Frazier Bronson | Missouri University of Science and Technology (original) (raw)
Papers by Frazier Bronson
The ISOCS mathematical method developed by Canberra Industries is a well established technique fo... more The ISOCS mathematical method developed by Canberra Industries is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user inputs the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. Canberra is developing a customized efficiency optimization software, which is an extension of the ISOCS, known as "Advanced ISOCS" that varies the uncertain parameters and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, or FRAM, activities from multi-l...
In the process of decommissioning contaminated facilities, and in the conduct of normal operation... more In the process of decommissioning contaminated facilities, and in the conduct of normal operations involving radioactive material, it is frequently required to show that large areas of land are not contaminated, or if contaminated that the amount is below an acceptable level. However, it is quite rare for the radioactivity in the soil to be uniformly distributed. Rather it is generally in a few isolated and probably unknown locations. One way to ascertain the status of the land concentration is to take soil samples for subsequent measurement in the laboratory. Another way is to use in-situ gamma spectroscopy. In both cases, the non-uniform distribution of radioactivity can greatly compromise the accuracy of the assay, and makes uncertainty estimates much more complicated than simple propagation of counting statistics. This paper examines the process of determining the best way to estimate the activity on the tract of land, and gives quantitative estimates of measurement uncertainty ...
In situ gamma spectroscopy has been successfully used for decommissioning surveys and environment... more In situ gamma spectroscopy has been successfully used for decommissioning surveys and environmental remediation surveys for many years. With the recent advancements in technology of very portable and reliable Ge detectors, high quality digital MCAs, and mathematical efficiency calibration algorithms that are fast and accurate, this technology is now available to operating nuclear facilities. In situ gamma spectroscopy offers advantages over the traditional method of extracting a representative sample, transporting it to a laboratory, and then preparing the sample for counting. Getting the sample is the major problem. Some samples are physically difficult to obtain (subsurface soil, concrete, activated materials, material inside pipes or tanks, etc.). Some samples are physically dangerous to take (very radioactive items like resin beads, concrete cores or steel coupons, pressurized gases, hot water, corrosive or toxic items). Since in situ spectroscopy is a non-contact process, and s...
Gamma ray spectrometry using High Purity Germanium (HPGe) detectors is commonly employed in assay... more Gamma ray spectrometry using High Purity Germanium (HPGe) detectors is commonly employed in assaying radioactive waste streams from a variety of sources: nuclear power plants, Department of Energy (DOE) laboratories, medical facilities, decontamination and decommissioning activities etc. The radioactive material is typically packaged in boxes or drums (for e.g. B-25 boxes or 208 liter drums) and assayed to identify and quantify radionuclides. Depending on the origin of the waste stream, the radionuclides could be special nuclear materials (SNM), fission products, or activation products. Efficiency calibration of the measurement geometry is a critical step in the achieving accurate quantification of radionuclide content. Due to the large size of the waste items, it is impractical and expensive to manufacture gamma ray standard sources for performing a measurement based calibration. For well over a decade, mathematical efficiency methods such as those in Canberra's In Situ Object ...
The ISOCS mathematical method developed by Canberra Industries is a well established technique fo... more The ISOCS mathematical method developed by Canberra Industries is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user inputs the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. Canberra is developing a customized efficiency optimization software, which is an extension of the ISOCS, known as “Advanced ISOCS” that varies the uncertain parameters and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, or FRAM, activities from multi-line nuclid...
