at 07:30 jst, tepco prepared to release radioactive steam, indicating that "the amount of radiation to be released would be small and not of a level that would affect human health" and manual venting took place at 08:41 and 09:20. at 09:25 jst on 13 march, operators began injecting water containing boric acid into the primary containment vessel (pcv) via the pump of a fire truck. when water levels continued to fall and pressure to rise, the injected water was switched to seawater at 13:12. by 15:00 it was noted that despite adding water the level in the reactor did not rise and radiation had increased. a rise was eventually recorded but the level stuck at 2 m below the top of reactor core. other readings suggested that this could not be the case and the gauge was malfunctioning.