The Fukushima nuclear plant has more than 330,000 tonnes of water stored in pits, basements and tanks with varying levels of toxicity. The 300+ tonne water leak last week was from a tank similar to the others across the site. The Japanese Nuclear Regulation Authority is concerned that further spills may occur from the badly constructed tanks.
Why Fukushima is worse than you think – CNN
Q&A Fukushima Leak Problems – BBC
Fukushima’s toxic water pool grows as Tepco dithers – the Age