This article is not ready to be a Good Article, for many reasons. You may wish to peruse WP:What is a Good Article? or look through other articles at WP:GA, but I'll my best to explain what the problems are.
Per WP:Verifiability, every controversial statement needs a reference. This is pretty much every statement, unless it is patently obvious. This means that almost all of the article requires a citation. There are far too few references provided in the article at the moment.
Citations require details that allow others to verify the statement. Given than weblinks sometimes break, this means providing things like the page's title, date, author, work and publisher. If you use a template like ((cite web)) for web links, then the fields should provide a guide as to what it is necessary to include (not all the fields, but at least some).
Layout. The long-list format doesn't work very well. If you look at WP:LAYOUT, then you will see that bullet points are only suitable for lists of short items, unlike in the article at current. Instead, the sections should be divided into groups and each point presented in a paragraph.
Prose. There are some problems, such as fuel / breeding and conversion to an insoluble form such as a glass, could be desirable. There are also some non-encyclopedic parts such as An excellent detailed technical description of the 1970s development status and knowledge of the molten salt breeder reactor (MSBR) that the ORNL program was working on is available online in a single large document.. I suggest a copyedit from the Guild of Copyeditors, once you've seen to the other problems.
Lead. Bit difficult to follow; doesn't make much mention of the advantages/disadvantages which occupy most of the article. It's the part which needs to be best explained to the lay reader.
Following on from this there is some attempt at an accessible introduction, but it's still very hard to understand. The explanation is basic in some respects, but jargon remains difficult for the lay reader.
Images: mostly fine, although File:Lwrvslftr2.png looks a bit suspicious. Sub-images are included, but their copyright status isn't clear.
Feel free to renominate the article once these issues have been addressed. Grandiose(me, talk, contribs) 18:58, 18 June 2012 (UTC)[reply]