DRIVERS AND IMPEDIMENTS TO PURSUE A PARTICULAR NUCLEAR ENERGY SCENARIO FAMILYSCENARIO FAMILY

Technical meetings and case studies⁹ of the SYNERGIES collaborative project made it possible to identify drivers and impediments for considering a particular scenario family¹⁰, as well as possible patterns of collaboration among countries in these scenarios. These ‘scenario specific’ drivers and impediments are briefly summarized below for each scenario family as introduced in Section 2.7. The drivers and impediments for collaboration among countries to amplify the benefits of each scenario family by bringing them to those technology users and newcomers who would not pursue technical innovations indigenously are then described in Section 4. Section 4

9 Case studies of the SYNERGIES project are presented in Section 3.

10 Relationship between scenario families and options for enhanced nuclear energy sustainability is explained in Table 2.2.

Note: ALWR — advanced light water reactor; F(B)R — fast (breeder) reactor; LWR — light water reactor; MOX — mixed oxide;

UOX — uranium oxide.

FIG. 2.12. Scenarios of transition to Th/²³³U fuel cycle and scenarios with alternative U/Pu/Th fuel cycles (Scenario family D).

also incorporates major findings of the fourth INPRO Dialogue Forum, on drivers and impediments for regional cooperation on the way to sustainable NESs, convened in Vienna in 2012.¹¹

2.8.1. Business as usual scenarios consisting of once through fuel cycle and mono-recycling of U/Pu in thermal spectrum reactors (Scenario family A), with reference to Section 2.7.2 and Figs 2.7–2.9 At present, most of the Member States having a nuclear energy programme operate with thermal reactors with uranium dioxide fuel in a once through fuel cycle. Such situation is reasonably stable (to the extent some call it sustainable in the short term), owing to the following factors:

— The perceived no immediate shortage of natural uranium;

— Economic competitiveness in the short term with reliance on the available competitive offers of front end fuel cycle services;

— Competitive globally available services for wet and dry interim storage construction;

— No need to develop additional domestic specialized skills related to back end fuel cycle services.

On the other hand, there are factors that make the current situation non-sustainable from a resource and waste perspective, including:

— Growing security of supply risks in the long term.

— Spent fuel accumulation that is directly proportional to energy produced by nuclear power plants:

● Saturation of the available wet spent fuel pool capacities for interim (cooled) storage.

● Limitations of the interim dry spent fuel storage facilities: long term/very long term behaviour of spent fuel in dry storage is unknown and may reduce options for further management of such fuel even in the medium term (i.e. beyond a certain interim storage period no options may remain to manage spent nuclear fuel); in this, the associated increased costs and risks cannot be assessed up front.

— Proliferation and security risks associated with long term/very long term interim storage and direct disposal of spent nuclear fuel.

The above mentioned factors could lead to certain kinds of synergistic collaboration among countries, which may include:

— Regional interim storage and geological disposal sites [2.9]¹²;

— Front end regional fuel cycle centres (e.g. URENCO).

Scenario family A also includes scenarios with mono-recycling of plutonium in LWRs. Already a reality in the European Union, although on a limited scale [2.28, 2.29], this step is driven by:

— The possibility to reduce natural uranium specific consumption by 15–25% for the case of uranium and plutonium recycling;

— An option to empty on-site and off-site wet interim spent fuel storage pools;

— An option to postpone the need for wet/dry interim (regional) spent fuel storage solutions, as well as the need for geological disposal;

— Alleviation of difficult to safeguard proliferation risks in geological disposal;

— Possibility to rely on the available, although limited, international/regional back end fuel cycle services.

The impediments for the above mentioned scenarios are as follows:

— Their realization requires at least a medium term vision on nuclear energy use, which is not yet developed in many Member States.

11 See www.iaea.org/INPRO/4th_Dialogue_Forum/index.html

12 They do not yet exist.

Note: ALWR — advanced light water reactor; F(B)R — fast (breeder) reactor; LWR — light water reactor; MOX — mixed oxide;

UOX — uranium oxide.

FIG. 2.12. Scenarios of transition to Th/²³³U fuel cycle and scenarios with alternative U/Pu/Th fuel cycles (Scenario family D).

— If the domestic recycling is considered, this would require careful planning to align the spent fuel reprocessing and the uranium and plutonium recycling requirements, which might be difficult to achieve in some countries.

— Notwithstanding the fact that international services are available, these scenarios will require certain fuel cycle management skills to be developed domestically.

— Yet another impediment could be the agreement a country may have with another country, under which certain restrictions on nuclear trade with the third parties are imposed.

2.8.2. Scenarios with the introduction of a number of fast reactors to support multi-recycling of Pu in LWRs and fast reactors (Scenario family B), with reference to Section 2.7.3 and Fig. 2.10

These scenarios may be driven by:

— Avoidance of any spent fuel direct disposal;

— Possibility to further reduce specific natural uranium consumption;

— Delayed interim storage needs for MOX spent fuel;

— Avoidance of fissile material disposal, possibly simplifying safeguards and physical protection requirements for such disposal sites.

