Patent Number: 045405123
Section: summary

BACKGROUND OF THE INVENTION Nuclear wastes containing large amounts of boric acid are generated during the operation of pressurized water reactor (PWR) electrical generating plants. Other sources of such wastes are low level burial sites which have either intercepted and stored run-off from the burial trenches or received unacceptable, unsolidified boric acid waste. The most popular method for solidifying low level waste in power plants is to concentrate the waste to 12% boric acid in waste evaporators, then mix the waste with concrete. Alternatively, a bitumen or a water expandable polymer may be mixed with the waste to produce a solid mass. While methods for reducing the volume of the waste have been devised, the volume of the waste is still large, and the high concentrations of boric acid in the waste may interfere with the setting of concrete. Also, boric acid is a very leachable substance in concrete and as it leaches out, it leaves pores through which the radionuclides can escape. SUMMARY OF THE INVENTION We have discovered a process for separating and recovering boric acid from water containing nuclear wastes and boric acid. The process of this invention lowers the volume and mass of nuclear waste that must be solidified up to about eight times less than it would be if the boric acid were present. The resulting cement containing the nuclear waste without boric acid present is stronger and less susceptible to leaching of the radionuclides. An added advantage of the process of this invention is that the boric acid is recovered and can be reused in the nuclear reactor. The process of this invention is relatively uncomplicated and inexpensive to implement. RELEVANT ART The 53rd Edition of the CRC Handbook of Chemistry and Physics, page D-29, shows that an azeotrope is formed of 27.0% methanol and 73.0% trimethylborate which boils at 54.0.degree. C. U.S. Pat. No. 4,086,325 discloses a process for drying solutions containing boric acid by the addition of an oxidizing agent, such as hydrogen peroxide. The boric acid solution is first neutralized with sodium hydroxide. The sodium borate is then oxidized to an insoluble perborate by the addition of hydrogen peroxide. U.S. Pat. Nos. 4,225,390 and 4,073,683 both disclose boron control systems for a nuclear power plant which include an evaporative boric acid recovery apparatus. U.S. Pat. No. 4,314,877 discloses a method and apparatus for drawing radioactive waste for the concentrates from evaporators in order to reduce the volume on the resultant waste. U.S. Pat. No. 4,257,912 discloses a process for encapsulating spent nuclear fuel into concrete.