Radiance to Reflectance conversion


I want to convert the S3 radiance band into reflectance, for Sentinel 3 SLSTR products, but I dont know how to do it in SNAP.
Hope that somebody can help me

Optical -> Preprocessing -> Radiance-to-Reflectance Processor

A problem occurred during the target product initialisation. Type: OperatorException
Message: Sensor ‘OLCI’ not compliant with input product. Please check you selection.

Do you know why this error emerges?
I use the S3B level-1 radiance data.