Fuel Cycle Costs Research Articles

Recycling scheme and fuel cycle costs for twin BWRs reactors

To access possible economic advantages of reprocessing and recycling the spent fuel from nuclear power reactors against a once through policy, a proposed scenario for twin BWRs was established. Calculations for the amount of fuel that the plants will use and generate during 40 years of operation under each scenario were made. An evaluation of costs for each option applying current prices for uranium and services were then carried out. Finally a comparison between the options was made, and it was found that the recycling option is more expensive than the once through cycle by about 4%.

SHIELDED LASER ABLATION ICP-MS SYSTEM FOR THE CHARACTERIZATION OF HIGH BURNUP FUEL

In modem power reactors, nuclear fuels have recently reached 55,000 MWd/MtU from the initial average burnup of 35,000 MWd/MtU to reduce the fuel cycle cost and waste volume. At such high burnups, a fuel pellet produces fission products proportional to the burnup and creates a typical high burnup structure around the periphery region of the pellet, producing the so called 'rim effect'. This rim region of a highly burnt fuel is known to be ca. in width and is known to affect the fuel integrity. To characterize the local burnup in the rim region, solid sampling in the micro meter region by laser ablation is needed so that the distribution of isotopes can be determined by ICP-MS. For this procedure, special radiation shielding is required for personnel safety. In this study, we installed a radiation shielded laser ablation ICP-MS system, and a performance test of the developed system was conducted to evaluate the safe operation of instruments.

Technical feasibility of using RU-43 fuel in the CANDU-6 reactors of the Cernavoda NPP

Abstract Recovered uranium (RU) is a by-product of many light-water reactor (LWR) fuel recycling programs. A fissile content in the RU of 0.9 to 1.0 % makes it impossible for reuse in an LWR without re-enrichment, but CANDU reactors have a sufficiently high neutron economy to use RU as fuel. The Institute for Nuclear Research (INR) Pitesti has analyzed the feasibility of using RU fuel with 0.9 – 1.1 w% 235U in the CANDU-6 reactors of the Cernavoda Nuclear Power Plant (Cernavoda NPP). Using RU fuel would produce a significant increase in the fuel discharge burnup, from 170 MWh/kgU currently achieves with natural-uranium (NU) fuel to about 355 MWh/kgU. This would lead to reduced fuel-cycle cost and a large reduction in spent-fuel volume per full-power-year of operation. The RU fuel bundle design with recovered uranium fuel, known as RU-43, is being developed by the INR Pitesti and is now at the stage of final design verification. Early work has been concentrated on RU-43 fuel bundle design optimization, safety and reactor physics assessment. The changes in fuel element and fuel bundle design contribute to the many advantages offered by the RU-43 bundle. Verification of the design of the RU-43 fuel bundle is performed in a way that shows that design criteria are met, and is mostly covered by proof tests such as flow and irradiation tests. The most relevant calculations performed on this fuel bundle design version are presented. Also, the stages of an experimental program aiming to verify the operating performance are briefly described in this paper.

HIGH BURNUP FUEL ISSUES

One of the major current challenges to nuclear energy lies in its competitiveness. To stay competitive the industry needs to reduce maintenance and fuel cycle costs, while enhancing safety features. Extended burnup is one of the methods applied to meet these objectives However, there are a number of potential fuel failure causes related to increased burnup, as follows: l) Corrosion of zirconium alloy cladding and the water chemistry parameters that enhance corrosion; 2) Dimensional changes of zirconium alloy components, 3) Stresses that challenge zirconium alloy ductility and the effect of hydrogen (H) pickup and redistribution as it affects ductility, 4) Fuel rod internal pressure, 5) Pellet-cladding interactions (PCI) and 6) pellet-cladding mechanical interactions (PCMI). This paper discusses current and potential failure mechanisms of these failure mechanisms.

