It is often incorrectly assumed that the combustion behavior of graphite is similar to that of charcoal and coal. Numerous tests and calculations have shown that it is virtually impossible to burn high-purity, nuclear-grade graphites. Graphite has been heated to Òwhite-hotÓ temperatures (~1650°C) without incurring ignition or self-sustained combustion. After removing the heat source, the graphite cooled to room temperature with a total mass loss of only a few percent. Charcoal and coal burn at rapid rates because:

• They contain high levels of impurities that catalyze the reaction.
• They are very porous, which provides a large internal surface area, resulting in more homogeneous oxidation.
• They generate volatile gases (e.g., methane), which react exothermically to increase temperatures.
• They form a porous ash, which allows oxygen to pass through, but reduces heat losses by conduction and radiation.
• They have lower thermal conductivity and specific heat than graphite.

In fact, because graphite is so resistant to oxidation, it has been identified as a fire extinguishing material for highly reactive metals, including zirconium.

The oxidation resistance and heat capacity of graphite serves to mitigate, not exacerbate, the radiological consequences of a hypothetical severe accident that allowed air into the reactor vessel. Similar conclusions were reached after detailed assessments of the Windscale and Chernobyl events; graphite played little or no role in the progression or consequences of the accidents. The Òred glowÓ observed during the Chernobyl accident was the expected color of luminescence for graphite at 700°C and not a large-scale graphite fire, as some have incorrectly assumed.