1 General Aspects of High-Temperature Reactors .................... 1
1.1 Overview ................................................. 1
1.2 FutureSustainableEnergyTechnologies .......................... 2
1.3 PrincipleCharacteristicsofHTR ................................ 4
1.4 ApplicationofModularHTRintheEnergyEconomy ............... 8
1.5 SafetyAspectsofModularHTR ................................ 10
1.6 FuelCyclesofModularHTR .................................. 11
1.7 IntermediateandFinalStorage .............................. 13
1.8 OverviewontheHTR-PMProject .............................. 13
1.9 OverviewontheHTRDevelopmentuptoNow .................... 20
References ....................................................... 21
2 Physical Aspects of Core Layout .............................. 23
2.1 Overview on Physical Aspects of Core Layout and Design ofModularHTRPlants....................................... 23
2.2 SomeAspectsofCriticality................................. 27
2.3 In.uence of Re.ectors ....................................... 31
2.4 Coef.cientsofReactivity .................................. 33
2.4.1 PrincipleConsideration ............................... 33
2.4.2 Temperature Coef.cients.............................. 34
2.5 Demand of Reactivity Compensation and Worth of Control Systems .... 38
2.6 Fast Neutron Doses on Re.ectors ............................. 43
2.7 In.uenceofFlowofBalls,ActionontheBurnupofFuel ............ 46
2.8 Distributions of Fuel, Neutron Flux, and Power Density intheReactorCore .......................................... 52
2.9 PrinciplesofKineticsofNuclearReactors .................... 54
2.9.1 OverviewonSomeGeneralAspects ..................... 54
2.9.2 KineticEquations.................................... 58
2.9.3 Simple Solutions of the Kinetic Equations.... .... ..... .... 60
2.10 ProgramSystemsforPhysicalLayoutoftheCore .................. 61
2.10.1 GeneralRemarks .................................... 61
2.11 AspectsofCoreLayoutandDesign ............................. 67
2.11.1 General Overview and Aspects of Core and Fuel Element Design............................................ 67
2.11.2 Discussions on Different Core Parameter . .... .... ..... 69
2.12 Physical Aspect of the First Loading and Running in Period ofaPebbleCore ............................................ 74
2.13 DischargingofPebble-BedCores ............................... 80
References ....................................................... 80
3 Thermo-Hydraulic Aspects of Core Layout ......................... 83
3.1 HeatProductionInsidetheCore ................................ 83
3.2 ThermalPoweroftheCore.................................... 87
3.3 DataoftheCoolantGasHelium .......................... 88
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3.4 Basic Equations of the Thermo-Hydraulics of the Core . .... ..... .... 90
3.5 HeatingupofHeliumCoolantintheCore ........................ 94
3.6 Temperature Pro.lesinFuelElements ........................... 98
3.7 HeatTransferinthePebble-BedCore............................ 102
3.8 Pressure Drops in the Core and Re.ectorStructures ................. 104
3.9 Special Aspects of Thermo-Hydraulic Layout of the Core of Modular HTR..................................................... 107
3.9.1 MixingofHotGasBehindtheCore ..................... 107
3.9.2 In.uenceofBypassesontheCoreCooling ................ 110
3.9.3 Uncertainties of Calculation of Power Density and Other Thermo-HydraulicParameters .......................... 111
3.9.4 MeasurementofFuelTemperature....................... 112
3.9.5 c HeatingofCoreInternalsandCooling .................. 113
3.10 PrincipleofCoreLayout...................................... 114
3.11 Comparison of Data of Core Cooling in Some HTR Concepts ..... .... 117
3.12 Comparison of Thermo-Hydraulic Aspects of Different ReactorTypes .............................................. 118 References ....................................................... 119
4 Fuel Elements.................................................... 121
4.1 DescriptionoftheComponent ................................. 121
4.2 AspectsofLayoutandDesignofHTRFuelElements ............... 123
4.3 Temperature Distributions in HTR Fuel Elements.. .... .... ..... .... 128
4.4 IrradiationBehaviorofFuelElements............................ 130
4.5 StressesinFuelElements ..................................... 134
4.6 CorrosionofFuelElements.................................... 138
