Babcock & Wilcox PWR[edit]

Barriers:

Redundant safety systems

Automated reactor protection system

4 layer radiation containment barrier, ceramic fuel design, fuel cladding, sealed steel pipe system, containment building

RCS Reactor coolant system

The reactor is made up of 4 systems. The primary loop/RCS which acts as the heat source, including the reactor vessel, the control rods, the fuel rods, the core flood tank, the pressurizer, the steam generator, the reactor coolant pump, and the containment sump

The secondary system is the power generating system including the turbines, the generators, the hot and cold legs of the steam circulation system, the feedwater and it's pump, the condenser, the cooling tower, it's basin, and the circulating water pump.

Then there are two more systems, the high pressure injection system, and the low pressure injection system. The HPI can deliver fluid to the reactor at regular operating pressure. Water withdrawn from the primary loop is passed through a heat exchanger to cool it before it's filtered, heated up in another heat exchanger, and then fed back into the primary system. Boron can be added from the borated water tank to moderate reactivity.

The LIP is used to cool the reactor down after shutdown passing water drawn from the design basis (ultimate heat sink, UHS) heatsink through the LPI heatsink and back into the primary system. The LPI can also pump water from the reactor sump, or the borated water tank.

Reactor Coolant Systems

Reactor

The pressurizer controls the pressure of the reactor. It has heaters to manipulate temperature, and water sprayers for condensing the steam volume and lowering pressure.

The reactor vessel (RV) and reactor coolant system are usually constructed of carbon steel with the interior surface weld clad with stainless steel to reduce corrosion.

The b&w design uses two once through steam generators.

The reactor coolant pumps use 3% of the power generated by the plant, e.g. 30MW for a 1GW reactor.

There are 4 different types of rods. Safety rods provide the safe shutdown margin, which is a boilerplate item on the reactor license. Safety rods are retracted upon during reactor startup, during shutdown, and in case of a SCRAM.

Regulating rods are used to control reactor power during regular operation and are also used during shutdown.

Axial power shaping rods are only used to control neutron flux imbalances in the core. Only the bottom of the rod has neutron absorbing material.

Burnable Poison Rods are another type. When a fresh load is added to a reactor the reactivity is much greater than needed to compensate for decay over the useful span of the fuel.

The Emergency Core Cooling System (ECCS) is composed of three systems, the high pressure injection system, the core flood system, and the low pressure injection system.

The Ultimate Heat-Sink is a guaranteed water source for decay heat removal following a design bias accident.