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Thermal-hydraulics
Pressurized thermal shocks, Subchannel flow, Steam jets in containments, Hydrogen distribution and boron dilution in RPV’s, Convection in steam generators, Innovative Gen-IV reactors
Nuclear Technology
ASCOMP provides consulting services in the thermal hydraulics of nuclear power plants. We offer detailed
thermal-hydraulics studies including principally multiphase flow and heat transfer in reactor core and
containment systems, or during postulated transients in Light Water Reactors (LWR). TransAT offers the
opportunity to simulate medium to small-scale, multiphase flows featuring phase change either using
phase-average models or more detailed interface tracking variants. Medium-scale two-phase flow behavior
is conducted in specific components of a system.
Steam injection in containment pool
A typical example in BWR containments is the venting of vapor and gas mixtures into pressure suppression pools to control
containment pressure. The interest is evaluating the direct link between the vent and the pool surface. Full-scale experiments
remain too expensive to consider, motivating the development of advanced CMFD techniques for this purpose. Predicting the
break-up of the bubbles is important, since smaller ones condense very rapidly. TransAT is an excellent tool for predicting this
phenomenon, including steam condensation and chogging.
Sub-channel flow analysis
Predicting subcooled flow boiling in PWR’s is crucial for defining efficient operations and safety margins. In U.S. PWR plants,
subcooled flow boiling occurs under normal operating conditions, and determines the margin to critical heat flux. Subcooled flow
boiling also determines the rate at which corrosion products deposit on the surface of the cladding, which can lead to localized
corrosion and neutronic distortions, and ultimately cladding failure. TransAT simulations of the flow along subchannels use
systematically the IST/BMR meshing technique. Conjugate heat transfer between the rods and the fluid is thus simple to tackle.
Innovative Gen-IV HLM reactors
Thermal hydraulic studies involving free surfaces with Heavy Liquid Metals (HLM) have become important for innovative Gen-IV
nuclear reactors. In some of the reactors, the HLM can be used as coolant, while in Accelerator Driven Systems (ADS) it can be
used both as coolant and target. TransAT is used to solve several thermal-hydraulic issues encountered in ADS systems,
e.g. MYRRHA design in Belgium, more specifically in the free-surface multiphase and convective thermal-flow modelling contexts.
Flow and heat transfer in 5x5 fuel bundle
Boron dilution in the ROCOM model vessel
Interface deformations in the MYRRHA spallation source reactor
Pressurized Thermal Shock (PTS)
PTS events strongly affect the RPV integrity and as such they constitute a pillar in nuclear safety engineering. In PTS cold water
mixes with the hot fluid in the cold leg and flows towards the downcomer, poor mixing may lead to extreme thermal gradients in the
structures. ASCOMP engineers excel in predicting PTS using a combination of advanced turbulence models and multiphase flow
heat transfer models, in particular accounting for steam condensation.
Hydrogen distribution in the containment
In the case of a severe nuclear accident, Hydrogen produced by the metal-water reaction and core-concrete interaction is released
in the containment. Depending on the transient and geometrical configuration, a flammable mixture can be produced,
which can deflagrate and even lead to detonation, endangering the integrity of the containment. Trends in the area plead in favour
of advanced 3D for the prediction of various phenomena, e.g. the accumulation of light gases in specific parts of the containment.
Boron dilution in RPV
Boric acid is used as a neutron absorber for reactivity control in PWR’s. If the boric acid
concentration in the core region is reduced (boron dilution), a power excursion with possible fuel damage might occur. TransAT
enables the testing of a wide range of flow conditions in PWR’s pressure vessels, including boron injection: ranging from natural
convection flow-up to forced convection flow at nominal flow rates, including flow ramps due to pump start-up.
Mixed convection in steam generators
Steam Generators (SG) containing up to thousands U-shaped tubes are used to remove heat from the primary circuit to the
secondary one in PWRs. Mixing in SG inlet plenum is crucial during severe accidents where thermal stresses in U-tubes can be
significant. In response to the nuclear regulatory bodies recommending resorting to 3D CFD, we have adapted TransAT to deal
with key thermal-hydraulic issues that might be expected in severe accidents, including transients in the hot leg and SG inlet
plenum mixing.
EXCELLENCE IN MULTIPHASE FLOW SIMULATION
Multiphase Flow
Advanced Turbulence
Smart Meshing
Complex Fluids Flows
ASCOMP
www.ascomp.ch
France, Belgium - Eurobios
[email protected] - www.eurobios.com/
Middle East - Halhoul
[email protected]
China - SimPop Information Technology Co.
[email protected] - www.simpop.cn
South Korea - U . I . T . Inc.
[email protected] - www.uitsolutions.com
USA & Canada - Ascomp USA Inc.
[email protected] - www.ascomp.ch
Hong Kong - SimPop Technology
[email protected] - www.simpop.cn
North Africa - Enviroprocess
[email protected] - www.enviroprocess.com
Italy - Dofware
[email protected] - http://www.dofware.com/
India - RahulCom
[email protected] - rahulcom.com
United Kingdom - Petronet Resources
[email protected] - www.petronet-resources.co.uk/
Regional Distributors