Solidification of Microbiologically Treated Ion-Exchange Resins Using Portland Cement-Based Systems
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SOLIDIFICATION OF MICROBIOLOGICALLY TREATED IONEXCHANGE RESINS USING PORTLAND CEMENT-BASED SYSTEMS ARI IPATTI*
*IMATRAN VOIMA OY, Research and Development Division, Concrete and Soils Laboratory, P.O.Box 112, SF-01601, Vantaa, FINLAND ABSTRACT
Pretreated inactive ion exchange resins from the Loviisa nuclear power plant (NPP) were first reduced to one tenth of the original volume through microbiological treatment. During the process, the granular ion exchange resins were decomposed to result in dregs, which were solidified with two types of Portland cements. The objective of the present experiments was to investigate whether commercial cements are suitable solidification agents for this kind of waste. A total of ten mixtures were pretested for their rheological and setting properties. On the basis of the pretest results, four additional mixtures were chosen and tested for the spread value, density, air content, setting time and bleeding of the fresh waste product and for the dimensional stability and compressive strength of the hardened waste product. The cementing systems incorporated in the tests were ASTM type V Portland cement and ASTM type P Portland Composite cements. The dregs used in the tests were taken from a PilotPlant experiment at the Loviisa NPP and contained 2 wt-% solids. The test results were promising in showing that microbiological dregs can very easily be solidified with Portland cements to form a high-quality waste product. Thus, the microbiological treatment of spent ion exchange resins will drastically decrease the amount of solidified waste to be disposed of at the Loviisa NPP.
INTRODUCTION
Imatran Voima Oy (IVO) owns and operates two 465-MWe PWR units at the Loviisa NPP. The primary circuit water of the reactors is continuously circulated through the purification system based on granular styrene-based ion exchange resins, which are classified as intermediate-level radioactive waste. For the time being, all the spent resins produced are pumped into the liquid waste storage facility located within the plant area [1]. The estimated 3 total accumulation of spent resins from 30 years' plant operation is 600 m . According to the present solidification concept, the spent resins will be solidified in granular form with cement. The solidified wastes will be disposed of at the site. The repository will be constructed in the crystalline bedrock at a depth of 90 - 120 meters. On the basis of IVO's experiments, a typical volume increase factor for cement-solidified that by solidiwater-saturated ion exchange resins is on the order of 2.0 + 0.2. This means 3 fying the expected 600 m3 of resins with cement, a total of 1200 + 120 m of waste products will be disposed of. IVO's research and development on waste management has resulted in an alternative solidification concept, which is based on the microbiological treatment of waste before the cement solidification [1,2,3]. IVO-MicTreat is an anaerobic process designed for treating organic low and intermediate-level waste from a nuclear power plant. The pro
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