Gamma-Ray Imaging for Generating 3D Dose Rate Maps

2011 ◽  
Author(s):  
Karl Hughes ◽  
Edmund Cracknell
Keyword(s):  
Dose Rate ◽  
Source Term ◽  
Gamma Ray ◽  
Radiation Transport ◽  
Simple Procedure ◽  
Two Dimensions ◽  
Nuclear Industry ◽  
Dose Rates ◽  
Physical Measurements ◽  
Gamma Ray Imaging

The use of gamma-ray imaging has become established in the nuclear industry, especially in the fields of decommissioning and clean-up, for identifying the origins of elevated gamma dose rates. Since their first use in the mid 1990s, gamma-ray imaging devices, such as the Babcock RadScan, have been used to produce colour overlay plots that indicate, in two dimensions, the locations and distribution of radioactive contaminants. This information is invaluable in helping project managers to plan clean-up and shielding activities, ensuring that all work carried out is cost effective and ALARP. Recent work undertaken by Babcock demonstrates the capability to generate 3D maps of dose rate fields from the output of gamma-ray imaging work. The combination of gamma-ray imaging survey and resultant dose map is a very powerful tool for planning decommissioning. The conventional gamma-ray image provides an unambiguous identification of the origins of the dose rates present whilst the 3D dose map allows the dose uptake to personnel to be determined. Furthermore, the ability to quantify the effect of clean-up or shielding on the dose rates is possible, providing project teams with a metric for determining the best option available. A simple procedure is followed to generate 3D dose maps from gamma-ray imaging data. Firstly a model of the plant area is constructed. This model can be generated from existing plant drawings, from laser scan surveys, or from simple physical measurements taken on plant. The model includes information about the shielding properties of the plant structures, and can be easily modified to demonstrate the effect of adding more shielding, or of reducing any of the source terms. The data from a gamma-ray imager, such as RadScan, are analysed to generate distributions of radionuclide specific activities. These activities are entered into the model and form the source term. The advantage of using a gamma ray imager to generate the source term is that the location and distribution of the source is accurately represented in the model, thus ensuring that accurate dose maps are generated. Once the model has been completed it is analysed using a radiation transport modelling code such as Attila to produce the 3D dose maps (although other codes are available which could perform the same function). This paper describes an example of how this technique has been used to generate 3D dose maps for a customer and builds on earlier work with RadScan which provides quantitative in-cell assay.

Development of New Simulation Software System to Evaluate Radiation Dose Rates in a Wide Radioactively Contaminated Area

2012 ◽  
Author(s):  
Tomoharu Hashimoto ◽  
Masahiro Kondo ◽  
Ryuichi Tayama ◽  
Hideho Gamo
Keyword(s):  
Radiation Dose ◽  
Dose Rate ◽  
Gamma Ray ◽  
Simulation Software ◽  
Radiation Dose Rate ◽  
Dose Rates ◽  
Reduce Radiation Exposure ◽  
Radiation Sources ◽  
Reduction Effect ◽  
Contaminated Area

The Japanese government plans to conduct decontamination tasks in radioactively contaminated areas. For such a situation, we developed a system that evaluates radiation dose rates in a wide radioactively contaminated area by utilizing our radiation dose evaluation technology. This system can not only generate present maps of radiation dose rate in the air based on the dose rate measured at the surface of the contaminated areas, but can also quickly calculate the reduction effect of dose rate due to decontamination tasks by entering decontamination factors. The system can then formulate decontamination plans and make it possible to plan measures to reduce radiation exposure for workers and local residents. Radioactive nuclides that contribute to gamma-ray dose rate are mainly Cs-134 and Cs-137 in soil, on trees, buildings, and elsewhere. Shapes of such radiation sources are assumed to be 10m square or 100m square. If it is unsuitable that the radiation sources assume to squares, the radiation sources can assume to point. The relation between distance from the surface or point source and the radiation dose rate is calculated using MCNP5 code (A General Monte Carlo N-Particle Transport Code - Version 5), and approximated using four-parameter empirical formula proposed by Harima et al. In addition, the system can consider shielding such as soil, concrete, and iron. When setting such shielding, the skyshine dose rate is taken into account in dose rate calculation.

