SEDL / STP / STP1423-EB / STP11384S

The Behavior of Intermetallic Precipitates in Highly Irradiated BWR LTP Cladding

Goll, W
Framatome ANP GmbH, Erlangen,

Ray, L
European Commission Joint Research Centre, Institute for Transuranium Elements, Karlsruhe,

Pages: 16    Published: Jan 2002

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Abstract

Advanced Zry-2 cladding materials exhibiting good corrosion behavior are a prerequisite for extending BWR operation towards high burnup. To assess the burnup potential of Zry-2, the behavior of the intermetallic second-phase precipitates was analyzed as a function of fluence and compared with the in-reactor corrosion behavior. Various Zry-2 cladding samples with particle densities between 3 and 13 mm^-2 with an average particle diameter of 50 to 80 nm and irradiation times of up to 2400 EFPD, equivalent to neutron fluences of up to 1 ∙ 10²² cm^-2 (En > 1 MeV), were analyzed by TEM/SEM. The measurements showed a significant decrease in the particle density within the first cycle of irradiation followed by a slow decrease up to high fluences. At the highest fluences, the precipitate structure underwent deterioration combined with a markedly reduced number density. However, about 1 to 2% new precipitates of the Zr³Fe-type were formed during irradiation.

Metallographic examinations of BWR fuel rods showed both nodular and uniform corrosion. Up to a local burnup of 65 MWd/kgU no change of the corrosion kinetics and no acceleration of corrosion was found.