Module 09 High Temperature Gas Cooled Reactors (HTR)

Transcription

1 c Module 09 High Temperature Gas Cooled Reactors (HTR) Prof.Dr. H. Böck Vienna University of Technology /Austria Atominstitute Stadionallee 2, 1020 Vienna, Austria

2 Development of Helium Reactor Technology From 1963 to 1989 DRAGON (U.K.) AVR (FRG) PEACH BOTTOM 1 (U.S.A.) FORT ST. VRAIN (U.S.A.) THTR (FRG)

3 Technical Background 1 For higher thermal efficiency higher gas temperatures up to 1000ºC are necessary CO 2 gas temperature is limited to 800ºC then it disintegrates into C and O Only stable gas with good nuclear and thermal properties is Helium No activation Chemically inert High specific heat Stable to high temperatures

4 Technical Background 2 For HTR no metallic fuel cladding possible Only solution is high density graphite Low neutron absorption Minimal radiation damage Superb heat resistance High thermal conductivity Therefore development of new fuel types - coated particles embedded in graphite Two major lines: 1. Graphite fuel spheres (pebbles): German version 2. Graphite prismatic fuel assemblies: US version

5 Advantages of HTR High efficiency: 47% Possibility of U-233 breeding from Th-232 Excellent passive safety features Strong negative temperature coefficient Excellent fission product retention Simple design Economically attractive Burn-up of MWd/ton

6 International Activities 1 Germany: 15 MW e AVR operated first HTR from 1966 to 1988, followed by 300 MW e Thorium-Hochtemperaturreaktor THTR (Pebble Bed Reactor) operated between 1983 to 1988 German development was stopped recently, but German industry cooperates with South Africa, China, Indonesia and Russia on modular units of Pebble Bed Modular Reactors (PBMR)

7 International Activities 2 South Africa plans 165 MW th PBMR between China operates a 10 MW th prototype PBMR, critical since 2000 Japan works on a 40 MW th PBMR with prismatic fuel assemblies Russia plans a 330 MW e Pu Burner with prismatic fuel assemblies for 2007

8 Modular High Temperature Pebble Bed Reactor (MPBR) 360,000 pebbles in core About 3,000 pebbles handled by fuel handling system each day About 350 discharged daily One pebble discharged every 30 seconds Average pebble cycles through core 15 times Burn-up of MWd/t Fuel handling most maintenance-intensive part

9 Typical PBMR Technical Data 110 MW e Helium Cooled Indirect Cycle 8% Enriched Fuel Built in 2 Years Factory Built Site Assembled On-line Refueling Modules added to meet demand - no Reprocessing High Burn-up >90,000 MWd/t Direct Disposal of High Level Waste

10 PBMR Fuel Spheres Fuel particles (kernels) consist of uranium dioxide Coated particles embedded in a spherical graphite matrix, 50 mm diameter 5 mm thick fuel-free outer graphite zone, overall outer sphere diameter 60 mm One fuel sphere contains approximately coated particles fuel spheres are required for a single core loading

11 Fuel Sphere Production 1 Solution containing 8% enriched uranium is cast to form microspheres. These are washed, calcined and sintered at high temperature to produce uranium dioxide kernels Kernels are then put in a Chemical Vapour Deposition furnace at a temperature above 1000ºC in which the pyrolytic carbon coating layers are added with extreme precision by cracking CH 4 into C+H SiC-layers have different densities: -one inner layer low density to capture volatile fission products, -two outer layers with high density

12 Fuel Sphere Production 2 Carbon densities can be adjusted by cracking temperature and exposure time The coated particles with about a millimeter in diameter are mixed with a resin and graphite powder and pressed into 50mm diameter spheres A 5mm thick layer of fuel free graphite powder is then added to form the "fuel-free" outer zone. The resulting spheres are then machined, cabonized and annealed

13 Construction of Graphite Spheres

14 Ceramic Coated Fuel Particles

15 Microcut through Fuel Kernel

16 TRISO Fuel Particle (Kernels) Microsphere 0.9 mm diameter ~11,000 particles in every pebble Fission products retained inside microsphere TRISO acts as a pressure vessel (= first and second barrier) Reliability Defective coatings during manufacture ~1 defect in particles

17 TRISO Fuel Particle Microsphere Pyrolytic carbon: Material similar to graphite with some covalent bonding between it layers Produced by heating CH 4 nearly to its breakdown temperature and permitting the graphite to crystallise on the UO 2 kernels

18 HTR Module

19 Cross Section of the German 300 MW e THTR Core operating from 1983 to 1988

20 Reactor Building of China s HTR-10

21 Core of HTR-10

22 Chinese Pebble Bed-HTR PM 200 MWe demonstration unit at Weihei/Shandong province Later 18 modules of full-scale power Project costs US 375 M$ Start-up in fuel elements, 9% enriched Low power density but high temperature 900 C 60 years life time, 85% availability First of 18 modules

23 Mock-up of Chinese HTR-Plant (3600 MW e ) in Shangdon

24 HTR-10 ATW 12/ decision to construct HTR construction started after safety review December 2000 first criticality January 2003 full power operation Excellent operation recod Used for reactor safety experiments during normal and abnormal operation

25 Operational Data of the HTR-10 ATW 12/2006 Design Operation Nuclear power [MW] Electric power [MW] Helium inlet temperature [ 0 C] Helium outlet temperature [ 0 C] Helium pressure [MPa] 3 3 Feed water temperature [ 0 C] Steam temperature [ 0 C] Feed water flow [kg/s] ,57 Steam pressure [MPa] Fuel number [-] 13,622 Graphite spheres number [-] 16,387

26 Parameters of the HTR_Pebble Bed Module (HTR-PM) ATW 12/2006 Reactor thermal power [MW] Electric power [MW] 458 MW 195 MW Fuel number at equilibrium core [-] 520,00 Core Heigh/out diameter/inner diameter [m] 11/ 4 / 2.2 Helium pressure [MPa] 9 Helium flow rate [kg/s] 176 Helium temperature inlet/outlet [ 0 C] 250/750 Steam flow rate [t/h] Steam temperature [ 0 C] 538 Steam temperature [MPa] 13.5

27 Passive Safety Feature in Case of LOCA Design Goal = 1600 C Fuel Temperature ( C) Pressurized Depressurized To Ground Time After Initiation (Days) Fuel temperatures remain below design limits even during loss of cooling

28 Major Advantages of GasTurbine (GT)-HTR SAFETY: GT-HTR is meltdown-proof and passively safe PROLIFERATION/TERRORIST RESISTANCE: High proliferation resistance due to low fuel inventories in GT-MHR fuel elements (fresh and spent) Below grade silo resistant to sabotage SPENT FUEL MANAGEMENT: TRISO coating provides excellent barrier for containment of radionuclides for geologic times LOW ENVIRONMENTAL IMPACT: High thermal conversion efficiency and high fuel burnup reduce environmental impacts ECONOMIC COMPETITIVENESS: Projectioned generation costs are lower than any other generation alternative

29 References