How secure is the radius encryption

[Thomas Glanzmann]

Hello,
I wonder if the radius encryption between radius client and radius is
secure enough if you choose a decent password like the following:
'O([G6krj\9[9FN#GVn(/|9+8h5vq2!W*J:OrA;2Uvk1G&*z~-6'emgQV 2X5iD>a('
Or if someone should always protect the connection between radius client
to radius server using ipsec or some other VPN software like for example
openvpn? I don't want to do radius over the internet but in a coporate
intranet. However I want also to absolutly sure that noone is reading my
pap passwords on the wire between radius client and radius server.

Cheers,
        Thomas