Experimental study of the transient characteristics of a natural circulation loop under SBLOCA
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J. H. Bo
Abstract
In order to understand the influences of various factors on the depressurization rate under small break LOCA occurring at the upper plenum in a natural circulation loop, a basic analysis has been carried out. It is shown that the depressurization rate is influenced by system pressure, back pressure, break area, water mass in the system, heating power, operational state of the second loop, and so on. Experimental results of flow and heat transfer are also presented in this paper. The experiment was carried out at the 5 MW nuclear heating reactor test loop HRTL-5. The transient processes are described and heat transfer coefficients are estimated. The results show that flashing improves the natural circulation and the heat transfer, so the wall temperature of the heated rod can be kept at a lower level and the reactor is safe. The flow oscillation, which leads to cyclical variations of important parameters, is described and its development mechanisms are studied. It is pointed out that the interaction of pressure decreasing and bubbles producing caused by flashing is the main reason of the flow oscillation.
Abstract
Es wurde eine grundlegende Analyse zum Verständnis der Auswirkungen verschiedener Einflussfaktoren auf die Druckabbaurate bei einem Kühlmittelverluststärfall mit kleinem Leck im Bereich des oberen Plenums in einer Testschleife mit Naturumlauf durchgefährt. Es wird dargelegt, dass die Druckabbaurate vom Systemdruck, vom Außendruck, von der Leckgröße, vom Wasserinventar, von der Heizleistung und vom Betriebszustand des Sekundärkreislaufs abhängt. Im vorliegenden Beitrag werden experimentelle Ergebnisse zum Massenfluss und zur Wärmeübetragung dargestellt. Das Experiment wurde an der Testschleife HRTL-5 des 5 MW nuklearen Heizreaktors durchgefährt. Die transienten Prozesse werden beschrieben; für die Wärmeübergangskoeffizienten werden Schätzwerte ermittelt. Die Ergebnisse zeigen, dass „Flashing“ den Naturumlauf und den Wärmeübergang steigert, so dass die Wandtemperatur des Heizstabes niedriger gehalten werden kann, der Reaktor bleibt in einem sicheren Zustand. Die Oszillation des Massenflusses, die zyklische Veränderungen wichtiger Parameter zur Folge hat, wird beschrieben und der Mechanismus ihres Zustandekommens wird untersucht. Es wird dargelegt, dass der Hauptgrund für die Oszillation des Massenflusses in einer durch das „Flashing“ verursachten Wechselwirkung von Druckabbau und Blasenbildung zu sehen ist.
List of symbols
- A
break area
- cp
specific heat capacity at constant pressure
- d
orifice diameter
- G
discharge steam mass flow rate at the break
- H
heat transfer coefficient
- I'
specific enthalpy of saturated water
- k'
adiabatic exponent of steam
- m
total mass of water and steam in the system
- m
the evaporated mass
- m
circulation mass flow rate
- m'
mass of water in the system
- m"
mass of gas in the system
- p
pressure in the gas space
- pe
back pressure
- Phi
pressure at the heated section inlet
- Q
heat flux
- t
time
- Thi
inlet temperature of the heated section
- Tho
outlet temperature of the heated section
- Tro
outlet temperature of the riser
- T„
temperature at the upper space of the separator
- Tw
wall temperature of the heated rod
- Ts
saturation temperature
- Tshi
saturated temperatures corresponding to the heated section inlet pressure
- ΔT
temperature difference
- V
total volume of the primary loop
- Vh
hot section volume
- V'
water volume
- V"
gas space volume
- Wc
condensed water mass
- x
steam quality
- α
average avoid fraction in the hot section
-
void fractions at the heated section inlet
- α2
void fractions at the raiser inlet
- Φ
heating power in the system
- r
latent heat
- v'
specific volume of saturated water
- v"
specific volume of saturated steam
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© 2001 Carl Hanser Verlag, München
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Articles in the same Issue
- Frontmatter
- Calendar of Events
- Calendar of Events • Veranstaltungskalender
- Summaries
- Summaries/Kurzfassungen
- Notes
- Richtlinie VDI 3783 Blatt 12. Umweltmeteorologie – Physikalische Modellierung von Strömungs- und Ausbreitungsvorgängen in der atmosphärischen Grenzschicht – Windkanalanwendungen; Hrsg.: VDI Verein Deutscher Ingenieure, Kommission Reinhaltung der Luft (KRdl im VDI und DIN-Normenausschuss), Dezember 2000; 107,60 DM
- Comparison of plant efficiencies of various power conversion systems for high-temperature reactor modules
- Studies on the behaviour of a passive containment cooling system for the Indian Advanced Heavy Water Reactor
- Detonation waves in melt-coolant interaction
- Experimental study of the transient characteristics of a natural circulation loop under SBLOCA
- Calculation of the higher order eigenvalues for a homogeneous sphere using the FN method
- Books
- Safe Management of the Operating Lifetimes of Nuclear Power Plants
- Study of the possibility of high accuracy flow measurements with the pulsed neutron activation method
- The astrophysical S-factor for dd-reactions at keV-energy range
- Books
- Books • Bücher
- Monte Carlo analysis of accelerator-driven systems: Studies on spallation neutron yield and energy gain
- Subcritical nuclear systems and their stability against changes in the geometrical set-up
- Technical Notes
- An energy amplifier fluidized bed nuclear reactor concept
- An attempt to describe the swelling of U3Si 2 fuel by a simple formula
- European Commission initiative to promote technical harmonisation on risk-based decision making
- Patent
- Notes
- Note • Mitteilung
