Forget about getting from the Radisson Narita to the city easily. Explore the Narita area instead. Most of the airport hotels have shuttles (generally to the train station)to the nearby town. It is kind of fun to see "suburban" Tokyo. Pick up a train ticket to the main nearby station (trains about every 10 minutes) to see what
"crossroads" types of areas are like--department stores, apartment areas. I had fun on a 20 hour layover just in the NRT area 2 years ago--just soaking it in!