There are plenty of volatile fission products in a molten salt reactor. For example, at MSRE, a large fraction of the iodine went completely missing and no one

There are plenty of volatile fission products in a molten salt reactor. For example, at MSRE, a large fraction of the iodine went completely missing and no one to this day knows where it went. Capable and redundant containment systems are absolutely necessary in these reactors.