186
C. H. Pyeon
where
MCNP
Critical,Al→Pb indicates the difference between inverse values of eigenvalue
calculations in the two critical states evaluated by MCNP6.1. Here, the first term in
Eq. (7.4) is defined as “criticality bias” as follows:
MCNP
Critical,Al→Pb =
1
k
MCNP,Al
Critical
−
1
k
MCNP,Pb
Critical
.
(7.5)
By introducing the evaluation methodology of the numerical sample reactivity
worth shown in Eq. (7.3),
MCNP,Al→Pb
Clean,J40 → xxx, yy−zzz is investigated on the numerical
sample reactivity worth as follows, when the nuclear data libraries and isotopes
are varied in the MCNP calculations:
MCNP,Al→Pb
Clean,J40→xxx, yy−zzz =
1
k
MCNP,Al
Clean,J40,All
−
1
k
MCNP,Pb
Clean,J40,All
−
1
k
MCNP,Al
Clean,xxx, yy−zzz
−
1
k
MCNP,Pb
Clean,xxx, yy−zzz
,
(7.6)
where J40 indicates the JENDL-4.0 library, All all the related isotopes and xxx a
suitable choice of three nuclear data libraries: JENDL-3.3 [7], ENDF/B-VII.0 [8]
and JEFF-3.1 [9], yy an isotope and zzz a mass of isotopes.
7.2.2 Lead Sample Reactivity Worth
7.2.2.1 Numerical Simulations
The numerical analyses were conducted with the use of MCNP6.1 together with
the JENDL-3.3, JENDL-4.0, ENDF/B-VII.0 and JEFF-3.1 for transport. For actual
experimental analyses, the capability of eigenvalue calculations by MCNP6.1 was
useful to be discussed with the use of JENDL-4.0 in processing important data
analyses. Also, JENDL-4.0, as a reference library, was compared with the other
nuclear data libraries to reveal its uncertainty.
In the reference core shown in Fig. 7.1, criticality was reached by adjusting the
position of control rod C2 and withdrawing control rods C1 and C3, and safety rods
S4, S5 and S6 from the core, and excess reactivity was deduced with the combined
use of control rod worth (C2) by the rod drop method and its calibration curve by the
positive period method. The measured excess reactivity was within an uncertainty
of 5%, and compared with the numerical one as shown in Table 7.3. The numerical
excess reactivity was obtained by the MCNP6.1 eigenvalue calculations with JENDL4.0 within a statistical error of 2 pcm through 2,000 active cycles of 25,000 histories
and estimated with the use of the two eigenvalue calculations in critical and supercritical states. From a comparison between measured and calculated results shown
C. H. Pyeon
where
MCNP
Critical,Al→Pb indicates the difference between inverse values of eigenvalue
calculations in the two critical states evaluated by MCNP6.1. Here, the first term in
Eq. (7.4) is defined as “criticality bias” as follows:
MCNP
Critical,Al→Pb =
1
k
MCNP,Al
Critical
−
1
k
MCNP,Pb
Critical
.
(7.5)
By introducing the evaluation methodology of the numerical sample reactivity
worth shown in Eq. (7.3),
MCNP,Al→Pb
Clean,J40 → xxx, yy−zzz is investigated on the numerical
sample reactivity worth as follows, when the nuclear data libraries and isotopes
are varied in the MCNP calculations:
MCNP,Al→Pb
Clean,J40→xxx, yy−zzz =
1
k
MCNP,Al
Clean,J40,All
−
1
k
MCNP,Pb
Clean,J40,All
−
1
k
MCNP,Al
Clean,xxx, yy−zzz
−
1
k
MCNP,Pb
Clean,xxx, yy−zzz
,
(7.6)
where J40 indicates the JENDL-4.0 library, All all the related isotopes and xxx a
suitable choice of three nuclear data libraries: JENDL-3.3 [7], ENDF/B-VII.0 [8]
and JEFF-3.1 [9], yy an isotope and zzz a mass of isotopes.
7.2.2 Lead Sample Reactivity Worth
7.2.2.1 Numerical Simulations
The numerical analyses were conducted with the use of MCNP6.1 together with
the JENDL-3.3, JENDL-4.0, ENDF/B-VII.0 and JEFF-3.1 for transport. For actual
experimental analyses, the capability of eigenvalue calculations by MCNP6.1 was
useful to be discussed with the use of JENDL-4.0 in processing important data
analyses. Also, JENDL-4.0, as a reference library, was compared with the other
nuclear data libraries to reveal its uncertainty.
In the reference core shown in Fig. 7.1, criticality was reached by adjusting the
position of control rod C2 and withdrawing control rods C1 and C3, and safety rods
S4, S5 and S6 from the core, and excess reactivity was deduced with the combined
use of control rod worth (C2) by the rod drop method and its calibration curve by the
positive period method. The measured excess reactivity was within an uncertainty
of 5%, and compared with the numerical one as shown in Table 7.3. The numerical
excess reactivity was obtained by the MCNP6.1 eigenvalue calculations with JENDL4.0 within a statistical error of 2 pcm through 2,000 active cycles of 25,000 histories
and estimated with the use of the two eigenvalue calculations in critical and supercritical states. From a comparison between measured and calculated results shown