Thermal Decomposition of 3-Methoxypropylamine as an Alternative Amine in PWR Secondary Systems

概要

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The secondary coolant of pressurized water reactors is buffered to slightly alkaline pH by ammonia or amines in order to suppress corrosion. 3-Methoxypropylamine (MPA) is one of the promising alternative amines. The thermal decomposition of MPA was studied under two conditions: (i) a dissolved oxygen (DO) concentration of less than 5 ppb at 280°C for 1.5 h and (ii) a DO concentration of 20 ppb at 70°C for 2 h. The initial MPA concentration was 10 ppm. After the tests, concentrations of MPA and carboxylic acids were measured. Approximately 9 to 15% of MPA was decomposed after the tests. Carboxylic acid concentrations were as follows: (i) formate 110 ppb, acetate 260 ppb and propionate 400 ppb at 280°C, and (ii) formate less than 2 ppb, acetate 60 ppb and propionate 1270 ppb at 70°C. The reaction mechanism of MPA decomposition was estimated from the present experimental results. At 280°C, the hydrolysis of the ether bond initiates the decomposition, and the subsequent bond cleavage of C-N and/or C-C occurs. At 70°C, hydrogen abstraction by an oxygen molecule is the initiation reaction. MPA radicals and HO2 or C1 compounds propagate a chain reaction and result in a relatively high yield of propionate.
一般社団法人日本原子力学会の論文
2009-02-01