No abstract

No abstract

No abstract

This paper was prepared for the 1991 Kroll Award. A review is presented of the development of barrier fuel. It includes the recognition of the pellet-cladding interaction (PCI) fuel failure mode and of a coordinated program to develop understanding, mitigating strategies, and a fuel that is resistant to this failure mode. The efforts to understand PCI led to the conclusion that the dominant mechanism is stress-corrosion cracking of the Zircaloy. The invention and development of zirconium-barrier fuel was intended to provide a materials solution to this fuel failure mode. This review includes the work to understand the failure mechanism as well as the program to develop PCI-resistant fuel designs. Ultimately, the zirconium-barrier fuel was tested in power ramps to ascertain and to quantify the resistance to PCI under expected service conditions in commercial boiling water reactors (BWRs). The program that led to a large-scale demonstration in a commercial power plant (Quad Cities-2) is described briefly. Subsequent to that, program work continued with in-reactor load following and experiments in a test reactor on power cycling of barrier fuel. Finally, the performance of failed fuel is discussed briefly.

TASK f. NUCLEAR DESIGN AND CORE MANAGEMENT 2-1 2.1 Objectives 2-1 2.2 Introduction 2-1 2.3 Special Barrier Bundle Design 2-1 2.4 Energy Utilization Plan (EUP) 2-4 2.5 Fuel Cycle Comparison 2-5 2.6 Power Ramp Simulation 2-6 2.7 Cycle 6 Thermal Limits Calculations 2-7 2.8 Safety and Transient Analyses 2-11 2.9 Summary 2-11 2.10 GEAP-25163-3 TABLES Table Title Pag® 2.4-1 Energy Utilization Plan 2-4 2.4-2 Demonstration Loading Strategy 2-4 2.5-1 Fuel Cycle Comparison 2-5 2.5-2 Discharge Data, Discharge Exposure and Energy Produced by Discharge Batch 2-6 2.6-1 Estimated Peak LHGRs During Ramps 2-6 3.2-1 Weight Gain Data of Samples Tested in the Simulator at 350 and 400''C 3-2 3.2-2 Average Thicknesses of the Unirradiated Specimens Measured at the Undeformed and Deformed Regions 3-8 3.2-3 Average Thickness of the Irradiated Specimens Measured at the Undeformed and Deformed Regions 3-12 3.2-4 Summary of Expanding Mandrel Constant Extension Rate Tests for EBR-ll-1 and 2 Irradiated Reference and Barrier Modified Clad Tested in Flowing Iodine at 4 = 5 X 10-''min-^and337*'C 3-15 3.2-5 Summary of Expanding Mandrel Ramp and Hold Tests for EBR-II and Millstone Irradiated Reference and Barrier Modified Clad Tested in Flowing Iodine at 337''C 3-16 3.4-1 SRP Irradiation Status 3-31 3.4-2 Description of Fuel Rods to be Tested in 1980 3-32 3.4-3 1980 Ramp Test Matrix 3-39 3.4-4 Rods Selected for Destructive Examination 3-45 3.4-5 Fission Gas Analyses for Three Sound Rods 3-45 3.4-6 Summary of Fission Gas Release Fractions and Grain Growth Data from Ramp Tested Rods 3-46 3.4-7 Burnup Analyses for Three Sound Rods 3-47 3.4-8 Comparison of Calculated and Measured Burnups 3-47 3.4-9 Zirconium Liner Microcracking Versus Localized Diametral Cladding Strain 3-49 3.4-10 Zr-Liner Cladding Corrosion and Hydrogen Pickup 3-49 3.4-11 Water Sample Activity Analysis ~ Data Summary 3-64 3.4-12 Release Fractions-1st Cycle 3-73 v/vi GEAP-25163-3 ILLUSTRATIONS Figure Title Page 2.3-1 Special Barrier Bundle Design 2-3 2.7-1 Maximum Linear Heat Generation Rate (MLHGR) Cycle 6 Exposure 2-8 2.7-2 Minimum Critical Power Ratio (MCPR) Cycle 6 Exposure 2-9 2.7-3 Maximum Ratioed Average Planar Heat Generation Rate (MRAPLHGR) Cycle 6 Exposure 2-10 3.2-1 Corrosion Weight Gains for Zr-Liner Cladding and Reference Zircaloy-2 as a Function of Time at 350°C and 400°C in 7.0 MPa (1000 psig) Steam in the Simulator 3-3 3.2-2 Unirradiated Specimen as Bent and Sectioned Metailographically. Plane of Section is Parallel to the Original Tube Axis and Normal Tube Bend Axis 3-5 3.2-3 Photomicrograph at Region of Maximum Deformation (at O in Figure 3.2-2). No Separation Was Found at the Interface of Zirconium-Zircaloy 3-6 3.2-4 Microstructure at the Mid-Wall of the Zircaloy. Hydride Particles are Indicated by Arrowheads. Twinning is Shown by Arrows 3-7 3.2-5 Irradiated Specimens as Bent 3-8 3.2-6 Photomicrograph of Irradiated Specimen at the Undeformed Region 3-9 3.2-7 Irradiated Bent Specimen at the Most Severely Deformed Region (Marked O in Figure 3.2-5) 3-10 3.2-8 Irradiat...