Burn-up Scheme Research Articles

Design study of a 450MW thermal Modified CANDLE fast reactor using helium gas as a coolant

The Modified CANDLE (MCANDLE) burnup scheme divides the reactor core into several regions in an axial or radial direction with equal volume. It works like the CANDLE burnup scheme except that, in the CANDLE burnup scheme, the reactor core is divided into three main regions in the axial direction. Namely, spent fuel, burning region and fresh fuel region. In this study, the design of a modular modified CANDLE fast reactor using helium gas as a coolant has been performed. One of the important roles of a modified CANDLE fast reactor is that it can utilize natural uranium as fuel without the need for enrichment or reprocessing. This type of reactor can be used, including in developing countries, without the nuclear proliferation problem. Using helium gas as a coolant gives hope for a fast reactor due to its properties, such as its less neutron absorption, less radioactive, and as helium is an inert gas, prevents chemical reactions with other materials. The study was performed on a rector with a thermal power of 450MWth. The active core was divided into ten regions with equal volume in radial directions. The refueling scheme has been optimized every ten years of burnup to obtain a good reactor design. In the beginning, the fuel was put in the first region after ten years of burnup was moved to the second region, after another ten years of burnup was moved to the third region and so on until the tenth region where the fuel gets out. The neutronic calculation has been performed using the SRAC (Standard Reactor Analysis Code system). The collision probability method (PIJ) was employed for cell burnup calculation, and CITATION was used for the reactor core design with JENDL 4.0 as the nuclear data library.

Neutronic performance of 208Pb-Bi eutectic-cooled fast reactor with uranium nitride fuel (enriched 15N)

Fast reactors (FRs) require more uranium enrichment than LWRs and fuel reprocessing. The solution proposed to address these issues is to use the modified CANDLE burnup scheme on the reactor core. The use of uranium nitride (UN) as fuel was proposed because the UN fuel has several advantages, such as high melting point, high heavy metal density, and large thermal conductivity. However, using UN as a fuel can produce the radioactive isotope 14C via the reaction 14N (n, p)14C. Therefore, in this study, a neutronic analysis was performed in a modified CANDLE fast reactor employing UN and UN (enriched 15N) as fuel using SRAC. The modified CANDLE fast reactor fuelled with UN (99% 15N) has a higher keff than the UN-fuelled reactor with similar parameters. Similarly, the atomic density of fissile nuclides and power density are higher because the 15N isotope has a smaller neutron capture cross-section than the 14N isotope.

Design study of small modular gas-cooled fast reactor employing modified CANDLE burnup with radial direction shuffling scheme

Abstract Design Study of Small Modular Gas-cooled Fast Reactors Employing Modified CANDLE Burnup with Radial Direction Shuffling Scheme has been performed with the power level 325–525 MWt. In this study Modified CANDLE burn-up scheme with radial direction shuffling has been employed with special attention to minimize reactivity swing during burn-up. The reactor cores are divided into 10 regions with equal volume in radial direction. The shuffling scheme of Modified CANDLE in radial direction can be described as follows. The natural uranium input is initially loaded in region 1. After 10 years of burnup the fuel in region 1 is shifter to region 2, the fuel in region 2 is shifted to region 3, etc. till the fuel of region 9 is shifter to region 10. The fuel from region 10 is taken out. Region 1–5 basically breeding zones in which plutonium is accumulated in fuels, while regions 5–10 have enough accumulated plutonium so that they contribute significantly to the power production. We call region 5–10 as burning zone. Nitride fuel is adopted as fuel in this study. Some parametric studies have been performed including variation of core height and power level. The neutronic calculations have been performed using the SRAC 2006 code with JENDL 4.0 nuclear data library. The optimized result shows the reactor could be operated 10 years continuously with maximum excess reactivity less than 1 % Δk/k for 500 MWt output power, 160 cm core active height and 110 cm core active radius.

