H2-MHR Pre-Conceptual Design Report: SI-Based Plant; HTE-Based Plant

Abstract

Hydrogen and electricity are expected to dominate the world energy system in the long term. The world currently consumes about 50 million metric tons of hydrogen per year, with the bulk of it being consumed by the chemical and refining industries. The demand for hydrogen is expected to increase, especially if the U.S. and other countries shift their energy usage towards a hydrogen economy, with hydrogen consumed as an energy commodity by the transportation, residential, and commercial sectors. However, there is strong motivation to not use fossil fuels in the future as a feedstock for hydrogen production, because the greenhouse gas carbon dioxide is a byproduct and fossil fuel prices are expected to increase significantly. For electricity and hydrogen production, an advanced reactor technology receiving considerable international interest is a modular, passively-safe version of the high-temperature, gas-cooled reactor (HTGR), known in the U.S. as the Modular Helium Reactor (MHR), which operates at a power level of 600 MW(t). For electricity production, the MHR operates with an outlet helium temperature of 850°C to drive a direct, Brayton-cycle power-conversion system (PCS) with a thermal-to-electrical conversion efficiency of 48 percent. This concept is referred to as the Gas Turbine MHR (GT-MHR). For hydrogen production, the process heat from the MHR is used to produce hydrogen. This concept is referred to as the H2-MHR. The growing international interest in the MHR concept is the direct result of MHR design features, which include: (1) Passive Safety, Competitive Economics, and Siting Flexibility. The MHR does not require active safety systems to ensure public and worker safety. The high-energy conversion efficiency of the MHR, combined with the elimination of active safety systems, result in a design that is passively safe and economically competitive with other non-passively safe reactor concepts. Because of its high efficiency, the MHR rejects less waste heat than other reactor concepts. This design feature, combined with passive safety, allows for more flexible siting options for the MHR. (2) High Temperature Capability and Flexible Energy Outputs. The MHR is capable of producing process-heat temperatures of 950°C and higher. This high-temperature capability translates into a high-energy conversion efficiency for a variety of energy outputs, including electricity, hydrogen production, and synthetic fuel production. (3) Flexible Fuel Cycles. The MHR can operate efficiently and economically with several different fuel cycles. MHR designs have been developed utilizing low-enriched (LEU) uranium fuels, high-enriched uranium (HEU) fuels, mixed uranium/thorium and plutonium/thorium fuels, and surplus weapons-grade plutonium fuels. The thermal neutron spectrum of the MHR, combined with robust, ceramic-coated particle fuel, allow for very high burnup in a single pass through the reactor. More recently, an MHR design has been developed to deeply burn plutonium and other transuranic (TRU) actinides recovered from lig...

Tritium Barrier Materials and Separation Systems for the NGNP

“…The reduction in flux of tritium caused by diffusion of hydrogen was studied in the context of the Peach Bottom HTGR and tritium permeation by Richards et al [2,90]. In the study, the tritium flux through steam generators was calculated based upon the measured concentrations of hydrogen and tritium in the primary coolant, and the observed downstream permeation of tritium through the steam generator tube walls, which were composed of Alloy 800H.…”

Characteristic of the Pressurized Continuous Bunsen Reaction using HIxSolution

“…According to the previous works proposed for the SI process, the decomposition products in the HI decomposition section could be recycled as the form of the HI x (HI-I 2 -H 2 O) solution to the Bunsen reaction section [1,2]. Kim et al investigated the phase separation characteristics of the Bunsen reaction using the HI x solution.…”

Bifunctional Characteristics of Al2O3supported Ni in the HI Decomposition of Sulfur-Iodine Process

“…In the H 2 SO 4 decomposition process (Eq. (3)), H 2 SO 4 is decomposed into H 2 O, SO 2 and O 2 . Products of H 2 SO 4 decomposer are then fed back to Bunsen process.…”

“…(1)). I 2 is returned to Bunsen process as complexes of HIx·yH 2 O [2]. In the temperature range of 600 ~ 800 K, HI conversion is around 20 % in the equilibrium state.…”