They are interchangeable in some cases, but I would say hirune is a preferred choice when you intentionally set aside some time to take a nap. Uatatane is more like falling asleep without intending to.

昼寝, also called 午睡, means a midday nap. You may want to use these words when you sleep during daytime. うたた寝 means falling asleep for a short time without knowing. You can use this word either in the daytime or at night.

昼寝 is consciously taking a nap during day time during short time; on the contrary, うたた寝 is unconsciously falling asleep. For example of 昼寝, u try to sleep during day time when u don't have anything to do, consciously; and for うたた寝, if u take a bus, and ur destination is not so far away, u might try not to sleep; but, u already pass the destination when u realize next moment cuz u fall asleep, unconsciously. I hope these examples work for u to understand the difference:) Good luck with ur studying:)

昼寝 means sleep in the afternoon. うたた寝 Is nap. 昼 = afternoon 寝 = sleep