Evaluation of Thermal Decomposition Behavior of Carbohydrazide and Its Suppression Effect on Carbon Steel Corrosion

Abstract

In the secondary systems of pressurized water reactors (PWRs), all volatile treatment (AVT) is applied. Hydrazine is added as an oxygen scavenger. The authors hypothesized that carbohydrazide would be a harmless alternative to hydrazine. In the present study, the thermal decomposition and corrosion suppression effects on carbon steel of carbohydrazide were evaluated in comparison with those of hydrazine. The rate constant of the thermal decomposition of carbohydrazide was evaluated. The oxygen-scavenging efficiency of carbohydrazide is slightly lower than that of hydrazine. However, it has been confirmed that corrosion of carbon steel is suppressed more in carbohydrazide solution than in hydrazine solution at 423 K. It is considered that carbohydrazide is less reducing at 423 K than hydrazine, and that carbohydrazide suppresses reductive dissolution of iron oxides. It can be concluded that carbohydrazide is a promising alternative to hydrazine in the secondary systems of PWRs.