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Effects of Neutron Irradiation on the Microstructure of Alpha-Annealed Zircaloy-4 Pages: 27 Published: Jan 2002
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View License Agreement Source: STP1423-EB Abstract Analytical electron microscopy (AEM) was used to study the separate effects of the irradiation parameters on the evolution of the microstructure in recrystallized alpha-annealed Zircaloy-4 under controlled irradiation conditions. The effects of fast neutron flux from 4 × 10 n/cm-s to 1.5 × 10 n/cm-s ( > 1 MeV) neutron fluence in the range of 15 × 10 n/cm to 50 × 10 n/cm and temperature from 270 to 330°C were studied. The completeness of the test matrix and the exposure in the controlled environment of the advanced test reactor permitted the separate effects of fast neutron flux, fluence, and irradiation temperature to be delineated for the first time. It was found that an increase in the neutron flux increases the degree of amorphization of the second-phase precipitates but retards the redistribution of iron out of the amorphous region (neutron fluence and irradiation temperature remaining the same), whereas increasing temperature (neutron flux and neutron fluence remaining the same) has a reverse effect. Overall, the rate of amorphization of the second-phase precipitates observed in this work was larger than that predicted by many existing literature models. Finally, neither segregation of alloying elements to grain boundaries nor precipitation of any new phases were encountered.
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