Result of LWR-PuT

In MOX scenarios, the Rokkasho reprocessing plant (RRP) will be operated with annual capacity of 800 t and a MOX fabrication plant also (Fig. 19.6). The total amount of UO2-SF reprocessed is 34,500 tHM, slightly larger than the planned amount of 32,000 tHM. Thus, the present analysis assumes an extension of the RRP by several years. The MOX loading to a usual LWR is limited to 30 %, although the

Fig. 19.5 Result of LWR-OT scenario

Ohma full-MOX reactor starting in 2014 in this analysis can be operated only by MOX fuel. Because the RRP is operated after all LWRs are closed, part of the separated Pu cannot be burned. The total amount of Pu is reduced to 250 t, but that of MA is increased to 100 t.

Result of FR

In the FR scenario as well as other transmutation scenarios, Pu from the RRP is at first fabricated as LWR-MOX fuel and burned in LWR. Pu is co-extracted with same content of U in the current RRP, although MA is vitrified as waste. MA partitioning is assumed to be introduced in 2025 and stored until 2045. In 2045, before introduction of transmuters in 2050, reprocessing of LWR-MOX spent fuel will begin and provide Pu to the transmuters.

FRs are to be introduced in 2050 when 250 t plutonium and 100 t MA remains.

MA of 20 t is vitrified by the RRP before 2025 and is not available for transmutation. Available TRU is 330 t. The required TRU to introduce an FR is approximately 25 t, if we assume 41 % of Pu content and 15 % of MA content and employ

45.1 t from Table 19.10. Theoretically, 14 (ΒΌ350/25) FRs can be introduced in 2050, but only 8 can be deployed in practice because the plant life of an FR is assumed to be 60 years and sufficient TRU must be kept until 2110. Available TRU gradually decreases to 200 t in 2110 by transmutation. After 2110, FRs are replaced and reduced to 3 units corresponding to available TRU of 200 t that decreases to 130 t in 2170. Then, 2 FRs from 2170 to 2230 and 2 FRs from 2230 to 2290 will be deployed. After four generations of transmutation, the amounts of Pu and MA are reduced to 40 and 30 t, respectively.

MA content of FR is as high as 15 % (Fig. 19.7), which is above the design limit of 5 % in Wakabayashi et al. [1]. In the usual design of FBRs, MA accumulation is mitigated by a supply of fresh Pu from the blanket. Moreover, high Pu content of FR burner contributes to high MA content. High MA content generally causes deterioration of safety parameters (beta, Doppler coefficient, void reactivity) and difficulty in a reprocessing and fabrication plant.

Result of ADS

In the ADS scenario, transmuter is changed from FR to ADS. ADS can accept both Pu and MA; distribution is shown in Fig. 19.8. In 2050, 22 ADSs are to be introduced, corresponding to 140 t available TRU. Then, 7 and 3 ADSs are operated respectively from 2110 to 2170 and 2170 to 2230. After three generations, Pu and MA are reduced to 10 t and 3 t, respectively, excluding 16 t MA in vitrifi waste.

Result of FR+ADS

In the FR+ADS scenario, MA content in FR is limited below 5 % with respect to design limit and the remaining MA is transmuted in the ADS. In the first generation of transmutation from 2050 to 2110, six FRs and three ADSs are deployed, then three FRs and two ADSs in the second generation, and two FRs and one ADS in the third generation are built (Fig. 19.9). In the fourth generation, only ADS is utilized as to reduce TRU rapidly. The total amount of Pu and MA is reduced to 20 and 10 t, respectively, excepting MA in vitrified waste.

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