Criticality experiments with 235U (metal and hydride) and 239Pu (metal) were performed during the... more Criticality experiments with 235U (metal and hydride) and 239Pu (metal) were performed during the Manhattan Project. Results from these experiments provided necessary information for the success of the Manhattan Project [LA-1033 to LA-1036 (1947), LA-02532-MS V I (1961), and Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years, 1943–1945 (1993)]. These experiments have been previously described in compilations made after the Manhattan Project, but those works are either lacking in technical details or are not publicly available. This work aims to provide detailed information while showcasing the enduring impact of these experiments 75 years after they were performed. Furthermore, we use modern computational methods embodied in the MCNP6® code and ENDF data to analyze and interpret these historic measurements. The world’s first four criticality accidents are also discussed, as lessons learned from these helped shape the field of criticality experiments.
The National Criticality Experiments Research Center (NCERC) located at the Device Assembly Facil... more The National Criticality Experiments Research Center (NCERC) located at the Device Assembly Facility (DAF) at the Nevada National Security Site (NNSS) and operated by Los Alamos National Laboratory (LANL) is home to four critical assemblies which are used to support of range of missions, including nuclear criticality safety and nuclear nonproliferation. Additionally, subcritical systems can also be assembled at NCERC. NCERC is providing critical and subcritical experiments valuable to the nuclear data community and experiments performed at NCERC are often published as benchmarks in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. This manuscript will give a broad overview of recent experiments performed at NCERC, upcoming experiments, and why integral measurements are important and useful to the nuclear data community. The four critical assemblies are GODIVA IV, FLATTOP, COMET, and PLANET. GODIVA IV is a cylindrical metal fast burst reactor, the f...
The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of ... more The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kW(thermal) Kilopower space reactor. This paper presents results from the KRUSTY warm critical experiments, which were completed prior to the final system test. The first set of criticals comprised cold or zero-power criticals; i.e., the core was not heated by fission power. These were followed by three warm criticals, where fission power heated the core to 200°C, 300°C, and 450°C, respectively. These criticals provided the data, confidence, and regulatory framework that were needed to proceed with the KRUSTY nuclear system test. The criticals also provided valuable data for the benchmarking of codes applicable to all nuclear systems. Finally, a comparison of KRUSTY results to pretest predictions is provided, and overall, the models matched the experimental results very closely.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The view and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ' This study has adopted highly conservative positions with respect to both nuclear and geologic assumptions. A more realistic treatment of nuclear assumptions is expected to severely constrain the possibilities for criticality and autocatalytic behavior. The probabilities and even the possibilities of the several geologic and chemical phenomena and actions that must occur before a criticality study is even appropriate are not evaluated in this paper. These chemical and geologic considerationsAstudies underway, see Ref. 5) may eliminate the problem and the need for a criticality and dynamic study completely.
First, I would like to express my gratitude to Glenn Brunson. I believe he derives pleasure from ... more First, I would like to express my gratitude to Glenn Brunson. I believe he derives pleasure from helping others, and I feel very fortunate to have collaborated and learned from him. He played a major role deciding what type of detection system and analysis that should be performed in this experiment. The many discussion I had with Glenn were both educational and enjoyable. Many people provided time and helped operate Godiva IV. I would like to mention the great support provided by the Crew Chief Ken Butterfield. Ken was instrumental during the collection of data. He not only operated Godiva, but provided many stimulating discussions. He also helped fine-tune the retrieval system. My thanks go to Rene Sanchez and Guy h o n e. It was Rene Sanchez who fiunished the idea to measure the delayed neutrons for Np-237. Rene provided optimism and enthusiasm. Guy h o n e and Ray Hastings helped in many aspects of this experiment that are too numerous to mention. Many thanks go to the design and shop teams led by Charlene Cappiello. Charlene has a great group of people and they were very supportive throughout the experiment. My gratitude goes toward Rick Paternoster for his support and for providing me the opportunity to perform this experiment. Finally, I would like to thank my advisors Dr. Eric Haskin and Dr. Robert Busch. I appreciate their hard work and dedication. They provided insightful suggestions for the improvement of my project and manuscript. It has been a great pleasure having them as advisors in both my master and doctorate studies. There are many people who have contributed to this experiment. If I have failed to mention you, it is for lack of space and not lack of gratitude. DISCLAIMER Portions of this document may be ilkgiile in electronic image products. Images are produced fmm the best available original d O m 5 t .
