NEA-0448 MATTEO.
MATTEO, BWR Subchannel Steady-State and Transient Thermohydraulics
NAME OR DESIGNATION OF PROGRAM, COMPUTER, NATURE OF PHYSICAL PROBLEM SOLVED, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, UNUSUAL FEATURES OF THE PROGRAM, AUXILIARIES, STATUS, REFERENCES, MACHINE REQUIREMENTS, LANGUAGE, OPERATING SYSTEM, OTHER RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHOR, MATERIAL, CATEGORIES
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| Program name | Package id | Status | Status date |
|---|---|---|---|
| MATTEO | NEA-0448/01 | Tested | 01-MAR-1975 |
Machines used:
| Package ID | Orig. computer | Test computer |
|---|---|---|
| NEA-0448/01 | IBM 370 series | IBM 370 series |
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3. NATURE OF PHYSICAL PROBLEM SOLVED
Enthalpy, flow and vapour concentration distributions in all the sections and subchannels of a nuclear BWR or of an experimental loop simulating thermohydraulic behaviour are calculated in steady state and transient assuming that heat fluxes to the coolant and total mass flow into the channel are known functions of time. The general pressure of the system is also a known function of time as well as the inlet enthalpy.
Enthalpy, flow and vapour concentration distributions in all the sections and subchannels of a nuclear BWR or of an experimental loop simulating thermohydraulic behaviour are calculated in steady state and transient assuming that heat fluxes to the coolant and total mass flow into the channel are known functions of time. The general pressure of the system is also a known function of time as well as the inlet enthalpy.
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4. METHOD OF SOLUTION
Open channel model - the diverted volume flows are calculated at each node by imposing equal pressure drops for each subchannel. The problem specification for intersubchannel volume exchange is obtained by imposing zero net recirculation in all independent recirculation closed paths among subchannels in the channel layout. The diverted cross flows are split up into vapour and liquid cross flows by specific models for transversal slip and vapour-liquid volume per volume exchange between pairs of connected subchannels. The numerical model is finite backwards differences in space and time. The diverted flows at each axial node are obtained by an iterative procedure with underrelaxation. The tangent method is utilized for diverted volume flows with renormalization to enforce the total volume continuity. The convergence is said to be achieved when the pressure has been achieved and the pressure drops agree within one tenth of percent with their weighted average. The calculation scheme sweeps the bundle from inlet to outlet iterating to convergence at each axial node in succession in steady state and at each time step.
Open channel model - the diverted volume flows are calculated at each node by imposing equal pressure drops for each subchannel. The problem specification for intersubchannel volume exchange is obtained by imposing zero net recirculation in all independent recirculation closed paths among subchannels in the channel layout. The diverted cross flows are split up into vapour and liquid cross flows by specific models for transversal slip and vapour-liquid volume per volume exchange between pairs of connected subchannels. The numerical model is finite backwards differences in space and time. The diverted flows at each axial node are obtained by an iterative procedure with underrelaxation. The tangent method is utilized for diverted volume flows with renormalization to enforce the total volume continuity. The convergence is said to be achieved when the pressure has been achieved and the pressure drops agree within one tenth of percent with their weighted average. The calculation scheme sweeps the bundle from inlet to outlet iterating to convergence at each axial node in succession in steady state and at each time step.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM
Relatively slow pressure transient as no sound wave propagation is considered and thermodynamic equilibrium is assumed in the saturated region.
Relatively low inlet enthalpy subcooling as liquid water properties are considered at the saturation point corresponding to the general pressure level. The pressure drop into the channel should be small relative to the general pressure level as the spatial variation of pressure is neglected in evaluating liquid and vapour properties.
All these limitations allow the calculation of every practical transient in BWR analysis with exclusion of blowdown. Transients with complete flow reversal are also excluded as no provision for coolant inlet from two directions is made. Local flow reversal in some subchannels is permitted in principle even if the correlations utilized are questionable in this event.
Relatively slow pressure transient as no sound wave propagation is considered and thermodynamic equilibrium is assumed in the saturated region.
Relatively low inlet enthalpy subcooling as liquid water properties are considered at the saturation point corresponding to the general pressure level. The pressure drop into the channel should be small relative to the general pressure level as the spatial variation of pressure is neglected in evaluating liquid and vapour properties.
All these limitations allow the calculation of every practical transient in BWR analysis with exclusion of blowdown. Transients with complete flow reversal are also excluded as no provision for coolant inlet from two directions is made. Local flow reversal in some subchannels is permitted in principle even if the correlations utilized are questionable in this event.
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NEA-0448/01, included references:
- G. Forti:The Computer Programme MATTEO for Subchannel Analysis of BWR Rod
Bundles in Steady State and Transient
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NEA-0448/01
| File name | File description | Records |
|---|---|---|
| NEA0448_01.001 | SOURCE PROGRAM (F4) | 1949 |
| NEA0448_01.002 | SAMPLE PROBLEM INPUT DATA | 41 |
| NEA0448_01.003 | SAMPLE PROBLEM PRINTED OUTPUT | 1184 |
Keywords: BWR reactors, coolants, enthalpy, flow rate, heat transfer, steady-state conditions, thermodynamics, transients, vapors.