Westinghouse Advanced Doped Pellet Characteristics and Irradiation behaviour

Transcription

1 Westinghouse Advanced Doped Pellet Characteristics and Irradiation behaviour Karin Backman 1, Lars Hallstadius 1 and Gunnar Rönnberg 2 1. Westinghouse Electric Sweden, 2. OKG AB Sweden IAEA - Technical Meeting on Advanced Fuel Pellet Materials and Fuel Rod Designs for Water Cooled Reactors November 2009, PSI, Villigen, Switzerland 1

2 Contents ADOPT overview Properties that will be discussed Density Fission gas release PCI performance Secondary degradation behavior Conclusion ADOPT = Advanced Doped Pellet Technology 2 Westinghouse Proprietary Information Class 2

3 ADOPT Overview High density UO 2 pellets with enlarged grain size. ADOPT contains additives of Cr- and Al-oxide less than 1000 ppm total Improved quality: the additives facilitate pellet densification during sintering and are experienced to give a lower rejection rate in the visual inspection after grinding 3 Westinghouse Proprietary Information Class 2 Standard pellet Grain size 9 μm Density 10.60g/cm % of TD ADOPT pellet Grain size 31 μm Density 10.67g/cm % of TD

4 ADOPT Overview Verification An extensive test program performed High BU irradiation on-going Experience 10 years of experience from irradiation Two full reloads in operation 4 Westinghouse Proprietary Information Class 2

5 ADOPT Overview Density Manufactured density mainly influenced by Cr 2 O 3 content. Grain size Strongly influenced by both Al 2 O 3 and Cr 2 O 3 content 5 Westinghouse Proprietary Information Class 2

6 Physical Properties Properties characterized Thermal Diffusivity Specific Heat Thermal Expansion Melting Temperature The difference between ADOPT and Standard UO 2 is negligible (within the uncertainty of accurate measurements) 6 Westinghouse Proprietary Information Class 2

7 Densification and swelling behaviour 7 Westinghouse Proprietary Information Class 2

8 Densification and swelling Resinter tests ,000 0,010 0,020 0,060 0,070 0,080 0,090 0,100 0,030 0,040 0,050 0,110 0,120 0,130 0,140 0,150 ADOPT, density 10.67g/cm3 8 Westinghouse Proprietary Information Class 2 Densification [g/cm 3 ] No of observations 0.13% ±0.13%, From 18 pellet lots Standard UO 2, density 10.60g/cm3 0.60% ±0.40%, From 65 pellet lots ,000 0,010 0,020 0,060 0,070 0,080 0,090 0,100 0,030 0,040 0,050 0,110 0,120 0,130 0,140 0,150 Densification [g/cm 3 ] No of observations

9 Fuel rod growth Less fuel densification of ADOPT pellets implies earlier pellet cladding contact resulting in a higher rod length increase. Same swell rate after densification ADOPT Rod Length Grow After pellet cladding contact occurs the rod length growth rate is the same. Rod Growth [% UO2 UO2 Database Burnup [MWd/kgU] 9 Westinghouse Proprietary Information Class 2

10 10 Westinghouse Proprietary Information Class 2 Fission Gas Release

11 FGR Gamma measurements at Oskarshamn Measurements on 22 fuel rods from 2 FA 10 with ADOPT-pellets 12 with standard pellets 2,5 Standard Fission Gas Release [%] 2 1,5 1 0,5 Adopt Preliminary Data Calculated Burnup [MWd/kgU] Around 30 % benefit of ADOPT consistent with Studsvik enhanced power data 11 Westinghouse Proprietary Information Class 2

12 FGR Studsvik data Relative FGR (%) Standard UO 2 ADOPT RAMP TEST 57kW/m 30.2% 17.2% BUMP TEST 45kW/m 29.7% 20.5% Significantly less gas release from the ADOPT fuel 12 Westinghouse Proprietary Information Class 2

13 FGR PIE after ramp test Standard pellets have pores precipitated mainly in the grain boundary. The doped pellet have the pores precipitated mainly inside the grain. This is beneficial to FGR. Standard segment (r = 2,2mm from center) Doped segment (r = 2,0mm from center) 13 Westinghouse Proprietary Information Class 2

14 Halden Test FGR Estimates from Normalized Rod Pressures ADOPT rods switch at 15 MWd/kgOx 200C temp jump initiates gas release from ADOPT rod 1 Std UO 2 ADOPT The rods were operated above the Vitanza FGR threshold The timing of the FGR release are linked to big steps in temperature The FGR release from the different rods are not comparable due to the completely different power histories they have experienced 14 Westinghouse Proprietary Information Class 2

15 Halden test Results from PIE Rod 1 ADOPT Rod 5 ADOPT Rod 6 Standard UO 2 The PIE examinations show results which is consistent with earlier ADOPT experience 15 Westinghouse Proprietary Information Class 2

16 16 Westinghouse Proprietary Information Class 2 PCI performance

17 PCI performance PIE following ramp tests Standard Doped 17 Westinghouse Proprietary Information Class 2

18 PCI performance PIE following ramp tests Standard UO 2 Doped 18 Westinghouse Proprietary Information Class 2

19 Pellet creep Constant Stress Creep test 1500 C 45 MPa 5 Strain (%) ADOPT creep rate = 0.5 %/h UO 2 creep rate = 0.4 %/h Time (h) A higher creep rate indicate a more viscoplastic behavior of the ADOPT pellet compared to the standard pellet 19 Westinghouse Proprietary Information Class 2

20 Resistance to secondary degradation 20 Westinghouse Proprietary Information Class 2

21 Secondary degradation Oxidation resistance test Oxidation curves, 400 o C, 20h, Ar/H 2 O 0.18 Weigth increase (%) Time (h) Pure UO 2 UO 2 +Cr 2 O 3 ADOPT Thermal microbalance test shows that ADOPT has improved resistance to fuel oxidation 21 Westinghouse Proprietary Information Class 2

22 Secondary degradation Inreactor washout test BWR rod with a large secondary defect Standard UO 2 pellet after inreactor washout test Studsvik inreactor test show less washout caused by erosion and or surface boiling of higher density pellets i.e. ADOPT 22 Westinghouse Proprietary Information Class 2

23 Conclusions Experience with ADOPT 10 years of experience including two full reloads An extensive test program Improved properties Higher density Reduced FGR Improved creep (PCI performance) Secondary degradation behavior in and out of pile test 23 Westinghouse Proprietary Information Class 2

24 24 Westinghouse Proprietary Information Class 2 Thank You!