SEDL / STP / STP1123-EB / STP19562S

Cementation of Borate Waste by Adding Slaked Lime

Kim, J-H
Head, Korea Atomic Energy Research Institute, Taejon,

Kim, H-Y
Principal researcher, Korea Atomic Energy Research Institute, Taejon,

Park, H-H
Director, Korea Atomic Energy Research Institute, Taejon,

Suh, I-S
Vice-president, Korea Atomic Energy Research Institute, Taejon,

Pages: 10    Published: Jan 1992

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Abstract

With regard to the cementation of the evaporator concentrate from pressurized water reactors, this study identifies the operating conditions giving properly coherent waste forms of a high volume reduction factor, high compressive strength, and good workability without the development of freestanding water. Simulated waste specimens prepared by varying the mixing ratios of simulated borate waste [boric acid (H³BO³) 12% by weight, pH 9], Portland cement, and slaked lime were tested. The results appear in a three-phase diagram depicting the proper blending necessary to yield final products possessing a compressive strength of over 15 MPa and a volume reduction factor above 0.65.

The solubility of sodium borate is higher than that of H³BO³, and cementation of a concentrated borate solution (24 wt% H³BO³, pH 9) was therefore also tested. The region of over 15 MPa of compressive strength with a volume reduction factor of over 0.6 based on the waste volume was identified. By increasing the H³BO³ concentration in the waste from 12 to 24 wt%, the actual volume was reduced by an additional factor of about two.