Design study of 208Pb-Bi eutectic-cooled reactor with natural uranium as fuel cycle input with radial fuel shuffling

In the CANDLE burnup scheme, the burnup moves in the axial direction continuously. Meanwhile, the Modified CANDLE (MCANDLE) burnup scheme divides the core into several equal volume parts in the axial or radial direction. It can increase the utilization of natural uranium by using natural uranium as fuel cycle input. The use of 208Pb-Bi eutectic as a coolant can increase the criticality of the reactor. The core was divided into six discrete regions in radial directions. The refueling scheme was optimized to obtain an excellent reactor design. SRAC code system was used for neutronic calculations and JENDL 4.0 was used for the nuclear data library. A scheme that located natural uranium in the central region and nearby to the highest burnup level fuel has an excess reactivity lower than 0.5% Δk/k and PPF lower than two during operation time. The scheme also has a burnup of natural uranium spent fuel ∼ 48% FIMA.

Neutronics performances of gas-cooled fast reactor for 300-600 MWt Output Power with Modified CANDLE burn-up scheme in radial direction

Gas-Cooled Fast Reactor-GFR is a Generation IV reactor that is helium-cooled and has a closed fuel cycle. Due to the target operation on 2022-2030, this reactor type still needs further research and development technologies. We investigated the neutronics performances of a GFR balance type core with some modification of CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy production) burn-up scheme in the radial direction. The output power varied from 300 to 600 MWt. The neutronics calculation was performed using SRAC 2002 with JENDL 4.0 nuclear data library. The analysis indicate the reactor could operate critically for ten years without refueling with burn-up level 20% HM.

Neutronic Study of Fast Reactor with Modified CANDLE Burnup Scheme Using natural Pb, Pb(nat)-Bi Eutectic, 208Pb, and 208Pb-Bi Eutectic as Coolant

About 96% of reactors in the world consume enriched uranium. However, enrichment technology is costly and a sensitive issue related to nuclear non-proliferation. Whereas, without the technology, it is difficult to obtain the optimal benefits from the nuclear reactor. The long-life reactor designs that can consume natural uranium and minimize initial fue l loading are needed. Therefore, the design study of long-life Pb(208)-Bi eutectic cooled reactor with modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy Energy production) burn up scheme has performed. Modified CANDLE burnup scheme can use natural Uranium (without enrichment) as fuel and also can reprocess LWR (Light-Water Reactor) spent fuel. In Modified CANDLE scheme, a reactor core is divided into 10 regions in an axial direction which has the same volume. Region 1 is filled by fresh natural uranium and after 10 years burnup, it is then shifted to region 2. These mechanisms are applied to all the regions. Coolant for LFR (Lead-cooled Fast Reactors) have some requirements such as has low neutron absorption, low melting point, high boiling point and non-reactive with air and water. Pb(208)-Bi eutectic is a promising coolant for LFR due to its properties. The Neutronic calculation was performed by SRAC and FITB.ch1 using JENDL 4.0 as nuclear data library. The Important neutronic parameter such as k-eff is discussed in the present study. Initial k-eff of the reactor using Pb-natural, Pb-Bi, Pb(208), and Pb(208)-Bi as coolant are 0.99973, 1.0020, 1.0089, and 1.0059, respectively.

Neutronic analysis of sodium‐cooled fast reactor design with different fuel types using modified CANDLE shuffling strategy in a radial direction

This study compares three fuel types using neutronic analysis for use in a sodium-cooled fast reactor (SFR) design with a modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy production) radial shuffling strategy. SFR is one type of generation IV reactor that is currently under investigation for commercial implementation. In this study, the SFR design utilizes natural uranium as the fuel input. The designed reactor core has a two-dimensional cylindrical geometry for each fuel mixed oxide (MOX), uranium-plutonium nitride ([U-Pu]N), and uranium-plutonium zirconium ([U-Pu]Zr). A radial shuffling strategy, using natural uranium as the fuel input, is applied to the SFR to manage the nuclear fuel burn-up process of the long-life reactor. This strategy is called the modified CANDLE burn-up scheme. The reactor core is divided into 10 regions with equal volume to represent the 10 years that the reactor operates without refueling. Initially, the first (innermost) region of the reactor core is filled with natural uranium fuel. The result of the burn-up from the first region is then shuffled into the second region. The third region is the result of the burn-up that is shuffled from the second region, and so on. This mechanism only requires natural uranium as the input for each 10-year fuel cycle. In this study, the fuel movement scheme is examined for three fuels. Global neutronic parameters, such as the multiplication factors and burn-up analyses, are observed and optimized. Overall, for an output power of 500 MWth and an active core radius of 110 cm and height of 210 cm, the study indicates that (U-Pu)N is the optimal fuel to be applied in the SFR with a modified CANDLE burn-up scheme. (U-Pu)Zr reaches a critical condition at an output power of 500 MWth with an active core radius of 130 cm and a height of 210 cm; whereas criticality for MOX is achieved at an output power of 1500 MWth with an active core radius of 210 cm and a height of 210 cm.

