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Mennerdahl, Dennis

Publications and source records attributed to Mennerdahl, Dennis.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Benchmarking of the Updated Resolved Resonance Region Evaluations of Copper

A new resolved resonance region (RRR) evaluation for the two naturally occurring isotopes of copper, {sup 63}Cu and {sup 65}Cu was performed at Oak Ridge National Laboratory (ORNL), and the benchmarking results based on the four highly enriched uranium (HEU), intermediate spectrum, copper-reflected Zeus experiments were presented in June 2014. Since then, two significant updates to the evaluations have been performed: first, the data for the experimental measurement of the capture cross section between 220 keV and 300 keV were renormalized and the resonance parameters were refitted. Second, the angular distribution of elastic scattering initially reported in point-wise form in File 4 of the ENDF file format with high fidelity was significantly reduced in size to allow for better computer storage. Twenty-seven criticality safety benchmarks from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) were calculated using these updated resolved resonance region evaluations for the two isotopes of copper. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Just a word or two: Nuclear criticality - 14376

What's in a name? The purpose is to demonstrate a need for better definitions, how to achieve that and how to use them. A controversial definition, nuclear criticality, and implementation of available directives for preparation of standards have been selected for illustration. The definitions of bias and a few other terms are discussed briefly. Reliable communication, supported by established standards, is essential to (nuclear) criticality safety. Sufficiently accurate, without necessarily being scientific, and consistent definitions are required. A term is the name of a concept (a general idea or understanding of something). A definition is a link between a term and a concept. A concept may be complex but the term and the concept description should be exchangeable in the text they are used. They have identical meanings. Established standards include ANSI/ANS and ISO consensus standards, the IAEA Safety Glossary and the IAEA Transport Regulations. The report LA-11627-MS and the associated ANS Glossary of Terms in Nuclear Science and Technology are sources for the consensus standards. In the spring of 2015, ISO approved a new terminology standard for the nuclear fuel cycle (excluding reactors). In response to an ISO member state proposal, a definition of nuclear criticality, based on the IAEA Safety Glossary, was added at the very last moment by the high-level (not criticality safety only) working group preparing the new standard. The ISO criticality safety working group, after some discussion, did not provide any comment on a nuclear criticality definition to the terminology working group. As a concept, nuclear criticality has a very precise 'reactor physics' meaning. Criticality, as a term related to fission chain reactions, is used in some contexts to cover less precise meanings ('loosely') or as a constituent of a combined expression for rather different concepts. Criticality may thus be loosely used to mean 'criticality or something worse', a criticality accident, a different concept with is own definition. The new definition proposed by the ISO member state was based on such use. What does fraction of a critical mass, e.g. 40%, mean if the critical mass has an unspecified k{sub eff} value larger than unity? Bias, typically an estimated deviation from the correct value in a measured or a calculated value, is sometimes used to mean the opposite concept, bias correction. That is a direct cause of safety concern since the conflicting concepts may be used in the same document or evaluation. (author)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Benchmark On Sensitivity Calculation (Phase III)

The sensitivities of the keff eigenvalue to neutron cross sections have become commonly used in similarity studies and as part of the validation algorithm for criticality safety assessments. To test calculations of the sensitivity coefficients, a benchmark study (Phase III) has been established by the OECD-NEA/WPNCS/EG UACSA (Expert Group on Uncertainty Analysis for Criticality Safety Assessment). This paper presents some sensitivity results generated by the benchmark participants using various computational tools based upon different computational methods: SCALE/TSUNAMI-3D and -1D, MONK, APOLLO2-MORET 5, DRAGON-SUSD3D and MMKKENO. The study demonstrates the performance of the tools. It also illustrates how model simplifications impact the sensitivity results and demonstrates the importance of 'implicit' (self-shielding) sensitivities. This work has been a useful step towards verification of the existing and developed sensitivity analysis methods.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