Environmental Gamma Rays Research Articles

Calculation of total efficiencies of extended samples for HPGe detectors

Calculation of coincidence summing correction factors in gamma-ray spectrometry can be carried out by making use of full-energy-peak and total efficiencies for a given sample geometry and detector setup. In the case of extended samples, the contribution of gamma-rays that scatter in the sample itself to the total efficiency needs to be taken into account. A method is described for calculating this contribution based on calibration measurements with point sources positioned on the detector housing. The approach is aimed at environmental gamma-ray spectrometry analysis of cylindrical samples on p-type HPGe detectors and is verified against full Monte Carlo calculations of total efficiencies with the GEANT code.

Cosmic ray effects in microcalorimeter arrays

We have identified signals resulting from cosmic rays and environmental gamma rays depositing energy in the pixels and in the silicon frame of the Astro-E2/X-Ray Spectrometer microcalorimeter array. Coincidences between pixels and between the array and an anti-coincidence detector determined the nature of the events. Pulse shapes and amplitudes from the cosmic ray events helped refine the thermal model of the array chip. We discuss how future arrays can be optimized either for the greatest background rejection or for the highest source count rates.

Evaluation of Accuracy of Response Matrix Method for Environmental Gamma Ray Analysis

Evaluation of Accuracy of Response Matrix Method for Environmental Gamma Ray Analysis

Diagonal Elements Fitting Technique to Improve Response Matrixes for Environmental Gamma Ray Spectrum Unfolding.

Diagonal Elements Fitting Technique to Improve Response Matrixes for Environmental Gamma Ray Spectrum Unfolding.

岡山県環境保健センターにおける放射能測定への取り組み

We evaluated the environment around Ningyotoge in the northern part of Okayama Prefecture. (I) Measurement with TLD. 1) Environmental gamma ray measurement results were evaluated by TLD at the time of confirming an investigation using a continuous gamma ray monitor. Doses during that time span for passing persons and individuals in the area were lower than 89nGy/h. 2) We observed Fading for TLD. The result was that the Fading revision coefficient for the Tenno district in Ningyotoge between October 10, 1997 to December 18, 1997 was 1.02. That for the premises of the Okayama Prefectural Institute for Environmental Science and Public Health was 1.05. The Tenno district in Ningyotoge during the period between June 29, 1998 to October 6, 1998 was 1.04. 3) A relationship between the height from the ground and gamma ray dose was found. A straight line was shown by both logarithm graphs. (II) Wastewater processing. We evaluated radioactive wastewater. When considering the processing of wastewater that flows into rivers, a discharge of zero release is desirable. We evaluated the BOD, COD, etc, as well as the radioactive materials that are processed by microbes such as Bacillus and Arthrobacter.

Development of a real-time radon monitoring system for simultaneous measurements in multiple sites

A real-time radon monitoring system that can simultaneously measure radon concentrations in multiple sites was developed and tested. The system consists of maximum of four radon detectors, optical fiber cables and a data acquisition personal computer. The radon detector uses a plastic scintillation counter that collects radon daughters in the chamber electrostatically. The applied voltage on the photocathode for the photomultiplier tube (PMT) acts as an electrode for radon daughters. The thickness of the plastic scintillator was thin, 50 /spl mu/m, so as to minimize the background counts due to the environmental gamma rays or beta particles. The energy discriminated signals from the radon detectors are fed to the data acquisition personal computer via optical fiber cables. The system made it possible to measure the radon concentrations in multiple sites simultaneously.

Calculation of the effective dose and its variation from environmental gamma ray sources.

Effective dose, an indicator of the stochastic effect of radiation, has been widely used in dose evaluation in the environment. Though conversion factors have been used to obtain E from the air kerma or air absorbed dose, the variation of the conversion factors due to the change of exposure conditions has not been sufficiently investigated. This report documents an investigation of the variation of the effective dose per air kerma for environmental gamma rays depending on the exposure conditions using anthropomorphic phantoms and Monte Carlo calculations, taking into account the precise angular and energy distributions of the environmental gamma rays incident on the human body. As causes of the variation, posture of human bodies, biases of environmental source distributions, and body size were considered. The variation of effective dose in a prone position compared with that in a standing position was found to be within 30%. The bias of environmental sources causes the effective dose per air kerma to vary by 20% at maximum, but in some cases for low-energy gamma rays the variation was found to be up to 40% due to the change in the energy spectrum. The effective dose for a new born infant was estimated to be higher than that for an adult by a maximum of 80-90% for low-energy gamma rays from anthropogenic sources because of a lower shielding effect of the smaller body. The variation of the effective dose equivalent shows a similar tendency to the effective dose. Consequently, this study made it possible to estimate the uncertainties of effective dose and effective dose equivalent evaluated from air kerma or absorbed dose in air using the standard available conversion factors.

