Gamma-ray Radiation Dose Research Articles

Radiation-induced attenuation self-compensating effect in super-fluorescent fiber source

The compact super-fluorescent fiber source (SFS) output spectra variations at different pump currents and under different dose of gamma-ray radiation were measured and compared respectively. The radiation-induced attenuation (RIA) self-compensating effect in SFS based on photo-bleaching was found and the general mathematic model of SFS output spectra variations was made. The radiation-induced background attenuation (RIBA) at the pump wavelength was identified to be the main cause of the total output power and spectra variations and the variations can then be compensated by active control of the pump power to enhance the self-compensating effect. With closed-loop feedback control of pump current, double-pass backward (DPB) configuration and spectrum re-shaping technology, an SFS prototype was made and tested. The mean-wavelength stability of about 87.4 ppm and output power instability of less than 5% were achieved under up to 200 krad (Si) gamma-ray irradiation.

Structural Changes of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma Ray Radiation Doses

The effect of (60)Co gamma rays irradiation on the polymetallayne [-Pt(PBu(3))-C≡C-C(6)H(4)-C(6)H(4)-C≡C-](n) (Pt-DEBP) of defined chain length corresponding to 10 repeat units, has been studied in detail. The UV-vis absorption spectra of Pt-DEBP have been recorded in solution upon exposure of the polymetallayne at increasing radiation doses in the range up to 90 Gy, with special care to the features related to low doses. Complex modifications of the chemical structure of Pt-DEBP could be accessed through NMR, FTIR, GPC, and XPS characterizations, which support the attack of Cl and H radicals coming from the radiolysis of the solvent, CHCl(3), to the triple C≡C bonds of the backbone, leading to the formation of chlorinated double and single C-C bonds, with a concomitant increase of the molecular weight due to a recombinant effect of oligomer fragments upon irradiation. The presence of vinyl and single chlorinated moieties has been sustained from the simulation of the UV-vis spectra based on theoretical calculations.

Optical Behavior of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma-Ray Radiation Doses

The effect of (60)Co γ irradiation on the absorption and emission spectra of the organometallic polymer [-Pt(PBu(3))(2)-C≡C-C(6)H(4)-C(6)H(4)-C≡C-](n) (Pt-DEBP) in chloroform and toluene solutions for dosimetry applications has been studied. The system Pt-DEBP/chloroform can be used for dosimetric applications in two different ways: (i) monitoring of absorption spectra changes for higher doses (higher than 1 Gy), and (ii) monitoring of emission spectra changes for low doses (below 1 Gy). The response of the polymer solution to γ ray doses has been interpreted with the aid of theoretical studies based on time dependent density functional theory (TD-DFT) calculations on the absorption bands of a model complex and of the possible fragments coming from the degradation of the polymer backbone. It has been proposed that the observed changes are promoted by the attack of radicals, from the radiolysis of the solvent, on the polymer triple bonds.

A facile and convenient fluorescence detection of gamma-ray radiation based on the aggregation-induced emission

A facile and convenient fluorescence detection of gamma-ray radiation is reported. This is based on the ensemble of silole 1 and polymer 2, by taking advantages of AIE (aggregation-induced emission) behavior of silole compounds and the fact that polymers with –SO2groups in the main chain can be degraded upon gamma-ray radiation. The fluorescence intensity of the ensemble of silole 1 and polymer 2 decreases gradually after exposure to increasing dose of gamma-ray radiation. The detection of gamma-ray radiation with silole 1 and polymer 2 can be performed at ambient conditions and gamma-ray radiation as low as 0.13 kGy dose can be successfully detected.

Radiation Induced Change in Defect Density in ${\hbox {HfO}}_{2}$-Based MIM Capacitors

The effect of radiation-introduced defects on the behaviour of HfO2-based metal-insulator-metal (MIM) capacitors as a function of gamma-ray radiation dose from 10 to 1000 krad are reported. Half the capacitors studied showed no degradation after exposure to 1000 krad from a 60Co source, whilst the remaining half showed no change to parameters, such as barrier height and dielectric constant. For the good devices, the I-V characteristics are controlled by Poole-Frenkel model, at a corresponding interface trap energy of 0.39 ~ 0.46 eV before radiation and 0.37 ~ 0.44 eV after 1000 krad. The failed devices show an substantial increase in the trap density from the as fabricated level of 1019 cm-3 to in excess of 1020 cm-3, in contrast to the good devices which show almost no change. We relate this change in defect density to the failure of devices by means of a percolation model, with a trap separation of around 2 nm.

Conducting polymer/silicon heterojunction diode for gamma radiation detection.

