RADIATION EFFECTS IN ORGANIC COMPOUNDS
Figure 7 Effect of Gamma Radiation on
Different Types of Hydrocarbon
The stability of organic (and other covalent) compounds to radiation is frequently expressed by
means of the "G" value, which is equal to the number of molecules decomposed, or of product
formed, per 100 eV of energy dissipated in the material. As an example of the use of G values,
the data in Table 3 are for a number of polyphenyls exposed to the radiation in a thermal reactor.
The table shows the number of gas molecules produced, G(gas), and the number of polyphenyl
molecules, G(polymer), used to produce higher polymers per 100 eV of energy deposited in the
material. Note that this adds up to approximately 1000 atoms of gas and 10,000 atoms forming
higher polymers per each 1 MeV particle. It is also of interest to note that the terphenyls are
even more resistant to radiation than diphenyl and, since they have a higher boiling point, a
mixture of terphenyls with a relatively low melting temperature was chosen as the moderator-
coolant in organic-moderated reactors.