3 Reactor Kinetics
61
Table 3.4 Comparison of measured subcriticalities obtained by the area ratio method and calculated
subcriticalities by MCNP (JENDL-3.3) (Ref. [2])
Case MCNP
(%k/k)
Fiber #1
(%
C/E
Fiber #2
(%
C/E
Fiber #3
(%
C/E
10
0.97 ± 0.03
0.99 ± 0.01 0.98
0.96 ± 0.01 1.01
0.99 ± 0.01 1.03
11
1.83 ± 0.03
1.88 ± 0.02 0.97
2.15 ± 0.02 0.85
1.78 ± 0.02 1.03
12
2.55 ± 0.03
2.55 ± 0.03 1.00
3.12 ± 0.03 0.82
2.42 ± 0.02 1.05
13
3.45 ± 0.03
3.40 ± 0.03 1.02
3.25 ± 0.03 1.06
3.63 ± 0.04 0.95
14
4.15 ± 0.03
4.49 ± 0.04 0.93
4.00 ± 0.04 1.04
4.60 ± 0.05 0.90
15
6.24 ± 0.03
5.89 ± 0.06 1.06
6.54 ± 0.07 0.95
6.87 ± 0.07 0.91
16
6.76 ± 0.03
6.59 ± 0.07 1.03 10.01 ± 0.10 0.67
7.56 ± 0.08 0.89
17
7.41 ± 0.03
7.55 ± 0.08 0.98
8.18 ± 0.08 0.91
8.64 ± 0.09 0.86
18
10.38 ± 0.03 10.24 ± 0.10 1.01 12.28 ± 0.12 0.85 11.93 ± 0.12 0.87
appeared little affected by the increase in the subcriticality, with the discrepancy
being within 7% even for the largest subcriticality, while Fibers #2 and #3 reached
about 30%. This tendency can be clearly seen in Fig. 3.6.
The results allowed some estimation of the relative effects among the various
parameters suspected to influence the measurement of the subcriticality by the
neutron pulsed technique and the prompt neutron decay constant. Although the same
value of the delayed neutron fraction was used for the area ratio method (Table 3.5),
the results from Fiber #2 allowed the evaluation of the variation in the delayed
neutron fraction to be in the smallest order of the uncertainty over the subcriticality.
The measurements from Fiber #2 (Fig. 3.7), although underestimating the subcriticality (Fig. 3.6), tended to give a relatively good evaluation of the prompt neutron
decay constant compared with those from Fiber #3. Fiber #1, however, gave a marked
underestimation of the prompt neutron decay constant of less than 7%. Finally, Fiber
Fig. 3.6 Measured and
calculated results of
subcriticalities in KUCA
kinetic experiments (Ref.
[2])
0
2.00
4.00
6.00
8.00
10.00
12.00
0
2.00
4.00
6.00
8.00
10.00
12.00
Caluclated subcriticality ρ Cal (%Δk/k)
Measured subcricality
ρ Exp (%Δk/k)
Fiber #1
Fiber #2
Fiber #3
61
Table 3.4 Comparison of measured subcriticalities obtained by the area ratio method and calculated
subcriticalities by MCNP (JENDL-3.3) (Ref. [2])
Case MCNP
(%k/k)
Fiber #1
(%
C/E
Fiber #2
(%
C/E
Fiber #3
(%
C/E
10
0.97 ± 0.03
0.99 ± 0.01 0.98
0.96 ± 0.01 1.01
0.99 ± 0.01 1.03
11
1.83 ± 0.03
1.88 ± 0.02 0.97
2.15 ± 0.02 0.85
1.78 ± 0.02 1.03
12
2.55 ± 0.03
2.55 ± 0.03 1.00
3.12 ± 0.03 0.82
2.42 ± 0.02 1.05
13
3.45 ± 0.03
3.40 ± 0.03 1.02
3.25 ± 0.03 1.06
3.63 ± 0.04 0.95
14
4.15 ± 0.03
4.49 ± 0.04 0.93
4.00 ± 0.04 1.04
4.60 ± 0.05 0.90
15
6.24 ± 0.03
5.89 ± 0.06 1.06
6.54 ± 0.07 0.95
6.87 ± 0.07 0.91
16
6.76 ± 0.03
6.59 ± 0.07 1.03 10.01 ± 0.10 0.67
7.56 ± 0.08 0.89
17
7.41 ± 0.03
7.55 ± 0.08 0.98
8.18 ± 0.08 0.91
8.64 ± 0.09 0.86
18
10.38 ± 0.03 10.24 ± 0.10 1.01 12.28 ± 0.12 0.85 11.93 ± 0.12 0.87
appeared little affected by the increase in the subcriticality, with the discrepancy
being within 7% even for the largest subcriticality, while Fibers #2 and #3 reached
about 30%. This tendency can be clearly seen in Fig. 3.6.
The results allowed some estimation of the relative effects among the various
parameters suspected to influence the measurement of the subcriticality by the
neutron pulsed technique and the prompt neutron decay constant. Although the same
value of the delayed neutron fraction was used for the area ratio method (Table 3.5),
the results from Fiber #2 allowed the evaluation of the variation in the delayed
neutron fraction to be in the smallest order of the uncertainty over the subcriticality.
The measurements from Fiber #2 (Fig. 3.7), although underestimating the subcriticality (Fig. 3.6), tended to give a relatively good evaluation of the prompt neutron
decay constant compared with those from Fiber #3. Fiber #1, however, gave a marked
underestimation of the prompt neutron decay constant of less than 7%. Finally, Fiber
Fig. 3.6 Measured and
calculated results of
subcriticalities in KUCA
kinetic experiments (Ref.
[2])
0
2.00
4.00
6.00
8.00
10.00
12.00
0
2.00
4.00
6.00
8.00
10.00
12.00
Caluclated subcriticality ρ Cal (%Δk/k)
Measured subcricality
ρ Exp (%Δk/k)
Fiber #1
Fiber #2
Fiber #3