Enhancing the performance of a long-life modified CANDLE fast reactor by using an enriched 208Pb as coolant

The investigation of the utilization of enriched 208Pb as a coolant to enhance the performance of a long-life fast reactor with a Modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy production) burnup scheme has performed. The analyzes were performed on a reactor with thermal power of 800 MegaWatt Thermal (MWTh) with a refueling process every 15 years. Uranium Nitride (enriched 15N), 208Pb, and High-Cr martensitic steel HT-9 were employed as fuel, coolant, and cladding materials, respectively. One of the Pb-nat isotopes, 208Pb, has the smallest neutron capture cross-section (0.23 mb) among other liquid metal coolants. Furthermore, the neutron-producing cross-section (n, 2n) of 208Pb is larger than sodium (Na). On the other hand, the inelastic scattering energy threshold of 208Pb is the highest among Na, natPb, and Bi. The small inelastic scattering cross-section of 208Pb can harden the neutron energy spectrum. Therefore, 208Pb is a better neutron multiplier than any other liquid metal coolant. The excess neutrons cause more production than consumption of 239Pu. Hence, it can reduce the initial fuel loading of the reactor. The selective photoreaction process was developing to obtain enriched 208Pb. The neutronic was calculated using SRAC and JENDL 4.0 as a nuclear data library. We obtained that the modified CANDLE reactor with enriched 208Pb as coolant and reflector has the highest k-eff among all reactors. Meanwhile, the natPb cooled reactor has the lowest k-eff. Thus, the utilization of the enriched 208Pb as the coolant can reduce reactor initial fuel loading. Moreover, the enriched 208Pb-cooled reactor has the smallest power peaking factor among all reactors. Therefore, the enriched 208Pb can enhance the performance of a long-life Modified CANDLE fast reactor.

Neutronic Analysis of Lead208-Bismuth Eutectic-Cooled Modified CANDLE Reactor with Core Geometry Variations

Lead208-Bismuth Eutectic (LBE)- cooled reactor is one of the Generation IV reactors. The fourth-generation has several objectives: economic competitiveness, inherent safety, minimize radioactive waste, and non-proliferation. Modified CANDLE burnup scheme is one solution to fulfil these objectives. The scheme does not need fuel enrichment and reprocessing Pu from LWR. Lead208-Bi eutectic was employed as a coolant of the reactor due to its low neutron absorption cross-section. However, However, it is necessary for surveying the neutronic core design. In this study, we compared the core neutronic among the variations of core geometry with equal volume of Pb208-Bi eutectic-cooled Modified CANDLE reactor. The calculation is performed by PIJ and CITATION of SRACs module. The Pancake cylindrical (larger diameter) has the highest K-eff and the lowest-peaking factor among of balance and tall cylindrical.

Study of Modified CANDLE Burnup Scheme In A Helium Cooled Fast Reactor Using Uranium-Plutonium Nitride

The startup strategies for neutronic analysis Gas-Cooled Fast Reactors with scheme Modified CANDLE have been investigated. This research used natural uranium and spent fuel PWR in the starter core. The reactor power level was set at case 800 MWth, 900 MWth, and 1000 MWth, while the fuel fraction was varied at 50%, 55%, 60%, and 65%. The calculation was performed by using SRAC-CITATION system codes, with two-dimensional R-Z cylindrical cell models. In this Modified CANDLE burnup scheme start-up strategy, the active core was divided into ten regions (region-1 until region-10) with similar volume in the axial direction and two regions in the radial direction. The fresh fuel of natural Uranium was initially put in region-1 while another was filled with a mixture of spent fuel PWR and natural Uranium. After each cycle of burnup, defined by 10 years, the fuel from region-1 was shifted to region-2, and the fuel from region-2 was shifted to region-3. This was done consecutively until all the regions have been refueling while region 1 is refilled with natural uranium fuel. An optimum design was achieved in the reactor by 60% inner and 65% outer fuel fraction for case 800 MWt. The ratios of a peak to average power density were 1.37, with power density of 187.43 W/cc.

