Alternative deployment strategy of fast reactor startup on enriched U fuel 1. Introduction

The present study was performed within Task 2, on the evaluation of additional options for NESs with thermal and fast reactors of the collaborative project SYNERGIES. The objective of this task is to investigate possible synergies among the already considered technology options and additional options which have not been addressed in previous INPRO studies. The GAINS analytical framework [3.52] was a basis for the performed studies.

This framework considers a global scenario level for NESs based on regional NES scenarios with collaborative agreements addressing fuel cycle options. Based on SYNERGIES objectives, this study considered various fast reactor deployment strategies for sustainable global nuclear energy in the 21st century. The complete case studies can be found in Annexes XVIII and XIX on the CD-ROM accompanying this publication. Some intermediate results of study were presented at the HLMC 2013 conference [3.83].

3.3.7.2. Objective and problem formulation

One of the problems with the current generation of nuclear fuel cycles based on thermal reactors is the limited supply of natural uranium that can be obtained economically. Natural uranium is used inefficiently within the existing once through nuclear fuel cycle and is not available equally to all countries. Moreover, large scale nuclear power reactors operating in a once through nuclear fuel cycle cannot be deployed at the same capacity as organic fuelled power plants.

Addressing the uranium fuelling problem requires modelling the long term scenarios for nuclear power development in order to predict the consequences of various approaches. In this context, proposals to develop nuclear power on a large scale focus on the use of fast reactors instead of thermal reactors. This study describes and tries to explain that it is more efficient and effective to use enriched uranium in a fast reactor (breeding ratio > 1) and recycle its spent fuel to extract plutonium for further use than to use enriched uranium in LWRs (breeding ratio < 1) without further recycling.

This study provides more detailed analysis of the likely impacts of introducing fast reactors with enriched uranium fuel. The findings are then applied to the GAINS project analysis of a synergistic heterogeneous world model [3.52], taking into account material flow analysis and economics: material flow analysis considers natural uranium consumption, SWU, plutonium balance in the storage, and spent fuel; economics considers fuel cost analysis and levelized fuel cycle unit cost associated with different reactor types.

3.3.7.3. Assumptions, methods, codes and input data used

Two growth curves were established for GAINS, as follows: a high case that climbs to 5000 GW(e)·year and a moderate case that climbs to 2500 GW(e)·year being flattened after 2100. Each curve has three growth periods and follows a linear growth to meet the specific level of power generation by the end of the respective period:

(i) 2009–2030: 600 GW(e)·year and 700 GW(e)·year growth levels for the moderate and high case, respectively.

(ii) 2031–2050: 1000 GW(e)·year and 1500 GW(e)·year growth levels for the moderate and high case, respectively.

(iii) 2051–2100: 2500 GW(e)·year and 5000 GW(e)·year for the moderate and high case, respectively.

Four reactor types have been considered: LWR, HWR and two fast reactors, FR12_MOX and FRU.

FR12_MOX reactor is an SFR (breeding ratio of 1.2) using MOX fuel. FRU uses enriched uranium fuel for first startup with subsequent recycling of plutonium+uranium+minor actinides from the spent fuel. FRU could be, for example, a lead cooled fast reactor design with a breeding ratio of 1.05. Calculations were carried out using MESSAGE [3.36], CYCLE [3.84] and the IAEA NEST tool for economic aspects (i.e. LUEC). Following the GAINS approach, several assumptions also were implied on reactor and fuel cycle features:

— Unlimited uranium resources are assumed.

— The uranium enrichment tails assay is equal to 0.3% for models in Annex XVIII and 0.2% for models in Annex XIX.

— Temporary storage is used for HWR spent fuel.

— Cooling pool retention time is three years for irradiated fast reactor fuel assemblies, five years for irradiated LWR fuel assemblies.

— The loss factor of the fuel fabrication and reprocessing is equal to zero.

A fast reactor with a first loading (FRU) of enriched uranium was introduced in the basic fuel cycle system of GAINS framework (see Fig. 3.168).

