Jun-ichi Tani

Behavior of Stress Corrosion Cracking for Type 316L Stainless Steel With Controlled Distribution of Surface Work Hardened Layer in Simulated Boiling Water Reactors Environment

Stress corrosion cracking (SCC) of Type 316L stainless steels with controlled surface hardness distribution was investigated under simulated boiling water reactor (BWR) condition by creviced bent beam (CBB) tests. Intergranular microcracks having a depth of less than 50 μm are observed in 50 hours. Until 250 hours, depths of the microcracks are not increased. After 500 hours, cracks with depths of more than 50 μm are observed. SCC is initiated preferentially in a steep hardness gradient area.

Corrosion behaviour of aluminium under simulated environmental conditions of low-level waste

ABSTRACT In Japan, low-level radioactive waste including aluminium alloys is generated from nuclear power plants. It is well known that aluminium reacts with both alkaline cement and water, generating hydrogen gas. For the safe management of radioactive waste disposal facilities, it is necessary to evaluate corrosion and hydrogen generation behaviours of aluminium corresponding to changing environmental conditions. In the present study, the corrosion behaviour of aluminium in alkaline solutions at 15 °C was evaluated. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Methodology to Improve Corrosion Rate Estimation Based on Atmospheric Corrosion Monitoring Sensors

The accuracy of corrosion rate estimation using atmospheric corrosion monitoring (ACM) sensors is improved using humidity data. This methodology determines the daily amount of sea salt, Ws, to consecutively determine rain/dew/dry conditions for instantaneous output. ACM outputs observed in 4.8-m-long steel pipe braces installed on the Japanese coast were used to verify the methodology. Ws is the basic value used in analysis and is in agreement with experimental observations. When using this methodology, divergence of estimated and observed corrosion rates was reduced by up to 40% compared with results using the conventional methodology that determines rainfall using only outputs from ACM sensors.

An in Situ Raman Spectroscopy System for Long-term Corrosion Experiments in High Temperature Water up to 673 K

A Raman spectroscopy system has been developed, in order to identify metal oxides formed on the surfaces of metals and steels in high temperature water up to 673 K. A supercritical water loop system including a Raman cell was installed. The design of the loop system is up to 673 K and 40 MPa. The Raman cell has a diamond window without window-to-metal packing. Raman spectrum of alumina plate was measured at room temperature, at 523 K and at 673 K under pressure of 25 MPa. A long-term measurement was also performed at 523 K and 25 MPa for 117.5 h. In all cases intense Raman peaks attributed to alumina were observed. Raman spectrum of anatase particles in suspension was measured at 673 K and 25 MPa. The results show that the Raman spectroscopy system developed in the present study works well not only for plate sample but also for suspension. Raman spectra observed for titanium plate in high temperature water of 673 K and 25 MPa show growth of several Raman peaks with time up to 257 h. The peaks disappeared after cooled down to room temperature. The experimental results have demonstrated importance of in situ Raman spectroscopy.