Calculations have been done for two kinds of transmutation target. In case 1, the
transmutation target was the MA hydride of (MA 0.1 , Zr 0.9 )H 1.6 . Calculation with
metal MA 0.1 Zr 0.9 target without H was done in case 2. The results of calculations
are summarized in Table 16.3, where effective half-life is defined as the time such
that the residual amount of MA is decreased to half of the MA loaded during the
burn-up. The effective half-life is calculated to be 2.19 years in case 1 and
8.07 years in case 2, mainly because of the softened spectrum effect induced by
the MA-hydride. The transmutation rate of the MA-hydride target is about three
times higher than that of the MA-metal target. Figure 16.4 shows the change of total
MA and each element of MA in the MA-hydride target with increase of time. Major
elements in MA, that is, Np and Am are decreased simultaneously during the burnup. The contribution of long-lived Cm (
245 Cm and
246 Cm) is much smaller than that
of Np and Am. The change of total MA in the MA-metal target is also shown in
Fig. 16.4 for comparison.
The major mode of the transmutation in the present method is not fission but
neutron capture (see Table 16.3). As shown in Fig. 16.5, Am and Np are mainly
transmuted to Pu because of neutron capture, beta decay, and alpha decay. Recycled
Pu is used as a driver fuel in this reactor.
Table 16.2 Calculation method for MA transmutation
Items
Methods
Notes
Computation
method
Three-dimensional continuation
energy Monte Carlo analysis code;
MVP (burn-up routine is
MVP-BURN)
1,200,000 neutron histories with
120 batches. Initial 20 batches are run
to establish the initial neutron source
distribution
Nuclear data JENDL-4.0 library
Calculation
model
Pin heterogeneous model
Table 16.3 Comparison of reduction ratio of MAs
Target
Loading
mass (kg)
Reduction mass
(kg/year)
Reduction ratio
after 1 year
Effective half life
(year)
Case1:
MA-hydride
335
91.1 (33.0)
a
0.272
2.19
Case2:
MA-metal
335
27.6 (9.4)
a
0.082
8.07
Ratio: Case1/
Case2
1.00
3.30
3.30
0.27
a
Values in parentheses are reduction masses by fissions
16 Enhancement of Transmutation of Minor Actinides by Hydride Target
173
transmutation target was the MA hydride of (MA 0.1 , Zr 0.9 )H 1.6 . Calculation with
metal MA 0.1 Zr 0.9 target without H was done in case 2. The results of calculations
are summarized in Table 16.3, where effective half-life is defined as the time such
that the residual amount of MA is decreased to half of the MA loaded during the
burn-up. The effective half-life is calculated to be 2.19 years in case 1 and
8.07 years in case 2, mainly because of the softened spectrum effect induced by
the MA-hydride. The transmutation rate of the MA-hydride target is about three
times higher than that of the MA-metal target. Figure 16.4 shows the change of total
MA and each element of MA in the MA-hydride target with increase of time. Major
elements in MA, that is, Np and Am are decreased simultaneously during the burnup. The contribution of long-lived Cm (
245 Cm and
246 Cm) is much smaller than that
of Np and Am. The change of total MA in the MA-metal target is also shown in
Fig. 16.4 for comparison.
The major mode of the transmutation in the present method is not fission but
neutron capture (see Table 16.3). As shown in Fig. 16.5, Am and Np are mainly
transmuted to Pu because of neutron capture, beta decay, and alpha decay. Recycled
Pu is used as a driver fuel in this reactor.
Table 16.2 Calculation method for MA transmutation
Items
Methods
Notes
Computation
method
Three-dimensional continuation
energy Monte Carlo analysis code;
MVP (burn-up routine is
MVP-BURN)
1,200,000 neutron histories with
120 batches. Initial 20 batches are run
to establish the initial neutron source
distribution
Nuclear data JENDL-4.0 library
Calculation
model
Pin heterogeneous model
Table 16.3 Comparison of reduction ratio of MAs
Target
Loading
mass (kg)
Reduction mass
(kg/year)
Reduction ratio
after 1 year
Effective half life
(year)
Case1:
MA-hydride
335
91.1 (33.0)
a
0.272
2.19
Case2:
MA-metal
335
27.6 (9.4)
a
0.082
8.07
Ratio: Case1/
Case2
1.00
3.30
3.30
0.27
a
Values in parentheses are reduction masses by fissions
16 Enhancement of Transmutation of Minor Actinides by Hydride Target
173