Nuclear heating and helium production at the inboard divertor rail for DEMO

• Distributions of heating and helium production at the divertor were calculated.
• Three design variants for DEMO were examined.
• Both the heating and the He production can be significantly reduced.
• The nuclear heating is dominated by photons.
• The steel rail and the extended divertor are essential for the DEMO design.

Monte Carlo simulations were carried out for the DEMO model. Distributions of both the nuclear heating and the helium production in the area between the blanket and the divertor were calculated with the MCNP5 code for the reference case, when the DEMO geometry was not changed. Next a segment of the divertor and the lower part of the manifold were modified. Two new arrangements were studied. The simulations show that for one of the examined cases the helium production and the nuclear heating can be reduced roughly three or even four times in the investigated area. Besides the nuclear heating and the He production were estimated at the fastener (bolt head). The use of the modified divertor and a rail protecting the blanket is essential in the DEMO design.