CREATE TABLE "list_of_most_powerful_nuclear_tests" (
  "date_gmt" text,
  "yield_megatons" text,
  "deployment" text,
  "country" text,
  "test_site" text,
  "name_or_number" text
);

Question: Name the name for 15 yield
SQL: SELECT "name_or_number" FROM "list_of_most_powerful_nuclear_tests" WHERE "yield_megatons"='15';