Question: when did the ussr became a nuclear power
[{'answer': 'August 29 , 1949', 'provenance': [{'wikipedia_id': '585704', 'title': 'Nuclear arms race', 'start_paragraph_id': 13, 'start_character': 430, 'end_paragraph_id': 13, 'end_character': 446, 'bleu_score': 1.0, 'section': 'Section::::Early Cold War.:Warhead Development.\n'}]}, {'provenance': [{'wikipedia_id': '585704', 'title': 'Nuclear arms race', 'start_paragraph_id': 13, 'start_character': 0, 'end_paragraph_id': 13, 'end_character': 622, 'bleu_score': 0.9815648442794911, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10732173881220764884}, 'section': 'Section::::Early Cold War.:Warhead Development.\n'}]}]