Assessment of shutdown dose rates at the ESS target cooling system using SCALE6.2

2020 ◽  
Vol 22 (2-3) ◽  
pp. 309-318
Author(s):  
Amalia Chambon ◽  
Esben Klinkby ◽  
Leif Emås ◽  
Bent Lauritzen
Keyword(s):  
Dose Rate ◽  
Source Term ◽  
Cooling System ◽  
High Energy ◽  
Beam Power ◽  
Robot Arm ◽  
Robotic Arms ◽  
Dose Rates ◽  
Spallation Source ◽  
Conservative Estimation

The production of high-energy neutrons at the European Spallation Source through the spallation process may cause an erosion of the tungsten target. The eroded particles could be released into the target helium cooling system which contains four kind of filters. Among them, the auxiliary filters called “getters” are designed to capture volatile elements and remaining dust. In this work, the ORNL’s SCALE6.2 modelling and simulation suite for nuclear safety analysis is applied to assess shutdown dose rates and determine if added shielding and/or robotic arms are needed for their maintenance. SCALE6.2 is well adapted to treat this problem as it allows for isotope selection regarding source term calculation. Dose rates are determined by an ORIGEN2 source term and a MAVRIC shielding sequence calculation. As SCALE6.2 is non-standard software for ESS, the results are verified against MCNP, which is the baseline tool for neutronics analysis at ESS. Dose rate calculations show that additional shielding and/or robot arm are not needed to remove the getters after 3 months of cooling time, following 5400 h of operation at 5 MW beam power. At a distance of 1 mm from the getter, the dose rate is 0.2 mSv/h in the most conservative estimation.

scholarly journals Gross Gamma Dose Rate Measurements for TRIGA Spent Nuclear Fuel Burnup Validation

2002 ◽  
Author(s):  
P. L. Winston ◽  
J. W. Sterbentz
Keyword(s):  
Dose Rate ◽  
Spent Nuclear Fuel ◽  
Gamma Ray ◽  
Gamma Dose ◽  
Gamma Dose Rate ◽  
Primary Concern ◽  
Examination System ◽  
Dose Rates ◽  
Calculated Dose ◽  
Fuel Elements

Gross gamma-ray dose rates from six spent TRIGA fuel elements were measured and compared to calculated values as a means to validate the reported element burnups. A newly installed and functional gamma-ray detection subsystem of the In-Cell Examination System was used to perform the measurements and is described in some detail. The analytical methodology used to calculate the corresponding dose rates is presented along with the calculated values. Comparison of the measured and calculated dose rates for the TRIGA fuel elements indicates good agreement (less than a factor of 2 difference). The intent of the subsystem is to measure the gross gamma dose rate and correlate the measurement to a calculated dose rate based on the element s known burnup and other pertinent spent fuel information. Although validation of the TRIGA elements’ burnup is of primary concern in this paper, the measurement and calculational techniques can be used to either validate an element’s reported burnup or provide a burnup estimate for an element with an unknown burnup.

scholarly journals An inverse modeling method to assess the source term of the Fukushima nuclear power plant accident using gamma dose rate observations

2013 ◽  
Vol 13 (6) ◽  
pp. 15567-15614 ◽  
Author(s):  
O. Saunier ◽  
A. Mathieu ◽  
D. Didier ◽  
M. Tombette ◽  
D. Quélo ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Dose Rate ◽  
Inverse Modeling ◽  
Nuclear Power ◽  
Source Term ◽  
Noble Gases ◽  
Atmospheric Dispersion ◽  
Nuclear Accident ◽  
Dose Rates

