ADS Reactor Research Articles

Computational Analysis of the Kinetic Processes of Microbial Electrolysis Cell-Assisted Anaerobic Digestion Using the ADM1

This study deals with the computational analysis of the kinetic processes of microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) for treating raw-waste-activated sludge (WAS), compared to conventional AD, as well as investigating the effect of the organic loading rate (OLR) on the system’s performance. The aim was to derive a mathematical model for the study of MEC-AD using the ADM1 framework, which can be utilized to extract the effect of an applied potential on the kinetics of AD. The experimental data were obtained from the operation of two identical reactors (an AD reactor and an MEC-AD reactor), which were operated at different OLRs. The kinetic parameters extracted from the ADM1 showed that the MEC-AD reactor yielded improved biomass yields, substrate consumption, and first-order disintegration rates, with a predominant contribution to the disintegration of complex particulates, which increased fourfold compared to the AD reactor. Moreover, it enabled operation at higher OLRs (achieving the highest divergence from the AD reactor at the OLR of 4.14 gCOD/(L × d)), therefore accelerating WAS treatment, as well as showing an improved performance at increased solids retention time (SRT). The ADM1 exhibited efficient adaptability and predictability of the kinetic processes and can be effectively used for the optimization of the MEC-AD operation.

Understanding how microbial electrolysis cell assisted anaerobic digestion enhances triclocarban dechlorination in sludge

Microbial electrolysis cell assisted anaerobic digestion (MEC-AD) has recently been considered as an efficient method for degradations of refractory pollutants. To date, however, knowledge about whether and how MEC-AD enhances the degradations of refractory pollutants in sludge remains largely unknown. This study therefore aims to fill this knowledge gap through investigating the transformation of triclocarban (TCC), a widely used antimicrobial agent, in MEC-AD reactors. Experimental results showed that over 83.3 % of TCC was dechlorinated to less toxic dichlorocarbanilide, monochlorocarbanilide and carbanilide in MEC-AD reactors. However, the mass loss of TCC in AD reactor (the electrodeless control) was merely 0.53 %. The presence of electrodes promoted TCC dechlorination in MEC-AD reactors, while the applied voltages (0.6 and 0.8 V) promoted hydrogenotrophic methanogenesis. H2-utilizing Nitrospira and homoacetogenic Acetobacterium were recognized as potential TCC dechlorinators, with their abundances in the planktonic sludge of MEC-AD reactors being 5.0–16.5 times higher than those in AD reactor. The carbon brush electrodes in MEC-AD reactors caused the enrichment of acetoclastic Methanothrix and the complete removal of acetic acid, which thereby thermodynamically accelerated homoacetogenesis and H2-producing acetogenesis in the planktonic sludge. Moreover, the direct interspecies electron transfer using hydrogenase as terminal electron acceptor was enhanced in the planktonic sludge of MEC-AD reactors, which could also improve H2 production rate and stimulate the growth and activity of TCC dechlorinators.

Boosting methane production and raw waste activated sludge treatment in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system: The effect of organic loading rate

This study deals with the effect of different organic loading rates (OLRs) on the organic load removal and the productivity of methane, in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system treating raw waste activated sludge (WAS). For comparison, two identical reactors, a control (AD) and a MEC-AD reactor were constructed. Both reactors operated for 131 days, during which different Organic Loading Rates (OLRs) were examined; 1.1, 1.7 and 2.9 gCOD/(L*d). The results showed that the MEC-AD reactor performed better, relative to the AD reactor, at high OLRs. Specifically, the additional total particulate carbon and Kjeldahl nitrogen removal reached 12% and 13%, respectively, at an OLR of 1.7 gCOD/(L*d), while they reached 19% and 13%, respectively, at an OLR of 2.9 gCOD/(L*d). Moreover, the biogas production and the methane content increased by 30% and 6%, respectively, at an OLR of 1.7 gCOD/(L*d) and by 32% and 5%, respectively, at an OLR of 2.9 gCOD/(L*d). The electrochemical measurements indicated that the power output increased from 5 to 30 mW/m2 when the OLR increased from 1.1 to 2.9 gCOD/(L*d). Overall, the results showed that the MEC-AD accelerated and enhanced the WAS treatment, boosting methane productivity.

