Transmutation Reactor Research Articles

The results of the transmutation of fission fragments in the spectrum of neutrons of thermal and fast reactors

Radioactivity of spent nuclear fuel (SNF) discharged from nuclear reactor core is determined during the first 100 years by fission fragments (FF), after that the main contribution in the SNF activity is made by actinides. Existing scenarios of SNF handling are based on the transmutation of minor actinides (MA) into fission fragments accomplished in fast reactors. Scenarios of transmutation of fission fragments in thermal and fast neutron spectra and time-dependent radiation characteristics are examined in the present study. Nuclide composition of fission fragments is taken from the results of simulation of burnup of 439GT fuel assembly (TVSA type) for VVER-1000 nuclear reactor during 3 years performed using MCU-5 software complex. The obtained data were used for determining starting nuclide composition for different cooling-down times prior to the beginning of transmutation (irradiation in neutron fluxes) to be input in the ORIGEN2 code.The following three options of irradiation of fission fragments are presented: transmutation without cooling down, cooling down fission fragments during 4 years prior to irradiation, cooling down fission fragments during 30 prior to irradiation. Duration of irradiation was selected to be equal to 3 and 15 years. Efficiency of transmutation was determined using time-dependent “transmutation factor” equal to the ratio of radioactivity of nuclides in the process of transmutation and after its completion to their radioactivity without transmutation.The calculated values of transmutation factors proved to be noticeable only during irradiation in reactor core: these values reached 5–10 and were dependent only on the duration of fission fragment cooling down prior to the beginning of transmutation. After removal of fission fragments from neutron flux transmutation factor decreased to unity within several years. After one hundred more years after irradiation in neutron spectrum of thermal reactor transmutation factor reduces to 0.8–0.5 depending on the duration of the transmutation process. Slight growth of transmutation factor to the values of 1.2–1.8 was observed after irradiation in fast reactor spectrum within the time interval of 200–1000 years and after 1000 years following this its reduction to the value of 0.9–0.7 was noted.The main conclusion is that purposeful incineration of fission fragments is senseless because only insignificant gain in radioactivity (a little less than by the factor two) is achieved after 1000 years.The indifference of fission fragments with regard to transmutation can be partially explained by the fraction of stable nuclides which increases with extension of the period of fission fragments cooling down. Upon completion of the cycle of fuel use it contains approximately 15% of stable nuclides among fission fragments, and after 30 years of cooling down the fraction of stable isotopes reaches 85%.

Solving the Spent Nuclear Fuel Problem by Fissioning Transuranics in Subcritical Advanced Burner Reactors Driven by Tokamak Fusion Neutron Sources

The Georgia Tech concept of the Subcritical Advanced Burner Reactor (SABR) spent nuclear fuel (SNF) transmutation reactor and supporting analyses to date are summarized. SABR is based on the fast reactor physics and technology prototyped in Experimental Breeder Reactor-II (EBR-II) and proposed for the Integral Fast Reactor and the PRISM Reactor and on the tokamak fusion neutron source physics and technology that will be prototyped in ITER. Preliminary fuel cycle calculations indicate that subcritical operation would enable a proliferation-resistant fuel reprocessing cycle that would safely accommodate fuel with up to 100% TRU content and that introduction of SABRs in a 1-to-3 power ratio with light water reactors would reduce the required SNF high-level waste repository capacity (defined on the basis of decay heat released) by a factor of 10 to 100. Preliminary dynamic safety calculations indicate that SABRs could be shut down to the decay heat level by turning off the plasma heating power without core damage in loss of heat sink, loss of flow, and loss of power accidents, but that additional decay heat removal capability is needed in the case of total loss of primary or secondary system pumping power.

