CANES Center for Advanced Nuclear Energy Systems * A MITEI Low Carbon Energy Center* 77 MASSACHUSETTS AVE CAMBRIDGE MA 02139-4307 Closed Brayton Cycle Power for Pebble Bed Reactors Jim Kesseli, Brayton Energy, LLC Kesseli@BraytonEnergy.com January 30, 2017
Introductory Notes and Acknowledgements Notes from Prof. Jacopo Buongiorno: focus your talk on Helium Brayton, both the heat compact exchangers and the turbomachinery, with emphasis on readiness, performance, challenges, and importantly cost wrt steam cycle. Acknowledgements: Portions of this work was sponsored by X-energy (2010-2013) covering the early studies of the direct Brayton cycles. PBMR Inc sponsored Brayton Energy studies 2004-2008, for the development of an alternative recuperator. AREVA sponsored Brayton Energy studies of IHX for indirect cycles 2005-2007
Closed Cycle Brayton for Pebble Bed Reactors Heat rejection Pre-cooler Compressor Recuperator Generator Containment PEBBLE BED REACTOR Turbine Principles: Gas turbine (Brayton cycle) Working fluid: inert gas (He favored, non-radioactive release) Attractions: Simplicity: One major moving part No water or steam Simplified pressure boundary for coding AC power terminals Containment
Turbomachinery for closed He cycle - high stage count for He. (Pr~3) PM Alternator (12 MWe) Axial turbine (2-stage) 8-stage Axial Centrifugal Compressor Closed-cycle He working fluid Only one moving part No mechanical wear all magnetic bearings Shaft speed motor/alternator, for variable power control. 4
10MW Helium Cycle Turbo-Alternator Cost ~ $500/kWe Axial compressor diameter~ 400mm, centrifugal ~800mm ~600mm diameter turbine rotor State of Readiness: Conservative aero design loading Low stress Common low temp alloys High TRL Mag bearings PMA
Efficiency trades: Basic cycle ~30% thermal-electric Reactor inlet temp = 500ºC Reactor outlet temp = 850ºC Peak Pressure = 4 MPa He mass fraction = 15%, Ar mass fraction = 85% η-electric=0.30 η-electric=0.29 η-electric=0.28
Step 1- Brayton s cycle model for trade studies Step 2: Concepts NREC Agile Software for refined performance modeler, maps, and blade design for turbine and compressor Structural ANSYS Aero FEA 7
Brayton Turbomachinery Design Sequence - Readiness: Very Mature Aerodynamic 1. Cycle studies- Pr, N, η 2. 1-D geometry definition, based on nondimentional parameters (specific speed, head coefficient (defines speed and rough geometry, stage count) 3. Mean-line analysis: ηc, ηt, map prediction. 4. 2-D Blade geometry generator: stream-line coordinate methods. 5. 3-D full performance analysis and refinements Mechanical 1. Rotor-dynamic analysis (seals an bearings) 2. Cost analysis trade studies 3. AN 2 stress / creep life: scoping studies: material selection 4. Preliminary CAD modeling for polar characteristics for rotor dynamic analysis & bearing design. 5. Detailed FEA: Thermal structural analysis, blade dynamics 6. Final CAD manufacturing. 8
Current thinking: Blisk and fully machined first test articles Alloy MAR-M 247 Notes on turbine life Very low TIT (750 C), blade root temp <<700 C Due to low loading coefficient (best efficiency) low stress Therefore: No blade cooling Solid blades (vs cored) Generic alloys Blisks possible if size permits 9
Modular Pebble Bed Modular Reactor for X-energy 2010-2012 Cost at Production Level: Mass (kg) 10 500 108663 $10,595,296 $9,663,663 Normalized Cost $/kwe $1,060 $966 Item Mass (kg) Low Prod. Cost High Prod. Cost $/kg RECUPERATOR 5710 $579,626 $325,149 $102 TURBOMACHINERY 7824 $1,047,357 $864,711 $134 ALTERNATOR AND POWER ELECTRONICS 30833 $4,394,597 $4,141,464 $143 HEAT REJECTION TANKS 34395 $542,642 $362,940 $16 MAIN VESSEL & SUPPORTS 29901 $274,499 $259,362 $9 SYSTEM INSTALL 0 $74,775 $42,439 COOLING TOWERS 0 $3,550,000 $3,550,000 INVENTORY CONTROL SYSTEM 0 $131,800 $117,597 CONTROLS & INSTRUMENTATION TOTAL 108663 $10,595,296 $9,663,663 Closed cycle recuperated gas turbine (He) Almost half the cost was the alternator & bearings
