are produced in a negative beta decay
. In a nuclear reactor
occurs especially the β− decay, because the common feature of the fission fragments
is an excess of neutrons
. The existence of emission of antineutrinos and their extremely low cross-section
for any interaction leads to very interesting phenomenon. Roughly about 5% of released energy
per one fission is radiated away
from reactor in the form of antineutrinos.
For a typical nuclear reactor with a thermal power of 3000 MWth (~1000MWe of electrical power), the total power produced is in fact higher, approximately 3150 MW, of which 150 MW is radiated away into space as antineutrino radiation. This amount of energy is forever lost, because antineutrinos are able to penetrate all reactor materials without any interaction.
In fact, a common statement in physics texts is that the mean free path of a neutrino is approximately a light-year of lead. Moreover, a neutrino of moderate energy can easily penetrate a thousand light-years of lead (according to the J. B. Griffiths).