Three-dimensional reactor dynamics code for VVER type nuclear reactors

Dissertation

Riitta Kyrki-Rajamäki

Research output: ThesisDissertationCollection of Articles

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 languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Helsinki University of Technology
Supervisors/Advisors
  • Salomaa, Rainer, Supervisor, External person
Award date17 Nov 1995
Place of PublicationEspoo
Publisher
Print ISBNs951-38-4784-5
Publication statusPublished - 1995
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

Nuclear reactors
Accidents
Hydraulics
Physics
Networks (circuits)
Two phase flow
Nuclear power plants
Dilution
Boron
Neutrons
Heat transfer
Cooling
Kinetics
Hot Temperature
Experiments

Keywords

  • nuclear reactors
  • reactor dynamics
  • three-dimensional kinetics
  • HEXTRAN
  • mathematical models
  • computer programs
  • validation
  • accident analysis
  • WWER type reactors
  • hexagonal fuel

Cite this

Kyrki-Rajamäki, R. (1995). Three-dimensional reactor dynamics code for VVER type nuclear reactors: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Kyrki-Rajamäki, Riitta. / Three-dimensional reactor dynamics code for VVER type nuclear reactors : Dissertation. Espoo : VTT Technical Research Centre of Finland, 1995. 142 p.
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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.",
keywords = "nuclear reactors, reactor dynamics, three-dimensional kinetics, HEXTRAN, mathematical models, computer programs, validation, accident analysis, WWER type reactors, hexagonal fuel",
author = "Riitta Kyrki-Rajam{\"a}ki",
year = "1995",
language = "English",
isbn = "951-38-4784-5",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
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Kyrki-Rajamäki, R 1995, 'Three-dimensional reactor dynamics code for VVER type nuclear reactors: Dissertation', Doctor Degree, Helsinki University of Technology, Espoo.

Three-dimensional reactor dynamics code for VVER type nuclear reactors : Dissertation. / Kyrki-Rajamäki, Riitta.

Espoo : VTT Technical Research Centre of Finland, 1995. 142 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Three-dimensional reactor dynamics code for VVER type nuclear reactors

T2 - Dissertation

AU - Kyrki-Rajamäki, Riitta

PY - 1995

Y1 - 1995

N2 - 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.

AB - 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.

KW - nuclear reactors

KW - reactor dynamics

KW - three-dimensional kinetics

KW - HEXTRAN

KW - mathematical models

KW - computer programs

KW - validation

KW - accident analysis

KW - WWER type reactors

KW - hexagonal fuel

M3 - Dissertation

SN - 951-38-4784-5

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Kyrki-Rajamäki R. Three-dimensional reactor dynamics code for VVER type nuclear reactors: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1995. 142 p.