The following information is to be distributed for review as part of the Department of Energy's N... more The following information is to be distributed for review as part of the Department of Energy's Nuclear Criticality Safety Program (NCSP) Critical Experiment Design (CED) process requirements. This Research Note is to serve as documentation for IER 299 CED phase 1 preliminary design which is the information that represents the preliminary planning, design, and analysis for the KRUSTY experimental measurements to be executed to obtain the requested data.
Module 10 Reactor Physics LA-UR-21 Unclassified Goals • Students will gain a understanding of som... more Module 10 Reactor Physics LA-UR-21 Unclassified Goals • Students will gain a understanding of some basic reactor physics concepts, which will prepare them for learning more detailed concepts about the design and operations of the experiments performed using the NCERC critical assemblies.
Transactions of the American Nuclear Society, 1996
Formation of critical and possibly autocatalytic mixtures of weapons-grade plutonium, Nevada tuff... more Formation of critical and possibly autocatalytic mixtures of weapons-grade plutonium, Nevada tuff, and water in an underground repository has been postulated by Bowman and Vernneri. The objective of this work is to examine the possibility that a nuclear explosion in the {open_quotes}range of kilotons{close_quotes} or {open_quotes}hundreds of tons TNT equivalent{close_quotes} could occur from the formation of a {open_quotes}worst-case{close_quotes} autocatalytic mixture of plutonium, Nevada tuff, and water. Once this is done, other realistic criticality safety issues dealing with the design of the repository can be the main focus of the work for criticality experts. This work does not examine the probability of formation of the critical mixtures of plutonium, Nevada tuff, and water in a repository setting. The authors accept, for the purpose of this work, the assumptions of formation given by Bowman and Venneri. They examine the dynamic behavior of these systems using what they consi...
An experiment has been performed combining highly enriched uranium, a hydrogenous moderator (poly... more An experiment has been performed combining highly enriched uranium, a hydrogenous moderator (polyethylene), and concrete. The purpose of the experiment was to provide additional criticality data that can be used to verify and validate criticality safety evaluations in support of the decommissioning of nuclear facilities throughout the Department of Energy complex. In this experiment, criticality was observed as a function time due to the curing and drying processes that occurred in the concrete.
Critical experiments are carried out in order to validate, improve, and benchmark the extensive d... more Critical experiments are carried out in order to validate, improve, and benchmark the extensive data calculations available. A series of such experiments was performed at the Los Alamos Criticality Experiments Facility. These experiments were performed to provide criticality safety data for waste matrix materials. These critical experiments were fueled with highly enriched uranium, moderated and reflected with polyethylene, and mixed with silicon dioxide (SiOâ), aluminum (Al), magnesium oxide (MgO), and gadolinium (Gd). The uncertainties affecting the experiment were divided into three broad categories: mass measurement, geometry, and material composition. Each category is considered in turn, and then the total experimental uncertainty is derived. All four experiments had a measured k{sub eff} of 1.001. The sensitivity analyses of these critical experiments yielded uncertainties in the measured k{sub eff} of {+-}0.0026 for SiOâ, {+-}0.0026 for Al, {+-}0.0021 for MgO, and {+-}0.0029 for Gd. These experiments were judged to be of benchmark quality.
