High Temperature Materials

Transcription

1 High Temperature Materials Training Course on High Temperature Gas-cooled Reactor Technology October 19-23, Serpong, Indonesia Japan Atomic Energy Agency

2 High Temperature Materials in HTGR Graphite components - Core structure - Core support structure Metallic material - RPV - IHX Heat transfer tube - Coaxial piping p.2

3 Graphite Components Fuel channel Fuel pin PGX IG-110 BP insertion hole Graphite block IG-110 PGX IG-110 PGX ASR-0RB Fuel element CR guide hole Block handling hole RSS hole Dowel pin Graphite block J. Sumita et al., NED, 233, (2004). CR guide block p.3

4 Graphite Components PGX IG-110 IG-110 PGX IG-110 PGX ASR-0RB J. Sumita et al., NED, 233, (2004). p.4

5 Graphite in HTTR Grade Bulk density (g/cm 3 ) Tensile strength (MPa) Compressive strength (MPa) Young s modulus (GPa) Thermal conductivity at 673K (W/m/K) Coefficient of thermal expansion at K(10-6 /K) JAEA s HTTR (IG-110) IG-110 (Moderator) IG-110 PGX (reflector) PGX Chinese reactors HTR-10 (IG-11) HTR-PM(IG-110) 2.3mm 2.3mm p.5

6 Manufacturing Process of Graphite Period of manufacturing process : about 6 months Coke/Coal tar pitch Pulverizing & Mixing Kneading Pulverizing & Sieving Isostatic pressing Chemical processing Machining Graphitizing Baking Purification Pitch impregnation Rough machining Inspection p.6

7 Requirements for Graphite Requirement properties for graphite are different depending on its role. Moderator Isotropic, homogeneous, high density Amount of impurity, dimensional change, thermal conductivity, thermal expansion, young s modulus, irradiation creep Neutron absorber Stability for irradiation (dimensional change, thermal expansion, etc.) Insulator Thermal conductivity and dimensional stability under high stress Fuel coating, sleeve High strength and irradiation stability due to severe irradiation condition (high fluence and temperature) The same properties are required as moderator Reflector The same properties are required as moderator. Strength degradation by thermal oxidation Irradiation effect is not important due to low neutron fluence. p.7

8 Integrity Assurance Approach Database Design Manufacturing Inspection Design data including irradiation effect Proof test Structural design code Inspection standards QA/QC management JAERI-M JAERI-M Pre-service inspection In-service In-service inspection method JAERI-Tech JAEA-Data/Code First fuel loading Inspection by TV camera A special committee at Atomic Energy Society in Japan established a draft of standard for graphite core components in HTGR (JAEA-Research ). In-service inspection Reactor not in operation Surveillance test Inspection by TV camera Reactor in operation Monitoring of regional temperature distribution p.8

9 Irradiation Effect on Graphite It is important for graphite structure of HTGR to have structure stability with the stand points of its lifetime. During the neutron irradiation, gradient of temperature and neutron flux case the local stress and residual stress. Irradiation induced stresses are determined by property change of graphite. Dimensional change Young s modulus Change in thermal expansion Change in thermal conductivity Change in creep strain At the beginning of irradiation, the young s modulus is increases because the defects produced by irradiation fix the movement of dislocation (pinning effect) Young s modulus keep increase due to deceasing pores in graphite by dimensional change. Thermal conductivity of graphite is dominated by phonon. Irradiation defects make mean free path of graphite and thermal conductivity shows small. A decrease rate of thermal conductivity at high irradiation temperature is small due to annealing effect. p.9

10 Dimensional Change by Irradiation Dimensional 寸法変化率 Change(%) (%) 3 2 Lifetime as graphite components USA(H-451) Germany(ATR-2E) IG Fast Neutron 高速中性子照射量 Fluence(x10 26 n/m 2,E>0.1Mev) With increasing the neutron fluence, the dimensional change decreases. The dimensional change shrinks maximum at the one fluence point, called turn around, then the dimensional change increase with increasing the fluence. The dimension and fluence of turn around depend on irradiation temperature, raw material and micro texture. Isostatic graphite with micro texture shows stable dimensional change. p.10

11 Elastic Modulus Change by Irradiation At the initial stage of the irradiation, the modulus is rapidly increased by the pinning effect of dislocations in graphite crystals. In latter stage of the irradiation, the modulus is gradually increased by the irradiationinduced dimensional shrinkage, i.e. the decrease of porosity of graphite. GA, DOE-HTGR (1991). p.11

12 Thermal Expansion Change by Irradiation The mean coefficient of thermal expansion is increased at the initial stage of the irradiation and is decreased by the irradiation. GA, DOE-HTGR (1991). p.12

13 Thermal Conductivity Change by Irradiation The conductivity rapidly decrease by the initial stage of the irradiation because irradiation-induced defects reduces mean free path of phonon, which dominates the thermal conductivity of graphite. The lower irradiation temperature gives the greater decrease in the conductivity because that high-temperature irradiation causes annealing recovery of irradiationinduced defects during the irradiation. ORNL, ORNL/TM-2011/378 (2011). p.13

14 Advantage of IG-110 Graphite (1/2) Fig. Weibull plots for tensile strength (IG-110 graphite and Coarse grain graphite) As you can see the difference of the line slope. The IG-110 graphite shows less scattering performance on the tensile strength test results. T.S.Byun, Statistical Characteristics of Facture Strength and Toughness of Nuclear Graphite,INGSM-10 p.14