Large NaI detectors are commonly used in gamma measurement systems where nuclide identification a... more Large NaI detectors are commonly used in gamma measurement systems where nuclide identification and quantification is desired. These systems are used to measure people, soil, drums, boxes, animals, and other things. For quantification, an efficiency calibration must be performed, which becomes increasingly difficult as the sources become large and complicated. Mathematical techniques can be quite useful here, if they are easy enough to use, and accurate enough for the application. A series of experiments was performed to show how accurately the efficiency of large (3”x5”x16”) rectangular NaI detectors can be computed with techniques that could be implemented within the commercially available ISOCS mathematical efficiency calibration software. This software assumes that the detector response function is cylindrically symmetric, which certainly isn’t the case here. But, perhaps it is good enough for the applications for which these large rectangular detectors are commonly used. A seri...
wmsym.org
A large variety of non-destructive assay (NDA) systems have been developed for the analysis of wa... more A large variety of non-destructive assay (NDA) systems have been developed for the analysis of waste containers by passive gamma-ray spectroscopy. Examples of such systems include Segmented Gamma Scanners (SGS), Q 2-style drum counters, Large Box Counters, and far-field measurement systems. The calibration of these systems typically involves the purchase and construction of "calibration" containers that are to varying degree representative of the items to be assayed. Typically these "calibration" containers represent idealizations of the waste stream with homogenized matrix materials and pseudouniform source distributions. But, for complete and correct calibrations, these containers must span the operational range of the system, and consequently include extreme and difficult configurations of matrix, density and source distribution. The NDA systems themselves typically have multiple configurations to deal with different kinds of items, and each configuration must be calibrated separately, often with different calibration sources. If the system is changed or modified, it must subsequently be recalibrated experimentally. The accuracy of such a calibration is typically estimated by performing a limited number of "worst-case" scenarios to establish the bounds of the Total Measurement Uncertainty (TMU). In its entirety, the calibration and uncertainty estimation of an NDA system represents a significant up-front expense. Alternatives exist to the source-based calibrations of NDA systems. Among these alternatives is the mathematical modeling of the efficiency response of a given system to a particular waste configuration. In this situation, the system is calibrated using physically-relevant models of the gamma-ray response, with a relatively small number of validation measurements performed to demonstrate proper operation of the system and establish traceability to national standards. Due to the complexity of NDA systems and waste streams, purely analytically models are typically not feasible, but semi-analytical Monte-Carlo approaches based on the fundamental principles of gamma-ray interactions have proven to be very successful. These semi-analytical approaches are sufficiently versatile to allow the modeling of general waste stream configurations. Systems can be quickly adapted to changing waste streams or detector configurations. Not only can the measurement limits of the TMU be accurately estimated with semianalytical techniques, but its functional form can be properly modeled to allow a more accurate assessment of the entire waste stream. In this paper, we will present a survey of instruments including SGS, Box Counter, and far-field systems that have been calibrated using semi-analytical mathematical models. We will discuss experiences in calibration techniques, modeling of the TMU, and recent advances that further enhance the capabilities of such approaches.
Applied Radiation and Isotopes, 2009
An MCNP model of a co-axial HPGe detector, defined by the specification sheet and without paramet... more An MCNP model of a co-axial HPGe detector, defined by the specification sheet and without parameter optimization, was used to assess practicality for efficiency characterization and complex spectra simulation. Simulated efficiencies, with and without Gaussian energy broadening, were compared against an experimental calibration for a standard counting geometry. Results show that this minimal detector model predicted efficiencies within 6% of experimental values at energies above 100 keV, while including energy broadening offered little improvement. This work shows that extensive detector characterization and optimization of parameters is not absolutely necessary, thereby reducing the experimental burden associated with detector modeling for many applications.
Ｎｕｃｌ Ｉｎｓｔｒｕｍ Ｍｅｔｈｏｄｓ Ｐｈｙｓ Ｒｅｓ Ｓｅｃｔ Ａ Ａｃｃｅｌ Ｓｐｅｃｔｒｏｍｅｔｅｒｓ Ｄｅｔｅｃｔ Ａｓｓｏｃ, 1999
A design study has been performed for a system that should measure the Cs-137 activity in ash fro... more A design study has been performed for a system that should measure the Cs-137 activity in ash from an incinerator. Radioactive ash, expected to consist of both Cs-134 and Cs-137, will be transported on a conveyor belt at 0.1 m/s. The objective of the counting system is to determine the Cs-137 activity and direct the ash to the correct stream after a diverter. The decision levels are ranging from 8000 to 400000 Bq/kg and the decision error should be as low as possible. The decision error depends on the total measurement uncertainty which depends on the counting statistics and the uncertainty in the efficiency of the geometry. For the low activity decision it is necessary to know the efficiency to be able to determine if the signal from the Cs-137 is above the minimum detectable activity and that it generates enough counts to reach the desired precision. For the higher activity decision the uncertainty of the efficiency needs to be understood to minimize decision errors. The total eff...
