Simplify the following text for a Grade 8 native English-speaking person.
Original: Nuclear weapons deliveryâ '' the technology and systems used to bring a nuclear weapon to its targetâ '' is an important aspect of nuclear weapons relating both to nuclear weapon design and nuclear strategy .
Simplified: Iran is believed to be making nuclear weapons , but they say they are just making nuclear energy . When countries get or try to get nuclear weapons , it is called nuclear proliferation .