OECD countries with ongoing nuclear energy programs

Objective drivers Means to meet the objectives Technology requirements Enhance proliferation

Reduce heat and dose at the con-tact of waste packages

Same as above plus decay stor-age for Cs137, Sr90

Minimize environmental impact Reduce radiotoxicity of waste, dose at the contact of the reposi-tory, reduce effluents

Same as above plus pay attention to waste streams at all fuel cycle steps, including fuel fabrication

Table 2.5: National energy policy objectives and associated technology requirements [8]

For instance, a country in phasing-out strategy can be interested in an advanced fuel cycle in order to deal with waste management, a country in stagnant nuclear energy share situation will chose advanced fuel cycles on the basis of cost-benefits analysis and countries with an ongoing energy policy will be attracted by advanced fuel cycles able to guarantee the long-term security of supply [8].

All these aspects together with the initial conditions in the country as well as the availability of the new technologies (reactors but also infrastructures as the reprocessing and fabrication plants for innovative fuel and plants, e.g. for waste vitrification) determine the choice adopted in the single country and then, it can modify the regional and global trends analyzed before. An example is the delay on implementing a strategy (e.g. transition to FRs) that can affect the availability of resources and the security of supply at world level.

The studies are presented according to three groups: 1) OECD countries with ongoing nuclear energy (e.g. France, Canada, Japan, Korean), 2) Other OECD countries (e.g. Germany) and, 3) non-OECD coun-tries (China and India).

2.5.1 OECD countries with ongoing nuclear energy programs

A short overview of the studies ongoing in France, Japan, USA is summarized in the following parts.

France

Advanced fuel cycles are studied in France since long time with the main objective to optimize the use of resources, to envisage the partitioning of MAs for the next reactor generation maintaining proliferation resistance and economical competitiveness [8].

France has the largest nuclear energy production in Europe. The 58 PWRs are producing every year ca. 430 TWhe corresponding to 78% of the total gross electricity generated [122]. The policy considered

by France, as also indicated in the Act of June 2006 [123], is to mainain the actual level of nuclear energy production reducing the MAs sent to disposal and deploying the future facilities [8].

Three steps for the French future scenario are investigated (see Figure 2.13): 1) replacement of the 50%

of operating fleet by the available technology (i.e. EPR developed by AREVA [124]) for the short-term (period 2020-2040); 2) replacement of the 50% of the remaining old fleet by FRs systems (or EPRs if the technology is not available) for the medium term (period 2040-2050); and 3) replacement of the first EPRs installed as Gen-IV systems for the long-term toward equilibrium situation (2080).

Figure 2.13: French future reactor substitution strategy [7]

The reference scenario considers the Pu mono-recycling in EPR (in agreement with the actual policy where 22 reactors are licensed for using MOX fuel [125]) and then the multi-recycling of second generation Pu (and the remaining first generation Pu) in FRs.

For a homogeneous recycling situation, the fuel contains 1.2% MAs (Am, Np, Cm) and ca. 20% Pu content (values that depend on the FRs considered as it is shown later on).MAs are then stabilized to ca. 86 tons in 2100 and natural uranium needs can be reduced by about 30-40% (in agreement, e.g. with the world study performed at KIT [4]).

These data can be affected by several scenario options (e.g. burn-up or out-of-pile time) but they repre-sent reasonably well the average values for the transition from a 100% LWRs fleet to a FRs fleet. The same order of magnitude has been found also for the reference case studied within this Ph.D. activity as described in Chapter 5.

Several alternatives have been analyzed. Some of them are oriented to investigate the final inventory if FRs are not deployed, e.g. considering only the mono-recycling of Pu in EPR or multi-recycling of Pu in EPR. All the studies have confirmed that, in order to properly transmute MAs, the adoption of FRs is essential. The expected favorable contribution is confirmed by the radiotoxicity behavior shown in Figure 2.14.

Several studies have been developed in the past at CEA (France), some examples (concerning also the investigation of Pu and MAs burning in LWRs under the assumption that FRs will not reach the expected safety level and, therefore, its industrial application) are reported in [125, 126, 127, 128, 129, 7, 9].

Figure 2.14: Radiotoxicity level of the TRUs disposed in the storage [8]

Additional studies have been performed considering the MAs separation and burning in ADS systems [128]. It has been concluded that the advantages of the use of an ADS in a double strata scenario compared to FRs with homogeneous MAs multi-recycling are not sufficient to justify this choice for a country with a continuous use of nuclear energy policy ongoing (as confirmed also by [130]). However, the adoption of an ADS in a regional strategy should be more feasible [5, 11].

The systems considered in the transition as well as the associated breeding capabilities can strongly impact the country-oriented scenario (and not only the world scenario as shown in Par. 2.3). According to [129], the comparison of three fast reactors has been performed in order to evaluate the ability of the systems for renewing the French fleet⁸.

All systems considered in [129] are able to renew the current fleet in the period 2035-2100. Assuming Pu and MAs multi-recycling, a stabilization of TRUs can be achieved too [129].

Further studies about MAs recycling in FRs have been carried out at CEA during the last two years (e.g. [7, 9]). The homogeneous and heterogeneous multi-recycling of MAs in sodium cooled fast reactors has been further analyzed [133]. These studies have shown how Am recycling plays the major role for the radiotoxicity reduction [9].

The addition of Am to depleted uranium blanket as well as to fuel core composition has been considered as an option also within the CP-ESFR project oriented to develop an innovative industrial scale sodium fast reactor able to fulfill the Gen. IV goals [58, 31, 30]. More details are included in Chapter 5 and Appendix D of the present study.

