1. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 1 EFIT Design and Transient Analysis M. Schikorr, E. Bubelis EUROTRANS: DM1 WP1.5 : Safety Madrid, 13-14 November 2007

2. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 2 1.Design Criteria for EFIT-Pb 2.EFIT design data for Transient Analysis 3.Some EFIT-Pb results to the ULOF transient Topics:

3. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 3 1.Use of MgO-based MA-MOX Fuel Mixture 2.Operate EFIT at k_eff ~ 0.95 - 0.97 with flat k_eff burnup characterisitics 3.Adopted 3-Core region design to obtain flat radial power profile (designed by ENEA and ANSALDO) 4.Design core and primary system in such a manner to allow sufficient natural convection flow rate to sustain a ULOF transient for at least 30 minutes without large number of pin failures (via gas blowdown) 5.Account for burn-up and protective oxide layer formation during operation of plant 1.Some important EFIT Design Criteria:

4. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 4 Assure a sufficiently large natural convection flow rate ( > 25 % nominal flow) under ULOF-ss conditions. This implies : 1.keep pressure drop across the core low (~< 0.75 bar) by selecting an appropriate fuel pin / subassembly design 2.minimize pressure losses throughout the primary / DHR system such that total system pressure loss <~ 1.0 – 1.1 bar 3.assure a height differential between the core midplane and the heat sink midplane of at least > 2.00 m EFIT ULOF Design Criteria requires :

5. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 5 1.Select an appropriate pin / sub-assembly design by optimizing the pin diameter, pin pitch, wrapper dimensions etc. 2.Minimize the number of grid-spacers and optimise design 3.Keep the length of the fuel pin low 4.Optimize inlet and outlet support structures to keep pressure drops small Keeping P_core in the XT-ADS Design low:

6. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 6 Most current EFIT Design Data: Inner Core Region, Core Zone 1

7. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 7 Most current EFIT Design Data: Intermediate Core Region, Core Zone 2

8. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 8 Most current EFIT Design Data: Outer Core Region, Core Zone 3

9. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 9 Other EFIT Data Inputs: 854mm lower gas plenum 274mm upper gas plenum

10. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 10 EFIT-Pb: Avg and Peak Cladding and Fuel Temperatures at Nominal and ULOF-ss Plant Conditions for BOC and EOC EOC state is defined to be max burnup ~ 100 MWd/kg of MOX-MA fuel

11. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 11 EFIT ULOF Transient Cases Analysed: 1.ULOF:BOC, Peak Pin, 6 Spacer @ 0.50mm thickness 2.ULOF:EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100 um oxide

12. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 12 EFIT-Pb : ULOF, BOC, Peak Pin, 6 Spacer @ 0.50mm thickness, no oxide Conclusion: For current design EFIT peak pin clad will NOT fail under BOC conditions even though of flow undershoot that is ~ 22 % nom. flow. Min Clad Failure Time ~ 17 hours

13. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 13 EFIT-Pb : ULOF, EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100um oxide Conclusion: For current design EFIT peak pin clad will most likely NOT fail under EOC conditions even though of flow undershoot ~ 22% (min. clad failure time ~ 1000 sec). Peak pin fission gas pressure will be </~ 100 bar.

14. Forschungszentrum Karlsruhe Technik und Umwelt IRS /FzK W.M.SchikorrEUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007 14 Conclusions on EFIT ULOF Transient : 1.)The ULOF transient is less sensitive in the Pb-cooled EFIT design than to the XT-ADS design because of its better natural convection characterisitcs: (38% of nominal flow for EFIT-Pb compared to ~ 25% nominal flow for the XT-ADS under ULOF-steady state conditions). 2.) The current design of the Pb-cooled EFIT system achieves the design goal of sustaining a ULOF transient for at least 0.5 hours without pin failures.