In its Feb. 14, 2012 final significance determination letter to Entergy Nuclear about a Sept. 25, 2011 loss of power to the control room at the Palisades atomic reactor in southwest Michigan, the U.S. Nuclear Regulatory Commission reported that not until 6 p.m., "Cooling was restored to spent fuel pool heat exchanger (lost during loss of power). The pool temperature was 83.4 [degrees] F at 15:00 [3 p.m.] and had risen to 87.4 [degrees] F by the time the heat exchanger was restored."
Although Palisades has had dry cask storage since 1993, the vast majority of its high-level radioactive waste is still stored in its indoor pool. Loss of pool cooling for long enough would lead to boiling, and eventual exposure of irradiated fuel to air. After a short time without water cooling, irradiated nuclear fuel will ignite, and the fire could spread to the entire pool inventory. Up to 100% of the hazardous radioactive Cesium-137 contained in the irradidated nuclear fuel could be released into the environment. An NRC commissioned study in 2001 reported that 25,000 latent cancer fatalities could result from a pool fire. An NRC commissioned study in 1997 reported even more shocking figures: 143,000 latent cancer fatalities downwind of a pool fire.