Neutrons, fusion and efficiency

[John Plant]

TL;DR Summary

capturing only a percentage of the fusion neutrons in the thermal blanket to generate energy.

Regarding electricity generation from a fusion reactor:
I can't seem to find any discussion about the percentage of fusion product neutrons that can be realistically caught in the thermal blanket to utilise the energy they carry from the fusion reaction.
The neutrons from fusion have to be slowed to change their kinetic energy into heat so electrical power can be generated at a steam turbine. Thermal blanket may be the wrong term but I think it's obvious what my enquiry concerns.
So how comprehensive is the coverage of said ' thermal blanket' and what percentage of fusion energy is expected to be lost by neutrons that escape through the areas not covered by this thermal blanket ?
I can't imagine it is anywhere even close to 100% of the fusion product neutrons being caught in the "thermal blanket" to extract the KE they carry.
Nevermind catching the energy from neutrons that have been used to produce more tritium.

 

[jartsa]

As neutrons move straight, they will not get out through a tunnel that is not straight.

Is there any need to have a straight hole going through the blanket?



(To answer my question: No there isn't. So, if 100% blanket coverage is needed, then it can be quite easily achieved. Oh, yes 100% coverage is needed to protect the superconductors, so there will be 100% coverage then.)

 

[mathman]

As neutrons move straight, they will not get out through a tunnel that is not straight.

Is there any need to have a straight hole going through the blanket?

There is lots of room between nuclei, so a "hole" is not relevant. Number of neutrons escaping without interaction decreases exponentially with thickness. However more neutrons can get through (at lower eneergy) after scattering.

 

[jartsa]

There is lots of room between nuclei, so a "hole" is not relevant. Number of neutrons escaping without interaction decreases exponentially with thickness. However more neutrons can get through (at lower eneergy) after scattering.

By hole I mean an area not covered by the blanket. Like a hole through which a supporting concrete pillar goes through, or hole for electric wiring, or holes for cooling pipes, or a path trough which an engineer can walk into the reactor.

Actually blanket is the same as the inner wall. I just looked it up. I thought it was some thick blanket behind the inner wall, sorry. So how could part of the inner wall be missing?

Oh yes one part of the wall is called divertor. @John Plant, do you think the divertor might cause a loss of neutron energy?

 

[mfb]

All the neutrons will be caught somewhere. Nearly all of them in regions that will get hot - and can contribute to the electricity production. A reactor design might decide to discard the heat from some colder regions where it would be uneconomical to use the heat.