Modified CANDLE Burnup Calculation System, Its Evolution, and Future Development

CANDLE Burn-up has been widely investigated during the last 15 years and give excellent possibility for natural Uranum utilization without the necessity of fuel enrchment plant and fuel reprocessing plant. Modified CANDLE burn-up scheme is a slight modification of CANDLE burn-up scheme by adopting discreet regions in the core. Modified CANDLE burn-up calculation is a complex calculations because it need accurate treatment of nuclear group constants, burn-up calculations, and multigroup diffusion calculations. Another problem come from the fact that the burn-up level of fuel is very high. Therefore the fission produc treatment have to be carried out in a highly accurate apporach and alsolarge number of energy groups is applied. Large number of Fission product is considered durng simulations. The calculations are performed under iterative scheme. For 10 regions and 10 years of burn-up period, first initial power density distributions are assumed and then multi-group diffusion and burn-up calculations are conducted. After 10 years of burn-up process the fuel in the first region is moved to the second region, the fuel in the second region was moved to the third region, the fuel in the third region is moved to the forth region, and so on. The fuel in the 10th region is then taken out. The first region is filled with the fresh fuel of natural uranium. The process is repeated till equilibrium condition achieved. Modified CANDLE burnup also has evolved to radial shuffling and combined axial-radial shuffling scheme.

Neutronic Comparison Study Between Pb(208)-Bi and Pb(208) as a Coolant In The Fast Reactor With Modified CANDLE Burn up Scheme.

Neutronic study of Pb(208)-Bismuth as a coolant in the Lead Fast Reactor (LFR) with Modified CANDLE burn up scheme has been conducted. Lead cooled fast reactor (LFR) is one of the fourth-generation reactor designs. The reactor is designed with 500 MW thermal power output. Modified CANDLE burn-up scheme allows the reactor to have long life operation by supplying only natural uranium as fuel cycle input. This scheme introducing discrete region, the fuel is initially put in region 1, after one cycle of 10 years of burn up it is shifted to region 2 and region 1 is filled with fresh natural uranium fuel. The reactor is designed for 100 years with 10 regions arranged axially. The neutronic calculations were performed by SRAC code using nuclear data library based on JENDL 4.0. Level burn up of Pb(208)-Bi cooled fast reactor is 530.688 GWD/MTU at BOC and 433.051 GWD/MTU at EOC whereas 190.790 GWD/MTU at BOC and 433.051 GWD/MTU at EOC for Pb(208) . The effective multiplication factor of Pb(208)-Bi Cooled Fast Reactor is 1.0554 at BOC and 1.05958 at EOC whereas 1.06703 at BOC and 1.06816 at EOC for Pb208.

Investigation of fuel cycles containing Generation IV reactors and VVER-1200 reactors

Abstract Gen-IV fast reactors are envisaged to operate in closed fuel cycles due to their ability to breed their fuel from fertile feed and burn minor actinides produced by themselves or thermal reactors in the nuclear park. The optimization of such fuel cycle strategies requires detailed models, capable of simulating the transition from initial state to equilibrium. A fast and flexible burn-up scheme based on polynomial fitting of the one-group cross-sections, FITXS was used to develop burn-up models for the Gen-IV Gas-cooled Fast Reactor (GFR), Lead-cooled Fast Reactor (LFR) and Sodium-cooled Fast Reactor (SFR), as well as a European Pressurized Reactor (EPR) and a VVER-1200 MOX fuel assembly. The burn-up models were integrated in a closed fuel cycle model containing Gen-IV LFR and MOX fueled VVER-1200 reactors, and different scenarios were investigated and compared concerning the reduction of transuranium inventories and the stabilization of the plutonium inventory. Results show that the LFR is capable of burning minor actinides from spent VVER-440 fuel and that transuranium inventories can be stabilized or reduced with a mixed fleet of LFR and MOX fueled VVER-1200 reactors.

