TRAB-3D is the newest member in the reactor dynamics code
family developed in VTT. It is now possible to analyze
both PWRs and BWRs taking into account the real core
loading. The core geometry can be either rectangular, as
in most western reactors, or hexagonal, as in e.g. VVER
reactors. In addition to the core models the codes
include models for the cooling circuits and reactor
control systems. This paper describes the
neutronics/thermal-hydraulics coupling methodology and
validation of the three-dimensional TRAB-3D for the
application to PWR and BWR transient calculations.
Code development in the fields of reactor physics and
dynamics, as well as in thermal-hydraulics has been one
of the key areas of reactor safety research in Finland
since the middle of the seventies. In reactor dynamics,
which combines neutron kinetics, heat conduction, heat
transfer and hydraulics of the cooling circuit, the first
product was a LWR core model (Rajamäki 1980a), which is
basically one-dimensional two-group code, but includes a
synthesis model for radially nonuniform dynamics.
The same core model was applied in the development of the
BWR dynamics code TRAB (Rajamäki 1980b and Räty et al.
1991), which is continuously used in the safety analysis
of the Finnish TVO power plant. It models the core and
the main circulation system inside the reactor vessel,
including the steam dome with related systems, steam
lines, recirculati-on pumps, incoming and outgoing flows,
as well as control and protection systems. Typical
applications are the pump trip and the steam line
isolation. The code has also been used for the simulation
of the RBMK type reactor in accident conditions.
The HEXTRAN (Kyrki-Rajamäki 1995) core dynamics model has
been developed on the basis of the stationary two-group
diffusion code HEXBU-3D (Kaloinen et al. 1981) for
hexagonal geometries, with the fuel heat conduction and
channel hydraulics description of the TRAB code.
TRAB-3D (Kaloinen & Kyrki-Rajamäki 1997) is a similar
code used for rectangular lattice reactors. In addition
to the core dynamics TRAB-3D also includes the BWR
circuit models of TRAB. The validation work of TRAB-3D
consists of the successful calculation of OECD
benchmarks, the most recent of which has been the PWR
main steam line break (MSLB) benchmark (Ivanov et al.
1999), as well as comparisons with measurements of real
TVO plant transients (Daavittila et al. 2000).
As the cooling circuit model of PWRs serves the SMABRE
code (Miettinen 1985) coupled with HEXTRAN or TRAB-3D.
SMABRE is a fast running simulation code and it was
developed for such thermal-hydraulic accidents as small
breaks, originally in order to facilitate parameter
variations to support slow RELAP calculations. Its range
of application was, however, soon extended to cover such
types of accidents as small break LOCA, primary-secondary
leak, steam line break, ATWS and most parts of a large
break LOCA in VVER plants.
|Title of host publication||FINNUS: The Finnish Research Programme on Nuclear Power Plant Safety|
|Subtitle of host publication||Interim Report 1999 - August 2000|
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Publication status||Published - 2000|
|MoE publication type||D2 Article in professional manuals or guides or professional information systems or text book material|
|Series||VTT Tiedotteita - Research Notes|