Nuclear Reactor

Nuclear Reactor

Control rods (Контролирани цилиндри)

These are made of steel containing a high percentage of material which can absorb neutrons, e.g. boron. Control rods are pushed into the core of the reactor. They control the amount of reaction and hence the amount of heat energy being produced. In emergency they can be used to shut down the reactor completely.

Coolant (Охлаждаща течност)

The nuclear reaction produces heat (parallel to the burning of coal or oil in a conventional power station). The coolant carries this heat away. 

The coolant is taken  by a pipe to the steam generator where water is boiled. This  is a heat-exchange process and it thereby lowers the temperature of the coolant which is then returned to the core to collect more heat.

Typical coolants are water, carbon dioxide gas, liquid sodium.

In a Boiling Water Reactor which operates at about 300 oC water is both the moderator and the coolant.

A Pressurized Water Reactor (PWR) operates at a slightly higher water temperature of approximately 320 oC.

A Gas-cooled Reactor operates at still higher temperatures.

Fuel (Гориво)

Typical fuels are uranium in the form of uranium or uranium dioxide; and plutonium 239P. Uranium dioxide is preferred to the metal as it has a higher melting point.

Fuel rod temperature under normal operating conditions is about 760 oC. The ceramic-fuel rod melts at about 2870 oC.

The world's first nuclear reactor was a natural reactor at Oklo in Gabon.

NB 1. Since the percentage of 235U in the fuel is too low the nuclear reactor cannot turn into an atomic bomb.

Moderator (Регулатор)

Only neutrons of a fairly low speed can produce fission of the uranium nuclei. Fast moving neutrons have their speed moderated (slowed) by passing through a moderator e.g. water, graphite or heavy water (D2O).

Други реферати:
Управление на националното развитие-проф. д.ик.н. Асен Ковачев
Статистика-учебно помагало
Икономика-пари и банки
БДС EN 12845
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