Assessment of transient characteristics of fast reactors and influences of minor actinides using neutron transport method

Summary Partitioning and transmutation of the minor actinides (MAs) from nuclear power plants are of importance for the nuclear-energy sustainable development. Fast reactors are applied to transmutation for the hard neutron spectrum and high neutron flux. However, the safety-related neutronic parameters will become worse when large amounts of MAs are loaded. In this paper, transients of a 600 MWe sodium-cooled fast reactor for MA transmutation are analyzed by using neutron transport simulation. The control rod withdrawal transients are calculated. Two cases are compared to investigate the influence of loading MAs into the fast reactor core. One is the common core loaded with mixed oxide (MOX) fuel, and the other one is the transmutation core loaded with MOX fuel and MAs. The results indicate that in order to apply similar operation criterion with the common core, the transmutation core with 6% weight fraction of MAs should be operated with more than 30% power reduction. In addition, the results of the transport-based transient analysis and the point kinetics transient analysis are compared. There are noticeable differences between them, which indicate that the usual way based on the point kinetics calculation is not suitable well for simulating the control rod introduced transients. Copyright © 2017 John Wiley & Sons, Ltd.

Study of an optimal configuration of a transmutation reactor based on a low-aspect-ratio tokamak

We determine the optimal configuration of a transmutation reactor based on a low-aspect-ratio tokamak. For self-consistent determination of the radial build of the reactor components, we couple a tokamak systems analysis with a radiation transport calculation. The inboard radial build of the reactor components is obtained from plasma physics and engineering constraints, while outboard radial builds are mainly determined by constraints on neutron multiplication, the tritium-breeding ratio, and the power density. We show that the breeding blanket model has an effect on the radial build of a transmutation blanket. A burn cycle has to be determined to keep the fast neutron fluence plasma-facing material below its radiation damage limit. We show that the radial build of the transmutation reactor components and the equilibrium fuel cycle play a major role in determining the transmutation characteristics.

Preliminary design of inner radius of spallation target of an accelerator driven subcritical reactor for waste transmutation (ADS-NWT)

This paper presented preliminary design studies of inner radius of spallation target for lead-bismuth cooled accelerator driven sub-critical reactor, aimed at reducing proton beam current while simultaneously maintaining high Minor Actinides transmutation performance. Lead-bismuth eutectic (LBE) and uranium-free metallic dispersion fuel were used as the coolant and the fuel for this 1000 MWt reactor. By taking Proton Transmutation Support Ratio (PTSR) as an evaluation index, the inner radius of the spallation target was designed for this reference reactor and the optimized design proposal could obtain the higher transmutation performance. The preliminary study found that when the inner radius of the spallation target ran up to a certain value, the spallation neutron yield would have greater influence on the transmutation performance.

A study on transmutation of LLFPs using various types of HTGRs

In order to investigate the potential of high temperature gas-cooled reactors (HTGRs) for transmutation of long-lived fission products (LLFPs), numerical simulation of four types of HTGRs were carried out. In addition to the gas-turbine high temperature reactor system “GTHTR300”, which is the subject of our previous research, a small modular HTGR plant “HTR50S” and two types of plutonium burner HTGRs “Clean Burn with MA” and “Clean Burn without MA” were considered. The simulation results show that an early realization of LLFP transmutation using a compact HTGR may be possible since the HTR50S can transmute fair amount of LLFPs for its thermal output. The Clean Burn with MA can transmute a limited amount of LLFPs. However, an efficient LLFP transmutation using the Clean Burn without MA seems to be convincing as it is able to achieve very high burn-ups and produce LLFP transmutation more than GTHTR300. Based on these results, we propose utilization of variety of HTGRs for LLFP transmutation and storage.

Design and Optimization for the Windowless Target of the China Nuclear Waste Transmutation Reactor

A windowless spallation target can provide a neutron source and maintain neutron chain reaction for a subcritical reactor, and is a key component of China's nuclear waste transmutation of coupling accelerator and subcritical reactor. The main issue of the windowless target design is to form a stable and controllable free surface that can ensure that energy spectrum distribution is acquired for the neutron physical design when the high energy proton beam beats the lead–bismuth eutectic in the spallation target area. In this study, morphology and flow characteristics of the free surface of the windowless target were analyzed through the volume of fluid model using computational fluid dynamics simulation, and the results show that the outlet cross section size of the target is the key to form a stable and controllable free surface, as well as the outlet with an arc transition. The optimization parameter of the target design, in which the radius of outlet cross section is 60 ± 1 mm, is verified to form a stable and controllable free surface and to reduce the formation of air bubbles. This work can function as a reference for carrying out engineering design of windowless target and for verification experiments.

