Simulated Rossi-alpha analysis of an asymmetrically coupled bare metal HEU reactor system
- Department of Mechanical Engineering, University of Nevada, Las Vegas (United States)
The predictive capabilities of MCNP6 for neutron noise experiments are shown in a comparison to the results of a series of Rossi-alpha measurements performed by J. Mihalczo utilizing a coupled set of symmetrical bare HEU (high enrichment uranium) cylinders. The results from the ptrac simulations agree well with the historical measured values. A series of case studies were conducted to study the effects of geometrical asymmetry in the coupling between two bare metal HEU cylinders. The difficulty in observing such systems is due in part to the inability to determine the individual coupling coefficients from measurement: unlike the symmetrical cases, only the product of the values can be obtained. A method is proposed utilizing MCNP6 tally ratios to separate the coupling coefficients for such systems. This work provides insight into the behavior of asymmetrically-coupled systems as the separation distance between the two cores is changed and also as the asymmetry is increased. As the asymmetry increases, both the slower and the faster observable prompt neutron decay constants increase in magnitude. The coupling time constants are determined from the measured decay constants. As the separation distance increases, both coupling coefficients decrease as expected. Based on these findings, an effective computational method utilizing MCNP6 and the Rossi-alpha technique can be applied to the prediction of asymmetrical coupled system measurements. (authors)
- Research Organization:
- American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 22973015
- Resource Relation:
- Conference: ANS NCSD 2017: Nuclear Criticality Safety Division topical meeting - Criticality safety, pushing boundaries by modernizing and integrating data, methods, and regulations, Carlsbad, NM (United States), 10-15 Sep 2017; Other Information: Country of input: France; 6 refs.; Available on CD-ROM from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- Country of Publication:
- United States
- Language:
- English
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