Feasibility study of boiling water reactor core based on thorium–uranium fuel concept

The design of a boiling water reactor (BWR) equilibrium core using the thorium–uranium (blanket–seed) concept in the same integrated fuel assembly is presented in this paper. The lattice design uses the thorium conversion capability to 233U in a BWR spectrum. A core design was developed to achieve an equilibrium cycle of one effective full power year in a standard BWR with a reload of 104 fuel assemblies designed with an average 235U enrichment of 7.5 w/o in the seed sub-lattice. The main core operating parameters were obtained. It was observed that the analyzed parameters behave like those obtained in a standard BWR. The economic analysis shows that the fuel cycle cost of the proposed core design can be competitive with a standard uranium core design. Finally, a comparison of the toxicity of the spent fuel showed that the toxicity is lower in the thorium cycle than in other fuel cycles (UO 2 and MOX uranium and plutonium) in the case of the once through cycle for light water reactors (LWR).

Assessment of Regenerative Reheating in Direct Brayton Power Cycles for High-Temperature Gas-Cooled Reactors

Future world energy demand will require a sustainable energy generation system. Optimization of power cycles has become a key element to better exploit natural resources, to minimize waste production, and even to reduce fuel cycle cost. Aware of this, nuclear technology is developing what has been termed Generation IV designs. In particular, the high-temperature gas-cooled reactor (HTGR) concept is a promising technology to reach much higher thermal efficiencies than present nuclear power plants.By using a classical thermodynamic methodology, this paper demonstrates that regenerative reheating would significantly enhance the thermal performance of a reference Brayton cycle based on pebble bed modular reactor (PBMR) technology. The regenerative reheating is conducted by a live gas fraction (β) extracted from the coolant inventory exiting the nuclear reactor. Optimization of β results in efficiency values as high as 53 and 61%, respectively, under current and midterm technology scenarios. In addition, reheating would allow an effective and easy-to-conduct “load-follow” operation with no loss of thermal efficiency in the upper range of β. Even further, under the midterm technology scenario, reheating would make it possible to cogenerate H2 from the enthalpy content of the β fraction exiting reheater.

Advanced Doped UO2 Pellets in LWR Applications

The nuclear industry strives to reduce the fuel cycle cost, enhance flexibility and improve the reliability of operation. This can be done by both increasing the fuel weight and optimizing rod internal properties that affect operational margins. Further, there is focus on reducing the consequences of fuel failures. To meet these demands Westinghouse has developed ADOPT (Advanced Doped Pellet Technology) UO2 fuel containing additions of chromium and aluminium oxides. This paper presents results from the extensive investigation program which covered examinations of doped and reference standard pellets both in the manufactured and irradiated states. The additives facilitate pellet densification during sintering and enlarge the pellet grain size. The final manufactured doped pellets reach about 0.5% higher density within a shorter sintering time and a five fold larger grain size compared with standard UO2 fuel pellets. The physical properties of the pellets, including heat capacity, thermal expansion coefficient, melting temperature, thermal diffusivity, have been investigated and differences between the doped and standard UO2 pellets are small. The in-reactor performance of the ADOPT pellets has been investigated in pool-side and hotcell Post Irradiation Examinations (PIEs), as well as in the Studsvik R2 test reactor. The investigations have identified three areas of improved operational behaviour: Reduced fission gas release, improved PCI performance thanks to increased pellet plasticity and higher resistance against post-failure degradation. Fuel segments have been exposed to ramp tests and enhanced power steady-state operation in the Studsvik R2 reactor after base-irradiation to above 30 MWd/kgU in a commercial BWR. ADOPT reveals up to 50% lower fission gas release than standard UO2 pellets. The fuel degradation behaviour has been studied in two oxidizing tests, a thermal-microbalance test and an erosion test under irradiation. The tests show that ADOPT pellets have a reduced rate of fuel washout, as compared to standard UO2 pellets. Fuel rods with ADOPT pellets have been irradiated in several light water reactors (LWRs) since 1999, including two full SVEA-96 Optima2 reloads in 2005.

Technology for Nuclear Reprocessing: Present and Future Directions

A variety of factors have served to bring nuclear technology to international attention as a viable option to meet a major fraction of the energy needs of the future. This has also brought the US policy since 1977 of a once‐through nuclear cycle into question. Such a process uses only about 5% of the energy content of the nuclear fuel. Although recycling the unburnt nuclear fuel seems reasonable from a technology point of view, proliferation risks led to cessation of the technology, as conventional reprocessing can be used to make weapons grade plutonium. The economic viability of recycling is also questionable, since uranium ore prices make the once‐through nuclear fuel cycle cost effective. In addition to the standard reprocessing cycle used in many countries, there are efforts to introduce advanced fuel cycle technologies that deal with some of the issues associated with the older technology. This presentation discusses the concerns with present reprocessing technologies and with the planned repository systems. Advanced separation systems designed to reduce the possibility of diversion of reprocessed material to weapons production are also discussed in the presentation. Other goals of these advanced systems are increased reactor operational safety, the reliable disposal of nuclear wastes from reprocessing for the millennia required to allow radioactive decay.

