N-batch core can reduce k eff drop by 1/N, that is, a drop of 14 %dk can be reduced to
2.3 %dk by six-batch design. Figure 19.4 illustrates the criticality change with an
expansion for operation date of 0–1,200 days. The criticality drop for the early
operation date is larger than the limit of 3 %dk, that is, 0.94 of k eff at end of burn-up;
the drop decreases in the equilibrium cycle. The maximum drop is 5 %dk for
Pu-ADS and 6.5 %dk for Pu+U ADS, which can be compensated by control rods
or burnable poison or mitigated by shorter operation in the early cycle in future
improvements. The drop in the equilibrium cycle is approximately 2 %dk, which is
comparable to that of the reference MA-ADS.
Volume fractions and inventories are listed in Table 19.6. Six-batch cores
generally require more inventory than a one-batch core because an averaged k eff
during operation of multi-batch cores is higher than that of the one-batch core.
Transmutation amounts of Pu- and Pu+U-ADSs are much smaller than that of the
MA-ADS because the operation period is, respectively, only 50 and 100 days.
To evaluate transmutation half-life, operation and cycle efficiencies must be
determined. The short operation period of 50 or 100 days implies frequent fuel
exchange and low operation efficiency. There are two kinds of interval: fuel
exchange and plant maintenance. We assumed that fuel exchange of a 1/6 core
requires 15, 30, or 60 days for the Pu- and Pu+U-ADS and that plant maintenance
including accelerator needs 60 days. Because fuel exchange for 15 days is very
short, considering shutdown and startup of the ADS plant is included, tentative
storage inside a core vessel should be applied for such a short interval. In the case of
Pu-ADS, the 50-day operation and 15-, 30-, or 60-day interval are repeated five
times, then 50-day operation and 60-day maintenance are done. In the case of Pu
+U-ADS, 100-day operation and 15-, 30-, or 60-day interval are repeated two times,
then 100-day operation and 60-day maintenance are done. The total operation
period before a long plant maintenance of 60 days in both ADSs is 300 days.
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
0
600
1200
1800
2400
3000
3600
4200
4800
5400
6000
Criticality, keff
Operation day
MA
Pu
Pu+U
Fig. 19.3 Time evolution of criticality for one-batch design
214
K. Nishihara et al.
2.3 %dk by six-batch design. Figure 19.4 illustrates the criticality change with an
expansion for operation date of 0–1,200 days. The criticality drop for the early
operation date is larger than the limit of 3 %dk, that is, 0.94 of k eff at end of burn-up;
the drop decreases in the equilibrium cycle. The maximum drop is 5 %dk for
Pu-ADS and 6.5 %dk for Pu+U ADS, which can be compensated by control rods
or burnable poison or mitigated by shorter operation in the early cycle in future
improvements. The drop in the equilibrium cycle is approximately 2 %dk, which is
comparable to that of the reference MA-ADS.
Volume fractions and inventories are listed in Table 19.6. Six-batch cores
generally require more inventory than a one-batch core because an averaged k eff
during operation of multi-batch cores is higher than that of the one-batch core.
Transmutation amounts of Pu- and Pu+U-ADSs are much smaller than that of the
MA-ADS because the operation period is, respectively, only 50 and 100 days.
To evaluate transmutation half-life, operation and cycle efficiencies must be
determined. The short operation period of 50 or 100 days implies frequent fuel
exchange and low operation efficiency. There are two kinds of interval: fuel
exchange and plant maintenance. We assumed that fuel exchange of a 1/6 core
requires 15, 30, or 60 days for the Pu- and Pu+U-ADS and that plant maintenance
including accelerator needs 60 days. Because fuel exchange for 15 days is very
short, considering shutdown and startup of the ADS plant is included, tentative
storage inside a core vessel should be applied for such a short interval. In the case of
Pu-ADS, the 50-day operation and 15-, 30-, or 60-day interval are repeated five
times, then 50-day operation and 60-day maintenance are done. In the case of Pu
+U-ADS, 100-day operation and 15-, 30-, or 60-day interval are repeated two times,
then 100-day operation and 60-day maintenance are done. The total operation
period before a long plant maintenance of 60 days in both ADSs is 300 days.
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
0
600
1200
1800
2400
3000
3600
4200
4800
5400
6000
Criticality, keff
Operation day
MA
Pu
Pu+U
Fig. 19.3 Time evolution of criticality for one-batch design
214
K. Nishihara et al.