Danger of Spent Fuel Outweighs Reactor Threat

Nuclear power has been both a blessing and a curse since its beginnings as a weapon. It generates a lot of power for comparatively little waste: minuscule amounts of greenhouse gases and a lot of energy for relatively little fuel. Unfortunately, the little waste that is created is highly dangerous and needs close attention for years.

Figures provided by Tokyo Electric Power on Thursday show that most of the dangerous uranium at the power plant is actually in the spent fuel rods, not the reactor cores themselves. The electric utility said that a total of 11,195 spent fuel rod assemblies were stored at the site.

That is in addition to 400 to 600 fuel rod assemblies that had been in active service in each of the three troubled reactors. In other words, the vast majority of the fuel assemblies at the troubled reactors are in the storage pools, not the reactors.

Now those temporary pools are proving the power plant’s Achilles heel, as the water in the pools either boils away or leaks out of their containments, and efforts to add more water have gone awry. While spent fuel rods generate significantly less heat than newer ones, there are strong indications that the fuel rods have begun to melt and release extremely high levels of radiation. Japanese authorities struggled Thursday to add more water to the storage pool at reactor No. 3. Read more…

Even though the power level in spent fuel has dropped considerably compared to fresh fuel, it still generates power…just not enough for the steam turbines. IMHO, it’s like charcoal briquettes after you have used them; while they may be too cool to barbecue any more food they’re more than hot enough to burn you. The nuclear fuel rods need cooling, usually for a couple of years, before they can be processed into something that can be stored inside a nuclear waste burial site.

Nuclear reactors make steam to turn turbines which turn generators to make electricity. Since water boils at 212 degrees Fahrenheit, it’s not a really efficient turbine working fluid in nuclear reactors because it can’t hold much heat. Pressurizing the water allows it to hold more heat before it boils and thus more energy when it reaches the low pressure zone of the turbine. This high heat requirement makes spent fuel useless for power production as it can’t generate that kind of power under normal circumstances. Removing safety restrictions (as in accidents) allows power to be generated but is useless as current reactor designs don’t have a safe way to harvest that heat energy. As a result of this situation, the fuel rods must be treated as if they generated power, without the benefit of actually producing power.