The European Capability for Environmental Airborne Gamma Ray Spectrometry

The past few years have seen significant development in the availability of airborne gamma spectrometry (AGS) systems in Europe, and awareness of their potential contribution in support of off-site emergency management. The high sampling rates, mobility, and fields of view of AGS lead to the possibility of conducting total environmental surveys of areas affected by an accidental release of radioactivity. Recent developments of systems suitable for rapid deployment from fixed and rotary-wing aircraft, and of rapid data processing and presentation systems, have greatly enhanced the capability of AGS to deliver results on emergency timescales. The need for greater coordination of AGS capabilities and methods at an international level has been recognised in Europe. This presentation summarises the current European capability for AGS, giving brief details of the types of systems available, their mobilisation timescales, calibration status and data produced. The extent to which the systems are currently integrated into emergency preparations, and their possible roles will be discussed. There is a considerable European capability for post-accident deposition mapping using AGS. Further needs in support of emergency response are outlined.

97/00403 Accounting for spatial variability and fileds of view in environmental gamma ray spectrometry

97/00403 Accounting for spatial variability and fileds of view in environmental gamma ray spectrometry

車を利用した北海道における環境γ線測定

An extensive car-borne survey was made for the evaluation of dose rates due to environmental gamma rays in Hokkaido during the period from May 1994 to January 1996. The dose-rate levels in Hokkaido were estimated from survey results measured with a portable pure germanium spectrometer installed in a car. The car speed was kept between 30 and 60km h-1 (car-borne measurements). In addition to the car-borne measurements, another mode of measurement (spot measurements) was also made at 100 specific places selected in advance. The measurement times were set at 900s real time both for car-borne measurements and spot measurements. The survey routes covered almost all districts along the main roads in Hokkaido. From the car-borne measurements, absorbed dose rates in air due to gamma rays were found to be distributed from 14.9 to 116.5nGy h-1. The arithmetic mean dose rate and the standard deviation were calculated to be 42.1±16.2nGy h-1. The variation of total absorbed dose rate was found to be originated mainly by the variation of contribution from the Th-232 series nuclides.

Accounting for spatial variability and fields of view in environmental gamma ray spectrometry

Spatial variability is an important feature in many environmental studies, which influences comparison estimates of environmental radioactivity from soil samples and in-situ or airborne γ-ray spectrometry. Comparisons between ground based and airborne gamma ray spectrometry are needed both for interpretation and for calibration purposes. However, under normal environmental conditions such comparisons may be affected by the considerable differences in the spatial response of these measurement techniques. A sampling methodology is presented which enables soil sample derived estimates of environmental radioactivity to be effectively compared with in-situ and aerial survey results. Examples of calibration sites and derived sensitivity estimates for 137Cs are presented for a range of environmental contexts.

環境γ線線量率の高精度測定のためのデータ処理手順

The recent development of instruments for radiation measurement has made measurement of low-level environmental gamma ray dose rates simpler and easier. Many of these instruments are commercially available. However, it is still indispensable to separate unnecessary component from the measured data, or to make appropriate corrections considering the physical meanings of the measured quantity when one trys to measure environmental gamma ray dose rate with high accuracy. In this report, a procedure of data treatment for measurement of environmental gamma ray dose rates with high accuracy using a NaI (T1) scintillation detector and spectrometric techniques is mentioned. It includes separation of unnecessary component involved in the measured pulse height spectra, correction of the angular response of the detector, calibration of the relation between pulse height and gamma ray energy, and the process of data treatment.

Organ Doses for Foetuses, Babies, Children and Adults from Environmental Gamma Rays

Organ doses for babies, children and adults and doses to foetuses from environmental gamma rays were calculated using Monte Carlo codes. Firstly, gamma ray fields in the air-over-ground geometry were simulated, neglecting the disturbance of the radiation field by the human body. The exposure modes considered were semi-infinite homogeneous volume sources in the air, infinite plane sources at a depth of 0.5 g.cm −2 in the ground and homogeneous volume sources of a natural radionuclides in the ground. The results of the simulation of the gamma ray transport in the air-over-ground geometry were used as sources irradiating the anthropomorphic phantoms : an 8 week old baby, a seven year old child and two «reference» adult phantoms of a male and a female. the doses to foetuses were estimated from the dose to the uterus of the adult female. Dose conversion factors normalised to source intensity and air kerma were calculated for monoenergetic sources (15 keV to 10 MeV) and natural and artificial radionuclides

Organ Doses as a Function of Body Weight for Environmental Gamma Rays

Organ Doses as a Function of Body Weight for Environmental Gamma Rays

Organ Doses as a Function of Body Weight for Environmental Gamma Rays.

The organ doses for γ rays from typical environmental sources were determined with Monte Carlo calculations using anthropomorphic phantoms having different body sizes. It has been suggested that body weight is the predominant factor influencing organ doses for environmental γ rays, regardless of sex and age. A weight function expressing organ doses for environmental γ rays was introduced. This function fitted well with the organ doses calculated using the different phantoms. The function coefficients were determined mathematically with the least squares method. On the assumption that this function was applicable to organ doses for human bodies with diverse characteristics, the variances in organ doses due to race, sex, age and difference in body weight of adults were investigated. The variations of organ doses due to race and sex were not significant. Differences in body weight were found to alter organ doses by a maximum of 10% for γ rays over 100 keV, and 20% for low-energy γ rays. The doses for organs ...

