Radioactive decay

Radioactive Decay

Some large atoms produce static sounds on a radio, so are known as radio active. This radio activity is due to spontaneous decay of atoms.

The half life of an isotope is the time it would take for half the nuclei to decay.

The decay processes give off, Alpha, beta, and/or gamma rays. They were named before scientists knew what they were.

Alpha rays are high speed nuclei of helium atoms.

Beta particles are high speed electrons. They are produced when a neutron decays to a proton and an electron plus an antineutrino.

Gamma rays are high energy photons which are electromagnetic waves. They carry off excess energy.

U238 decays in a number of steps showing each type of decay.

Alpha decay

Alpha decay




Beta and gamma decay of Thorium 234

Ref: More detail

Powering spacecraft

Spacecraft operating for many years use the decay of Plutonium as their heat source.

On Nov. 26, 2011 NASA launched ‘Curiosity’, the largest, most capable rover ever sent to another planet. Radioactive decay of 4.8 kilograms of plutonium dioxide will produce a steady flow of heat to warm the rover’s systems during the intensely cold Martian night and allow electricity to be generated. Image: NASA.

The Voyager 2 spacecraft, launched on Aug. 20, 1977, is about 14 billion kilometers (9 billion miles) from the sun. It is the longest continuously operating NASA spacecraft. It owes its long life to radioisotope thermoelectric generators; these generate electricity from heat flowing from plutonium-238′s radioactive decay. Image: NASA.




Geothermal heat

The heat in the Earth's crust comes from radioactive decay of Uranium 238 and Thorium 232. It produces 20 trillion watts. This causes the convection currents driving plate tectonics and volcanoes.

Radioactive decay accounts for half the heat of the earth. The heat in the core is from the formation of the Earth.