those effects on the transmutation half-life were surveyed. Finally, a core with pure
Pu supply and 30-day fuel reloading was selected as the reference case for the
scenario analysis. The transmutation half-life was estimated as 24.8 years, meaning
that the amount of Pu is reduced to half after 24.8 years of operation, taking
maintenance and cooling time of spent fuel into account.
In the scenario analysis, once-through scenario of LWR spent fuel was referred to
as a conventional scenario. LWR-MOX utilization with reprocessing of LWR spent
fuel was also considered. As the transmutation scenario, three cases of transmuters
that are only-FR, only-ADS, and both-FR+ADS were analyzed. The numbers of
necessary transmuters were obtained as 15 to 32 units, and the necessary period for
transmutation as 180–240 years. Benefit to the repository by reduction of Pu and MA
was reduction of repository area by a factor of five and of decay time of toxicity by
one order of magnitude. It was shown that MA vitrified in the LWR reprocessing
plant before introduction of the partitioning technology in 2025 considerably deteriorates both benefit. Therefore, early introduction of the partitioning process and
retrievability of MA from vitrified waste should be investigated.
In comparison among transmutation scenarios, reduction of TRU in the ADS
scenario is two times faster than that in the FR scenario. It was found that MA
content in FR fuel in the FR scenario was 15 %, which is much higher than the
design limit of 5 %. On the other hand, the cost of the FR scenario including profit
of electricity generation by transmuter would be much smaller than that of the ADS
scenario because the number of ADSs is double, the accelerator cost is added, and
thermal efficiency of the ADS is worse. Considering high MA content in the FR
scenario, the FR+ADS scenario can be a modest solution, although the ADS
scenario is preferable if rapid transmutation is required regardless of cost.
The present scenario study revealed that the number of the transmuters and time
necessary to transmute Pu and MA in the LWR legacy is considerably large.
However, impact on the TRU amount in the repository related to the nonproliferation issue, repository size, and decay time of the potential radiotoxicity is also
expected to be large. Assessments of increasing cost and risk to operate transmuters
based on the present analysis are the next subject.
Open Access This chapter is distributed under the terms of the Creative Commons Attribution
Noncommercial License, which permits any noncommercial use, distribution, and reproduction in
any medium, provided the original author(s) and source are credited.
Nomenclature
w
Amount of heavy metal (t)
w tr
Transmutation amount (t)
w i
Initial amount (t)
P
Core thermal power (MW)
h ¼
P
w i
Specific heat (MW/t)
230
K. Nishihara et al.
Pu supply and 30-day fuel reloading was selected as the reference case for the
scenario analysis. The transmutation half-life was estimated as 24.8 years, meaning
that the amount of Pu is reduced to half after 24.8 years of operation, taking
maintenance and cooling time of spent fuel into account.
In the scenario analysis, once-through scenario of LWR spent fuel was referred to
as a conventional scenario. LWR-MOX utilization with reprocessing of LWR spent
fuel was also considered. As the transmutation scenario, three cases of transmuters
that are only-FR, only-ADS, and both-FR+ADS were analyzed. The numbers of
necessary transmuters were obtained as 15 to 32 units, and the necessary period for
transmutation as 180–240 years. Benefit to the repository by reduction of Pu and MA
was reduction of repository area by a factor of five and of decay time of toxicity by
one order of magnitude. It was shown that MA vitrified in the LWR reprocessing
plant before introduction of the partitioning technology in 2025 considerably deteriorates both benefit. Therefore, early introduction of the partitioning process and
retrievability of MA from vitrified waste should be investigated.
In comparison among transmutation scenarios, reduction of TRU in the ADS
scenario is two times faster than that in the FR scenario. It was found that MA
content in FR fuel in the FR scenario was 15 %, which is much higher than the
design limit of 5 %. On the other hand, the cost of the FR scenario including profit
of electricity generation by transmuter would be much smaller than that of the ADS
scenario because the number of ADSs is double, the accelerator cost is added, and
thermal efficiency of the ADS is worse. Considering high MA content in the FR
scenario, the FR+ADS scenario can be a modest solution, although the ADS
scenario is preferable if rapid transmutation is required regardless of cost.
The present scenario study revealed that the number of the transmuters and time
necessary to transmute Pu and MA in the LWR legacy is considerably large.
However, impact on the TRU amount in the repository related to the nonproliferation issue, repository size, and decay time of the potential radiotoxicity is also
expected to be large. Assessments of increasing cost and risk to operate transmuters
based on the present analysis are the next subject.
Open Access This chapter is distributed under the terms of the Creative Commons Attribution
Noncommercial License, which permits any noncommercial use, distribution, and reproduction in
any medium, provided the original author(s) and source are credited.
Nomenclature
w
Amount of heavy metal (t)
w tr
Transmutation amount (t)
w i
Initial amount (t)
P
Core thermal power (MW)
h ¼
P
w i
Specific heat (MW/t)
230
K. Nishihara et al.