Have any caves been spotted on the moon, in an area where Astronauts could potentially seek shelter from radiation?
There are a number of confirmed instances of caves on the Moon formed by old lava tubes (e.g.: here, here, and here). These could potentially form a very advantageous site for a lunar colony or base in the future.
Here is a formal study of the presence and possible usage of lava tubes, both on the Moon and Mars, for exploration and colonization purposes. Building a base in a lava tube has a number of attributes that makes it highly desirable for a lunar base or colony, in particular:
- Protection from radiation (as you noted)
- Minimal structural needs Using these tubes as structural support for a lunar colony could significantly reduce the amount of building materials that would need to be brought as payload. This could reduce building costs drastically.
- Simplified containment A long-term base or colony requires a lot of oxygen to stay sustainable, and lava tubes help to preserve this precious resource. First, it's relatively easy to seal the base off from the outside, just by filling in a few entryways. Second, oxygen can be easily extracted from the lunar soil/rock forming the walls of these structures.
- Constant temperatures By making the base underground, you get to avoid the temperature extremes that can occur on the surface. On the Moon, an underground base would have a year-round temperature of -20 °C (−4 °F), reducing the need for heavy temperature maintenance. The temperature could be raised by solar heaters on the surface, and since the base is contained underground, the heat would escape only very slowly.
- Exploration & research An underground base is probably one of the most lucrative spots for conducting scientific research and exploration on the Moon, since the lunar subterranean environment is still largely unexplored--especially if combined with a telescope on the surface without the interference of atmospheric distortion.
Yes -- if you count lava tubes. And why wouldn't you?