History, description, effects and uses of radioactivity

<p>Some big atomic nuclei are very fragile, like uranium-235 and plutonium-239. The capture of a neutron by these so-called fissile nuclei causes them to explode into two fragments accompanied by several secondary neutrons. This explosion releases a very high energy, much higher than that of conventional energy sources.</p> <p>See also:  <a href="http://laradioactivite.apps.wok.in2p3.fr/nuclearenergy/fission_products">Fission energy</a></p>

<p>The most common measurement is that of the radiation exposure dose over a certain period of time, using dosimeters worn by the exposed persons. This is done for personnel who may be exposed to radiation, for example in a nuclear power plant or research facility. Small radiation counters, such as Geiger counters, are also used to monitor the evolution of radioactive activity from one place to another.</p> <p>See also : <a href="http://laradioactivite.apps.wok.in2p3.fr/questions_of_doses/active_dosimeters">Dosimetry</a>, <a href="http://laradioactivite.apps.wok.in2p3.fr/laboratoire-en/geiger_counters">Geiger Counters</a></p>

<p>Natural radioactivity is not dangerous. Exposure to radiation can become dangerous when the source of radiation is intense (in the case of certain therapies) or during major nuclear accidents. There are ways to protect oneself, such as the protective barriers implemented around nuclear reactors.</p> <p>See also: <a href="http://laradioactivite.apps.wok.in2p3.fr/in_daily_life/natural_exposures">Natural and artificial radioactivity</a></p>