Design Study of Small Modified CANDLE based Long Life Gas Cooled Fast Reactors

Small size modified CANDLE burn-up based Long Life Gas Cooled Fast Reactors have been investigated. In this study gas cooled fast reactor system are combined with modified CANDLE burn-up scheme to create long life fast reactors with natural circulation as fuel cycle input. Such system can utilize natural uranium resources efficiently without the necessity of fuel enrichment plant or fuel reprocessing plant. The investigated power level is in the range of 200-400 MWt. For small reactors, modified CANDLE burn-up design has difficulty in term of criticality aspect. Therefore some important steps are adopted to overcome this problem. First, combined axial-radial shuffling is adopted. Then, high fuel volume fraction of about 65% is adopted. The optimization processes is then conducted which includes adjustment of fuel region movement scheme, volume fraction adjustment, core dimension, etc. Due to the limitation of thermal hydraulic aspects, the maximum average power density of the proposed design is selected of about 75 W/cc. All proposed reactor design are operated for 10 years without refueling or fuel shuffling with just need natural uranium as fuel cycle input in every beginning of 10 years of cycle. With such conditions small sized cores from 200MWt to 400 MWt were investigated and optimized. The average discharge burn-up is about 20% HM. As an example, the dimension of 200 MWt case is 90 cm in radius and 180 cm height for the active core part. The reflector is 70 cm with. The burn-up level is about 20% HM.

FITXS: A fast and flexible burn-up scheme based on the fitting of one-group cross-sections

The closure of the nuclear fuel cycle is currently envisaged with the deployment of Generation IV fast reactors which are able to generate their fuel from fertile 238U or 232Th, and also burn minor actinides arising from legacy wastes and thermal reactors in the nuclear park. The optimization of such fuel cycle strategies requires detailed models, capable of simulating the transition from initial state to equilibrium. Due to the high computational cost of detailed burn-up calculations, most scenario codes use parametrized few group cross-sections to calculate fuel depletion in the reactors. This paper presents a fast and flexible burn-up scheme called FITXS which we applied on the GFR2400 Gas-cooled Fast Reactor and a European Pressurized Reactor MOX fuel assembly. Based on the fitting of one-group cross-sections as functions of the detailed fuel composition, the developed models are able to calculate spent fuel compositions with high accuracy for a wide range of initial compositions in less than one second computational time. In order to demonstrate applicability, the models were integrated into a fuel cycle model containing GFR2400 and European Pressurized Reactors, as well as conventional Light Water Reactors, and the fuel utilization and transmutational properties of the system were analyzed. It was found that the GFR2400 can operate in a closed fuel cycle, with positive breeding gain in the equilibrium. Increased minor actinide feed improves breeding in the GFR2400, but the accumulation of plutonium can be prevented by recycling the excess plutonium as MOX fuel in thermal reactors.

Safety Analysis of Pb-208 Cooled 800 MWt Modified CANDLE Reactors

Safely analysis of 800MWt Pb-208 cooled fast reactors with natural Uranium as fuel cycle input employing axial-radial combined Modiified CANDLE burnup scheme has been performed. The analysis of unprotected loss of flow(ULOF) and unprotected rod run-out transient overpower (UTOP) are discussed. Some simulations for 800 MWt Pb-208 cooled fast reactors has been performed and the results show that the reactor can anticipate complete pumping failure inherently by reducing power through reactivity feedback and remove the rest of heat through natural circulations. Compared to the Pb-nat cooled long life Fast Reactors, Pb-208 cooled reactors have smaller Doppler but higher coolant density reactivity coefficient. In the UTOP accident case the analysis has been performed against external reactivity up to 0.003dk/k. And for ULOHS case it is assumed that the secondary cooling system has broken. During all accident the cladding temperature is the most critical. Especially for the case of UTOP accident. In addition the steam generator design has also consider excess power which may reach 50% extra during severe UTOP case..