CABLES AND WIRING $54,000 $51,022 ENCLOSURE $54,000 $51,022 Cost at Production Level: Mass (kg) 10 500 108663 $10,595,296 $9,663,663 Normalized Cost $/kwe $1,060 $966 Item Mass (kg) Low Prod. Cost High Prod. Cost RECUPERATOR 5710 $579,626 $325,149 RECUPERATOR CORE 3072 $523,155 $285,923 RECUPERATOR TIE ROD 208 $8,664 $4,870 RECUPERATOR CASE 838 $9,872 $7,948 HP EXHAUST MANIFOLD 1591 $37,935 $26,409 NO. CORES 18 TURBOMACHINERY 7824 $1,047,357 $864,711 TURBINE MODULE 3144 $253,132 $190,654 COMPRESSOR MODULE 2487 $200,167 $154,912 SHAFT UNIT 73 $8,100 $6,917 BEARING ASSEMBLY 36 $514,160 $457,585 SUPPORT AND MOUNTING 2084 $30,253 $24,333 FINAL ASSEMBLY 0 $41,545 $30,311 ALTERNATOR AND POWER ELECTRONICS 30833 $4,394,597 $4,141,464 ALTERNATOR 18636 $2,040,120 $1,927,620 MOUNTING 12196 $208,247 $185,966 POWER ELECTRONICS 0.00 $2,146,230 $2,027,878 UTILITY INTERFACE $540,000 $510,222 LOAD BANK $2,160,000 $2,040,889 CABLES AND WIRING $54,000 $51,022 ENCLOSURE $54,000 $51,022 HEAT REJECTION TANKS 34395 $542,642 $362,940 PRESSURE VESSEL 7251 $66,996 $25,078 INTERNAL FIN MODULE 15449 $239,313 $170,639 EXTERNAL FIN MODULE 10784 $221,332 $155,309 INSTALLATION 912 $15,000 $11,913 MAIN VESSEL & SUPPORTS 29901 $274,499 $259,362 VESSEL 24498 $247,920 $234,249 SUPPORT STRUCTURE 5403 $26,579 $25,114 SYSTEM INSTALL 0 $74,775 $42,439 FACTORY ASSEMBLY 0 $15,845 $8,743 RIGGING & TRANSPORT 0 $14,396 $9,124 ON SITE ASSEMBLY 0 $44,534 $24,572 COOLING TOWERS 0 $3,550,000 $3,550,000 DRY COOLING TOWERS & FANS $3,400,000 $3,400,000 COOLANT PUMPS $50,000 $50,000 PLUMBING $100,000 $100,000 INVENTORY CONTROL SYSTEM 0 $131,800 $117,597 COMPRESSOR 0 $105,000 $93,685 AFTERCOOLER 0 $1,200 $1,071 CONTROLS AND PIPING 0 $25,600 $22,841 CONTROLS & INSTRUMENTATION TOTAL 108663 $10,595,296 $9,663,663
IHX -2 Solenoid valve compressor Emergency by-pass circuit IHX -1 Safety bypass valve Brayton-sCO2 Combined Cycle PCS System Helium cycle turbine NHS boundary H3 H2 H4 C2 C1 SCO2 Recompression Cycle-Top Fan cooler Fan cooler Gen SCO2 Cycle-Bottom Economics highly leveraged by cycle efficiency Potentially 40 to 50% efficiency State of Readiness for sco2 cycles: low TRL Start heater H1 Helium CO2 Water/glycol Butterfly valve Gen H5 C4 C3 Gen 12
IHX -2 Solenoid valve compressor Emergency by-pass circuit IHX -1 Safety bypass valve Brayton-sCO2-ORC Combined Cycle PCS System Helium cycle turbine NHS boundary H3 C2 SCO2 Recompression Cycle-Top Fan cooler Economics highly leveraged by cycle efficiency H2 Gen C1 H4 Fan cooler SCO2 Cycle-Bottom Start heater H1 Helium CO2 Water/glycol Butterfly valve Gen H5 C4 C3 ORC Gen 13
Published SCO2 Efficiency Studies 55% 50% 45% MIT papers Aspen Case Study at & SNLA papers Efficiency 40% 35% 30% 25% 20% ASPEN Case Study Pressure Ratio = 4.17 Compressor polytropic eff = 0.84 Turbine polytropic eff = 0.88 Alternator efficiency = 0.96 Power Electronics (or gear ) efficiency or 0.97 Cooling system parasitic = 0.97 Heat Addition DP/P = 2% Recup HX eff = 0.90 300 400 500 600 700 800 900 Turbine Inlet Temp, C TIP 250 bar TOP, bar Efficiency Split Fraction Pressure Ratio 40 40.84% 0.196 6.25 45 42.39% 0.196 5.56 50 43.89% 0.196 5 55 45.29% 0.191 4.55 60 50.48% 0.326 4.17 65 49.77% 0.315 3.85 70 48.87% 0.288 3.57 75 47.96% 0.258 3.33 80 46.94% 0.206 3.13 85 46.05% 0.169 2.94 90 45.13% 0.098 2.78 95 43.62% 0.005 2.63 100 41.48% 0 2.5 14
Estimated cost for Combined Cycle PCU Higher vs basic direct cycle, but lowered full power plant cost Unit Number Mass (kg) 10 500 RECUPERATOR - TURBOMACHINERY 9,708 $880,235 $695,130 ALTERNATOR AND POWER ELECTRONICS 8,393 $1,319,321 $1,244,995 MAIN VESSEL & SUPPORTS 11,213 $102,937 $97,261 SYSTEM INSTALL - $74,775 $42,439 COOLING TOWERS (INSTALLED) - $4,167,391 $4,167,391 INVENTORY CONTROL SYSTEM - CONTROLS & INSTRUMENTATION - TOTAL PCS 29,314 $6,544,660 $6,247,216 SCO2 POWER MODULE (no heat addition or rejection HXs) $16,400,000 $11,480,000 INTERMEDIATE HEAT EXCHANGERS 19,320 $1,126,384 $957,426 TOTAL PCS 48,634 $24,071,044 $18,684,643 Power, MWe 15 15 Normalized cost $/kwe $ 1,592,000 $ 1,235,757 Actually just over 17MW-e Note: Budgetary costs for sco2 cycle based on rough engineering estimates and not substantiated by suppliers
