Non-destructive testing dummy nuclear fuel rods by neutron radiography

The nuclear fuel rod is a key component of nuclear plants and reactors. It works in the extreme conditions, so it is easy to be broken. In order to be safe in operation, lots of testings have to be carried out from fabricating to operating of the fuel rod. As a unique non-destructive testing technique, neutron radiography can be used to measure the nuclear fuel rods with radioactivity by an indirect neutron radiography method. Study the indirect neutron radiography method is the primary step of testing. Non-destructive testing experiments were carried out at China Advanced Research Reactor (CARR) by indirect neutron radiography method with dummy nuclear fuel rods as the samples. The 0.1 mm-thick Dy foil was used as the neutron converter. The neutron images of dummy nuclear fuel rods were obtained. The resolution of testing was analyzed with the images. Through imaging analysis methods, the structure defections, the hydrogen accumulation in the cladding and the U-235 enrichment of pellet were studied and analyzed. The indirect neutron radiography method and the neutron image analysis method were studied. The work described in this paper provides a primary guideline for investigating actual irradiated fuel rods by the neutron radiography at CARR in the future.