Inspection of the PuO2-UO2 fuel claddings and assembly parts for the Japan prototype heavy water reactor 'FUGEN'

The reactor core of the prototype advanced thermal reactor ''FUGEN'' is composed of 96 PuO2-UO2 fuel assemblies, 124 UO2 fuel assemblies and 4 special fuel assemblies. The outline of the fuel specifications are as follows; 1) The diameter and height of pellets 14.4 mm and 18 mm density 95%, uranium enrichment 1.5% U235, and plutonium enrichment 0.55% and 0.8% Pu fissile, respectively, 2) the effective length of fuel elements 3700 mm, the cladding tube material Zry-2, and the cladding tube dimensions OD 16.46 mm, ID 14.70 mm, 3) the number of fuel elements in one fuel assembly 28 rods, the full length of a fuel assembly 4388 mm, and the weight of fuel assembly 230 kg. Prior to fabricating the initial core fuel assembly, study was conducted on the quality assurance program for the fuel assembly production. The production and inspection of fuel assemblies were forwarded based on the quality assurance program. The inspection of the parts for fuel elements and assemblies started in July, 1974, and completed in March, 1978. The destructive and non-destructive methods were utilized for the inspection. The destructive inspection was conducted by random sampling, and the non-destructive inspection by the total or sampling inspection. Those data processing and banking were totally made with a FACOM M-160 computer. As for the cladding inspection, the chemical analysis, the mechanical property test. The corrosion test and the micrographical structure test were conducted as the destructive inspection, and the visual, dimensional and ultrasonic inspections were conducted as the non-destructive inspection. The inspection processes and the items of acceptance inspection for fuel elements and fuel assemblies are presented. Each inspection result is shown and evaluated. (Nakai, Y.)