Calculation of core neutronic parameters in electron accelerator driven subcritical TRIGA reactor

Abstract Investigating the dependence of reactor core neutronic parameters on the accelerator related parameters such as source multiplication coefficient (K s ), beam profile and electron beam energy (E e ), have a significant impact on the design of future ADS reactors and the cost of their construction. Using the MCNPX code, core neutronic parameters were calculated for three eigenvalues levels (k s ) such as axial and radial distributions of neutron flux, effective multiplication coefficient (K eff), photoneutron yield (Y n/e ), net neutron multiplication (M), energy gain (G), energy constant gain (G 0), power peaking factor (P max/P ave), and importance of neutron source (φ*) for the tungsten target in the core of TRIGA reactor which was driven by an electron accelerator. According to the results, when K s increases safety margin and the required accelerator current (I e ) decrease, but the parameters G and φ* increase. Also, using the parabolic spatial distribution for the electron source instead of the uniform spatial distribution, the parameters Y n/e , G and M increase. In addition, by increasing E e from 100 to 500 MeV, Y n/e and G are improved, and I e and accelerating power (p acc) decrease. Therefore, these results suggest that the dependence of reactor core neutronic parameters on accelerator related parameters is necessary to optimize the design cost of an ADS reactor.

Analysis of reusability of ThO2 and spent UO2 fuels enriched with ads in a CANDU reactor

The study presents the analysis of the reusability of ThO2 and spent UO2 fuels enriched in two different ADS reactors fuelled with Minor Actinide. The spent UO2 fuels are taken out from pressurized water reactor and CANDU spent fuels. For this analysis, the CANDU-37 reactor having a total fission thermal power of 2156 MW is considered and 14 different cases of enriched fuels taken from the previous enrichment processes are analysed by burning in this reactor. The 3-D and time-dependent critical burn up calculations are carried out by using the MCNP 2.7 code. To determine the effective burn time of each case, these calculations are performed until the values of kinf decrease to about the criticality thresh old of 1.05 for all investigated cases. The percent ages of the 239Pu and 233U fissile isotopes appear to be below weapons-grade plutonium and uranium, respectively, in all enriched fuel cases. At the end of effective burn times, the burnup values can reach the values varying in the range of 26.770 and 33.540 GWd/MTU which are a mean of 3.5-4.5 times the burnup value of the CANDU-37 reactor fed with the NatUO2 fuel. The results of this study bring out that in terms of energy production, the CANDU-37 reactor fuelled with the ThO2 and spent UO2 fuels enriched in ADS designs demonstrates higher neutronic performance than the conventional CANDU-37 reactor.

Simulation of transients in ads reactors in three-dimensional geometry

Accelerator-Driven System, ADS, belong to the new generation of advanced reactors being developed that promise to drastically reduce the life of radioactive waste by, for example, the transmutation process. Subcritical reactor designs of the ADS type have attracted worldwide attention and are the subject of research and development in several countries. The purpose of this work is to simulate transients associated with ADS. It adopted the neutron diffusion model that leads the spatial kinetics equations. These equations are solved by the known numerical method of finite differences. The simulations are performed considering transients related to the variations in the intensity of the proton flux provided by the particle accelerator acting in a sub-critical reactor in three-dimensional geometry for two energy groups and six groups of delayed neutron precursors.

