|Image Courtesy Union of Concerned Scientists|
When the 9.0 magnitude earthquake and tsunami struck, all of the fresh fuel at the plant's Reactor No. 4 had been removed and stored in a pool that must remain filled with cooling water. That pool became one of the biggest problems for plant operator Tokyo Electric Power Company, or Tepco, after much of the protective water dissipated, threatening fire and widespread radiation release.
The Japanese argue it's safer to move all the fuel to the pool, but the practice of full-core discharge caused a problem, in the case of the tsunami. They believe the practice of removing still-usable fuel and stowing it in the spent-fuel pool can be done safely if ample water is available and sufficient space is maintained between the rods.
|Outdoor Dry Casks: Image UCS|
Rods can be left in pools for many years for two reasons. First, they need to cool down. Second, no nation has yet solved the problem of what to do with large stockpiles of used nuclear fuel. As a result, much of it remains in utility holding pens. (WSJ, 3/21/2011)