即発 そくはつ中性 ちゅうせい じゃなかったです
soku hatsu chūseikojanakattadesu

Noun
Desu Copula

The polite, past negative form of 即発中性子

1. Wasn't an immediate neutron.; Wasn't a prompt neutron.

Past/Perfective
Negative
Polite
Casual Register