Overtrykkets

Overtrykkets, also known as the Overpressure, is a phenomenon observed in certain types of nuclear reactors, particularly those using heavy water as a moderator and coolant. It refers to a condition where the pressure inside the reactor core exceeds the expected or designed levels. This can occur due to various factors, including the accumulation of non-condensable gases, such as hydrogen and oxygen, produced during the fission process.

The primary concern with overtrykkets is the potential for the reactor to exceed its pressure limits, leading to a loss of coolant accident (LOCA). This can result in significant damage to the reactor core and other components, as well as the release of radioactive materials into the environment. To mitigate the risks associated with overtrykkets, nuclear reactors are equipped with various safety systems, such as pressure relief valves and emergency core cooling systems.

The phenomenon was first observed in the early 1960s in the CANDU (CANada Deuterium Uranium) reactors, which are designed to use heavy water as both a moderator and a coolant. Since then, extensive research and development efforts have been undertaken to better understand and manage overtrykkets in these reactors. Today, CANDU reactors are equipped with advanced safety features and operating procedures to minimize the risks associated with this phenomenon.