection coatings. Their borated version, called Borobond™, has been studied for its neutron shielding capabilities and is being used in structures built for storage of nuclear materials. This investigation assesses the durability and shielding performance of borated Ceramicrete coatings when exposed to gamma and beta radiations to predict the composition needed for optimal shielding performance in a realistic nuclear radiation field. Investigations were conducted using experimental data coupled with predictive Monte Carlo computer model. The results show that it is possible to produce products for simultaneous shielding of all three types of nuclear radiations, viz., neutrons, gamma-, and beta-rays. Additionally, because sprayable Ceramicrete coatings exhibit excellent corrosion- and fire-protection characteristics on steel, this research also establishes an opportunity to produce thick coatings to enhance the shielding performance of corrosion and fire protection coatings for use in high radiation environment in nuclear industry.

Radiation-hard power electronics for the ATLAS New Small Wheel

The New Small Wheel (NSW) is an upgrade for the ATLAS detector to provide enhanced triggering and reconstruction of muons in the forward region. The large LV power demands of the NSW necessitate a point-of-load architecture with on-detector power conversion. The radiation load and magnetic field of this environment, while significant, are nevertheless still in the range where commercial-off-the-shelf power devices may suffice.We present studies on the radiation-hardness and magnetic-fieldtolerance of several candidate buck converters and linearregulators. Device survival and performance are characterized whenexposed to gamma radiation, neutrons, protons and magnetic fields.

Determining Reactor Graphite Lifespan from Thermal Properties Degradation

This work assesses real graphite lifespan distribution of pressurized-tube reactors (RBMK) with graphite moderator. The changes in heat exchange and heat transfer conditions were taken into consideration, which changes are induced by the thermal properties’ degradation and the changes in the form of structural elements. Besides, some features associated with the differences in the neutron flux spectrum and differences in characteristics of gamma radiation field in the fuel and in the channels of control and protection system (CPS) were all taken into account.

Modeling the radiolysis of supercritical water by fast neutrons: density dependence of the yields of primary species at 400°c.

A reliable understanding of radiolysis processes in supercritical water (SCW)-cooled reactors is crucial to developing chemistry control strategies that minimize the corrosion and degradation of materials. However, directly measuring the chemistry in reactor cores is difficult due to the extreme conditions of high temperature and pressure and mixed neutron and gamma-radiation fields, which are incompatible with normal chemical instrumentation. Thus, chemical models and computer simulations are an important route of investigation for predicting the detailed radiation chemistry of the coolant in a SCW reactor and the consequences for materials. Surprisingly, information on the fast neutron radiolysis of water at high temperatures is limited, and even more so for fast neutron irradiation of SCW. In this work, Monte Carlo simulations were used to predict the G values for the primary species e(-)aq, H(•), H2, (•)OH and H2O2 formed from the radiolysis of pure, deaerated SCW (H2O) by 2 MeV monoenergetic neutrons at 400°C as a function of water density in the range of ∼0.15-0.6 g/cm(3). The 2 MeV neutron was taken as representative of a fast neutron flux in a reactor. For light water, the moderation of these neutrons after knock-on collisions with water molecules generated mostly recoil protons of 1.264, 0.465, 0.171 and 0.063 MeV. Neglecting oxygen ion recoils and assuming that the most significant contribution to the radiolysis came from these first four recoil protons, the fast neutron yields were estimated as the sum of the G values for these protons after appropriate weightings were applied according to their energy. Calculated yields were compared with available experimental data and with data obtained for low-LET radiation. Most interestingly, the reaction of H(•) atoms with water was found to play a critical role in the formation yields of H2 and (•)OH at 400°C. Recent work has underscored the potential importance of this reaction above 200°C, but its rate constant is still controversial.

Gamma radiation and magnetic field mediated delay in effect of accelerated ageing of soybean.

Soybean seeds were exposed to gamma radiation (0.5, 1, 3 and 5kGy), static magnetic field (50, 100 and 200 mT) and a combination of gamma radiation and magnetic energy (0.5kGy + 200 mT and 5kGy + 50 mT) and stored at room temperature for six months. These seeds were later subjected to accelerated ageing treatment at 42°C temperature and 95-100% relative humidity and were compared for various physical and biochemical characteristics between the untreated and the energized treatments. Energy treatment protected the quality of stored seeds in terms of its protein and oil content . Accelerated aging conditions, however, affected the oil and protein quantity and quality of seed negatively. Antioxidant enzymes exhibited a decline in their activity during aging while the LOX activity, which reflects the rate of lipid peroxidation, in general, increased during the aging. Gamma irradiated (3 and 5kGy) and magnetic field treated seeds (100 and 200 mT) maintained a higher catalase and ascorbate peroxidase activity which may help in efficient scavenging of deleterious free radical produced during the aging. Aging caused peroxidative changes to lipids, which could be contributed to the loss of oil quality. Among the electromagnetic energy treatments, a dose of 1-5kGy of gamma and 100 mT, 200mT magnetic field effectively slowed the rate of biochemical degradation and loss of cellular integrity in seeds stored under conditions of accelerated aging and thus, protected the deterioration of seed quality. Energy combination treatments did not yield any additional protection advantage.

Performance of radiation survey meters in X- and gamma-radiation fields.

