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pin rod are divided into four regions. Since each rod is discriminated in the primary stage, the number
of regions for rods amounts to 24. The inner and outer coolant regions are assigned by the succeeding
numbers; 25 and 26.
A line (neutron path) defined by a pair of (ρ,ϕ) is drawn across the cell where ρ is the signed
distance OM from the center of the cell O to the line, and ϕ is the angle made by this line and the
horizontal line. The line intersects with the region boundaries at A,B,C,......L. The point M (OM ⊥ AL)
is the origin of the measure on the line AL.
The preliminary trace table consists of an array T of which element is the signed distance from
the point M to each intersecting point, an integer array IR for the region number of the right hand side
of the point, and another array IL for the region number of the left hand side of the point.
12
8
4
4
11
10 5 6 7 L
9
26
G H I J K
3
3
2 2
1
6
1
16 15 25
14 13 O 1 2 3 4
A B C D E F M ρ 4 3 5
2 1 2 3 4
1
ϕ
17
21
1
1
18
22
2
2
19
23
3
3
20
24
4
4
a. S-Region map. b. T-Region map.
Fig.7.1-6
A hexagonal cell with six pin rods on a circle crossed by a line defined
by a pair of parameters (ρ and ϕ)
The computing process is organized to find, first, the intersections A and L on the hexagonal
boundary, then D and I on the circle through the rods centers. At this step, the preliminary trace table is
made up as shown in Table 7.1-1.
Table 7.1-1 Preliminary trace table after scanning annular regions
Position 1 2 3 4
T
l AM
l DM
l MI
l ML
IR 26 25 26 -
IL - 26 25 26
241