3.3.7.4. Summary presentation and analysis of the results

(a) Alternative fast reactor deployment scenarios of transition to sustainable NESs (²³⁵U load versus uranium–

plutonium load)

For fast reactors, an alternative use of enriched uranium fuel for first startup with subsequent recycling (of plutonium+uranium+minor actinides) from the spent fuel is an interesting option. This option was addressed briefly in Ref. [3.25]. This study provided more detailed considerations for the impact of introducing fast reactors with enriched uranium fuel startup.

Figures 3.169–3.172 present comparison of key characteristics of considered reactor types for detailed understanding of scenario simulation. Total natural uranium consumption for first load and total annual reload over the life of reactor is compared in Fig. 3.169. LWRs have the highest natural uranium consumption total during

FIG. 3.168. Fuel cycle system, BAU with fast reactor scenario.

FIG. 3.169. Total uranium consumption. FIG. 3.170. Total separative work unit requirements.

FIG.3.171. Mass of plutonium per year. FIG. 3.172. Mass of minor actinides per year.

FIG. 3.173. Fast reactor power production growth. FIG. 3.174. Reprocessing rates for UOX fuel.

lifetime and FRU has the lowest uranium consumption in the form of enriched uranium. Therefore, replacing LWRs by fast reactors can lead to potential saving of natural uranium resources. Similar trends are shown by the Fig. 3.170 in terms of total SWU requirements. Figure 3.171 shows the comparison of the plutonium ‘inventory’, which is a difference between production and consumption of plutonium for the typical reactor type. Figure 3.172 shows a comparison of minor actinide production over the life of the reactors.

There are constraints imposed by the GAINS framework on total power production rate of fast reactors by 2030 and 2050, with objectives in high growth case to have total fast reactor generation rate of 10 GW(e)·year in 2030 and a total of 400 GW(e)·year in 2050. The GAINS framework also puts constraint on total plutonium inventory in the spent fuel storage to be maintained close to zero. Fast reactors introduction rate after 2050 is not constrained by the capacity, but rather limited by plutonium availability and overall growth rate of the NES.

The analysis shows that available industrial reprocessing capacity significantly lacks the plutonium production to satisfy the fast reactor introduction rate. Limited reprocessing capacity will reduce the introduction rate of fast reactors, which needs to be considered in efficient planning of long term global transition scenario towards fast reactors.

The study further investigates the impact of limiting LWR reprocessing capacity on possible deployment of fast reactors. Figures 3.173 and 3.174 show the curves for power production growth demand of fast reactors as identified by GAINS (linearly growing to 400 GW(e)·year by 2050) and related demand reprocessing load. With unlimited separation capacity, it results in significant reprocessing requirements for a very short period of about 1–3 years in 2030 and 2050 for the first fast reactor fuelling.

Fast reactors require an operational time of three years prior to start using plutonium reprocessed from their own spent fuel. Many reprocessing facilities cannot be built in a limited duration of few years due to economic constraints. Figures 3.173 and 3.174 also show that a power production growth rate of 400 GW(e)·year for fast reactors can be achieved if the introduction of new reprocessing capacities is limited to 850 t HM/year of LWR spent fuel until 2050 and up to 3000 t HM/year of LWR spent fuel afterwards. Whereas, limiting new LWR reprocessing capacity introduction to 850 t HM/year results in only 300 GW(e)·year power production capacity realization. Hence, the limitations in reprocessing capacity pose a considerable limit on the fast reactor deployment.

If the reprocessing capacity introduction limit is elevated to 3000 t/year of spent fuel after 2035, LWR spent fuel reprocessing can be increased and 400 GW(e)·year fast reactor power growth can be achieved by 2050. However, the demand will not be met by linear growth of fast reactors in this case. This issue can be overcome by using enriched uranium as first fuel loading in fast reactors.

