Emergency Core Cooling Systems encompass all of the emergency systems used 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. Inside of the RPVRPVReactor Pressure Vessel - contains all of the reactor heat. In BWR reactors, the RPV contains the reactor core - basically the entirety of the main reactor assembly. The RPV is designed to withstand a very large amount of force considering that in a BWR it must withstand the pressure that both it operates at and at emergency designs -- this is due to the fact that in most designs, the RPV isn't considered to be at major risk: even during a major LOCA the RPV is considered to be at healthy condi 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, LOCALOCALoss of Cooling Accident - inside of Nuclear Reactors, this is the official term for if there is a loss of coolant used to cool the reactor. \#stub, 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 design, so variations may be included. For example, PWR reactorPWR reactorThis reactor is a PWR reactor - a pressurized water reactor. This is a specific type of Nuclear Reactor--in that it is pressurized water. This is also the most common type of reactor used and produced. The fuel rods are pressurized with helium, and the fission gas products result in more stability; as fuel "burns" in the reactor, the density increases resulting in small voids developing. Helium pressurization is necessary as these voids can cause potential rupture of fuel rods. Furthermore, thes and BWR reactorBWR reactorA boiling water reactor uses Light Water as both coolant and neutron moderator. The second most used reactor, next to the PWR reactors, there are approximately 75 plants in current operation. The efficiency of these reactors is about 46%, with 33-34% in practice. Enriched uranium is used as nuclear fuel, as light water absorbs too many neutrons to use Uranium that is natural. Light water is not as good of a moderator compared to Heavy Water or graphite, but it is good as in the event of a LOCA os require different emergency systems due to their differing reactor containment and cooling supplies.

BWR Primary Cooling Systems (inclusive of other types)

IMPORTANTLY, these cooling systems are NOT defined as ECCS Systems. However, for simplicity, they are listed here as they are part of emergency core cooling and therefore deserve mention

Reactor Core Isolation Cooling

RCIC allows for water to enter the RPV for cooling even when the steam lines are isolated and the main water supply to reactor is lost. This is initated either on low water level or manually

The RCIC system is driven using steam from the main steam lines and this exhaust is routed to the suppression pool. This turbine runs a pump that drives water from either the CSTs or suppression poool.

Standby Liquid Control System

The Standby Liquid Control System injects Boron, which is a neutron poison (Boron is also used in Control RodsControl RodsControl Rods are rods that are used to control the rate of reaction inside and within a Nuclear Reactor. They have a specific design that allows for this control. BWR reactor parameters In the GE Marathon control rod, it contains stainless steel tubes filled with boron carbide poison. This isotope contains a high cross-section for the absorption of neutrons, acting as a control rod neutron poison. These control rods are uniformly placed into a reactor core according to its design parameters.). This is injected into the RPV to shutdown the chain reacton, and is completely independent on the control rods. It uses explosive valves that are manually initated to slowly achive reactor shutdown conditions.

BWR Official ECCS Systems

There are 4 official ECCS systems: HPCI and ADS, and LPCI and CS, the former being high pressure and latter for low pressure.

High Pressure ECCS

These systems have the priority to reduce the pressure of the RPV to a mangeable level, and ensure ample water in the RPV.

High Pressure Coolant Injection

HPCI is an independent ECCS requiring NO aux AC, air, or cooling water systems to provide cooling water to reactor vessel for small and medium LOCAs. the HPCI can provide makeup water using vessel pressure enough to the point that LPCI systems can take over.

Automatic Depressurization System

ADS consists of redundant logics that can open small relief valves to depressurize reactor if HPCI is unavailable or cannot recover RPV water level.

Low Pressure ECCS

These systems are for after the RPV is depressurized to maintain water level of the reactor and also reduce temperatures to ensure claddingCladdingCladding is the thin walled metal tube that composes the outside of a fuel rod. It's purpose is to prevent corrosion of the fuel by the coolant & release of fission contents into the coolant. Although Zirconium alloy is common, aluminum and stainless steel is also used. Cladding Types Zirconium alloy has been used for so long due to it's properties being very good for nuclear reactors. * New research suggests that there is an alternative - SiGA cladding. This cladding is made from silicon car does not reach the point of creating hydrogen.

Low Pressure Coolant Injection

LPCI of the Residual Heat Removal SystemRHRThis page's sources are primarily from NRC ML11223A219 (Westinghouse Section 5.1) RHR or Residual Heat Removal is a system utilized in Nuclear Reactors 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 sa provides makeup water to the vessel under LOCA conditions. RHR has several modes for the same equipment. LPCI is the main mode and oeprates automatically. During this mode, water is taken from the supression pools and discharged into the RPV, via the recirculation pump output lines.

Containment Spray

Containment Spray can spray both suppression pools and the drywell, and have the same output lines as LPCI.

Core Spray

Core Spray is indepdent of LPCI and consists of two independent loops that can pump water from the suppression pool into the RPV, spraying water directly on top of the Fuel RodFuel RodsThis is a breakdown of how Fuel Rods work, for information on nuclear fuel itself, you want Nuclear Fuel. Fuel rods are made out of the fissile material that is wanted for the reactor, then experience different things. Uranium Dioxide fuel is pelleted and filled into metallic tubes, which have cladding of Zirconium or stainless steel, and then these tubes are sealed. In a PWR reactor, fuel is cylindrical rods into bundles, where fuel is bundled and the cladding gap filled with helium to help w assemblies