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

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

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

5. FP release from a reactor core 1.Physical scales 5/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE MFPR Code UO 2 grain ~10 -6 m VERCORS tests UO 2 pellet ~10 -2 m PWR UO 2 core ~10 1 m Physical Interpretations Meso scale Modelisation Empirical Correlations MFPR Core Calculations S3 Normalisation Partners Core FP release model Activity and Power Reflooding efficiency Expectations on ST estimation FP release model for PSA lev2 S3 Source Term

6. FP release from a PWR core 2.Multi-zone calculations/temperature data 6/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE Fast Core melting 3h Slow Core melting 10h 1 5 4 3 2 -VULCAIN Code- 24 axial meshes5 radial meshes 120 temperature transients Partners Core FP release model Activity and Power Reflooding efficiency Expectations on ST estimation FP release model for PSA lev2 S3 Source Term

7. FP release from a PWR core 3.Multi-zone calculations/ MFPR 8 zones 7/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE 8 MFPR Calculations (neutral H 2 O/H 2 atmosphere) S3 normalisation for each FP (highest VERCORS release) 4 axial meshes 2 radial meshes Partners Core FP release model Activity and Power Reflooding efficiency Expectations on ST estimation FP release model for PSA lev2 S3 Source Term Balanced sum (mesh burnup and mass) Mass balance Burnup balance

8. FP release from a PWR core 4.Multi-zone calculations/ Results 8/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE Partners Core FP release model Activity and Power Reflooding efficiency Expectations on ST estimation FP release model for PSA lev2 S3 Source Term Fast Core melting 3h Slow Core melting 10h

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

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

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

12. FP Release model for PSA lev2 2. FP release model construction 12/13 INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE Partners Core FP release model Activity and Power Reflooding efficiency Expectations on ST estimation FP release model for PSA lev2 S3 Source Term tempst0t0 t1t1 Mass (kg) Noble gases t_DEN 100% Second aerosols tempst0t0 t1t1 Mass (kg) t 1f t2t2 t_DEN 100% t1t1 t2t2 1% masse Classe (S3) First aerosols t_DEN 100% temps 20% 80% t0t0 t1t1 Mass (kg) t 1f t2t2 t 2 = 0.2 t_DEN 100% + 0.8 t 1 t 1f = 0.8 t_DEN 100% + 0.2 t 1 t0t0 t1t1 Mass(kg) t 1f t2t2 t_DEN 100% (S3) t_DEN Reflooding case

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