Nuclear Energy

iii. Gamma radiation: This is akin to X-rays. It is composed of photons, that is, high energy
light waves. It has great penetrating power and can travel large distances. Gamma radiation goes
straight through human bodies. As gamma rays pass through the body, they can mutate
regulatory or reproductive genes.
Radiation is measured in Becquerel (Bq). One Bq is defined as one disintegration per
second. Another unit is curie, defined as: Curie (Ci) = 3.7 × 10 10 disintegrations per second.
Half-life
Each radioactive isotope has a specific half-life. Half-life of an isotope is the amount of time
it takes for the half the number of atoms of that isotope to decay. For example, radioactive iodine
131 has a half-life of eight days, so that in eight days it loses half its radioactive energy, in another
eight days it decays again to one quarter of the original radiation, ad infinitum. The amount of time
taken by a radioactive isotope to decay to a harmless level can be obtained by a simple thumb rule:
multiply the half-life by 20. (There is of course no unanimity on this, with many experts saying that
radiation becomes harmless in 10 half lives.) Thus, in the case of iodine 131, its radioactive life is 8
x 20 = 160 days. Some isotopes created during the fission reaction in nuclear reactor have very
short half-lives (less than a second) and some extremely long (millions of years).
Radiation and reproduction
Part II: Radiation and Human Health lxii
Instructions providing all the information necessary for a living organism to grow and live
reside in every cell of the body of the organism. These instructions are stored in a molecule called
the DNA, or Deoxyribonucleic acid, whose shape is like a twisted ladder, called a “double-helix”.
The DNA molecules are stranded together like letters in a sentence, and these strands are called
genes. Genes are packed into thread like structures, called chromosomes. All the genes come in
pairs, and in the human cell they are organised into the two sets of 23 chromosomes. The human
cell thus has a total of 46 chromosomes.
Genes are the very building blocks of life, responsible for every inherited characteristic in
all species – plants, animals, and humans. Every person inherits half of his/her genes from the
mother, and half from the father. While every human cell has 46 chromosomes, the egg and sperm
have 23. At the time of conception, the mother’s egg cell unites with the father’s sperm, to form the
zygote, which has a full complement of 46 genes. This cell then duplicates itself, and develops into
the child. Most genes are the same in all human beings, which is why all human beings are similar.
A small number of genes are different, and it is these which are responsible for each human being’s
unique features.
Radiation can induce mutation, that is, a chemical change, in the DNA molecule, thereby
causing a change in the gene. If this mutation takes place in the reproductive gene, then it can cause
the most unexpected changes in the offspring. This can be understood from the fact that according
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