Nuclear Production of Hydrogen, Fourth Information Exchange ...

EXECUTIVE SUMMARY
the overall efficiency of a HTGR-IS system from about 50% to 55% to justify the use of nuclear heat to
produce hydrogen instead of electricity. Zr-V-F alloys were chosen because they have among the
largest enthalpy changes of the hydrogen-absorbing alloys. The heat pump is incorporated into the
three decomposition reactions in the cycle (H 2 SO 4 , HI and SO 3 ), in essence converting the enthalpy
change of the He coolant into enthalpy changes in hydrogen production thus leading to the higher
overall utilisation of the reactor heat.
Richard Vilam (DOE/ANL) presented a series of papers towards mitigating structural and
component failures in the heat transfer system and tritium migration between the nuclear reactor
and a high-temperature electrolysis (HTE) plant for producing hydrogen through the use of control
systems designed to minimise temperature differentials and more efficiently manage heat transfer
and the use of ceramic materials in place of metals. In his paper titled “Heat exchanger temperature
responses for duty-cycle transients in the NGNP/THE”, Vilam presented a control system for
moderating the differential temperature spatial distribution in the (IHX) during duty-cycle transients.
A dynamic systems simulation code was used to predict the plant response to transients such as
changes in the electric generator load during normal operation and loss of load when the electrolysis
plant goes off line. The study concluded that the plant load schedule could be managed to maintain
near-constant temperatures over the load ranges anticipated for both the nuclear and chemical plant
by use of a primary flow controller that forces flow tracked flow in the power conversion unit and a
turbine bypass control for responding to step changes in the generator load. The proposed control
scheme was shown to be effective in limiting temperature variations in the IHX during transients;
however, it was determined that more stable operation meant operating at points on the operating
curve that resulted in lower overall cycle efficiencies. In his paper titled “Alternate VHRT/THE
interfaces for mitigating tritium transport and structure creep”, Vilam noted that about 90% of the
heat transferred to the chemical plant is used at temperatures of below 250°C and described an
alternative interface between the nuclear and chemical plants which operated at temperatures
around 250°C. The small amount of high-temperature heat required by the HTE plant is obtained by
using either electric heaters or hydrogen combustion. By lowering the interface operating temperature,
both creep of structures and tritium migration were significantly reduced as well as structural
materials and maintenance costs. Overall plant efficiency for the alternative interface design was by
about 1.5% greater than that of a plant based on the conventional high-temperature interface design.
Closing session
Co-chairs: Yoshiyuki Nemoto (OECD/NEA), Theodore Krause (ANL)
The two co-chairmen expressed their great appreciation on behalf of the Organising Committee for
the interest and co-operation received from the authors, session chairman, panellists and audience.
It was unfortunate that some authors were unable to participate because their request for a visa for
entry into the USA could not be processed in time.
David Wade (ANL) briefly described the history of this series of OECD-NEA meetings. The
increasing number of papers submitted indicates a growing interest and greater awareness of the
importance of the topic. The first meeting held on 2-3 October 2000 in Paris, France, had a total of
20 papers. The second meeting held on 2-3 October 2003 at Argonne, IL, USA, had 22 papers. The third
meeting held on 5-7 October 2005 at Oarai, Japan, had 35 papers and the fourth meeting held on
14-16 April 2009 at Oakbrook, IL, USA, had 50 (46 oral + 4 poster) papers.
It was noted that the OECD/NEA has a long history of sponsoring joint projects of many types in
addition to information exchange meetings. Such projects have produced peer-reviewed databases,
calculational benchmarks, and special studies – many of which were very influential. The primary
objective of such joint projects is to share the costs of expensive projects and to provide access to the
information gained for the participating parties. Certain areas of the research and development for
the production of hydrogen from nuclear energy could be considered for such joint projects, and the
participants were encouraged to contact their national representative to the NEA Science Committee
if they wished to propose a project.
The audience indicated that the meeting had been found to be very useful. It was suggested that
in the future greater emphasis should be placed on the use of hydrogen, e.g. in the oil and chemical
industries.
18 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010