PBMR: Direct Cycle He gas-cooled nuclear reactor (2002-2007) A Joint Venture between ESKOM and British Nuclear Fuels Corp./Westinghouse Corporation Brayton Energy was sponsored to develop a low cost, straintolerant recuperator 16
BRAYTON s PBMR Recuperator Recup cell - brazed We have worked on every aspect of the integrated PBMR recuperator package Recup- welded stack of cells BRAYTON Energy, LLC Shut-off Disk HP gas interface Recup core w/integral manifolds Factory assembled module, Recup module 3x6 m LP gas interface 17
Brayton Recuperator PBMR highlights Compact containment vessel diameter: 2.8 meters Factory install recup into Class-1 vessel Full factory acceptance test Vessel transport width suitable for highway truck, Arrives at PBMR power plant needing only external connections. No internal support structure ( cradle ) Recup cores supported from cool HP pipes Cumulative damage factor for PBMR maneuvers and full mission profile = 0.0 (infinite fatigue life) based on 12-mo. of ANSYS analysis Demonstrated hermetic pressure boundary and creep resistance exceeding 30-yr life (ongoing full-scale cell tests employing Larsen-Miller time extrapolation) Weight: HX core 29,000 kg (common 304 or 316 stainless) ½ to ⅓ of Heatric core Manufacturing plans for GEA, in Germiston So. Africa 18
Integration and assembly Preliminary layout and integration Review of specifications vs design - TBD 19
PBMR Recuperator Assembly Recup cores: 61 per row or module 4 modules totaling 244 cores High-pressure (HP) piping and toroidal ring manifolds delivers cool HP Annular module, 1 of 4) 5.3m This integration design requires no internal support structures, as the cores are suspended from the ring manifolds by their integral manifolds. 2.8m 20
Top of assembly co-axial HP duct per PBMR specification. Hot flex pipes tolerate differential growth and provide interface to central collector pipe HP gas in HP gas out HP gas in Interconnecting vertical distribution pipes connect feeder to ring manifolds (omitted for clarity) Cores hang from ring manifold on short rigid HP pipes transitioning to the integral core manifold pipes (50 mm dia,) Ring manifold 21
Core to core annular seal (keeps hot LP within the annulus and the cooler LP exit on the Class-1 vessel interior surface Class-1 pressure vessel bathed in LP out gas Hot LP gas enters co-axial pipe at bottom LP out LP in LP out Large (2.2m) bellows surrounds core modules on cool side, permitting the cores to move axially with the growth of the central hop HP pipe. This AISI316 bellows was quotes at a price of $5,000. 22
Coaxial HP duct as specified by PBMR insulation HP Flex piles on hot side 50 mm dia, 2mm wall thickness HP cool intake pipes support core weight LP Seals bridge core to core annulus. Insulation to fill between cores (omitted for clarity) 23
50 mm diameter HP flex pipes staggered. Insulation Compensating bellows and tie bar on cool 106 C HP side). 510 C LP gas in 24
Testing in Phase 1- Brayton addressed critical design and life issues 1. Manifold flow distribution measurement and model validation 2. Wavy fin and straight fin friction factor measurements 3. Brazed folded wire matrix pressure drop characterization vs. braze parameters 4. Rupture tests-coupons (at room temp, to qualify manufacturing processes) 5. Rupture tests cells (at room temp) 6. Long duration creep tests at peak PBMR temps 25
A battery of test performed for PBMR recuperator Manometer Bank Test specimen (52 folds, 100-mesh folded screen) Flow Meter Regenerative Blower Static pressure taps Suction port Cell Inlet Cell Outlet Rubber seal Rubber seal Header & manifold flow distribution measurements Ambient air in port Brazed high-density formed screen flow test Pressure control switches (Breadboard) Gas bottles (N2) P = 17MPa P = 41.3 MPa Test Section volume 1100x700x15 0mm High-temp high-pressure cell creep Microprocessor controller and safety monitor High pressure destructive tests for braze strength characterization 26