4.7 Fission Product Release from Fuel Elements in Normal Operation .. .... 141
4.8 DifferentTypesofSphericalFuelElements ....................... 150
4.9 Some Further Experiences with HTR Fuel Elements.... .... ..... .... 151
4.10 ComparisonofLWRandHTRFuelElements ..................... 157
References ....................................................... 161
5 Reactor Components .............................................. 163
5.1 OverviewontheComponents .................................. 164
5.2 InternalReactorStructures .................................... 165
5.2.1 OverviewontheComponents .......................... 165
5.2.2 TechnicalAspectsofCoreInternals...................... 165
5.2.3 LoadsonCoreInternals............................... 175
5.2.4 GraphiteandItsIrradiationBehavior ..................... 178
5.2.5 Results of Analysis of Re.ector Structures During Operation .......................................... 183
5.3 PrimaryEnclosure ........................................... 186
5.3.1 Overview .......................................... 186
5.3.2 Aspects of Dimensioning and Materials for Pressure VesselsofPrimaryCircuit ............................. 189
5.3.3 Neutron Irradiation of Reactor Pressure Vessel andDesignAspects .................................. 197
5.3.4 ActivationoftheReactorPressureVessel ................. 201
5.4 Comparison of Different Reactor Pressure Vessles . .... .... ..... .... 203
5.5 ShutdownandControlSystems................................. 203
5.5.1 OverviewonReactivityAspects ........................ 203
5.5.2 WorthesofShutdownSystemsinHTR ................... 206
5.5.3 Technical Concepts of Control and Shutdown Systems ... .... 208
5.6 FuelHandlingSystem ........................................ 217
Contents LLL
5.6.1 Overview .......................................... 217
5.6.2 Technical Aspects of the Fuel Handling System ... ..... .... 220
5.6.3 AlternativesfortheFuelHanding ....................... 226
5.6.4 SomeSpecialAspectsofFuelHandling .................. 231
5.7 Measurement Installations for Core Parameters .... .... .... ..... .... 233
5.7.1 MeasurementofNeutronFlux .......................... 233
5.7.2 Measurements of the Thermo-Hydraulic Parameters oftheCore......................................... 236 References ....................................................... 238
6 Components of the Helium Cycle .................................... 241
6.1 Overview ................................................. 241
6.2 HotGasDuct .............................................. 245
6.2.1 DescriptionoftheComponent .......................... 245
6.2.2 TechnicalAspects ................................... 250
6.3 SteamGenerator ............................................ 257
6.3.1 GeneralDescriptionoftheComponent ................... 257
6.3.2 Thermo-HydraulicAspects............................. 267
6.3.3 PressureDrops ...................................... 273
6.3.4 FlowStabilityoftheSteamGenerator .................... 276
6.3.5 Aspects of Mechanical Design of Steam Generator Tubes . .... 278
6.3.6 Experiences with Steam Generators of Gas-Cooled Reactors........................................... 283
6.4 HeliumCirculator ........................................... 290
6.4.1 Overview Some Thermosdynamic Aspects ... .... ..... .... 290
6.4.2 Aspects of Technology of Helium Circulators . .... ..... .... 296
6.4.3 ConceptsofHeliumCirculators ......................... 298
6.5 Gas Puri.cationPlant ........................................ 306
6.5.1 Overview .......................................... 306
6.5.2 Concept of the Gas Puri.cation......................... 311
6.5.3 Experiences with Gas Puri.cationPlants .................. 314
6.6 HeliumCircuitsforDecayHeatRemoval ......................... 316
6.7 HeliumAuxiliarySystems .................................... 320
6.7.1 Overview .......................................... 320
6.7.2 AuxiliaryHeliumCircuits ............................. 320
6.7.3 MeasurementsinHeliumCircuits ....................... 322
6.8 ReactorProtectionSystem .................................... 326
References ....................................................... 327
7 Reactor Containment Building ...................................... 331
7.1 GeneralRemarksandRequirements ............................. 331
7.2 Aspects of LWR and HTR Containments or Containment Buildings .... 334
7.3 Several Overview on Concepts of Reactor Containment Buildings forHTR .................................................. 336