However, the impediments here relate to:

— The increase of the specific fraction of minor actinides in ultimate waste;

— The need to develop a well defined back end fuel management strategy;

— The need to modify core management schemes for evolutionary LWRs;

— The need to demonstrate fast reactor technology and the associated fuel cycle.

The synergistic collaborations for the Scenario family B may include:

— Regional interim storage and geological disposal sites;

— Regional fuel cycle centres (e.g. La Hague);

— Pre-cycling and TOP-MOX (see Figs 2.8 and 2.9), as well as other international (regional) fuel cycle services.

The scenarios of the B family could substantively address the spent fuel buildup issue, but will provide only limited improvement in natural fissile resource saving. It could be noted that these scenarios can be viewed as a transition phase towards fast reactor centred scenarios of the C family, which offer much better natural uranium savings but would require a larger number of fast reactors.

2.8.3. Fast reactor centred scenarios enveloping scenarios with reprocessing of thermal reactor fuel to enable noticeable growth rate of fast reactor capacity (Scenario family C), with reference to Section 2.7.4 and Fig. 2.11

Scenarios with a higher fraction of fast reactors may be driven by rapidly growing NESs and/or when it is strategically decided by a country to pursue energy independence including both, fissile resource and sustainable waste management. The technologies for such scenarios are available and are (almost) industrially mature in several technology holder countries.

From the investment standpoint, fast reactor centred scenarios make sense only when the targeted deployment scale of fast reactors is several tens of gigawatts within the present century; otherwise, the payback period may well exceed the century time frame [2.6]. However, countries with smaller nuclear demand projections could share the benefits offered by such scenarios through synergistic collaboration with technology holders in fuel cycle back end (see Section 2.5). The drivers for embarking on such scenarios are:

(a) Possibility to achieve a ‘perfect synergy’ between LWRs/HWRs and fast reactors (i.e. recycle all mined uranium resources and tails within a single multicomponent NES).

(b) High degree of flexibility, given multiple parameters:

— Fast reactor/LWR+HWR ratio;

— Fast reactor conversion/breeding ratio;

— Reduced specific (per unit of energy produced) minor actinide inventory in waste.

(c) Reduction/elimination of proliferation risks related to final disposal of waste and, for some options, to enrichment.

At the same time, moving along such scenarios is restricted by the following impediments:

— Anticipated higher overnight construction costs for fast reactors;

— The need to achieve industrial maturity for fast reactors and the associated fuel cycles;

— Synergistic collaboration in scenarios of the C family might require both, commonly shared vision of an international (regional) NES and regional fast reactor fuel cycle service centres, which in turn would require time to be developed and deployed; ideally, an alignment on main fuel cycle technology choices would be an asset here.

Multiple variants can be considered within this scenario family, depending on the timing of introduction of fast reactors and the ratio of fast reactor/LWR deployment in a variety of national or regional nuclear power park settings. Fast reactor deployment could be considered domestically for large enough nuclear energy programmes [2.6]; however, due to technical–economic and sociopolitical reasons, preference may be eventually given to international consortia where fast reactors are part of the regional fuel cycle centres aimed at managing the plutonium balance for many countries, possibly complementing the system also with reprocessed uranium and plutonium recycling in LWRs and even HWRs.

2.8.4. Scenarios of transition to Th/²³³U fuel cycle and scenarios with alternative U/Pu/Th fuel cycles (Scenario family D), with reference to Section 2.7.5 and Fig. 2.12

With regard to Scenario family D, the case studies presented in Section 3 do not address synergistic collaborations among technology holders and technology users/newcomers for the plain reason that so far there is only one country — India — that has moved significantly along the thorium route to cater to the needs of its huge domestic market in a sovereign manner. Notwithstanding, the discussions at the SYNERGIES technical meetings make it possible to assume that the drivers for synergistic collaboration in scenarios of the D family could be:

— Full realization of nuclear energy sustainability potential, additionally boosted by the several times increase of the available natural fissile/fertile resources;

— Possibility to exploit in full the synergistic potential among thermal spectrum and fast spectrum reactors with respect to thorium and ²³³U.

The impediments for embarking upon scenarios of the D family are as follows:

— Addition of the ²³³U–thorium fuel cycle would result in a more complex fuel cycle management involving both the uranium and plutonium and the ²³³U and thorium cycle simultaneously.

— Also required would be a whole new nuclear fuel cycle infrastructure specific to ²³³U and thorium, including mining, new fuel and fuel fabrication technologies, new fuel handling and radioprotection technologies, new separation processes and waste characterizations. Overall, qualification of the whole technology towards industrialization would be required.

The synergistic collaborations possible for scenarios of the D family could be:

— Regional interim storage and geological disposal sites;

— International/regional nuclear power plant parks and fuel cycle services.

Some observers to the SYNERGIES project also considered examining the potential of thorium–rare earth synergy (thorium is a by-product of rare earth mining). It was noted that here the economics might either be a driver (competitive) or an impediment (non-competitive).