This study employs the GAINS framework for assessing impact of different reactor types on infrastructure requirements of nuclear fuel cycle over time. The study considered SFRs and LFRs, first loaded with enriched uranium and subsequently shifting to their own plutonium based reprocessed fuel. The study aims at identifying the prospects and limitations of deployment strategies of different fast reactors and their combinations. The sensitivity of fast reactor shares towards different key indicators of the NES is evaluated. Following possible options with mentioned fast reactor shares are evaluated in the current study:

FIG. 3.168. Fuel cycle system, BAU with fast reactor scenario.

FIG. 3.169. Total uranium consumption. FIG. 3.170. Total separative work unit requirements.

FIG.3.171. Mass of plutonium per year. FIG. 3.172. Mass of minor actinides per year.

FIG. 3.173. Fast reactor power production growth. FIG. 3.174. Reprocessing rates for UOX fuel.

— BAU: Once through nuclear fuel cycle using conventional LWRs and HWRs.

— FR12_00%/FRU_100%: FR12 at 0% and FRU at 100% share of total fast reactor demand.

— FR12_25%/FRU_75%: FR12 at 25% and FRU at 75% share of total fast reactor demand.

— FR12_50%/FRU_50%: Both FR12 and FRU at 50% share of total fast reactor demand.

— FR12_75%/FRU_25%: FR12 at 75% and FRU at 25% share of total fast reactor demand.

— FR12_100%/FRU_00%: FR12 at 100% and FRU at 0% share of total fast reactor demand.

Figure 3.175 shows the fast reactor power production growth for different shares of fast reactor types varying from 0% to 100%. Figure 3.176 shows overall global power production growth for a case of both FRU and FR12 shares at 50% of fast reactor nuclear power demand. Total fast reactor demand is set initially at 400 GW(e)·year by 2050 and at maximum possible fast reactor introduction rate afterwards.

Different fast reactor share options are analysed and compared with the BAU option for the key indicators of NES such as cumulative natural uranium utilization, SWU requirements, LWR spent fuel reprocessing requirements, spent fuel accumulation in dry storage facilities, reprocessed fission products and minor actinide stocks, plutonium and minor actinide accumulation in long term spent fuel storage facilities. Figures 3.177 and 3.178 show cumulative natural uranium consumption for the considered options and comparative performance of these options to the BAU scenario, respectively.

All options of fast reactor shares show similar saving of natural uranium in the long term perspective, with option of FR12_50%/FRU_50% performing slightly better. However, completely different trends are observed in short and medium terms. The highest natural uranium consumption is observed with the FR12_00%/FRU_100%

option until 2060 and this trend is even higher than the BAU option rising 5% above it from 2035 and 2040.

The lowest natural uranium consumption is observed with the FR12_100%/FRU_00% option until 2070. The FR12_50%/FRU_50% option shows intermediate natural uranium consumption in the medium term lying close to the FR12_100%/FRU_00% option, which is justified since there are significant requirements of natural uranium for first enriched uranium core loading of FRU reactors (see Fig. 3.169).

Annual SWU requirements calculated for different fast reactor share options are shown in Fig. 3.179. The SWU requirements for the BAU case are comparable with other fast reactor share options in the short (until 2030) and medium (until 2050) terms, but considerably higher than all fast reactor options in the long term rising to 800 kt SWU/year by 2100. Two relatively short lived steep SWU growth trends are observed for the FRU options around 2030 and 2050 resulting from the increase in capacity growth rate of FRUs. The most noticeable rise in SWU requirements from 220 kt SWU/year to 350 kt SWU/year is observed for the FR12_00%/FRU_100% option in 2050, but straightens afterwards to the end of the century. Most feasible results are obtained from the option of FR12_50%/FRU_50% which shows nominal growth in 2050 and minimal level of SWU requirements for the medium and long terms, thus being the optimum choice among all fast reactor share options.

FIG. 3.175. Fast reactor power production growth. FIG. 3.176. Power production growth (FRU: 50% of fast reactor

power production growth). FIG. 3.177. Cumulative natural uranium consumption. FIG. 3.178. Comparative cumulative natural uranium

consumption.

FIG. 3.179. Separative work unit requirements.

