Gamma-ray Exposure Rate Research Articles

A Comprehensive Evaluation of the Attenuation Characteristics of Some Sliding Bearing Alloys under 0.015-15 MeV Gamma-Ray Exposure.

In this study, three different sliding bearing alloy samples were investigated in terms of their performance on attenuation characteristics and behavioral attitudes under 0.015–15 MeV gamma-ray exposure. Accordingly, different types of advanced calculation methods were utilized to calculate the radiation shielding parameters. Next, several gamma-ray shielding parameters and exposure rates in addition to fast neutron removal cross-section were determined. Furthermore, exposure and energy absorption buildup factors were determined by using G-P fitting method. Mass attenuation coefficients (MAC) values were recorded as 2.5246, 2.5703, and 2.5827 (cm2/g) for Alloy1, Alloy2, and Alloy3 samples at 15 MeV photon energy, respectively. At 40 mfp, the highest EBF values were reported as 1,376,274, 1,003,593, and 969,373 for Alloy1, Alloy2, and Alloy3 samples. The results of this extended investigation showed that the Alloy3 sample with the highest Pb reinforcement amount has superior shielding capability among the investigated samples. It can be concluded from the results that substitution of Pb with Bi in the recent alloy structure has a monotonic effect on different types of shielding parameters. Therefore, it can also be concluded that Pb is a remarkable tool for the improvement of the shielding properties of studied alloy structures.

Study of n/γ discrimination using 3He proportional chamber in high gamma-ray fields

The 3He proportional chamber is widely used for neutron measurement owing to its high neutron detection efficiency and simplicity for gamma-ray rejection. In general, the neutron and gamma-ray signals obtained from the 3He proportional chamber can be easily separated by the difference in the pulse heights. However, for a high gamma-ray field, the gamma-ray signal cannot be precisely eliminated by the pulse height due to gamma-ray pulse pileup which causes the pulse height of gamma-ray pulse to increase and making the pulses due to neutrons and gamma rays indistinguishable. In this study, an improved algorithm for n/γ discrimination using a parameter, which is the ratio of the rise time to the pulse height, is proposed. The n/γ discrimination performance of the algorithm is evaluated by applying it to 252Cf neutron signal separation from various gamma-ray exposure rate levels ranging 0.1–5 R/h. The performance is compared to that of the conventional pulse-height analysis method in terms of the gamma elimination ratio. The suggested algorithm shows better performance than the conventional one by 1.7% (at 0.1 R/h) to 70% (at 5 R/h) for gamma elimination.

Modeling background radiation in Southern Nevada

Aerial gamma ray surveys are an important tool for national security, scientific, and industrial interests in determining locations of both anthropogenic and natural sources of radioactivity. There is a relationship between radioactivity and geology and in the past this relationship has been used to predict geology from an aerial survey. The purpose of this project is to develop a method to predict the radiologic exposure rate of the geologic materials by creating a high resolution background model. The intention is for this method to be used in an emergency response scenario where the background radiation environment is unknown. Two study areas in Southern Nevada have been modeled using geologic data, images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), geochemical data, and pre-existing low resolution aerial surveys from the National Uranium Resource Evaluation (NURE) Survey. Using these data, geospatial areas that are homogenous in terms of K, U, and Th, referred to as background radiation units, are defined and the gamma ray exposure rate is predicted. The prediction is compared to data collected via detailed aerial survey by the Department of Energy's Remote Sensing Lab - Nellis, allowing for the refinement of the technique. By using geologic units to define radiation background units of exposed bedrock and ASTER visualizations to subdivide and define radiation background units within alluvium, successful models have been produced for Government Wash, north of Lake Mead, and for the western shore of Lake Mohave, east of Searchlight, NV.

Monte Carlo simulations of the gamma-ray exposure rates of common rocks

Monte Carlo simulations have been performed to model the gamma ray emission and attenuation properties of common rocks. In geologic materials, 40K, 238U, and 232Th are responsible for most gamma ray production. If the concentration of these radioelements and attenuation factors such as degree of water saturation are known, an estimate of the gamma-ray exposure rate can be made. The results show that there are no significant differences in gamma-ray screening between major rock types. If the total number of radionuclide atoms are held constant then the major controlling factor is density of the rock. Finally, the thickness of regolith or soil overlying rock can be estimated by modeling the exposure rate if the radionuclide contents of both materials are known.

