nuclear meltdown vs meltdown

nuclear meltdown and meltdown both are nouns.

Word	Noun	Adjective	Verb	Adverb
nuclear meltdown	Yes	No	No	No
meltdown	Yes	No	No	No

As nouns, nuclear meltdown and meltdown are synonyms defined as:

nuclear meltdown and meltdown: severe overheating of the core of a nuclear reactor resulting in the core melting and radiation escaping

nuclear meltdown (noun)	meltdown (noun)
severe overheating of the core of a nuclear reactor resulting in the core melting and radiation escaping	a disaster comparable to a nuclear meltdown
	severe overheating of the core of a nuclear reactor resulting in the core melting and radiation escaping