Question: when did the chernobyl power plant go offline
[{'answer': 'June 17 , 2017'}, {'provenance': [{'wikipedia_id': '1238999', 'title': 'Chernobyl Nuclear Power Plant', 'start_paragraph_id': 28, 'start_character': 0, 'end_paragraph_id': 28, 'end_character': 172, 'bleu_score': 0.7701365065543351, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17945910410118588007}, 'section': 'Section::::Accidents and incidents.\n'}]}]