CEC thermal-hydraulic benchmark exercise on Fiploc verification experiment F2 in Battelle model containment long-term heat-up phase

European Commission Directorate-General For The Information Society And Media Directorate-General For Research And Innovation

Description

Results for Phase I
Nuclear energy and safety

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• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-DI
• Nombre de lectures: 19
• Langue: English
• Poids de l'ouvrage: 2 Mo

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Commission of the European Communities
nuclear science
and technology
CEC thermal-hydraulic benchmark exercise
on Fiploc verification experiment F2
in Battelle model containment
long-term heat-up phase
Results for Phase I Commission of the European Communities
thermal-hydraulic benchmark exercise
on Fiploc verification experiment F2
in Battelle model containment
long-term heat-up phase
Results for Phase I
K. Fischer, M. Schall, L. Wolf
Battelle Institut E.V.
Am Romerhof 35
D-W-6000 Frankfurt/Main 90
Contract No ETSN-0045/D
Final report
Directorate-General
Science, Research and Development PA1 EUROP Biblioth.
1991 N.C. EUR 13588 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1991
ISBN 92-826-2777-2 Catalogue number: CD-NA-13588-EN-C
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1991
Printed in Belgium Contents Page
1 Introduction
1.1 Background 1.1 Background 1
1.2 1.2. Objectives of the Benchmark Exercise 2 2
1.3 Objective of the F2-Experiment 4
4 1.4 Test Facility and Experiment
Participating Codes and Institutions 13
2.1 Code Versions and Modifications
2.2 Contributed Calculations ^
Results of Model Calculations 19
3.1 Pressure and Leakage
3.2 Atmospheric Temperature 24
3.2.1 Specified Pressure Simulations
3.2.2d Mass Flow Injection Simulations 25
3.3 Sump Temperature and Level 26
3.4 Steam/Air Concentration8
3.5 Heat Transfer and Structure Temperatures 29
3.6 Flow Velocities 31
4 Computational Effort and Code Stability 69
5 Conclusions 73
5.1 Achievements of the Benchmark Exercise 7
5.2 General Modelling Aspects 7
5.3 Remarks on Participating Codes6
6 References9
Appendix by S. Schwarz, GRS München, FRG 81
III Summary
After completion of the CEC Benchmark Exercise on the thermal hydraulic aspects of the
single-compartment DEMONA-experiment B3, the majority of the participants recognized
the need for a follow-up exercise on the basis of typical multi-compartment experiment. The
experiment should cover such aspects as thermal stratification, natural and combined
convection, recirculation flow patterns, non-uniform spatial condensation effects and heat
transfer because it is the combination of these phenomena which must be properly modelled
in multi-compartment geometry when realistic containment behavior must be addressed.
CEC supported this idea from the beginning and an invited international working group
selected the F2-experiment in the Battelle Model-Containment from different other
candidates.
The major objective of the F2-experiment was to investigate the thermal-hydraulic long-
term phenomena with special emphasis on natural convection phenomena in a loop type
geometry affected by variations of steam and air injections at different locations as well
as dry energy supply into various compartments.
The open post-test exercise is being performed in two consecutive phases, with Phase 1
covering the initial long-term heat-up phase.
The specification report did not only provide the usual initial- and boundary conditions
but Battelle also proposed an 11-node model for the BMC including vent flow resistance
coefficients and compartment-dependent leakage rates to be used by all participants. This
model was agreed upon by all participants at a workshop. It is a compromise between
computational efforts, physically sufficient representation and limitation of complexity. The exercise received widespread international attention with 9 organisations from 6
European countries participating with 7 different computer codes (FUMO, JERICH02,
FIPLOC, WAVCO, CONTAIN, MELCOR, COBRA/FATHOMS). These codes cover a
broad spectrum of presently known European computational tools in severe accident
containment analysis.
The participants used either the specified mass flow or pressure control boundary conditions.
Some exercised their codes for both. In total, 14 different computations were officially
provided by the participants indicating strong interests and cooperative efforts by various
institutions.
Each institution received individual comparisons between measured data and computed
results. At a recent workshop superpositions of all computations in comparison with the
data were presented, discussed and distributed among the participants.
The following observations can be summarized from the results of Phase 1 of the CEC
Benchmark Exercise:
1) The provision of an unique containment model with all necessary input eliminated a
number of uncertainties commonly introduced by the individual participant's modeling
efforts
2) Because of the application of this model by nearly all participants, a more common
basis for assessing the individual computations was obtained
3) Specification of the leakage allowed the coarse lumped-parameter models to
approximate the penetration of steam into dead-end rooms
4) The issue of the BMC leakage was more of a problem for mass flow boundary driven
computations than for pressure controlled computations. Best estimate leakage
assumptions resulted in much better agreement with the data
VI 5) The application of the same code by different users resulted in some deviations
6) Considering the leakage involved during the F2-experiment and with due consideration
of the specified input data, the codes generally show consistent treatments of the
underlying conservation equations. Especially the observed thermal stratification has
been reproduced by all codes.
7) The observed discrepancies in the pressure histories for the mass flow controlled
computations can be understood in terms of the applied treatments of the leakages,
respectively.
8) It should be recognized that the observed spread in the calculations compared to the data
is indicative of:
a) the fact that this exercise was the first effort in multi-compartment analysis for a
majority of the participants
b) needs for further improvements of the physical models and numerics to cope with
long-term containment transients
9) The computational efforts by the individual codes for the 48 h problem time span nearly
two orders of magnitude
In summary, the CEC Benchmark Exercise for multi-compartment long-term containment
analysis has achieved its major objectives, mainly due to the enthusiastic efforts by all of the
international participants. The verification efforts involved for the F2-Benchmark Exercise
Phase I are limited to the thermal-hydraulic processes covered by the heatup phase of the
underlying experiment, namely plug flow, thermal stratification and heat conduction. The
Benchmark Exercise is now continued in Phase 2 covering all aspects of natural circulation
flow modeling.
VII -