To validate the accuracy and precision of the Genie2000 Cascade Summing Correction method, over 8... more To validate the accuracy and precision of the Genie2000 Cascade Summing Correction method, over 800 archived measurements were made on calibrated sources (filter paper, 20cc liquid scintillation vial, 400 ml beaker and Marinelli beaker) containing cascading ( 88 Y and 60 Co) and non-cascading isotopes. These measurements used 133 different high purity germanium detectors that were characterized for use by the ISOCS/LabSOCS mathematical efficiency software. These detectors ranged in size from 10cc to 450cc (100% relative efficiency), and covered all types of Ge detectors. MCNP was used to calculate required peak-to-total efficiency calibrations. This study compared the Genie2000 cascade summing corrected results for the cascading isotope activities to the known activities. The analysis shows that the method is effective and accurate. The method appears to be valid for all sizes of detectors tested. Evaluation of the accuracy as a function of the amount of correction reveals a small s...
Radiological characterization in DD & ER projects is an important part of the project. When prope... more Radiological characterization in DD & ER projects is an important part of the project. When properly applied it can provide much needed information to better plan the project, to guide the progress of the remediation, to know when to stop remediating, and to prove officially that the job is complete. One of the more expensive radiological characterization tasks is the location and quantification of hidden or buried sources. Many samples must normally be taken for laboratory analysis, which is costly and takes much time. With the newly available InSitu gamma spectroscopy systems, this can often be done in the field. InSitu gamma spectroscopy avoids the dose and industrial hazard of extracting samples, avoids the necessity of packaging and transporting to fixed laboratories, gives results nearly immediately, and generates no waste. Reactors facilities [operating or shut down], Uranium processing facilities, NORM contamination sites, and weapons sites all have nuclides that are amenabl...
Canberra Industries, Inc. has designed a new truck monitoring system for a facility in Japan. The... more Canberra Industries, Inc. has designed a new truck monitoring system for a facility in Japan. The customer desires to separately quantify the Cs-137 and Cs-134 content of truck cargo entering and leaving a Waste Consolidation Area. The content of the trucks will be some combination of sand, soil, and vegetation with densities ranging from 0.3 g/cc - 1.6 g/cc. The typical weight of the trucks will be approximately 10 tons, but can vary between 4 and 20 tons. The system must be sensitive enough to detect 100 Bq/kg in 10 seconds (with less than 10% relative standard deviation) but still have enough dynamic range to measure 1,000,000 Bq/kg material. The system will be operated in an outdoor environment. Starting from these requirements, Canberra explored all aspects of the counting system in order to provide the customer with the optimized solution. The desire to separately quantify Cs-137 and Cs-134 favors the use of a spectroscopic system as a solution. Using the In Situ Object Counti...
In the process of decommissioning contaminated facilities, and in the conduct of normal operation... more In the process of decommissioning contaminated facilities, and in the conduct of normal operations involving radioactive material, it is frequently required to measure radioactivity in large containers such as 200 liter drums. For solid material, it is quite unusual for the radioactivity to be homogeneously distributed throughout the container. One way to derive the concentration of radioactivity within the container is to extract a sample for subsequent measurement in the laboratory. Another way is to use gamma spectroscopy and assay the entire container, or in-toto measurement. This paper examines the process of determining the best way to estimate the activity within the container, and gives quantitative estimates of measurement uncertainty for various conditions of radioactivity contained within 200 liter drums. When the contents of the container are not homogeneous, the sampling uncertainty is likely to be larger than the in-toto measurement uncertainty.
