Corrosion Test of 304 Stainless Steel in Hydrazine and Methanol Solutions at 320 °C under Gamma-Irradiation and Gamma Radiolysis of Hydrazine and Methanol

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Dissolved hydrogen is one of the key factors of PWSCC (primary water stress corrosion cracking) in the primary systems of pressurized water reactors. The authors consider that application of alternative reductant for hydrogen may mitigate PWSCC. The corrosion tests of 304 stainless steel specimens in methanol solution and hydrazine solution at 320 °C were carried out under γ-ray irradiation, and the corrosion environment was evaluated. Electrochemical corrosion potential (ECP) of the stainless steels was -605 mV and -643 mV vs. SHE in 2 mmol dm-3 hydrazine solution and 2 mmol dm-3 methanol solution at 320 °C, respectively. After the immersion tests, oxide films formed on the stainless steel specimens were analyzed. It is concluded from the ECP measurement and comparison with previous results that corrosion environment under following conditions is similar: (1) 1.5 ppm DH without irradiation, (2) 2.9 ppm methanol without irradiation, (3) 2 mmol dm-3 hydrazine under γ-ray irradiation and (4) 2 mmol dm-3 methanol under γ-ray irradiation. During the immersion tests, the test waters were sampled, and analyzed, in order to understand radiolysis of the methanol solution and the hydrazine solution at 320 °C. Hydrazine is decomposed predominantly through thermal decomposition, and an ammonia molecule is formed from a hydrazine molecule. Formaldehyde and ethylene glycol were detected in the methanol solution. But, carboxylates were not detected. The present results do not demonstrate oxidation of methanol to CO or CO2. Irradiation experiments of higher absorbed dose are necessary.

Corrosion Test of 304 Stainless Steel in Hydrazine and Methanol Solutions at 320 °C under Gamma-Irradiation and Gamma Radiolysis of Hydrazine and Methanol

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