RHR

This page's sources are primarily from NRC ML11223A219 (Westinghouse Section 5.1) RHR or Residual Heat Removal is a system utilized in Nuclear ReactorNuclear ReactorIn it's most simplest form, a nuclear reactor uses Uranium and other radioactive materials and the fission from uranium to create heat, and transfer that heat into steam to create power. Nuclear reactors are one of the biggest sources of energy, although not renewable, uranium has a very high energy density resulting in massive power transmissions. There are many different types of nuclear reactors, and this term serves as a broad hub/introduction for each type. After uranium is used in reactos to manage the decay heat from the reactor. When a reactor is at its subcritical or shutdown stages, the fuel still produces heat that needs to be managed. During this period, RHR removes heat using heat exchangers and service water.

During shutdown, RHR reduces temperature of the core to safe temperatures. While in shutdown, RHR maintains the safe temperature until the next startup. RHR also serves an important role in the Emergency Core Cooling SystemsECCSEmergency Core Cooling Systems encompass all of the emergency systems used in Nuclear Reactors. Inside of the RPV of a reactor is the reactor core, which gets hot due to fission during operation. In the event that primary cooling systems go offline due to a powerloss, LOCA, or other reason, ECCS systems are automatically enabled. ECCS broadly describes all of the emergency systems used, however specific emergency systems can be used in isolation. Some ECCS systems are specified for a specific d offering LPCI support.

System Description

The RHR system has 2 heat exchangers, 2 residual heat removal pumps, and secondary systems. Inlet lines to the system connect to the hot leg of coolant, and output connect to the cold leg (since it is literally for heat removal). This cold leg injection is also what is used for LPCI injection.

The RHR suction line (water input) is normally isolated by valves - with a relief valve. each discharge line is isolated by both 2 check valves in containment and 2 motor valves outside containment. During cooling, water flows from hot leg, thorugh RHR heat exchangers, then into cold leg. Component cooling water is circulated through HE.

If 1 of the 2 pumps or heat exchangers is inoperable, cooling time is extended. Furthermore, each RHR system is connected to a different EDG electrical bus in the event of a LOOP or Loss of Off-site Power event.

ECCS Function

During a ECCS event, RHR is compined with high pressure ECCS, and it has the capability to inject Boron-water from the refueling CST to the cold leg. After injection, RHR provides recirculation for core cooling, using water from containment sump and using residual heat exchangers. If the pressure in the coolant coop is greater then the discharge pressure of the RHR, core water recovery can be provided using centrifugal pumps and injection pumps with the standard RHR discharge being used as a suction source for these pumps.

In a LOCA, fission products have the possibility to circulate outside of containment. If the pump seal fails, water spillage would occur inside of a shielded room - each pump is separately located and there are no interconnections for safety. Sump pumps and level instrumentation are also included in the case of spillage to deliver this water to the waste disposal.