The influence of uncertainty in cross sections on the multiplication factor in a reflected reactor

2013 ◽  
Vol 54 ◽  
pp. 85-90 ◽  
Author(s):  
M.M.R. Williams
Keyword(s):  
Cross Sections ◽  
Multiplication Factor

scholarly journals Uncertainty Analysis of the TRU-Burning Thorium-Fueled RBWR Using Generalized Perturbation Theory

2017 ◽  
Author(s):  
Sandra Bogetic ◽  
Phillip Gorman ◽  
Manuele Aufiero ◽  
Massimiliano Fratoni ◽  
Ehud Greenspan ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Cross Sections ◽  
Consumption Rate ◽  
Hexagonal Lattice ◽  
Data Uncertainty ◽  
Monte Carlo Code ◽  
Multiplication Factor ◽  
Generalized Perturbation Theory ◽  
The Cross ◽  
The Impact

The RBWR-TR is a thorium-based reduced moderation BWR (RBWR) with a high transuranic (TRU) consumption rate. It is charged with LWR TRU and thorium, and it recycles all actinides an unlimited number of times while discharging only fission products and trace amounts of actinides through reprocessing losses. This design is a variant of the Hitachi RBWR-TB2, which arranges its fuel in a hexagonal lattice, axially segregates seed and blanket regions, and fits within an existing ABWR pressure vessel. The RBWR-TR eliminates the internal axial blanket, eliminates absorbers from the upper reflector, and uses thorium rather than depleted uranium as the fertile makeup fuel. This design has been previously shown to perform comparably to the RBWR-TB2 in terms of TRU consumption rate and burnup, while providing significantly larger margin against critical heat flux. This study examines the uncertainty in key neutronics parameters due to nuclear data uncertainty. As most of the fissions are induced by epithermal neutrons and since the reactor uses higher actinides as well as thorium and 233U, the cross sections have significantly more uncertainty than in typical LWRs. The sensitivity of the multiplication factor (keff) to the cross sections of many actinides is quantified using a modified version of Serpent 2.1.19 [1]. Serpent [2] is a Monte Carlo code which uses delta tracking to speed up the simulation of reactors; in this modified version, cross sections are artificially inflated to sample more collision, and collisions are rejected to preserve a “fair game.” The impact of these rejected collisions is then propagated to the multiplication factor using generalized perturbation theory [3]. Covariance matrices are retrieved for the ENDF/B-VII.1 library [4], and used to collapse the sensitivity vectors to an uncertainty on the multiplication factor. The simulation is repeated for several reactor configurations (for example, with a reduced flow rate, and with control rods inserted), and the difference in keff sensitivity is used to assess the uncertainty associated with the change (the uncertainty in the void feedback and the control rod worth). The uncertainty in the RBWR-TR is found to be dominated by the epithermal fission cross section for 233U in reference conditions, although when the spectrum hardens, the uncertainty in fast capture cross sections of 232Th becomes dominant.

An Analytical Solution for the Two-Group Diffusion Theory Analysis of Multiregion Source-Driven Systems

2019 ◽  
Vol 5 (3) ◽  
Author(s):  
Huseyin Atilla Ozgener ◽  
Ceyhun Yavuz
Keyword(s):  
Analytical Solution ◽  
Cross Sections ◽  
Diffusion Theory ◽  
Spherical Geometry ◽  
Multiplication Factor ◽  
Source Regions ◽  
Design Variables ◽  
Effective Multiplication Factor ◽  
Fast Flux ◽  
Effective Multiplication

An analytical solution of the two-group diffusion equations is derived for multiregion source-driven subcritical systems in spherical geometry. An analytical formulation for the calculation of the effective multiplication factor is also presented. Using typical two-group cross sections characterizing source, buffer, and blanket regions, parameters such as neutron amplification, source efficiency, and blanket fast flux peaking factor are calculated. The criticality solution is utilized to calculate the effective multiplication factor and the neutron source efficiency. The dependency of the calculated global parameters on design variables like the source, buffer, blanket thicknesses, and subcriticality level is studied. Thin source regions result in very high neutron amplification, at the expense of high blanket fast flux peaking factors. If a buffer region is put between the source and the blanket regions, flux peaking could be reduced at the expense of reduced neutron amplification. If the subcriticality level can be reduced without jeopardizing safety, the neutron amplification increases and the fast flux peaking is reduced.

