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Pim Joostens - Internship at QST

Conceptual design evaluation of in-box LOCA resistant cylindrical shaped tritium breeder modules using MCNP

Because a cylindrical shaped vessel is a good configuration to resist pressure, the Japanese blanket development team has proposed a cylindrical shaped Breeding Blanket (BB) as part of the ITER Test Blanket Module design contest, in contrast to the often considered box shaped BB. Pressure resistance is essential because high pressure coolant improves energy conversion. Furthermore, the in-box LOCA (Loss of Coolant Accident) criteria state that the test blanket module walls need to be able to withstand coolant pressure. Comparison of different vessel shapes at different design pressures was considered interesting as some shapes are better in resisting pressure, and also optimization of a concept breeding vessel with cylindrical shape could still be done.

To increase understanding in the effect of coolant pressure and vessel shape an effort was made to numerically evaluate the Tritium breeding ratio (TBR) of different module design using MCNP (Monte Carlo N-Particle) code. It resulted that a cylindrical blanket shows a higher TBR, especially when an hemispherical head was considered. Also a relation between pressure and TBR was found, where a higher coolant pressure would lead to a lower TBR. Without the in-box LOCA criteria the effect of pressure on the TBR was approximated to be 4 times smaller. In addition it was found that a cylindrical vessel with a toroidal orientation has an optimal radius in term of TBR, where there is a balance between neutron capture and shielding of the first wall.

At the National Institute for Quantum and Radiological Science and Technology (QST) in Japan I learned a lot about breeding blanket development and technology. I now know more about the current state blanket development is in, which is linked to the ITER design challenge, the challenges that still exists, some design choices that need to be made that lead to different BB concepts and about the tools that are used to evaluate different designs. Especially about neutronic programs such as DoHeat3 and MCNP, which I used extensively during my research. Besides general topics concerning BB design and the topics coved in my research ,such as pressure vessel calculations and Rankine cycle thermal efficiency, I learned about DD-reactor startup and its only minor effect on the BB design, hence the decision to pursue another topic for research. Besides the experiences gathered at QST I am glad to have had the chance to travel in Japan and learn many things about their culture and food. Only the noodles are reason enough to go back to Japan someday, as they were delicious. To conclude I would like to thank EUROfusion and FuseNet for providing me with this opportunity, which is enjoyed to the fullest.