Massimo Salvatores’ seminal ideas and comprehensive views on nuclear fuel cycle studies

Massimo Salvatores provided fundamental innovations to the European and international Nuclear Fuel Cycle (NFC) studies, in particular on analysis of Partitioning and Transmutation (P&T) strategies, and introduced them to KIT. His visions and guidance triggered an advanced approach to such studies, with the final aim to maximize synergies of different nuclear energy policies at local and regional levels. He recognized that several different aspects have to be taken into account in the NFC activities, ranging from national polices, to the role of Pu as resource or as a waste, up to the implementation of P&T options with innovative reactor concepts. Such huge contribution inherited from Massimo is a result of the key role he played in the main projects worldwide related to both the NFC studies and the design and assessment of ADS and Low Conversion ratio fast reactor systems. In the present paper, we provide an overview of the work performed by Massimo and his colleagues at the Karlsruhe Institute of Technology, emphasising the innovative elements introduced by Massimo on the back-end of the fuel cycle with focus on P&T of the spent nuclear fuel. The key innovations achieved by Massimo and his KIT team presented hereafter are the introduction of NFC regional scenario studies, the consideration of safety and transmutation assessments of innovative burner reactor concepts, and the effect of the propagation of the existing uncertainties on fuel cycle scenarios simulation results.

Use of citric acid for reducing CH4 and H2S emissions during storage of pig slurry and increasing biogas production: Lab- and pilot-scale test, and assessment

The use of sulfuric acid (SA) for reducing greenhouse gases (GHGs, mainly CH4) emissions in manure management encounters with problems related with safety issue and increased H2S emissions. In the present study, citric acid (CA) as an alternative to SA was assessed in the lab-scale experiment at various dosages (pH 5.0–7.0), and then confirmed in the pilot-scale tank (effective volume of 30 ton). During 35 d of pig slurry (PS) storage at 30 °C, it was found that the CA addition to initial pH down to 6.5 could lead negligible reduction, while 85–99% and 48–72% reduction of CH4 and H2S emissions were achieved at pH ≤ 6.0, respectively. The similar reduction performance was confirmed (control vs. pH 6.0) in the pilot-scale test, but, interestingly, two times higher CH4 emissions of 123.7 kg CO2 eq./ton PS was detected caused by the automatic temperature increase (≥35 °C). The pH of acidified PS did not exceed 6.5 during the whole storage period, while it was maintained 7.3–7.7 in the control. A continuous AD reactor fed with acidified PS exhibited a higher CH4 yield of 10.0 m3 CH4/ton PS, compared to the control (5.7 m3 CH4/ton PS), due to the preservation of organic matters and added CA. In overall, about 8.5 [(4.4, storage) + (4.1, biogas)] kg of CH4/ton PS was generated from raw PS and it was reduced to 7.8 [(0.7, storage) + (7.1, biogas)] kg of CH4/ton PS by CA-acidification. Despite the carbon footprint for manufacturing CA, it was calculated that GHG reduction of 107 kg CO2 eq./ton PS could be attained by CA-acidification. In terms of economic profit, it was estimated that 6.3 USD/ton PS can be gained by CA-acidification, while it was 2.4 USD/ton PS in case of control.

Impact of pyrochar and hydrochar derived from digestate on the co-digestion of sewage sludge and swine manure

Four kinds of biochar were obtained by pyrolysis carbonization and hydrothermal carbonization from swine manure digestate, i.e. pyrochar (HC, HC-Fe) and hydrochar (HTC, HTC-Fe). Batch fermentation was conducted to compare their effects on the co-digestion of sewage sludge and swine manure. Both pyrochar and hydrochar present positive effect on methane production, nevertheless the higher methane yields were obtained in HTC and HTC-Fe digesters. No advantage was observed for the iron impregnation. The maximum methane yield was 308.4 mL/g VS in HTC digester, which was 27% and 49% higher than HC and Control, respectively. The surface functional groups of hydrochar are more abundant than pyrochar, which is favorable for promoting the syntrophic anaerobic metabolism, as revealed by the promoted substrate hydrolysis and VFAs consumption rate. Thus, it is proposed to convert swine manure digestate to hydrochar, which can be recirculated back to the AD reactor to increase the digestion efficiency.

