Light-water reactor

Light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator. This distinguishes it from other types of nuclear reactors such as heavy water reactors, graphite-moderated reactors, or fast neutron reactors. LWRs are the most common type of nuclear reactor in use for power generation today.

History

The concept of the light-water reactor was first proposed in the United States in the early 1950s. The United States Navy was the first to use LWRs for its nuclear submarines, with the launch of the USS Nautilus (SSN-571) in 1954. The success of this project led to the development of commercial LWRs for power generation.

Design and operation

The design of a light-water reactor is characterized by its use of light water (ordinary water) as both a coolant and a neutron moderator. This dual role allows the reactor to maintain a stable and self-sustaining nuclear chain reaction.

The core of an LWR contains fuel rods made up of uranium or plutonium that undergo nuclear fission when struck by a neutron. The heat generated by this process is transferred to the water, which is circulated through the reactor core. The heated water then travels to a steam generator, where it transfers its heat to a secondary loop of water. This secondary water loop turns into steam, which drives a turbine connected to an electric generator.

Types of light-water reactors

There are two main types of light-water reactors: the pressurized water reactor (PWR) and the boiling water reactor (BWR).

Pressurized water reactor

In a pressurized water reactor, the water in the reactor core is kept under high pressure to prevent it from boiling. The heated water from the reactor core is sent to a steam generator, where it heats a separate loop of water into steam. The steam then drives a turbine to generate electricity.

Boiling water reactor

In a boiling water reactor, the water in the reactor core is allowed to boil into steam. This steam is directly used to drive a turbine to generate electricity.

Safety and environmental considerations

Light-water reactors are designed with multiple safety systems to prevent nuclear meltdown and the release of radioactive material. However, accidents such as the Three Mile Island accident and the Fukushima Daiichi nuclear disaster have raised concerns about the safety of LWRs.

From an environmental perspective, LWRs produce no greenhouse gas emissions during operation. However, the mining and enrichment of uranium, as well as the disposal of nuclear waste, do have environmental impacts.

See also

• Nuclear power
• Nuclear power plant
• Nuclear fuel cycle
• Nuclear safety