The aim of this work was to investigate the different types of radiation detectors commonly used for radiation protection purposes as survey meters. The study was performed on survey meters that use different detectors as ionisation chamber, Geiger Mueller (GM) counter and scintillation detector. For each survey meter, energy dependence and angular response in X- and gamma-radiation fields was tested. The following commercially available survey meters were investigated: ionisation chambers Victoreen 451P, Babyline 31 and VA-J-15A, Geiger counter MRK-M87, 6150 AD6 and FAG FH 40F2 and scintillation counter 6150 ADB. As a source of gamma radiation, (137)Cs and (60)Co were used whereas X-ray radiation fields were generated using an X-ray unit. The radiation characteristics of the survey meters were mostly in compliance with references estimated by standard IEC 1017-2. However, some of them showed larger deviation at lower energies. GM counters exhibit strong energy dependence for low-energy photons.

Monitoring Performance of the Cameras under the High Dose-Rate Gamma Ray Environments

CCD/CMOS cameras, loaded on a robot system, are generally used as the eye of the robot and monitoring unit. A major problem that arises when dealing with images provided by CCD/CMOS cameras under severe accident situations of a nuclear power plant is the presence of speckles owing to the high dose-rate gamma irradiation fields. To use a CCD/CMOS camera as a monitoring unit in a high radiation area, the legibility of the camera image in such intense gamma-radiation fields should therefore be defined. In this paper, the authors describe the monitoring index as a figure of merit of the camera's legibleness under a high dose-rate gamma ray irradiation environment. From a low dose-rate (10 Gy h) to a high dose-rate (200 Gy h) level, the legible performances of the cameras owing to the speckles are evaluated. The numbers of speckles generated by gamma ray irradiation in the camera image are calculated by an image processing technique. The legibility of the sensor indicator (thermo/hygrometer) owing to the number of speckles is also presented.

Failure of the negative voltage regulator in medium-photon-energy X radiation fields

Negative voltage regulators were examined in the effective 60-keV and 170-keV bremsstrahlung fields, as well as in the field of 60Co gamma-radiation. Most devices irradiated in the fields of medium-dose-rate breaking radiation failed to operate after absorption of very small total doses of ionizing radiation, in the range of 37–132Gy(SiO2). However, all samples irradiated in the gamma radiation environment remained completely functional, even after deposition of a total dose of 500Gy(SiO2). Devices irradiated with higher input voltages failed after absorption of low total doses, whereas the load current increase mitigated and even prevented circuit failures in X radiation fields. The high radiation sensitivity of the LM2990T-5 voltage regulators operating in the bremsstrahlung fields was a consequence of the dose enhancement on the gold–aluminum connection between the silicon chip and ground contact. Computer model simulations indicated that the primary failure mechanisms were the generation of radiation-induced leakage currents alongside the npn transistors in the operational amplifier circuit. The difference between the voltage regulator responses in various bremsstrahlung environments was affected by the time-dependent effects, leading to the partial recovery of radiation-induced trapped charge.

A prototype of an ionization chamber for gamma radiation beams of 60Co: Experimental and Monte Carlo preliminary results

Ionization chambers are the most widely used instruments for dosimetry in radiotherapy. With the aim to test new configurations and materials using low-cost and easily-available components, verify the possibility of its application in the gamma radiation field of 60Co and fulfill the need of a chamber for scientific metrological purposes, in this paper the prototype of a plane-parallel ionization chamber has been designed and built, and its performance has been studied at the SSDL of KARAJ. The front wall and back wall of the chamber were made of graphite and Plexiglas respectively, as opposed to the one type of material in commercially available chambers. The collecting electrode has a diameter of 20 mm. The sensitive volume is 0.63 cm3. It was found that the Leakage current, the short-term stability and the polarity effect were within the international recommendations. The results were compared with those of a reference cylindrical chamber. The maximum difference observed in this comparison was 1.1%. The relative uncertainty was below 0.2%. Moreover, Monte Carlo simulation was undertaken using MCNP4C code and the relative difference of 1.9% was observed compared to the experiment. As a result the chamber presented a satisfactory performance in all evaluated tests in Gamma radiation field of 60Co.

Teaching about natural background radiation

Ambient gamma dose rates in air were measured at different locations (indoors and outdoors) to demonstrate the ubiquitous nature of natural background radiation in the environment and to show that levels vary from one location to another, depending on the underlying geology. The effect of a lead shield on a gamma radiation field was also demonstrated to emphasize the important role of shielding in radiation protection. The measurements were carried out with a Geiger–Muller (GM)-based dosimeter and a NaI scintillation gamma-ray spectrometer, which are normally available in physics laboratories. Radioactivity in household materials was demonstrated using a gas mantle as an example.

Determination of alpha activity in organic solvents using CR-39

Solid State Nuclear Track Detector (SSNTD) like CR-39 offers a unique opportunity to measure alpha radiations in a complex matrix like high level nuclear waste due to its sensitivity to only alpha radiations in the presence of intense beta–gamma radiation field. There is however a concern about the lower sensitivity of SSNTD when the radiation source is present in solution vis-à-vis solid medium. The sensitivity of CR-39 toward detection of alpha particles homogenously distributed in n-hexane, n-dodecane and n-octanol has been investigated and was found to be better than that obtained in 3M HNO3.

Effects of different types of nuclear radiations on optically stimulated luminescence

This study aims to investigate the effects of different nuclear radiation fields on an optically stimulated luminescence (OSL) dosimeter using Al_2O_3:C material. The Al_2O_3:C material was exposed to alpha- and beta-particles and gamma-photons, and the luminescence signals were measured by stimulation with a blue light emitting diode. It is concluded that the OSL technique is suitable for obtaining an adequate blue light stimulated luminescence signal in alpha, beta, and gamma radiation fields, and if the source activity was low, the statistical distributions were large.