Unit 2 Suppression Pool Breach Feared; Containment Potentially Compromised

On March 15, a loud noise was heard from Unit 2 at approximately 06:10 JST, consistent with damage to the suppression pool (torus). This represented the most serious containment concern of the crisis, as the suppression pool is a key barrier against atmospheric radioactive release. Radiation levels at the site boundary spiked to over 400 mSv/h. TEPCO temporarily withdrew non-essential workers from the plant, leaving approximately 50 operators—the so-called 'Fukushima 50'—on site. A hydrogen explosion also occurred in Unit 4's reactor building on this day.