Molten salt reactors require an external chemical plant processing radioactive materials. Radioactive chemical plants are a huge headache. If anything goes wrong, there's a huge mess and another long-term toxic waste site. Hanford (a PUREX plant) and Pantex (in Texas) are both now toxic waste sites.
Every nuclear reactor design that has something complicated going on in the radioactive section has had serious problems. Gas-cooled reactors leak. (Ft. St. Vrain was so promising.) Pebble bed reactors jam. (The one in Germany is permanently jammed and can't be disassembled.) Sodium reactors have sodium fires. Ones with attached chemical plants have problems with handling of hazardous materials. It's discouraging.
Ordinary water-based reactors have a simple radioactive section. All the complexity is outside. Yet even those have problems.
Hyman Rickover on this subject:
An academic reactor or reactor plant almost always has the following
basic characteristics: (1) It is simple. (2) It is small. (3) It is
cheap. (4) It is light. (5) It can be built very quickly. (6) It is
very flexible in purpose ("omnibus reactor"). (7) Very little development is required. It will use mostly “off-the-shelf” components.
(8) The reactor is in the study phase. It is not being built now.
On the other hand, a practical reactor plant can be distinguished by the
following characteristics: (1) It is being built now. (2) It is behind
schedule. (3) It is requiring an immense amount of development on
apparently trivial items. Corrosion, in particular, is a problem.
(4) It is very expensive. (5) It takes a long time to build because of
the engineering development problems. (6) It is large. (7) It is
heavy. (8) It is complicated.
Every nuclear reactor design that has something complicated going on in the radioactive section has had serious problems. Gas-cooled reactors leak. (Ft. St. Vrain was so promising.) Pebble bed reactors jam. (The one in Germany is permanently jammed and can't be disassembled.) Sodium reactors have sodium fires. Ones with attached chemical plants have problems with handling of hazardous materials. It's discouraging.
Ordinary water-based reactors have a simple radioactive section. All the complexity is outside. Yet even those have problems.
Hyman Rickover on this subject:
An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose ("omnibus reactor"). (7) Very little development is required. It will use mostly “off-the-shelf” components. (8) The reactor is in the study phase. It is not being built now.
On the other hand, a practical reactor plant can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem. (4) It is very expensive. (5) It takes a long time to build because of the engineering development problems. (6) It is large. (7) It is heavy. (8) It is complicated.