A model predictive optimal control system for the practical automatic start-up of anaerobic digesters

The optimal automatic start-up of anaerobic digesters has remained an elusive problem over the years to be solved at the lowest possible costs, including that of process monitoring. In this work, a non-linear model predictive control (NMPC) system was developed, under two proposed configurations, for the optimal start-up of anaerobic digesters treating soluble non-recalcitrant substrates. The minimum set of low cost practical control variables (CVs) selected for process start-up include (i) the effluent quality as acetate COD, (ii) the level of aceticlastic methanogenic biomass in the reactor, and (iii) the methane production rate (only for one of the NMPC configurations). The manipulated variables (MVs) consist of the volumetric inflow rates of the organic substrate, dilution water, and of a possible concentrated alkali addition. To be able to apply the above selected CVs (technically and economically feasible to measure/estimate), a simplified tailored AD model was specifically designed as the prediction model, integral part of the NMPC system. The NMPC system developed was evaluated for a case scenario consisting of the automatic start-up of a high rate AD reactor treating a readily biodegradable carbohydrate based substrate. The AD plant was virtually represented by the complex Anaerobic Digestion Model No. 1. Compared to other manual start-up strategies, the two configurations of the NMPC developed appeared to reach the target methane production rate faster (39 and 18 days for the NMPC versus 70–75 days for the manual strategies) together with an overall superior CV set-point tracking error performance. Interestingly, the two configurations of the NMPC developed appear to propose two very different, almost opposite, start-up feeding strategies to both eventually start-up the reactor successfully with no process destabilizations throughout. A number of practical scenarios were also considered to evaluate the NMPC configurations for robustness and any possible improvements. These tests indicate that the NMPC objective function formulation is a key factor of the success and robustness exhibited during start-up.

Numerical Investigation of Th-229 Production in an Accelerator Driven System Reactor

The expected increase in radionuclide demand for treatment of various tumor diseases has led to the investigation of alternative production routes to provide sufficient amount of medical isotopes [1]. In Targeted Alpha Therapy (TAT), there is a present and future need for the Ac-225 and Bi-213, as the most promising alpha emitting isotopes, one of the limited ways to provide these radioisotopes is by production of Th-229 in reactor route [2][3]. The present study conducted to investigate the production of Th-229 to expand the availability of Ac-225 and Bi-213 in innovative nuclear reactor concept like Accelerator Driven System reactor (ADS)[4], which is a subcritical reactor and currently in development that predict to play an important role in the transmutation process of heavy elements and isotopes production. The possibility of producing Th-229 from neutron transmutation of Ra-226 are numerically investigated for simple model of ADS reactor consist of two zones, inner region with fast neutron spectra and outer region with thermal neutron spectra, and the subcritical core coupled with external neutron source. The calculations of transmutation behavior and mass ratio for the produced isotopes are conducted by using Monte Carlo N-particle Transport (MCNPX) code. This research was supported by International Center for Theoretical Physics and The Institute of International Education Scholar Rescue Fund. My deep thanks to colleagues from Institute for Safety Problems of Nuclear Power Plants, Ukraine who provided expertise that assisted the research. [1]E. R. Birnbaum, L. J. Bitteker, A. Couture, and M. E. Fassbender, “Ac and Ra-223 Production via 800 MeV Proton Irradiation of Natural Thorium Targets,” vol. 836.[2]J. R. Griswold et al., “Large scale accelerator production of Ac-225: Effective cross sections for 78–192 MeV protons incident on Th-232 targets,” Appl. Radiat. Isot., 2016.[3]S. Hogle et al., “Reactor production of Thorium-229,” Appl. Radiat. Isot., vol. 114, pp. 19–27, 2016.[4]H. Aït Abderrahim, P. Baeten, D. De Bruyn, and R. Fernandez, “MYRRHA - A multi-purpose fast spectrum research reactor,” in Energy Conversion and Management, 2012, vol. 63, pp. 4–10.

