Engineering models in the ARIES system code, Part II M. S. Tillack, X. R. Wang, et al. ARIES Project Meeting January 2011

Summary of status in October 2010 Line-by-line review of DesignPoint.cpp was performed Numerous major and minor concerns were identified with power flow models in VASST  Thermal conversion efficiency  Pumping power in the blanket and divertor  Power density limits  Pump efficiencies  Fusion power partitioning to components We decided to evaluate the potential impact of changes and concentrate on those with significant expected effect on system code output

Action Items from October System code contributions (Lane and Chuck) (end of Nov inputs, end of Dec implement) 1.Output formatting (Lane, Laila, Les, Chuck, …) 2.System code models of volumes, inclusion of He systems (Lane, Laila, Les) 3.New models for pumping power – He (Mark, Minami, Xueren) and PbLi (Mark, Neil, Siegfried) 4. Power cycle model (First quantify the impact of uncertainties ) (Mark, Xueren, Lane) 5.Poloidal distribution (including divertor) of heat flux CAD skeleton (Xueren) Wall load and core radiation formulas (Laila) Mantle and divertor radiation (Mark, Tom?, Chuck?) 1.Define the approach for modeling heat fluxes in the code 2.Provide the models 6.Decommissioning and waste handling costs (Laila)

He pumping power in the divertor Analysis of three options performed, with some amount of optimization vs. heat flux (more design optimization underway). Results reduced to polynomial fits with very high R 2 No accommodation of profiles (yet)  Velocity calculated from peak location is used at all locations

MHD pressure drop in the blanket Previous studies used a fully-developed channel flow formula   p=0.25 MPa for ARIES-AT, dp/dx=10 -3 MPa/m for ARIES-CS However, the pressure drop from fully-developed channel flow is small compared with 3d effects  Bends  Entrance/exit to magnetic field  Flow channel insert overlaps A standard method is to apply K factors, similar to ordinary flows   p 3d = k N (  v 2 /2)  Each 3d perturbation contributes 0.1~0.5 MPa for the “standard DCLL” blanket

Inboard MHD pressure drop can be a serious concern ARIES-ST, where the DCLL was originally developed, had no inboard blanket and very low outboard B (2 T on axis, 1.25 T outboard midplane) Pressure drop depends on B 2   p 3d = k N (  v 2 /2), N = Ha 2 /Re =  dB 2 /  v  BR~constant  For the pre-strawman, B o =6.25, R o =5.5, a=1.375  B 2 inboard /B 2 outboard = 2.5  Detailed design is needed to evaluate and optimize MHD pressure drops Limited inboard space leads to higher flow speed Lower inboard power flows may help Detailed design is needed to better evaluate and optimize MHD pressure drops

Total blanket pumping power Combined He in FW (with bends), grid plates, HX and LM MHD Tests for self-consistent temperature rise and heat transfer Result is a simple quadratic fit for the system code I can segregate LM and He powers if desired

Thermal conversion efficiency models were not changed The entire effect is caused by degradation of bulk outlet temperature due to internal heat transfer: very design-dependent Minor variation at lower wall loads expected for our strawmen For DCLL, surface heat flux has minimal effect below 0.5 MW/m 2 Not clear why  th depends so strongly on q for AT blanket; probably this could be fixed (DCLL) (SiC)

Characterizing divertor and first wall heat loads with reduced models suitable for ARIES systems code - LLNL Divertor heat loads come primarily from plasma exhaust power, P p ; heat flux S d = P p /4  R  d  d,  d ~ ½ –Combined approaches to be used 1.Kukushkin/Pacher parameterization of acceptable pedestal parameters based on SOLPS modeling (published NF, JNM), to determine  d DOE experimental Joint Milestone gives  d ~ 1/I p 3.Two-point (midplane/divertor) models for SOL 4.Divertor-leg radiation from high density, low temperature plasma; specified by impurity content and divertor retention of impurities First-wall heat loads primarily from radiation loss 1.Mantle radiation profiles can come from neutronics codes (treat edge as part of core) or UEDGE 2.SOL radiation to FW is expected to be small 77% mantle radiation loss ARIES-AT

NEW: Pump efficiencies were reviewed and updated PbLi MHD pump: 40% (optimistic) PbLi mechanical pump: 80% (Morley) (S. Malang: suggests using 90%, 5% recoverable) He compressor: 90% (5% recoverable)

Partial recovery of pumping power Wall plug power (100%) LM pump (40% efficient) Pump inefficiency lost (20%) LM heating within pump (40%) System pressure drops result in LM heating (40%) Thermal energy recovered at  th (80% x  th ) HX blanket (MHD pump example)

Partial recovery of pumping power Wall plug power (100%) Mechanical pump (90% efficient) Pump inefficiency lost (5%) LM heating within pump (5%) System pressure drops result in LM heating (90%) Thermal energy recovered at  th (95% x  th ) HX blanket (mechanical pump example)

Next steps Refinements to various blanket formulas are needed, e.g.  Inclusion of manifolding  Revisit loss factors for bends and other perturbations  Separate treatment of inboard and outboard blankets  Better estimates of peaking factors  Proper accounting of heat transfer enhancement techniques  Design details (number of channels, channel size, …) Proceed to detailed point design studies of a SiC blanket and He- cooled W divertor for a tokamak  Need MHD formulas for SiC blanket Treat q” and NWL in blanket separately in pumping power eqn. Re-examine peak achievable conversion efficiency for SiC blanket Explore blanket He pumping with a turbine