15 Advantage of IG-110 Graphite (2/2) Fig. Example of calculated residual stress for graphite blocks during HTTR operation and limit of stress The first loaded IG-110 graphite in HTTR had excellent strength properties and small variation. Then graphite blocks had enough safety margins to the stress limits. Therefore, it was verified that the IG-110 is the high quality graphite regulated by graphite design. Reference: Jyunya SUMITA, Characteristics of First Loaded IG-110 Graphite in HTTR Core, JAEA-Technology p.15

16 Metallic Materials in HTTR Material Components Material Product form Service conditions Design temperature Design pressure* Maximum allowable temperature Reactor pressure vessel 440 o C 4.8 MPa 2 1/4Cr-1Mo steel Plate, forging, Pipe Shells of intermediate heat exchanger, primary pressurized water cooler, etc. 430 o C 4.8 MPa 550 o C Outside pipe of concentric double pipe 430 o C 4.8 MPa Hastelloy XR Tube, plate, forging Intermediate heat exchanger heat transfer tubes Intermediate heat exchanger hot header 955 o C 0.29MPa 940 o C 0.29MPa 1000 SUS321 Tube Primary pressurized water cooler heat transfer tubes 380 o C 4.8 MPa 650 o C SUS316 Bar Core restraint mechanism 450 o C o C 1Cr-0.5Mo-V steel Forging Core restraint mechanism 450 o C o C *: absolute pressure, Note: Control rod sleeves are made of Alloy 800H, whose maximum allowable temperature at a scram is 900. p.16

17 Design Approach for High Temperature Component Max. Allowable stress (MPa) 最大許容応力強さ (MPa) ¼ Cr-Mo SUS316 SUS321 ハステロイXR: HTGR 用耐熱機器 ( 圧力容器内管 IHX 伝熱管他 ) SUS 321: HTGR 用冷却器伝熱管 2 1/4Cr 1Mo: HTGR 用圧力容器もんじゅ用蒸発器 SUS 316: 一般工業用 Hastelloy XR Temperature 温度 ( )( o C) Outer tube (2 1/4 Cr-1Mo) Insulator 低温ヘリウムガス (400 ) He (400 o C) Inner tube (2 1/4 Cr-1Mo) Insulator He (900 o C) Liner (Hastelloy XR) Temperature limitation for metallic material is approx. 800 o C. Cooling is required to use in high temperature condition above 800 o C. Hastelloy XR is used with limiting pressure load or temperature by keeping the difference between internal and external pressure or utilizing insulation. p.17

18 Design Approach for RPV Cooling Standpipe Recuperator Turbine Compressor Control rod guide tube Upper shroud Precooler Reactor Generator RPV Hot plenum block Core barrel Core support plate From Recuperator Conventional RPV steel can be deployable with the intrinsic cooling scheme 588 o C 6.95 MPa From Compressor 136 o C 7.0 MPa RPV temperature < 350 o C X. Yan, et al., Nucl. Eng. Des.,, 226, (2003). p.18

19 Operating Temperature in HTTR IHX Intermediate heat exchanger Type Heat transfer rate Design pressure Design temperature Vertical helically-coiled counter-flow heat exchanger 10 MW 4.8 MPa (shell) 0.3 MPa (tube) 430 C (shell) 955 C (tube) Shell Outer diameter Overall height 2 m 11.0 m Tube Number 96 Outer diameter Thickness Material 31.8 mm 3.5 mm 2.25Cr-1Mo steel (shell) Hastelloy XR (tube) T. Furusawa et al., Nucl. Eng. Des., (2004). p.19

20 Hastelloy XR Development Hastelloy XR was developed based on Hastelloy X in conjunction with Mitsubishi Material Co. Manganese and Silicon contents are optimized to form stable and adherent oxidation films Cobalt content is optimized to reduce radioactive contamination in primary cooling system Aluminum and Titan content is optimized to suppress internal oxidation and intergranular attack Boron content is limited up to 100 ppm in weight in the standard specification. Within the range, increasing Boron content introduces significant improvement of creep resistance Cross-sectional Views after Corrosion Test (1000 o C, 10,000 hrs, in impure helium gas) 50μm Hastelloy XR Hastelloy X p.20

21 Advanced Material for Commercial HTGR Structure Reactor pressure vessel Core structural material HTTR 2 1/4Cr-1Mo IG-110 and PGX Material GTHTR300 SA533, SA508 (Mn-Mo) IG110 and IG11 Core barrel - Alloy 800H Core restraint mechanism 1Cr-0.5Mo-V and SUS316 C/C composite Control rod Alloy 800H C/C composite IHX heat transfer tubes Hastelloy XR Hastelloy XR Turbine rotor blade - Ni superalloy p.21

22 C/C Composite R&D Concept of control rod element Control rod sheath: C/C composite(fabrication) Connecting rod: C/C, SiC/SiC composite (oxidation resistance, strength) Conditions Temperature : <1500C Neutron fluence : - 2dpa Coolant :Helium gas with small amount of impurities Max. weight : 250kg Mock up with C/C composite (CX-270G, Toyo Tanso) For the design of the ceramic components of VHTR it is important to investigate, Irradiation behavior Oxidation behavior of the mechanical/thermal properties p.22