[en] Onagawa-2 started commercial operation on 28 July 1995 and the first annual outage started 27 August 1996. The total man-Sv exposure during the first annual outage was about 0.15, which was quite low for a boiling water reactor. To obtain this reduction in man-Sv at Onagawa-2, various countermeasure were applied from the point of plant design. In addition, the 'Clean Plant Campaign' had been implemented extensively throughout the design, construction, start-up test period, and the first cycle. In this campaign, 'Ultra Low Crud Control' was adopted to keep the ionic Ni concentration high in the reactor water for the suppression of the incorporation of the activity on the piping. In this report, the performance results of the water quality control and the dose rate throughout the first cycle are reviewed. (author)