We describe three partly-coupled integrated nuclear energy systems enabling base-load nuclear reactors to provide fully dispatchable electricity without greenhouse-gas emissions—replacing gas turbines burning natural gas and batteries storing electricity. First, electricity-to-high-temperature (1800˚C) gigawatt-hour firebrick heat storage converts low-price electricity to high-temperature stored heat to provide dispatchable heat for industry and power generation. Second, Nuclear Air-Brayton Combined Cycles (NACC) with thermodynamic toping cycles using high-temperature stored heat or combustible fuel provide dispatchable electricity. Peak power output can be 2 to 5 times base-load electricity production. The heat-to-electricity efficiency of the thermodynamic topping cycles exceeds 70%. Third, nuclear hydrogen production for industrial markets enables production of dispatchable electricity where hydrogen is used for energy storage but not for the production of heat and electricity. Base-load nuclear reactors send electricity to the grid and/or electrolyzers for hydrogen production depending upon electricity prices. Low-cost hydrogen storage enables meeting steady-state industrial hydrogen demand while hydrogen and grid electricity production are varied. Hydrogen production for industrial uses (ammonia fertilizer, direct reduction of iron ore to iron replacing coke, cellulosic liquid hydrocarbon biofuels replacing crude oil) may exceed 20% of total energy demand. Consequently, this option may become a major source of dispatchable electricity.