190
C. H. Pyeon
around 10 pcm, and resulted in a markedly high accuracy of C/E values, as shown
in Table 7.6.
7.2.2.4 Discussion
Special attention was paid to the second term in Eq. (7.4) to investigate the difference
between JENDL libraries mentioned in Sect. 7.2.2.3. The second term in Eq. (7.4) was
significantly demonstrated in actual sample reactivity by the MCNP analyses, as well
as by the experiments, and the bias between JENDL-4.0 and the other libraries were
studied with a new definition, as shown in Eq. (7.6): contribution of individual isotope
to sample reactivity. In the analyses of differences defined in Eq. (7.6), JENDL-4.0
was selected as the reference library, and the sample reactivities in clean cores were
obtained, as shown in Figs. 7.9a, d along with four cases in Fig. 7.5, respectively,
when the libraries and isotopes were varied separately: core composition materials
of Pb isotopes,
27 Al,
235 U and
238 U in the fuel rod of the core.
A comparison between the two JENDL libraries showed a significant effect on
the reactivity resulting from large differences among all Pb isotopes (
204 Pb,
206 Pb,
207 Pb and
208 Pb), regardless of the magnitude of sample reactivity: especially from
those of
206 Pb and
207 Pb; contrary to that among the others (
27 Al,
235 U and
238 U).
Regarding the discussion between the two JENDL libraries, the reason for total
difference was attributable mainly to those of all Pb isotopes through the analyses of
differences in Eq. (7.6). As discussed in previous studies [11, 12], this fact provided
valuable knowledge that an improvement of the inelastic scattering cross sections
around a few MeV neutron energy region of
206 Pb and
207 Pb had been pointed out
importantly in the difference between JENDL-3.3 and JENDL-4.0 libraries through
the analyses of the Pb void reactivity in the JAEA ADS model [10] and of the Pb
reflector effect on SEG experiments through JENDL-4.0 benchmarks [12]. From the
results of ENDF/B-VII.0, a small effect of the difference was compared inversely
with that in JENDL-4.0 about 20 pcm in all cases, with regard to Pb isotopes and
27 Al, but not to
235 U and
238 U, although the total difference between JENDL-4.0 and
ENDF/B-VII.0 was slight.
Furthermore, while a difference about 20 pcm was found in
238 U and
27 Al of
Cases 2 and 4, respectively, the difference between JENDL-4.0 and JEFF-3.1 was
considered notably minor within the allowance of relative errors.
On the basis of these observations, a library update from JENDL-3.3 to JENDL4.0 was demonstrated by the fact that the difference between Pb isotopes of the
two JENDL libraries was dominant in the comparative study, through the numerical
analyses of sample reactivity by the MCNP approach. Moreover, JENDL-4.0 revealed
a slight difference from ENDF/B-VII.0 in all the Pb isotopes to
27 Al, and from
JEFF-3.1 in
238 U to
27 Al.
C. H. Pyeon
around 10 pcm, and resulted in a markedly high accuracy of C/E values, as shown
in Table 7.6.
7.2.2.4 Discussion
Special attention was paid to the second term in Eq. (7.4) to investigate the difference
between JENDL libraries mentioned in Sect. 7.2.2.3. The second term in Eq. (7.4) was
significantly demonstrated in actual sample reactivity by the MCNP analyses, as well
as by the experiments, and the bias between JENDL-4.0 and the other libraries were
studied with a new definition, as shown in Eq. (7.6): contribution of individual isotope
to sample reactivity. In the analyses of differences defined in Eq. (7.6), JENDL-4.0
was selected as the reference library, and the sample reactivities in clean cores were
obtained, as shown in Figs. 7.9a, d along with four cases in Fig. 7.5, respectively,
when the libraries and isotopes were varied separately: core composition materials
of Pb isotopes,
27 Al,
235 U and
238 U in the fuel rod of the core.
A comparison between the two JENDL libraries showed a significant effect on
the reactivity resulting from large differences among all Pb isotopes (
204 Pb,
206 Pb,
207 Pb and
208 Pb), regardless of the magnitude of sample reactivity: especially from
those of
206 Pb and
207 Pb; contrary to that among the others (
27 Al,
235 U and
238 U).
Regarding the discussion between the two JENDL libraries, the reason for total
difference was attributable mainly to those of all Pb isotopes through the analyses of
differences in Eq. (7.6). As discussed in previous studies [11, 12], this fact provided
valuable knowledge that an improvement of the inelastic scattering cross sections
around a few MeV neutron energy region of
206 Pb and
207 Pb had been pointed out
importantly in the difference between JENDL-3.3 and JENDL-4.0 libraries through
the analyses of the Pb void reactivity in the JAEA ADS model [10] and of the Pb
reflector effect on SEG experiments through JENDL-4.0 benchmarks [12]. From the
results of ENDF/B-VII.0, a small effect of the difference was compared inversely
with that in JENDL-4.0 about 20 pcm in all cases, with regard to Pb isotopes and
27 Al, but not to
235 U and
238 U, although the total difference between JENDL-4.0 and
ENDF/B-VII.0 was slight.
Furthermore, while a difference about 20 pcm was found in
238 U and
27 Al of
Cases 2 and 4, respectively, the difference between JENDL-4.0 and JEFF-3.1 was
considered notably minor within the allowance of relative errors.
On the basis of these observations, a library update from JENDL-3.3 to JENDL4.0 was demonstrated by the fact that the difference between Pb isotopes of the
two JENDL libraries was dominant in the comparative study, through the numerical
analyses of sample reactivity by the MCNP approach. Moreover, JENDL-4.0 revealed
a slight difference from ENDF/B-VII.0 in all the Pb isotopes to
27 Al, and from
JEFF-3.1 in
238 U to
27 Al.