High Temp creep testing - full scale Recup cells (5 mm x 480 mm), integral manifold omitted for these tests Cells pressurized through capillary tubes with N2 Photo shows SN048 and SN056 in creep test rig Photos taken at approximately 600 hours @ 17.2 MPa, 510 C Two additional cells (S/N 83 and 85 were later installed at 24.2 MPa gas pressure. All four cells are still operating, each with over 2400hrs accumulated Brayton will maintain experiment to 8,000 hrs 27
Four samples past 2000-hour mark in early March 07 Test still in progress; Based on Larsen-Miller time-temp extrapolation of this data cells will easily meet 30- year creep requirement 500 450 MPa 400 350 300 250 200 150 100 50 0 ASME Code N-47-30, Section III, Div 1, ASME Boiler & Pressure Vessel Code, Creep Stress Rupture σ_f/a for SN79, S/N83 Yield,Special Metals F/A fin stress for pressure allowable σ_f/a for SN83, S/N85 510 C σ_f/a for SN048, SN056 (24.1 MPa gas pressure) PBMR spec, 30-year (17.2MPa) Design point, 30-years P=6MPa σ_f/a=29 MPa 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 Time, HRS 28
Explanation of creep life extrapolation The Larson-Miller theory of creep enables the extrapolation of metal failure data to different pressures, temperatures, and times. Applying the known theory to a sample failing at our design conditions of 262,800 hours, 510 C (783K) and 6MPa gas pressure (28 MPa fin tensile stress), enables the prediction of failures at other conditions. Since it is impractical to conduct a creep test at 6MPa, 510C and wait for 30 years to prove viability, Larson-Miller provides a means for predicting the relative pressure increase associated with shorter time intervals. Applying this theory for theses conditions is the basis for extrapolation shown on the previous slide. The reference line in red, emanating from the theoretical design point predicts shorter rupture times, at increasing pressures (or fin stress) for a comparable safety margin. A failure below this reference line indicates that the target conditions are unattainable. Operating above the reference line implies some measure of safety margin. 29
PBMR Recuperator cost model The design point for each Recuperator (2 each) Process $/Cell Parting sheets Materials 1.85 Parting Sheet processing 0.07 Braze materials 1.52 Braze application 1.13 Fin materials 3.47 Fin processing 1.60 Manifold Rings materials 1.01 Manifold Rings Processing 3.14 Cell Assembly 1.29 Braze processing (furnace charges) 1.59 Braze processing labor 2.09 Cell to core weld assembly 1.42 Total cell cost 20.17 Number of cells 80820 Total Factory Cost, $ 1,630,427 Price excludes tooling, and is appropriate for second full recup order. Based on material prices quoted in March 2007 from ZAPP rolling mill Labor rates based on US rate of $75/hr Primary inlet temperature, C 512.5 Primary inlet pressure, kpa 2977 Primary mass flow, kg/s 101.1 Secondary inlet temperature, C 108.5 Secondary inlet pressure, kpa 8927 Secondary mass flow, kg/s 95.54 Effectiveness 97.26% Pressure drop (sum dp/p) 1.00% Cycle pressure ratio 3.00 $, USD Weight, kg $/kg Recuperator core & tooling 1,630,427 29,000 56.22 Manifolds, flex pipe, bellows 199,384 11,846 16.83 Vessel, 2.8 m x 6 m Total, US$ 1,829,811 Power, electric, MW 120 from 400 MWthermal Inflation 2007-2016 1.16 US labor statistics Normalized cost, FY2016 Recup module, less $/kwe 17.69 vessel 2 each required The Recuperator represents a small fraction of the PBMR cost 30
Noble gas-cooled nuclear reactor Cost ~ 35 $/kwe Brayton turbomachinery and heat exchangers A Joint Venture between ESKOM and British Nuclear Fuels Corp./Westinghouse Corporation 31
BRAYTON performed preliminary design of the Intermediate Heat Exchanger IHX for AREVA/Framatome (2005/2006) 850 C IHX State of Readiness: High Costs: please call