Integral Burnable Absorber Research Articles

Searching for optimal reactivity management using a new burnable absorber for SCLWR with (Th, 233U)O2

This work investigates the efficiency of some new burnable absorbers (BAs) suggested to provide possible improvements in the fuel management of a supercritical light water reactor (SCLWR) assembly fueled with (Th, 233U)O2. Four BAs including gadolinium, Erbium, Iridium and Lutetium are suggested as integral burnable absorber (IBA) rods. A three-dimensional model of SCLWR has been modelled using MCNPX version 2.7. A complete neutronic analysis has been carried out for the suggested BAs and compared with the gadolinium vector which is the common BAs. The IBA rods were distributed through the SCWR fuel assembly in a way that provided a flat power distribution. Various concentrations of the suggested BAs have been investigated to obtain the optimum value that can suppress the excess reactivity at the beginning of the cycle and flatten the infinite multiplication factor. The burnup parameters including the fertile, fissile, BAs and most effective fission product concentration as a function of effective full power days (EFPDs) of the SCLWR have been examined for the suggested BAs. The reactivity temperature coefficients have been studied to ensure the viability of the suggested BAs. A further analysis is performed to study the axial, radial power distribution and local power peaking factor.

Searching for optimum design and burnable absorber for controlling the reactivity of U.S. Supper critical water reactor (SCWR)

Numerous research endeavours are currently underway to advance supercritical water reactors (SCWR), acknowledged as a cornerstone among Generation IV nuclear reactor designs. Evaluation and managing the reactivity of the reactor is a vital issue in the reactor operation. This research seeks to identify efficacious burnable absorber (BA) materials and determine an optimal spatial distribution within the fuel assembly to regulate reactivity levels effectively. Gadolinium, erbium and Lutetium have been suggested as BA in the form of integral burnable absorber (IBA) rods ((UO2 + Gd2O3), (UO2 + Er2O3) and (UO2 + Lu2O3)). Two SCWR assembly models, each featuring varied quantities and distributions of BA, have been examined. Various concentrations of the suggested BAs have been examined in the suggested models to verify the optimum cases. Burnup analyses have been conducted to evaluate the proposed cases. Different alloys of BAs including B4C+Dy2O3 and B4C+Sm2O3 have been investigated in the control rod and compared with the standard alloy B4C.

UN-UB[formula omitted] Composite fuel material; improved water tolerance with integral burnable absorber

As part of a scoping study to investigate the initial feasibility of UN-UB2 composites, pellets of 5, 25 and 50% UB2 within UN were produced via Spark Plasma Sintering alongside a high density UN material. The pellets were seen to have a well-formed and dense microstructure which did not appear to change after annealing for 24 hours at 1273 K, which consisted of UN, UB2 and a UBN phase, with an additional UB0.1N0.9 phase suggested via EBSD. Steam exposure in an STA demonstrated that an increase in reaction onset temperature of approximately 150 K can be achieved via the addition of 25% UB2, and an increase of 120 K in onset temperature was evident in pellets containing only 5% UB2. High density UN was tested alongside these composites and behaved similarly, but microstructural examination of composites post-oxidation suggest that the oxidation rate is retarded in porous regions in addition to highly dense regions.

Neutronic analysis of VVER-1000 MOX fuel assembly with burnable absorber Gadolinia and Erbia

This paper represents the neutronic characteristics and feasibility of using Gadolinia and Erbia in integral burnable absorber (IBA) rods for the proposed MOX fuel assembly of VVER-1000 reactor by Nuclear Energy Agency (NEA). For comparison the 4.0% Gd2O3 IBA is considered as a reference. The assembly was burned to 40 GWd/t, and by neutronic calculation, the optimum percentage of Gd2O3 and Er2O3 was determined using SRAC-2006 code and JEFF-3.1 data library. The burnup dependent reactivity of a MOX assembly containing 12 UO2-Gd2O3-Er2O3 (U-Gd-Er) IBA rods with 0.9% Gd2O3, and 5.0% Er2O3 was found almost identical to the reference assembly with 4.0% Gd2O3 in IBA rods. However, the assembly with U-Gd-Er IBA rods has a flatter pin-wise power distribution and lower power peaking factor (PPF). Long-lived fission products, poisons, and minor actinides are also investigated for choosing Gd2O3 and Er2O3 as IBA over only Gd2O3 for the VVER-1000 MOX fuel assembly.

