Use bpexpdate : Change the expiration date of backups in the image catalog and media in the media catalog.
For example:
bpexpdate -backupid eel_0904219764 -d 0 : expire an image
bpexpdate -m BU0002 -d 0 : expire a tape

make a file - I called it expire.bat
put this in it.  (if your install path is different please change it)

"C:\Program Files\VERITAS\NetBackup\bin\admincmd\bpmedialist.exe" -m %1
"C:\Program Files\VERITAS\NetBackup\bin\admincmd\bpexpdate.exe" -m %1 -d 0
"C:\Program Files\VERITAS\NetBackup\bin\admincmd\bpmedialist.exe" -m %1

save file.

expire.bat <TAPE NUMBER>

here is output

expire.bat H00006

Server Host = mymaster

id rl images allocated last updated density kbytes restores

vimages expiration last read <------- STATUS ------->

--------------------------------------------------------------------------------

H00006 12 2 08/13/2006 00:04 N/A dlt 122566743 0

MPX 10/19/2010 20:30 04/19/2010 18:57 IMPORTED

Media H00006 is due to expire at 10/19/2010 20:30:52

Are you sure that the data on this media is not critical to

your business, and you are sure you want to delete H00006 y/n (n)? y

requested media id is not assigned to this host in the EMM database

--------------
First it looks up the tape and shows it to you -
Then it asks if you really want to expire the images on the tape.
Then it looks it up again - this should have the error that it is not in the EMM database, meaning it was succesfull in expireing all the images on the tape.  If it comes back and shows you the tape info again - then it did not expire it.

I am Very Friendly with MS Excel So..

I used to go TLD and check for list of tapes to expire and select all of them and Press CTRL+C.

Open Excel CTRL+V. Delete all Fields except MEDIA ID. Insert a Column before that MEDIA ID Columns and Enter "bpexpdate -d 0 -force -m " and on column 3 enter "=CONCATENATE(A1,B1)" and the output will be "bpexpdate -d 0 -force -m MEDIAID"

Just drag this same formula for all Media's and copy all of these.

Goto CMD-> C:\INSTALPATH\Netbackup\Bin\Admincmd\ and paste those copied things ( or you can also paste in notepad and save as bat file and execute it)

Its more read all these lines but when you do it, it really 1 min job :-) no need to shake up your mind :-)