Talk:Loki (Warframe)/@comment-70.241.17.97-20140613103533/@comment-91.65.132.148-20140613132232

Let's bring a quote on the table:

"Survival Void mission will have a chance to yield one of the following in every 5 minutes:

Orokin Cell,  Fusion Core, or Prime components listed below.[1]

However, the 20th minute will guarantee a Prime component[1] ."

So, you can get it on every 5 minute mark. You are just guaranteed any of the possible prime components at the 20 minute mark. It's the same for Defense: a prime part guaranteed at wave 15, but you could also get it in any other wave.