Boiling water reactor how does it work

Circulation pumps integrated in the reactor pressure vessel mix the feed water pumped from the condenser with the water in the reactor pressure vessel that has not evaporated. Depending on the volume circulated, the temperature of the coolant flowing through the fuel elements changes. This also influences the share of steam in the area of the reactor core. Steam has a lower moderation effect than water.

The more steam there is in the area of the reactor core, the fewer nuclear fissions take place. Thus, the reactor power decreases negative steam bubble coefficient. By changing the speed of the circulation pumps, the reactor power can thus be influenced via the share of steam bubbles in the coolant water.

A lower coolant flow rate reduces the reactor power by increasing the share of steam bubbles, and vice versa. The reactor control rods containing neutron-absorbing material so-called neutron poisons are loaded into the reactor core from below and regulate the reactor.

In the event of a reactor trip the control rods are pneumatically "shot" into the reactor core, thus terminating the chain reaction. Cookies erleichtern die Bereitstellung unserer Dienste. Main Menu Zur Suche. Nuclear reactors are the heart of a nuclear power plant.

Nuclear Fission Creates Heat The main job of a reactor is to house and control nuclear fission —a process where atoms split and release energy. Fission and Fusion: What is the Difference?

There are two types of light-water reactors operating in America. Pressurized water reactors. Graphic by Sarah Harman U. Department of Energy. The core water cycles back to the reactor to be reheated and the process is repeated.

Boiling Water Reactors. The unused steam is then condensed back to water and reused in the heating process. See the section below to view a basic operating cycle of a boiling water power plant. Boiling water reactors must use enriched uranium as their nuclear fuel , due to their use of light water.

This is because light water absorbs too many neutrons to be used with natural uranium , so the fuel content of fissile Uranium must be increased. This is done through uranium enrichment —which increases the concentration of Uranium from 0. The enriched uranium is packed into fuel rods, which are assembled into a fuel bundle, as seen in Figure 3. There are about rods in each bundle, with up to bundles in a reactor. As mentioned before, light water is used as the coolant and moderator for a boiling water reactor.

Light water is much more abundant than heavy water, as it makes up The use of light water as a coolant is beneficial as it can cool down the fuel at the same time as it heats up to steam.

The steam moves through the turbines which spin a generator to generate electricity. This simplifies the design of boiling water reactors, as there is only one primary loop see Figure 4 needed which results in a lower cost of development. Light water does not make as good of a moderator as heavy water or graphite due to its relatively high absorption of neutrons.

However, its use as a moderator makes for an interesting and important safety feature; if there is a "loss of coolant accident: LOCA , the moderator will also decline, causing the nuclear chain reaction to stop.