Can I safely nail a wall's top plate to a laminated beam?
Go ahead and put that wall right on under that beam. The beam is a bearing surface for what is up above the beam. The wall you are adding is a non bearing wall that will not hinder the bearing capacity of the beam. Nail it in place using standard nailing practice. In other words, don't load it up with no more nails than you need, one nail staggered every 16", 2 on the ends. 

The thing about the non-bearing wall you are building, it can never be made a bearing wall unless you do something with the floor it sets on. The reason why I bring this up, it is possible that in the future, and it is highly unlikely that somebody at some time sees this wall under the beam and thinks "well this wall is under this portion of this beam and I need to run such and such through this area, I will just cut it out since there is this wall under it." WRONG. The beam MUST remain intact as if there is no wall under it.