지르코늄 압력관에서 Hydride Blister에 의한 잔류응력 측정

When the pressure tubes (PT) contact to the calandria tube (CT) in the pressurized heavy water reactor(PHWR), the temperature difference between inner wall and outer wall of PT results in a thermal diffusion of hydrogen (deutrium) and hydride blisters are formed on the outer surface of PT. The volume expansion associated with the formation and growth of zirconium hydride blister creates localized residual stresses in the PT. Residual stresses of localized area near the hydride blister were measured by micro-focused x-ray diffraction(XRD). The specimen were prepared using a cold spot on the outer surface of PT and the diameter of XRD beam was set as 100 ㎛. When we measured residual stress on the outer surface of PT, residual stress state of zirconium matrix just outside the blister were compressive and become tensile as moving to the inside the blister. The cross-sectional residual stress state of blister also revealed that compressive stress state at zirconium matrix just outside the blister and tensile stress state at the inside blister. These results are compared with the finite element model and discussed with the possibility of crack propagation to the zircoium matrix.