REMEDIATION OF LOW-LEVEL MIXED WASTE - CELLULOSE-BASED MATERIALS AND PLUTONIUM

Low-level mixed radioactive wastes containing cellulose-based material s and plutonium have been generated during various nuclear processing activities. Biological digestion of the organic- or cellulose- based m aterial was examined as an environmentally acceptable and effective me thod of treatment for these and other similar wastes. Cellulase enzyme was used to initiate biodegradation prior to 90% destruction of the c ellulose material by a sewage sludge consortium. Plutonium did not sig nificantly effect the biodegradation. Bench-scale experimental data we re used to design a batch treatment system. A cost and sensitivity ana lysis was performed to determine the optimal reactor size, materials o f construction and media type. The sensitivity analysis indicated that while a 12-month treatment scenario using a carbon steel ball mill, s ludge digester and vacuum thickener was the least expensive scenario e valuated on a levelized cost basis ($800 per ton of waste degraded per month), the 12-month scenario using stainless steel construction and the alternative dewatering system offered the most cost-effective trea tment alternative and better corrosion resistance (levelized cost of $ 1130 per ton per month). The dewatering system consisting of a disk ce ntrifuge and sludge dryer is capable of doubling the sludge solids con tent and produce an overall waste reduction of 67%. The proposed waste treatment system offers a cost savings of up to 31% compared to conve ntional disposal practices.