Llyn Brianne Dam: Dog-Walking and camping
Though it clearly is not allowed, I have seen mobile homes and campervans parked up in the quarry area by the dam. There are some discreet areas round the far end where you can 'hide'. I doubt there is much policing of this but it is not a designated campsite area.
However the roads are so narrow and windy in places that I would not consider it practical to drive a motor home or camper into this area. You certainly could not do the scenic drives in anything other than an ordinary car as some of the roads are a high gradient and have switchback curves.
Assuming you are staying at Craig y Nos Castle, you will not be needing to camp here. But to get in a good dog walk of say 7 or 8 hours, it is worth setting off early, parking up at the dam, and taking a picnic with you. For my own part, I like the circular drive around the reservoir, with a couple of hours allowed for the dog walk. There are several stop-off points around the reservoir where you can let the dogs out for a run before you get to the dam itself.
One of the stop-off points with a nice little private beach is shown in the picture above.