Summary of EU scenarios with transmutation option for nuclear phase out and continued nuclear scenarios

3.3.1.1. Introduction

The study analyses EU scenarios with transmutation options for nuclear phase out and continued nuclear scenarios based on the EC Framework Programme projects Impact of Partitioning, Transmutation and Waste Reduction Technologies on the Final Nuclear Waste Disposal (RED-IMPACT), Partitioning and Transmutation European Roadmap for Sustainable Nuclear Energy (PATEROS) and ADS and Fast Reactor Comparison Study (ARCAS).

The RED-IMPACT project [3.54] studied the impact of partitioning and transmutation, conditioning and waste reduction technologies on reducing the burden associated with radioactive waste management and disposal.

The project focused on realistic evaluation of partitioning and transmutation technologies which can be deployed on an industrial level or based on future developments that take into account inventory of existing and foreseen nuclear fuel facilities in Europe.

The PATEROS project established a global partitioning and transmutation roadmap leading up to the industrial scale deployment of necessary facilities at the European level.¹² A common objective of all strategies using partitioning and transmutation is to reduce the burden on a long term waste management, in terms of radiotoxicity, volume and heat load of HLW, which has to be disposed of in final repositories. Possible strategies can range from using dedicated transmuters in a separate fuel cycle stratum in a stable or expanding nuclear energy scenario in order to reduce drastically the amount of nuclear waste sent to the repository, down to the scenario of a nuclear phase out.

The ARCAS project supports the Sustainable Nuclear Energy Technology Platform (SNETP) Strategic Research Agenda [3.55]. It compared, on a technological and economic basis, accelerator driven systems (ADSs) and fast reactors as minor actinide burners. The economic impact of both options was evaluated for investment cost and operational cost, but not for R&D cost requirements. The project considered technological maturity and how this can be incorporated in the economic analysis.

This study falls within the framework of SYNERGIES Task 3, evaluation of options for minor actinide management, providing technical and economical assessment and comparison of fast reactors and ADSs for transmutation of minor actinides at a European level. Examination of collaborations among European countries also contributed to Task 1, on evaluation of synergistic collaborative scenarios of fuel cycle infrastructure development, for example considering scenarios for sharing of facilities and services and identifying timeframes for required infrastructure introduction and expansion in different stages of the nuclear fuel cycle. The complete case study can be found in Annex XXIV on the CD-ROM accompanying this publication.

3.3.1.2. Objective and problem formulation

One of the main tasks of the RED-IMPACT project was to select representative fuel cycle scenarios to explore the impact of partitioning and transmutation technologies on the overall waste management, and specifically on a final HLW repository [3.54]. The PATEROS project had the objective of establishing a European vision for deployment of partitioning and transmutation of nuclear waste which can contribute to the deployment of sustainable nuclear energy. A regional approach was adopted to implement the innovative fuel cycles associated with partitioning and transmutation in Europe addressing the impact of different strategies in various countries. The ARCAS study aimed to compare, on a technological and economical basis, ADSs and fast reactors as minor actinide burners [3.55]. It is split into five work packages: the reference scenario definition, the fast reactor system definition, the ADS definition, the fuel reprocessing and fabrication facilities definition, and the economical comparison.

12 For further information on the PATEROS project and the deliverables of the Sixth Framework Programme, see http://pateros.sckcen.be

FIG. 3.97. Levelized fuel cycle unit costs for the reference

approach. FIG. 3.98. Levelized fuel cycle unit costs for the international

approach.

3.3.1.3. Assumptions, methods, codes and input data used

Reference [3.54] reports that the scenarios that were addressed in the RED-IMPACT project ranged from direct disposal of the spent fuel to fully closed cycles with fast neutron reactors or ADSs. Both equilibrium and transition analyses have been applied to those scenarios. The choice of scenarios was based on a comprehensive representation of waste streams appearing in scenarios discussed in different EU Member States. The indicators assessed included “total radioactive and radiotoxic inventory, discharges during reprocessing, thermal power and radiation emission of the waste packages, corrosion of matrices, transport of radioisotopes through the engineered and geological barriers or the resulting doses from the repository” [3.54]. The selected scenarios included several industrial scenarios in which both equilibrium and transition options were investigated:

