8 Sensitivity and Uncertainty of Criticality
241
Table 8.15 Uncertainty [pcm] of k eff attributed to manufacturing variation in HEU plates in
Table 8.1 and reproducibility of control rods for E3 core (Ref. [2])
Case Enrichment of
235 U
Vertical length Horizontal length Thickness
Reproducibility of
control rod
II-1
13.20 ± 0.11
3.00 ± 0.25
3.09 ± 0.28
8.40 ± 0.41 2.47 ± 3.16
II-2
13.22 ± 0.11
3.15 ± 0.31
3.41 ± 0.35
7.71 ± 0.41 2.90 ± 3.17
II-3
13.27 ± 0.11
3.00 ± 0.2 9
3.19 ± 0.30
8.11 ± 0.41 3.56 ± 317
II-4
13.36 ± 0.11
3.10 ± 0.29.
2.60 ± 0.31
8.04 ± 0.41 6.78 ± 3.14
II-5
13.50 ± 0.11
2.90 ± 0.32
3.03 ± 0.31
7.42 ± 0.41 3.99 ± 3.16
II-6
13.30 ± 0.11
3.08 ± 0.28
2.89 ± 0.32
7.93 ± 0.41 4.10 ± 3.15
the deterministic approach with the covariance data of JENDL-4.0. Sensitivity and
uncertainty analyses demonstrated that the impact of
27 Al and
235 U was remarkably
large in the KUCA A cores, respectively. Moreover, the numerical results revealed
the quantitative evaluation (about 150 pcm) of uncertainty induced by the JENDL4.0 data library in the A cores. Also, these results indicated that further investigation
is needed of the numerical analyses of uncertainty of
27 Al composed mainly of core
components in the A cores, with the use of
27 Al covariance data, in order to assess
the effect of the uncertainty of
27 Al cross sections on reactivity.
To ensure the accuracy of criticality by experimental analyses at KUCA, the
modeling of core configuration was examined through the comparison of excess
reactivity and control rod worth between the calculation and the experiment in hard
and soft spectrum cores. Furthermore, uncertainty was evaluated for manufacturing
tolerance in HEU plates, for reproducibility of the control rod position, and for nuclear
data. In the validation estimation of calculated k eff values in the modeling of reference
core materials and core configurations with MCNP6.1 and SCALE6.2/KENO-VI, the
bias in calculated k eff values showed that the difference in the spectrum was about 350
pcm in EE1 core and about 600 pcm in E3 core. Moreover, uncertainty of k eff induced
by nuclear data indicated about 950 pcm for k eff evaluation with a slight variation in
control rod position and core spectrum. In the breakdown of the uncertainty of k eff
induced by nuclear data, the impact of
235 U was significantly dominant in over 90%
for both cores. The sensitivities of Al in HEU plates and in Al sheaths were marked
in fast neutron and resonance regions, leading to large uncertainty about 100 pcm
and 40 pcm in EE1 and E3 cores, respectively. Also, uncertainty was evaluated about
10 and 8 pcm in the tolerance of HEU plates and the reproducibility of control rod
positions, respectively.
References
1. Pyeon CH, Yamanaka M, Ito M et al (2018) Uncertainty quantification of criticality in solidmoderated and -reflected cores at Kyoto University Critical Assembly. J Nucl Sci Technol
55:812
241
Table 8.15 Uncertainty [pcm] of k eff attributed to manufacturing variation in HEU plates in
Table 8.1 and reproducibility of control rods for E3 core (Ref. [2])
Case Enrichment of
235 U
Vertical length Horizontal length Thickness
Reproducibility of
control rod
II-1
13.20 ± 0.11
3.00 ± 0.25
3.09 ± 0.28
8.40 ± 0.41 2.47 ± 3.16
II-2
13.22 ± 0.11
3.15 ± 0.31
3.41 ± 0.35
7.71 ± 0.41 2.90 ± 3.17
II-3
13.27 ± 0.11
3.00 ± 0.2 9
3.19 ± 0.30
8.11 ± 0.41 3.56 ± 317
II-4
13.36 ± 0.11
3.10 ± 0.29.
2.60 ± 0.31
8.04 ± 0.41 6.78 ± 3.14
II-5
13.50 ± 0.11
2.90 ± 0.32
3.03 ± 0.31
7.42 ± 0.41 3.99 ± 3.16
II-6
13.30 ± 0.11
3.08 ± 0.28
2.89 ± 0.32
7.93 ± 0.41 4.10 ± 3.15
the deterministic approach with the covariance data of JENDL-4.0. Sensitivity and
uncertainty analyses demonstrated that the impact of
27 Al and
235 U was remarkably
large in the KUCA A cores, respectively. Moreover, the numerical results revealed
the quantitative evaluation (about 150 pcm) of uncertainty induced by the JENDL4.0 data library in the A cores. Also, these results indicated that further investigation
is needed of the numerical analyses of uncertainty of
27 Al composed mainly of core
components in the A cores, with the use of
27 Al covariance data, in order to assess
the effect of the uncertainty of
27 Al cross sections on reactivity.
To ensure the accuracy of criticality by experimental analyses at KUCA, the
modeling of core configuration was examined through the comparison of excess
reactivity and control rod worth between the calculation and the experiment in hard
and soft spectrum cores. Furthermore, uncertainty was evaluated for manufacturing
tolerance in HEU plates, for reproducibility of the control rod position, and for nuclear
data. In the validation estimation of calculated k eff values in the modeling of reference
core materials and core configurations with MCNP6.1 and SCALE6.2/KENO-VI, the
bias in calculated k eff values showed that the difference in the spectrum was about 350
pcm in EE1 core and about 600 pcm in E3 core. Moreover, uncertainty of k eff induced
by nuclear data indicated about 950 pcm for k eff evaluation with a slight variation in
control rod position and core spectrum. In the breakdown of the uncertainty of k eff
induced by nuclear data, the impact of
235 U was significantly dominant in over 90%
for both cores. The sensitivities of Al in HEU plates and in Al sheaths were marked
in fast neutron and resonance regions, leading to large uncertainty about 100 pcm
and 40 pcm in EE1 and E3 cores, respectively. Also, uncertainty was evaluated about
10 and 8 pcm in the tolerance of HEU plates and the reproducibility of control rod
positions, respectively.
References
1. Pyeon CH, Yamanaka M, Ito M et al (2018) Uncertainty quantification of criticality in solidmoderated and -reflected cores at Kyoto University Critical Assembly. J Nucl Sci Technol
55:812