Design Study of Innovative Simplified Small Pebble Bed Reactor

Transcription

1 Design Study of Innovative Simplified Small Pebble Bed Reactor Dwi IRWANTO 1), Toru OBARA 2) 1) Department of Nuclear Engineering, Tokyo Institute of Technology 2) Research Laboratory for Nuclear Reactor, Tokyo Institute of Technology

2 Outline Introduction Research Purposes Calculation Procedures Parametric Survey Reference Design Conclusions page 2 of 13

3 Introduction Peu a Peu Fuel Loading Scheme Pebble Peu a Bed PeuReactor fuel loading concept proposed by E.Teuchert et al (1992) Pebble bed reactor based design with fuel unloading devices is removed The reactor core subdivided into several fuelling zones Startup lower layers filled first criticality During operation layer per layer filled maintain criticality The end of the core unloaded fuel (Potential) Problem? The unloading machinery is a very complex and high cost system page 3 of 13

4 Research Purposes To find a means of carrying out the exact calculations needed to analyze the Peu à Peu fuel-loading scheme Optimize the fuel design by perfoming parametric survey in the infinite geometry Calculate a whole core design by using the optimized fuel design page 4 of 13

5 Development of a Code for Automate Process of Peu a Peu Fuel Loading Scheme

6 Calculation Procedures Some studies have been performed previously, they have used a diffusion-based method but the large empty cavity region in the core, makes accurate calculations is difficult to performed The Monte Carlo method is used to perform calculations with high accuracy at the top region of the core near the large cavity Unfortunately, the calculation procedures for the Peu à Peu modus using the Monte Carlo method require lot of steps Therefore, a computer code to automate the process of the Peu à Peu fuel load scheme has been developed using Fortran-77 and based on the Monte Carlo MVP/MVP-BURN code page 5 of 13

7 Development of a Code for Automate Process of Peu a Peu Fuel Loading Scheme Motivation Time needed to prepare the input files, calculate it and sequentially do all the process is very huge Huge number of nuclear materials data to edit and/or add to the input files In order to avoid mistakes in preparing the input This code significantly reduce time needed to perform the calculation process of the Peu a Peu fuel load scheme page 6 of 13

8 Parametric Survey

9 Parametric Survey Parametric Survey 235 U enrichment 1 20 % Packing Fraction 1 20 % Parameters Burn-Up Energy per Ball MWD/Ton MWD 235 U and 238 U used in the core % Consumed mass of 235 U and 238 U Critical periods gram month page 7 of 13

10 Parametric Survey 12 %wt 235 U 7% packing fraction of CFP page 8 of 13 Parametric survey of the burn-up (MWD/Ton 235 U)

11 Reference Design

12 Reference Design Design Specification Reactor Power 20 MWth Fuel TRISO Core radius 125 cm Core Height 500 cm Reflector width 70 cm Startup fuel layers 85 cm Initial 235 U enrichment Supply fuel 235 U enrichment 12 % 12 % Schematic view of reactor core design Packing Fraction 7.0 % page 9 of 13

13 Reference Design page 10 of 13 Fuel Kernel Radius of the kernel mm UO2 density 10.4 g/cm 3 Boron impurities 4 ppm Coatings First Buffer Layer (PyC) Thickness 0.09 mm Density 1.1 g/cm 3 Boron impurities 1.3 ppm Second Layer (PyC) Thickness 0.04 mm Density 1.9 g/cm 3 Boron impurities 1.3 ppm Third Layer (SiC) Thickness mm Density 3.18 g/cm 3 Boron impurities 1.3 ppm Forth Layer (PyC) Thickness 0.04 mm Density 1.9 g/cm 3 Boron impurities 1.3 ppm Fuel Ball Diameterof the ball 6.0 cm Diameter of fuel zone 5.0 cm Packing fraction of Coated Fuel Particle (CFP) 7.0 % Enrichment of 235 U 12 % Equivalent natural boron content of impurities in uranium 4.0 ppm Percentages of fuel balls in the core 57 % Packing fraction of fuel and dummy balls in the core 61 %

14 Reference Design page 11 of 13 keff for each fuel-loading step * The average burnup value of this design is 9.44 x 10 4 MWD/T-U

15 Conclusions

16 Conclusions Concept of innovative small high temperature gas cooled pebble bed reactor with possibility to simplify the reactor system by removing the unloading devices has been performed A code for criticality analysis of automates Peu a Peu fuel load scheme process has been developed and tested From the parametric survey in the infinite geometry, the maximum burnup value can be expected if the inserted fuel element is 12 wt% U-235 enrichment with 7% packing fraction page 12 of 13

17 Conclusions A whole-core calculation for the small 20 MWth reactor was performed. This reactor design can maintain its criticality for up to 12 years, with the average burnup is 9.44 x 10 4 MWD/T-U, which is comparable to that of the conventional PBRs design Further analysis such as reduction of the power peak near the top of the reactor core is necessary to performed in order to optimize this design page 13 of 13

18 THANK YOU