— Scenario A1 using LWR reactors, UO₂ and once through cycle;

— Scenario A2 with LWR reactors and UO₂ + MOX (once plutonium recycling);

— Scenario A3 with introduction of fast spectrum only for plutonium reuse and innovative scenarios;

— Scenario B1 representing a Generation IV solution based on an integral fast reactor;

— Scenario B2, similar to A2 but with the introduction of ADSs in a second stratum for transmutation of remaining plutonium and minor actinides;

— Scenario B3, a double state scenario with LWR (UO₂ + MOX) and fast reactor in first stratum and ADSs with minor actinide burning in second stratum.

The PATEROS project considered implementation of partitioning and transmutation and advanced fuel cycles on a regional European level. It studied the possibilities to share fuel cycle facilities and to envisage the optimized use of resources and investments for developing sustainable nuclear energy at a regional level. To provide a regional perspective consideration, countries have been grouped as follows:

— Group A: Stagnant or phase out; focus on spent fuel management.

— Group B: Continuation scenario with focus on optimization of plutonium for future deployment of fast reactors or ADSs.

— Group C: Subset of Group A, after stagnation, envisages a nuclear ‘renaissance’.

— Group D: Initially no nuclear power, decides to go for nuclear energy in the future.

Four different scenarios based on the use of fast spectrum reactors and ADSs are studied. Scenarios 1 and 2 considered deployment of ADSs shared by country Groups A and B. ADSs will use the plutonium of Group A and transmute minor actinides of both groups. Plutonium of Group B is either mono-recycled in PWRs and then stored for future deployment of fast reactors (Scenario 1) or continuously recycled in PWRs (Scenario 2).

Scenario 3 considered deployment of a group of fast reactors in Group B using plutonium from Groups A and B with the objective of decreasing stock of spent fuel of Group A. Scenario 4 assumed some selected countries decided to relaunch nuclear energy with fast reactors, while other countries continue with their objective of waste minimization. The PATEROS simplified flow scheme is given in Fig. 3.99. The transmuter uses plutonium of Group A and transmutes the minor actinides of the two groups.

The reference scenario considered in the framework of the ARCAS project [3.55] refers to the PATEROS project where a regional scenario, at a European level, was analysed in detail.¹³

In the Collaborative Project for a European Sodium Fast Reactor (CP–ESFR), a ‘working horse’ SFR design was elected (actually a basic SFR concept), and its parameters were then optimized to improve reactivity coefficients [3.56]. A short description of the optimized reactor concept is provided in Annex XXIV on the CD-ROM accompanying this publication.

3.3.1.4. Summary presentation and analysis of the results

The material balances for plutonium and minor actinides have been calculated for all RED-IMPACT scenarios. It has been shown that the production of plutonium and minor actinides could be reduced by using an

13 Further information is available from https://cordis.europa.eu/result/rcn/57137_en.html

FIG. 3.99. Simplified flow chart used in the PATEROS project.

inert matrix or thorium matrix fuel in LWR type reactors. When plutonium is multi-recycled in LWRs, the amount of generated plutonium waste would be 5–10 times less compared to the case of plutonium mono-recycling, while an increase by a factor of 3–7 would be observed in the amounts of americium and curium. Modelling of the transition scenarios from the current reactor fleet to a final equilibrium state has shown that it is not possible to ignore the radiotoxic inventory of the HLW produced before the deployment of partitioning and transmutation.

Fastest possible deployment of partitioning and transmutation could secure a true reduction of the total radiotoxic inventory of HLW in geological disposal. When caesium and strontium are also separated in the partitioning and transmutation cycle, this helps to achieve minimum thermal output of HLW allowing a substantial reduction in the repository size.

The main results of the PATEROS regional partitioning and transmutation Scenarios 1 and 2 can be summarized as follows. The stock of spent nuclear fuel in Group A can reach 0 by 2100, as all the fuel will be reprocessed by then. The plutonium inventory available by the end of the century for future fast reactors in Scenario 1 will be 840 t. The Scenario 2 simulation indicates the main stock of plutonium inventory for Group B to be stabilized at 100 t by 2100. In this, the total inventory would increase slightly over time owing to the accumulation of ‘bad quality’ plutonium produced during MOX multi-recycling, which also has less minor actinide production by radioactive decay with respect to plutonium mono-recycling.

