Yes.

From Wikipedia:

Plutonium is identified as either weapons-grade, fuel-grade, or reactor-grade based on the percentage of 240Pu that it contains. Weapons-grade plutonium contains less than 7% 240Pu. Fuel-grade plutonium contains 7%–19%, and power reactor-grade contains 19% or more 240Pu. Supergrade plutonium, with less than 4% of 240Pu, is used in United States Navy weapons stored near ship and submarine crews, due to its lower radioactivity.

Weapon Grade Plutonium has lower concentration because Plutonium has a high rate of spontaneous decay which means it leads to issues with detonations in bombs.