Nuclear Production of Hydrogen, Fourth Information Exchange ...

PRESENT STATUS OF HTGR AND HYDROGEN PRODUCTION DEVELOPMENT IN JAEA
Figure 8: Concept of H 2 SO 4 decomposer and mock-up model
Thermal
insulation
SO 3 +H 2 Ooutlet
He outlet
H 2SO 4
outlet
Full scale
SiC block
He inlet
SiC
block
SiC block
He
inlet
f0.7m
m
.1
3
m
.5
1
Gasket
(Au)
f 0.25m
H 2 SO 4 inlet
He outlet
H 2SO 4 inlet
Mock-up
model
Future perspective
The original proposal for the first commercial-scale HTGR plant, the GTHTR300, combines a 600 MWt
reactor and a direct cycle gas turbine for sole generation of electric power. The detailed design of the
GTHTR300 has involved to the extent verifiable by tests of gas-turbine components such as a
compressor and a magnetic bearing of appropriate scale, and has carried preliminary safety analysis
and economical evaluation. The design of the GTHTR300 evolved to a hydrogen cogeneration system,
named the GTHTR300C. In the GTHTR300C, an intermediate heat exchanger (IHX) is used to transfer a
share of reactor thermal power to secondary helium which is delivered in piping as high temperature
process heat to a distant IS process hydrogen plant which has a capacity of hydrogen production rate
of about 0.6 × 106 Nm 3 /d. The electricity need for hydrogen production is met in-house from the efficient
gas turbine power cogeneration of 200 MWe. Providing a seawater desalination plant making fresh
water at a rate of 90 000 tonne/d, the GTHTR300C has a thermal efficiency of about 80%, which can be
called a HTGR cascade energy plant.
Figure 9 shows a conceptual layout of the GTHTR300C. The commercial plants of the GTHTR300C
will consist of four reactors operating in parallel, adapting the same system arrangement of the
GTHTR300. The nuclear produced heat is transported by the second helium circulation loop over a safe
distance to the hydrogen plant inside a coaxial hot gas piping, which is a proven component of the
HTTR. As for the baseline design of helium gas turbine is a single-shaft, axial-flow design having six
turbine stages and twenty non-intercooled compressor stages. The gas turbine rated at 200 MWe and
3 600 rpm drives a synchronous generator from shaft cold end by a diaphragm coupling. The machine
is placed horizontally to minimise bearing loads. These design features have been chosen in accord
with established industrial air gas turbine practice. The new gas turbine elements incorporated in the
baseline unit are the narrow compressor flow path, which results from working in helium gas, and the
use of rotor magnetic bearings to avoid pressure boundary penetration and potential lubricant
contamination to reactor system. The development and test programmes have been carried out for
validation of these new technology components uniquely present in this application.
Hydrogen demand would grow quickly by 2020 after a primary stage by 2010, followed by wide
and rapid expansion thereafter (NEDO, 2005). Until 2020, hydrogen is to be produced still with existing
methods such as steam reforming of fossil fuels and cokes oven gas in steel works and electrolysis at
a hydrogen station. In order to meet a substantial demand of hydrogen at the matured stage beyond
2020, however, technologies of HTGR hydrogen and coal reforming hydrogen shall be developed and
deployed. In the coal reforming, technology for carbon dioxide sequestration should be developed
(NEDO, 2005). In addition, renewable energy hydrogen would share specific demand of hydrogen.
Since the HTGR hydrogen production system can produce massive hydrogen as previously shown, it is
expected to be one of most promising systems in the future hydrogen economy.
NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 53