According to the >a href=”http://nuclear.gov/HTGCR/overview.html” target=blank>U.S. Department of Energy, every 750 MWt of installed HTGR capacity will offset 1 million metric tons of CO2 emissions per year when compared to a similarly sized natural gas plant.
For the NGNP Alliance, choice of the Areva design, a reactor outlet temperature of 750C provides sufficient heat to produce conventional steam temperatures of 400-550C for applications like oil refinery distillation and chemical processing.
Southworth said the primary heat is carried from the reactor in a closed loop by helium and the steam is super heated but not super critical.
The NGNP Alliance is developing a regulatory strategy to identify key issues related to getting a license from the NRC. Southworth said the combination of licensing and building a first-of-a-kind unit could take 10-12 years to get one operating at a customer site. He estimates that with start-up schedules, the first customer would be reaping benefits from the technology in the time frame of 2024-2027. it could be sooner depending on the outcomes of design and regulatory processes and actual construction of a first-of-a-kind unit.
The (High Temperature Gas-Cooled Reactor) HTGR is a inherently safe, modular, underground helium-cooled nuclear reactor technology, The reactor and the nuclear heat supply system (NHSS) is comprised of three major components: the reactor, a heat transport system and a cross vessel that routes the helium between the reactor and the heat transport system
The NHSS design is modular with module ratings from 200 MWt to 625 MWt, reactor outlet temperatures from 700ºC to 850ºC, and heat transport systems that provide steam and/or high temperature fluids. The range of power ratings, temperatures, and heat transport system configurations provides flexibility in adapting the modules to the specific application.
The principal design objective of the NHSS is to ensure that there is no internal or external event that could lead to substantive release of radioactive material from the plant that would require evacuation or sheltering of the public or threaten food and water supplies. This objective is met by provision of:
• Multiple barriers to the release of radioactive material from the plant that will not fail under all normal, abnormal, and accident conditions whether affected by internal (e.g., loss of all electrical power, a leak in a steam generator tube) or external events (e.g., earthquakes, flooding, tornadoes). These barriers include:
o A robust carbon-based fuel structure that forms the princi- pal barrier to release and transport of radioactive mate- rial. As shown in Figure 2, the fuel is made up of minute (~1 mm diameter) particles that are comprised of multiple
ceramic layers surrounding the uranium based kernels. These ceramic layers are designed to retain the products of nuclear fission and limit release to the fuel elements and the helium coolant.
o Distribution and containment of the fuel particles in fuel elements (compacts or spheres) of carbon based material.
o Enclosure of the fuel elements in a large graphite core.
o Enclosure of the core structure and the helium coolant system in ASME Nuclear Grade metallic vessels.
o Enclosure of the NHSS vessels in a robust underground reactor building.
Additional reactor characteristics that prevent release of radioactive materials include:
• Extreme high temperature capability of the ceramic coated and carbon-based fuel and core structure.
• Reactor materials including the reactor fuel are chemically compatible and, in combination, will not react or burn to produce heat or explosive gases. Helium is inert and the fuel and materials of construction of the reactor core and the nuclear heat supply system preclude such reactions.
• Plant design features limit intrusion of air or water so that the reactor remains shutdown and containment of radio- active materials is maintained.
• Single phase and low heat capacity minimizes stored energy in the helium coolant.
• Inherent nuclear and heat transfer properties of the reactor design that are continuously functional to ensure that the fuel temperatures remain within acceptable limits under all conditions.
• Inherent properties of the reactor core that regulate nuclear power so no electrical power, coolant flow or any other
A potential for deployment of 510 GWt of HTGR technology by 2050 has been identified to fulfill the following industrial energy needs (Figure 7):
CO-GENERATION supply of electricity and steam to major industrial processes in petrochemical, ammonia and fertilizer plants, refineries and other industrial plants.
HYDROGEN production and supply to industrial plants and to the merchant hydrogen market.
ENHANCED RECOVERY and UPGRADING of Bitumen from oil sands (e.g., Alberta, Canada) requiring supply of steam, hydrogen, and electricity.
CONVERSION OF COAL AND NATURAL GAS TO LIQUID FUELS AND FEEDSTOCK requiring the supply of steam, electricity, and hydrogen.
ELECTRICITY generation and supply to the electrical grid.