Effects of aspect ratio and component ratio on binary-mixed discharging pebble flow in hoppers

As an important class of particle flows in industrial applications, hopper flows, particularly those using pebbles (diameters dp ~O(10-2) m), play a significant role in nuclear reactor engineering, e.g. HTGR and ADS reactors. However, the features and influencing factors of the binary mixture discharge have not yet been widely investigated. In this study, the discrete element method (DEM) simulation was adopted to analyze the discharge flow of binary mixtures consisting of ellipsoids and spheres in a hopper. After a model validation, the effects of particle aspect ratio (Ra, the ratio of the major axis to the minor axis) of ellipsoids and component ratio (Rn, the ratio of the ellipsoid number to the sphere number) of ellipsoids to spheres were analyzed. Flow patterns were visualized by colored pebble stripes according to pebbles' initial heights. Particle discharge flow rates were computed to examine their relations to particle aspect ratios and component ratios. The force structure and distributions of the binary mixtures were also explored. Results showed that pebble stripes followed quadratic function profiles. Adding ellipsoids was advantageous for particles discharging at lower particle aspect ratios (Ra≤2), while impedimental at large particle aspect ratios (Ra≥3). The discharge flow rate was inversely proportional to the particle aspect ratio at fixed component ratios, and linearly proportional to the 1/4th power of the component ratio at fixed particle aspect ratios. In addition, the discharge flow rate showed low sensitivity to the initial packing states of particles when the particle aspect ratio and component ratio were fixed.

Numerical Investigation of Th-229 Production in an Accelerator Driven System Reactor

The expected increase in radionuclide demand for treatment of various tumor diseases has led to the investigation of alternative production routes to provide sufficient amount of medical isotopes [1]. In Targeted Alpha Therapy (TAT), there is a present and future need for the Ac-225 and Bi-213, as the most promising alpha emitting isotopes, one of the limited ways to provide these radioisotopes is by production of Th-229 in reactor route [2][3]. The present study conducted to investigate the production of Th-229 to expand the availability of Ac-225 and Bi-213 in innovative nuclear reactor concept like Accelerator Driven System reactor (ADS)[4], which is a subcritical reactor and currently in development that predict to play an important role in the transmutation process of heavy elements and isotopes production. The possibility of producing Th-229 from neutron transmutation of Ra-226 are numerically investigated for simple model of ADS reactor consist of two zones, inner region with fast neutron spectra and outer region with thermal neutron spectra, and the subcritical core coupled with external neutron source. The calculations of transmutation behavior and mass ratio for the produced isotopes are conducted by using Monte Carlo N-particle Transport (MCNPX) code. This research was supported by International Center for Theoretical Physics and The Institute of International Education Scholar Rescue Fund. My deep thanks to colleagues from Institute for Safety Problems of Nuclear Power Plants, Ukraine who provided expertise that assisted the research. [1]E. R. Birnbaum, L. J. Bitteker, A. Couture, and M. E. Fassbender, “Ac and Ra-223 Production via 800 MeV Proton Irradiation of Natural Thorium Targets,” vol. 836.[2]J. R. Griswold et al., “Large scale accelerator production of Ac-225: Effective cross sections for 78–192 MeV protons incident on Th-232 targets,” Appl. Radiat. Isot., 2016.[3]S. Hogle et al., “Reactor production of Thorium-229,” Appl. Radiat. Isot., vol. 114, pp. 19–27, 2016.[4]H. Aït Abderrahim, P. Baeten, D. De Bruyn, and R. Fernandez, “MYRRHA - A multi-purpose fast spectrum research reactor,” in Energy Conversion and Management, 2012, vol. 63, pp. 4–10.

