SUBCRITICAL MULTIPLICATION
DOE-HDBK-1019/2-93
Reactor Theory (Reactor Operations)
Solution:
Step 1:
Calculate 1/M for each of the rod positions using equation (4-5). The
reference count rate is 50 cps at a rod position of zero.
Rod Withdrawal
(inches)
Count Rate
(cps)
CRo/CR
0
50
1
2
55
0.909
4
67
0.746
6
86
0.581
8
120
0.417
10
192
0.260
12
500
0.100
Step 2:
Plotting these values, as shown in Figure 1, and extrapolating to a 1/M
value of 0 reveals that the reactor will go critical at approximately 13
inches of rod withdrawal.
Figure 1 1/M Plot vs. Rod Withdrawal
NP-04
Rev. 0
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