Performance of Cement for Immobilizing Strontium Waste in Saline Environment

Abstract

For solving the radioactive waste storage problem, there is an idea to store immobilized waste at deep sea. Solidifier material, such as cement should be resistance to saline environment for deep sea storage. So, this research objective is to study the performance of cement ation method in immobilizing strontium waste i n saline environment. Research was conducted by immobilizing strontium waste using Portland pozzolanic cement, white cement and composite Portland cement. Cement, 65 ppm Sr(NO 3 ) 2 , sand and water were mixed and cast . Strontium waste varied in 2 v/o, 4 v/o, 6 v/o and 8 v/o. After 28 days curing, the cement block ’s compressive strength and leaching rate on saline water were ana lyzed. Determination of compressive strength was done by using Universal Wood Testing. The density of blocks was measured by picnometer at 25° C . Compressive strength test for Portland pozzolanic cement at various w/c was conducted to confirm the effect of w/c in increasing the strength. For testing strontium leaching rate i n water containing 35 ppm NaCl, cement blocks have been immersed in saline water for 21 days. 25 ml samples were taken and analyzed by Atomic Absorption Spectrophotometer. Strontium leaching rate on block containing pH 9 of waste was compared to the previous research data of strontium leaching rate on water to know the effect of saline water. To adjust the pH, 1 MNaOH was added into the waste. Effects of various cement type and filler materials (sand, zeolite and baryte) on Portland pozzolanic cement were also compared. The results show that there were almost no effects of salt on im mobilized strontium waste, except in pH 9 waste (0.00224 over to0.000199 g/cm 2 ·days). Strontium leaching rates on all cemented waste still meet the IAEA’s standard , so the safety of cemented strontium waste disposal at saline environment could be ensured .