Post-Test Calculations of NOKO Emergency Condenser Experiments


Post-Test Calculations of NOKO Emergency Condenser Experiments

Schaffrath, A.; Dumaz, P.

The SWR1000 is a new innovative boiling water reactor concept,
which is developed by Siemens AG. This concept is characterized
in particular by passive safety systems (e.g., four emergency
condensers, four building condensers, eight passive pressure
pulse transmitters, six gravitydriven core flooding lines).
Passive safety systems need no external energy sources. The
function is directly based on the physical phenomena:
gravity, natural convection and/or evaporation. Therefore the
effectiveness is independent of operator actions and smaller
failure rates are assigned to passive safety systems.
For the experimental investigation of the operation mode and
the effectiveness of these passive safety systems the multipurpose
thermohydraulic test facility NOKO (NOKO is an abbreviation for
the German translation of emergency condenser) was constructed
at the Forschungszentrum Jülich (FZJ). The facility has a maximum
power of 4 MW for steam production and a maximum operating pressure
of 10 MPa.

In the frame of an European Union programme (EU BWR R&D Cluster),
six test series with an emergency condenser test bundle were
performed in 1996. Within the Physics and Thermalhydraulics
Complementary Actions (BWR/CA) to the EU BWR R&D Cluster the
German Forschungszentrum Rossendorf (FZR) e.V. and the French
Commisariat a'l Energie Atomique (CEA/DRN) have calculated 9 tests
and an additional blind test of the NOKO bundle experiments. These
posttest calculations were carried out using ATHLET (FZR) and
CATHARE2 (CEA/DRN). The results of these calculations are presented
in this paper.

Detailed comparisons of ATHLET and CATHARE results show that despite
the good prediction of global parameters for both codes, the variations
of local parameters calculated (e.g., film velocity and temperature)
are not in such a good agreement. This can be explained by some
compensating errors in computer codes (e.g., an overestimation of
the condensing film velocity can hide an error in the condensation
correlation) and the significant effect of the tube wall conduction
in controlling the heat transfer. The emergency condenser test bundle
of the available and considered experiments were not instrumented.
Therefore a deeper analysis (including a detailed comparison of local
parameters) is not possible. New test series released in the frame of
a new European union action will be analyzed in 1998.

  • Lecture (Conference)
    ICONE 6 - 6th International Conference on Nuclear Engineering , 10.-14. Juni 1998, San Diego, Californien, Beitrag 6382
  • Contribution to proceedings
    ICONE 6 - 6th International Conference on Nuclear Engineering , 10.-14. Juni 1998, San Diego, Californien, Beitrag 6382

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Publ.-Id: 1135