Heaven Sent - S9-E12
Continuity mistake: When the Doctor is first shown discovering the word "bird" written in the sand on the floor of the teleport chamber, the handwriting changes from being somewhat messy in the wide shot to being perfectly neat in the close-up.
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.