Japan tsunami: Latest updates

11.53am:

A former US energy policy adviser says the use of seawater and boron to cool the reactor at the Fukushima Dai Ichi nuclear power plant was a desperate, "Hail Mary pass" tactic, with success depending on the volume and rate at which the dousing continues.

Robert Alvarez told reporters in the US that the effort would need to continue non-stop for several days.