Keep transaction log size under control during batch processing
Even with the SIMPLE recovery model, the trans log can still blow up if there's a long running transaction going on.  I'm wondering if something on your Dev server was running while your script was doing its thing and cause the trans log to not be able to truncate since the MinLSN was from some long running transaction.

To answer the question though, unless you restrict access to the DB (like running your script using ALTER DATABASE  SET RESTRICTED_USER WITH ROLLBACK IMMEDIATE or something similar like SINGLE_USER), there's no way you can force the log file to free space as other transactions may be running and the trans log has to stay consistent for those transactions.

Check TechNet (or BOL: Checkpoints and the Active Portion of the Log) for more information.