During the decommissioning of structures and the remediation of soil, material that is known or s... more During the decommissioning of structures and the remediation of soil, material that is known or suspected to be contaminated with radioactivity must be assayed. For many, if not most, of the cases, the radioactive material concentration can be determined or inferred by gamma spectroscopy. In most, if not all, of these cases, the radioactivity is not uniformly distributed. For these situations, is it better to perform in-toto measurements of the entire item, or is it better to extract a sample and analyze that sample? For the in-toto gamma spectroscopy measurement, the results will not be accurate unless the calibration method perfectly represents the measured item. And since the calibrations normally assume uniformly distributed radioactivity, any nonuniform distribution of radioactivity in the measured material will cause an error in the results. A mathematical program using probabilistic methods has been developed to estimate the uncertainty in in-toto gamma spectroscopy measureme...
The D&D of nuclear facilities will generate a large volume of pipes, structural beams, and column... more The D&D of nuclear facilities will generate a large volume of pipes, structural beams, and columns that are potentially contaminated. While some are indeed heavily contaminated and are best treated as radioactive waste in the traditional manner, many of these are likely to be clean. The problem is to economically prove that they are clean. Due to the nature of these items, traditional survey techniques involving manually checking all surfaces areas with a hand probe are impossible and/or quite expensive. Since these objects have been installed, used, and removed from operation, they have irregular shapes, are covered with paint or other debris, have protrusions, and have inaccessible inner surfaces. These characteristics all make alpha/beta assay very difficult. Canberra Industries has designed, manufactured, and tested the Mobile Internal/External Pipe Assessment System under a contract with FIU-HCET under the FETC/DOE program. The system has several unique features. Gamma detector...
During the operations of nuclear facilities and during the environmental remediation and decommis... more During the operations of nuclear facilities and during the environmental remediation and decommissioning of nuclear facilities, radioactive waste is generated which must be assayed. To save on labor and transportation costs, this material is commonly placed in large containers of typically several cubic meters in size [e.g. B-25]. The most common choices of assay are to either extract a representative sample of the contents for laboratory assay, or to use in-situ gamma spectroscopy of the total container. Both of these methods have strengths and weaknesses. InSitu methods determine container activity directly and typically quantify gamma emitters which are then correlated to total activity. Gamma measurement accuracy can suffer from an inadequate efficiency calibration, which can be caused by variations in container size, shape, matrix fill height, or matrix density, but primarily by non-homogeneous distribution of the radioactivity. Laboratory assay methods using a small sample ext...
Low level radioactive waste disposal is very expensive, especially when all of the handling, tran... more Low level radioactive waste disposal is very expensive, especially when all of the handling, transportation and documentation costs are included. However for most generators, a large fraction of this low level waste is not contaminated at all, or only slightly so. This paper describes the development and performance of a low level counter that is convenient to use, and that can accurately identify and quantify the radioactivity of any gamma emitter that can be placed in a 200 L (55-gal) container. These measurement results can be used to verify the absence of radioactivity at very low levels (10 nCi (370 Bq)/ sample), and to identify the nuclides and quantities present, while differentiating against natural radioactivity (Radium, Thorium, Potassium). These results can be used as part of a 10CFR20.302 waste stream exemption program, and thus allow significant savings and a less than one year payback at a typical nuclear power plant. The Q system is fully shielded to allow its use in ...
2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), 2013
Cerium Bromide scintillators (CeBr3) have received recent attention for gamma spectroscopy due to... more Cerium Bromide scintillators (CeBr3) have received recent attention for gamma spectroscopy due to its absence of internal background, promising resolution, short scintillation decay time, and good stopping power. We report on the production and characterization of LED stabilized probes with scintillator sizes of 3.7 cm × 3.7 cm (OD x Length) and 5.1 cm × 5.1 cm. Excellent stability versus temperature has been demonstrated from -20 to 50 °C. Modeling capability with MCNP and commercial efficiency codes (ISOCS) show excellent agreement with measured data. Comparisons of resolution performance, shielded and unshielded background data, and intrinsic efficiencies show that CeBr3 probes meet or exceed the performance off-the-shelf NaI:Tl and LaBr3:Ce detectors.
