Question: when was nuclear power first used to generate electricity
[{'answer': 'December 20 , 1951', 'provenance': [{'wikipedia_id': '22153', 'title': 'Nuclear power', 'start_paragraph_id': 33, 'start_character': 69, 'end_paragraph_id': 33, 'end_character': 87, 'bleu_score': 1.0, 'section': 'Section::::History.:First nuclear reactor.\n'}]}]