The only way to prevent prisoner on prisoner rape is to put Chasity belts on them.... or build them little individual houses with showers, a bathroom, and nice kitchenette, and their own personal exercise yard.
Actually, the way to do this would be to put closed circuit cameras in every part of the prison (including showers, prison guard locker rooms and toilets), and require the warden to keep - on pain of dismissal with revocation of pension and imprisonment - several years worth of video archives. The ACLU, which would probably sue to prevent this, is going to go apeshit, but cameras everywhere would also do a number of contraband smuggling and other categories of crime.
I am for individual cells with a toilet.
I don’t think they’d need kitchenettes, and they could be rotated in and out of exercise yards - no need for a private one.
It could be easily done and I don’t know why we aren’t doing it.