Nuclear Production of Hydrogen, Fourth Information Exchange ...

NUCLEAR HYDROGEN USING HIGH TEMPERATURE ELECTROLYSIS AND LIGHT WATER REACTORS FOR PEAK ELECTRICITY PRODUCTION
System description
The proposed system has four major components (Figure 1):
• Steam production. Light water reactors produce steam. The power plant may operate as a
conventional nuclear plant where all the steam is used to produce electricity. Alternatively,
electricity and some of the steam may be diverted to hydrogen production.
• Hydrogen production. Steam and electricity are used to produce hydrogen and oxygen using the
HTE process at times of low electricity demand.
• Hydrogen and oxygen storage. Underground storage facilities are used for the low-cost storage of
hydrogen and oxygen on a daily, weekly, and seasonal basis.
• Peak electricity production. Variable electricity production to match demand is achieved by two
methods: i) variable production of hydrogen and oxygen to storage when electricity is not
needed for the electrical gird; ii) using the hydrogen and oxygen for electricity production to
meet peak load demand. Peak electricity from hydrogen and oxygen can be produced by either
operation of the HTE system as a fuel cell or use of an oxygen-hydrogen steam turbine.
Figure 1: Peak power production system using high temperature electrolysis
From a system perspective, the high-capital-cost nuclear reactor operates at full power; but the
electricity to the electrical grid varies from zero (electricity and steam to hydrogen production) to
several times the electrical output of the reactor (reactor sends electricity to the grid and hydrogen is
used to produce added electricity). The characteristics of the system allow rapid variation in electricity
to the grid. This capability stabilises the grid, provides spinning reserve and provides peak electricity.
Hydrogen can also be sold to industrial markets. The hydrogen storage facilities enable supplying
hydrogen based on demand – independent of the instantaneous production rate.
Hydrogen production using high temperature electrolysis
The HTE/fuel cell system that converts steam and electricity to hydrogen and oxygen at times of low
electric demand can convert hydrogen and oxygen back to electricity at times of high electricity
demand. This reversibility, if it proves to be practical, significantly reduces the capital costs for peak
power production because the same equipment is used for hydrogen and electricity production. While
laboratory prototypes for electrolysis have been operating for some time, the technology is not yet
commercial. The electrolysis technology is based on the still developing but more advanced
solid-oxide fuel cell technology with operational temperatures near 800°C.
HTE is expected to be significantly less expensive than conventional electrolysis because it uses
heat and electricity (rather than just electricity) to supply the energy needed to convert water to
hydrogen and oxygen. Because heat is less expensive than electricity, this substitution reduces costs.
Heat reduces the electricity demand by two mechanisms:
NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 157