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Diffusion Annealing as a Means of Improving Corrosion Resistance of Zircaloy-2 Clad, Uranium - 2 w/o Zirconium Rods

Technical Report ·
DOI:https://doi.org/10.2172/4190502· OSTI ID:4190502
 [1]
  1. Nuclear Metals, Inc., Concord, MA (United States)
The diffusion heat treatment technique has been investigated as a means of improving the corrosion protection provided by Zircaloy cladding coextruded with rods of U - 2 w/o Zr alloy. Specimens with cladding defects in the form of drilled holes were tested in high temperature steam and water to determine the effects of various factors influencing the beneficial effect of the diffusion anneal. These included heat treatment time and temperature, cooling rates, secondary heat treatments, defect size, cladding thickness, hardness, bond strength, and radiation. Most of these factors appeared to affect the ultimate corrosion life of the defected specimens. In particular, all heat treatments from 800 to 1050°C greatly increased the corrosion life if the time at temperature was sufficient; slow cooling rates or subsequent heat treatments between 650 and 700°C were detrimental; a strong initial bond is desirable; the treatment does not reliably provide protection if the cladding is 10 mils thick or less. A few defected, irradiated specimens have survived subsequent short-time corrosion tests. Tests were also performed on specimens with defects resulting from flaws placed in the cladding component prior to extrusion. Most of these specimens did not benefit from the diffusion anneal. The treatment was successful, however, in preventing the failure of specimens with threads of uranium extending between the core material and the exposed cladding surface. The diffusion anneal technique continues to show promise as a means of increasing the reliability of the Zircaloy cladding on rods of U - 2 w/o Zr.
Research Organization:
Nuclear Metals, Inc., Concord, MA (United States)
Sponsoring Organization:
US Atomic Energy Commission (AEC)
NSA Number:
NSA-14-018124
OSTI ID:
4190502
Report Number(s):
NMI--1217
Country of Publication:
United States
Language:
English