In this work, alternative heterojunction devices to be used for gamma-radiation detection are presented. The high quality silicon/polyaniline heterostructures use polyaniline thin films as an active part of the device structure. Polyaniline thin films 40 nm thick were deposited onto silicon substrates (n-type, <100>, 1 ohm x cm) using the spin-coating technique from soluble polyaniline. The devices present excellent electrical characteristics, with a rectification ratio of 60,000 at +/- 1.0 V, reverse currents in the order of a few nA and ideality factor approximately 2. These electrical characteristics indicate great potential for their use in sensor applications. The heterojunction diode is very sensitive to gamma radiation in the dose range of 0-7000 Gy, presenting a linear response in the forward and reverse bias. The excellent electrical characteristics, together with the linear response with the dose strongly suggest the application of this device for spectrometry or dosimetry of low and high doses of gamma ray radiation.

Radiation effects of carbon ions and gamma ray on UDMA based dental resin.

The radiation effects on the mechanical and physical properties of photo-polymerized UDMA resin without filler was investigated by various mechanical tests and spectroscopic measurements. The radiation sources were carbon ion (12C ion) and gamma ray (gamma-ray). With 640 Gy of 12C ion radiation, Vickers hardness increased by about 40%, the degree of abrasion decreased by 30%, and the flexural strength increased by 20%. With the same dose of gamma-ray radiation, only Vickers hardness increased by 19%. The spectra taken by the Fourier Transform Infrared Spectrometer (FT-IR), Raman spectroscopy, and Fluorescence spectrophotometer showed little change in the peak configuration and background intensities. The relative degree of conversion (DC) of carbon double bonds by radiation to the state of non-radiated samples were estimated by FT-IR. Spectroscopic results were indicative for the formation of cross-linking between carbon chains. Cross-linking of carbon molecules induced by radiation might be one of the reasons for the improved mechanical properties of UDMA resin.

Channel-length impact on radiation-induced threshold-voltage shift in N-MOSFET devices at low gamma ray radiation doses

SiO/sub 2/ gate dielectric and Si/SiO/sub 2/ interface are two important components which will shape the future of the MOSFETs and integrated circuits (IC's) technologies for ionizing radiation environment applications. This study discuss their size effects on irradiated NMOS device response. N-channel MOSFET's of different gate size were first irradiated with /sup 60/Co gamma rays source at several total doses (low doses). Then, they were investigated by using both voltage- and frequency-charge pumping (CP) methods. On one hand, all transistors reveal two radiation-induced oxide charge traps formation mechanisms, caused by low radiation total doses. Initially, there is a build-up of positive charge in the oxide layer, followed later by diminution of net positive charge (turn around effect), while the interface traps exhibit a linear increase with radiation doses. On the other hand, the total dose response is shown to depend on gate length of NMOS device.

Radioactivity in zircon and building tiles.

Zircon (ZrSiO4) is commonly used in the manufacture of glazed tiles. In this study we found high concentrations of the radionuclides 226Ra, 232Th, 40K in zircon sand. The average radium equivalent (A(Ra) + 1.26 A(Th) + 0.086 A(k)) in zircon sand is 17,500 Bq kg(-1), which is 106 times as much as that in ordinary building materials. The external radiation (gamma + beta) dose rates in air at 5 cm from the surface of piles of zircon sand sacks range from 1.1 to 4.9 x 10(-2) mGy h(-1) with an average of 2.1 x 10(-2) mGy h(-1). Although no elevated gamma-ray radiation or radon exhalation rate was detected in rooms decorated with glazed tiles, which is characteristic of combined alpha, beta and gamma emitting thin materials, the average gamma-ray radiation dose rate at the surface of the tile stacks in shops is 1.5 times as much as the indoor background level. The average area density of total beta emitting radionuclides in glazed floor tiles and glazed wall tiles is 0.30 Bq cm(-2) and 0.28 Bq cm(-2), respectively. It was estimated that the average beta dose rates in tissue at a depth 7 mg cm(-2) with a distance 20-100 cm from the floor tiles were 3.2 to 0.9 x 10(-7) Gy h(-1). The study indicates that the beta-rays from glazed tiles might be one of the main factors leading to an increase in ionizing radiation received by the general public. Workers in glazed tile manufacturing factories and in tile shops or stores may be exposed to elevated levels of both beta-rays and gamma-rays from zircon sand or glazed tile stacks. No elevated radiation from unglazed tiles was detected.

