CREATE TABLE nuclear_power_plants (id TEXT, name TEXT, latitude TEXT, longitude TEXT, country TEXT, status TEXT, reactortype TEXT, reactormodel TEXT, constructionstartat TEXT, operationalfrom TEXT, operationalto TEXT, capacity TEXT, lastupdatedat TEXT, source TEXT)

Which country first started using nuclear power plant(s)?
SELECT country FROM nuclear_power_plants ORDER BY operationalfrom LIMIT 1
SELECT "country" FROM "nuclear_power_plants" ORDER BY "operationalfrom" NULLS FIRST LIMIT 1