user: Question: When did the Electricity Grid 28.12.1972 officially shutdown?
Columns: ['Unit', 'Reactortype', 'Net capacity', 'Gross capacity', 'Construction started', 'Electricity Grid', 'Commercial Operation', 'Shutdown']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Novovoronezh-1', 'VVER-210 (prototype)', '197 MW', '210 MW', '01.07.1957', '30.09.1964', '31.12.1964', '16.02.1988']
SQL:

assistant: SELECT "Shutdown" FROM "Table" WHERE "Electricity Grid" = '28.12.1972';