Use of americium as a burnable absorber for VVER-1200 reactor

The objective of this research is to the use of americium (AmO2) as a burnable absorber effectively instead of conventional gadolinium (Gd2O3) for VVER-1200 reactor by analyzing its impacts on reactivity, power peaking factor (PPF), safety factor, and quality of the spent fuel. The assembly is burned to 60 GWd/t by using SRAC-2006 code and JENDL-4.0 data library for finding the optimum amount and effective way of using AmO2 as a burnable absorber. From these studies, it is found that AmO2 can decrease the excess reactivity like Gd2O3 without changing the criticality life span and enrichment of 235U. A homogeneous mixture of the 0.20% AmO2+ 4.95% enriched UO2 fuel rod (model MF-4) decreases the PPF than the reference assembly. The use of AmO2+UO2 in the integral burnable absorber (IBA) rod or the outer layer could also decrease the PPF up to 10 GWd/t but increases rapidly after 30 GWd/t, which could be a safety threat. The fuel temperature coefficient and void coefficient of the model MF-4 are the same as the reference assembly. In addition, 22% of initially loaded Am are burning effectively and contributing to the power production.

SMART reactor core design optimization based on FCM fuel

Fully ceramic microencapsulated (FCM) fuel is originally proposed for replacement in light water reactors (LWRs) to enhance thermal hydraulic performance and reactor safety features. However, reactor core cycle length might be degraded by the fuel replacement. In the present paper, SMART reactor core, which employs conventional UO2 fuel in its original scheme, is redesigned based on FCM fuel. Reactor core configuration is optimized for extending the reactor core cycle length. Optimization is performed using imperialist competitive algorithm (ICA) in two steps. In the first step, multi-zone core configurations are investigated with the purpose of increasing effective multiplication factor. In the second step, utilizing integral burnable absorber (IBA) rods are evaluated with the object of power peaking factor reduction and flattening reactor power distribution. Finally, the ultimate target of the present study is achieved and core configuration with four zones is proposed that has potential of increasing reactor cycle time for 46 days with appropriate safe margin of power peaking factor.

Study of neutronic characteristics for the VVER reactor assembly with five various burnable poisons using MCNPX code

The present work investigates the neutronic characteristics of VVER reactor assembly with various burnable poisons. The MCNPX code is used to design VVER-1000 LEU Assembly model. At first gadolinium oxide (Gd2O3) as integral burnable absorber is used, the results are compared with the results of the reference benchmark. Different fuels (uranium oxide, thorium oxide and thorium plutonium oxide) and five various burnable poisons are used in the study. Gadolinium Oxide (Gd2O3) and Erbium Oxide (Er2O3) are used together in the same assembly as IBAs that are mixed homogenously with 30 uranium fuel rods and Dysprosium Titanite (Dy2O3–TiO2) is coated the fuel rod with 0.001 cm thickness. Also, Iridium Oxide (IrO2) used in guide tube as BPR and finally Minor Actinides are used as both IBAs or BPRs. A number of parameters are determined at BOL such as thermal neutron flux, axial power distribution and pin power distribution. Also, four physical parameters are studied, Keff, βeff, MTC and FTC. The burnup calculation is performed for VVER-1200. The comparison of the multiplication factor variation with depletion (for 730 days) illustrated that Iridium Oxide in Th–F assembly has a faster rate of depletion than other Burnable absorbers. Using Iridium Oxide shortens the core life time due to the transformation process of Ir-191 to Ir-192. Moreover, the concentration of actinides for the different assemblies at EOC were discussed. In addition, the effect of using BPs in different fuel assemblies on the concentration of 135Xe and 149Sm production are also performed.

