RADIATION PROTECTION - ILEA

Historical Prologue 7
P.3A Decay of the carbon-14 nucleus,
6
14
C.
The carbon-14 nucleus, with 6 protons and 8
neutrons, is not stable, because the ratio of
neutrons to protons is too high. The ratio is
changed by the spontaneous transformation of
one of the neutrons into a proton and the emission
of an energetic beta particle (negative)
from the nucleus. The average lifetime of the
nucleus is 8,250 years. After its decay, however,
the resultant nitrogen-14 nucleus (7 protons,
7 neutrons) is stable.
= Proton
= Neutron
{ β {
−
6p
8n
7p
7n
22
P.3B Decay of the sodium-22 nucleus, 11
Na.
The sodium-22 nucleus, with 11 protons and
11 neutrons, is also not stable. The ratio of protons
to neutrons is too high. The ratio is usually
changed by the spontaneous transformation of
one of the protons into a neutron and the emission
of an energetic positron (positive beta
particle) from the nucleus. About 10 percent of
the time, the ratio is changed by the capture
by a proton of an electron from an inner orbit,
which transforms it into a neutron. The average
lifetime of the unstable sodium-22 nucleus is
3.75 years. The resultant neon-22 nucleus (10
protons, 12 neutrons) is stable.
11 10
11 12
3 The Development of a Radiation Technology
After the discovery of the neutron, major developments in nuclear research
came in rapid succession: the discovery of uranium fission in 1939, and the
recognition of the possibility of releasing enormous amounts of energy;
achievement of the first self-sustaining fission reaction in a reactor in 1942;
explosion of nuclear fission devices in 1945; production of thermonuclear
explosions in 1952; commissioning of the first nuclear-powered submarine,
the Nautilus, in 1954; and the development of high-energy accelerators,
with energies over 10 9 electron volts (GeV) in the fifties and exceeding
10 12 electron volts (1 TeV) at the present time. The result of these
developments was the creation of an extensive radiation technology concerned
with the production of energetic radiations for use in research,
medical treatment, and industry.
β +
4 The Need for Radiation Protection
The development of a radiation technology left its occupational casualties—physicists,
radiologists, radiation chemists—researchers who investigated
the properties and uses of these energetic radiations without appreci-