Korea is exerting efforts to ensure the sustainable use of nuclear power by reducing the substantial inventory of nuclear spent fuel in temporary repositories in nuclear power plants. Against this backdrop, Korea is considering the direct disposal of spent fuel and Pyro-processing, which offers high proliferation resistance. Since Korea’s national policy gives priority to high proliferation resistance, the PWR (Pressurized Water Reactor)-MOX (Mixed OXide (UO2 and PuO2) fuel) method with plutonium extraction is not being considered.
An analysis of economic feasibility, which is the most important factor, must be conducted when comparing direct disposal and Pyro-SFR (Sodium-cooled Fast Reactor). This is because the selection of an alternative cannot be justified without a guarantee of economic feasibility.
Pyro-processing technology is an electrochemical method used to recover uranium and TRU (TRansUranium) from nuclear spent fuel. Because the recovered uranium is utilized as a raw material of SFR fuel [1
], not only does it reduce the inventory of spent fuel, it can also greatly increase the efficiency of disposal.
Therefore, Pyro-processing technology is a future nuclear technology that will generate a sustainable energy source in an economical and environmentally friendly way. Thus, it will enable sustainable nuclear power generation through the Pyro-SFR fuel cycle.
In addition, Pyro-processing economics should include all costs of the Pyro-SFR nuclear fuel cycle, including the cost of SFR capital investment, not just the costs directly related to the Pyro-processing facility [2
]. The cost of capital investment is an important driver of the Pyro-SFR nuclear fuel cycle’s electricity generation cost. In other words, the capital investment cost makes up the largest share of the cost of the Pyro-SFR nuclear fuel cycle. Of course, the cost of SFR capital investment is also an important factor that determines the economics of the alternative to the Pyro-SFR nuclear fuel cycle. However, this capital investment cost relies on estimation because no SFR has yet been commercialized.
To determine Pyro-SFR nuclear fuel cycle economics, the capital investment cost required for SFR and Pyro-processing facility construction needs to be expensed, to factor into the cost of electricity generation [3
]. Here, capital investment cost expensing refers to the process of converting economic resources included in the reactor and Pyro-processing facility, as cost.
For the engineering cost estimation method, it is assumed that the Pyro-processing facility construction period is approximately six to seven years [4
]. The cost that is input every year during the construction period is allocated from the total invested economic resource according to expert judgement. For comparison, the accounting method recognizes the input capital investment cost as a tangible asset [5
]. Then, it is expensed every year utilizing a depreciation cost. Each year, an adequate method is selected among various depreciation methods.
The engineering cost estimation method estimates the capital investment cost of a SFR and Pyro-processing facility that is not yet commercialized, based on the conceptual design. Moreover, in the case of a SFR, data published in the existing literature is utilized to estimate the capital investment cost of reactors with increased capacity using a “scale adjustment” [7
According to previous research, the capital investment cost of a reactor makes up approximately 60% (or more) of the cost of generating electricity [8
]. Moreover, the capital investment cost of a Pyro-processing facility makes up approximately 33% (or more) of the total Pyro-processing cost [9
]. Accordingly, although the share of the Pyro-processing facility capital investment cost is small compared to the reactor cost, the former investment cost cannot be neglected.
In this paper, the following work was carried out to identify the effect of capital investment cost on the cost of electricity generation. First, a method for calculating the nuclear-fuel-cycle cost was introduced; and then the direct disposal option and Pyro-SFR nuclear-fuel-cycle electricity generation costs were calculated. Second, the break-even point of the capital investment cost for the Pyro-SFR nuclear fuel cycle and for direct disposal was calculated, and the economics of the Pyro-SFR nuclear-fuel-cycle was judged.
Among the 24 nuclear power plants in Korea, only 4 have CANDU (CANadian Deuterium Uranium)-PHWRs (Pressurised Heavy Water Reactor). This study focused on PWR (Pressurized Water Reactor) because of the poor economic feasibility of reprocessing by CANDU-PHWR [10
4. Break-Even Point Analysis of the SFR Capital Investment Cost for the Pyro-SFR Nuclear Fuel Cycle Option and the Direct Disposal Option
The capital investment cost makes up the largest share of the Pyro-SFR nuclear fuel cycle electricity generation costs. In other words, the SFR capital investment cost is the most important factor affecting the Pyro-SFR nuclear fuel cycle economics. Accordingly, the break-even point of the SFR capital investment cost was calculated to inform the choice between the Pyro-SFR nuclear fuel cycle and direct disposal options.
It is necessary to consider the reactor cost intentionally in order to ensure sound economics for the Pyro-SFR nuclear fuel cycle. This is because the SFR capital investment cost is known to be higher than the PWR reactor cost [3
The break-even point was calculated using the engineering method. As a result, when the SFR capital investment cost is 4284 US$/kWe or less, as shown in Figure 3
, it was shown that the Pyro-SFR nuclear fuel cycle is comparatively economic compared to the direct disposal option. Here, only the SFR capital investment cost was input as a variable, in order to calculate the break-even point for the SFR capital investment cost, while other costs were assumed to be consistent [26
According to the Hyundai Engineering Company’s SFR 800 MWe capital investment cost estimate (3691 US$/kWe) [2
], is less than the break-even value (4284 US$/kWe). Accordingly, Pyro-SFR nuclear fuel cycle was proven to be more economical than the direct disposal option. However, the nominal value of the SFR capital investment cost reported in the NEA (Nuclear Energy Agency) report was 5032 US$/kWe, it was shown that the capital investment cost is larger than the break-even value (4284 US$/kWe).