(b) Economic aspect of fast reactor deployment scenarios (²³⁵U load versus uranium–plutonium load)

In this study, the focus is on the fuel cost while recognizing that the capital and operation and maintenance costs are significant components of the total LUEC. Fuel cycle cost analysis is based on a cost breakdown structure for a specific nuclear fuel cycle scheme, which includes fuel cycle components from uranium mining to HLW disposal.

Capital cost is influenced by a deep division of labor, a long production chain (from raw materials to final product) and R&D, so investment risk is significant. Fuel cost makes a much smaller contribution to the LUEC than the capital cost, which is a strong advantage for nuclear power over the fossil energy sources. Figure 3.180 shows the levelized fuel cycle unit cost associated with different reactors:

— LWR: a typical PWR design considered in the GAINS project.

— FR: a ‘break-even’ fast reactor considered in the GAINS project.

— FR12: a SFR with a breeding ratio of 1.2.

— HLMR: a heavy liquid metal cooled fast reactor with a breeding ratio of 1.05.

FIG. 3.175. Fast reactor power production growth. FIG. 3.176. Power production growth (FRU: 50% of fast reactor

power production growth). FIG. 3.177. Cumulative natural uranium consumption. FIG. 3.178. Comparative cumulative natural uranium

consumption.

FIG. 3.179. Separative work unit requirements.

The fuel cycle component encompasses uranium cost, reprocessing, fuel reload, first fuel load, spent fuel disposal and HLW disposal. Levelized fuel cycle cost of HLMRs using enriched uranium (natural uranium = US $80/kg U) for first loading is in the range between HLMRs using LWR plutonium for first loading and plutonium from fast reactors. It is comparable to levelized fuel cycle cost of LWRs operating in a once through fuel cycle. The levelized cost of HLMR with uranium startup is cheaper than that of the FR12.

The technology is economically viable under existing uranium cost. If the uranium cost increases up to US $260/kg, the uranium levelized fuel cycle cost of HLMRs using enriched uranium becomes lower than the levelized fuel cycle cost of LWRs operating in a once through fuel cycle. On the other hand, it approaches the fuel cycle cost of HLMRs using LWR plutonium. The latter option becomes more economic as the uranium cost

(a) Uranium = US $80/kg U.

(b) Uranium = US $260/kg U.

FIG. 3.180. Levelized fuel cycle cost. TABLE 3.38. CAPACITY OF NG1 AND 50% NG3 BY

YEARS (GW(e))

Year NG1 50% NG3 Total

2008 149 0 149

2030 358 17 375

2050 853 68 921

2100 3250 500 3750

increases. For a uranium cost of US $260/kg, the uranium levelized cost of HLMRs with uranium startup is still cheaper than the one of FR12 using LWRs plutonium for first loading and the first three years of refuelling, but becomes more expensive than FR12 using LWRs plutonium for the first loading.

These results indicate that fuel cost in the case of startup on enriched uranium will begin to rise. It may be economical to start from uranium first loading of HLMRs and then replace with first loading based on LWR/fast reactor plutonium.

(c) Alternative deployment strategy of fast reactor startup on enriched uranium fuel

This section considered the deployment strategy of the Russian designed BN-1200 SFR with startup on enriched uranium oxide fuel. In the current study, in the modelling scenarios of transition to sustainable NES with fast reactors on enriched uranium, a high case scenario was adopted of up to 5000 GW·h by 2100. There was a GAINS scenario modification with an enlarged rate of fast reactor commissioning from 2030 to 2050. The considered global scenario refers to an option where the capacities in NG1 are expected to have high growth (from 50% to 65%). The mathematical model consists of NG1 and half of the NG3 capacities (half of NG3 spent fuel).

This means that the scenario works with thermal and fast reactors of NG1, as well as with the thermal reactors of NG3 (see Table 3.38). Spent fuel from NG3 is transported to common spent fuel storage of NG3 and is reprocessed immediately.

