Complex sentence: Among those, 247 Cm and 248 Cm are popular in scientific research because of their long half-lives, however, the production rate of 247 Cm in thermal neutron reactors is relatively low because of its strong fission induced by thermal neutrons.
Split into simpler sentences: Among those, 247 Cm and 248 Cm are popular in scientific research because of their long half-lives. However, the production rate of 247 Cm in thermal neutron reactors is relatively low because of it is prone to undergo fission induced by thermal neutrons.