Reduction of Radioactive Secondary Waste With Steam Reforming in Treatment of Waste TBP/Dodecane

Waste tributyl phosphate (TBP) and normal dodecane generated from R&D activities on recycle of nuclear fuel has been stored in Japan Atomic Energy Agency (JAEA). If it is incinerated, a large quantity of contaminated phosphorous compounds will be generated as radioactive secondary wastes. The objective of this study is to reduce the generation of the radioactive secondary wastes by the treatment of the waste TBP/dodecane using steam reforming system. We constructed the demonstration scale steam reforming system which consists of a gasification chamber for vaporization of wastes, a metal mesh filter for removal of radioactive nuclides from gasified wastes, a combustion chamber, and scrubbers for removal of phosphorous oxides. We conducted process demonstration tests using waste TBP/dodecane with 0.07 g/L of uranium. We studied the temperature dependence of the gasification ratio of inorganic phosphorus compounds formed by pyrolysis of TBP in the gasification chamber and removal of uranium by the filter. As the results, more than 90% of phosphorus compounds were gasified from the gasification chamber at temperature of 600°C or more, and the uranium concentration in the waste water generated from the off-gas treatment system is under the detection limits. The waste water containing the separated phosphorus compounds can be discharged into the river or the sea as the liquid wastes in which uranium concentration is under the regulatory level. These results show the steam reforming system is effective in the reduction of radioactive secondary waste in the treatment of TBP/dodecane.