Fralink,
Some radiation patients will develop urinary retention and that may be treated with a catheter and a bag. Perhaps that happened with your husband. Definitely ask why your husband had to have a bag, and you might inquire as to why you weren't told the reason at the time.
When you get an answer, I hope you will feel comfortable sharing it with us. You'll find a lot of sharing. Indeed, sharing can be a comfort but only if you're comfortable doing so.
Prostate Veteran