There is no supported way to simply rename a chunk.
You can only rename dbspace, blobspace.... by onspaces.
The only spported way of doing this would be to empty the chunk and then drop it and
create a new chunk. That of course means unloading and
reloading the data stored there.
Unofficially you can do this by binary editing data on the disk, but its dangerous and can lead to some corrupted chunk information.
ps: ontape can rename chunks only during cold restore.