For the proposed transmutation strategy, a total reprocessing capacity of 3700 t per year in Scenario 1 and 3300 t per year in Scenario 2 are needed. The reprocessing capacity for PWR fuel as needed in Scenario 1 is around 18% higher than that available in France currently. When it comes to the ADS reprocessing facilities, they would need to be developed and deployed in the future. The requirements for fuel fabrication capacity are as follows:

(i) Scenario 1:

— 1000 t/year for UOX;

— 100 t/year for MOX;

— 30 t/year for ADSs.

(ii) Scenario 2:

— 690 t/year for UOX;

— 390 t/year for MOX;

— 40 t/year for ADSs.

The requirements for the two scenarios presented above appear quite similar, with only the proportion of MOX/UOX fabrication capacities being notably different (1:10 and 1:1.77, correspondingly).

FIG. 3.99. Simplified flow chart used in the PATEROS project.

As a final consideration on the European Facility for Industrial Transmutation (EFIT) design, it should be mentioned that a transmuter of such a type might have benefits in regional scenarios. However, it would hardly be suitable for countries phasing out nuclear energy and implementing a partitioning and transmutation strategy in isolation. The plain reason for this is that transmutation addresses exclusively minor actinides and leaves most of the plutonium stocks unchanged.

The analysis performed in the PATEROS project for Scenarios 3 and 4 concluded that a regional approach with fast reactors used either as breeders or just as burners can make it possible to manage both plutonium and minor actinides originating from a number of countries. In this, the flexibility of a fast reactor providing for its easy conversion, at a desired point of time, from a breeder to burner and vice versa will be useful to reduce the radiotoxic HLW in both considered groups of countries. Moreover, the added value of the fast reactors compared to the ADS would be the electricity produced.

The ARCAS study [3.55] tries to address crucial issues in the partitioning and transmutation debate: which options are technologically feasible, and at what price. As a contractual service agreement project, it does not aim to perform R&D in the field, but rather to gather the available information and combine it in a global study. At the moment, the inventory and feedstock of minor actinides has been established and the reference fast reactor system and ADS have been defined. The fuel reprocessing and fuel fabrication facilities are being assessed and their choice finalized.

TABLE 3.24. PROPOSED REFERENCE MINOR ACTINIDE COMPOSITION

Nuclide Content (%)

Am²⁴¹ 39.55

Am^242m 0.22

Am²⁴³ 22.34

Np²³⁷ 32.91

Cm²⁴³ 0.059

Cm²⁴⁴ 3.97

Cm²⁴⁵ 0.95

Note: Minimum minor actinide annual stream (PATEROS scenario) is 2.3 t/year; maximum minor actinide annual stream (PATEROS extended to all European countries with present energy production) is 6.5 t/year.

TABLE 3.25. COMPARISON OF LWR, FR AND ADS COST ADVANTAGES AND DISADVANTAGES

LWR Fast reactor ADS

Construction cost + − −−

Operation and maintenance cost + − −−

Fuel costs +/− −

MA transmutation capacity −− + ++

Note: ++ high advantages; + medium advantages; +/− both advantages and disadvantages; − medium disadvantages; −− high disadvantages.

The outcome of the simulations addressed the minor actinide streams (and their isotopic composition) evaluation from Group A (i.e. coming from a spent fuel storage after some decay time) and Group B (i.e. coming from a continuous feed from a PWR fleet) is shown in Table 3.24.¹⁴

Both fast reactors and ADSs have transmutation capabilities. As expected from their fuel loadings and spectra, the project work packages 2 and 3 have demonstrated that ADSs have a superior capability for transmutation compared to fast reactors. Furthermore, the required transport of spent fuel and dedicated burner fuel can be limited because of the high concentration of minor actinides in ADS fuel. The challenging question is whether these advantages could compensate for the extra difficulties and then costs of building these facilities. Table 3.25 shows the cost advantages and disadvantages for the three reactor systems considered.

