Terms to Know

Alpha radiation -ionizing, particulate radiation having low penetrating power.

Background (Natural) Radiation - the radiation that has always been present in the environment and is produced by natural sources such as cosmic rays and radioactive elements in the ground, building materials and the human body.

Beta radiation - ionizing, particulate radiation having more penetrating power than alpha radiation.

Community Alert Siren System - an audible system of sirens throughout the Emergency Planning Zone intended to notify residents in the case of an emergency at a nuclear plant.

Containment -  the structures which enclose the reactor, designed to prevent the escape of radiation from the reactor to the outside environment. Some reactors of the former Soviet Union (i.e. Chernobyl’s RBMK) do not have containment structures. The containment structure consists of layers of steel and reinforced concrete.

Control rods - movable rods made of neutron-absorbing material that are used to regulate the nuclear fission process in a reactor.

Core - the central portion of a nuclear reactor containing the fuel rods and control rods. Nuclear fission takes place and heat is generated within the core.

Decommissioning - the process of closing down and removing a nuclear reactor after its useful life has come to an end.

Electrical Switchyard - a facility where electricity from the electrical generator is transferred to the electric grid.

Electricity - a form of energy An electric current is a stream of electrons.

Electric grid - a large interconnection of both generation and transmission electrical subsystems to facilitate efficient distribution of electricity to consumers and businesses.

TOP

Emergency Broadcast System (EBS) - a network of radio and television stations which may be accessed by appropriate government officials, on a regional or national basis, to communicate emergency information to the public in the event of a serious natural or manmade emergency, including a nuclear power plant accident.

Emergency Planning Zone (EPZ) - the area around the plant which could be affected if an accident occurred.

Enriched Uranium - uranium in which the naturally occurring proportion of uranium which can be readily split (fission ) is increased. For use as fuel in a nuclear power plant, it is increased from less than 1 percent to between 3-5 percent. To produce an atomic bomb requires enrichment to 90 percent.

Fission - the splitting of atoms, which results in the release of large amounts of energy. Fission occurs naturally or when an atom's nucleus is bombarded by neutrons.

TOP

Fuel rods - metal rod in which uranium in the form of ceramic pellets are contained.

Gamma radiation - ionizing, electromagnetic radiation having high penetrating power. Similar to x-rays.

High-level wastes - used (spent) fuel rods from a nuclear power plant.

Low-level wastes - materials containing comparatively low levels of radioactivity.

Megawatts - standard measure of electrical power. One megawatt equals one million watts or a thousand kilowatts.

Neutron - an uncharged subatomic particle. Neutrons sustain the fission process in nuclear reactors.

TOP

Nuclear Regulatory Commission (NRC) - the federal governmental agency that regulates, inspects, and oversees nuclear power plants to ensure they are safe.

Pressurized Water Reactor (PWR) - a light water reactor in which the water used as a moderator is kept under pressure preventing it from boiling.

Public Education Zone (PEZ) - an area 10-20 miles from the plant, outside the Emergency Planning Zone (EPZ), in which educational information regarding nuclear emergency planning and safety is provided .

Radioactivity - the process in which atoms undergo internal change with the resultant emission of electromagnetic or particulate radiation.

Radiological Controlled Area - work areas where potential radiation exposure exists, requiring monitoring to ensure minimal levels of exposure to employees.

TOP

Radon gas - a radioactive gas which comes from the earth's crust. Radon contributes about two thirds of human exposure from natural background radiation.

Renewable resources - resources (i.e. wind, solar) that can be used over and over again to produce energy.

Spent fuel - used fuel rods.

Steam generator - a huge radiator where heat from the primary (reactor coolant) loop is transformed to the secondary (steam) loop without mixing of the two streams of water.

Turbine - connected to the electrical generator, high pressure steam is driven against the blades of the turbine causing the turbine to rotate.

TOP

Uranium - naturally occurring radioactive chemical element found in the earths crust. Used as fuel at nuclear power plants. See enriched uranium.

X-Rays - electromagnetic radiation similar to gamma radiation.

Major Components

Reactor

A reactor vessel with 8-inch thick steel walls houses the fuel rods. Within the reactor vessel, nuclear fission--the process of splitting atoms of uranium to release energy--occurs. This energy heats pressurized water to more than 600 degrees Fahrenheit without boiling. During the reactor operation, water flows rapidly through the reactor vessel.

This water serves two key purposes. It acts first as a coolant to transfer heat from the fuel rods to the steam generator. Second, it slows down neutrons and increases the probability of fission. Just as in a baseball game -- where a batter is more likely to hit a slow ball than a fast ball -- a slow-moving neutron is more likely to hit a uranium atom and split it.

The "moderating" effect of the water adds another safety feature. Any loss of water would slow down the chain reaction.

TOP

Fuel Rod Assemblies

Fuel rod assemblies include fuel rod bundles and control rods.

The fuel is made up of small uranium pellets, about as big as the end of a finger. These pellets are dense, ceramic materials placed end-to-end inside long metal tubes called fuel rods. The fuel rods are then grouped together in bundles, and arranged so that control rods can be placed between them.

Control rods are used to slow or stop the fission process. They are made with a substance that absorbs neutrons. Moving them in or out of the reactor controls the amount of heat being produced.

TOP

Steam Generation System

After leaving the reactor, the hot pressurized water passes through pipes submerged in cooler water in a steam generator. Within this generator, the pressurized water gives up its heat to a second, separate supply of water which boils -- making steam for the turbine.

After giving up its heat, the pressurized water recycles back to the reactor vessel to be reheated again.

The reactor vessel and steam generator are enclosed in a massive, reinforced, air-tight concrete structure, called the containment, with concrete and steel walls more than four feet thick.

TOP

Turbine/Generator

As in a coal, oil or natural gas power plant, this steam passes through a steam line and into a turbine generator. Steam striking the propeller-like blades causes them to rotate just as the wind blows the blades of a windmill.

This rotation of the turbine blades spins the shaft of the generator. Inside, coils of wire, and magnetic fields interact to produce electricity.

A third, separate cool water system from the ocean interacts with the steam to condense it back into water for recycling to the steam generator.

TOP