## thermal flux through a part of surface and particlar direction

Discussion on physics, models and calculation methods
ahmed
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### thermal flux through a part of surface and particlar direction

Hello everyone

I am now doing calculations for a new research reactor (neutron source) and I want to calculate the thermal neutron current or flux passing through part of the surface (shown in red in the figure) and inside channel in the direction perpendicular to this part of surface.

surf 56 cuboid -10 10 25.0622 35.0622 -5 5
surf 57 cuboid -10 10 -35.0622 -25.0622 -5 5

surf 58 cube 32.50129831208109 20.9547 0.0 5
trans s 58 rot 32.50129831208109 20.9547 0.0 0 0 1 -60

surf 64 cone 0 64.5 0 17.3578 35.58
trans s 64 rot 0 64.5 0 1 0 0 90

surf 65 cone 0 -64.5 0 17.3578 35.58
trans s 65 rot 0 -64.5 0 1 0 0 -90

surf 66 cone 0 0 -21.34256364 3.763269807 21.34256364
trans s 66 -1.34256364 30.0622 0 -10 -90 0 1
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Ana Jambrina
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### Re: thermal flux through a part of surface and particlar direction

Check the surface current/flux detector (ds) - combine it with (single)mesh/cell detectors to define the integration surface of the detector (option available in Serpent 2.1.32; for Serpent 2.1.31, you can implement the necessary changes by following the description of the post: viewtopic.php?f=15&t=3672#p11804) - results are integrated over the surface, energy and all directions.

Specifying a direction might be possible playing around with ‘superdet.c’ routine imposing certain constrain(s) to evaluate currents in a given direction, 3D-angle or solid-angle (u,v,w represent the direction-cosines) - most likely, single direction per run.
- Ana

ahmed
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### Re: thermal flux through a part of surface and particlar direction

Thanks alot Ana for fast response,
i cant understand what do you mean by "(single)mesh/cell detectors "?

Ana Jambrina
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### Re: thermal flux through a part of surface and particlar direction

i.e. use of mesh and cell detectors with a single bin when combined with surface detectors.
- Ana

ahmed
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### Re: thermal flux through a part of surface and particlar direction

some thing like that ??

det 1 ds 65 1 dc 52 dumsh UNI NC CELLn, BINn

if yes, which universe must be ?

Ana Jambrina
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### Re: thermal flux through a part of surface and particlar direction

e.g: surface detector (ds) + mesh detector (dx/dy/dz Cartesian, dh hexagonal, dn spherical) / cell detector (dc) —> single bin means single value detector.
- Ana

ahmed
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### Re: thermal flux through a part of surface and particlar direction

thanks alot Ana, i will try and tell you the result.

ahmed
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### Re: thermal flux through a part of surface and particlar direction

Good evening
Please review this command, for outward current detector which calculate thermal neutron current (< 0.5 eV), in direction perpendicular to the surface number 56 according to the following figure, is this correct ?

ene MyEnergyGrid1 3 1 1e-11 0.5E-6
det 1 ds 56 1 dc 52 dn 2 35.72464 35.72464 1 64 116 1 64 116 1 de MyEnergyGrid1 dir 0 1 0
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Last edited by ahmed on Sun Mar 21, 2021 12:53 pm, edited 1 time in total.

Ana Jambrina
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### Re: thermal flux through a part of surface and particlar direction

Some notes:
- Direction detectors are not allowed with surface detectors.
- The idea is to define a surface where you want to calculate flux/current and limit the spatial domain of integration by another detector.
- Surface 65 is not defined. If the typo refers to surface 64 cone, in this case the surface do not define the region of interest in the first place; if it corresponds to surface 56 cuboid, the curvilinear mesh detector should define the area corresponding with the truncated cone at such position.
- Alternatively, you could define a surface that is not part of the geometry, corresponding with area of the cuboid where you want to calculate the outward current, e.g. (top) plane, and limit it by a curvilinear (cylindrical/spherical) detector that corresponds with the cone area (in this way, it would be easier to avoid problems with the curvilinear detector defining multiple regions within the cuboid surface) .
- Check the curvilinear detector definition (see 'dn' syntax). The definition might refer to the local/global coordinate system, but it needs to define a real volume (in the current definition, rmin = rmax) - collision detectors, e.g. mesh detectors, are volumetric.

** Maybe it would be easier to understand the functionality creating a simple model and playing around with it to evaluate the flux/current of different portions of a surface. Or, in the given model, applying it to an easier case for testing purposes, such the ‘blue’ cuboid: e.g. split it among different parts or faces and compare with respect total.
- Ana

ahmed
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### Re: thermal flux through a part of surface and particlar direction

Ana, can you please write an example, or try to define detector which calculate the current or flux getting out from the cube and goes through the channel defined by cone. It is very important for my calculations and I can't understand you very well .
i corrected the typo above, i refer to surf 56, and used spherical mesh to cut this part of surface where i want to calculate the current, and for r i want to use constant r but i dont know how i can type it.
and what do you mean by "/ cell detector" ?