1. Accident assessment for DCLL DEMO design Susana Reyes TBM Project meeting, UCLA, Los Angeles, CA March 2-4, 2005 Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

2. SR—3/3/05 Outline  Preliminary accident analysis for DCLL DEMO  Decay heat removal results for DCLL TBM  Summary of cross-section uncertainty analysis for DC DEMO activation results

3. SR—3/3/05  Created MELCOR thermal-hydraulics model for DCLL DEMO accident assessment  Model represents ¼ of the full-scale reactor  Dimensions and nuclear heating values from M. Sawan; decay heat results from M. Youssef  Values for temperatures, mass flows and pipes taken from S. Malang’s memo (8/16/04)  Several iterations needed to adjust the balance of plant, heat exchangers, etc Preliminary accident assessment of DCLL DEMO concept

4. Radial View High temp shield Outboard Inboard Plasmachamber Blanket VV Accumulator LiPb HX Drain tank Blanket High temp shield Pressurizer Top View Vacuum vessel(VV) Vacuum vessel(VV) High Temp shield IB Blanket Inboard Outboard High Temp shield OB Blanket He pipes LiPb pipes Secondary He HX Model is 1/4 th of full reactor PbLi temperatures 460/700°C PbLi mass flow 329 kg/s He temperatures 360/460°C He mass flow 20 kg/s

5. SR—3/3/05  Preliminary accident analysis for a loss of He coolant (LOCA) into the breeder blanket  Model assumes break of one FW cooling channel and leakage of He gas (8 MPa) to first LiPb breeder channel (1 MPa)  Reactor is scrammed and pumps coast down on a high blanket pressure signal, immediately after accident  We want to assess pressurization of the blanket during the accident In-blanket He LOCA has been modeled Vacuum vessel(VV) Vacuum vessel(VV) High Temp shield IB Blanket Inboard Outboard High Temp shield OB Blanket Plasma chamber

6. SR—3/3/05  MELCOR results show pressurization of blanket occurs in only ~ 4 seconds  Drain line opens 100 s after the accident occurs  FW temperature cools down by radiation to vacuum vessel after drain line opens MELCOR results for in-blanket LOCA

7. SR—3/3/05 Assessment of DCLL TBM Passive Decay Heat Removal  ITER safety requirement is that decay heat removal should be achieved by thermal radiation to the basic machine  CHEMCON 1D heat transfer model of DC TBM was used for this analysis with decay heating from M. Youssef  Adequate decay heat removal demonstrated by thermal radiation to ITER in-vessel structures  Maximum FW temperature ~ 595 °C at 1 hr due more to thermal equilibration rather than decay heating CHEMCON Results ITER FW TBM FW (baseline) 0246 810 Time (d) 200 300 400 500 600 Temperature (C) TBM FW (high performance)

8. SR—3/3/05  Completed uncertainty analysis using Monte Carlo procedure included in the ACAB code  Method uses simultaneous random sampling of all XS probability density functions involved in the problem  Nuclear data from European Activation File (EAF-2003): EAF_XS (Cross sections), EAF_UN (XS Uncertainty), EAF_DEC(Decay Data) Analysis of effect of cross-section uncertainty on DEMO FW activation  Inventory predictions for 60 Co and 94 Nb, are responsible for significant errors at long cooling times (>8 yrs, significant for waste management)  The XSs 59 Co(n,g-m) 60m Co and 93 Nb(n,g-m) 94m Nb have been identified as those need of improvement for an overall reduction of the uncertainty

9. SR—3/3/05 Summary  Preliminary in-blanket LOCA analysis for DCLL DEMO design shows pressurization of blanket module would occur~ 4 seconds  LOFA assessment for DCLL TBM demonstrates adequate decay heat removal by thermal radiation to ITER in-vessel structures  Completed activation cross section uncertainty analysis for DEMO FW and identified cross sections 59 Co(n,g-m) 60m Co and 93 Nb(n,g-m) 94m Nb as those need of new measurements for overall improvement of FW activation predictions