The ISOCS mathematical method developed by Canberra Industries is a well established technique fo... more The ISOCS mathematical method developed by Canberra Industries is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user inputs the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. Canberra is developing a customized efficiency optimization software, which is an extension of the ISOCS, known as "Advanced ISOCS" that varies the uncertain parameters and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, or FRAM, activities from multi-l...
In the process of decommissioning contaminated facilities, and in the conduct of normal operation... more In the process of decommissioning contaminated facilities, and in the conduct of normal operations involving radioactive material, it is frequently required to show that large areas of land are not contaminated, or if contaminated that the amount is below an acceptable level. However, it is quite rare for the radioactivity in the soil to be uniformly distributed. Rather it is generally in a few isolated and probably unknown locations. One way to ascertain the status of the land concentration is to take soil samples for subsequent measurement in the laboratory. Another way is to use in-situ gamma spectroscopy. In both cases, the non-uniform distribution of radioactivity can greatly compromise the accuracy of the assay, and makes uncertainty estimates much more complicated than simple propagation of counting statistics. This paper examines the process of determining the best way to estimate the activity on the tract of land, and gives quantitative estimates of measurement uncertainty ...
In situ gamma spectroscopy has been successfully used for decommissioning surveys and environment... more In situ gamma spectroscopy has been successfully used for decommissioning surveys and environmental remediation surveys for many years. With the recent advancements in technology of very portable and reliable Ge detectors, high quality digital MCAs, and mathematical efficiency calibration algorithms that are fast and accurate, this technology is now available to operating nuclear facilities. In situ gamma spectroscopy offers advantages over the traditional method of extracting a representative sample, transporting it to a laboratory, and then preparing the sample for counting. Getting the sample is the major problem. Some samples are physically difficult to obtain (subsurface soil, concrete, activated materials, material inside pipes or tanks, etc.). Some samples are physically dangerous to take (very radioactive items like resin beads, concrete cores or steel coupons, pressurized gases, hot water, corrosive or toxic items). Since in situ spectroscopy is a non-contact process, and s...
Gamma ray spectrometry using High Purity Germanium (HPGe) detectors is commonly employed in assay... more Gamma ray spectrometry using High Purity Germanium (HPGe) detectors is commonly employed in assaying radioactive waste streams from a variety of sources: nuclear power plants, Department of Energy (DOE) laboratories, medical facilities, decontamination and decommissioning activities etc. The radioactive material is typically packaged in boxes or drums (for e.g. B-25 boxes or 208 liter drums) and assayed to identify and quantify radionuclides. Depending on the origin of the waste stream, the radionuclides could be special nuclear materials (SNM), fission products, or activation products. Efficiency calibration of the measurement geometry is a critical step in the achieving accurate quantification of radionuclide content. Due to the large size of the waste items, it is impractical and expensive to manufacture gamma ray standard sources for performing a measurement based calibration. For well over a decade, mathematical efficiency methods such as those in Canberra's In Situ Object ...
The ISOCS mathematical method developed by Canberra Industries is a well established technique fo... more The ISOCS mathematical method developed by Canberra Industries is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user inputs the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. Canberra is developing a customized efficiency optimization software, which is an extension of the ISOCS, known as “Advanced ISOCS” that varies the uncertain parameters and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, or FRAM, activities from multi-line nuclid...
Large NaI detectors are commonly used in gamma measurement systems where nuclide identification a... more Large NaI detectors are commonly used in gamma measurement systems where nuclide identification and quantification is desired. These systems are used to measure people, soil, drums, boxes, animals, and other things. For quantification, an efficiency calibration must be performed, which becomes increasingly difficult as the sources become large and complicated. Mathematical techniques can be quite useful here, if they are easy enough to use, and accurate enough for the application. A series of experiments was performed to show how accurately the efficiency of large (3”x5”x16”) rectangular NaI detectors can be computed with techniques that could be implemented within the commercially available ISOCS mathematical efficiency calibration software. This software assumes that the detector response function is cylindrically symmetric, which certainly isn’t the case here. But, perhaps it is good enough for the applications for which these large rectangular detectors are commonly used. A seri...
