Conference Proceedings Paper
CHARACTERIZING THE MECHANICAL PROPERTIES OF I ROD REMOVED FROM NATIONAL RESEARCH UNIVERSAL REACTOR
11th International Conference on CANDU® Maintenance and Nuclear Components - 2017 Oct. 01-04
M. Bach (Canadian Nuclear Laboratories)
S. St Lawrence (Canadian Nuclear Laboratories)
The National Research Universal (NRU) reactor is a research reactor which has many roles, one of which is the generation of isotopes used for both medical and non-medical purposes. The vessel wall of the reactor used to contain the heavy water is made of Al 5052 alloy. After corrosion issues shutdown the reactor in 2009, a program was developed to examine the mechanical properties of the vessel wall and its fitness-for-service. It so happened that the iodine-125 (I-rod) material used to produce medical isotopes in the NRU that was removed in 1991 was also made out of the same Al5052 as the vessel wall. A recent research and development project was created to study the mechanical properties of the I-rod with varying thermal fluence levels which, could be used to assess the conditions of the NRU vessel. While in the NRU reactor, various locations on the I-rod was exposed to a range of thermal fluence from 0 to a maximum of 11.9 x 1022 n/cm2. The end of life thermal neutron fluence of the NRU vessel is estimated to be 2.2 x 1022 n/cm2 at 35 years of service. The goal of this project was to determine the fracture toughness along the various locations of the I-rod to determine if the mechanical properties changes due to different levels of irradiation exposure. From the experiment, the yield strength and UTS increased with thermal fluence value due to the radiation-induced Mg-Si precipitate strengthening and reduction in ductility. It was determined that the fracture toughness of the material decreased with increase fluence rates. In the irradiated materials, unstable crack jumps were detected however, SEM images of the fracture face showed signs of ductile fracture and not brittle fracture.
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