Regional Basic Professional Training Course in Korea

Regional Basic Professional Training Course (BPTC) on Nuclear Safety
234
Th90 -----> 234
Pa91 + β- [5]
Gamma radiation, (γ) belongs to a class known as electromagnetic radiation. This type
of radiation consists of quanta or packets of energy transmitted in the form of a wave.
Some well-known members of this class of radiation are radio waves and visible light.
Another type of electromagnetic radiation, which in most aspects is identical to gamma
radiation, is x-rays. For radiation protection purposes, the electromagnetic spectrum may
be divided into two portions: one potion called ionizing radiation extends from the very
shortest wavelengths to until about several nanometres. Electromagnetic radiations of
these wavelengths include x-rays and gamma rays. The main difference between these
two types of radiation lies in their origin: γ rays results from changes in the nucleus,
whereas x-rays are emitted when electrons undergo a change in velocity.
Radiation energy is expressed in units called electron volts(eV). One electron volt is the
energy gained by an electron in passing through an electrical potential of one volt. The
electron volt is an extremely small unit, so radiation energies are usually expressed in kilo
(1000) electron volts (keV) or mega (1,000,000) electron volts (MeV).
1 MeV = 1000 keV = 1,000,000 eV
The decay of a radioactive sample is random and therefore statistical in nature. The result
of this uncertainty is that the radioactive decay law is exponential in nature and is
expressed mathematically as:
N = No e -λt
[6]
where No is the number of nuclei present initially, Nis the number of nuclei present at a
later time, t, and λ is the decay constant.
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