Restkern

Restkern is a German term that translates to "residual core" or "remaining core." It is most commonly used in the context of nuclear reactors and refers to the nuclear fuel that remains within the reactor core after a period of operation and subsequent refueling.

During the operation of a nuclear reactor, nuclear fuel is consumed through fission. Over time, the concentration of fissile isotopes decreases, and the accumulation of fission products, which can absorb neutrons, reduces the reactivity of the fuel. This necessitates refueling, where spent fuel assemblies are removed and replaced with fresh ones. The fuel assemblies that are removed but still contain a significant amount of fissile material and are not yet fully depleted are considered restkern.

This restkern is typically stored temporarily in spent fuel pools at the reactor site. It continues to generate decay heat and emit radiation, requiring careful management and cooling. Eventually, the restkern may be processed for reprocessing to recover valuable fissile materials like plutonium and uranium, or it may be designated for long-term disposal as radioactive waste. The handling and management of restkern are crucial aspects of nuclear safety and waste management strategies.