Status of a New Resonance Evaluation for Cerium to Support Nuclear Criticality Safety Applications

Journal Article · Sat Jul 01 04:00:00 EDT 2017 · Transactions of the American Nuclear Society

OSTI ID:23047520

Sobes, Vladimir; Guber, Klaus ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

A new resonance evaluation is currently being carried out at Oak Ridge National Laboratory (ORNL) for isotopes of cerium. This new evaluation will provide a much-needed update of the resolved and unresolved resonance parameters for {sup 140}Ce and {sup 142}Ce based on new and existing experimental cross section data. The physics of the resolved resonance region will be greatly improved, and new resonance parameter covariance data will be generated. Cerium exists predominately as {sup 140}Ce and {sup 142}Ce and can be found in chemical processing streams because it is used commercially as a catalyst or additive in chemical applications (e.g., glass polishing powder). Cerium has neutron-absorbing properties that can influence the reactivity of systems with fissionable material. The need for improved cerium cross section data has been identified specifically for the Hanford Plutonium Finishing Plant as part of the Nuclear Criticality Safety Program (NCSP) nuclear data request. Furthermore, cerium is a high-yield fission product, making it relevant for reactor calculations. Currently, ENDF/B-VII.1 evaluations for cerium isotopes (described in Section II) do not include the covariance data needed to support sensitivity/uncertainty analyses of systems involving cerium. In addition, the available cerium resonance parameters in ENDF/B-VII.1 are based on parameters provided in the Atlas of Neutron Resonances: Resonance Parameters and Thermal Cross- Sections. Z = 1-100 by S. Mughabghab; hence, the 'evaluated' resonance parameters are not based on a detailed R-matrix analysis. Furthermore, differential measurements are needed in the resonance region to accurately predict the neutron resonances. ORNL has completed new differential measurements on natural samples of cerium, and measurements of an enriched {sup 142}Ce sample are planned. A corresponding resonance evaluation for {sup 140}Ce and {sup 142}Ce being conducted by ORNL will provide detailed cross section resonance parameters and corresponding evaluated covariance data in the resonance region in support of the NCSP. The target uncertainty requested by the NCSP is on the order of 1-2% for the total cross section and less than 6% for the capture cross section in the resolved resonance region. New cerium resonance evaluations will significantly improve radiation transport calculations for systems involving cerium in processes in the DOE Complex. Also, the new evaluations will provide much-needed evaluated covariance data to support sensitivity/ uncertainty analyses.

• OSTI ID: 23047520
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 116; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CATALYSTS
CERIUM
CERIUM 140
CERIUM 142
CRITICALITY
FISSION PRODUCTS
FISSION YIELD
FISSIONABLE MATERIALS
NEUTRONS
NUCLEAR DATA COLLECTIONS
ORNL
PLUTONIUM
R MATRIX
RADIATION TRANSPORT
REACTIVITY
REACTOR SAFETY
SENSITIVITY
TOTAL CROSS SECTIONS