Lattice Experiments with Simulated Burned-Up Fuel for D₂O Power Reactors

Technical Report · Thu Feb 01 04:00:00 EST 1968

DOI:https://doi.org/10.2172/4531149· OSTI ID:4531149

Baumann, N. P. ^[1]; Crandall, J. L. ^[1]; Olson, R. L. ^[1]; O'Neill, G. F. ^[1]; Pellarin, D. J. ^[1]; Vandervelde, V. D. ^[1]

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1. Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.

The changes in lattice physics parameters accompanying fuel burnup in natural-uranium-fueled D₂O power reactors were studied by measuring bucklings and neutron reaction rates for D₂O-moderated lattices of UO₂ rod clusters containing five different concentrations of ²³⁵U and the plutonium isotopes. Both 19- and 31-rod clusters with D₂O, gas, and organic coolants were used at triangular lattice pitches of 9.33 and 12.12 inches. Substitution measurements in natural UO₂ lattices in the Process Development Pile determined the uniform lattice bucklings. Exponential measurements in the Subcritical Experiments determined the changes in buckling induced by uniform lattice heating. Foil activations, also performed in the Subcritical Experiment, measured the thermal neutron distributions in terms of Mn activations, the thermal neutron spectral indices in terms of Lu-Mn and ²³⁹Pu-²³⁵U activations, resonance neutron capture in ²³⁸U in terms of the cadmium ratio for ²³⁹Np production, fast fissions in ²³⁸U and all fissions in ²³⁵U in terms of the induced fission product activities, and fissile material conversion ratios in terms of the ²³⁸U capture to ²³⁵U fission ratios. These results were compared with calculations by the HAMMER code, a one-dimensional, integral-transport cell calculation performed in 84 energy groups. Although agreement between experiment and theory was in general good, significant discrepancies were observed in the spectral index and resonance capture calculations. These discrepancies were tentatively assigned primarily to difficulties in reducing the highly heterogeneous fuel clusters into a ring model for the one-dimensional calculations.

• Research Organization: Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.
• Sponsoring Organization: US Atomic Energy Commission (AEC); USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• NSA Number: NSA-22-025082
• OSTI ID: 4531149
• Report Number(s): DP--1122
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
ACTIVATION ANALYSIS
ANALYSIS
BURNUP
CRITICAL ASSEMBLIES
DISTRIBUTION
EXPONENTIAL PILES
FUEL ELEMENTS
HEAVY WATER MODERATOR
MEASUREMENT
N38550* --Research & Test Reactors & Critical Assemblies-- Fuels
Nuclear Criticality Safety Program (NCSP)
PDP COMPUTERS
PLUTONIUM OXIDES
Plutonium oxides
REACTIVITY
REACTORS
RODS
Savannah River Reactor
THERMAL NEUTRONS
URANIUM DIOXIDE