The Chromosome Network for biodosimetry in Japan

The Chromosome Network in Japan was established just after the critical Tokai-mura accident in 2001 with the purposes of (1) integrating work to be ready for a large-scale radiation accident, (2) establishing standard methods for cytogenetic dose estimation, (3) creating a standard dose response curve in Japan, (4) preparing a training program for cytogenetic dose estimation and (5) training successors for biodosimetry work. In order to perform the cytogenetic dose estimation according to the same criteria, an inter-laboratory comparison is being experimentally carried out among the laboratories in the Chromosome Network.     

Franco-Russian comparison of mixed neutron and gamma radiation field dosimeters at the Silène reactor

This paper gives the results of dosimetry measurements carried out in the Silène reactor at Valduc (France) with neutron and photon dosimeters in mixed neutron and gamma radiation fields, in the frame of a Franco-Russian comparison of dosimeters. Neutron dosimetry was supplied by passive semiconductors, activation detectors and nuclear track detectors. For photon dosimetry, thermoluminescent and passive semiconductor detectors were used. The experiments were located at 3 m from the reactor core, in free air and also at the front and back of a tissue-equivalent phantom. The pulse operating mode of the reactor was used to simulate a criticality accident with solid fissile material, while the free evolution mode simulated a criticality accident in a fissile solution. The photon absorbed dose showed a slight increase on entering the phantom compared to measurements in free air, probably due to backscattering by the phantom. At the rear of the phantom, the neutron kerma was four times lower than on the front, whereas the photon dose was only two times lower. The heterogeneity of dose inside the phantom was far greater for neutrons than for photons.     

燃料操作事故辐射影响定量分析

以红沿河核电厂为对象，开展了CPR1000燃料操作事故放射性核素的来源、迁移途径、释放方式研究，构建了燃料存储室以及外环境的源项计算模型。在此基础上，定量地论证了该事故所产生的辐射影响，结果表明:基于前0.5%概率水平的厂址气象条件，得到非居住区边界以及规划限制区外边界16个标准方位的公众剂量均可满足GB 6249-2011限值要求，且尚存一定裕量。通过关键参数的敏感性分析，进一步识别出了剂量最大方位、主导核素、关键时段，论证了事故分析截断时间取12 h的合理性、燃料操作起始时间取100 h的必要性。同时，进一步研究了水洗深度及正常通风隔离时间对公众剂量的影响规律，公众剂量随水洗深度增加呈指数降低趋势，随正常通风隔离延迟时间变长而快速增加，相关研究可为各核电厂设计决策提供支持。     

Investigations of touchscreen glasses from mobile phones for retrospective and accident dosimetry

Touchscreen glasses of mobile phones are sensitive to ionizing radiation and have the potential of usage as an emergency dosimeter for retrospective dosimetry for the purpose of triage after a radiological accident or attack. In this study the TL glow curves and dosimetric properties of touchscreen glasses were studied in detail, such as intrinsic background dose, dose response, reproducibility, optical stability and long-term stability of the TL signal.Preliminary results are additionally presented to minimize the intrinsic background dose by mechanically removing the surface layer of the glass samples. Additionally chemical element analyses of the touchscreen glass samples were carried out to investigate the difference between glass samples which show a TL signal and samples which show neither an intrinsic zero dose signal nor a radiation induced TL signal.An irradiation trial using glass samples stored in the dark demonstrated a successful dose recovery. However, when applying a realistic, external light exposure scenario, dose underestimation was observed, even though samples were pre-bleached prior to measurement. More investigations have to be carried out in the future to solve the challenge of the low optical stability of the TL signal, if touchscreen glasses are to be used as a reliable emergency dosimeter.     

Limits of retrospective accident dosimetry by EPR and TL with natural materials

The radiation response of natural materials and domestic articles was investigated by EPR and TL to select suitable materials for retrospective dose assessment in accident dosimetry. The thermal stability and the influence of UV-exposure to the radiation-induced EPR centres were investigated. Based on a required precision of ±20% for dosimetry the lower limits of applicability of the materials were determined. The lowest dosimetry limits of 0.5 Gy were found using sugar, boiler scale and egg shells by EPR and 0.3 Gy by using TL with boiler scale. A list of materials found not to be applicable for retrospective radiation accident EPR dosimetry is also given.     

