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TRANSIENT EVALUATION OF A GEN-IV LFR DEMONSTRATION PLANT THROUGH A LUMPED-PARAMETER

LEADER PROGRESS MEETING, W.P. 4 TASK 4.4 Preliminary definition of the Control Architecture . TRANSIENT EVALUATION OF A GEN-IV LFR DEMONSTRATION PLANT THROUGH A LUMPED-PARAMETER ANALYSIS OF COUPLED KINETICS AND THERMALHYDRAULICS. Sara Bortot , Antonio Cammi.

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TRANSIENT EVALUATION OF A GEN-IV LFR DEMONSTRATION PLANT THROUGH A LUMPED-PARAMETER

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  1. LEADER PROGRESS MEETING, W.P. 4 TASK 4.4 Preliminary definition of the Control Architecture TRANSIENT EVALUATION OF A GEN-IV LFR DEMONSTRATION PLANT THROUGH A LUMPED-PARAMETER ANALYSIS OF COUPLED KINETICS AND THERMALHYDRAULICS Sara Bortot, Antonio Cammi CIRTEN - POLITECNICO DIMILANO November 18th, 2010, Bologna

  2. OUTLINE • Context and goals • Reactor configuration • Analysis approach • Mathematical model • Simulation results • Conclusions • WORK PROPOSAL – TASK 4.4

  3. CONTEXT and GOALS • Lead-cooled Fast Reactor (LFR) selected by the Generation IV international Forum (GIF) as one of the candidates for the next generation of nuclear power plants • significant technological innovations • need of a demonstrator reactor (DEMO) • study of plant global performances • refining/finalizing the system configuration REACTOR DYNAMICS • design of an appropriate control system

  4. REACTOR CONFIGURATION CORE LAYOUT

  5. ANALYSIS APPROACH (1) Thermal-hydraulics δTin(t) δTf(t) δTc(t) δTl(t) δq(t) δTout(t) δTf(t) δTc(t) δTl(t) δρ(t) δH(t) Reactivity Input δTin(t) δH(t) Tout H Ψ Ci CORE Tf Tc Tl Tin Kinetics δρ(t) δψ(t)

  6. ANALYSIS APPROACH (2) • MAIN ASSUMPTIONS -NEUTRONICS • neutron time fluctuations independent of spatial variations • spectrum independent of neutron level • - core lumped source of neutrons with prompt heat power • - neutron population and neutron flux related by constants of proportionality • POINT-KINETICS APPROXIMATION

  7. ANALYSIS APPROACH (3) • MAIN ASSUMPTIONS –THERMAL-HYDRAULICS • average channel representation • single-node heat-exchange model • - 3 distinct temperature regions fuel • cladding • coolant • - energy balance over the fuel pin surrounded by coolant • - reactor power input retrieved from reactor kinetics • LUMPED-PARAMETER APPROACH

  8. MATHEMATICAL MODEL (1) NEUTRON KINETICS EQUATIONS - ASSUMPTION t ≤ 0 steady state -perturbation around steady state solution -linearization SMALL-PERTURBATION APPROACH with: - ψ = n(t)/n0 = q(t)/q0 - ηi = Ci(t)/Ci0

  9. MATHEMATICAL MODEL (2) THERMAL-HYDRAULICS EQUATIONS ASSUMPTIONS: -constant properties -axial conduction neglected -Tl = (Tin + Tout)/2 SMALL-PERTURBATION APPROACH Time constants: - tf = MfCf/kfc - tc1 = McCc/kfc - tc2 = McCc/hcl -tl = Ml/Γ

  10. MATHEMATICAL MODEL (3) REACTIVITY EQUATIONS - αD = Doppler coefficient -αL = coolant density coefficient - αZ = axial expansion coefficient - αR = radial expansion coefficient (Linked option) - αH = CR-related coefficient - Function of fuel average temperature cladding average temperature coolant average temperature coolant inlet temperature externally introduced reactivity (ideal control rod)

  11. MATHEMATICAL MODEL (4) REACTIVITY COEFFICIENTS CALCULATION DOPPLER LEAD DENSITY RADIAL EXPANSION AXIAL EXPANSION

  12. SIMULATIONS (1) SOLUTION TECHNIQUE – MIMO (Multiple Input Multiple Output) SYSTEM modelling equations state-space representation: state vector: output vector: input vector:

  13. SIMULATIONS (2) ERANOS-2.1, JEFF-3.1 data library calculations

  14. RESULTS (1) LEAD INLET TEMPERATURE PERTURBATION (+10 K) Fuel average temperature Lead average temperature Clad average temperature Reactivity Power Core outlet temperature

  15. RESULTS (2) CONTROL ROD EXTRACTION (+50 pcm) Reactivity Lead average temperature Clad average temperature Power Fuel average temperature Core outlet temperature

  16. RESULTS (3) REACTOR CORE OPEN-LOOP STABILITY Study of the system representative TRANSFER FUNCTION qualitative insights into the response characteristics of the system STABILITYall the system poles with negative real parts

  17. CONCLUSIONS • preliminary evaluation of DEMO core dynamics • coupling of NEUTRONICS and THERMAL-HYDRAULICS • prediction of DEMO reactions to 10°C increase of lead inlet T • 50 pcm insertion by ideal CR • stable system • significant impact of reactivity insertion on reactor power (steady state: + 32/25 % nominal value at BoC/EoC) and fuel temperature (+ 276/220 K at BoC/EoC) • model with satisfactory capability of predicting the system response to both perturbations (small errors figured) • generally slight impact of assuming the fuel linked to the cladding or the radial expansion driven by the coolant average temperature • useful tool allowing a relatively quick, qualitative analysis of fundamental dynamics and stability aspects

  18. WORK PROPOSAL TASK 4.4 Preliminary definition of the Control Architecture • Primary loop modeling • Secondary loop modeling • Coupling between primary and secondary loops • Sensitivity analysis • Control and measured variables definition • Control strategy assessment (SISO loops and Multi-variable control, e.g. MPC)

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