[en] Corrosion of ultra-low carbon type 304 stainless steel in boiling nitric acid solution was analyzed by statistical approach. A large scale mock-up of an evaporator was introduced to perform corrosion test of heat exchanger tubes, and change in loss of wall thickness and intergranular penetration depths of the tubes during test duration was measured and analyzed statistically applying normal distribution and Gumbel distribution. As the results, it was considered that tube wall was corroded uniformly and maximum value of loss of thickness was not exceeded by maximum depth of intergranular penetration. This conclusion means that tube wall thickness measurement can be applied to prevention maintenance against corrosion with intergranular penetration of stainless steel in boiling nitric acid solution. (author)