ABSTRACTNuclear graphite components are produced from polycrystalline artificial graphite manufactured from binder and filler coke material with approximately 20% porosity. During the operational lifetime of a nuclear reactor the graphite moderator is subjected to fast neutron irradiation which contributes to changes in material and physical properties such as thermal expansion co-efficient, young’s modulus and dimensional change. These changes are directly driven by irradiation induced changes to the crystal structure as reflected through the bulk microstructure. Therefore it is important that irradiation changes and there implications on component property changes are understood. Work carried out under the FP7 CARBOWASTE consortium under work package three is underway to characterize both structural and radiological damage in graphite. This study examines a range of irradiated graphite samples removed from the British Experimental Pile Zero (BEPO) reactor. Raman spectroscopy and Transmission Electron Microscopy (TEM) have been used to compare the effect of increased irradiation Fluence on graphite microstructure. Irradiation induced crystal defects and changes in crystallite size are observed using TEM and related to Raman Spectroscopy, comparisons are also made to virgin nuclear grade graphite.
Earthquake response of a multiblock nuclear reactor graphite core: Experimental model vs simulations