Development of enriched Gd-155 and Gd-157 burnable poison designs for a PWR core

In this study, a genetic algorithm developed by the authors was applied to design the optimal enriched Gd-155 and Gd-157 burnable poisons in a reference PWR TMI-1 core. The CASMO-4/TABLES/SIMULATE-3 package calculated the neutronic performance of the enriched UO 2/Gd 2O 3 fuel pin configurations. These configurations included different fractions of neutron absorbing isotopes Gd-155 and Gd-157, and 100 w/o enriched Gd-155 designs. Fuel cost analysis was performed to evaluate the economical benefits of these optimized enriched gadolinium designs. The break-even point for unit Gd-155 enrichment cost was determined to be around ∼$30/gram-Gd-155 with current unit cost scenario. The projected savings were 3.13% in gross and 2.08% in net compared to total fuel cycle cost of a reference TMI-1 core loading, if all of the 68 feed assemblies would be replaced with the optimized designs.

A Physics Study of a 600-MW(thermal) Gas-Cooled Fast Reactor

A neutronic feasibility study was performed for a 600-MW(thermal) gas-cooled fast reactor fuel cycle through recycling simulations. Sensitivity calculations were also performed for various physics design parameters such as the plutonium volume fraction of the fuel, fuel burnup, core material volume fraction, and the power density. The results showed that the initial breeding gain of –0.04755 is sufficient to sustain the recycling of the actinides with a reasonable amount of natural uranium and plutonium feed material. The comparative calculation on the core power density has shown that it is feasible to reduce the amount of minor actinides and spent fuel in the high power density core (98.4 MW/m3) compared to the reference core (58.2 MW/m3). It was also found that the fuel cycle cost is saved by 0.4 mills/kW·h for the high power density core compared to the reference core.

Compound Process Fuel Cycle Concept and Core Characteristics

A new fuel cycle concept is proposed in which spent fuels of light water reactor are multi-recycled in a fast reactor core without ordinary reprocessing process but with only simple dry pyrochemical processing. Feasibility of the concept has been studied focusing on the core nuclear characteristics adopting radial heterogeneous core configuration in which both recycled light water spent fuels and fast reactor fuels are loaded. Results of the core survey analyses show that four to six time recycling of light water reactor spent fuels with the burn-up of 300 to 400 GWd/t can be achieved with almost no increase of minor actinide content. Such benefits will be expected in this concept, though further research and development efforts are required, as efficient utilization of nuclear fuel resources, enhancement of nuclear non-proliferation due to the fact that all actinides are recycled all together in a lumped state together with the fact that the concept has no radial blanket fuels which contain high fissile plutonium ratio, besides the possibilities of reduction of environmental impacts due to reduced high level waste, reduction of fuel cycle cost through simplified reprocessing procedure, and suppression of light water reactor spent fuel pile-up.

