First “as the core gets hotter and hotter,” easily evaporated products of atomic fission — like iodine 131 and cesium 137 — fly out.
If temperatures rise higher, threatening to melt the core entirely, he added, less volatile products such as strontium 90 and plutonium 239 join the rising plume.
The lofting of the latter particles in large quantities points to “substantial fuel melting"
a blow-by-blow of the accident’s early hours and days.
It said drops in cooling water exposed up to three-quarters of the reactor cores, and that peak temperatures hit 2,700 degrees Celsius, or more than 4,800 degrees Fahrenheit.
That’s hot enough to melt steel and zirconium — the main ingredient in the metallic outer shell of a fuel rod, known as the cladding.
A slide with a cutaway illustration of a reactor featured a glowing hot mass of melted fuel rods in the middle of the core and noted “release of fission products” during meltdown.
The products are radioactive fragments of split atoms that can result in cancer and other serious illnesses.
Stanford, where Dr. Hansen is a visiting scholar, posted the slides online after the March presentation.
At that time, each of the roughly 30 slides was marked with the Areva symbol or name, and each also gave the name of their author, Matthias Braun.