Elsevier

Fusion Engineering and Design

Volume 136, Part B, November 2018, Pages 1370-1375
Fusion Engineering and Design

On the thermal and thermomechanical assessment of the “Optimized Conservative” helium-cooled lithium lead breeding blanket concept for DEMO

https://doi.org/10.1016/j.fusengdes.2018.05.013Get rights and content

Highlights

  • Thermal and thermomechanical behaviour of the “Optimized Conservative” DEMO HCLL BB has been numerically investigated.

  • The steady state nominal loading conditions foreseen for DEMO BB have been considered.

  • Three successive 3D FEM models have been realized, modelling also the Cap.

  • Thermal results showed that small modifications to the cooling system should be performed.

  • Thermomechanical results showed that RCC-MRx criteria are not totally fulfilled due to secondary stress.

Abstract

Within the framework of EUROfusion R&D activities a research campaign has been performed at CEA-Saclay, in close collaboration with the University of Palermo, in order to investigate thermal and thermomechanical performances of the “Optimized Conservative” concept of DEMO Helium-Cooled Lithium Lead breeding blanket (HCLL). Attention has been paid to the HCLL outboard equatorial module (OEM) when subjected to the steady state nominal loading scenario. To this purpose three simplified 3D models, characterized by an increasing level of detail, have been set-up taking into account, firstly, a single radial-toroidal slice, then a basic module geometric unity composed by two adjacent slices and adding, lastly, the peripheral poloidal region. This latter 3D model has allowed the assessment of the Caps potential influence on the module thermal and thermomechanical behaviour. For each investigated 3D model, thermal and thermomechanical analyses have been performed and a stress linearization procedure has been carried out in order to verify the fulfilment of the criteria prescribed by the RCC-MRx 2015 code. The study has been performed adopting a numerical approach, based on the Finite Element Method (FEM), and adopting the Siemens NX v. 10.0 software in order to discretize the geometric domain, whereas thermal and thermomechanical calculations have been carried out using the Cast3 M 2015 FEM code.

The obtained results, herewith reported and critically discussed, allow predicting a good thermal and mechanical behaviour of the “Optimized Conservative” concept of DEMO HCLL OEM, even if some small modifications to the module cooling scheme should be performed in order to avoid the insurgence of hotspots where temperature is slightly above the Eurofer limit temperature (550 °C). This will entail, from the mechanical point of view, a reduction of the secondary stress amount which is the main responsible of the failure in RCC-MRx criteria verification within First Wall-Side Wall bend region.

Introduction

Within the framework of EUROfusion activities, CEA Saclay is in charge of developing the design of the Helium-Cooled Lithium Lead breeding blanket (HCLL) of DEMO nuclear fusion reactor.

In this context a fruitful collaboration has taken place with University of Palermo, as this latter has been involved, long time now, in the studies regarding the ITER Test Blanket Module (TBM) based on HCCL concept [1].

The work described in this paper, developed within the above said collaboration, has been aimed at the investigation of the thermal and thermomechanical performances of the HCLL Outboard Equatorial Module (OEM) under the envisaged nominal steady state loading conditions, paying also attention to the automation of the analysis procedure. In particular, the study has been aimed at the verification of the fulfilling of the set of thermomechanical requirements, in accordance with RCC-MRx code [2], prescribed for HCLL design.

A theoretical-numerical approach, based on the Finite Element Method (FEM), has been followed and the qualified Cast3 M 2015 and Siemens NX v. 10.0 FEM codes [3], [4] have been adopted in the study.

Section snippets

HCLL “Optimized Conservative” concept

Within the framework of HCLL design activities [5], 3 different concepts (Optimized Conservative, Advanced [6], [7], Advanced-Plus [8]) have been assessed. All the concepts use Eurofer steel as structural material, Helium at the pressure of 8 MPa as coolant and the eutectic alloy Pb-15.7Li enriched at 90% in 6Li as breeder, neutron multiplier and tritium carrier.

In this paper, attention has been focused on the “Optimized Conservative” concept, which is consistent with the TBM approach [9] and

The FEM models

In order to investigate thermal and thermomechanical performances of the “Optimized Conservative” DEMO HCLL OEM, paying also attention to analysis procedure automation, three successive FEM models (Model 1, Model 2 and Model 3) have been set-up. For all of them, cooling helium has been properly modelled, as well as the breeder.

As to material properties, they have been considered to depend uniquely by temperature [10].

Analysis and results

Un-coupled thermal and thermomechanical steady state analyses have been performed adopting the described FEM models. The most representative results are reported and critically discussed in the following.

Conclusion

The research campaign, carried out within the framework of a close collaboration between CEA Saclay and University of Palermo, has allowed of minimizing the number of user-defined variables in the analysis procedure. Moreover, obtained results show good thermal and mechanical behaviour of the “Optimized Conservative” DEMO HCLL concept. However high temperature on the FW-Cap connection occurs and high stress is calculated near to the bend region of the FW-SW, where only RCC-MRx criterion against

Acknowledgements

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

References (13)

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