The protection of hydrogen permeation through the heat exchanger tubes of the high-temperature gas-cooled reactor into a primary coolant is one of the most severe problems. Also in a thermonuclear fusion reactor the protection of tritium diffusion is considered to be essential from the standpoint of environmental contamination, because tritium has radioactivity.
In the 2nd report, the calorizing method which was applied to the heat exchanger tubes of the hydrogen secondary gas loop in Japan Atomic Energy Research Institute, is described. The amount of hydrogen gas which was permeated through the heat exchanger was successfully reduced to approximately 1/50. This experiment was conducted about 7 weeks in all under the following condition: helium gas temperature 1, 000°C, hydrogen gas temperature 900°C, helium gas and hydrogen gas pressures 40 atm, and no deterioration was observed.
After all the experiments were performed, the heat exchanger was cut and taken out of the loop to examine the micro-structure of the calorizing layer. The analyses by a microscope and an X-ray micro-analyzer proved that the calorizing layer was almost unchanged as fas as the metallurgical structure was concerned.
This calorizing method could be said to be very applicable to the reduction of hydrogen permeation from the industrial point of view.