Abstract. The Chernobyl nuclear accident and more recently the Fukushima accident highlighted that the largest source of error on consequences assessment is the source term including the time evolution of the release rate and its distribution between radioisotopes. Inverse modeling methods, which combine environmental measurements and atmospheric dispersion models, have proven efficient in assessing source term due to an accidental situation (Gudiksen, 1989; Krysta and Bocquet, 2007; Stohl et al., 2012a; Winiarek et al., 2012). Most existing approaches are designed to use air sampling measurements (Winiarek et al., 2012) and some of them also use deposition measurements (Stohl et al., 2012a; Winiarek et al., 2013) but none of them uses dose rate measurements. However, it is the most widespread measurement system, and in the event of a nuclear accident, these data constitute the main source of measurements of the plume and radioactive fallout during releases. This paper proposes a method to use dose rate measurements as part of an inverse modeling approach to assess source terms. The method is proven efficient and reliable when applied to the accident at the Fukushima Daiichi nuclear power plant (FD-NPP). The emissions for the eight main isotopes 133Xe, 134Cs, 136Cs, 137Cs, 137mBa, 131I, 132I and 132Te have been assessed. Accordingly, 103 PBq of 131I, 35.5 PBq of 132I, 15.5 PBq of 137Cs and 12 100 PBq of noble gases were released. The events at FD-NPP (such as venting, explosions, etc.) known to have caused atmospheric releases are well identified in the retrieved source term. The estimated source term is validated by comparing simulations of atmospheric dispersion and deposition with environmental observations. The result is that the model-measurement agreement for all of the monitoring locations is correct for 80% of simulated dose rates that are within a factor of 2 of the observed values. Changes in dose rates over time have been overall properly reconstructed, especially in the most contaminated areas to the northwest and south of the FD-NPP. A comparison with observed atmospheric activity concentration and surface deposition shows that the emissions of caesiums and 131I are realistic but that 132I and 132Te are probably underestimated and noble gases are likely overestimated. Finally, an important outcome of this study is that the method proved to be perfectly suited to emergency management and could contribute to improve emergency response in the event of a nuclear accident.

Dose Rate Effects in Fluorescence Chemical Dosimeters Exposed to Picosecond Electron Pulses: An Accurate Measurement of Low Doses at High Dose Rates

2021 ◽  
Author(s):  
Martin Precek ◽  
Petr Kubelik ◽  
Ludek Vysin ◽  
Uli Schmidhammer ◽  
Jean-Philippe Larbre ◽  
...  
Keyword(s):  
Dose Rate ◽  
Gamma Ray ◽  
High Dose Rate ◽  
Attractive Alternative ◽  
High Dose ◽  
Low Doses ◽  
Solution Ph ◽  
Short Pulses ◽  
Dose Rates ◽  
Trimesic Acid

The development of ultra-intense electron pulse for applications needs to be accompanied by the implementation of a practical dosimetry system. In this study four different systems were investigated as dosimeters for low doses with a very high-dose-rate source. First, the effects of ultra-short pulses were investigated for the yields of the Fricke dosimeter based on acidic solutions of ferrous sulfate; it was established that the yields were not significantly affected by the high dose rates, so the Fricke dosimeter system was used as a reference. Then, aqueous solutions of three compounds as fluorescence chemical dosimeters were utilized, each operated at a different solution pH: terephthalic acid - basic, trimesic acid - acidic, and coumarin-3- carboxylic acid (C3CA) - neutral. Fluorescence chemical dosimeters offer an attractive alternative to chemical dosimeters based on optical absorption for measuring biologically relevant low doses because of their higher sensitivity. The effects of very intense dose rate (TGy/s) from pulses of fast electrons generated by a picosecond linear accelerator on the chemical yields of fluorescence chemical dosimeters were investigated at low peak doses (<20 Gy) and compared with yields determined under low-dose-rate irradiation from a 60 Co gamma-ray source (mGy/s). For the terephthalate and the trimesic acid dosimeters changes in the yields were not detected within the estimated (∼10%) precision of the experiments, but, due to the complexity of the mechanism of the hydroxyl radical initiated reactions in solutions of the relevant aromatic compounds, significant reductions of the chemical yield (–60%) were observed when the C3CA dosimeter was irradiated with the ultra-short pulses.

The Use of Radiological Characterisation in Support of the Design and Build of a New Facility in an Area of Elevated Dose Rate

2009 ◽  
Author(s):  
Karl Hughes ◽  
David Thornley ◽  
Czeslaw Pienkowski
Keyword(s):  
Dose Rate ◽  
Gamma Ray ◽  
Gamma Spectroscopy ◽  
Gamma Dose ◽  
Spent Fuel ◽  
North West ◽  
Dose Rates ◽  
Railway Line ◽  
The North ◽  
New Facility

