5 Neutron Spectrum
133
Fig. A2.7. To investigate the accuracy of reaction rate analyses at different subcritical states, the
115 In(n, γ)
116m In reaction rate distributions along the (14-13, P-A)
region in Figs. A2.16a–d were measured with subcriticality ranging from 2,483 to
11,556 pcm. From a comparison between the measured and the calculated
115 In(n,
γ)
116m In reaction rate distributions in Cases II-1 and II-3, as shown in Figs. 5.2a, b,
respectively, the calculated
115 In(n, γ)
116m In reaction rates reproduced successfully
the measured ones at an acceptable accuracy with the MCNP fixed-source calculations in the subcritical states, demonstrating the allowance within the experimental
statistical error.
To estimate the effect of spallation neutrons on the neutron multiplication in
ADS, the subcritical multiplication factor k s is acquired as Eq. (5.6), on the basis of a
theoretical background [5]. A comparison between experiments and calculations of k s
Fig. 5.2 Comparison
between measured and
calculated 115 In(n, γ) 116m In
reaction rate distributions
along (14-13, P-A) region
(Ref. [9])
(a) Case II-1
(b) Case II-3
-50
-40
-30
-20
-10
0
10
0
50
100
150
200
Distance from location of Pb-Bi target [cm]
Normalized reaction rate [Arbitrary units]
Polyethylene
region
Normal fuel region
Pb-Bi-zoned
fuel region
Normal
fuel region
Calculation
Experiment
-50
-40
-30
-20
-10
0
10
0
50
100
150
200
Distance from location of Pb-Bi target [cm]
Normalized reaction rate [Arbitrary units]
Polyethylene
region
Normal
fuel region
Pb-Bi-zoned
fuel region
Normal
fuel region
Calculation
Experiment