Mail about duplicate rows

I am trying to append a table radius from another table radiustemp, both
having the same structure, but want to append only those tuples from
radiustemp which are not there in radius. The size of the table can be
up to 165 MB.
So anyone can suggest me a better way of doing this.

The structure if table is like this .

Table    = radius
+----------------------------------+----------------------------------+-------+

|              Field               |              Type                |
Length|
+----------------------------------+----------------------------------+-------+

| uname                            | char()
|   256 |
| logdate                          | date
|     4 |
| logtime                          | time
|     8 |
| duration                         | int4
|     4 |
| status                           | char()
|    20 |
| nasadd                           | char()
|    20 |
| port                             | int4
|     4 |
| bytesin                          | int4
|     4 |
| bytesout                         | int4
|     4 |
| packin                           | int4
|     4 |
| packout                          | int4
|     4 |
| misc                             | int4
|     4 |
+----------------------------------+----------------------------------+-------+

Thank's in advance for your help.

Thanks & regards,
Vicky