Automated parametric neutronics analysis of the Helium Cooled Pebble Bed breeder blanket with Be12Ti

J Shimwell,L Lu,Y Qiu,P Pereslavtsev,A Häußler,F Hernández,C Zeile,T Eade,G.A Spagnuolo,S Mcintosh,L Packer,T Barrett

doi:10.1016/j.fusengdes.2017.01.004

Abstract

The Helium Cooled Pebble Bed (HCPB) breeder blanket is being developed as part of the European Fusion Programme. Part of the programme is to investigate blanket designs relevant for future demonstration fusion power plants. This paper presents neutronics analyses of the HCPB with an alternative neutron multiplier, Be12Ti which is incorporated into the design, replacing the current Be multiplier. A parameter study was performed for a range of geometries to identify the optimal heights of the lithium ceramic and neutron multiplier pebble beds. Automated creation of CAD models followed by conversion to constructive solid geometry (CSG) and unstructured mesh (UM) geometry allows the models to be useful for both neutronics simulations and engineering simulations. In this neutronics study simulations were performed using MCNP 6.1 to find the tritium breeding ratio, energy multiplication and the volumetric heat loads of different blanket designs. Combinations of geometry parameters and material choices that resulted in adequate TBR values were identified and will be further investigated with automated engineering simulations. This paper provides insight, supported by neutronics analysis, on the validity of the design and comments on some of the potential advantages and disadvantages of using Be12Ti in the Helium Cooled Pebble Bed (HCPB) breeder blanket. Blankets with Be12Ti neutron multiplier were found to produce less tritium but higher energy multiplication when compared to blankets with Be neutron multiplier.

Highlights

Optimising the design of components for use in future power producing fusion reactors requires a combination of analysis techniques
Neutronics analysis is used to calculate important performance metrics for breeder blankets such as: the tritium breeding ratio (TBR), energy multiplication and volumetric heating
Care was taken during the construction of the CAD geometry to avoid the use of spline surfaces to describe Boundary Representation (BRep) solids, this facilitates the CAD to constructive solid geometry (CSG) conversion process as spline surfaces are not supported in CSG

Summary

Introduction

Optimising the design of components for use in future power producing fusion reactors requires a combination of analysis techniques. Neutronics analysis is used to calculate important performance metrics for breeder blankets such as: the tritium breeding ratio (TBR), energy multiplication (the ratio of energy incident on the blanket to energy released in the blanket) and volumetric heating. Thermal hydraulics and structural mechanics analysis are able to utilise outputs of neutronics analysis (e.g. volumetric nuclear heating) and obtain additional performance metrics such as the temperature and stress within components. Neutronics simulations have utilised structured meshes to tally volumetric heating. Recent improvements in MCNP 6.1 [3] allow particle transport and tallying on unstructured meshes that conform to geometry and material boundaries. This opens up the possibility of performing neutronics and engineering analysis on the same underlying CAD geometry. Similar methodologies have previously been suggested [4] and this research represents an earlier application of the unstructured mesh and parametric CAD based neutronics studies for optimising fusion reactor components

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