OSL and TL retrospective dosimetry with a fluorapatite glass-ceramic used for dental restorations

Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL) properties of a fluorapatite glass-ceramic have been investigated, with a view to developing a dose assessment technique for medical triage following unplanned exposures of individuals to ionizing radiation. The ceramic is an innovative material used in dental prostheses and restorations. It is strongly sensitive to radiation and the intensity of both the OSL and TL signals are proportional to the absorbed radiation dose. We focused on the optimization of the measuring procedure and investigated characteristics such as reproducibility, fading, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. The dental ceramic exhibited very good reproducibility (<5% at 2σ level) when measured and a linear dose response for a wide range of doses (50 mGy–20 Gy). The MDD values for the samples investigated were ∼5 mGy. The material is not tissue equivalent and the OSL and TL signals are strongly dependent on incident photon energy. Both the luminescence signals exhibited significant fading during the first few hours after irradiation. Its rate was dependent on the parameters of measurement. The results indicate that the material can be used for the purposes of accident dosimetry, however, the fading and photon energy response have to be properly corrected for a reliable dose assessment.     

Monitoring environmental dose rate using Risø TL/OSL readers with built-in sources: recommendations for users

Measurements were carried out to quantify the dose rate delivered to samples due to leakage and cross-talk of the beta and alpha sources in various models of Risø TL/OSL readers; additionally the offset time was calculated. Highly sensitive -Al₂O₃:C and CaF₂:Mn dosemeters were used to investigate the impact on low environmental dose-rate assessment. The effect is shown to depend on the energy response of the detectors, the source strength and the reader design of the equipment. It was tested, if the scattered radiation of the closed source can be utilised to extend the dose range downwards to lower doses, as the dose rates of the built-in sources of Risø TL/OSL readers often exceed the practical values for ultra-low-dose measurements. The results and their consequences for environmental dose-rate assessment are discussed.     

Radon, thoron and their progeny levels in some dwellings of northern Haryana, India using SSNTDs

Radon pollution is an important global problem of radiation hygiene. Radon and its progeny are the major contributors in the radiation dose received by general population of the world. Keeping this in mind the environmental monitoring of radon, thoron and their progeny in some dwellings of northern part of Haryana state of India has been carried out. The radon-thoron twin dosimeter cups were used for the study. The aim of the study is the possible health risk assessment in the dwellings under consideration.     

Difficulties in the dose estimate of workers originated from radon and radon progeny in a manganese mine

The regulation of radon concentration at workplaces has gained an accentuated importance in all countries. Nevertheless, at this time there is no globally accepted workplace protocol that sets out safe radon concentration values.In this study the radon concentration measured during the working hours and the equilibrium factor, which are necessary for the exact estimation of the radiation dose originating from radon and effecting manganese miners are determined in a Hungarian manganese mine. In order to determine the exact committed effective dose, workers wore track-etched radon.The annual average radon concentration measured at the different points in the mine that was investigated may vary by ±30% relative to the average of the total of the measurement points. The influence of the measurement period is even more significant as the difference related to the annual average may be ±30% with a measurement period of 6 months. The radon concentration level measured during working hours was approximately half of the average measured during the whole period. The measured equilibrium factor was 50% greater than the value given in literature. Disregarding any of these factors may lead to significant errors for the estimation of dose to workers.The average value of the estimated effective radiation dose was 3.7 mSv year⁻¹ based on the personal radon dosimeters.     

Electron paramagnetic resonance radiation dosimetry in fingernails

There is now an increased need for accident dosimetry due to the increased risk of significant exposure to ionizing radiation from terrorism or accidents. In such scenarios, dose measurements should be made in individuals rapidly and with sufficient accuracy to enable effective triage. Electron paramagnetic resonance (EPR) is a physical method of high potential for meeting this need, providing direct measurements of the radiation-induced radicals, which are unambiguous signatures of exposure to ionizing radiation. For individual retrospective dosimetry, EPR in tooth enamel is a proven and effective technique when isolated teeth can be obtained. There are some promising developments that may make these measurements feasible without the need to remove the teeth, but their field applicability remains to be demonstrated. However, currently it is difficult under emergency conditions to obtain tooth enamel in sufficient amounts for accurate dose measurements. Since fingernails are much easier to sample, they can be used in potentially exposed populations to determine if they were exposed to life-threatening radiation doses. Unfortunately, only a few studies have been carried out on EPR radiation-induced signals in fingernails, and, while there are some promising aspects, the reported results were generally inconclusive. In this present paper, we report the results of a systematic investigation of the potential use of fingernails as retrospective radiation dosimeters.     