wmsym.org
A large variety of non-destructive assay (NDA) systems have been developed for the analysis of wa... more A large variety of non-destructive assay (NDA) systems have been developed for the analysis of waste containers by passive gamma-ray spectroscopy. Examples of such systems include Segmented Gamma Scanners (SGS), Q 2-style drum counters, Large Box Counters, and far-field measurement systems. The calibration of these systems typically involves the purchase and construction of "calibration" containers that are to varying degree representative of the items to be assayed. Typically these "calibration" containers represent idealizations of the waste stream with homogenized matrix materials and pseudouniform source distributions. But, for complete and correct calibrations, these containers must span the operational range of the system, and consequently include extreme and difficult configurations of matrix, density and source distribution. The NDA systems themselves typically have multiple configurations to deal with different kinds of items, and each configuration must be calibrated separately, often with different calibration sources. If the system is changed or modified, it must subsequently be recalibrated experimentally. The accuracy of such a calibration is typically estimated by performing a limited number of "worst-case" scenarios to establish the bounds of the Total Measurement Uncertainty (TMU). In its entirety, the calibration and uncertainty estimation of an NDA system represents a significant up-front expense. Alternatives exist to the source-based calibrations of NDA systems. Among these alternatives is the mathematical modeling of the efficiency response of a given system to a particular waste configuration. In this situation, the system is calibrated using physically-relevant models of the gamma-ray response, with a relatively small number of validation measurements performed to demonstrate proper operation of the system and establish traceability to national standards. Due to the complexity of NDA systems and waste streams, purely analytically models are typically not feasible, but semi-analytical Monte-Carlo approaches based on the fundamental principles of gamma-ray interactions have proven to be very successful. These semi-analytical approaches are sufficiently versatile to allow the modeling of general waste stream configurations. Systems can be quickly adapted to changing waste streams or detector configurations. Not only can the measurement limits of the TMU be accurately estimated with semianalytical techniques, but its functional form can be properly modeled to allow a more accurate assessment of the entire waste stream. In this paper, we will present a survey of instruments including SGS, Box Counter, and far-field systems that have been calibrated using semi-analytical mathematical models. We will discuss experiences in calibration techniques, modeling of the TMU, and recent advances that further enhance the capabilities of such approaches.
Applied Radiation and Isotopes, 2009
An MCNP model of a co-axial HPGe detector, defined by the specification sheet and without paramet... more An MCNP model of a co-axial HPGe detector, defined by the specification sheet and without parameter optimization, was used to assess practicality for efficiency characterization and complex spectra simulation. Simulated efficiencies, with and without Gaussian energy broadening, were compared against an experimental calibration for a standard counting geometry. Results show that this minimal detector model predicted efficiencies within 6% of experimental values at energies above 100 keV, while including energy broadening offered little improvement. This work shows that extensive detector characterization and optimization of parameters is not absolutely necessary, thereby reducing the experimental burden associated with detector modeling for many applications.
Ｎｕｃｌ Ｉｎｓｔｒｕｍ Ｍｅｔｈｏｄｓ Ｐｈｙｓ Ｒｅｓ Ｓｅｃｔ Ａ Ａｃｃｅｌ Ｓｐｅｃｔｒｏｍｅｔｅｒｓ Ｄｅｔｅｃｔ Ａｓｓｏｃ, 1999
A design study has been performed for a system that should measure the Cs-137 activity in ash fro... more A design study has been performed for a system that should measure the Cs-137 activity in ash from an incinerator. Radioactive ash, expected to consist of both Cs-134 and Cs-137, will be transported on a conveyor belt at 0.1 m/s. The objective of the counting system is to determine the Cs-137 activity and direct the ash to the correct stream after a diverter. The decision levels are ranging from 8000 to 400000 Bq/kg and the decision error should be as low as possible. The decision error depends on the total measurement uncertainty which depends on the counting statistics and the uncertainty in the efficiency of the geometry. For the low activity decision it is necessary to know the efficiency to be able to determine if the signal from the Cs-137 is above the minimum detectable activity and that it generates enough counts to reach the desired precision. For the higher activity decision the uncertainty of the efficiency needs to be understood to minimize decision errors. The total eff...
