Tratamiento de reorientación de hidruros en tubos de circonio mediante presión interna

Resumo

Pressurized water nuclear reactors (PWR) use zirconium tubes -cladding- to contain the nuclear fuel and fission products. During operation in reactor, they capture hydrogen, that precipitates in the form of zirconium hydrides, usually in the circumferential direction of the cladding. During drying prior to dry storage, hydrides may be reoriented in the radial direction due to the thermomechanical conditions in the cladding. If the maximum main stress is circumferential, like in some postulated accident scenarios, this morphology may cause brittle fracture. The objective of this work is to develop a new hydride reorientation method (using internal pressure), different than the one used previously by this group. For this reason, a new device has been designed and build, that allows independent control of temperature and internal pressure of the cladding, which better reproduces what happens in real conditions. Hydrogen cathodic charge and a thermal treatment were used to precipitate zirconium hydrides in the circumferential direction. Afterwards a hydride reorientation treatment was performed and finally, ring compression tests were carried to evaluate the embrittlement of the material.