Laboratory scale testing program was conducted to investigate the feasibility of using water extended polyester cement composite (PCC) based on poly(ethylene terephthalate) waste (PET) as immobilization matrix for borate waste, originated from pressurized water reactors (PWRs), during prolonged term of disposal process and in scenario of flooding accident. Twenty-eight days cured solid blocks prepared as a premix of 3% by weight of the water extended polyester (WEP) and ordinary Portland cement (OPC) past having 40% by weight water were subjected to static immersion in three type of leachants, namely tap, sea, ground water. Weight changes, compressive strength variations, porosity, water absorption, and some other physical properties of the solid PCC waste forms were evaluated during 260 days of the static immersion. X-ray diffraction (XRD), infrared analysis (IR), and electron scanning microscope were performed for the waste forms at the end of immersion prolonged period to follow the internal changes in the solid waste forms that may occur due to the corrosion action of the different leachants. The results obtained from the different measurements confirm the performance of the PCC solidified waste form, based on the mentioned formulation, as an acceptable matrix in the various disposal sites and for extended disposal time even at the worst flooding environment. (c) 2007 Wiley Periodicals, Inc.