To validate the accuracy and precision of the Genie2000 Cascade Summing Correction method, over 8... more To validate the accuracy and precision of the Genie2000 Cascade Summing Correction method, over 800 archived measurements were made on calibrated sources (filter paper, 20cc liquid scintillation vial, 400 ml beaker and Marinelli beaker) containing cascading ( 88 Y and 60 Co) and non-cascading isotopes. These measurements used 133 different high purity germanium detectors that were characterized for use by the ISOCS/LabSOCS mathematical efficiency software. These detectors ranged in size from 10cc to 450cc (100% relative efficiency), and covered all types of Ge detectors. MCNP was used to calculate required peak-to-total efficiency calibrations. This study compared the Genie2000 cascade summing corrected results for the cascading isotope activities to the known activities. The analysis shows that the method is effective and accurate. The method appears to be valid for all sizes of detectors tested. Evaluation of the accuracy as a function of the amount of correction reveals a small s...
Radiological characterization in DD & ER projects is an important part of the project. When prope... more Radiological characterization in DD & ER projects is an important part of the project. When properly applied it can provide much needed information to better plan the project, to guide the progress of the remediation, to know when to stop remediating, and to prove officially that the job is complete. One of the more expensive radiological characterization tasks is the location and quantification of hidden or buried sources. Many samples must normally be taken for laboratory analysis, which is costly and takes much time. With the newly available InSitu gamma spectroscopy systems, this can often be done in the field. InSitu gamma spectroscopy avoids the dose and industrial hazard of extracting samples, avoids the necessity of packaging and transporting to fixed laboratories, gives results nearly immediately, and generates no waste. Reactors facilities [operating or shut down], Uranium processing facilities, NORM contamination sites, and weapons sites all have nuclides that are amenabl...
Canberra Industries, Inc. has designed a new truck monitoring system for a facility in Japan. The... more Canberra Industries, Inc. has designed a new truck monitoring system for a facility in Japan. The customer desires to separately quantify the Cs-137 and Cs-134 content of truck cargo entering and leaving a Waste Consolidation Area. The content of the trucks will be some combination of sand, soil, and vegetation with densities ranging from 0.3 g/cc - 1.6 g/cc. The typical weight of the trucks will be approximately 10 tons, but can vary between 4 and 20 tons. The system must be sensitive enough to detect 100 Bq/kg in 10 seconds (with less than 10% relative standard deviation) but still have enough dynamic range to measure 1,000,000 Bq/kg material. The system will be operated in an outdoor environment. Starting from these requirements, Canberra explored all aspects of the counting system in order to provide the customer with the optimized solution. The desire to separately quantify Cs-137 and Cs-134 favors the use of a spectroscopic system as a solution. Using the In Situ Object Counti...
In the process of decommissioning contaminated facilities, and in the conduct of normal operation... more In the process of decommissioning contaminated facilities, and in the conduct of normal operations involving radioactive material, it is frequently required to measure radioactivity in large containers such as 200 liter drums. For solid material, it is quite unusual for the radioactivity to be homogeneously distributed throughout the container. One way to derive the concentration of radioactivity within the container is to extract a sample for subsequent measurement in the laboratory. Another way is to use gamma spectroscopy and assay the entire container, or in-toto measurement. This paper examines the process of determining the best way to estimate the activity within the container, and gives quantitative estimates of measurement uncertainty for various conditions of radioactivity contained within 200 liter drums. When the contents of the container are not homogeneous, the sampling uncertainty is likely to be larger than the in-toto measurement uncertainty.