Preliminary design study of Long-life Gas Cooled Fast Reactor With Modified CANDLE Burnup Scheme

In this paper, preliminary design study of Gas Cooled Fas Reactors with Natural Uranium as Fuel Cycle Input has been performed. Gas Cooled Fast Reactor is slightly modified by employing modified CANDLE burnup scheme so that it can use Natural Uranium as fuel cycle input. The natural uranium is initially put in region 1, after one cycle of 10 years of burn-up it is shifted to region 2 and the region 1 is filled by fresh natural uranium fuel. This concept is basically applied to all regions. In this case the system has been applied to many power level which results relatively flexible discharge burn-up level up from about 20%HM to 30 %HM.

Design and Analysis on Initial Core for Pb‐Bı Cooled Fast Reactors using Modıfıed CANDLE Burn-up Approach

Nuclear reactor for power production which can directly consume natural Uranium has some advantages, e.g., no necessity to bult enrichment plant which may drive controversy such as in the case of Iran. CANDLE and Modified CANDLE type reactors are an example of Nuclear Power plant which can directly consume natural Uranium in its fuel cycle. In this study the preliminary analysis of start-up process of modified CANDLE burn-up scheme based long life Pb-Bi Cooled Fast Reactors has been performed. The basic strategy is to put different plutonium content in each core regions by considering its equilibrium plutonium content in each region. The system then is started as a Modified CANDLE reactor system until relatively stable cycle obtained. The calculation has been done by using SLAROM, SRAC, and FI-ITB CH1 system codes. Two dimensional multi-group diffusion and burn-up calculation has been adopted during simulation. As results, the start-up scheme of several Modified CANDLE core with power level of 1150-1350 MWt have been performed. In this case LWR plutonium is used to initiate the MCANDLE reactors. The simulation results show that the system can work well with maximum excess reactivity of 3% dk/k

Conceptual Design Study of Small 400 MWt Pb-Bi Cooled Modified Candle Burn-Up Based Long Life Fast Reactors

In this paper conceptual design study of modified CANDLE burn-up scheme based 400 MWt small long life Pb-Bi Cooled Fast Reactors with natural Uranium as Fuel Cycle Input has been performed. In this study the reactor cores are subdivided into 10 parts with equal volume in the axial directions. The natural uranium is initially put in region 1, after one cycle of 10 years of burn-up it is shifted to region 2 and the region 1 is filled by fresh natural uranium fuel. This concept is basically applied to all regions, i.e. shifted the core of I’th region into I+1 region after the end of 10 years burn-up cycle. For small reactor core, it is important to apply high breeding material, so that high volume fraction of 60% fuel volume fraction nitride fuel is applied. The effective multiplication factor initially at 1.005 but then continuously increases during 10 years of burn-up. The peak power density initially about 307 W/cc but then continuously decreases to 268 at the end of 10 years burn-up cycle. Infinite multiplication factor pattern change, conversion ratio pattern change, and Pu-239 accumulation pattern change shows strong acceleration of plutonium production in the first region which is located near the 10th region. Maximum discharged burn-up is 31.2% HM.

The Effects of the Total Number of Regions and Average Power Density on the Overall Performance of Modified CANDLE Burn-Up Scheme Based Gas Cooled Fast Reactors

In this study the effects of the total number of regions and average power density in Modified CANDLE burn-up scheme are studied. In the previous studies usually 10 equal axial regions are applied in Modified CANDLE burn-up scheme, and in this study 6, 8 and 10 regions Modified CANDLE burn-up scheme performance is compared and discussed. The core power level varied from 800-1000MWt. Several comparisons are performed between 10 and 8 regions Modified CANDLE, 8 and 6 regions Modified CANDLE and some additional comparison which include some changing in power level. Some general remark which we can get from this study is that reducing region with the same cycle length and power level will resulted in significant drop of effective multiplication constant especially at the beginning of life and the reduction of discharge burn-up level. On the other hand the increase of the power level with the same region number and cycle length resulted in higher effective multiplication constant value especially at the beginning of life, while at the end of life the differences are decrease. Then when we reduce the region number and increase the power level at the same time we get the mixed effect in which the system performance is relatively go back to the original case.