Nuclear Production of Hydrogen, Fourth Information Exchange ...

NUCLEAR HYDROGEN USING HIGH TEMPERATURE ELECTROLYSIS AND LIGHT WATER REACTORS FOR PEAK ELECTRICITY PRODUCTION
• Response time. When a reactor is kept operating at high power output and the plant electricity
is used for operating an electrolysis system, the electricity can be switched in a fraction of a
second from the electrolysis plant to the electrical grid. The fast response times enables this
system to be used to regulate the electrical grid (see section entitled Economics).
Oxy-hydrogen steam turbine
The storage of oxygen and hydrogen at pressure provides a second method of peak electricity
production: the oxy-hydrogen steam turbine (Figure 2). Hydrogen, oxygen, and water are fed directly
to a burner to produce high pressure, very high temperature steam. Because the combustion
temperature of a pure hydrogen-oxygen flame is far beyond that of current materials of construction,
water is added to lower the peak temperatures. The technology is that of a low-performance rocket
engine. The resultant steam is fed directly to a very high temperature turbine that drives an electric
generator. Through the use of advancing gas turbine technology with actively cooled blades, it is
expected that peak steam temperatures at the inlet of the first turbines can approach 1 500°C. The
projected heat-to-electricity efficiency for advanced turbines approaches ~70%, starting with compress
oxygen and hydrogen from the storage facilities.
The technology is based on ongoing development of an advanced natural gas electric plant that
uses oxygen rather than air (Anderson, 2004) Combustors with outputs of ~20 MW(t) are being tested.
With a feed of natural gas and oxygen, a mixture of steam and carbon dioxide is created. After it
passes through the turbine to the condenser, the steam is condensed and the carbon dioxide is
available for: i) injection into oil fields to increase the recovery of oil and/or ii) sequestration. The
higher heat-to-electricity efficiency and the production of a clean carbon dioxide gas stream for
long-term sequestration of the carbon dioxide greenhouse gases has created strong incentives to
develop oxy-fuel combustors for burning of fossil fuels.
Figure 2: Oxygen-hydrogen-water steam cycle
06-016
Hydrogen
Steam
Turbine
Oxygen
Burner
Steam
1500º C
Generator
Water
Cooling
Water
In
Out
Pump
Condenser
The capital costs (Forsberg, 2009b) for the oxy-hydrogen steam turbine system are significantly
less than those for any existing methods to convert fossil fuels to electricity. The low capital-cost
peak-power production technology is the natural-gas-fired combined-cycle plant with a high
temperature gas turbine producing electricity and the hot gas turbine exhaust being sent to a steam
boiler with the steam used to produce additional electricity. As is the case for traditional combined
cycle plants, the turbine remains in the oxy-hydrogen steam cycle but the need to compress air as an
oxidiser is eliminated, as well as the massive gas flow of nitrogen (80% of air) through the system.
Equally important, the expensive high-surface-area boiler in the combined-cycle plant is also
eliminated. These changes simultaneously increase efficiency (55 to 70%) and lower the capital costs.
The low capital costs relative to any other method of peak electricity production allow the peak power
system to be sized independently of the reactor or hydrogen production system.
160 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010