Advanced Doped UO2 Pellets in LWR Applications

The nuclear industry strives to reduce the fuel cycle cost, enhance flexibility and improve the reliability of operation. This can be done by both increasing the fuel weight and optimizing rod internal properties that affect operational margins. Further, there is focus on reducing the consequences of fuel failures. To meet these demands Westinghouse has developed ADOPT (Advanced Doped Pellet Technology) UO2 fuel containing additions of chromium and aluminium oxides. This paper presents results from the extensive investigation program which covered examinations of doped and reference standard pellets both in the manufactured and irradiated states. The additives facilitate pellet densification during sintering and enlarge the pellet grain size. The final manufactured doped pellets reach about 0.5% higher density within a shorter sintering time and a five fold larger grain size compared with standard UO2 fuel pellets. The physical properties of the pellets, including heat capacity, thermal expansion coefficient, melting temperature, thermal diffusivity, have been investigated and differences between the doped and standard UO2 pellets are small. The in-reactor performance of the ADOPT pellets has been investigated in pool-side and hotcell Post Irradiation Examinations (PIEs), as well as in the Studsvik R2 test reactor. The investigations have identified three areas of improved operational behaviour: Reduced fission gas release, improved PCI performance thanks to increased pellet plasticity and higher resistance against post-failure degradation. Fuel segments have been exposed to ramp tests and enhanced power steady-state operation in the Studsvik R2 reactor after base-irradiation to above 30 MWd/kgU in a commercial BWR. ADOPT reveals up to 50% lower fission gas release than standard UO2 pellets. The fuel degradation behaviour has been studied in two oxidizing tests, a thermal-microbalance test and an erosion test under irradiation. The tests show that ADOPT pellets have a reduced rate of fuel washout, as compared to standard UO2 pellets. Fuel rods with ADOPT pellets have been irradiated in several light water reactors (LWRs) since 1999, including two full SVEA-96 Optima2 reloads in 2005.

Impact of High Burnup on PWR Spent Fuel Characteristics

Reducing the burden of management of spent nuclear fuel is important to the future of nuclear energy. The impact of higher pressurized water reactor (PWR) fuel burnup is examined in this paper from the perspective of its impact on spent-fuel radioactivity, decay heat, and plutonium content. The necessary fresh fuel enrichments to achieve high burnup in PWRs with the same three-batch operation scheme are first computed; then, characteristics of the spent fuel are determined. The increase in decay heat with burnup is found to be generally less than linear. Although each high-burnup fuel assembly would be hotter and more radioactive, the total decay heat to be removed or accommodated in storage is less for the same electricity production. If the time window before 150 yr after discharge can be excluded from impacting a repository, significant savings in its capacity can be realized with high-burnup fuel. The high-burnup fuel is more proliferation resistant because of reduced total plutonium production per kilowatt hour and because of higher content of less desirable plutonium isotopes, such as 238Pu. The fuel cycle cost can be slightly reduced by increasing burnup until it reaches a shallow minimum near 70 MWd/kg. Higher burnups would require one-time changes to the limits on enrichments that can be handled in most commercial fuel fabrication facilities. Changing the waste fee to base it on the amount of radioactivity in the spent fuel would enhance the economic benefit of high burnup.

05/02064 Purex co-processing of spent LWR fuels: comparative fuel cycle cost analyses

05/02064 Purex co-processing of spent LWR fuels: comparative fuel cycle cost analyses

Effect of Highly Enriched/Highly Burnt UO2 Fuels on Fuel Cycle Costs, Radiotoxicity, and Nuclear Design Parameters

A study of high-burnup pressurized water reactor (PWR) fuel management schemes extending to 100 GWd/tonne is presented. The Studsvik Scandpower code suite was used to model a Westinghouse three-loop PWR core, and realistic loading patterns were derived. The loading patterns were optimized for minimum power peaking and maximum cycle length using engineering judgment and automated binary shuffles. Gadolinia was found to control power peaking to within current FΔH design limits up to 70 GWd/tonne, with only a slight deterioration thereafter. The moderator temperature coefficient, boron coefficient, and control rod worth were calculated and shown to fall within existing design limits.An economic analysis was carried out to determine the most economic discharge burnup based on fuel cycle costs only. It was found that the lowest fuel cycle costs were obtained with average discharge burnups between 70 to 75 GWd/tonne (initial enrichments between 6 to 7 wt%).The energy generated per tonne of uranium ore used was calculated and shown to peak between 40 to 60 GWd/tonne. Also, the radiotoxicity generated per GW·yr(electric) was calculated for each fuel management scheme and found to reduce considerably with burnup between 100 and 100 000 yr.

