Homework Problem #5In this tutorial, you are going to learn how to run the REAL crit safety SCALE sequence: CSAS5. This sequence is like CSAS1, but uses three dimensional geometry, giving it the capability to analyze more real-world problems than the simple spheres that we learned how to analyze in CSAS1.
The good news is that the material description is exactly the same for CSAS5 and CSAS1. The difference comes in the specification of the geometry: KENO (the 3D transport model inside CSAS5) lets you create complex 3D geometries, far beyond the simple spherical layers that we learned in the previous exercises.
Despite the complexity of the 3D geometries, the basic approach to describing geometries remains the same. You will recall that the spherical layers of the CSAS1 geometry were laid out from the INSIDE OUT. That is, when we included the water layer, we specified the material and radius of the central region first, then the material and radius of the next layer out, etc. In the 3D world of KENO, we describe UNITs (which are standalone components in the geometry--like canisters inside a glovebox or the glovebox itself), the same way: from the inside out. But, instead of being limited to spheres, the layers can either be SPHEREs, CYLINDERs, or CUBOIDs (rectangular boxes).
HISTORICAL NOTE: Many years ago, the SCALE group created a replacement for KENO5.a (used in CSAS5) that allowed much more geometric flexibility--more shapes, the ability to have overlapping boundaries (that violate the inside-out requirement), etc.--at the expense of a more complicated input. This version is KENO6 and is embedded in the sequence CSAS6. For the most part, the criticality safety community rejected this change and requested that KENO5.a and CSAS5 be kept "alive". It remains true that CSAS5 has remained the "workhorse" of criticality safety. (And if we need more geometric flexibility, we simply go to MCNP to get it.)
Describing a layerJust like specifying the outer radius of layers in CSAS1, the layers in a KENO unit are described by specifying a material number and an outer surface that contains it (except for internal layers that have previously been specified). Here is the syntax for each of the three that we will use. (The manual describes these and the other outer surface shapes that you can use.)
A SPHERICAL layer is specified with the syntax:SPHERE mat# 1 radius ORIGIN x y z [These last 4 are optional. Without them, the sphere is centered on (0,0,0).]
SPHERE 3 1 5.6specifies a region that contains material 3 and has an outer surface that is a sphere centered on (0,0,0) with a radius of 5.6 centimeters.
SPHERE 2 1 4.2 origin 1 2 3specifies a region that contains material 2 and has an outer surface that is a sphere centered on (1,2,3) with a radius of 4.2 centimeters.
(Yes, there is an extra "1" sitting there, not doing anything. It means something to the ORNL guys--something about importance, if I remember correctly--but we will just have the "1" in that position every time.)
A CYLINDRICAL layer is specified with the syntax:CYLINDER mat# 1 radius +z -z ORIGIN x y [These last 3 are optional. Without them, the cylindrical axis is the z axis, with x=0 and y=0.]
The +z is the elevation of the TOP of the cylinder and -z is the elevation of the BOTTOM of the cylinder.
You are free to put the origin anywhere in the unit that you want to--but remember where you put it!
CYLINDER 1 1 5.6 10 0specifies a region that contains material 1 and has an outer surface that is a cylinder centered on the z axis with a radius of 5.6 which goes from 0 to 10 centimeters. (Note that this puts the origin at the center of the bottom surface of the cylinder, which is my preference. Some analysts prefer to put it in the center of the cylinder--in which case the last two numbers in the line would be 5 and -5. Do what you want.)
CYLINDER 8 1 4.1 7 2 origin 1 2specifies a region that contains material 8 and has an outer surface that is a cylinder centered on (1,2) with a radius of 4.1 centimeters which goes from 2 to 7 centimeters in z.
A CUBOID layer is specified with the syntax:CUBOID mat# 1 +x -x +y -y +z -z
The -x, +x, -y, +y, -z, and +z are the upper and lower limits of the x, y, and z ranges. The tough part is remembering the order that these must be listed.
CUBOID 11 1 5 -5 6 -6 7 -7specifies a region that contains material 11 and has an outer surface that is a rectangular parallelpiped (a box) ranging from -5 to 5 in x, -6 to 6 in y, and -7 to 7 in z
Describing a multilayer UNIT
The syntax to creating a UNIT (a standalone object in KENO) is:
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