Thermal stability of morpholine in a PWR secondary system

Morpholine decomposition products are supposed to be one of the origins of organic acids in PWR secondary system where morpholine treatment is used. Laboratory and loop tests have been carried out in order to investigate the thermal stability of morpholine and the migration of decomposition products. Theoretical investigations supported by laboratory experiments lead to propose a decomposition mechanism which begins with the hydrolysis of morpholine into other amines and glycol. Then, in presence of metallic catalysts and at high temperature these decomposition products lead to aldehydes and organic acids. Laboratory and loop tests confirme that cation conductivity increases are not due to morpholine impurities but to the products of the thermal decomposition of morpholine. Acetate and formate are the main decomposition products observed in loop tests. (author)