A Strategic Opportunity for Magnetic Fusion Energy Development

The realities of energy development and the perception of and support for magnetic fusion in the US are briefly summarized as background for proposing a strategic opportunity for magnet fusion energy development as fusion neutron sources for subcritical advanced burner (transmutation) reactors for the destruction of long-lived transuranics in spent nuclear fuel.

Transmutation performance analysis on coolant options in a hybrid reactor system design for high level waste incineration

A fusion–fission hybrid reactor (FFHR) is one of the most attractive candidates for high level waste transmutation. The selection of coolant affects the transmutation performance of a FFHR. LiPb coolant, as a conventional coolant for a FFHR, has problems such as reduction in neutron economic and magneto-hydro dynamics (MHD) pressure drop. Therefore, in this work, transmutation performance is evaluated and compared for various coolant options such as LiPb, H2O, D2O, Na, PbBi, LiF-BeF2 and NaF-BeF2 applicable to a hybrid reactor for waste transmutation (Hyb-WT). Design parameters measuring performance of a hybrid reactor were evaluated by MCNPX. They are keff, energy multiplication factor, neutron absorption ratio, tritium breeding ratio, waste transmutation ratio, support ratio and radiotoxicity reduction. Compared to LiPb, H2O and D2O are not suitable for waste transmutation because of neutron moderation effect. Waste transmutation performances with Na and PbBi are similar to each other and not different much from LiPb. Even though molten salt such as LiF-BeF2 and NaF-BeF2 is good for avoiding MHD pressure drop problem, waste transmutation performance is dropped compared with LiPb.

Porous metal oxide microspheres from ion exchange resin

This study is devoted to the synthesis and the characterization of porous metal oxide microsphere from metal loaded ion exchange resin. Their application concerns the fabrication of uranium-americium oxide pellets using the powder-free process called Calcined Resin Microsphere Pelletization (CRMP). Those mixed oxide ceramics are one of the materials envisaged for americium transmutation in sodium fast neutron reactors. The advantage of such microsphere precursor compared to classical oxide powder is the diminution of the risk of fine dissemination which can be critical for the handling of highly radioactive powders such as americium based oxides and the improvement of flowability for the filling of compaction chamber. Those millimetric oxide microspheres incorporating uranium and americium were synthesized and characterizations showed a very porous microstructure very brittle in nature which occurred to be adapted to shaping by compaction. Studies allowed to determine an optimal heat treatment with calcination temperature comprised between 700–800 °C and temperature rate lower than 2 °C/min. Oxide Precursors were die-pressed into pellets and then sintered under air to form regular ceramic pellets of 95% of theoretical density (TD) and of homogeneous microstructure. This study validated thus the scientific feasibility of the CRMP process to prepare bearing americium target in a powder free manner.

Neutron Damage in the Plasma Chamber First Wall of the GCFTR-2 Fusion-Fission Hybrid Reactor

The successful development of energy-conversion machines based on either nuclear fission or fusion is completely dependent on the behaviour of the engineering materials used to construct the fuel containment and primary heat extraction systems. Such materials must be designed in order to maintain their structural integrity and dimensional stability in an environment involving high temperatures and heat fluxes, corrosive media, high stresses and intense neutron fluxes. However, despite the various others damage issues, such as the effects of plasma radiation and particle flux, the neutron flux is sufficiently energetic to displace atoms from their crystalline lattice sites. It is clear that the understanding of the neutron damage is essential for the development and safe operation of nuclear systems. Considering this context, the work presents a study of neutron damage in the Gas Cooled Fast Transmutation Reactor (GCFTR-2) driven by a Tokamak D-T fusion neutron source of 14.03 MeV. The theoretical analysis was performed by MCNP-5 and the ENDF/B-VII.1 neutron data library. A brief discussion about the determination of the radiation damage is presented, along with an analysis of the total neutron energy deposition in seven points through the material of the plasma source wall (PSW), in which was considered the HT-9 steel. The neutron flux was subdivided into three energy groups and their behaviour through the material was also examined.

