分裂 ぶんれつ物質 ぶっしつではありませんでした
bunretsubusshitsudewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 分裂物質

1. Was not a fissile material.; Was not a splitting substance.

Past/Perfective
Negative
Polite
Formal Register