What is the nuclear war movie called that ends with a family taking drugs to die before radiation comes?

I am trying to find a movie that I watched awhile back, but can not remember the name. The movie has to do with the after effects of a nuclear war scenario. At the end of the movie a family takes some sort of drug to die so that they don't die from the radiation headed their way (i think they are in australia at the end of the movie). I watched it in various parts on youtube.What is the nuclear war movie called that ends with a family taking drugs to die before radiation comes?
It might be "On the Beach".