Fission chain reaction control: system

management and protection

The main tool for the control and management of nuclear reactions

it is the control and protection system (CPS). Principle of operation

The CPS is as follows: to prevent the very rapid multiplication of neutro-

nov, leading to a nuclear explosion, materials are introduced into the core,

absorbing neutrons (so-called “absorbers”). One of the most popular

boron (B), more precisely, its isotope 10 V.

as absorbers in modern power reactors used

use rare earth elements: gadolinium (Gd), erbium (Er), euro-

pi (Eu). Structurally, the absorbers are made in the form of vertical

rods that move up and down the core of the by means of a special mechanism.

Accordingly, if we need to “accelerate” the reactor (raise

Figure 4.5 – Reactor cores

Figure 4.4 – Arrangement of the core and fuel assembly

(view from above) its power), the control rods are lifted from the core. Wherein

the amount of the absorber decreases, which leads to an increase in

throne flux, which means an increase in the number of acts of fission of ura-

per unit of time. In this case, the reactor power (i.e. heat,

removed from the core per unit of time) increases.

If necessary, on the contrary, reduce power or stop completely

reactor, then the control rods are introduced into the core. In this case, the neutron

flux decreases until complete attenuation, when the quantities

there are not enough neutrons to sustain the chain reaction.

The structure also includes CPS rods emergency protection: at WHO-

in the event of an emergency or pressing the emergency protection button

they fall into the active zone, providing instant cessation

chain reaction, i.e. shutdown of the reactor.

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