A new building, a maintenance facility, is to be constructed in the ‘separation area’ of the Sellafield Site. Sellafield is a complex and busy nuclear facility covering about two square miles in the north-west of the United Kingdom. The facility, which is to provide necessary storage and maintenance functionality to support bulk waste retrievals from legacy silos, is being built in close proximity to spent fuel storage ponds, intermediate level legacy waste stores and a pipebridge carrying active materials. In addition, the site is adjacent to a main pedestrian and vehicle thoroughfare and a railway line used for the regular transfer of nuclear materials. The facility itself is to be built on the site of a recently demolished active facility. The ambient gamma dose rates in the construction area have been measured to be typically 5 to 50 μSv/hr. Although there are known specific sources of dose rate close to the construction site, the relative contributions of each within the envelope of the new facility are unknown. This paper describes how a series of gamma dose rate measurements, gamma spectroscopy measurements and gamma-ray imaging surveys, using RadScan® 800, have been used to better understand the origins of the dose rates at a number of key locations within the area. The results of the survey are being used to assess the requirements for shielding within the structure of the facility in order to reduce the dose to personnel that will work there when it is operational. The results are also being used to identify whether any localised shielding would prove beneficial for reduction of the dose both during construction and occupancy. The unique mix of facilities surrounding the site have meant that the contributions to the dose rate come not only from adjacent facilities in the form of unscattered, higher energy, penetrating radiation, but also in the form of lower energy scattered radiation, both from radiation that has passed through shielding and also in the form of skyshine. Skyshine is the term for the radiation that has escaped a facility and ‘bounced’ off the sky to return to earth. The radiometric measurements, which were collected over a period of a few days, were able to provide a useful understanding of each of these sources of dose, and to quantify the relative contributions of each.

Measurement and analysis of dose rates and gamma-ray fluxes in an ITER shut-down dose rate experiment

2002 ◽  
Vol 63-64 ◽  
pp. 211-215 ◽  
Author(s):  
K Seidel ◽  
Y Chen ◽  
U Fischer ◽  
H Freiesleben ◽  
D Richter ◽  
...  
Keyword(s):  
Dose Rate ◽  
Gamma Ray ◽  
Dose Rates ◽  
Measurement And Analysis ◽  
Rate Experiment

ELEVATION OF GAMMA DOSE RATE BY CONSTRUCTION OF THE ASIAN HIGHWAY 3 (AH3) BETWEEN ULAANBAATAR AND SAINSHAND, MONGOLIA

2018 ◽  
Vol 184 (1) ◽  
pp. 127-134 ◽  
Author(s):  
Yasutaka Omori ◽  
Atsuyuki Sorimachi ◽  
Manlaijav Gun-Aajav ◽  
Nyamdavaa Enkhgerel ◽  
Galnemekh Oyunbolor ◽  
...  
Keyword(s):  
Dose Rate ◽  
Gamma Ray ◽  
Natural Radionuclides ◽  
Pulse Height ◽  
Gamma Dose ◽  
Gamma Dose Rate ◽  
Radiation Level ◽  
Dose Rates ◽  
Gamma Dose Rates ◽  
Road Materials

Abstract The present study aimed at examining changes of gamma radiation level associated with road construction in Mongolia. A car-borne survey of gamma dose rate was made for a paved, ~450-km long part of the Asian Highway 3 between Ulaanbaatar and Sainshand. The gamma dose rates ranged from 48 to 173 nGy/h. Elevation of the gamma dose rates was observed only on a 86-km long segment of the survey route which was newly constructed from 2011 to 2013. The gamma dose rates over the newer paved segment were twice as high as those over the bare dirt surface alongside it. Outdoor measurements of gamma-ray pulse height distributions also indicated an abundance of natural radionuclides, especially 232Th-series elements in road materials. These findings suggest that the gamma dose rates were elevated by introduction of road materials containing large amounts of natural radionuclides.

scholarly journals An inverse modeling method to assess the source term of the Fukushima Nuclear Power Plant accident using gamma dose rate observations

2013 ◽  
Vol 13 (22) ◽  
pp. 11403-11421 ◽  
Author(s):  
O. Saunier ◽  
A. Mathieu ◽  
D. Didier ◽  
M. Tombette ◽  
D. Quélo ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Dose Rate ◽  
Inverse Modeling ◽  
Nuclear Power ◽  
Source Term ◽  
Atmospheric Dispersion ◽  
Nuclear Accident ◽  
Fukushima Accident ◽  
Dose Rates