Hygienic characteristics of radiation situation in the water area of The Ladoga Lake during salvaging of the radioactively contaminated experimental vessel “KIT”

In 1991, a salvage operation of the waterlogged radioactive contaminated vessel in the water area of lake Ladoga was carried out. In 1953-1954, new radiological weapons or new radiological warfare agenst were tested on this vessel. By the beginning of works, the experimental vessel was on the ooze in the half-flooded condition at a depth of 4,5-6 meters. There were approximate 2000 m3 of contaminated water and silt, mixed with oil products inside the vessel. The aims of the study are to perform:1) the hygienic assessment of radiation situation on the place of the vessel berthing before, during and after ship salvaging; 2) the radiation risk assessment for the population of the region. The assessment of the radiological situation on the board and at the place of the vessel berthing was carried out on the base of dosimetric, spectrometric and radiochemistry surveys. The gamma ray exposure rate at a height of 1 m from the superstructures and main deck outer surfaces was on average 0,14 μSv/h andit did not exceeded 0,30 μSv/h. On the place of the vessel berthing, an increasing of concentrations of Sr-90, Cs-137, Pu-239,240 in samples of water, bottom sediments, and algae has been determined. Object posed no radiation hazard to the population of the region. However, some inhabitants, despite the ban, visited the vessel for recreation and fishing. Their potential exposure dose could reach 0,5 mSv/y. Ship salvaging included salvage pontoon launching, ship’s bottom isolation, liquid waste pumping from the vessel to the special tanker, ship raising and dockage, liquid waste remediation, discharge of remediated water in the water area of lake Ladoga, solidification of liquid waste remained in the vessel’s rooms. Liquid waste remediation and strict radiation control of each process prohibited significant hygienic degradation of the radiation situation in the water area of the lake Ladoga. An insignificant increasing of levels of radioactivity in water during the vessel salvaging was due to the mixing and raising of bottom sediments. For prevention of the environmental contamination by radionuclides and oil-products on the route of the vessel traffic, next protective measures were performed: 1) setting up in the floating dock special pallet wherein collected flowing out of the vessel liquid waste; 2) solidification of liquid waste remained in the vessel’s rooms; 3) partly isolation of the vessel hull.

Study of the Periodicity of Daily Ambient Gamma ray Rates in the Mid-Korean Peninsula

A study of the ambient gamma ray exposure rate is an essential part of underground astro-particle and astro-nuclear physics experiments. The daily variation of the ambient gamma ray exposure rate has been measured at a gamma-ray monitoring post in the mid-Korean peninsula from 2003 to 2006 by using a sinusoidal function with two free parameters, an amplitude and a phase, as a function of the time. The shifted phase indicates that the besttted sine curve starts 3 hours and 7 minutes delayed from 0:00 o'clock. The maximum and the minimum ambient gamma exposure rates appear at 9:07 am and at 9:07 pm in the besttted sinusoidal curve for the daily variation of ambient gamma ray rate. Also, we will provide some information for the daily gamma ray exposure rate.

Daily and Annual Variations of the Ambient Gamma Ray Exposure Rates on the Korean Peninsula from 2003 to 2006

A study of the ambient gamma ray exposure rate is essential as a background for underground particle physics experiments such as the neutrino and the non-bayonic dark matter experiments. Here, we report patterns for the daily and the annual variations of the ambient gamma ray exposure rate measured at the Cheongju Regional Radiation Monitoring Post from January 2003 to December 2006 by using a pressurized ionization chamber. The daily ambient gamma ray exposure rate appears to have a sinusoidal pattern with an annual average daily variation of 0.17 μR/h. The maximum ambient gamma exposure rate appears from 7 : 30 am to 9 : 30 am and the minimum from 7 : 30 pm to 10 : 30 pm. The annual average of the ambient gamma ray rate was 12.78 μR with an annual variation of 1 μR/h for the years from 2003 to 2006. The fluctuation in the seasonal variation was 7.8 percent while the fluctuation the daily varition was 1.3 percent during the years from 2003 to 2006.

Annual effective dose due to natural radionuclides in building blocks in eight cities of Southwestern Nigeria

The specific absorbed dose rates due to (226)Ra, (232)Th and (40)K in building blocks have been determined for a model dwelling dimension of 3.6 x 3.6 x 3.0 m(3), wall thickness 10 cm and density of 1.73 x 10(3) kg m(-3) in eight cities across Southwestern Nigeria. The Mustonen method of calculating gamma-ray annual exposure rate from the radioactivity concentrations (Bq kg(-1)) of (226)Ra, (232)Th and (40)K in the blocks have been adopted with modifications to suit the Nigerian situation. The specific absorbed dose rates obtained were as follows: 11.36, 14.94 and 0.92 microGy y(-1) per Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. These dose rates were used to calculate the annual effective dose in the model dwelling. The annual effective dose obtained varied between 209.20 (Osogbo) and 400.36 microSv y(-1) (Abeokuta). The values are in the range of values obtained for the German Democratic Republic (309 microSv y(-1)) and Jordan (470 microSv y(-1)).

