WP 1.5 Progress Meeting ENEA – Bologna, Italy, May 28-30, 2008 FPN-FISNUC / Bologna EUROTRANS – DM1 Analysis of EFIT Unprotected Accidental Transients with PARCS/RELAP5 Coupled Code G. Bandini, P. Meloni, M. Polidori

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30,  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 OUTLINE

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, 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  – Thermal-Hydraulic 1D code modified to treat HLM (Seban-Shimazaki heat transfer correlation implemented)

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, RELAP5 Model – 6 Rings Active Core Region RELAP5 Noding Scheme  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)

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, PARCS Mesh Dimension Width = 8.27 cm Height = 9.55 cm EFIT Core Layout PARCS Model and Assumptions

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Vertical View of EFIT Core Layout PARCSRELAP5 Axial Nodal Correspondance PARCS Model and Assumptions

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, XS Generation XSEC Formalism in PARCS Tfuel 400°C750°C1100°C Tcoolant 400°COOO 440°CO 550°COO XSEC Data Set to Find the Derivative Cross Sections  Omogenized  Collased in 2 groups (0.079 MeV Cutting Energy) Initial k eff  A k eff calculation with the Base XSEC Data Set in ERANOS suggests a value of k eff = Normalization of  f to achieve the desired k eff k eff 

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30,  PRIMARY SYSTEM:  Total power = MW  Lead mass flowrate = 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 = / / (ANSALDO data = / / 0.406)  SECONDARY SYSTEM:  Feedwater flow rate (4 SGs) = kg/s, Temperature = 335 C  Steam pressure = 140 bar  Steam temperature = 452 C (Superheating of 115 C) Main EFIT Parameters

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, R5 SA vs P/R5 Steady-State Calculation Maximum temperature (°C) Code Inner zone (Fax = 1.14) Middle zone (Fax = 1.16) Outer zone (Fax = 1.17) Hot FA Fr =1.12 Fr =1.03 Averag e FA 41/42 Hot FA Fr = 1.13 Fr = 1.10 Avera ge FA 65/66 Hot FA Fr = 1.24 Fr = 1.20 Avera ge FA 71/72 Center fuel R5 SA P/R Surface fuel R5 SA P/R Internal clad R5 SA P/R External clad R5 SA P/R Lead R5 SA P/R ParameterCodeInner zone Middle zone Outer zone ReflectorTargetTotal Thermal power (MW) R5 SA P/R “ 11.2 “ Lead mass flow rate (kg/s) R5 SA P/R By- pass outlet Target outlet

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Transients to be Analyzed by ENEA with P/R5 TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN NumberTransientDescriptionBOCEOC ENEA RELAP5 (X-S) RELAP/PARCS (X-C) SIMMER PROTECTED TRANSIENTS P-10 Spurious beam trip beam trip for 1,2,3 ….. 10 s intervals x?X-C UNPROTECTED TRANSIENTS U-1ULOF Total loss of forced circulation in primary system (4 pumps) x?X-CX U-2UTOP (?) pcm jump in reactivity at HFP x?X-C U-4 DECULOH Total loss of secondary loops (4 loops) x?X-C U-5 DECULOF + ULOH Total loss of forced circulation and secondary loops x?X-C U-11 Beam Overpower to (?)% at HFP x?X-C U-12 Beam Power Jump to 100% at HZP x?X-C

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, 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

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, 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

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Keffective and Reactivity Reactor and SG power Unprotected Loss of Flow Transients  130 pcm inserted during the LOF transient  3% of Power reduction

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Lead Mass Flowrate Lead Temperature Unprotected Loss of Flow Transients  Core mass flow rate drop down almost to 0 in the initial transient  Slight overcooling of the Lead in the heat exchanger

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Temperature Ring 3 (Intermediate Zone) Unprotected Loss of Flow Transients  Fuel Peak Temperature 1530°C, 1460°C in long term conditions.  Clad Peak Temperature 810°C approaching the 700°C in long term conditions.

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Keffective and Reactivity Reactor and SG power Beam Trip Transients  100 pcm inserted during the Beam Trip and reinsertion transient  Decay Heat not take into account

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, Lead Temperature Beam Trip Transients Temperature Ring 3 (Intermediate Zone)  The Beat Trip transient seems to be not a safety issue for the system.

EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, CONCLUSIONS  The results obtained by PARCS/RELAP5 coupled both at nominal and at ULOF accidental conditions are in good agreement with that obtained by RELAP5 Stand Alone.  Some work has to be done to improve the power distribution among the FA rings.  It is not foreseen to carry out EOL Unprotected Transients due to the very small diffence expected.