Optimum Discharge Burnup and Cycle Length for PWRs

This paper discusses the results of a pressurized water reactor fuel management study determining the optimum discharge burnup and cycle length. A comprehensive study was performed considering 12-, 18-, and 24-month fuel cycles over a wide range of discharge burnups. A neutronic study was performed followed by an economic evaluation. The first phase of the study limited the fuel enrichments used in the study to <5 wt% 235U consistent with constraints today. The second phase extended the range of discharge burnups for 18-month cycles by using fuel enriched in excess of 5 wt%. The neutronic study used state-of-the-art reactor physics methods to accurately determine enrichment requirements. Energy requirements were consistent with today’s high capacity factors (>98%) and short (15-day) refueling outages. The economic evaluation method considers various component costs including uranium, conversion, enrichment, fabrication and spent-fuel storage costs as well as the effect of discounting of the revenue stream. The resulting fuel cycle costs as a function of cycle length and discharge burnup are presented and discussed. Fuel costs decline with increasing discharge burnup for all cycle lengths up to the maximum discharge burnup considered. The choice of optimum cycle length depends on assumptions for outage costs.

The Economics of Reprocessing versus Direct Disposal of Spent Nuclear Fuel

We assess the economics of reprocessing versus direct disposal of spent fuel. The uranium price at which reprocessing spent fuel from light water reactors (LWRs) and recycling the resulting plutonium and uranium in LWRs would become economic is estimated for a range of reprocessing prices and other fuel cycle costs. The contribution of both fuel cycle options to the cost of electricity is also estimated. A similar analysis is performed to compare fast neutron reactors (FRs) with LWRs. We review available information about various fuel cycle costs, as well as the quantities of uranium likely to be recoverable at a range of future prices. We conclude that the once-through LWR fuel cycle is likely to remain significantly cheaper than recycling in either LWRs or FRs for at least the next 50 yr, even with substantial growth in nuclear power.

Core concept of compound process fuel cycle

This paper presents fast reactor core concept and its feasibility as a part of newly proposed compound process fuel cycle in which spent fuels of light water reactor are multi-recycled without conventional reprocessing but with only pyrochemical processing, fuel re-fabrication and reloading to the fast reactor core. Results of the core survey analyses in order to find out the feasibility of this concept, taking example for BWR MOX spent fuel of 60 GWd/t burn-up, show that four times recycling of LWR spent fuel with the burn-up of more than 300 GWd/t can be achieved without increasing MA content. Such benefits will be expected in this concept as reduction of fuel cycle cost due to simplified reprocessing procedure, reduction of environmental impacts due to reduced high level waste, efficient utilization of nuclear fuel resources, enhancement of nuclear non-proliferation, and suppression of LWR spent fuel pile-up.

Purex co-processing of spent LWR fuels: comparative fuel cycle cost analyses

Nuclear fuel cycle costs for purex reprocessing and co-processing cycles are to be evaluated, by calculating unit costs of recovered, accordingly treated and fabricated products and then comparing those to the unit cost of fresh uranium fuel ready to be loaded into a typical LWR on the once-through cycle.

Performance of the Lead-Alloy-Cooled Reactor Concept Balanced for Actinide Burning and Electricity Production

A lead-bismuth–cooled fast reactor concept targeted for a balanced mission of actinide burning and low-cost electricity production is proposed and its performance analyzed. The design explores the potential benefits of thorium-based fuel in actinide-burning cores, in particular in terms of the reduction of the large reactivity swing and enhancement of the small Doppler coefficient typical of fertile-free actinide burners. Reduced electricity production cost is pursued through a longer cycle length than that used for fertile-free burners and thus a higher capacity factor. It is shown that the concept can achieve a high transuranics destruction rate, which is only 20% lower than that of an accelerator-driven system with fertile-free fuel. The small negative fuel temperature reactivity coefficient, small positive coolant temperature reactivity coefficient, and negative core radial expansion coefficient provide self-regulating characteristics so that the reactor is capable of inherent shutdown during major transients without scram, as in the Integral Fast Reactor. This is confirmed by thermal-hydraulic analysis of several transients without scram, including primary coolant pump trip, station blackout, and reactivity step insertion, which showed that the reactor was able to meet all identified thermal limits. However, the benefits of high actinide consumption and small reactivity swing can be attained only if the uranium from the discharged fuel is separated and not recycled. This additional uranium separation step and thorium reprocessing significantly increase the fuel cycle costs. Because the higher fuel cycle cost has a larger impact on the overall cost of electricity than the savings from the higher capacity factor afforded through use of thorium, this concept appears less promising than the fertile-free actinide burners.