26.08.2015   ACCELERATOR DRIVEN SUBCRITICAL REACTORS

The surfaces

The geometry of a problem is described in the Cell cards; cells are volumes delimited by surfaces; these volumes may or may not be filled with materials. But before seeing how to define cells, let us see how Surface cards are defined.

MCNP has a wide choice of surface types to describe cells; however, here we will just present the surface types that we will use for our reactor examples. A Surface card consists in a surface number, a special keyword indicating the type of the surface, and parameters for that keyword. Table

5.2 lists these surfaces and their parameters.

Surface type

Keyword

Parameters

Equations

General plane

P

ABCD

Ax + By + Cz — D = o

Plane perpendicular to X-axis

PX

D

x — D = o

Plane perpendicular to Y-axis

PY

D

У — D = o

Plane perpendicular to Z-axis

PZ

D

z — D = o

Cylinder parallel to X-axis

C/X

Уо zo R

(y — yo f + (z — zo)2 — r2 = o

Cylinder parallel to Y-axis

C/Y

xo zoR

(x — xo)2 + (z — zo)2 — R2 = o

Cylinder parallel to Z-axis

C/Z

Xo yo R

(x — xo)2 + (y — yo)2 — R = o

Cylinder along X-axis

CX

R

о

+

Cylinder along Y-axis

CY

R

x2 + z2 — R2 = o

Cylinder along Z-axis

CZ

R

x2 + y2 — R2 = o

General sphere

S

Xo yo Zo R

(x — xo)2 + (y — yo^+

InT4

N

о

1

О

Sphere centred at origin

SO

R

x2 + y2 + z2 — R2 = o

Table 5.2. Some surface cards.