Criticality Uncertainty Dependence on Nuclear Data Library in Fast Molten Salt Reactors

Abstract To increase the sustainability of the nuclear fuel cycle, and increase security of nuclear energy, we have been inves- tigating Molten Salt Fast Reactors (MSFR) for transmutation of Minor actinoid (MA) isotopes. In the present work we describe the reactor physics analysis of a Th-TRU MSFR using a LiF-ThF 4 -TRUF3-fuel salt. We investigated the uncertainty of major reactor physics parameters using 3 sets of evaluated nuclear data: JENDL-4.0, JEFF-3.1.2, and ENDF/B-VII.1. The result of our work is that the spread in the multiplication factor is rather large between the sets of nuclear data, while other parameters are by and large the same. The uncertainties due to cross section covariance are large, with Th-232, U-233, and F-19 giving the most important contributions. The isotopic contributions to the uncertainties are quite different between the sets of nuclear data, giving a suspicion that the covariance data may is very different between the evaluations, and a review of the covariance data may be needed.

Characteristics of nuclear waste transmutation based on a tokamak neutron source

The optimum configuration is found of a transmutation reactor based on a tokamak neutron source for an aspect ratio in the range of 1.5–4.0 and fusion power in the range of 100–500 MW, by means of coupled analysis of the tokamak systems and the neutron transport. The dependence of the transmutation characteristics upon the aspect ratio is investigated for the case in which the transmutation reactor produces constant power. For a low-aspect-ratio tokamak, the power density requirement was satisfied with less fusion power, and less radial thickness of the breeding blanket was required to meet a tritium breeding requirement, relative to a high-aspect-ratio tokamak. It was shown that by adjusting the portion of minor actinides contained in the transuranic actinides, the nuclear waste transmutation could be optimized with low fusion power while producing constant power.

Overview of Accelerator Applications in Energy

An overview of the application of accelerators and accelerator technology in energy is presented. Applications span a broad range of cost, size, and complexity and include large-scale systems requiring high-power or high-energy accelerators to drive subcritical reactors for energy production or waste transmutation, as well as small-scale industrial systems used to improve oil and gas exploration and production. The enabling accelerator technologies will also be reviewed and future directions discussed.

Decomposition analysis of the sodium void reactivity of the Korean sodium-cooled fast reactor

Abstract To cope with increasing spent fuel disposals and limited domestic spent fuel storages in Korea, the Korea Atomic Energy Research Institute has developed an advanced sodium-cooled fast reactor for TRU transmutation with an electricity output of 600 MWe (called the KALIMER-600 TRU burner). The design philosophy of the KALIMER-600 TRU burner concept is highly focused on inherent safety mechanisms, i.e., passive responses to abnormal and emergency conditions, and thereby minimizes the need for engineered safety systems. Accordingly, the main concern is on the sodium coolant void reactivity, a very important safety parameter of the KALIMER-600 TRU burner. This study was therefore performed to analyze the sodium void reactivity of the KALIMER-600 TRU burner to the finest resolution possible, e.g., contributions from any isotope in each core region. Such detailed analysis could be valuable and applicable to further optimization of the core passive safety characteristics against severe coolant voiding accident conditions.

Transmutation of nuclear waste with a low-aspect-ratio tokamak neutron source

The transmutation characteristics of transuranics (TRUs) in a transmutation reactor based on a LAR (Low-aspect-ratio) tokamak as a neutron source are investigated. The optimum radial build of a transmutation reactor is found by using a coupled analysis of the tokamak systems and the neutron transport. The dependences of the transmutation characteristics on the aspect ratio A in the range of 1.5 to 2.5 and on the fusion power in the range of 150 to 500 MW are investigated. An equilibrium fuel cycle is developed for effective transmutation, and show that with one unit of the transmutation reactor based on the LAR tokamak producing fusion power in the range of a few hundred MWs, up to 3 PWRs (1.0 GW e capacity) can be supported with a burn-up fraction larger than 50%.

