0 20 40 60 80 100Starting percent of Be12Ti intotal Be12Ti + Li4SiO4 volume

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0 20 40 60 80 100Starting percent of Be12Ti intotal Be12Ti + Li4SiO4 volume

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0 20 40 60 80 100Starting percent of Be12Ti intotal Be12Ti + Li4SiO4 volume

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123

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J. Shimwell1, S. Lilley2, M. Kovari2, S. Zheng2, L. Morgan2, J. McMillan1.

Reducing beryllium content in solid-type breeder blankets.

1 - Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK. 2 - Culham Centre for Fusion Energy, Culham Science Centre , Abingdon, Oxfordshire , OX14 3DB, UK.

Corresponding author mail@jshimwell.com

Acknowledgements J. Shimwell would like to acknowledge the financial support of the UK Engineering and Physical Sciences Research Council (EPSRC). The authors would like to thank C. Dorm, E. Vidal, F. Fox, H. Gale, J. Naish, L. Packer, L. Pasuljevic P. Murphy, T. Eade, T. Shimwell, V. Ambros, Z. Ghani and the FDS team for their help completing this research.

References [1] Dombrowski - Manufacture of beryllium for fusion energy applications. Fusion Engineering and Design 1997, Vol 37 [2] Giancarli - Overview of the ITER TBM Program. Fusion Engineering and Design 2013, Vol 87 [3] Kim - A preliminary conceptual design study for Korean fusion DEMO reactor. Fusion Engineering and Design 2013, Vol 88 [4] Bradshaw – Is fusion a sustainable energy form? Fusion Engineering and Design 2011, Vol 86 [5] F. Druyts – Conditioning methods for beryllium waste from fusion reactors. Fusion Engineering and Design 2003, Vol 69

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Abstract Beryllium (9Be) is a precious resource with many high value uses and although little prospecting has occurred [1] it is considered a rare element.

The low threshold (n,2n) reaction makes 9Be the preferred choice material for solid-type breeder blankets in ITER [2] and DEMO designs [3].

Estimates of beryllium requirements suggest that there is insufficient beryllium for fusion energy to supply 30% of the world’s energy [4]. Recycling of irradiated beryllium is viable, albeit costly and laborious work [5]. Another option is to reduce the quantity of beryllium used in breeder blanket designs. Is it possible to reduce the beryllium requirements while achieving the same performance criteria?

The findings of this work show that it is possible to decrease the beryllium usage whilst maintaining a high TBR. The energy amplification of the blanket and peak nuclear heating performance of the blanket were also found to benefit from the reduction in 9Be.

Increase energy amplification.

The heat energy produced in a blanket can be more than the sum of the neutron energies entering the blanket. This is due to the release of binding energy as disturbed nuclei rearrange themselves into stable configurations. This is referred to as energy amplification.

The amount of energy amplification in breeder blankets is directly related to the amount of electricity generated. Increasing the energy amplification therefore improves the economic viability of the reactor.

Reduce hot spots.

The maximum neutronic and photonic energy deposited in any one region should be kept low to minimise the chance of hot spots forming and softening or melting materials.

As the 9Be(n,2n) reaction is a threshold reaction and therefore endothermic, this results in lower temperatures in regions where the reaction occurs. Therefore use of 9Be at the front of the blanket can reduce the peak heating in the blanket.

Maintain sufficient tritium breeding ratio (TBR).

Reducing the beryllium volume in the blanket allows more space for lithium ceramic which is responsible for the vast majority of tritium production in the blanket.

Neutron multiplying and tritium producing reactions require different energy neutrons. As the 6Li(n,t)4He reaction is predominantly a thermal reaction and therefore it can remain effective even at the rear of the blanket.

Decrease quantity of beryllium.

By varying the beryllium content in relation to blanket depth it is possible to find high performing blanket compositions that contain less 9Be.

This may reduce costs as Be12Ti is expected to cost $4500 per kg. It will also reduce the dependence on a rare material. Therefore it is important to reduce the amount of 9Be to produce economically attractive reactors.

Current mixed bed blanket designs employ

a uniform ratio of lithium ceramic and beryllium

multiplier throughout the entire blanket.  

The approach taken in this work considers

varying the lithium to beryllium ratio with relation to blanket

depth.

Final Be12Ti to Li4SiO4 ratio of

20%  

Initial Be12Ti to Li4SiO4 ratio of

80%  Constant Be12Ti to Li4SiO4 ratio

of 70%  

Li4SiO4   Be12Ti  

Image courtesy of EUROfusion.  

Comparing performance.

The key performance criteria of blankets capable of achieving a TBR of 1.2 are compared.

The shaded yellow region shows compositions which perform significantly better than blanket designs with a uniform ratio of Li4SiO4 to Be12Ti.

It was possible to increase the energy amplification by 2%, reduce the peak heating by 10% and decrease the 9Be mass by 20% while maintaining a high TBR.

Maintain  TBR  

Less  hot  spots  

Increased  energy    

Reduced  9Be  mass