Patent GB-1019373-A (GB)
Title: A new glass containing radioactive waste oxides
Inventor: GROVER JOHN ROGER
IPC: G21G4/04
Filed: 1962-08-10
Abstract: A glass with melting point 850 DEG -1100 DEG  C. consists essentially of (a) glass-forming oxides and (b) 20-50% by weight of waste oxides. Oxides (a) may be of Ca, Na, K, Mg, Pb, Mo, Zn, Al or Fe or B, P or Si which may be in the form of borates, phosphates or silicates.  The term "waste oxides" is defined as the mixture of oxides in the effluent or waste from treatment to remove U and Pu from irradiated metallic U fuel having burn-up greater than 3000 MW d/t. The oxides may initially be present as nitrates. Waste oxides comprise oxides of U, alloying additions, fission products and canning material and may include oxides of Ba, Ce, Cs, La, Mo, Nd, Pd, Pr, Rh, Ru, Sm, Sr, Tc, Te, Y, Zr, Fe, <PICT:1019373/C1/1> Al; smaller amounts of Ag, Eu, Pm, Rb, Cr, Ni, Mg and Si oxides may also be present.  An article may comprise the glass contained in a steel vessel.  In the Figure stainless steel cylinder 1 is in furnace 2, having six independently controlled heating elements which may be raised and lowered by support means 3.  Waste oxide solution and glass-forming oxide slurry, which may both be in HNO3 are mixed and fed via 6 and 4 to 1. The slurry is heated to form ultimately a molten glass at the bottom of 1.  The temperature of furnace 2 is raised to the maximum of 1100 DEG  C. and the furnace is so placed that remaining sinter and spattered dust in cylinder 1 is fused.  From 1, gases pass via 5, 7, 5a to identical cylinder 1a in oven 8 at 250 DEG  C. The gases leave 1a via filter 9 which may be iron oxide in a perforated steel container supported by a fusible zinc link and which traps ruthenium oxide, and pass via 4a and 10 into cylinder 11 in oven 12 at 250 DEG C., through filter 13 to condenser 14 which removes water, and thence to NO absorber tower 15, fed by condensate from condenser 14. Gases from 15 pass to the atmosphere via caustic scrubber 16, filter 17 and vacuum ejector 18.  After the above-described fusion of the contents of cylinder 1, the cylinder, containing the filter from a previous stage of the operation, is cooled.  At the same time cylinder 1a is cooled and transferred to furnace 2, and a new cylinder is placed in oven 8.  On raising the temperature of 2 the zinc link supporting filter 9 melts at about 420 DEG  C. whereupon the filter 9 drops to the bottom of the cylinder as at 19, where it will become encased in the glass to be formed.  If a phosphate glass composition is employed, the cylinder surface is preferably protected from corrosion either by diffusing Al into the inner surface of the cylinder, subsequently oxidizing this Al and adding up to 20% by weight excess Al2O3, or by adding up to 20% by weight iron oxide to the glass. Compositions are exemplified in the following systems: nepheline syenite-calcium oxide-boric oxide; sodium phosphate - calcium oxide - silica; lead oxide - boric oxide - silica; sodium phosphate - lead oxide - boric oxide, sodium phosphate - lead oxide - silica; sodium phosphate - sodium silicate; boron phosphate-sodium oxide - silica; sodium phosphate - lead oxide - zinc oxide; sodium oxide - silica-calcium oxide - boric oxide; borax - silica; molybdenum trioxide - potassium phosphate; sodium phosphate - silica - lead oxide - iron oxide.  A preferred embodiment of the last-named system has composition by weight: 42.4-47.7% sodium phosphate, silica 0-5.3%, lead oxide 0-5.3% ferric oxide 7-0% and waste oxides 40%. Experiments were carried out using simulated, non-radioactive waste oxides; in many cases K was substituted for Cs and Rb.  The article of glass in a steel vessel may be used as a homogeneous source of g -radiation, of mixed spectrum, free from BETA-rays and a -particles, or as a heat source, or as a means of disposal of waste oxides.