Patent Number: 059986905
Section: description

EXAMPLE 1 288 parts by weight of 95% sodium hydroxide and 1,400 parts by weight of 99% boric acid were obtained and were each divided into two equal parts. Each of the two equal parts was again divided twice and the parts were added in order gradually into 600 parts by weight of deionized water under agitation. The sequence of addition is as follows: sodium hydroxide--boric acid--sodium hydroxide--boric acid. To wait for sodium hydroxide was completely dissolved, the mixture solution was heated slightly to allow boric acid to dissolve completely. Dissolved boron concentration of the solution thus obtained was 105,943 ppm and the molar ratio of sodium/boron was 0.3. After boric acid was dissolved, the solution was continuously stirred and was cooled to 40.degree. C., at which temperature the solution was kept for ready use. Before addition of the solidification agent, the solution must be weighed again in order to know the weight lost by evaporation of moisture in the abovementioned preparation process and was supplemented with water of the same temparature. 16 parts of Portland type II cement produced by Taiwan Cement Company, 13 parts of tribasic magnesium phosphate powder and 0.4 part of stranded carbon fiber were mixed, homogenized and then pulverized to prepare the solidification agent powder. Thereafter, this solidification agent powder was gradually added into a ready-for-use boric acid solution and was at the same time vigorously agitated to allow the solidification agent powder to mix with the solution to form a homogeneous slurry. The weight ratio of solidification agent to waste fluid is 0.4. Agitation was stopped ten minutes after the solidification agent was completely added, the slurry was immediately poured into a cylindrical polyethylene plastic model having an inner diameter of 5 cm and a height of 11 cm and then was left at the room temperature. Demolding took place 30 days after the solidification and 5 samples were obtained and cut into 10 cm long cylindrical specimens, the specimens were again tested for compressive strength under ASTM C39 procedure in accordance with the quality specification of the U.S. Nuclear Regulatory Commission. From the result of the test, the average compressive strength of the 5 samples is 189 kg/cm.sup.2. EXAMPLE 2 Borate solution and solidification agent were prepared in the same steps as in Example 1. In the solution, the concentration of the dissolved boron and the molar ratio of sodium: boron were also the same as in Example 1; the component of solidification agent was however changed to 4 parts of type 2A mud solidification agent (for composition, please refer to U.S. Pat. No. 5,457,262) with 1 part of magnesium oxide, 1 part of tribasic magnesium phosphate and 0.09 part of stranded carbon fiber. The weight ratio of solidification to liquid waste used was 0.3328. Demolding took place 7 days after the solidification and test was performed similarly with 5 samples. From the result, the compressive strength is 130 kg/cm.sup.2. EXAMPLE 3 Borate solution and solidification agent were prepared in the same steps as in Example 1. In the solution, the concentration of the dissolved boron and the molar ratio of sodium:boron were the same as in Example 1; the component of solidification agent was however changed to 15 parts of Portland cement with 3 parts of fume silica, 7 parts of silicon phosphate and 0.4 part of carbon fiber. The weight ratio of solidification agent to liquid waste used in the solidification was lowered to 0.289. From the result, it was obtained that the compressive strength after presservation for 8 months of the solidified body is 105 kg/cm.sup.2 and the water resistant compressive strength is 93 kg/cm.sup.2. EXAMPLE 4 Borate solution was prepared in the same steps as in Example 1 and in the solution the concentration of boron was made to be 120,000 ppm and the molar ratio of sodium:boron was 0.32. Thereafter, the fine powder of BaSiO.sub.3 was used as the solidification agent and solidification was performed with a ratio of each part of borate solution with 0.37 part of solidification agent. Demolding took place 7 days after solidification and test was performed similarly with 5 samples. From the result, the compressive strength is 61 kg/cm.sup.2. EXAMPLE 5 Borate solution was prepared in the same steps as in Example 1, however, the molar ratio of sodium:boron was raised and pH of the solution was adjusted low with 85% phosphoric acid. The prepared simulative liquid borate waste was measured to contain boron of 77,728 ppm, the molar ratio of sodium:boron of 0.7 and phosphoric acid (H.sub.3 PO.sub.4) of 25,909 ppm. The preparation process of the solidification agent was also the same as in Example 1, its composition being 13 parts of type IIA mud solidification agent of Taiwan cement Company with 6 parts of magnesium oxide and 0.3 part of stranded carbon fiber. In solidification, the weight ratio of solidification agent to liquid waste was 0.2383. Demolding took place 30 days after solidification and test was performed similarly with 5 samples. From the result, the compressive strength is 193 kg/cm.sup.2 and the water resistant compressive strength is 172 kg/cm.sup.2.