They apparently can control the reaction so they will work either as a disintegrating ray or as an explosion like our atomic bomb.
6 seconds sound clip from the Radar Men from the Moon - Molten Terror (S1E2) movie soundboard.
You can hear this line at 00:03:30.465 in the Blu-ray version of the movie.
Quote context
[...]
- So Retik plans to invade the Earth with his army from the Moon.
- As soon as the saboteur's, he already has their finish softening up our defenses.
- Do you think he'll be able to do it?
- What did you find out about the ray guns?
- Then hadn't we better go back right away and warn our people?
- No.
[...]