Critical Experiments with Thoria-Urania Fuel in Heavy Water

Technical Report · Fri Dec 01 04:00:00 EST 1961

DOI:https://doi.org/10.2172/4806726· OSTI ID:4806726

Redman, W. C. ^[1]; Kaufmann, S. G. ^[1]; Plumlee, K. E. ^[1]; Baird, Q. L. ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States)

The nuclear characteristics of a variety of small reactors composed of thoria-urania fuel in heavy water were determined in a program of critical experimentation. The fuel element consisted of ceramic ThO₂-U²³⁵O₂ pellets stacked to a height of 1.5 m within 0.787-cm-OD aluminum tubing. The pellets used most frequently were of 0.587-cm diameter and had a Th/U²³⁵ atom ratio of 25. Rods containing similar pellets with only half as much U²³⁵ were used to achieve small changes in the U²³⁵ content of the cores. Some cores were assembled with 0.660-cm-diameter pellets having an atom ratio of 15. All cores were located in a 2-m-diameter tank containing D₂O. Three distinct core structures were used, allowing measurements with uniformly distributed fuel rods, loading patterns compatible with the EBWR core geometry, and clustered lattice arrangements with D₂O, H₂O, and air surrounding the clustered fuel. Most of the cores assembled had some amount of radial D₂O reflector. A 0.3-m-thick bottom reflector composed of D₂O and aluminum was always present. For most of the assemblies, the control rods were fully withdrawn, criticality being achieved by adjustment of the water level. Observed critical dimensions and the results of the conventional reactivity, foil activation, and fuel substitution experiments used to determine core parameters such as p, ϵ, f, and $$\tau$$, are reported. Information on void and temperature coefficients and control rod worth is included. No comparison of the experimental results with theoretical predictors is made nor are observations made on flux-trap systems of this composition included.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• DOE Contract Number: W-31109-ENG-38
• NSA Number: NSA-16-009344
• OSTI ID: 4806726
• Report Number(s): ANL-6378
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
AIR
ALUMINUM
CONFIGURATION
CRITICAL ASSEMBLIES
D2O
EBWR
FUEL CANS
Fuel Elements
H2O
HEAVY WATER
LATTICES
MEASURED VALUES
NEUTRON FLUX
Nuclear Criticality Safety Program (NCSP)
PELLETS
REACTIVITY
REACTORS
REFLECTORS
Reflector Savings
THORIUM OXIDES
THUD
U235
URANIUM 235
VESSELS
WATER
ZPR-III