Radiation Monitoring Along The Creeks Of Calabar River And Its Environs

Measurement of gamma-ray exposure rate using a portable dosimeter was taken. The exposure rate was taken one meter above water and ground levels for radiological assessment at the Calabar River and its environs of Cross River State, Nigeria. The study reveals equivalent dose rate of 0.007µSv/hr and 0.115µSv/hr within the river and its environs respectively. Subsequently, the values are considered far below the radiation limits of 1mSv stipulated for members of public per year. KEY WORDS: Gamma-ray, radiological assessment, Calabar river, Environs, members of public. Global Journal of Pure and Applied Sciences Vol.11(1) 2005: 137-140

Determination of Gamma-Ray Exposure Rate from Short-Lived Fission Products under Criticality Accident Conditions

For the assessment of γ-ray doses from short-lived fission products (FPs) under criticality accident conditions, γ-ray exposure rates varying with time were experimentally determined in the Transient Experiment Critical Facility (TRACY). The data were obtained by reactivity insertion in the range of 1.50 to 2.93$. It was clarified from the experiments that the contribution of γ-ray from short-lived FPs to total exposure during the experiments was evaluated to be 15 to 17%. Hence, the contribution cannot be neglected for the assessment of γ-ray doses under criticality accident conditions. Computational analyses also indicated that γ-ray exposure rates from short-lived FPs calculated with the Monte Carlo code, MCNP4B, and photon sources based on the latest FP decay data, the JENDL FP Decay Data File 2000, well agreed with the experimental results. The exposure rates were, however, extremely underestimated when the photon sources were obtained by the ORIGEN2 code. The underestimation is due to lack of energy-dependent photon emission data for major short-lived FP nuclides in the photon database attached to the ORIGEN2 code. It was also confirmed that the underestimation arose in 1,000 s or less of time lapse after an initial power burst.

Determination of Gamma-Ray Exposure Rate from Short-Lived Fission Products under Criticality Accident Conditions.

For the assessment of γ-ray doses from short-lived fission products (FPs) under criticality accident conditions, γ-ray exposure rates varying with time were experimentally determined in the Transient Experiment Critical Facility (TRACY). The data were obtained by reactivity insertion in the range of 1.50 to 2.93$. It was clarified from the experiments that the contribution of γ-ray from short-lived FPs to total exposure during the experiments was evaluated to be 15 to 17%. Hence, the contribution cannot be neglected for the assessment of γ-ray doses under criticality accident conditions. Computational analyses also indicated that γ-ray exposure rates from short-lived FPs calculated with the Monte Carlo code, MCNP4B, and photon sources based on the latest FP decay data, the JENDL FP Decay Data File 2000, well agreed with the experimental results. The exposure rates were, however, extremely underestimated when the photon sources were obtained by the ORIGEN2 code. The underestimation is due to lack of energy-dependent photon emission data for major short-lived FP nuclides in the photon database attached to the ORIGEN2 code. It was also confirmed that the underestimation arose in 1,000 s or less of time lapse after an initial power burst.

ブラジル・ガラパリ周辺の空間線量率予備調査

A preliminary survey of the gamma-ray exposure rate was carried out at Guarapari and Meaipe in Brazil in September 1998. In those areas, exposure rates in the streets ranged from 0.1 to 0.4μGy/h except for a few places such as near the beaches. Exposure rates inside houses were lower than 0.2μGy/h except for two houses where an exposure rate of 0.4μGy/h was measured. Our effective dose rate from external terrestrial irradiation was 0.17μSv/h on the average during the period of our three-day stay in Guarapari (outdoors and indoors). These values are lower than those observed in the 1960s, which were cited in UNSCEAR reports. This fact suggests that the natural radiation environment of Guarapari has varied with urbanization, which brought paved streets, and changes in the structure and building materials of houses. A detailed survey is necessary in order to evaluate the present exposure rates in these areas.