火山性の温泉地における地中ガスの挙動 ヘリコプターからのリモートセンシング

Aerial environmental gamma ray measurements by an advanced helicopter were carried out to clarify a behavior of radon and thoron as bed gases in regions of hot springs with high temperature, over Minami-Kayabe area in Hokkaido, Asama-Shirane area in Gunma Pref., and Azusa R. area in Nagano Pref.. As a result, some interesting facts were confirmed for bed gases behaviors in these regions, a) on intensities of radon and thoron, b) on relations of thoron and thoron/radon with temperature of hot springs, c) on reservoirs of hot fluid under the deeper ground, and d) on geothermal structures and so on.

地中ガスの挙動から見た伊豆大島の噴火 ヘリコプターからのリモートセンシング

Mihara Volcano, Izu-Ooshima Is., erupted violently on 15th November in 1986, and after six days the fissure eruption took place along a eine toward the northwest from caldera rim to somma slope of the volcano.By a advanced helicopter, aerial environmental gamma ray measurements over Izu-Ooshima Is. were carried out on 4th December in the same year and on 19th in next January, in order to clarify a behaviour of radon and thoron as bed gas in such volcanic eruptions. As a result, it can be stated that, on the occasion of volcanic eruption, the ratio of potassium/scattered gamma ray increases but instead the ratios of radon/potassium and thoron/radon decrease.The following eruption model may reasonably be interred on the behaviour of bed gases.1) On the first stage, the magma reservoir and all around basement layer are applied lateral pressure to.2) As the result, fissure in this layer contacts and then ascension of magma begins.3) Decreasing of gap volume in the fissure and supply of magmatic heat cause increasing of pressure of pore water in the fissure and the layer.4) In the continuous process, ascension of magma along the weak fissure keeps up and finally it results in eruption.5) Owing to this eruption, the comparable stress based on some pressures decrease.6) After this stage, magmas descend, the fissures in basement layer gap, and the pressure of pore water is restored.And more, the author believes that this model will be of great value in the prediction of volcanic eruption.

Determining the charged fractions of 218Po and 214Pb using an environmental gamma-ray and Rn detector.

The rate of 218Po and 214Pb atoms collected electrostatically inside an environmental gamma-ray and 222Rn detector (EGARD) was measured. These measurements were used to directly infer the charged fraction of 218Po and to calculate the charged fraction of 214Pb. Thirty-two percent of the 218Po was collected electrostatically using approximately -1500 V on a 2.54 cm diameter Mylar covered disc inside a vented A1 EGARD of 1 L volume. About 91% of the 214Pb is collected electrostatically under the same conditions. The measurements were performed in a calibrated 222Rn test chamber at the Environmental Measurements Laboratory (EML) using the Thomas alpha-counting method with 222Rn concentrations averaging about 4300 Bq m-3. The atomic collection rates were used with other measured quantities to calculate the thermoluminescent dosimeter (TLD) signal acquired from EGARD for exposure to 1 Bq m-3 of 222Rn. The calculations account for 222Rn progeny collection using a Teflon electret and alpha and beta detection using TLDs inside EGARD. The measured quantities include the energies of 218Po and 214Po alpha-particles degraded by passage through the 25 microns thick electret. The TLD responses to these alpha- and beta-particles with an average energy approaching that obtained from the combined spectra of 214Pb and 214Bi were also measured. The calculated calibration factor is within 30% of the value obtained by exposing EGARD to a known concentration of 222Rn. This result supports our charged fraction estimates for 218Po and 214Pb.

伊豆大島三原山の噴火と陥没 空中ガンマ線及び熱赤外線データの解析

Mihara Volcano, lzu-Ooshima Is., erupted violently on 15th November, 1986. At that time, vast erupted lava covered in craters on summit of the Volcano. After one year, the same volcano erupted again on 16th November, 1987. And then, though this eruption was on a small scale, the craters caved-in.Measurement on distribution of natural environmental gamma ray over lzu-Ooshima ls. was carried out on 4th December in 1986 and on 19th January in 1987, by the airborne gamma ray spectrometer system of AERRS on a helicopter Bell 212. Moreover, thermal imageries on the same island by the airborne thermal infrared video camera of AERMS were recorded at the following three epochs: on 28th November in 1986 after the first eruption, on 12th November in 1987 before the second eruption and on 19 th November in 1987 after the second eruption.As a result, some new facts on volcanic eruption and cave-in of the crater were obtained, that is, 1) On the occasion of volcanic eruption, spectrum composition of natural environmental gamma ray over the volcano shows some significant changes.2) Previous to cave-in of the crater, a ringlike thermal anomalous zone appears on the outskirts of crater, and it corresponds to a boundaryline of depressed area.

Taking a germanium detector down into the shaft of the thallium mine: What is the relevance to the solar neutrino flux determination via 205Pb?

We propose two reactions induced by environmental gamma-rays which may eventually have the same input and output nuclear channels as the neutrino capture itself and whose yields therefore must be estimated in background evaluation. From here there follows the need to know the gamma-ray spectra at the excavation site.