Abstract. The Chernobyl nuclear accident, and more recently the Fukushima accident, highlighted that the largest source of error on consequences assessment is the source term, including the time evolution of the release rate and its distribution between radioisotopes. Inverse modeling methods, which combine environmental measurements and atmospheric dispersion models, have proven efficient in assessing source term due to an accidental situation (Gudiksen, 1989; Krysta and Bocquet, 2007; Stohl et al., 2012a; Winiarek et al., 2012). Most existing approaches are designed to use air sampling measurements (Winiarek et al., 2012) and some of them also use deposition measurements (Stohl et al., 2012a; Winiarek et al., 2014). Some studies have been performed to use dose rate measurements (Duranova et al., 1999; Astrup et al., 2004; Drews et al., 2004; Tsiouri et al., 2012) but none of the developed methods were carried out to assess the complex source term of a real accident situation like the Fukushima accident. However, dose rate measurements are generated by the most widespread measurement system, and in the event of a nuclear accident, these data constitute the main source of measurements of the plume and radioactive fallout during releases. This paper proposes a method to use dose rate measurements as part of an inverse modeling approach to assess source terms. The method is proven efficient and reliable when applied to the accident at the Fukushima Daiichi Nuclear Power Plant (FD-NPP). The emissions for the eight main isotopes 133Xe, 134Cs, 136Cs, 137Cs, 137mBa, 131I, 132I and 132Te have been assessed. Accordingly, 105.9 PBq of 131I, 35.8 PBq of 132I, 15.5 PBq of 137Cs and 12 134 PBq of noble gases were released. The events at FD-NPP (such as venting, explosions, etc.) known to have caused atmospheric releases are well identified in the retrieved source term. The estimated source term is validated by comparing simulations of atmospheric dispersion and deposition with environmental observations. In total, it was found that for 80% of the measurements, simulated and observed dose rates agreed within a factor of 2. Changes in dose rates over time have been overall properly reconstructed, especially in the most contaminated areas to the northwest and south of the FD-NPP. A comparison with observed atmospheric activity concentration and surface deposition shows that the emissions of caesiums and 131I are realistic but that 132I and 132Te are probably underestimated and noble gases are likely overestimated. Finally, an important outcome of this study is that the method proved to be perfectly suited to emergency management and could contribute to improve emergency response in the event of a nuclear accident.

scholarly journals Radioactivity of soil in Croatia II: 137Cs, 40K, and absorbed dose rate

2021 ◽  
Vol 72 (1) ◽  
pp. 15-22
Author(s):  
Marko Šoštarić ◽  
Branko Petrinec ◽  
Mak Avdić ◽  
Ljerka Petroci ◽  
Milica Kovačić ◽  
...  
Keyword(s):  
Dose Rate ◽  
Gamma Ray ◽  
Absorbed Dose ◽  
Gamma Ray Spectrometry ◽  
External Exposure ◽  
Vegetation Density ◽  
Absorbed Dose Rate ◽  
Dose Rates ◽  
Activity Concentrations ◽  
Uncultivated Soil

Abstract We took samples of uncultivated soil from the surface layer (0–10 cm) at 138 sites from all over Croatia and measured their radionuclide activity concentrations with high-resolution gamma-ray spectrometry. This second part of our report brings the results on 40K and 137Cs to complement those on the 232Th and 238U decay chains addressed in the first part. Together they give the most complete picture of radioactivity of Croatian soil so far. Activity concentrations of 40K were the highest in the Pannonian region, and there was an opposite trend for 137Cs. We found that the concentrations of 137Cs tended to increase with altitude, annual precipitation, and vegetation density. The concentration ratio of 137Cs and K in soil, which indicates the potential for 137Cs entering food chains via uptake by plants, was the lowest in agriculturally important areas in the east of the Pannonian region. In addition, we used the obtained results on activity concentrations to calculate the related absorbed dose rate as a measure of external exposure to ionising radiation from soil. The sum of the absorbed dose rates for naturally occurring radionuclides and 137Cs showed that external exposure was generally the highest in the Dinaric region and Istrian Peninsula.

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