There are two scenarios of nuclear energy development by 2100 with different structure of reactor types:

LWR with uranium fuel, FR-1200 with uranium fuel and FR-1200 with MOX fuel. The first scenario is based on joint operation of thermal reactors (ALWR-1000 — an advanced LWR) with UOX fuel and fast reactors (FR-1200 with MOX fuel). In the second scenario, commissioning of thermal units stops in 2030. Introduced reactors work until the end of lifetime. FR-1200 MOX and FR-1200 UOX units provide for replacement of missing capacities.

The electricity production of ALWR-1000 reactors (lifetime of 60 years) reaches 960 GW(e) by 2100 in Scenario 1. To provide the desired total demand (see Table 3.38), characteristics of the Russian designed BN-1200 SFR with MOX fuel in equilibrium conditions were used as an example of a typical fast reactor. The BN-1200 reactor (lifetime of 60 years) will be commissioned from 2021, with a summary electricity production running up to 2790 GW(e) by 2100.

Scenario 1 is not optimal due to the following inherent fundamental flaws:

— Long period of thermal reactors mass use entails accelerated depletion of cheap natural uranium.

— Full reprocessing of spent fuel with limited requirements of total fast reactors capacities leads to excessive plutonium stocks buildup. The refusal of irradiated nuclear spent fuel reprocessing would lead to the large amount of radioactive materials accumulation and will require construction of an ever increasing amount of spent nuclear fuel storage facilities.

Scenario 2 assumes that from 2030 all new installed capacity will be with fast reactors. In the case of insufficient amount of plutonium to launch the BN-1200 on MOX, uranium fuel can be used. In the case of BN-1200 on MOX, there would be savings of natural uranium, reducing plutonium stockpiles and the need for new (a) Uranium = US $80/kg U.

(b) Uranium = US $260/kg U.

FIG. 3.180. Levelized fuel cycle cost. TABLE 3.38. CAPACITY OF NG1 AND 50% NG3 BY

YEARS (GW(e))

Year NG1 50% NG3 Total

2008 149 0 149

2030 358 17 375

2050 853 68 921

2100 3250 500 3750

spent fuel storage facilities. There is a 10% operational plutonium supply in these scenarios; under such conditions, the accumulation of direct use material becomes problematic.

A chart of thermal and fast reactor capacities, depending on the time for Scenarios 1 and 2, is shown in Fig. 3.181. Figure 3.182 shows the annual natural uranium consumption in both considered scenarios. By 2100 in Scenario 1, the total natural uranium consumption is 11.189 million t, while the depleted uranium consumption is 1.09 million t. The annual demand for natural uranium is 46 500 t in 2020, 107 000 t in 2050 and 142 000 t in 2100 (the maximum is 177 000 t in 2076).

By 2100 in Scenario 2, the total natural uranium consumption is 9.91 million t, while the depleted uranium consumption is 1.59 million t. The annual demand for natural uranium is 46 500 t in 2020, 216 000 t in 2050 and 75 700 t in 2100 (the maximum is 226 000 t in 2051). Scenario 2 gives 11.4% savings of natural uranium, but leads to a 45.9% increase in the flow of depleted uranium. Figure 3.182 shows spurts in the annual natural uranium consumption for Scenario 2. The maximum consumption is 226 000 t/year in 2076 against 177 000 t/year in 2051 for Scenario 1, which is due to the FR-1200 (UOX) commissioning.

In both considered scenarios, there is a significant and growing mass of plutonium in storage at the end of the modelling period. By 2100 in Scenario 1, 929 t of plutonium would be accumulated, while in Scenario 2, 3846 t of plutonium would be accumulated.

(a) Scenario 1 (b) Scenario 2

FIG. 3.181. Total capacity of thermal and fast reactors.

(a) Scenario 1 (b) Scenario 2

FIG. 3.182. Annual natural uranium consumption.

FIG. 3.183. Separative work unit demand, MESSAGE and

CYCLE results comparison. FIG. 3.184. Plutonium amount in storage, MESSAGE and

CYCLE results comparison.

CYCLE results comparison.

Dans le document Enhancing Benefits of Nuclear Energy Technology Innovation through Cooperation among Countries: Final Report of the INPRO Collaborative Project SYNERGIES | IAEA (Page 182-198)