R&D Category: Thermo hydraulics in all operating, shut-down and accident regimes
5 documents found
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Thermal-hydraulic and hydrodynamic investigations for the nuclear boiling generator in KNK II Thermohydraulische und hydrodynamische Untersuchungen fuer den nuklearen Siedegenerator KNK II
Dorr, B.;Schleisiek, KKernforschungszentrum Karlsruhe GmbH (Germany)
KFK-IRE--5/01.24.3/75/77 - German - 1977
Abstract: In order to test boiling detection methods for sodium cooled fast reactors, the installation of a nuclear heated boiling generator is planned in KNK II. In this report thermal-hydraulic investigations are reported, which have been performed in the IRE for the design of this blocked fuel assembly. The following problems are treated: 1. Size of the blockage and temperature distribution within this area. 2. Conditions, under which local boiling has to be expected, 3. Hydrodynamic processes during local boiling (bubble volume, life duration of bubbles, coolant flow variations)
Key words: boiling detection;bubble growth;flow blockage;in core instruments;knk-2 reactor;reactor cooling systems;temperature distribution;thermal hydraulics;transfer functions
Components Category: any or undefined
display the document: 34087746.pdf
Simulation of fuel element thermal hydraulics for sensitive monitoring of coolant flow
Edelmann, M. (Kernforschungszentrum Karlsruhe G.m.b.H. (Germany, F.R.). Inst. fuer Neutronenphysik und Reaktortechnik)GRS--19 - English - 1980
Abstract: The sensitivity of outlet temperatures for cooling disturbances can be improved significantly by eleminating temperature noise and variations of the temperature rise of a subassembly due to inlet temperature and power noise or control of the reactor power level. This has been demonstrated at the KNK II. The different types of KNK fuel elements were modeled by individual combinations of two first-order low-pass filters, one for the fuel element and one for the thermocouple. Using a neutron detector signal as input for these filters provides simulated outlet temperature signals for comparison with the measured signals. Under stationary conditions of reactor operation these signals agreed within less than 1 K. For non-stationary conditions a more general model of the fuel element was applied. In this model time-dependent thermohydraulic parameters could be used. In this way a cooling disturbance consisting of gas bubbles in the sodium was simulated. A sensitivity study showed that gas bubbles of 1% of the sodium volume in the fuel region could be detected at KNK II in spite of the power drop caused simultaneously by the negative sodium void effect. (orig./HP)
Key words: disturbances;flow blockage;flow rate;knk-2 reactor;loss of flow;reactor control systems;reactor noise;temperature control
Components Category: --Fuel assemblies
display the document: 13665581.pdf
Influence of the KNK II postscram control on the thermohydraulic plant behavior
Schubert, B. (GKSS-Forschungszentrum Geesthact GmbH, West Germany)CONF-850410--Vol.2 - English - 1985
Abstract: In LMFBRs the balance of generated and removed heat is highly distorted during the period following shortly after scram, because the core flow drops much less than the reactor power does even though the pumps are tripped as fast as possible after scram signal occurs. Due to this sharp temperature gradients are produced in the core and enter the piping system of the plant despite the damping effect of the upper plenum. In order to reduce the temperature variations occurring shortly after scram a flow control system is used in the German loop-type LMFBR. Theoretical investigations are presented to demonstrate how postscram control systems work and can help to limit thermal shocks in the plant. In addition several parameters of the system are investigated to show their influence
Key words: flow rate;fluid flow;heat transfer;knk-2 reactor;pipes;reactor control systems;reactor cooling systems;reactor cores;reactor protection systems;reactor safety;scram;thermal shock
Components Category: Reactor components
display the document: 17036590.pdf
Experiments on thermohydraulically induced fuel rod oscillations in a sodium flow. THIBO-Experiments Experimente zu thermohydraulisch induzierten Brennstab-Oszillationen im Natrium Strom. THIBO-Experimente
Bojarsky, E;Deckers, H.;Lehning, H.;Piel, D.;Reiser, H.;Schmidt, LKernforschungszentrum Karlsruhe GmbH (Germany)
KFK-PSB--01.11.12P06B - German - 1989
Abstract: The fuel rod claddings of the sodium cooled fast reactor KNK II showed damage in the form of wear marks and cracks. There is some evidence indicating that this damage is caused not by hydraulically induced vibrations but by low-frequency rod bowing due to the joint impacts of sodium heating and sodium flow. In order to investigate this supposed behavior of fuel pins, the THIBO (standing for thermohydraulically induced fuel pin oscillations) experiments have been performed in the sodium loop of the IMF III institute since November 1987 with an electrically heated test pin in an annular channel. These experiments have so far been successful inasmuch as it has been possible to generate under given conditions the anticipated variations in coolant channel temperatures and the periodical movements of the test pin corresponding to them, and to influence them by variation of operating parameters. Following a short description of the test facility, the test program as well as the essential test results are contained in the report
Key words: bowing;coolant loops;fuel pins;fuel rods;knk-2 reactor;mechanical vibrations;performance testing;sodium;thermal hydraulics
Components Category: --Fuel pins
display the document: 34086305.pdf
Summary representation of the behaviour of the fuel subassembly outlet temperatures in KNK II/2 Zusammenfassende Darstellung zum Verhalten der Brennelementaustrittstemperaturen der KNK II/2
Heinecke, J.;Hess, BSiemens AG, Bereich Energieerzeugung, KWU (Germany)
KWU-BGL-BT--71-92-0055 - German - 1992
Abstract: During the operation of the second core of the fast test reactor KNK II the measured fuel subassembly outlet temperatures showed time dependences which did not agree with the calculated changes due to fuel burnup, reloading of fuel subassemblies and control rod movement. The differences between the measured and pre-calculated changes are illustrated in the present report, and theoretical and experimental investigations for their clarification are described. As a summary it can be stated, that metallic particles in the primary sodium are the origin for the discrepancies. They deposit in the upper part of the fuel pins and the pin spacers, thus causing an increase of the hydraulic resistance of the fuel subassemblies. The calculated temperature changes using theoretical models of the depositing process agreed with the measurements
Key words: burnup;deposits;friction;fuel assemblies;knk-2 reactor;reactor operation;temperature distribution;temperature measurement;thermal hydraulics
Components Category: --Fuel assemblies
display the document: 34086310.pdf