Contribution of Geopolymers to Hard Sludge Formation on the Secondary Side Under Transient Conditions: An Experimental Study

Hard sludge formation on top of tubesheet of modern steam generators (SGs) is non-desirable because it is associated with tube degradation problems that affect the efficiency of nuclear power plants. The characterization of SG deposit samples mainly constituted by hard sludge have determined high concentrations of aluminum and silicon (up to 6.0±0.1 wt% of Al and 2.7±0.1 wt% of Si), together with high microhardness values (above 800 HV) measured at particular locations within collars or hard sludge particles. In fact, there is evidence that the presence of aluminum and silicon is at the origin of the problematic of the formation of hard sludge in SGs during normal operation.