Here is a survey on status of the work around the world on Thorium nuclear fission reactors and molten salt reactors. Molten Salt reactors may be safer than current reactors and could close the nuclear fuel cycle and some designs can eliminate the longest lived nuclear waste. Molten Salt reactors potentially eliminate the need for both fuel enrichment and fuel fabrication, both major expenses.
I would bet on Czech, India to build a Thorium reactor first.
Japan, Norway could also get involved early.
Canada or France could help make one for someone else (probably India)
India is developing the Advanced Heavy Water reactor (AHWR) as the third stage in its plan to utilise thorium to fuel its overall nuclear power program. The AHWR is a 300 MWe reactor moderated by heavy water at low pressure. The calandria has 500 vertical pressure tubes and the coolant is boiling light water circulated by convection. Each fuel assembly has 30 Th-U-233 oxide pins and 24 Pu-Th oxide pins around a central rod with burnable absorber. Burn-up of 24 GWd/t is envisaged. It is designed to be self-sustaining in relation to U-233 bred from Th-232 and have a low Pu inventory and consumption, with slightly negative void coefficient of reactivity.
High Temperature Reactors (HTRs) can potentially use thorium-based fuels, such as HEU with Th, U-233 with Th, and Pu with Th. Most of the experience with thorium fuels has been in HTRs.
A larger US design, the Gas Turbine – Modular Helium Reactor (GT-MHR), will be built as modules of 285 MWe each directly driving a gas turbine at 48% thermal efficiency.
South Africa’s Pebble Bed Modular Reactor (PBMR) is being developed by a consortium led by the utility Eskom, and drawing on German expertise.