TNAG-1508-FCO40-2066-Guangdong-nuclear-power-station-project-at-Daya-Bay-safety-c-1987 — Page 122

AYAQ

1099

In

lies

The

HOW NUCLEAR ENERGY IS RELEASED

structure the atom is like a solar system.

The nucleus

in the centre, surrounded by negatively charged electrons.

substance of an atom is almost entirely concentrated in

the

nucleus,

which

is

charged protons made up of positively charged

and

neutrons

which carry no charge.

The number of electrons

in an

atom is

equal to the number of protons in its nucleus,

So the

atom is neutral.

The hydrogen atom

composed

is

one proton

one electron

The

oxygen

of

is

composed

atom of

and

eight

eight

protons, neutrons

and

eight

trons.

elec-

The uranium

atom

is composed of 92 protons, 146, 143 neutrons or 142 and 92 electrons. These three types of uranium atoms are known as ura- nium 238, uranium 235 and uranium 234.

metallic element.

Uranium

is

a heavy

Natural

uranium

is

made up

of three

isotopes.

Uranium pellet

Uranium-235: Content

Uranium-238: Content 99.28% Uranium-234: Content 0.0058%

0.71%

Uranium

lore

Uranium-235

occuring

is

the only naturally

nuclear

easily fissionable

element. Plutonium-239 and uranium-233

are also easily fissionable, but are not

naturally

8

occurring

and

must

be