When they arrive from court to the Prison they get an interview from a Reception Officer, at this point the officer will ask what they are being sent to prison for, this generally gets asked so they can see if the person understands why they are here. They will then ask if the offence is Sexual Assault/Rape/Anything noncie if the want to take "the rule".
Prison Rule 45, Segregation from general population. This is offered or can be asked for. each request for Rule 45 OP (own protection) is considered and either accepted or denied based on the evidence given.
Prisons will have a VP (Vulnerable Prisoner) wing which sex offenders or nonces will get placed into should they accept Rule 45. They will be escorted everywhere on mass, separately from the general population by officers, they have separate exercise yards, separate visits and separate times for the library, gym and healthcare to keep their contact with the general population to a minimum.
Prisoners can deny the rule and live in general population. They are advised to cover up the nature of their crimes as staff will not be able to watch them or protect them at all times of the day. If they get "outed" they can be beaten rather severely before staff can respond.
All this "they will get bummed in prison" etc is pure Hollywood TV drama. Yes it does happen in Prison but not very often, think when I served, in 4 years we have maybe 3 reported sexual assaults in my prison. Some may not get reported however.
Some poeple mistake the VP wing as a "bacon wing" thinking that everyone there is a sex offender, some however just cannot cope in general population. Either poor copers, older prisoners who have had enough of the 19-25 year old hooligans types.
The VP wings are generally quiter as people know that they are there for protection and that life could be much worse, they tend to self police issues well, start up support groups and have lots of interaction with healthcare workers and councillors etc
I never agreed with the level of support they got and hated being anywhere near them. I found most of them devious and cunning. Officers in my prison would be asked if the wanted to work on the VP wing. Some said yes due to the quieter life, most said no as they didn't want to deal that type of person - I flat out said no 3 times that I was asked.
I was prepared to refuse a direct order should I be put in that position.