Radiochemistry:

Radiochemistry is the chemistry of radioactive substances that uses radioactive isotopes of elements to study the properties and chemical reactions of non-radioactive isotopes (in radiochemistry, isotopes are stable in the absence of radioactivity substances are often described as inert). Much of radiochemistry deals with the use of radioactivity to study ordinary chemical reactions. This is very different from radiochemistry, where the radiation level is too low to affect the chemistry.