During the decommissioning of structures and the remediation of soil, material that is known or s... more During the decommissioning of structures and the remediation of soil, material that is known or suspected to be contaminated with radioactivity must be assayed. For many, if not most, of the cases, the radioactive material concentration can be determined or inferred by gamma spectroscopy. In most, if not all, of these cases, the radioactivity is not uniformly distributed. For these situations, is it better to perform in-toto measurements of the entire item, or is it better to extract a sample and analyze that sample? For the in-toto gamma spectroscopy measurement, the results will not be accurate unless the calibration method perfectly represents the measured item. And since the calibrations normally assume uniformly distributed radioactivity, any nonuniform distribution of radioactivity in the measured material will cause an error in the results. A mathematical program using probabilistic methods has been developed to estimate the uncertainty in in-toto gamma spectroscopy measureme...
The D&D of nuclear facilities will generate a large volume of pipes, structural beams, and column... more The D&D of nuclear facilities will generate a large volume of pipes, structural beams, and columns that are potentially contaminated. While some are indeed heavily contaminated and are best treated as radioactive waste in the traditional manner, many of these are likely to be clean. The problem is to economically prove that they are clean. Due to the nature of these items, traditional survey techniques involving manually checking all surfaces areas with a hand probe are impossible and/or quite expensive. Since these objects have been installed, used, and removed from operation, they have irregular shapes, are covered with paint or other debris, have protrusions, and have inaccessible inner surfaces. These characteristics all make alpha/beta assay very difficult. Canberra Industries has designed, manufactured, and tested the Mobile Internal/External Pipe Assessment System under a contract with FIU-HCET under the FETC/DOE program. The system has several unique features. Gamma detector...
During the operations of nuclear facilities and during the environmental remediation and decommis... more During the operations of nuclear facilities and during the environmental remediation and decommissioning of nuclear facilities, radioactive waste is generated which must be assayed. To save on labor and transportation costs, this material is commonly placed in large containers of typically several cubic meters in size [e.g. B-25]. The most common choices of assay are to either extract a representative sample of the contents for laboratory assay, or to use in-situ gamma spectroscopy of the total container. Both of these methods have strengths and weaknesses. InSitu methods determine container activity directly and typically quantify gamma emitters which are then correlated to total activity. Gamma measurement accuracy can suffer from an inadequate efficiency calibration, which can be caused by variations in container size, shape, matrix fill height, or matrix density, but primarily by non-homogeneous distribution of the radioactivity. Laboratory assay methods using a small sample ext...
Low level radioactive waste disposal is very expensive, especially when all of the handling, tran... more Low level radioactive waste disposal is very expensive, especially when all of the handling, transportation and documentation costs are included. However for most generators, a large fraction of this low level waste is not contaminated at all, or only slightly so. This paper describes the development and performance of a low level counter that is convenient to use, and that can accurately identify and quantify the radioactivity of any gamma emitter that can be placed in a 200 L (55-gal) container. These measurement results can be used to verify the absence of radioactivity at very low levels (10 nCi (370 Bq)/ sample), and to identify the nuclides and quantities present, while differentiating against natural radioactivity (Radium, Thorium, Potassium). These results can be used as part of a 10CFR20.302 waste stream exemption program, and thus allow significant savings and a less than one year payback at a typical nuclear power plant. The Q system is fully shielded to allow its use in ...
2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), 2013
Cerium Bromide scintillators (CeBr3) have received recent attention for gamma spectroscopy due to... more Cerium Bromide scintillators (CeBr3) have received recent attention for gamma spectroscopy due to its absence of internal background, promising resolution, short scintillation decay time, and good stopping power. We report on the production and characterization of LED stabilized probes with scintillator sizes of 3.7 cm × 3.7 cm (OD x Length) and 5.1 cm × 5.1 cm. Excellent stability versus temperature has been demonstrated from -20 to 50 °C. Modeling capability with MCNP and commercial efficiency codes (ISOCS) show excellent agreement with measured data. Comparisons of resolution performance, shielded and unshielded background data, and intrinsic efficiencies show that CeBr3 probes meet or exceed the performance off-the-shelf NaI:Tl and LaBr3:Ce detectors.