AdvertisementNorth Dakota Prison Officials Think Outside The Box To Revamp Solitary Confinement07:03Download AudioResumeJuly 31, 2018Cheryl CorleyfacebookEmailChief of Security Joe Charvat walks the halls of the state penitentiary's Behavior Intervention Unit (BIU) — the prison's name for solitary confinement. Typically there are about 20 inmates in the cells, far fewer than in previous years. (NPR)