Decay heat removal systems in nuclear power plants

How do you remove decay / residual heat from a reactor core?

Methods for removing decay or residual heat from a reactor core can be grouped into two general categories: Closed-Loop System. One category includes methods that circulate fluid through the reactor core in a closed-loop, using some type of heat exchanger to transfer heat out of the system. Heat Removal through Steam Generators.

What is the power level of decay heat in a nuclear reactor?

The power level of the decay heat is approximately 6% of the reactor power when the reactor operates at nominal power. After the nuclear reactor is shut down under normal conditions, the residual heat and decay heat are transferred from the reactor core to the ultimate heat sink by a normal residual heat removal system (NRHRS).

How do you remove decay heat from a pressurized water reactor?

Decay heat removal using the feed-and-bleed method. The feed-and-bleed method for decay heat removal becomes a necessary method in some pressurized water reactors (PWRs) if there is a loss of steam generator heat sink capability.

Which passive decay heat removal systems are suitable?

Three classes of passive decay heat removal systems have been identified as suitable candidates: the reactor vessel auxiliary cooling system (RVACS) which is similar to that proposed for the GE S-PRISM; a DRACS similar to that used in the Experimental Breeder Reactor EBR-II; and a new pool reactor auxiliary cooling system.

When does a decay heat removal system become ineffective?

The technology of decay heat removal that relies on electric power, known as an active system, will become ineffective when there is a total loss of electrical power for an extended period (e.g., extended station blackout (SBO)), such as the accident at the Fukushima Daiichi Nuclear Power Plant.

What are decay heat removal systems?

The decay heat removal system designs feature any number of passive, highly-reliable, and/or redundant features to accomplish their heat removal function. Other safety related terms such as fault-tolerant, walk-away safe, fully passive, etc. are also used to describe the characteristics and performance of these systems.