Increasing capacity of an anaerobic sludge digester through FNA pre-treatment of thickened waste activated sludge

Free nitrous acid (FNA) pre-treatment has been previously demonstrated to be effective in enhancing methane production and volatile solids (VS) destruction in the anaerobic digestion of waste activated sludge for an equivalent hydraulic retention time (HRT). We hypothesise that, due to enhancement of hydrolysis kinetics, FNA pre-treatment will also allow reduction in the HRT while retaining performance. This would allow for improvement of capacity constrained digesters. Two anaerobic sludge digesters (control-experiment) were fed with the same thickened waste activated sludge (TWAS) from a full-scale plant for 6 months. With 24 h pre-treatment of TWAS at an FNA concentration of 6.1 mgN/L (NO2-N = 250 mg/L, pH = 5.0, T = 25 °C), the HRT for the experimental anaerobic digester was progressively reduced from 15 days to 12 days and then to 7.5 days. In comparison, the control reactor was operated at a constant HRT of 15 days, representing typical loading conditions. With the shortened HRTs, the experimental AD reactor achieved VS destruction at 36.9 ± 0.8% (12 days) and 36.8 ± 1.0% (7.5 days), representing 30–40% relative increase in comparison to the control reactor (at 26.5 ± 0.8% and 28.3 ± 0.7%, respectively, in the same two periods). This was supported by a similar (31–35%) increase in the methane production per unit of VS fed. The volumetric methane production rate of the experimental digester was increased by 165% at HRT of 7.5 days compared with the control digester at HRT of 15 days. The results demonstrated that FNA pre-treatment of TWAS can substantially increase the capacity of an anaerobic sludge digester, with a highly favourable economic outcome.

Adsorption of volatile polonium species on metals in various gas atmospheres: Part III – Adsorption of volatile polonium on stainless steel 316L

Abstract This article summarizes the results obtained studying the interaction between polonium and stainless steel 316L in different atmospheres by the thermochromatography method. This issue is particularly important in terms of licensing of the MYRRHA prototype ADS reactor, where highly radiotoxic α-emitting polonium isotopes are produced in lead-bismuth eutectic used as both spallation target material and coolant, while stainless steel 316L is going to be the main structural material. The polonium adsorption enthalpy on stainless steel 316L in inert atmosphere was measured as −147±6 kJ mol−1. The findings obtained using reducing atmospheres show that the affinity of polonium for stainless steel 316L increases with the metallic character of the stainless steel surface. The presence of moisture in inert and reducing atmosphere does not significantly influence the polonium adsorption. Oxidizing atmospheres induce the formation of polonium dioxide which has a stronger interaction with the stainless steel 316L, with an adsorption enthalpy of −225±6 kJ mol−1. A prolonged exposure of the stainless steel to strong oxidants, such as pure oxygen, reduces the metallic character of the stainless steel surface and, consequently, its affinity to the polonium oxide. Furthermore, it was found that in all experiments at least 5 ppm of the total polonium present in the starting material were not retained on the stainless steel 316L surface at all.

Effect of Minimizing d-Limonene Compound on Anaerobic Co-digestion Feeding Mixtures to Improve Methane Yield

The purpose of this work was to assess the enhancement of the anaerobic digestion process of sewage sludge by the addition of orange peel as co-substrate. In this experimental study, an evaluation of the co-digestion process in a semi-continuous stirred tank reactor was carried out under mesophilic conditions (37 ± 0.2 °C) during an operation time up to 315 days. All trials were performed at a hydraulic retention time of 15 days and the AD reactor was fed daily with a mixture of sewage sludge and orange peel pulp, previously prepared. The organic loading rate was kept at 1.80 ± 0.31 g VS L−1 day−1 in all trials. A reference scenario (T0), mono-digestion, was performed using sewage sludge as substrate (primary sludge and activated sludge, 40:60, v/v). Thereafter, two different anaerobic co-digestion trials were carried out, one with pre-treated orange peel (T1) and the other with reduced d-limonene content (T2). Trials with pre-treated orange peel (T1 and T2) led to two- and threefold improvements in biogas and methane yields, compared with the reference scenario (T0). Furthermore, the reduction of d-Limonene content (T2) increased the methane yield by around 70% compared with T1. Therefore, it was proved that the sieving pre-treatment is effective to avoid the inhibitory effect of d-limonene.