Application of FELTRAN to NEACRP TN12 shipping cask benchmark

The finite element technique has received attention as a method of solving the Boltzmann equation in one, two and three spatial dimensions. In particular much work has been published concerning the geometrical flexibility, speed and accuracy of the method. British Nuclear Fuels plc and Imperial College have collaborated in developing the finite element code FELTRAN to near production code status. FELTRAN solves the even parity form of the Boltzmann equation using a functional approach. The solution is found in one or two spatial dimensions using various orders of finite elements to specify the problem geometry. The angular dependence of the even parity flux is expressed using spherical harmonics. FELTRAN has been interfaced to ANISN formatted nuclear data libraries such as CASK and BUGLE. Anisotropic scattering may be specified to any order. Methods have been incorporated within the code to analyse systems with voids. FELTRAN is currently undergoing further development as part of a BNFL sponsored MSc research programme at the University of Salford. The purpose of this paper is to consider the application of FELTRAN to a practical shield design problem. The OECD have adopted a benchmark experiment to measure the neutron and gamma ray radiation dose rates around a spent fuel transport flask. As part of an international collaboration the physical details of the flask design and contents have been provided to the nuclear industry. The objective is to perform an international comparison of the methods used in the analysis of cask shielding. BNFL is one of the companies involved, using the well established codes RANKERN and MCBEND. The FELTRAN calculations are performed using the same source and geometry data and equivalent angular flux expansions as for these two codes. FELTRAN is then compared with experimental and calculated results.

Nuclear radiation test of a D flip-flop IC using a single-board microcomputer

A description is presented of the design of a microcomputer-controlled electronic circuit and its use in evaluating the effects of nuclear radiation on a 4013 CMOS D flip-flop (FF) integrated circuit (IC). The IC undergoing testing is attached to a device-under-test board, which is enclosed in a metal container. The container is then lowered to the cobalt 60 radiation source located at the bottom of a 15-ft-deep pool filled with water. The gamma-ray radiation test setup is schematically shown. The in-source test board containing the D-FF IC is attached to an 8085-based single-board microcomputer, SDK-85, by a 30-ft multiconductor cable. Doses of gamma-ray radiation from the cobalt 60 are applied in steps at increasing quantities until the D-FF IC, which is tested between doses, begins to malfunction. The leakage current and the propagation delay time are measured between doses. An 8085 assembly language program is used for the functional test of the IC. The software design and the radiation testing procedure are discussed in detail.

Circuit design for nuclear radiation test of CMOS multiplier chips

The design of a microprocessor-based electronic circuit to be used in testing the effects of nuclear radiation on a CMOS 8×8 multiplier chips is described. The multiplier chip undergoing testing is attached to a DUT (device under test) board which is enclosed in a metal container. The container is then lowered to the cobalt 60 radiation source located at the bottom of a 15-ft deep pool. The in-source test board containing the multiplier chip is attached to an Intel 8085-based, single-board microcomputer (SDK-85) by a 30-ft multiconductor diode. Doses of gamma-ray radiation from cobalt 60 are applied in steps at increasing quantities until the multipliers chip, which is tested between doses, begins to malfunction. An 8085 assembly language program is used for functional testing of the multiplier. The leakage current and the propagation delay time are also measured between doses.

Shielding Calculations for Neutrons from Enhanced Radiation Weapons by Monte Carlo Theory

The Monte Carlo theory provides a powerful tool for solving three-dimensional neutron shielding problems. Special variance reducing methods must be applied if the detector regions are very remote from the source region. Recently, an idea for a new scoring method was proposed to reduce an estimator for large distances between flux point and collision point to the standard flux point estimator. A Monte Carlo code based on this method was developed. This code was applied to the calculation of neutron doses, neutron spectra, and neutron fluxes produced by the detonation of an enhanced radiation weapon. The results may be considered as a test of the efficiency and as a first application of a new Monte Carlo method. The radiation doses reported in this Note only refer to neutrons. The gamma-ray radiation doses due to neutron capture reactions are not considered.

Environmental Radiation at the EBR-II Site

The present environmental radiation state of the EBR-II site has been explored through application of new and highly sensitive methods which have resolved the environmental gamma and meson components at this highly relevant LMFBR site. The external gamma-ray radiation dose rate in the immediate vicinity of EBR-II (for gamma rays of energy in excess of 220 keV) was observed to be about 6 μrad/hr. The cosmic-ray meson component contributes an additional dose rate of about 4.5 μrad/hr. These two components result in an annual external dose to man of approximately 92 mrads. Although analysis of the gamma-ray spectra and soil samples reveals that the gamma-ray component is overwhelmingly derived from naturally occurring isotopes, statistically significant amounts of 137Cs and 125Sb (fission products). were observed in soil samples collected during this site survey. In addition, sizeable variations in the observed concentrations of 125Sb, 137Cs, 238Pu, and 239Pu of these EBR-II soil samples would appear to imply a non-uniform deposition pattern. However, the observed non-uniformity could be due to either local releases of fission products or drifting of surface soil containing fallout products. While fallout is certainly a significant contribution to the measured deposition, observed patterns and correlations qualitatively suggest that very low level releases could possibly have occurred at the EBR-II site some time in the past. Quantitative conclusions cannot possibly be based upon the very limited data available from the present site survey.