user: Question: What reactor type that has a commercial operation of —, and a Tianwan-7 unit?
Columns: ['Unit', 'Reactor type', 'Net capacity', 'Gross capacity', 'Construction started', 'Electricity grid', 'Commercial operation', 'Shutdown']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Tianwan-1', 'VVER -1000/428 ( AES-91 )', '990 MW', '1,060 MW', '20 October 1999', '12 May 2006', '17 May 2007', '—']
SQL:

assistant: SELECT "Reactor type" FROM "Table" WHERE "Commercial operation" = '—' AND "Unit" = 'Tianwan-7';