7.4 Overview on HTR Containments and Buildings Applied Until Now .... 337
7.5 PlanningWorkfortheContainmentsinthePast.................... 339
References ....................................................... 345
8 Power Conversion Cycle ........................................... 347
8.1 OverviewonFlowSheet...................................... 347
8.2 SomeThermodynamicAspectsoftheSteamCycle ................. 348
8.3 AspectsofSteamTurbine ..................................... 354
8.4 CondensationandCoolingSystems ............................. 356
8.5 Feed Water Preheating System and Feed Water Pumps . .... ..... .... 365
8.6 OptimizationoftheSteamCycle ............................... 368
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8.7 PotentialofSteamCycles ..................................... 371
8.8 CogenerationProcessesUsingSteamCycle ....................... 376
References ....................................................... 380
9 Operational Aspects............................................... 381
9.1 Overview on Requirements and Conditions of Plant Operation..... .... 381
9.2 BurnupofFuelandProductionofHigherIsotopes.................. 384
9.2.1 BurnupofFuel ..................................... 384
9.2.2 ProductionofHigherIsotopes .......................... 387
9.3 FissionProductInventory ..................................... 388
9.4 DynamicalEquationsfortheTotalPlant.......................... 395
9.4.1 PrincipleOverview .................................. 395
9.4.2 SystemoftheDynamicalEquations...................... 395
9.4.3 Program Systems for Evaluation of Dynamical Questions . .... 400
9.5 ApplicationsoftheDynamicalEquations ......................... 402
9.6 ConceptofControlandOperationofaModularHTR ............... 405
9.6.1 ConceptofControl .................................. 405
9.6.2 OperationofHTR ................................... 407
9.7 Xenon Dynamics and In.uenceofSamariumonReactivity ........... 411
9.8 DecayHeatRemovalDuringNormalOperation .................... 418
9.8.1 DecayHeatProduction ............................... 418
9.8.2 PrinciplesofDecayHeatRemoval ...................... 419
9.8.3 Decay Heat Removal in a Modular HTR During Normal Operation .......................................... 421
9.9 Release of Radioactive Substances During Normal Operation. ..... .... 423
9.10 AspectsofWasteManagementinModularHTR ................... 426
References ....................................................... 433
10 Safety Aspects and Analysis of Accidents ............................. 435
10.1 GeneralRemarks............................................ 436
10.2 OverviewonRelevantAccidents ............................... 444
10.3 LossofCoolantAccidents .................................... 449
10.4 TotalFailureoftheActiveDecayHeatRemoval ................... 450
10.4.1 Decay Heat Production and Active Decay Heat Removal . .... 450
10.4.2 Overview Over Different Cases of Loss of Active Decay HeatRemoval ...................................... 453
10.4.3 Self-acting Decay Heat Removal Under Full Helium Pressure ........................................... 454
10.4.4 The Concept of Self-acting Decay Heat Removal from the Depressurized Reactor (Outer Surface Cooler Is Working) .... 456
10.4.5 Discussion of Parameters Relevant for the Concept ofSelf-actingDecayHeatRemoval ...................... 460
10.4.6 Self-acting Decay Heat Removal from the Reactor, Total Loss of Active Cooling of the Core, and Failure of the Surface Cooler............................................ 464
10.4.7 Change of Core Temperature in Accidents and Change ofStateofReactivity ................................. 466
10.4.8 Self-acting Decay Heat Removal in Extreme Accidents (ReactorCoveredbyRubble)........................... 468
10.5 ReactivityAccidents ......................................... 470
10.5.1 Overview .......................................... 470
10.5.2 Extreme Reactivity Accidents in Modular HTR .... ..... .... 470
10.5.3 Water Ingress into the Core, Change of the Moderation Ratio ............................................. 474
10.5.4 General Considerations on Reactivity Accidents ... ..... .... 475
Contents Y
10.6 WaterIngressintothePrimarySystem ........................... 477
10.6.1 Overview on General Aspects and Consequences oftheAccident ..................................... 477
10.6.2 Estimation of Water Ingressing into the Primary Circuit .. .... 478
