Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

What is a liquid fluoride thorium reactor? Is it a proven technology that has been tested and released to market or still in research and development (R&D) phase?

 A liquid fluoride thorium reactor (LFTR) is a type of nuclear reactor that uses thorium, a naturally occurring radioactive element, as fuel. It is designed to operate using liquid fluoride salts as both a coolant and a means of transferring heat to generate electricity.

LFTRs are a type of advanced nuclear reactor that is still in the research and development phase. While the concept of using thorium as fuel in a nuclear reactor has been around for several decades, the development of a practical and viable LFTR has not yet been achieved.

LFTRs have several potential advantages over traditional nuclear reactors, including the ability to operate at higher temperatures, a higher fuel utilization efficiency, and a reduced proliferation risk. However, there are also significant technical and economic challenges that need to be addressed before LFTRs can be deployed at a commercial scale.

As a result, LFTRs are currently in the R&D phase and have not yet been tested or released to the market. Further research and development is needed to determine whether LFTRs can be designed, built, and operated safely and effectively, and to assess their potential economic viability as a source of electricity.