Doppler and Related Measurements in a Soft Fast-Reactor Spectrum

Technical Report · Wed Dec 31 04:00:00 EST 1969

DOI:https://doi.org/10.2172/4784461· OSTI ID:4784461

Springer, T. H. ^[1]; Tuttle, R. J. ^[1]; Otter, J. M. ^[1]; Paschall, R. K. ^[1]

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1. Atomics International, Canoga Park, CA (United States)

This report deals with a group of both theoretical and experimental investigations which have been carried out, utilizing Core 15, one in a series of critical assemblies that have been constructed at Atomics International's Epithermal Critical Experiments Laboratory (ECEL). Core 15 contains a U²³⁵ - U²³⁹ fueled, fast-spectrum test region, characterized by a median fission energy (mfe) of 18 kev. The investigations included studies of the neutron energy spectrum, the reactivity worths, and the Doppler coefficients of various candidate liquid metal, fast breeder reactor (LMFBR) materials. The latter two studies were performed on small heated samples, not only in the unperturbed core but also in an environment in which the samples were surrounded by 11 blankets 11 of fertile materials which could be heated to 400°C. The heated blanket technique permitted detailed experimental investigation of the so-called "hot sample - cold reactor" problem. These experiments show that, as a result of flux depressions at the resonances, large decreases in the Doppler coefficients of Th and U²³⁸ occur when a blanket of the same material as the sample is introduced in the immediate environment. When the surrounding blanket of the same material is heated to 400°C, a further decrease in the Doppler coefficient is observed. The implication is that a similar reduction in the Doppler effect of a particular isotope would occur in a LMFBR in which that isotope exists in large quantities.

• Research Organization: Atomics International, Canoga Park, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• DOE Contract Number: AT(04-3)-701
• NSA Number: NSA-23-011177
• OSTI ID: 4784461
• Report Number(s): AI-AEC-12705
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BREEDING
Blankets
CRITICAL ASSEMBLIES
Core 15
DOPPLER REACTIVITY
EXPANSION
FAST NEUTRONS
Fertile Elements
Flux Depression
LIQUID METAL COOLANT
MEASUREMENT
MFE
NEUTRONS
NUMERICALS
Nuclear Criticality Safety Program (NCSP)
REACTIVITY
REACTORS
SODIUM
SPECTRA
SPECTRAL SHIFT
TEMPERATURE
U235
U238