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Use of Fission Product Release results for IRSN safety studies

Use of Fission Product Release results for IRSN safety studies. Dr. Grégory NICAISE . IRSN / DSR (Reactor Safety Department). International VERCORS Seminar October 15-16th, 2007 Gréoux les Bains, France. Partners. Safety analysis and physical studies Probabilistic Safety Assessments

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Use of Fission Product Release results for IRSN safety studies

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  1. Use of Fission Product Release results for IRSN safety studies Dr. Grégory NICAISE IRSN / DSR (Reactor Safety Department) International VERCORS Seminar October 15-16th, 2007 Gréoux les Bains, France Partners

  2. Safety analysis and physical studies • Probabilistic Safety Assessments • IRSN/DSR (Reactor Safety) • IRSN/DPAM (FP research) • Vercors result analysis • FP release mechanisms Partners IRSN management of FP release(Severe Accidents) 2/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  3. “S3” Source Term S3 Source Term • FP release calculations (from the reactor core) Core FP release model Activity and Power • Kinetics of activity and power release(to the containment) Reflooding studies • Reflooding studies FP release model for PSA lev2 Expectations on ST estimation • Generic FP release model for PSA (level2) • Expectations on Source Term estimation Partners Main uses of VERCORS results for safety analysis 3/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  4. “S3” FP released fraction in case of full core melting Partners S3 Source Term S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 4/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  5. Physical Interpretations Empirical Correlations VERCORS tests UO2 pellet ~10-2 m PWR UO2 core ~101 m MFPR Code UO2 grain ~10-6 m Meso scale Modelisation “S3 Normalisation” Partners “MFPR Core Calculations” FP release from a reactor core1.Physical scales S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 5/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  6. Fast Core melting 3h -VULCAIN Code- Slow Core melting 10h 24 axial meshes 5 radial meshes Partners 5 4 3 2 1 FP release from a PWR core2.Multi-zone calculations/temperature data S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 120 temperature transients 6/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  7. 2 radial meshes 4 axial meshes Balanced sum (mesh burnup and mass) Mass balance Burnup balance Partners FP release from a PWR core3.Multi-zone calculations/ MFPR 8 zones 8 MFPR Calculations (neutral H2O/H2 atmosphere) S3 Source Term Core FP release model “S3” normalisation for each FP (highest VERCORS release) Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 7/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  8. Partners FP release from a PWR core4.Multi-zone calculations/ Results Fast Core melting 3h S3 Source Term Core FP release model Activity and Power Reflooding efficiency Slow Core melting 10h FP release model for PSA lev2 Expectations on ST estimation 8/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  9. Power released to containment Iodine is 50% Activity released to containment Iodine is 30% • FP identification of activity and power contributions • Containment chemistry Partners Activity and Power release to containment S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 9/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  10. Containment activity comparison for different refloodings Partners Reflooding efficiency studies S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 10/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  11. Partners FP Release model for PSA lev21. FP classification • Need of a generic (be applied to all severe accident sequences) and simple (linear) S3 Source Term GROUP 1  First aerosols I Cs Te Mo Br Rb Se Rh Tc Core FP release model Activity and Power GROUP 2 Noble Gases Xe Kr Reflooding efficiency FP release model for PSA lev2 GROUP 3 Second Aerosols Sb Sr Ba Ru Zr Nb La Ce Y Nd Eu Pr Np U Pu Am Cm Expectations on ST estimation 11/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  12. Mass (kg) Noble gases t0 t1 temps t_DEN 100% • t2 = 0.2 t_DEN100% + 0.8 t1 • t1f = 0.8 t_DEN100% + 0.2 t1 t_DEN 100% Mass (kg) Second aerosols • Reflooding case 1% masse Classe (S3) t1 t2 First aerosols Partners t0 t1 t2 temps t1f t_DEN 100% Mass (kg) 80% 20% t0 t1 t2 temps t1f Mass(kg) (S3) (S3) (S3) t_DEN t0 t1 t2 t1f t_DEN 100% FP Release model for PSA lev22. FP release model construction S3 Source Term Core FP release model Activity and Power Reflooding efficiency FP release model for PSA lev2 Expectations on ST estimation 12/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

  13. Partners Expectations on Source Term estimations S3 Source Term • High benefits of release kinetic acknowledgments from VERCORS tests Core FP release model Activity and Power • FP emission to containment is better estimated Reflooding efficiency • Containment atmospheric aerosols are dynamically quantified FP release model for PSA lev2 Expectations on ST estimation • Better estimation of source term in case of early containment loss 13/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

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