In-flight radiation measurements on STS-60

A joint investigation between the United States and Russia to study the radiation environment inside the Space Shuttle flight STS-60 was carried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measurement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy spectra and angular distribution of trapped protons. In general, there is good agreement between the U.S. and Russian measurements. The AP8 Min trapped proton model predicts an average of 1.8 times the measured absorbed dose. The average quality factor determined from measured lineal energy, y, spectra using a tissue equivalent proportional counter (TEPC), is in good agreement with that derived from the high temperature peak in the 6LiF thermoluminescent detectors (TLDs). The radiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 microSv/day. The absorbed dose rates measured using a tissue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 microGy/day for trapped particles and galactic cosmic rays, respectively. The combined dose rate of 298.5 +/- 0.82 microGy/day is about a factor of 1.4 higher than that measured using TLDs. The westward longitude drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 +/- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate variations by factors of up to 2 at the location of the TEPC.     

Analysis of Phototherapy Effectiveness Using Thermography

A thermographic study of low-intensity phototherapeutic effects on the human body in situ was carried out. The feature of the work was the measurement of the dynamics of surface temperature changes in a bio-object for 40 min after the cessation of irradiation. The relaxation character of the temperature behavior with quasi-oscillating phenomena during the selected observation period has been established. An explanation of the observed phenomena with the involvement of literature data is proposed. It is shown that 15-min irradiation at a radiation intensity of 14mWcm^?2 is optimal for phototherapy at a wavelength of 640 nm. A conclusion was made about the possibility of considering changes in the local temperature of a bio-object as a correlated parameter to determine the optimal dose of radiation during phototherapy.

     

Cosmic rays and dosimetry at aviation altitudes

Recent concerns regarding the effects of the cosmic radiation field at aircraft altitudes on aircrew have resulted in a renewed interest in detailed measurements of the neutral and charged particle components in the atmosphere. CR-39 nuclear track detectors have been employed on a number of subsonic and supersonic aircraft to measure charge spectra and LET spectra at aircraft altitudes. These detectors are ideal for long term exposures required for these studies and their passive nature makes them suitable for an environment where interference with flight instrumentation could be a problem. We report here on measurements and analysis of short range tracks which were produced by high LET particles generated mainly by neutron interactions at aviation altitudes. In order to test the overall validity of the technique measurements were also carried out at the CERN-CEC field which simulates the radiation field at aviation altitudes and good agreement was found with dose values obtained using mainly heavy ion calibration.     

Optically stimulated luminescence (OSL) of dental enamel for retrospective assessment of radiation exposure

This paper briefly reviews the optically stimulated luminescence (OSL) properties of dental enamel and discusses the potential and challenges of OSL for filling the technology gap in biodosimetry required for medical triage following a radiological/nuclear accident or terrorist event. The OSL technique uses light to stimulate a radiation-induced luminescence signal from materials previously exposed to ionizing radiation. This luminescence originates from radiation-induced defects in insulating crystals and is proportional to the absorbed dose of ionizing radiation. In our research conducted to date, we focused on fundamental investigations of the OSL properties of dental enamel using extracted teeth and tabletop OSL readers. The objective was to obtain information to support the development of the necessary instrumentation for retrospective dosimetry using dental enamel in laboratory, or for in situ and non-invasive accident dosimetry using dental enamel in emergency triage. An OSL signal from human dental enamel was detected using blue, green, or IR stimulation. Blue/green stimulation associated with UV emission detection seems to be the most appropriate combination in the sense that there is no signal from un-irradiated samples and the shape of the OSL decay is clear. Improvements in the minimum detection level were achieved by incorporating an ellipsoidal mirror in the OSL system to maximize light collection. Other possibilities to improve the sensitivity and research steps necessary to establish the feasibility of the technique for retrospective assessment of radiation exposure are also discussed.     

Angular Gamma Dose Rate Distribution at the Surface of Injected Ducted Concrete Shield

The shielding problems that arise due to the irregular penetrations such as neutral beam injection ducts should be treated carefully to aid in the shield design. The present work was undertaken to describe the effects arising due to radiation streaming through the neutral beam injector ducts (NBID) on the angular distribution of the total gamma ray doses at the outer surface of illmenite concrete shield (? = 4.6g/cm³). The shield is pierced with NBID of different diameters and lengths. The measurements were performed using a collimated beam of both gamma rays and neutrons emitted from one of the horizontal channels of the ET-RR-1 reactor. The measurements were carried out using ⁷LiF teflon thermoliminescent dosimeters. Generally the obtained data reveal that the presence of the total dose increase at the centerline of NBID and which in turn tends to decrease with the increase of scattered angle. An empirical formula describing the differential dose rate ratio is predicted. The experimental data obtained reveal good agreement with the calculated ones.     

