suppliers of technology and parts and less expertise at least initially than for decades old proven technology or its evolutionary improvements such as generation III+ reactors. However, LWRs were developed in the 1950s based on the subcritical fossil fired power technologies. The success of LWRs is based on that experience. Supercritical fossil fired power plants were developed after 1950s. Components such as valves, piping, turbines, feedwater pumps and heaters for operation at turbine throttle pressure up to 30MPa and temperature up to 630C are present for commercial applications. SCWRs are natural evolution of LWRs. The competitiveness of LWRs in the electricity market is being challenged in the US due to Shale gas from historical summaries of U.S. Energy Information Administration’s (EIA’s) Levelized cost of electricity(LCOE) projections (2010-2020) in Cost of electricity by source. LWRs are the dominant design with the largest share of nuclear power generation and are the current offering for new construction in the world. Innovation dynamics show that innovation does not come from companies with the largest market share. Comparing SCWRs and LWRs is not relevant in terms of innovation dynamics. If Small modular reactor(SMR) is competitive, a SMR version of SCWRs will increase its advantage. • The chemical shim might behave drastically different as the solution properties of supercritical water are vastly different from those of liquid water. Currently most pressurized water reactors employ boric acid to control reactivity early in burnup. However, chemical shim cannot be used in SCWRs as well as BWRs, due to the positive coolant void coefficient. SCWRs use borated water as the secondary shut-down similar to BWRs. •Depending on design online refuelling may be impossible. While CANDUs are capable of online refuelling, other water moderated reactors are not. However, the Capacity factor of LWRs is already high in USA, over 90%. Pressure vessel type SCWRs do not require online refuelling. See also Generation IV reactor Breeder reactor Reduced moderation water reactor, a concept that is in some ways similar and in others overlapping to the SCWR concept, and is under development apart from the Generation IV program. Generation III reactor Advanced Boiling Water Reactor (ABWR) Economic Simplified Boiling Water Reactor (ESBWR) (generation III+) References INL SCWR page INL presentation INL Progress Report for the FY-03 Generation-IV R&D Activities for the Development of the SCWR in the U.S. Generation IV International Forum SCWR website. INL SCWR workshop summary External links Idaho National