Results of modeling and experimental measurements for the design of a neutron surface moisture measurement sensor

Computer modeling and experimental testing have been performed to produce a design for a neutron-moderation-based surface moisture sensor. Results indicate that this sensor should be capable of providing information about the moisture concentration profile in the top 15 cm of material. Tests show that the sensor should be capable of operating in the expected high temperature and gamma-ray exposure rate fields within the Hanford Site tanks. A field-ready sensor and an in-tank deployment system were fabricated for application of this technology to the Hanford Site tank farms.

モデルハウスの屋内・外自然空間放射線線量率の測定

Natural gamma-ray and cosmic-ray exposure rates were measured indoors and outdoors for 94 model houses of four housing centers in Nagoya to obtain basic data for estimation of the population dose. Influence of the structure of houses on indoor exposure rates and relationship between indoor and outdoor natural gamma-ray exposure rates were studied. Exposure rates were measured with a 1.5″φ×4″ NaI (Tl) scintillation counter and a 6″φ spherical plastic scintillation counter.The mean indoor natural gamma-ray exposure rate in ferro-concrete buildings was about 40% higher than that in fireproof wooden houses, about 60% higher than that in light-weight steel-framed buildings, in fireproof wooden houses, it was also about 10% higher than in light-weight steel-framed building.The ratio of indoor to outdoor natural gamma-ray exposure rate was found to be about 0.95±0.15, 0.77±0.10, and 0.72±0.13 for ferro-concrete buildings, fireproof wooden houses and light-weight steel-framed buildings, respectively.The mean indoor cosmic-ray exposure rate in ferro-concrete buildings was 2.8μR/h, about 18% lower than the outdoors. The indoor cosmic-ray exposure rate in fireproof wooden houses and light-weight steel-framed buildings were 3.2μR/h, about 6% lower than the outdoors.

積雪による地殻γ線線量率の減衰

In order to clarify the diminution characteristics of terrestrial gamma ray exposure rate due to snow cover, measurements were performed on the ground with and without snow cover. The diminution factors observed were 0.36-0.17 for 12-23g/cm2 of water equivalent of the snow cover. According to a calculation by the Monte Carlo method, the corresponding diminution factors were 0.32-0.16. They agreed well as a whole, while the fluctuation of the diminution factors based on the measured exposure rate were fairly large. The fluctuation is deemed to be due to the inhomogeneity in the distribution of the snow cover as well as the gamma ray field. The fluctuation is expected to decrease with increase in the degree of their homogeneity.

Distribution of Gamma and Cosmic Ray Exposure Rates in a 12-Storied Concrete Building

General patterns of the ? and cosmic ray exposure rate distribution inside a 12-storied concrete building were obtained through simultaneous measurements using an intrinsic germanium spectrometer, NaI(Tl) scintillation detectors and a high pressure ionisation chamber. In general, the horizontal ? exposure rate increased with distance from a window, then became constant at the interior of a room. The cosmic ray exposure rate decreased with increasing distance from a window, then became constant within the room. The vertical profile of the cosmic ray exposure rate indicated a marked change between the roof and the upper floors because of the filtering out of the soft electromagnetic component of the cosmic ray flux, then decreased slowly with depth in the building. Gamma exposure rates varied from floor to floor and from room to room because of varying wall compositions. The representativeness of a measured value with regard to these observed patterns is also discussed.

Intercomparison Between EML Method and JAERI Method for the Measurement of Environmental Gamma Ray Exposure Rates

Intercomparison Between EML Method and JAERI Method for the Measurement of Environmental Gamma Ray Exposure Rates

Wide Range Wave-Number Spectra of Place-to-Place Variations in Terrestrial Gamma-Ray Exposure Rate

Wide Range Wave-Number Spectra of Place-to-Place Variations in Terrestrial Gamma-Ray Exposure Rate

Wide range wave-number spectra of place-to-place variations in terrestrial gamma-ray exposure rate.

Click to increase image sizeClick to decrease image sizeKEYWORDS: background radiationcarborne surveydose ratesgamma radiationmaximum entropy methodpower spectral densityradiation monitoringspectral analysiswave-number spectrum

A comparison of calculated indoor radiation exposure with the results of measurements

A model has been developed for the calculation of external and internal radiation exposure of the population in dwellings. The model consists of two adjacent rooms on top of a crawl-space. The indoor gamma ray exposure rates and the radon concentrations in indoor air, predicted for a variety of conditions, are compared with observations. Predictions and observations are in reasonable agreement; for the radon concentration the predictions may be around 40% too low.