One reason that the estimated values of the SFR capital investment cost were different (Hyundai vs. NEA) is because the economic environment (labor cost, price of raw material, construction period, and others) varies by nation. After construction of the first commercialized SFR, an increasingly more accurate normalized capital investment cost can be input for future evaluation of its economics.
5. Conclusions and Implication
The economics of the Pyro-SFR nuclear fuel cycle and direct disposal options was evaluated using the electricity generation cost as the standard. However, the reactor capital investment cost makes up the greatest share of the electricity generation cost. Accordingly, the break-even point of the reactor capital investment cost is important.
The reactor capital cost, accounting for more than 60% of the electricity generation cost [8
], is an important cost driver. Sensitivity analysis was not carried out because the cost of uranium or SWU (Separate Work Unit) costs, which accounts for the highest proportion of nuclear fuel cycle cost, is less than 10% of the electricity generation cost [8
An equilibrium model was used to calculate the electricity generation cost for the direct disposal option and for the Pyro-SFR nuclear fuel cycle option (64.70 and 74.75 mills/kWh, respectively). Accordingly, the difference in the cost of electricity generation between the two options was approximately 10 mills/kWh.
Moreover, the break-even point of the SFR capital investment cost between the Pyro-SFR nuclear fuel cycle and direct disposal option was calculated to be 4284 US$/kWe. Thus, when the SFR capital investment cost is 4284 US$/kWe or less, the analysis shows that the Pyro-SFR nuclear fuel cycle will be comparatively more economical than the direct disposal option.
Hyundai Engineering Company’s SFR 800 MWe capital investment cost estimate (3691 US$/kWe) is less than the break-even value (4284 US$/kWe). Accordingly, the Pyro-SFR nuclear fuel cycle was proven to be more viable economically than the direct disposal option.
However, the nominal SFR capital investment cost reported in the NEA report was 5032 US$/kWe, which is larger than the break-even value (4284 US$/kWe) calculated in this paper. Thus, further design development of the SFR technology is needed to lower the SFR capital investment cost.
The costs calculated in this study are the present costs after discounting for the relevant years. This study calculated the break-even point based on past resources, and compared economic feasibility using the different fast reactor capital costs calculated by Korea and NEA. The Pyro-SFR method has better economic feasibility than direct disposal when using the fast reactor capital cost calculated by Korea, but not so when using the cost calculated by NEA. This can be traced to the differences in economy and the level of construction technology, which determine the construction cost. For instance, Korea’s construction cost for light water reactors is the lowest in the world.
In making a decision between direct disposal and Pyro-SFR, the various factors to be taken into account include economic feasibility, public acceptance, international dynamics, national policy, and environmental pollution. Among these factors, this study focused on economic feasibility, which is regarded as the most important. The final outcome may be different if sustainability and other factors are included in the evaluation criteria, in addition to economic feasibility.
In addition, the aspect of economic feasibility is necessary to judge an optimized fuel cycle alternative. This is because the best fuel cycle option can be elicited through the evaluation of multi-criteria, such as safety and technology, environmental impact, economic feasibility, proliferation resistance, social factors (including public acceptance), etc.
To estimate the fuel cycle costs, the construction cost of a HLW (high-level waste) repository in the future and the disposal cost must be considered to estimate the fuel cycle costs. In Korea, the objects of disposal cost are limited to the deep geological repository covering PWR-spent fuel on the assumption that the PWR’s initial enrichment is 4.5% and its burn-up is 55 GWD/MTU. In addition, the cooling time is assumed to last for 10 years [14
]. To decrease the uncertainty, the actual disposal cost of KRS (Korea Reference System) to dispose HLW (high-level waste) will be considered in the future.
Compared to direct disposal, the Pyro-SFR method presents the following advantages. First, the Pyro-SFR method is more likely to be accepted by the public. In Korea, it is difficult to acquire repositories for high-level radioactive waste because of the limited land and high population density. Second, Pyro-SFR is associated with high proliferation resistance, which is favorable in terms of international dynamics and national policy. Since Pyro-SFR cannot be used to extract plutonium during the recycling process, it has higher proliferation resistance than PUREX (Plutonium-URanium EXtraction), which involves easier reprocessing of plutonium. Third, this method is more environmentally friendly. Due to the significant decrease in disposal amount, Pyro-SFR does not require disposal sites to be as large, thus posing less of the environmental risks that may arise from earthquakes or leakage. Ultimately, the Pyro-SFR method is superior to direct disposal in terms of the sustainability of nuclear power. As such, Pyro-SFR is likely to be a feasible method even if factors other than economic feasibility are considered.
It should be noted that this analysis is limited in the sense that the value of the SFR capital investment cost estimated based on the conceptual design was used as the input data. After the first commercialized SFR is constructed, a more accurate analysis on the economics of the nuclear fuel cycle option should be possible.