Nuclear Production of Hydrogen, Fourth Information Exchange ...

STATUS OF THE KOREAN NUCLEAR HYDROGEN PRODUCTION PROJECT
Candidate NHDD system
Considering economic production of hydrogen, the reaction temperature of a water-splitting process
should be above 850°C. To achieve this temperature at the chemical reactor, the nuclear reactor
should produce a heat of around 950°C. The NHDD reactor design aims at a 950°C outlet temperature
as the technology development target. To enhance safety and to reduce technical risk, the NHDD
reactor adopted a forged vessel with the conventional LWR pressure vessel material (Chang, 2007).
The power capacity is set as 200 MW thermal to stay within the current vessel manufacturing capability
in Korean industries.
Table 1: NHDD system parameters
Parameter PMR200 PBR200
Thermal power (MWth) 200 200
Equivalent active core inner/outer radius (cm) 50/140 80/147
Thickness of outer reflector (cm) 100 90
Effective core height (cm) 555 873
Average power density (W/cc) 6.69 4.79
Primary helium inlet/outlet temperature (°C) 490/950 490/950
Primary helium pressure (MPa) 7.0/6.95 7.0/6.87
Primary helium flow rate (kg/s) 82 83.2
RCCS inlet/outlet temperature (°C) 43/217 43/169
Peak fuel temperature (°C) 1 165 1 156
NHDD, which is proposed as a mid-term project, adopted a cooled vessel concept. The vessel
material will be SA508/533 steel in which there are many experiences on forging, welding, etc. Analyses
on the additional heat loss during normal operation and the peak temperature during accident confirm
that the cooled vessel concept is applicable (Kim, M-H., 2008) until full manufacturing capability is
developed for the high chromium steel vessel.
Two types of core, a prismatic block (PMR) and a pebble bed (PBR), are studied for NHDD reactor.
Each reactor type has pro and cons for hydrogen production. Currently, the more important issue is to
resolve the technical challenges in supplying the high temperature heat to chemical reactor efficiently
and safely. Since frequent maintenance such as catalyst replacement of a chemical plant is expected,
the hydrogen production plant of NHDD consists of five trains. A multi-train approach may enhance
plant availability as well as the possibility of testing various hydrogen production processes in an
industrial environment before selecting adequate commercial process.
A conceptual design of NHDD system is expected to be started in 2010 for three years.
Design tools
Many design tools were developed for the gas reactor analysis as well as for the hydrogen production
assessment. A neutron diffusion solver is practical to handle the large number of cases including the
sensitivity calculations for reactivity coefficient at several depletion steps. Computer tools for the reactor
physics analysis are developed to support PMR and PBR design. To handle the double heterogeneity of
coated particle, a special method named “reactivity equivalence physical transformation” (RPT) was
introduced (Kim, 2005). A Monte Carlo code MCNP is adopted as a standard code in the design
procedure in the RPT-based analysis methodology as shown in Figure 2. The idea of RPT was extended
to pebble geometry as well. The RPT method applied for PMR and PBR results reasonably accurate
prediction capability (Noh, 2008).
Many computer codes are required for design and safety analysis of a VHTR system as displayed
in Figure 2. HyPEP is a computer code to do scoping analysis of the VHTR, PCS and hydrogen plant
coupled system. HyPEP can be used to set operating parameters of the nuclear hydrogen production
system. The probabilistic safety analysis is done by PSA-AIMS. The detailed thermo-fluid analysis is
performed by the thermo-fluid code MARS-GCR combined with the reactor physics code MASTER-GCR.
A system analysis code GAMMA (No, 2007) is developed to handle air/moisture ingress situation.
GAMMA solves an integrated system of equations for the chemical reactions and the conventional
NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 61