Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Crack initiation criterion at notches in Zr-2.5Nb alloys

Abstract: This work investigates the experimental conditions necessary for initiation of delayed hydride cracking in Zr-2.5Nb alloys. The experiments were performed on 240 notched cantiliver beam specimens loaded in pure bending to a wide range of stresses. The test temperature was 250°C with weekly cycles between 60 and 295°C. The results are interpreted in the light of a recently proposed fracture criterion for hydrides at cracks and notch tips. This criterion is based on the premise that crack initiation occurs if the local tensile stress at the hydride exceeds that for hydride fracture. The local stress at the hydride is expressed as the sum of the peak stress at the notch and the stress in the hydride arising from the hydride formation process. The fracture stress of the hydride is obtained experimentally. An approximate analytical method, based on a modified Neuber's rule, was used to calculate the plastic zone size needed to estimate the peak stress at the notch. These approximate calculations show that the threshold notch tip stress for cracking is between 675 and 750 MPa.

The Effect of Microstructure on Delayed Hydride Cracking Behavior of Zircaloy-4 Fuel Cladding—An International Atomic Energy Agency Coordinated Research Program

Abstract: The rate of delayed hydride cracking (DHC) has been measured in Zircaloy-4 fuel cladding in several metallurgical conditions using the pin-loading tension technique. In light water reactor (LWR) cladding in the cold-worked and cold-worked and stress-relieved conditions, the cracking rate followed Arrhenius behavior up to about 280 °C, but at higher temperatures the rate declined with no cracking above 300°C. Non-LWR cladding appeared to behave in the same manner. In LWR cladding in the recrystallized condition, the cracking rate was highly variable because it depended on KI within the test range up to 25 MPa√m, whereas in the other LWR claddings, cracking rate was independent of KI, indicating that KIH was below 11 MPa√m. The main role of microstructure was to control the material strength; the cracking rate increased as the strength increased. Although all the claddings had a radial texture, it did not protect the cladding from DHC. The DHC fracture surface consisted of flat broken hydrides, often in arcs, but no striations were observed, except in one specimen subjected to thermal cycles.