EUROTRANS – DM1 RELAP5 Model Evaluation with SIMMER-III Code and Preliminary Transient Analysis for EFIT Reactor WP5.1 Progress Meeting KTH / Stockholm, May 22-23, 2007 P. Meloni, G. Bandini, M. Polidori FPN-FISNUC / Bologna

EFIT Transient Analysis by ENEA  Use of SIMMER-III code for in-vessel natural circulation assessment and DHR performance evaluation  RELAP5 model evaluation and revision based on SIMMER-III results  Preliminary transient analysis (PLOHS and ULOF) with revised RELAP5 model KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting

EFIT Design and Parameters  Primary circuit layout from ANSALDO presentation at the last EUROTRANS - DM4 Technical Review Meeting (March 2007):  Reactor core with 3 fuel zones  4 primary pumps, 8 IHXs, 4 secondary loops  4 DHR units (3 out of 4 in operation in transient analysis)  Primary circuit parameters:  Active core thermal power = 379 MW (ENEA study)  Lead mass flowrate = kg/s  Core inlet / outlet temperature = 400 / 480 C  Total pressure drop = 43 kPa (core pressure drop = 36 kPa) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting

Used Approach KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting SIMMER-III calculation PLOHS (beam trip at t = 0 s) 3 DHR in operation Recirculation ratio at DHR outlet RELAP5 calculation PLOHS (beam trip at t = 0 s) 3 DHR in operation Comparison Additional RELAP5 pressure drop coefficients to fit core and DHR natural circulation mass flow rates (SIMMER) Comparison with ANSALDO data RELAP5 revised model Transient analysis with RELAP5 ULOF PLOHS (beam and pump trip if aver. core out T > 500 C) RELAP5 model evaluation and transient analysis Comparison ULOF with SIMMER-III

SIMMER-III Model of EFIT KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting  2-D R-Z (36 x 35) Cylindrical model  Initial condition with stagnant lead and free level DH simulation  Harmonization with RELAP5 plant data and boundary conditions  No steam generator heat losses  3 out of 4 DHR units in operation (degraded conditions)  DHR heat removal based on constant oil temperature in secondary side (Tin = 405 C, Tout = 409 C)

SIMMER-III Results (Lead Temperature) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting

SIMMER-III Results (Lead Temperature) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting

SIMMER-III Results at 3600 s (Lead Velocities) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting Horizontal velocityVertical velocity

SIMMER-III ANSALDO Results at after 1 hour t = 3600 s: (P = 16 MW) m C = 2740 kg/s m D = 2983 kg/s 2985 Kg/s T Ci = C T Co = C T Di = C 444 C T Do = C 407 C Recirculation Ratio at DHR Outlet for RELAP5 KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting y = m C (T Di - T Do ) (T Ci - T Do ) x = y + m D - m C y = 255 kg/s Recirculation ratio at DHR outlet: x = 498 kg/s (17% of m D ) Simplified scheme of RELAP5 model x y mCmC mDmD T Ci T Co T Do T Di T Ci T Co T Ci T Co

SIMMER and RELAP5 Comparison at t = 3600 s KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting ParameterUnitSIMMER-IIIRELAP5 Core mass flow rateKg/s Core inlet temperatureC Core outlet temperatureC DHR mass flow rate (3 units)Kg/s DHR inlet temperatureC DHR outlet temperatureC DHR removed power (3 units)MW Additional pressure drop coefficients in RELAP5 model to fit SIMMER-III results RELAP5 (revised)

Code Result Comparison (Transient) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting Core mass flow rate and temperature Core inlet / outlet temperature Core mass flow rate  After the initial transient (about 2000 s) the revised RELAP5 model fit very well the SIMMER-III results

Code Result Comparison (Transient) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting DHR mass flow rate and temperature DHR mass flow rate DHR inlet / outlet temperature  After the initial transient the revised RELAP5 model fit well the SIMMER-III results, and stable DHR operation is predicted by both codes

Code Result Comparison (Transient) KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting Core decay power and DHR removed power

Preliminary Transient Analysis with RELAP5 KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting  Protected Loss of Heat Sink (PLOHS) at BOC with beam and pump trip when average outlet core temperature exceeds 500 C and DHR degraded conditions (3 out of 4)  Unprotected Loss of Flow (ULOF) at BOC with SGs full capacity and without reactivity feedback (constant core power)

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting Maximum temperature (°C) Inner zone (Fax = 1.14) Middle zone (Fax = 1.16) Outer zone (Fax = 1.17) Hot FA 1/42 Fr = 1.12 Average FA 41/42 Hot FA 1/66 Fr = 1.13 Average FA 65/66 Hot FA 1/72 Fr = 1.24 Average FA 71/72 Central fuel Surface fuel Internal clad External clad Lead ParameterInner zone Middle zone Outer zone Reflector + by-pass Total Thermal power (MW) (*)378.8 Lead mass flow rate (kg/s) Nominal Conditions (RELAP5 steady-state) (*) about 5 MW (not considered in this study)

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOHS Transient Results (Relap5) Core and DHR mass flow rate Initial transient About 3 hours transient  Proton beam and pump trip is assumed at 73 s (average lead temperature at core outlet > 500 K)  After some initial oscillations (free levels movements) both core and DHR mass flow rates became stable

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOHS Transient Results (Relap5) Core and DHR power Initial transient About 3 hours transient  The DHR system reaches full operation after about 600 s  A maximum of 20 MW power can be removed by 3 DHR units in operation)

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOHS Transient Results (Relap5) Max lead and clad temperature Initial transient About 3 hours transient  Peak clad temperature reaches 585 C in the hot channel of inner core zone  Max lead and clad temperature stabilize at about 450 C after 6000 s

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOHS Transient Results (Relap5) Max fuel temperature (hot channel) Initial transient About 3 hours transient Max vessel wall temperature  The vessel wall temperature reaches a maximum of about 460 C after 3000 s and reduces below 440 s after s

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF Transient Results (Relap5) Core and SG exchanged power Core mass flow rate Core mass flow rate and power  All primary pumps stop at 0 s (no pump inertia), secondary loops at nominal conditions  Core mass flow rate stabilizes at about 37% of the nominal value

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF Transient Results (Relap5) Max lead temperature (top of active zone) Average channel temperature Hot channel temperature  Peak lead temperature reaches about 850 C in the hot channel of inner core zone just after pump stop  Max lead temperature stabilizes at about 625 C in the hot channel of outer core zone

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF Transient Results (Relap5) Max clad temperature (top of active zone) Average channel temperature Hot channel temperature  Peak clad temperature reaches about 870 C in the hot channel of inner core zone just after pump stop  Max clad temperature stabilizes at about 660 C in the hot channel of inner core zone

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF Transient Results (Relap5) Max fuel temperature (centre of active zone) Average channel temperature Hot channel temperature  Peak fuel temperature reaches about 1525 C in the hot channel of middle core zone just after pump stop  Max fuel temperature stabilizes at about 1405 C in the hot channel of middle core zone

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF with SIMMER-III (Lead Temperature)

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF with SIMMER-III (Lead Temperature)

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF with SIMMER-III at 1000 s (Lead Velocities) Horizontal velocityVertical velocity

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF: SIMMER-III – RELAP5 Comparison Core mass flow rate and temperature Core inlet / outlet temperature Core mass flow rate  SG tube temperature in SIMMER-III calculation is imposed according to RELAP5 results  After the initial transient (about 200 s) there is a good agreement in code results

KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting Use of SIMMER-IV (3-D Calculation) In progress (Convergence and CPU time problems still to be solved) A A B B Section A - A Section B - B