Patent Number: 047626461
Section: claims

1. A method of treating low level radioactive waste liquid to form encapsulated solid for burial, the method comprising the steps of (i) adding caustic solution to the waste liquid to give the liquid a substantially neutral pH value in the range between about 6 and about 8, and agitating and cooling the liquid during the addition,  (ii) subjecting the so neutralized liquid to atomization to provide particles of solid radioactive material and water vapor,  (iii) separating the particles from the water vapor, and  (iv) encapsulating the particles in a matrix. 2. A method according to claim 1 wherein the pH is adjusted to about 6.7. 3. A method according to claim 2 wherein a strong caustic solution is used to adjust the pH of the liquid. 4. A method according to claim 3 wherein the strong caustic solution is potash. 5. A method according to claim 2, wherein the adjustment of the pH takes place in a vessel connected to the atomiser, and the vessel and the atomiser both have inner wall surfaces of stainless steel. 6. A method according to claim 1 wherein the atomiser has a rotary turbine and the substantially neutral liquid is supplied to the turbine which is rotated to form droplets of the liquid which are then atomised by the passage of hot air into the atomiser to form particles of radioactive material and direct them on to the inner wall surfaces of the atomiser. 7. A method according to claim 6 wherein the heated air supplied to the atomiser is heated by an electric heater to an inlet temperature of about 400 C. to about 500 C. 8. A method according to claim 6 wherein the heated air emerges from the atomiser at an outlet temperature of about 105 C. to about 150 C. 9. A method according to claim 6 wherein the solid particles are separated from water vapor by passage through a filter. 10. A method according to claim 9 wherein the filter comprises a set of filters each of successively finer sieve size and arranged to return clean air to atmosphere. 11. A method according to claim 6 wherein the solid particles are passed over a fluidised bed after removal of water vapour. 12. A method according to claim 6 wherein the solid particles are encapsulated under vacuum in a thermohardenable resin, concrete or bitumen. 13. A method according to claim 5, including the step of passing demineralised water through the vessel and the atomiser to clean out the vessel and the atomiser.