Support to the identification of anomalies in an external neutron source using Hurst Exponents

A new methodology is proposed here to identify anomalies in the neutron flux as a result neutron production trips in an Accelerator Driven System - ADS type reactor. This methodology is based on the calculation of Hurst exponents, where the neutron flux as monitored in the reactor core is treated as a temporal series. In several recent articles, related to fractional diffusion, the Hurst exponent is used as an estimate for the order of the fractional derivative. Our object of study considered a reactor based on the Myrrha simulated with the Serpent Monte Carlo code for two kinds of trips occurred in the production of neutrons, as follows: a Peak of Production (PP), the Unprotected* Accelerator Beam Overpower (UABO), and the spurious Beam Trip (BT). In order to estimate the Hurst exponent it was used two different methods, namely the Rescaled Range Analysis (R/S) and the Detrended Fluctuation Analysis Method (DFA). The results obtained showed that the R/S methodology had some advantages in a comparison with the DFA in indicating the occurrence of those anomalies. Also being able to provide a scale for the assessment of the intensity of the trip occurred, showing to be an useful tool to support anomaly identification in the neutron flux of ADS reactors.

Preliminary CFD Assessment of an Experimental Test Facility Operating with Heavy Liquid Metals

The CFD analysis of a Venturi nozzle operating in LBE (key component of the CIRCE facility, owned by ENEA) is presented in this paper. CIRCE is a facility developed to investigate in detail the fluid-dynamic behavior of ADS and/or LFR reactor plants. The initial CFD simulations have been developed hand in hand with the comparison with experimental data: the test results were used to confirm the reliability of the CFD model, which, in turn, was used to improve the interpretation of the experimental data. The Venturi nozzle is modeled with a 3D CFD code (STAR-CCM+). Later on, the CFD model has been used to assess the performance of the component in conditions different from the ones tested in CIRCE: the performance of the Venturi is presented, in terms of pressure drops, for various operating conditions. Finally, the CFD analysis has been focused on the evaluation of the effects of the injection of an inert gas in the flow of the liquid coolant on the performance of the Venturi nozzle.

Numerical Analysis for Transients in External Source Driven Reactors

The main purpose of this paper is to perform a numerical analysis of the Neutron Spatial Kinetic Equations, subject to transients of the External Neutron Source, by applying the Implicit Euler Method as well as the Runge-Kutta Method in order to check which methods are best applicable in transients caused by External Neutron Source. For this purpose, a one-dimensional ADS reactor with a constant external source was simulated based on the geometry of ANL-BSS-6 reactor for benchmark effects.

Dependence of neutron rate production with accelerator beam profile and energy range in an ADS-TRIGA RC1 reactor

Abstract Lead, mercury, tantalum and tungsten were used as target material for calculation of spallation processes in an ADS-TRIGA RC1 reactor. The results show that tungsten has the highest neutron production rate. Therefore it was selected as target material for further calculations. The sensitivity of neutron parameters of the ADS reactor core relative to a change of beam profile and proton energy was determined. The core assembly and parameters of the TRIGA RC1 demonstration facility were used for the calculation model. By changing the proton energy from 115 to 1 400 MeV by using the intra-nuclear cascade model of Bertini (INC-Bertini), the quantity of the relative difference in % for energy gain (G) and spallation neutron yield (Yn/p), increases to 289.99 % and 5199.15 % respectively. These changes also reduce the amount of relative difference for the proton beam current (Ip) and accelerator power (Pacc), 99.81 % and 81.28 % respectively. In addition, the use of a Gaussian distribution instead of a uniform distribution in the accelerator beam profile increases the quantity of relative difference for energy gain (G), net neutron multiplication (M) and spallation neutron yield (Yn/p), up to 4.93 %, 4.9 % and 5.55 % respectively.