These scenarios show that the total Pu inventory can be stabilized (after the transition) in the case with only Pu multi-recycling. Concerning MAs, only the case with MAs multi-recycling attains a stabilization of the total amount⁹(see Figure 2.15). In fact, in the case of Am multi-recycling the Cm and Np produced

8In the study, the systems compared are the Na-cooled European Fast Reactor (EFR) developed in the nineties and characterized by a negative core BG (-0.2) and by a high power density (300 W/cm3) [103], the He-cooled Fast Reactor (Gas-cooled Fast reactor, GFR) characterized by positive BG and lower power density (100 W/cm3) [131] and a lead-cooled FR (BREST-OD-300) with an equilibrium BG of 0.08 and a power density of 150 W/cm3 [132].

9Scenario 1 considers only Pu multi-recycling in FRs and MAs are sent to disposal; Scenario 2 considers Pu multi-recycling in FRs core and MAs in radial blankets; and Scenario 3 considers Pu multi-recycling in FRs core and Am in radial blankets, Cm and Np are sent to disposal [9].

in the FRs increase slightly, thus modifying the total amount. Similar results have been obtained for the reference case studied within this Ph.D. activity (see Par. 5.2).

Recent studies [125, 134] concerning the industrial research for transmutation scenarios have been de-veloped taking into account an advanced Na-cooled fast reactor (similar configuration as the model studied within the CP-ESFR project [135, 58]). The Am and MAs transmutation advantages have been compared.

The heterogeneous recycling by the adoption of Americium Bearing Blanket sub-assemblies (AmBB) is preferable because the number of SAs to be treated is lower and therefore the requested fabrication plant capacities remain limited (limiting the cost too). However, a higher thermal power and a more difficult handling strategy are drawbacks well known for this solution [125].

Japan

Despite the last event (Fukushima) in Japan, nuclear energy will probably continue to play an important role for a country that imports ca 96% of its energy resources. The 53 nuclear power plant installed are able to cover ca. one-third of the electricity needs [8].

Since the eighties, in Japan, the development of advanced fuel cycles has promoted a better use of the resources and associated ambitious research programs have been launched (as the OMEGA program oriented to "Options Making Extra Gain from Actinides and Fission Products" to reduce the high-level radioactive wastes [8]). In particular, the recycling of MAs in ADSs and FRs has been considered.

The analysis of the possible fuel cycle options can be restricted to four main cases: 1) LWRs "once-through" case; 2) Partial reprocessing scenario where only one part of the SF is reprocessed, the remaining part is directly disposed; 3) Total reprocessing with Pu utilization in thermal reactors and Pu and MAs (Am, Np, Cm) recycled in FRs from 2050; and, 4) Interim storage scenario where FRs are deployed in 2050 after SF interim storage (no recycling in LWRs).

These cases have been compared (for more details see [8]), an example is reported in Figure 2.16 where cumulative natural uranium resources are analyzed for the several scenarios. This aspect is particularly important in country as Japan obliged to import all the material and therefore eager to guarantee the long-term security of supply.

The study performed in Japan is in agreement with the French case. It shows the more favorable behavior of a FRs-based scenarios in terms of environment burden and natural uranium demands. In order to limit the build-up of Am241 from Pu241 decay as well as the accumulation of Pu stock (improving the proliferation resistance), an integrated reprocessing technology, called Flexible Fuel Cycle Initiative (FFCI), is under development and study in Japan [136].

Korea and Canada

Several studies have been performed also in Korea (e.g. [137, 8]). Korea has a total installed capacity of 17.7 GWe supplying 39.0% of its electricity needs.

The Korean fleet is composed of 16 PWRs and 4 PHWRs installed late in the eighties [17]. Due to fairly short period of operation up to now in Korea the main objectives are presently not related to the replacement of the fleet as indicated for France (Par. 2.5.1).

The main requirements for the Korean scenarios are that: 1) the accumulated PWR spent fuel shall keep below 20ktonHM (value assessed according to the estimated capacity requirement for the repository at present), and 2) the accumulated uranium demand shall remain below 5.0% of the identified uranium resources in the world (share that corresponds to the actual share).

In order to fulfill these objectives seven different fuel cycles have been compared [137, 8].

A parametric study concerning the adoption of SFR with different conversion ratio has been recently published [137, 138].

Figure 2.15: Minor Actinides inventory in cycle and in waste for the three cases considered in [9]

Figure 2.16: Accumulative uranium demands for Japan [8]

The study has shown that a complete substitution of the thermal fleet by FRs with CR equal to 1 (i.e.

self-sustaining system), leads to 50% reduction of the natural uranium use, 44% reduction of UOX fuel fab-rication and 50% reduction of total out-of-pile TRUs amount. Comparable results have also been obtained by own investigations of similar substitution scenarios. Essential findings of that particular study, forming a constituent part of the present work, are outlined more precisely in Chapter 5 and in [139].

The Canadian case is an interesting scenario because it opens the attention to other kind of systems as the CANDU technology is originally based on natural uranium and heavy water. The transition from thermal-to-fast reactors has been analyzed for Canada too [8].

The adoption of Heavy Water reactors (HWRs) facilitate the transition toward fast reactors because of their good conversion capability enabling to provide the first fissile loading.

In addition the option of combining the Th-fuel cycle with CANDU reactors enables the generation of U233 while significantly extending uranium resources [8, 140].