Abstract
A three-dimensional reactor dynamics computer code has
been developed, validated and applied for transient and
accident analyses of VVER type nuclear reactors. This
code, HEXTRAN, is a part of the reactor physics and
dynamics calculation system of the Technical Research
Centre of Finland, VTT.
HEXTRAN models accurately the VVER core with hexagonal
fuel assemblies. The code uses advanced mathematical
methods in spatial and time discretization of neutronics,
heat transfer and the two-phase flow equations of
hydraulics. It includes all the experience of VTT from 20
years on the accurate three-dimensional static reactor
physics as well as on the one-dimensional reactor
dynamics. The dynamic coupling with the thermal hydraulic
system code SMABRE also allows the VVER circuit-modelling
experience to be included in the analyses.
With HEXTRAN it is possible to make realistic
time-dependent analyses starting from the actual core
cycle conditions. Methods for making conservative
accident analyses with this best-estimate code have also
been developed. The usefulness of the
three-dimensionality is shown particularly in accidents
with asymmetric fission power distribution originating
from local neutronic or thermal hydraulic disturbances in
the core or cooling circuits. Complicated accidents in
which there are strong interactions between neutron
kinetics and thermal hydraulics can be reliably analyzed.
The new hydraulics solution method PLIM developed at VTT
has been applied in HEXTRAN to remove modelling
restrictions and to eliminate numerical diffusion and
dispersion. The use of PLIM improves accuracy and expands
the applicability range of the code.
HEXTRAN has been validated against different types of
relevant information available, viz. measurements of a
test reactor, start-up experiment and other data of a
real plant, as well as with calculations of several
international benchmark problems and independent code
comparisons. HEXTRAN's applicability to calculate
VVER-440 and VVER-1000 type reactors has been
demonstrated.
Extensive analyses have been carried out with HEXTRAN on
both design basis and new types of accidents, e.g. RIA,
ATWS or local boron dilutions, for the Finnish Loviisa
and Hungarian Paks nuclear power plants
as well as for the new Russian VVER-91 concept.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 17 Nov 1995 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-4784-5 |
Publication status | Published - 1995 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- nuclear reactors
- reactor dynamics
- three-dimensional kinetics
- HEXTRAN
- mathematical models
- computer programs
- validation
- accident analysis
- WWER type reactors
- hexagonal fuel