10.6.3 Thermodynamic Equilibria for the Steam/Graphite Reactions .......................................... 479
10.6.4 Reaction Speed of Graphite Corrosion by Steam ... ..... .... 481
10.6.5 Some Technical Aspects of Water Ingress into a Hot PebbleBed......................................... 484
10.6.6 RiseinPressureinPrimaryCircuit ...................... 487
10.6.7 Gas Formation During Water Ingress into the Reactor.... .... 489
10.6.8 Reactivity Effects caused by Water Ingress ... .... ..... .... 493
10.6.9 ValuationofWaterIngressAccidents .................... 494
10.7 IngressofAirintothePrimaryCircuit ........................... 497
10.7.1 Overview on Aspects of Air Ingress Accidents .... ..... .... 497
10.7.2 Thermodynamic Equilibria of Reactions . .... .... ..... .... 498
10.7.3 Reaction Velocities of Air with Graphite . .... .... ..... .... 499
10.7.4 ConsequencesofAirIngressAccidents ................... 501
10.7.5 Principle Considerations on the Mass Flow of Air IngressingintothePrimarySystemofHTR ............... 501
10.7.6 Conclusions on Results of Analysis of Air Ingress Accidents .......................................... 506
10.7.7 Further Options to Reduce the Consequences of Air Ingress ............................................ 506
10.8 Accidents on the Secondary Side of the Steam Cycle ... .... ..... .... 507
10.8.1 Overview .......................................... 507
10.8.2 RuptureoftheMainSteamPipe ........................ 508
10.8.3 Failure of the Turbine-Generator System; Load Rejection ofTurbine ......................................... 509
10.9 ImpactsfromtheOutsideontheReactorPlant ..................... 512
10.9.1 OverviewonImpacts ................................. 512
10.9.2 AirplaneCrash ...................................... 514
10.9.3 Earthquakes ........................................ 519
10.10 ReleaseofFissionProductsDuringAccidents ..................... 521
10.10.1 Overview on Source Terms of Radioactivity .. .... ..... .... 521
10.10.2 Fission Product Release During Operation of the Plant Over the Entitle Lifetime (First Source Term) . .... ..... .... 525
10.10.3 Fission Product Release During Core Heatup Accidents (SecondSourceTerm) ................................ 531
10.10.4 Transport of the Released Radioactivity from the Core totheEnvironment .................................. 532
10.10.5 Radioactive Source Terms—Conclusions .................. 535
10.11 Radiological Consequences of Accidents and Risk . .... .... ..... .... 536
10.11.1 OverviewonConceptsofRisks......................... 536
10.11.2 ImportanceofLandContaminations ..................... 540
10.11.3 Dose Rates Caused by Accidents of Modular HTR . ..... .... 542
10.11.4 General Remark on Risks Caused by Nuclear Technologies ....................................... 546 References ....................................................... 549
11 Fuel Cycles and Waste Management ................................. 555
11.1 OverviewonFuelCycles ..................................... 555
11.2 FabricationofFuelElements................................... 562
11.3 IntermediateStorageofSpentFuelElements ...................... 568
YL Contents
11.4 AccidentsinIntermediateStorageSystemsforSpentFuel ElementsandDuringTransport................................. 580
11.5 FinalStorageofSpentFuelElements............................ 584
11.6 NonproliferationandSafeguardAspects.......................... 596
References....................................................... 605
12 Economic Aspects of Power Plants and Questions of Optimization ......... 607
12.1 OverviewonEconomicalConsiderations......................... 607
12.2 EquationforCalculationoftheCostofElectricity Generation................................................. 610
12.3 InvestmentCostsandCapitalFactors............................ 612
12.4 Ef.ciencyandFull-PowerHoursofOperation..................... 614
12.5 CostofFuelSupplyandWasteManagement...................... 615
12.6 TotalCostsofElectricityGeneration ............................ 620
12.7 ComparisonofProductionCostsofDifferentPower PlantsandSensitivityofCosts................................. 623
12.8 EscalationofCostsandMethodsofEvaluation .................... 626
12.9 ExternalCostsofElectricityProduction.......................... 627
12.10 InvestmentCostsofNewlyDevelopedConcepts ofNuclearPowerPlants...................................... 630 References....................................................... 634
