MCNP CLASS SERIES (MCNP GEOMETRY) Jongsoon Kim

Transcription

MCNP CLASS SERIES
(MCNP GEOMETRY)
Jongsoon Kim
Learning Objectives: Geometry

Understand how to
define all four classes
of surfaces
Understand how to
create cells from
surfaces
Understand the
detailed definition of
macrobodies
Geometry Basics

The “universe” is divided into regions of different
materials and properties
The entire infinite universe must be included in
geometric model
The basic unit of a geometry is a “cell”
All cells are defined by bounding surfaces
All surfaces divide the universe into two regions
Quick Start:
Surfaces

Equation surfaces
Surfaces
defined by providing the equation of the
surface and the parameters (Table 3.1)
Examples

A sphere located at the origin with radius R
j

R
A cylinder parallel to the y-axis at x, z with radius R
j

so
c/y X Z R
A plane normal to the z-axis at Z
j
pz
Z
Quick Start:
Combining Surfaces into Cells

Interior points of cell are related to a surface by
the “sense” of the cell: ‘t’ or ‘-’
Surfaces

divide universe into 2 half-regions
Boolean operators
Combine
half-regions to create cells/objects
Intersection
Union
Complement

Quick Start: Combining Surfaces into Cells
Sense

All the points in a cell are related to the surfaces
that define the cell by the sense – which side of a
surface the points of a cell are on
+ (positive sense):
For open surfaces (planes), points in positive direction from
surface
For closed surfaces (spheres, cylinders, etc), outside the
surface
- (negative sense):
For open surfaces, points in negative direction from surface
For closed surfaces, inside the surface
Intersection

Space where both
senses are true
Input syntax: a
<space> between two
surface numbers
2_-1represents
only
the region of space
with sense +2 and
sense -1
Union

Space where either
sense is true
Input syntax: a
<colon> ‘:” between
two surface numbers
2:-1
represents both
the region of space
with sense +2 and the
region with sense -1
Complement

Space outside another cell
Input syntax: a <pound
symbol> ‘#’ before a cell
number
#5 represents the region
outside cell 5
This region can then be
intersected or united
with other regions
-2 #5 represents the only
the region outside cell 5
and inside surface 2
Four Classes of MCNP Surfaces:
Analytic Equations

Analytic equations
Planes,
Spheres, Cylinders, Cones, Tori, Arbitrary
Quadratics
Macrobodies

Combinatorial geometry based on closed primitives
Surfaces of finite “building blocks”
BOX:
arbitrarily oriented orthogonal box
RPP: rectangular parallelepiped

All surfaces normal to respective axes
SPH:

Identical to “equation” for sphere
RCC:

sphere
right circular cylinder
Axis orthogonal to base, but arbitrarily oriented
Axisymmetric sets of points

Planes & Linear or Quadratic surfaces
Example 1: j Z 7 5 3 2 4 3
A
surface sysmmetric about z-axis, which passes
through the three (z,r) points, (7,5), (3,2), and 4,3)
Three point in a plane

General Planes
Form: j P X1 Y1 Z1 X2 Y2 Z2 X3 Y3 Z3
Coordinates
of three points lying in the desired plane
Convert them to the required surface coefficient to
produce plane
Ax + By + Cz – D = 0
Coordinate Transformation

TRn Data Card (see page 3-31)
TRn

Ox Oy Oz Bxx’ Byx’ Bzx’ Bxy’ Byy’ Bzy’ Bxz’ Byz’ Bzz’
n
Number

of transformation
Ox Oy Oz
Displacement

vector of the transformation
Bxx’ . . . Bzz’
Rotation
matrix of the transformation
Angles in degrees when *TRn card is used, otherwise in
cosines
Example of Coordinate Transform
(CCW 67.5 for apple simulation for 1.35 MeV electron beam irradiation)
o
Z
Y
Z
Y
xx’ yx’ zx’ xy’ yy’
*TR1 0 0 0 0
90 90
zy’
xz’ yz’
zz’
90 67.5 22.5 90 157.5 67.5
Homework

Think about your geometry for term project and
make cell and surface cards