The delayed neutron activity resulting from the fast induced fission of ²³âµU and ²³â·Np ha... more The delayed neutron activity resulting from the fast induced fission of ²³âµU and ²³â·Np has been studied. The six-group decay constants, relative abundances, and absolute yield of delayed neutrons from fast fission of ²³âµU and ²³â·Np were measured using the Godiva IV fast assembly at the Los Alamos Critical Experiments Facility. The absolute yield measured for ²³âµU was 0.0163 {+-}
Criticality experiments with 235U (metal and hydride) and 239Pu (metal) were performed during the... more Criticality experiments with 235U (metal and hydride) and 239Pu (metal) were performed during the Manhattan Project. Results from these experiments provided necessary information for the success of the Manhattan Project [LA-1033 to LA-1036 (1947), LA-02532-MS V I (1961), and Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years, 1943–1945 (1993)]. These experiments have been previously described in compilations made after the Manhattan Project, but those works are either lacking in technical details or are not publicly available. This work aims to provide detailed information while showcasing the enduring impact of these experiments 75 years after they were performed. Furthermore, we use modern computational methods embodied in the MCNP6® code and ENDF data to analyze and interpret these historic measurements. The world’s first four criticality accidents are also discussed, as lessons learned from these helped shape the field of criticality experiments.
The National Criticality Experiments Research Center (NCERC) located at the Device Assembly Facil... more The National Criticality Experiments Research Center (NCERC) located at the Device Assembly Facility (DAF) at the Nevada National Security Site (NNSS) and operated by Los Alamos National Laboratory (LANL) is home to four critical assemblies which are used to support of range of missions, including nuclear criticality safety and nuclear nonproliferation. Additionally, subcritical systems can also be assembled at NCERC. NCERC is providing critical and subcritical experiments valuable to the nuclear data community and experiments performed at NCERC are often published as benchmarks in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. This manuscript will give a broad overview of recent experiments performed at NCERC, upcoming experiments, and why integral measurements are important and useful to the nuclear data community. The four critical assemblies are GODIVA IV, FLATTOP, COMET, and PLANET. GODIVA IV is a cylindrical metal fast burst reactor, the f...
The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of ... more The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kW(thermal) Kilopower space reactor. This paper presents results from the KRUSTY warm critical experiments, which were completed prior to the final system test. The first set of criticals comprised cold or zero-power criticals; i.e., the core was not heated by fission power. These were followed by three warm criticals, where fission power heated the core to 200°C, 300°C, and 450°C, respectively. These criticals provided the data, confidence, and regulatory framework that were needed to proceed with the KRUSTY nuclear system test. The criticals also provided valuable data for the benchmarking of codes applicable to all nuclear systems. Finally, a comparison of KRUSTY results to pretest predictions is provided, and overall, the models matched the experimental results very closely.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The view and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ' This study has adopted highly conservative positions with respect to both nuclear and geologic assumptions. A more realistic treatment of nuclear assumptions is expected to severely constrain the possibilities for criticality and autocatalytic behavior. The probabilities and even the possibilities of the several geologic and chemical phenomena and actions that must occur before a criticality study is even appropriate are not evaluated in this paper. These chemical and geologic considerationsAstudies underway, see Ref. 5) may eliminate the problem and the need for a criticality and dynamic study completely.
First, I would like to express my gratitude to Glenn Brunson. I believe he derives pleasure from ... more First, I would like to express my gratitude to Glenn Brunson. I believe he derives pleasure from helping others, and I feel very fortunate to have collaborated and learned from him. He played a major role deciding what type of detection system and analysis that should be performed in this experiment. The many discussion I had with Glenn were both educational and enjoyable. Many people provided time and helped operate Godiva IV. I would like to mention the great support provided by the Crew Chief Ken Butterfield. Ken was instrumental during the collection of data. He not only operated Godiva, but provided many stimulating discussions. He also helped fine-tune the retrieval system. My thanks go to Rene Sanchez and Guy h o n e. It was Rene Sanchez who fiunished the idea to measure the delayed neutrons for Np-237. Rene provided optimism and enthusiasm. Guy h o n e and Ray Hastings helped in many aspects of this experiment that are too numerous to mention. Many thanks go to the design and shop teams led by Charlene Cappiello. Charlene has a great group of people and they were very supportive throughout the experiment. My gratitude goes toward Rick Paternoster for his support and for providing me the opportunity to perform this experiment. Finally, I would like to thank my advisors Dr. Eric Haskin and Dr. Robert Busch. I appreciate their hard work and dedication. They provided insightful suggestions for the improvement of my project and manuscript. It has been a great pleasure having them as advisors in both my master and doctorate studies. There are many people who have contributed to this experiment. If I have failed to mention you, it is for lack of space and not lack of gratitude. DISCLAIMER Portions of this document may be ilkgiile in electronic image products. Images are produced fmm the best available original d O m 5 t .