Protocol for emergency EPR dosimetry in fingernails

There is an increased need for after-the-fact dosimetry because of the high risk of radiation exposures due to terrorism or accidents. In case of such an event, a method is needed to make measurements of dose in a large number of individuals rapidly and with sufficient accuracy to facilitate effective medical triage. Dosimetry based on EPR measurements of fingernails potentially could be an effective tool for this purpose. This paper presents the first operational protocols for EPR fingernail dosimetry, including guidelines for collection and storage of samples, parameters for EPR measurements, and the method of dose assessment. In a blinded test of this protocol application was carried out on nails freshly sampled and irradiated to 4 and 20 Gy; this protocol gave dose estimates with an error of less than 30%.     

Development of high-radiation-sensitive polymer gel for magnetic resonance imaging in three-dimensional dosimetry

We developed a high radiation sensitive polymer gel by modifying the amounts of the gel components and the temperature for the gel preparation. We evaluated its relaxation time linearity against dose and compared the measured dose distribution with the calculated one. For the relaxation time-dose linearity, irradiations were carried out with a linear accelerator using 6 MV photons and doses ranging from 0-5.0 Gy. The relationship between dose and R(2) value (reciprocal of T(2) relaxation time) was measured and it had good linearity over a wide range (0.3-5 Gy). The measured dose distributions were in good agreement with calculated ones. Since the present gel has higher sensitivity and it is synthesized more easily at lower cost than conventional polymer gels, we expect to see improved three-dimensional (3D) dosimetry using it.     

控制器组件γ瞬时辐射效应研究

瞬时电离辐射在电子器件内部形成的光电流可引起器件输出扰动,导致电路中部分器件受电源、输入信号及自身产生光电流扰动的多重影响,而单独对器件进行试验无法反映瞬时辐射输出扰动在电子组件系统中的传递影响。为此对由DC/DC、稳压器、单片机CPU,FPGA等组成的控制器组件在2.8105~1.7107 Gy(Si)/s的范围内开展了瞬时辐射效应的试验研究。试验中对组件功能和器件参数的测试结果表明,在较小的瞬时剂量率下,部分器件输出受到影响,但组件功能正常;较大剂量率时,所有器件均受影响,且组件功能中断。同时观测到瞬时辐射形成的扰动信号在器件间传输现象。     

Optical properties of some modified plant compound after 662 keV gamma radiation

Plant-isolated compounds, Osthol [7-methoxy-8-(3-methylbut-2-enyl) coumarin], were subjected to modification in the isopentenyl side chain to get an aldehyde of 2-methyl-4 (7-methoxy-2-oxo-2H-chromen-8-yl)-but-2-en-1-al. This modified compound was exposed to γ-radiation produced by ¹³⁷Cs source at room temperature. Pre- and post-irradiation study was carried out by ultraviolet–visible spectroscopy. The compound shows a sharp absorption peak at 322?nm. This observed absorption band decreases with irradiation up to a certain dose and then increases with a further increase in the radiation dose. This compound exhibits almost a linear response up to 7?Gy. From the optical data analysis, this compound follows indirect allowed transition and the optical gap was found around 3.58?eV. The systematic decrease in the band gap was found with an increase in the radiation dose. Urbach energy is also found to decrease with radiation. This parameter gives a clear indication of the defects and free radical created in the system after irradiation. The present features shown by this compound may be exploited as sensitive dosimeter in 0–7?Gy γ-radiation environment.     

Electron-Beam-Induced Modifications in High-Density Polyethylene

Post-irradiation studies have been carried out to elucidate the effects of electron beam irradiation on the structural, optical, dielectric, and thermal properties of high-density polyethylene (HDPE) films. The experimental results showed that both the optical band gap and activation energy of HDPE films decreases with an increase in the doses of electron radiation. The electrical measurements showed that dielectric constant and the ac conductivity of HDPE increases with an increase in the dose of electron radiation. The thermal analysis carried out using DSC and TGA revealed that the melting temperature, degree of crystallinity, and thermal stability of the HDPE films increased, obviously, due to the predominant cross-linking reaction following high doses of electron irradiation.