Sci fi movie name?

I saw a movie as a kid in the 1960s but cant rememeber the name.

Definitely a “b” movie. Might have been made for tv but i dont think so. I think the movie was made in the 1950s or 1960s and was in black and white.

Its about a group of survivors from either a nuclear war or radiation accident who are living/surviving in a mountain fallout shelter presumably designed by the government or military for just this situation. There are mutant dead people who terrorize the survivors and make there way into the tunnels of the mountain. The mutants walk slowly and are held off by the survivors using some sort of wall.

I want to say that there are scenes where the survivors are out walking around in the forests of the mountains and i want to say the location is pennsylvania or west virginia. I forget how it ends but the movie has haunted me ever since..even worse that i cant watch it again since i cant figure out the name!!!

Bill