A minor problem.
The stored fuel rods are outside the containment.
Site total ~1600 TONS of fuel, ~ 80 tons in each containment.
A major problem.
Most of the news on this topic is slanted so far to each side it is difficult to make an assessment.
See Item 27 on DWG.
http://en.wikipedia.org/wiki/Fukushima_I_Nuclear_Power_Plant
The spent fuel pools at the Japanese plants are located outside the primary containment but within the secondary containment.