NONTOXIC DISCHARGE, A NEW REQUIREMENT ON RADIOACTIVE LIQUIDWASTE TREATMENT AT OPG NUCLEAR STATIONS

摘要

The Municipal and Industrial Strategy for Abatement (MISA) regulation, which came into effect in 1995in Ontario (Ontario Regulation 215/95 under the Environmental Protection Act), imposed additionallimitations on liquid discharges from power generating stations.The MISA regulation has divided discharges into non-event and event streams, which have to bemonitored for, prescribed parameters and for toxicity. Radioactive Waste Management Systems fall intocategory of non-event streams. Standard toxicity testing involves monitoring lethality of Daphnia Magnaand Rainbow Trout in the effluent. The new legislation has imposed a need to address several issues:acute toxicity, complying with the specific limits prescribed by the regulation and, in a long run, chronictoxicity.In the first phase, the correlation between various chemical parameters and acute toxicity wasestablished and several investigations were initiated. The effects of microbial activities in the wastestreams were the most difficult to address because many synergies between chemical toxicants andmicrobial toxins were not known. Due to limited time schedule to achieve MISA compliance, a wideapproach was taken. Approaches included best management practices in the power plants, wastestream segregation and a choice of treatment technology that could simultaneously address a number ofpotential toxins. Furthermore, the variability of the waste streams in present and in future had to betaken into account. This approach had a drawback in potentially generating significant costs ofconsumables and volumes of secondary solid radioactive waste. A strategy, to monitor treatmenttechnology performance and to optimize processes and costs in the long run, was therefore devised.Control of waste generation and centralizing laundry facilities from Pickering and Darlington to the Brucesite have enabled achievement of MISA compliance with simple processes and modifications atPickering and Darlington stations (laundry is a key source of organic toxins). In parallel, the moreelaborate technologies were applied at Bruce 1-4 site for treatment of additional laundry wastes.Originally, Active Liquid Waste Treatment (ALW) systems were designed to remove radioactivity fromthe liquid waste streams. Achieving radioactivity Derived Emission Limits (DEL's) and Station TargetLimits was never a problem in Ontario Power Generation stations and the ALW treatment systemswere rarely required for this purpose. Modifications of these existing systems and installation of the newtreatment systems, were a part of the strategy developed at OPG.At Pickering a completely new treatment system was designed and installed. The process consists of anultraviolet biocide unit, cartridge filtration, Granulated Active Carbon (GAC), cation resin andneutralizing filter (CaCO3) bed. This combination of processes enabled use of adsorption for reduction