The first barrier designed to prevent an inadvertent release of radioactive material from the reactor core is the nuclear fuel rod itself.

During normal operations, approximately 99 percent of all fission products remain trapped within the fuel's structure very near the point at which they were generated by fission.

The fuel cladding which encases the nuclear fuel is designed to contain the remaining 1 percent. The release of fission products from the fuel rods would require a breakdown of the fuel cladding. A fuel rod would need to heat up to over 3,500 degrees Fahrenheit before it would begin to break down.