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Burns, Joseph R.; Petrovic, Bojan; Chandler, David; Terrani, Kurt A.
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Funding organisation: USDOE Laboratory Directed Research and Development (LDRD) Program (United States)2018
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Funding organisation: USDOE Laboratory Directed Research and Development (LDRD) Program (United States)2018
AbstractAbstract
[en] Additive manufacturing is under investigation as a novel method of fabricating the control elements (CEs) of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory with greater simplicity, eliminating numerous highly complex fabrication steps and thereby offering potential for significant savings in cost, time, and effort. This process yields a unique CE design with lumped absorbers, a departure from traditionally manufactured CEs with uniformly distributed absorbing material. Here, this study undertakes a neutronics analysis of the impact of additively manufactured CEs on the HFIR core physics, seeking preliminary assessment of the feasibility of their practical use. The results of the MCNP transport simulations reveal changes in the HFIR reactor physics arising from geometric and nuclear effects. Absorber lumping in the discrete CEs yields a large volume of unpoisoned material that is not present in the homogeneous design, in turn yielding increases in free thermal flux in the CE absorbing regions and their immediate vicinity. The availability of additional free thermal neutrons in the core yields an increase in fission rate density in the fuel closest to the CEs and a corresponding increase in neutron multiplication on the order of 100 pcm. The absorption behavior exhibited by the discrete CEs is markedly different from the homogeneous CEs due to several competing effects. Self-shielding arising from absorber lumping acts to reduce the effective absorption cross section of the discrete CEs, but this effect is offset by geometric and spectral effects. The operational performance of the discrete CEs is found to be comparable to the homogeneous CEs, with only limited deficiencies in reactivity worth that are expected to be operationally recoverable via limited adjustment of the CE positions and withdrawal rate. On the whole, these results indicate that the discrete CEs perform reasonably similarly to the homogeneous CEs and appear feasible for application in HFIR. In conclusion, the physical phenomena identified in this study provide valuable background for follow-up design studies.
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Source
OSTIID--1423086; AC05-00OR22725; Available from https://www.osti.gov/pages/biblio/1423086; DOE Accepted Manuscript full text, or the publishers Best Available Version will be available free of charge after the embargo period; Country of input: United States
Record Type
Journal Article
Journal
Annals of Nuclear Energy (Oxford); ISSN 0306-4549;
; v. 115(C); p. 403-414

Country of publication
BARYONS, ELEMENTARY PARTICLES, ENRICHED URANIUM REACTORS, FERMIONS, HADRONS, IRRADIATION REACTORS, ISOTOPE PRODUCTION REACTORS, NEUTRONS, NUCLEONS, PHYSICS, REACTOR COMPONENTS, REACTORS, RESEARCH AND TEST REACTORS, RESEARCH REACTORS, TANK TYPE REACTORS, TEST FACILITIES, TEST REACTORS, THERMAL REACTORS, WATER COOLED REACTORS, WATER MODERATED REACTORS
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