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 reactor type has the largest average capacity?
SELECT reactortype FROM nuclear_power_plants GROUP BY reactortype ORDER BY AVG(capacity) DESC LIMIT 1
SELECT "reactortype" FROM "nuclear_power_plants" GROUP BY "reactortype" ORDER BY AVG("capacity") DESC NULLS LAST LIMIT 1