Hydraulic phenomena

The hydraulic phenomena of concern for LPS conditions include cavitation and depriming 

Cavitation phenomena can affect the pumps and the control valves. 

In a liquid, pockets of steam may appear due to a temperature increase, a pressure decrease, or a combination of these two phenomena. The steam pockets are carried along by the liquid and condense when they reach zones where the pressure is higher. This condensation induces  

The signs of abnormal operation caused by cavitation are local knocking and a slight instability in pump parameters (current, pressure, flow), which can be detected from the control room. No local noise is generated apart from the noise of the pump motor forcing. 

The remedies are to change the operating parameters of the circuit (flowrate, pressure, 

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System thermal-hydraulic phenomena associated with instrument tube breaks at the reactor vessel and seal table are comparable. 

Yadigaroglu, G., and M. Andreani, 1989, Two Fluid Modeling of Thermal-Hydraulic Phenomena for Best Estimate LWR Safety Analysis, Proc. 4th Int. Topical Meeting on Nuclear Reactors Thermal-Hydraulics, Karlsruhe, U. Mueller, K. Rehnee, and K. Rust, Eds., Rep. NURETH-4, pp. 980-996. (3)... 

Uniform flow was described earlier as it applies to hydraulic phenomena in general. In the case of open channels, uniform flow means that the water cross section and depth remain constant over a certain reach of the channel. This requires that the drop in potential energy owing to the fall in elevation along the channel be exactly consumed by the energy dissipation through boundary friction and turbulence. 

Burt, T.N. Stevenson, J.R. (1986) Monitoring cohesive sediment transport in estuaries. In International Conference on Measuring Techniques of Hydraulic Phenomena in Offshore, Coastal and Inland Waters, London, England 9-11 April 1986. 

Often, the preliminary characterization wells can be incorporated in the permanent monitor-well network. However, in cases where the initial presumed ground-water flow direction turns out to be incorrect, due to the influences of nearby pumping wells, tidal fluctuations, ground-water mounds, or other hydraulic phenomena, additional regulatory wells may be required. 

From the results of up-scaling examination, the concept to treat the scale effect of permeability is considered. Then, by using the concept, the large scale analysis is carried out by considering the coupled thermal and hydraulic phenomena. At that time, some parametric studies are also carried out. 

Compacted swelling clays are often envisaged as the main component of engineered barriers for radioactive waste disposal. These barriers are subjected to thermal loading due to the heat emitted by the waste and to hydration from water coming from the adjacent rock. As a consequence of these thermo-hydraulic phenomena, mechanical and chemical changes arise that, in turn, may affect all other aspects of behaviour. A correct understanding and prediction of these barriers would require, therefore, the performance of fully coupled thermohydro-mechanical and chemical (THMC) numerical analyses. 

The main purpose of the Swiss mixing-layer research programme is to investigate the thermal-hydraulic phenomena in horizontal shear layers with particular attention paid to the effects of Richardson (Ri) and Prandtl (Pr) number. Therefore, experiments are to be performed over a wide range of velocity and temperature differences between the two streams and with water and sodium. In connection with safety considerations for pool-type LMFBRs, a reliable experimental data base should allow one to validate codes used to calculate the flow fields in the pools. 

TRACE (TRAC/RELAP Advanced Computational Engine) is recent thermal-hydraulics code designed to consolidate and extend the capabilities of safety codes— TRAC-P, TRAC-B, and RELAP. It is intended for analysis of large- and small-break LOCAs and system transients in both PWRs and BWRs. The code has the capability to model thermal-hydraulic phenomena in both ID and 3D spaces. 

RAMONA was developed at Brookhaven National Laboratory for analyzing BWR system transients. Until recently, RAMONA was the only best-estimate BWR system transient code capable of predicting 3D power in the core coupled with the fuel and cladding temperature and vessel thermal-hydraulic phenomena. 

CONTAIN (Containment transient analysis tool for PWRs or BWRs) has the capability to model thermal-hydraulics phenomena for existing containment designs. 

Knowledge of primary circuit thermal-hydraulic phenomena is necessary for the determination of structural loads. The methodology used to establish thermal stresses is generally based on close links between research on phenomena and an experimental approach using scaled models. Transposition to the reactor is made using similarity rules directly from experimental results, or using calculation codes, after validation on models or in-pile experiments. 

Grand, D., et. al. Three-dimensional Computation of Thermal-hydraulic Phenomena in Reactor Vessels, Proceedings of the International Topical Meeting Advances in Mathematics, Computations, and Reactor Physics - Pittsburgh, USA, 1991. 

Two-phase critical flow tests with non-condensable gases to investigate the thermal-hydraulic phenomena of critical flow with the existence of non-condensable gases,... 

This chapter describes the various hydraulic phenomena that occur in a bed of random dumped tower packing shapes. First, those factors that influence only gas-phase flow are considered. Then, the more complex hydraulics that result when liquid is introduced onto the packed bed are examined. Finally, a method for predicting pressure drop in two-phase flow through the packed bed is developed. 

The source of the energy in the primary NCL is the fuel rods in the reactor core, the coupling mechanism between the two loops is the SG, and a second HEX is used in the secondary loop to deposit the energy into the heat sink. All of this equipment, and the associated single- and two-phase thermal-hydraulic phenomena and processes, must be accounted for in the mathematical models developed for the system. 

Ambrosini, W., 2008. Lesson learned from the adoption of numerical techniques in the analysis of nuclear reactor thermal-hydraulic phenomena. Progress in Nuclear Energy 50, 866-876. 

In our assessment [10], MELCOR correctly calculated the thermal/hydraulic phenomena observed during steady-state, single-phase liqiud natural circulation, as summarized in Table 3.1. MELCOR predicted the correct total flow rate and the flow split between two unequal loops without any ad hoc adjustment of the input. The code could reproduce the major ther-mal/hydraulic response characteristics in two-phase natural circulation, after a number of nonstandard input modelling modifications MELCOR could not reproduce the requisite physical phenomena with normal input models. The natural circulation mass flows predicted in these two cases are shown in Figure 3.1. 

Since transport of heat and mass in the voids of a packed bed cannot be understood without knowing the movement of the fluid, hydraulic phenomena will be treated first. Second the heat and mass treuisfer between the fluid and the particles will be discussed. Third the radial transport of heat and mass through the voids (and the particles) will be treated. 

Some undesired thermal hydraulic phenomena were found and identified in these studies. For example, the flow vortex in the containment air duct, and water hammer of ERHR test may have bad impacts on its safety functions and should be avoided in the... 

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