Nuclear Steam Generator Chemical Cleaning Waste Treatment Using Membrane Technology

Abstract

The chemical cleaning of Ontario Power Generation's Pickering nuclear steam generators using Framatome's high temperature process generates a significant volume of spent solvent and rinse waste that requires treatment. Since 1996, these wastes have been sent off-site to a commercial facility for incineration after interim storage and radiological characterization at OPG's Spent Solvent Treatment Facility (SSTF) Tank Farm. In 2002, with the objective of reducing overall treatment costs, OPG's Nuclear Waste Management Division made the decision to investigate a simplified on-site treatment process utilizing ultrafiltration (UF) and reverse osmosis (RO) systems to volume reduce the spent steam generator cleaning wastes prior to off-site incineration. Bench scale membrane treatability tests, performed on actual waste, indicated significant volume reductions and excellent effluent quality could be achieved with membrane processes. Based on these results, re-commissioning of the SSTF UF and RO systems began in 2002 followed by full scale processing in May 2003. To date, approximately 2200 m3 of steam generator chemical cleaning waste rinse water and approximately 70 m3 of copper solvent has been treated in the SSTF using a combination of ultrafiltration and two-pass reverse osmosis. The overall volumetric recoveries on rinse water have been between about 90% for the RO system and about 95% for the UF system. There has been no significant degradation of system performance from the standpoint of permeate quality or membrane permeability. The influent criteria for discharge of permeate to the site sewage treatment plant have been easily met with and the facility operates at a fraction of the deminimus unity factor established by the approved radiological pathway analysis.