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EUROTRANS – DM1 Analysis of EFIT Unprotected Accidental Transients with PARCS/RELAP5 Coupled Code

EUROTRANS – DM1 Analysis of EFIT Unprotected Accidental Transients with PARCS/RELAP5 Coupled Code. G. Bandini, P. Meloni, M. Polidori. OUTLINE. Description of the Codes The modifications of RELAP5 Model of EFIT The PARCS Model of EFIT Analysis of Unprotected Transients

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EUROTRANS – DM1 Analysis of EFIT Unprotected Accidental Transients with PARCS/RELAP5 Coupled Code

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  1. EUROTRANS – DM1 Analysis of EFIT Unprotected Accidental Transients with PARCS/RELAP5 Coupled Code G. Bandini, P. Meloni, M. Polidori

  2. OUTLINE • Description of the Codes • The modifications of RELAP5 Model of EFIT • The PARCS Model of EFIT • Analysis of Unprotected Transients • Total Loss of Flow Accident • Beam Power Jump to 100% at HZP • Conclusions

  3. PARCS/RELAP5 Coupled Code Our State-of-the-Art code to simulate the Neutronic-T/H coupled phenomena for safety purpose is: PARCS v1.01 – 3D Neutronic coarse mesh code that solves the 2-group diffusion equation in cartesian geometry, modified to treat subcritical systems. RELAP5 mod 3.2.2b– Thermal-Hydraulic 1D code modified to treat HLM (Seban-Shimazaki heat transfer correlation implemented)

  4. RELAP5 Model – 6 Rings Active Core Region • Primary system layout by D1.26 of ANSALDO (November 2007) • Primary circuit pressure drops according to new ANSALDO data • Gagging at core inlet according to SIM-ADS • Core Region • Ring 1 – 18 FA (Inner Zone) • Ring 2 – 24 FA (Inner Zone) • Ring 3 – 30 FA (Interm Zone) • Ring 4 – 36 FA (Interm Zone) • Ring 5 – 42 FA (Outer Zone) • Ring 6 – 30 FA (Outer Zone) RELAP5 Noding Scheme

  5. PARCS Model and Assumptions PARCS Mesh Dimension Width = 8.27 cm Height = 9.55 cm EFIT Core Layout

  6. PARCS Model and Assumptions Axial Nodal Correspondance PARCS RELAP5 Vertical View of EFIT Core Layout

  7. XS Generation XSEC Formalism in PARCS XSEC Data Set to Find the Derivative Cross Sections • Omogenized • Collased in 2 groups • (0.079 MeV Cutting Energy) A keff calculation with the Base XSEC Data Set in ERANOS suggests a value of keff =0.97631 Normalization of nSf to achieve the desired keff Initial keff 0.958 keff 0.97515

  8. Main EFIT Parameters • PRIMARY SYSTEM: • Total power = 395.2 MW • Lead mass flowrate = 33243 kg/s • Lead temperature = 400 / 480 C • Total primary circuit pressure drop = 1.37 bar (core = 0.7 bar, SG = 0.4 bar, Pump = 0.27 bar ) • Total mass of lead = 5880 tons (ANSALDO data = 5954 tons) • Lead free levels = 1.085 / 1.495 / 0.448 (ANSALDO data = 1.085 / 1.473 / 0.406) • SECONDARY SYSTEM: • Feedwater flow rate (4 SGs) = 244.4 kg/s, Temperature = 335 C • Steam pressure = 140 bar • Steam temperature = 452 C (Superheating of 115 C)

  9. R5 SA vs P/R5 Steady-State Calculation

  10. Transients to be Analyzed by ENEA with P/R5

  11. Safety Limits • According to previous PDS-XADS safety analysis: • Clad temperature below 550 C during normal operation • Clad temperature in the range: • 550 – 600 C for less than 600 s, • 600 – 650 C for less than 180 s, in transient conditions • Vessel wall temperature below 450 C • Fuel temperature limited below 1380 C to avoid MgO inert matrix dissolution problem

  12. Analysis of Unprotected Transients • ULOF: Total loss of forced circulation in primary pumps • The coupling start from thermal-hydraulic nominal conditions and external source off. • After 1s the source is switched-on reaching the stationary conditions after 50s. • At 50s the primary pumps trip with system free evolution. • BEAM TRIP: Beam Power Jump to 100% at HZP • At 50s the external source is switched-off then 100s of free evolution (decay heat is not considered) • At 150s the external source is switched-on at 100% then free evolution

  13. Unprotected Loss of Flow Transients Keffective and Reactivity Reactor and SG power • 130 pcm inserted during the LOF transient • 3% of Power reduction

  14. Unprotected Loss of Flow Transients Lead Temperature Lead Mass Flowrate • Core mass flow rate drop down almost to 0 in the initial transient • Slight overcooling of the Lead in the heat exchanger

  15. Unprotected Loss of Flow Transients Temperature Ring 3 (Intermediate Zone) • Fuel Peak Temperature 1530°C, 1460°C in long term conditions. • Clad Peak Temperature 810°C approaching the 700°C in long term conditions.

  16. Beam Trip Transients Keffective and Reactivity Reactor and SG power • 100 pcm inserted during the Beam Trip and reinsertion transient • Decay Heat not take into account

  17. Beam Trip Transients Lead Temperature Temperature Ring 3 (Intermediate Zone) • The Beat Trip transient seems to be not a safety issue for the system.

  18. CONCLUSIONS • The resultsobtainedby PARCS/RELAP5 coupledboth at nominal and at ULOF accidentalconditions are in good agreement withthatobtainedby RELAP5 Stand Alone. • Some work hastobedonetoimprove the powerdistributionamong the FA rings. • Itisnotforeseentocarry out EOL UnprotectedTransients due to the verysmalldiffenceexpected.

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