Lättvattenreaktor

Lättvattenreaktor, often abbreviated as LWR, is a type of nuclear reactor that uses ordinary water as both a coolant and a neutron moderator. This is in contrast to other reactor types that might use heavy water or graphite. LWRs are the most common type of nuclear reactor globally, powering a significant portion of the world's nuclear electricity generation. There are two main designs of light water reactors: the Pressurized Water Reactor (PWR) and the Boiling Water Reactor (BWR).

In a PWR, the primary coolant water is kept under high pressure to prevent it from boiling. This hot, pressurized water then flows to a steam generator where it transfers its heat to a secondary loop of water, causing that water to boil and produce steam. This steam then drives a turbine connected to an electric generator. In a BWR, the water is allowed to boil directly within the reactor core. The steam produced in the core then directly drives the turbine.

LWRs are chosen for their relatively simple design, established safety record, and the availability of ordinary water as a moderator and coolant. The fuel used in most LWRs is enriched uranium, typically in the form of uranium dioxide pellets encased in zirconium alloy cladding. The control of the nuclear reaction is achieved through control rods, which absorb neutrons and can be inserted or withdrawn from the core to regulate the power output.