3.3.1.5. Conclusions

With reasonable exploration of present technologies, partitioning and transmutation will allow largely reducing the long term burden of the spent fuel and HLW, and can thus contribute to significantly improving its management. Residual heat of HLW can be reduced though partitioning and transmutation of plutonium and minor actinides. This will make it possible to use galleries 3–6 times shorter in an underground geologic repository. In turn, this would help to reduce the footprint and the number of repository sites.

Transmutation can be accomplished efficiently either in ADSs or in fast reactors, or through a system based on a combination thereof. While dealing with HLW, the issue of ILW and, specifically, of the long lived ILW, should not be discarded as, with partitioning and transmutation in place, the radiotoxicity of such ILW would actually be definitive.

The PATEROS project concluded that regional strategies can provide a framework for implementation of innovative fuel cycles, with appropriate share of efforts and resources optimization. This project also outlined the ADS characteristics that would fit best to minor actinide transmutation in ‘double strata’ type scenarios.

The ADS was found mostly adapted to minor actinides and not transuranics. Therefore, the best mode of its application appears to be within a regional scenario where different countries would collaborate in the use of facilities, resources and inventories towards waste minimization. However, the same type of ADS will not be useful in the case of a country committed to a stagnant or decreasing use of nuclear energy that could decide to deploy partitioning and transmutation in ‘isolation’ for waste management.

Within the PATEROS project, it was also noted that implementation of partitioning and transmutation at a regional level (with a potential to reduce radiotoxicity of the disposed HLW below that of natural uranium ore after several hundreds of years) could be of benefit to all countries in the region (all 34 European countries) irrespective of which policy regarding nuclear each country is pursuing. It was also noted that regional partitioning and transmutation could perhaps even facilitate pro-nuclear decision making in some countries.

The ARCAS project tried to address crucial issues in the partitioning and transmutation debate: which options are technologically feasible and at what price. The final report summary¹⁵ states that the ARCAS project has investigated:

“The dependence of the economic performance of a transmutation facility from the electricity price.... If the electricity price is low, the economic performance of ADS–EFIT and EFR are comparable only for very good EFR transmutation performances, while for high electricity prices EFR is more convenient than ADS–EFIT. In case standard values are considered there is no net economical convenience in the adoption of one particular system.

“When looking at the costs of electricity nuclear power plant fleets including FR and ADS respectively, the results of the comparison of these costs depend strongly on their relative costs. The increased costs of electricity produced by ADS may be balanced by its limited share in the energy mix and the bigger share of lower cost kW·h produced by LWR.”

14 Further information is available at https://cordis.europa.eu/result/rcn/57137_en.html

15 Available at https://cordis.europa.eu/result/rcn/57137_en.html TABLE 3.24. PROPOSED REFERENCE MINOR

ACTINIDE COMPOSITION

Note: Minimum minor actinide annual stream (PATEROS scenario) is 2.3 t/year; maximum minor actinide annual stream (PATEROS extended to all European countries with present energy production) is 6.5 t/year.

TABLE 3.25. COMPARISON OF LWR, FR AND ADS COST ADVANTAGES AND DISADVANTAGES

LWR Fast reactor ADS

Construction cost + − −−

Operation and maintenance cost + − −−

Fuel costs +/− −

MA transmutation capacity −− + ++

Note: ++ high advantages; + medium advantages; +/− both advantages and disadvantages; − medium disadvantages; −− high disadvantages.

Determination of the break-even price of ADSs that would make the ADS scenario competitive compared to the fast reactor scenario was found to be a complex task [3.55]. Having in mind the very low level of readiness of key nuclear technologies addressed in ARCAS, the cost models used might not represent adequately the actual future costs of such technologies. In this context one could also note that ADSs are not being designed for electricity generation. This being said, electricity cost was found to be the only parameter to compare the different scenarios unambiguously. To make it work, the ARCAS concluded that:

“one can consider the extra electricity cost for MA burning as the ‘price’ to be paid for minor actinide recycling and transmutation. The over-cost can then be viewed within the advantage of added sustainability of the closed fuel cycle, that recycles all its minor actinides, as well as from the viewpoint of reduction of long-lived nuclear waste.”

3.3.2. Preliminary analysis of the nuclear energy development scenarios based on U–Pu multi-recycling in