Inside the train car, the radiation starts to go up once the train enters Fukushima Prefecture from Sendai City in Miyagi Prefecture. The survey meter is at 0.1 microsievert/hour when the video starts, and goes up to about 0.5 microsievert/hour in about 5 minutes right before the train goes in the tunnel.
The person who posted this video on Youtube writes the highest was 0.9 microsievert/hour which is not shown in the video.
Remember JR East's "Must Go Now Or Never" campaign to bring young tourists to Fukushima? Did they say anything about radiation on board Shinkansen?