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Status of safety analysis for HCPB TBM

Status of safety analysis for HCPB TBM. Susana Reyes TBM Project meeting, UCLA, Los Angeles, CA May 10-11, 2006 Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Outline. Background Objectives

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Status of safety analysis for HCPB TBM

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  1. Status of safety analysis for HCPB TBM Susana Reyes TBM Project meeting, UCLA, Los Angeles, CA May 10-11, 2006 Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  2. Outline • Background • Objectives • Status of safety analysis • Source terms (radioactive, energy) • Decay heat removal • Ex-vessel LOCA analysis • Summary and plan

  3. Background • Each TBM contains radioactivity and energy source terms that must be identified • Radioactive source terms: tritium, activated components and materials • Energy source term: chemical, decay heat, enthalpy • Two steps must be completed as part of the TBM licensing process: • ITER Report on Preliminary Safety (RPrS), and associated documents (beg 2008) • Final Safety Report (by 2016) • Work now is focussed on updating DDD safety section, input from DDD will be used for the ITER RPrS • July 2006: initial DDD safety sections, including operational releases, radioactive inventories, decay heat, chemical sources, WDR • December 2006: final DDD safety sections, including specific accident scenarios • December 2006 to July 2007: ITER will select enveloping TBM results per category to include in the RPrS (not all TBM results will be included)

  4. Objectives • It is likely that full blown accident analysis will not be necessary for US HCPB TBM as long as it is similar to JA or EU concepts • Need to demonstrate that accident source term (radioactive inventories, chemical energy and enthalpy) in US TBM are similar or smaller than those in JA and EU HCPB TBM • Objectives of preliminary safety analysis: • address source terms (energy sources, activation products), decay heat and WDRs • demonstrate that the change in geometry in US TBM concept does not affect the decay heat removal capability of TBM • analyze thermal response of the module to an ex-vessel LOCA

  5. Status of safety analysis for US HCPB submodule • New US HCPB TBM dimensions (1/3 of half-port submodule) • Started to update safety analyses using new configuration 1/3 of half port submodule (71cmx38.9cmx60cm) 1/4 port submodule (91cmx73cmx60cm)

  6. Source terms in US HCPB TBM Material source term

  7. Activation calculations needed to determine radioactive source term • Do not have full neutronics analysis for US HCPB TBM, it would take a few weeks to set up 3-D neutronics Monte Carlo model • FW neutron flux for ¼ port submodule is known (M. Youssef, 4/05) and used to calculate new submodule FW activation • ACAB calculation using 41494 pulses of 400 s on, 1800 s cooling (to reach 0.3 MWa/m2 at average ITER NWL=0.57 MW/m2) • at shutdown Fe-55, Mn-56, Mn-54, Cr-51 and W-185, sum up 85% of the total 5.9x104 Ci (DCLL TBM is 7.65x104 Ci) • inventories for rest of HCPB submodule should be bounded by EU and JA TBMs • preliminary WDR estimation using FW neutron flux for all the components shows WDR acceptable

  8. Activation calculations: decay heat • Results from FW activation show that decay heat is less than that calculated for EU and JA HCPB TBMs, it can be anticipated that decay heat removal is not a concern for US HCPB submodule • For a detailed decay heat removal calculation need to have neutron fluxes for all components (need neutronics calculation) US HCPB TBM JA HCPB TBM

  9. Breeder channels Cooling plates Be multiplier FW Ex-vessel LOCA analysis • Assumed parallel configuration, surface heat flux = 0.5 MW/m2 • Used nuclear heating from previous TBM design and scaled for actual configuration (M. Youssef, et al., Fusion Eng. and Design 81, 2006) • Ex-vessel He LOCA at power, 2 scenarios considered: • Plasma shutdown occurs when Be armor melts (~1250 C) • Active plasma shutdown at t =100 s Manifold CHEMCON 1-D heat transfer model

  10. Ex-vessel LOCA analysis: results • Be temperatures in front portion of the bed is well above 800 °C (reaction rates high and access O2 should be avoided) • FW temperatures above 900 °C, material has practically no rigidity and we must assume FW failure • It is proposed here to introduce an active system for plasma shut down at t=100 s • FW front reaches high temperatures but the rear <800 °C, as the mechanical load is small rupture of the first wall is inhibited Temperature evolution during ex-vessel LOCA, plasma shutdown at t=100 s Temperature evolution during ex-vessel LOCA, no plasma shutdown

  11. Summary and plan • Preliminary safety analysis initiated for US HCPB TBM • Demonstrated that accident source term (radioactive inventories, chemical energy and enthalpy) in US TBM is smaller than JA and EU HCPB TBM • Full blown accident analysis will probably not be necessary for US HCPB TBM, however: • need detailed neutronics analysis for US HCPB TBM • need detailed activation analysis for decay heat and radioactive inventory/waste assessments • other accident scenarios (in-vessel LOCA, in TBM-box LOCA)? • Need to address tritium inventories and releases • Still need to address the impact of the edge-on configuration on safety analyses

  12. Comparison to EU and JA ex-vessel LOCA results US HCPB TBM EU HCPB TBM JA HCPB TBM

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