Hi Teige,
Okay this did the trick and this is what I did:
-I downloaded and installed KB3134758: Update voor Windows Server 2012 R2
-rebooted
-repaired the PowerShell installation, because I already had installed it
Now when I do right click on the sever wihtin SSMS version 17.2 I get the PS prompt
PS SQLSERVER:\
And it was even available after a reboot of the SQL server.
So thanks Teige for helping me out. Great.
kind regards
Marco