Question: when did the us start using nuclear energy
[{'answer': 'April 1957', 'provenance': [{'wikipedia_id': '4131402', 'title': 'Nuclear power in the United States', 'start_paragraph_id': 15, 'start_character': 155, 'end_paragraph_id': 15, 'end_character': 165, 'bleu_score': 1.0, 'section': 'Section::::History.:Start of commercial nuclear power.\n'}]}, {'provenance': [{'wikipedia_id': '4131402', 'title': 'Nuclear power in the United States', 'start_paragraph_id': 15, 'start_character': 0, 'end_paragraph_id': 15, 'end_character': 1038, 'bleu_score': 0.9666950091602231, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1001800096889960544}, 'section': 'Section::::History.:Start of commercial nuclear power.\n'}]}]