1. ERMSAR 2012, Cologne March 21 – 23, 2012 1 The Experimental Results of LIVE-L8B: Debris Melting Process in a Simulated PWR Lower Head X. Gaus-Liu, A. Miassoedov, T. Cron, S. Schmidt-Stiefel, T. Wenz Karlsruhe Institute of Technology (KIT), Germany

2. ERMSAR 2012, Cologne March 21 – 23, 2012 2 Outline Objectives LIVE-3D test facility Test definitions Test results: – dry-out debris bed temperature – debris melting process – Steady-state melt pool and crust behaviour Conclusion

3. ERMSAR 2012, Cologne March 21 – 23, 2012 3 Objectives Dry-out debris bed temperature distribution in large-scale semispherical geometry → the position of the initiation of melting Debris bed melting process after liquid melt relocation in the lower plenum → penetration depth of a liquid melt jet, melt pool progression, melt temperature development TH steady-state melt behaviour

4. ERMSAR 2012, Cologne March 21 – 23, 2012 4 LIVE 3D test facility 1:5 scaled 3D PWR lower head, external cooling and top cooling temperature profiles, heat flux distribution, crust analysis: growth rate, composition, heat conductivity simulant: 20% NaNO 3 - 80-mol% KNO 3

5. ERMSAR 2012, Cologne March 21 – 23, 2012 5 Melt temperature measurements

6. ERMSAR 2012, Cologne March 21 – 23, 2012 6 LIVE L8B test definition 50% of the total 355 kg simulant material prepared as debris bed and preheated in the test vessel, the other 50% prepared as liquid melt and poured in the vessel afterwards; debris porosity 50%, particle size 3- 16 mm 21 kW homogenous heat input after pouring water cooling short before melt pouring

7. ERMSAR 2012, Cologne March 21 – 23, 2012 7 Experimental data of debris bed dry-out temperature

8. ERMSAR 2012, Cologne March 21 – 23, 2012 8 Debris melting process-melt pool formation Melt pool formed initially at the top region; Till 1500 s downwards extension; Thereafter sideward's extension.

9. ERMSAR 2012, Cologne March 21 – 23, 2012 9 Fraction of liquid melt during melting process

10. ERMSAR 2012, Cologne March 21 – 23, 2012 10 Debris melting process- initial melt temperature with debris melting process without debris melting process

11. ERMSAR 2012, Cologne March 21 – 23, 2012 11 Penetration of melt jet and crust structure crust at upper part crust at bottom

12. ERMSAR 2012, Cologne March 21 – 23, 2012 12 Final crust thickness The determination of pool/crust boundary according to the melt temperature measurement is precise; Final crust volume fraction 10.6 % Final crust mass fraction 8.3 % The difference comes from the loose debris layer at bottom

13. ERMSAR 2012, Cologne March 21 – 23, 2012 13 Steady-state melt temperature L8B steady-state melt temperature distribution is comparable with tests without the process L8B crust at bottom is thicker than the crust formed without debris melting

14. ERMSAR 2012, Cologne March 21 – 23, 2012 14 Steady state heat transfer characteristics 83 % of the heat transferred through the vessel wall q max /q mean = 2 Nu dn =202 Ra i =4.3 x10 13

15. ERMSAR 2012, Cologne March 21 – 23, 2012 15 Conclusion- 1 In a dry-out debris bed with volumetric heat release the highest temperature locates in the middle-upper region in the debris bed; After melt relocation, a melt pool in a debris bed is formed initially at the top region; A part of the relocated liquid melt freezes in the debris bed firstly; The relocated melt jet penetrates in the debris bed easier sidewards than downwards; During the melting process, the melt pool enlarges its boundary mainly downwards at the beginning, then sidewards;

16. ERMSAR 2012, Cologne March 21 – 23, 2012 16 Conclusion- 2 Melt pool temperature remains low during the debris melting process; Steady-state melt temperature after debris melting process is comparable with the one without the melting process.

17. ERMSAR 2012, Cologne March 21 – 23, 2012 17 Thank you for your attention