The following information is to be distributed for review as part of the Department of Energy's N... more The following information is to be distributed for review as part of the Department of Energy's Nuclear Criticality Safety Program (NCSP) Critical Experiment Design (CED) process requirements. This Research Note is to serve as documentation for IER 299 CED phase 1 preliminary design which is the information that represents the preliminary planning, design, and analysis for the KRUSTY experimental measurements to be executed to obtain the requested data.
Module 10 Reactor Physics LA-UR-21 Unclassified Goals • Students will gain a understanding of som... more Module 10 Reactor Physics LA-UR-21 Unclassified Goals • Students will gain a understanding of some basic reactor physics concepts, which will prepare them for learning more detailed concepts about the design and operations of the experiments performed using the NCERC critical assemblies.
Transactions of the American Nuclear Society, 1996
Formation of critical and possibly autocatalytic mixtures of weapons-grade plutonium, Nevada tuff... more Formation of critical and possibly autocatalytic mixtures of weapons-grade plutonium, Nevada tuff, and water in an underground repository has been postulated by Bowman and Vernneri. The objective of this work is to examine the possibility that a nuclear explosion in the {open_quotes}range of kilotons{close_quotes} or {open_quotes}hundreds of tons TNT equivalent{close_quotes} could occur from the formation of a {open_quotes}worst-case{close_quotes} autocatalytic mixture of plutonium, Nevada tuff, and water. Once this is done, other realistic criticality safety issues dealing with the design of the repository can be the main focus of the work for criticality experts. This work does not examine the probability of formation of the critical mixtures of plutonium, Nevada tuff, and water in a repository setting. The authors accept, for the purpose of this work, the assumptions of formation given by Bowman and Venneri. They examine the dynamic behavior of these systems using what they consi...
An experiment has been performed combining highly enriched uranium, a hydrogenous moderator (poly... more An experiment has been performed combining highly enriched uranium, a hydrogenous moderator (polyethylene), and concrete. The purpose of the experiment was to provide additional criticality data that can be used to verify and validate criticality safety evaluations in support of the decommissioning of nuclear facilities throughout the Department of Energy complex. In this experiment, criticality was observed as a function time due to the curing and drying processes that occurred in the concrete.
Critical experiments are carried out in order to validate, improve, and benchmark the extensive d... more Critical experiments are carried out in order to validate, improve, and benchmark the extensive data calculations available. A series of such experiments was performed at the Los Alamos Criticality Experiments Facility. These experiments were performed to provide criticality safety data for waste matrix materials. These critical experiments were fueled with highly enriched uranium, moderated and reflected with polyethylene, and mixed with silicon dioxide (SiOâ), aluminum (Al), magnesium oxide (MgO), and gadolinium (Gd). The uncertainties affecting the experiment were divided into three broad categories: mass measurement, geometry, and material composition. Each category is considered in turn, and then the total experimental uncertainty is derived. All four experiments had a measured k{sub eff} of 1.001. The sensitivity analyses of these critical experiments yielded uncertainties in the measured k{sub eff} of {+-}0.0026 for SiOâ, {+-}0.0026 for Al, {+-}0.0021 for MgO, and {+-}0.0029 for Gd. These experiments were judged to be of benchmark quality.
The delayed neutron activity resulting from the fast induced fission of ²³âµU and ²³â·Np ha... more The delayed neutron activity resulting from the fast induced fission of ²³âµU and ²³â·Np has been studied. The six-group decay constants, relative abundances, and absolute yield of delayed neutrons from fast fission of ²³âµU and ²³â·Np were measured using the Godiva IV fast assembly at the Los Alamos Critical Experiments Facility. The absolute yield measured for ²³âµU was 0.0163 {+-}
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