 Beryllium is also commonly used in some neutron sources in laboratory devices in which relatively few neutrons are needed ( rather than having to use a nuclear reactor , or a particle accelerator @-@ powered neutron generator ) . For this purpose , a target of beryllium @-@ 9 is bombarded with energetic alpha particles from a radioisotope such as polonium @-@ 210 , radium @-@ 226 , plutonium @-@ 239 , or americium @-@ 241 . In the nuclear reaction that occurs , a beryllium nucleus is transmuted into carbon @-@ 12 , and one free neutron is emitted , traveling in about the same direction as the alpha particle was heading . Such alpha decay driven beryllium neutron sources , named " urchin " neutron initiators , were used some in early atomic bombs . Neutron sources in which beryllium is bombarded with gamma rays from a gamma decay radioisotope , are also used to produce laboratory neutrons . 
