Design and evaluation of Operation Grade Decay Heat Removal System of PFBR

The decay heat removal (DHR) system removes the decay heat generated (by radioactive decay of fission products) in the core after the reactor is shut down, thereby ensuring proper cooling of the core sub assemblies and limiting main vessel, internals and sodium temperature within safe limits. There are two diverse paths for removal of decay heat from the reactor, namely, Safety Grade Decay Heat Removal System (SGDHRS) and Operation Grade Decay Heat Removal System (OGDHRS). OGDHR circuit is used when at least one secondary sodium loop, DHR related steam water circuit and off site power supply is available and SGDHR circuit is used when OGDHR system is not available or when both the secondary loops are not available for DHR. This paper provides brief details of the design and evaluation of OGDHRS.

► DHR system removes radioactive decay heat of fission products in the core after shutdown.
► There are two systems – Operation Grade Decay Heat Removal System (OGDHRS) and Safety Grade Decay Heat Removal System (SGDHR).
► OGDHRS is used when offsite power, one secondary sodium loop and the steam water system are available.
► SGDHR is a passive system with sodium-in-sodium heat exchanger and sodium to air heat exchanger used when OGDHRS becomes unavailable.
► OGDHRS is a robust system with adequate redundancy to take care of the operational needs and anticipated occurrences.