I think you will find that every facility is different, but I understand that PRN work can mean per diem, and it can also mean working in the float pool at one facility.

I know of some hospitals that have created their own internal registry program, where they guarantee PRN nurses a certain number of hours and provide benefits.

I have been preimium pool now for 3 years. That is PRN where I am. I work 48 hours a week and refuse extra shifts on a regular basis. Truth is that I could work 24, X7 if they could get me to do it. It really depends on the facility. Try it, if it does not work you can change your status in 6 months, or get another job.