Nuclear waste transmutation performance assessment of an accelerator driven subcritical reactor for waste transmutation (ADS-NWT)

As a concept of lead–bismuth cooled accelerator driven sub-critical reactor, ADS-NWT was proposed for nuclear waste transmutation by FDS Team. In this paper, preliminary transmutation performance assessment on ADS-NWT was performed by using metallic dispersion fuel and metal alloy fuel. The studies were committed to improving the Discharge Transmutation Support Ratio (DTSR) under three key design constraints. Subject to the design constraints on the effective multiplication factor, the peak linear power and the peak fast neutron fluence, the design studies had been performed for ADS-NWT blanket. From these studies, the results showed that the maximum DTSR was primarily related to the MA/Pu ratio, the peak fast neutron fluence and fuel design under imposed design constraints. The maximum DTSR could be ∼47 in one refueling cycle time when the thermal power was fixed to 1000MW and the effective multiplication factor was 0.98 based on the specific design.

Transmutation characteristics of minor actinides in a low aspect ratio tokamak fusion reactor

The transmutation characteristics of minor actinides in the transmutation reactor of a low aspect ratio (LAR) tokamak are investigated. One-dimensional neutron transport and burn-up calculations coupled with a tokamak systems analysis were performed to determine optimal system parameters. The dependence of the transmutation characteristics, including the neutron multiplication factor, produced power, and the transmutation rate, on the aspect ratio A in the range of 1.5–2.0 was examined. By adding Pu239 to the transmutation blanket as a neutron multiplication material, it was shown that a single transmutation reactor producing a fusion power of 150MWth can destroy minor actinides contained in the spent fuels for more than 38units of 1GWe pressurized water reactors (PWRs) while producing a power in the range of 1.8–6.8GWth.

Resolution of Fission and Fusion Technology Integration Issues: An Upgraded Design Concept for the Subcritical Advanced Burner Reactor

The conceptual design of the subcritical advanced burner reactor (SABR), a 3000-MW(thermal) annular, modular sodium pool–type fast reactor, fueled by metallic transuranic (TRU) fuel processed from discharged light water reactor fuel and driven by a tokamak D-T fusion neutron source based on ITER physics and technology, has been substantially upgraded. Several issues related to the integration of fission and fusion technologies have been addressed, e.g., refueling a modular sodium pool reactor located within the magnetic coil configuration of a tokamak, achieving long-burn quasi-steady-state plasma operation, access for heating and current drive power transmission to a toroidal plasma surrounded by a sodium pool fast reactor, suppression of magnetohydrodynamic effects in a liquid metal coolant flowing in a magnetic field, tritium self-sufficiency in a TRU transmutation reactor, shielding the superconducting magnets from fusion and fission neutrons, etc. A design concept for a SABR that could be deployed within 25 years, based on the IFR/PRISM metal-fuel, sodium pool fast reactor technology and on the ITER fusion physics and technology, is presented. This design concept can be used for realistic fuel cycle, dynamic safety, and other performance analyses of a SABR.

Improved multi-group cross sections with resonance treatment for future applications involving minor actinides

In the future study for thorium reactors and minor actinide transmutation reactors, resonance self-shielding treatment for them becomes remarkable issue for criticality and isotope depletion. Resonance treatment for important minor actinides and other resonant absorbers has been carried out with subgroup method. The updated multi-group cross sections and subgroup data is replaced with existing multi-group library. The results from neutron transport code nTRACER with updated multi-group cross section library were compared with existing library and solutions from MCNP. The resonance interaction of uranium with important minor actinides has been accommodated through modified interference treatment by interference correction in subgroup method. The results for cross sections and multiplication factor for pin and assembly problems showed improvement from systematic resonance treatment for resonant absorber nuclides including 237Np and 243Am.