Searching for the optimum number of integral burnable absorber rods used in PWR assembly

This article discusses the effect of different Integral Burnable Absorber numbers (IBAs) on the neutronic characteristics of a Pressurised Water Reactor (PWR) to provide a suitable safety level. MCNPX code version 2.6 was used to design a three dimensional model for PWR assembly. The designed model has been validated by comparing the output values of the infinity multiplication factor (Kinf) with a previously published value. The designed MCNPX model was used to analyse the radial distribution of thermal neutrons and the power through PWR assembly with and without IBA. Due to the high absorption cross-section of gadolinium, it has been used as a burnable absorber material in the IBA rods. The gadolinium isotopes suppressed the power in the regions where they were distributed. The existence of IBA rods has a large effect on the Kinf. This effect decreases gradually with burnup due to the degradation of gadolinium. The gadolinium isotopes degradation was analysed with burnup. Different numbers of IBA rods were investigated to optimise the suitable number that can be used in the PWR assembly. The reactivity has been investigated at different numbers of IBAs. The gadolinium effect on the concentration of 135Xe and 149Sm resulting from the fission process was analysed.

Simulate the effect of integral burnable absorber on the neutronic characteristics of a PWR assembly

This article examines the effect of an integral burnable absorber (IBA) on the neutronic characteristics of Pressurized Water Reactor (PWR) to provide possible improvements for the fuel management. MCNPX code was used to design a three dimensional model for PWR assembly. The designed model has been validated by comparing the output data with a previously published data. MCNPX code was used to analyze the radial thermal neutron flux and the radial power distribution through PWR assembly with and without IBA. Gadolinium is burnable absorber material that was used in the IBA rods. The gadolinium element suppressed the power in the regions where they were distributed. The existence of IBA rods has a large effect on the Kinf. This effect decreases gradually with burnup due to the degradation of gadolinium. The gadolinium isotopes degradation was analyzed with burnup. Different numbers of IBA rods were investigated to optimize the suitable number that can be used in the PWR assembly. The gadolinium effect on the concentration of 135Xe and 149Sm resulting from the fission process was analyzed.

Impact of integral burnable absorbers on SMART reactor behaviour under normal and anomalous operational conditions

Burnable poisons are used to safely prolong reactor core cycle time. They are effective alternatives to regulate power peaking factor and to reduce soluble boron concentration. One of common materials employed for this purpose is Gd2O3 dispersed homogenously in UO2 fuel material. The amount of Gd2O3 content impacts directly on thermophysical properties of integral burnable absorber rods. Therefore, especial care must be taken at the design stage of the reactor core. In this paper, the effects of various Gd2O3 contents, as a burnable poison, on neutronic and thermal hydraulic behaviour of a SMART reactor are investigated. MCNPX 2.6 code is used to perform neutronic simulations of the core. The COBRA-EN with modified MATPRO subroutine is employed for calculating integral burnable absorber rods temperature in normal operation and control rod withdrawal accident. Results show that 12 percent of weight fraction for Gd2O3 lead to the suitable neutronic design which does not break the thermal hydraulic and safety constraints. The performance of the core design is evaluated in steady state and transient conditions in details in the paper.

Gas releases and rod internal pressure of BN-added UO2 fuel

Gadolinium (Gd), in the form of gadolinia (Gd2O3), has been used as integral burnable absorber to UO2 fuel by different companies. Recently, alternative burnable absorber materials are under investigation. In this paper, the results of the study on the use of boron mixed in UO2 as an integral burnable absorber are presented. Boron nitride was selected as the form of B to be added to UO2 fuel based on the stability of B during sintering. Fuel performance analysis code FRAPCON-UNI, which is based on FRAPCON code and has the modifications for boron and helium generation and gasses release models, was used for the calculation of fuel performance. Helium generation was calculated using a model and the result was verified against ORIGEN calculation results. Gas release calculation was based on Forsberg Massih model and different characteristics of the gasses were considered. Power histories of maximum burnup rods (B rod, no B rod, and Gd rod) were selected from reactor physics data. The results indicated significant increases in rod internal pressure by 500 ppm boron addition at the end of life with minimum influence of a grain boundary boron fraction due to high diffusivity of helium and nitrogen.