Is Atomkraftwerk der, die or das?

The correct German article for Atomkraftwerk is das. The noun Atomkraftwerk is Neuter. So you always say: das Atomkraftwerk. Learn the article together with the noun — German nouns don't follow predictable gender rules most of the time.

The plural of Atomkraftwerk is: die Atomkraftwerke. In the plural, every German noun takes the article "die". So: die Atomkraftwerke. Example: ein Atomkraftwerk → zwei Atomkraftwerke.

Correct: die Atomkraftwerke. The form "die Atomkraftwerks" is wrong. The plural of das Atomkraftwerk is die Atomkraftwerke. In the nominative plural, you always use the article "die".

das Atomkraftwerk follows the four German cases. Nominative: das Atomkraftwerk, Accusative: das Atomkraftwerk, Dative: dem Atomkraftwerk, Genitive: des Atomkraftwerks. In plural: die Atomkraftwerke / den Atomkraftwerken. Learn these forms together with the noun.

The genitive singular of das Atomkraftwerk is: des Atomkraftwerks. The genitive plural is der Atomkraftwerke. German uses the genitive to express possession or belonging. Example: die Farbe des Atomkraftwerks.

The dative plural of Atomkraftwerk is: den Atomkraftwerken. In German, dative plural nouns usually end in "-n". So you say: "mit den Atomkraftwerken". Use this case after prepositions like mit, von, bei, zu.

Atomkraftwerk is a noun and must be capitalized in German. You'll find example sentences above for each case. The article das stays the same in nominative singular but changes in other cases. Practice declension in your own sentences.

Yes, Atomkraftwerk is a noun (also called a substantive). German nouns are always capitalized. The article for Atomkraftwerk is das. Every German noun has a fixed article you must memorize.