| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
The decelopment of iodine removal technology is vital for the prevention of radio activity from the reprocessing facilities of spent fuel from nuclear power plants. Iodine species present in the aqueous acidic solution, in which the spent fuel rods are chopped and dissolved in concentrate nitric acid, are considered to be I^- and IO_3^-. In the presently proposed iodine removal process, the simultaneous oxidation of I^- and the reduction of IO_3^- by nitrous acid, produced by the bubbling of N_2-NO_2 gas mixture into the acidic solution, is considered. The mechanism and the rate of these reactions, however, are not known, which is the purpose of the present investigation.
The obtained outcome of the present research work is outlined as follows:
(1) The produced nitrous acid is consumed in acidic solution by a self-decomposition reaction, which is a three step successive reaction. It is a rather slow reaction and the last of the three steps is the rate determining step. The expression of this rate and the temperature dependency awere clarified.
(2) The oxidation reaction of I^- into iodine by nitrous acid is a rapid but complicated reaction. The dependencies of this reaction rate upon reactants concentrations and temperature were formulated. In the process of studying this reaction, the oxidation reaction rate of NO into NO_2 in aqueous acidic solution was also formulated.
(3) The reduction reaction of IO_3^- into iodine by nitrous acid is a slow and complicated reaction which has an induction period, and the presence of two mechanisms was confirmed in this reaction. The one is responsible for the production of iodine in the early stage and is of less importance. The other is a self-catalytic reaction, the reaction rate of which was formulated and the temperature dependency of the rate constant was made clear.
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