Cross Sections Influence on Monte Carlo Based Burnup Codes

2014 ◽  
Author(s):  
Davide Chersola ◽  
Guglielmo Lomonaco ◽  
Guido Mazzini
Keyword(s):  
Monte Carlo ◽  
Cross Sections ◽  
Multiplication Factor ◽  
Effective Multiplication Factor ◽  
Effective Multiplication

This paper reports the results of a comparison among JEFF and ENDF/B datasets when used by SERPENT and MONTEBURNS codes on a GFR-like configuration. Particularly, it shows a comparison between the two Monte Carlo based codes, each one adopting three different cross sections dataset, namely JEFF-3.1, JEFF-3.1.2 and ENDF/B-VII.1. Calculations have been carried out on the Allegro reactor, i.e. an experimental GFR-like facility that should be built in EU as GFR demonstrator. Results concern nuclear parameters as effective multiplication factor and fluxes, as well as the atomic densities for some important nuclides versus burnup.

scholarly journals VOID COEFFICIENT SENSITIVITY ANALYSIS FOR THE TRIGA MARK II REACTOR AT L.E.N.A. (UNIPV)

2021 ◽  
Vol 247 ◽  
pp. 15005
Author(s):  
D. Portinari ◽  
A. Cammi ◽  
S. Lorenzi ◽  
M. Aufiero ◽  
Y. Calzavara ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Cross Sections ◽  
Research Reactor ◽  
Multiplication Factor ◽  
Delayed Neutron ◽  
Reactor Physics ◽  
Fission Spectrum ◽  
Challenging Tasks ◽  
Generalized Perturbation Theory ◽  
Triga Mark Ii

Sensitivity analysis studies the effect of a change in a given parameter to a response function of the system under investigation. In reactor physics, this usually translates into the study of how cross sections and fission spectrum modifications affect the value of the multiplication factor, the delayed neutron fraction or the void coefficient for example. Generalized Perturbation Theory provides a useful tool for the assessment of adjoint weighed functions such as keff and void coefficient sensitivities. In this work, the capability of SERPENT code to perform sensitivity calculation based on GPT is used to study the TRIGA Mark II research reactor installed at L.E.N.A. of University of Pavia. A general sensitivity analysis to the most important reactor’s cross sections has been performed in order to highlight the biggest reactivity contributions. Two numerically challenging tasks related to GPT calculation have been performed thanks to the relatively quick Monte Carlo approach allowed by this reactor: investigating the linearity of the reactivity injection caused by the flooding of the central channel, and calculating the fuel void coefficient sensitivity to the coolant density.

U233 Data Evaluation for Criticality Study

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Mohammad Alrwashdeh ◽  
Wang Kan
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Computer Code ◽  
Data Fitting ◽  
Multiplication Factor ◽  
Cross Section Data ◽  
Mathematical Methods ◽  
Bayes Method ◽  
Section Data ◽  
Experimental Data Fitting

The aim of this study is to investigate the available U233 cross section data for adequate calculation of critical benchmark experiments, to calculate the multiplication factor Keff for several benchmarks in both fast and thermal energy ranges. The evaluation of the U233 has been investigated using SAMMY code, in order to generate a useful database for criticality calculations; the computer code FITWR for experimental data fitting shows the same results obtained from the Bayes method included within the SAMMY code, with a slight difference in the results in the evaluated cross sections due to different mathematical methods having different results. Excellent results for the calculated Keff values are obtained for several benchmarks in the thermal and fast benchmarks considered in this study.

scholarly journals UNCERTAINTY EVALUATION IN CRITICALITY CALCULATIONS USING THE TSUNAMI METHODOLOGY

2018 ◽  
Vol 19 ◽  
pp. 30
Author(s):  
Matěj Šikl ◽  
František Havlůj
Keyword(s):  
Cross Sections ◽  
Uncertainty Evaluation ◽  
Multiplication Factor ◽  
Similarity Coefficients ◽  
Suggested Approach ◽  
Variable Parameters ◽  
Critical Results ◽  
Selection Of

Procedure of criticality calculations and uncertainty evaluations currently has several insufficiencies which could lead to potential non–conservativeness. Paper discuss and describes possibilities of elimination of these insufficiencies and thereby ensuring safely sub–critical results of calculations. Selection of experiments for validation based on similarity coefficients between systems acquired from TSUNAMI-IP is used for this purpose. TSUNAMI-IP operates with sensitivity of multiplication factor to cross sections of individual isotopes and reactions between compared systems. Moreover, TSUNAMI-IP determines uncertainty of calculations brought in using insufficiently similar experiments. Within research, effects of variable parameters used in calculations inputs are investigated. In conclusion optimized suggested approach for validations and uncertainty evaluation using TSUNAMI module from SCALE based on knowledge acquired within research is described.

scholarly journals QUANTIFICATION OF NUCLEAR DATA AND MANUFACTURING UNCERTAINTIES IN VERA

2021 ◽  
Vol 247 ◽  
pp. 15014
Author(s):  
Christopher Sedota ◽  
Scott Palmtag
Keyword(s):  
Standard Deviation ◽  
Cross Section ◽  
Cross Sections ◽  
Nuclear Data ◽  
Sampling Techniques ◽  
Multiplication Factor ◽  
Stochastic Sampling ◽  
Nuclear Data Library ◽  
Neutron Multiplication ◽  
Cross Section Uncertainty

Uncertainty quantification (UQ) was performed using the Consortium for the Advanced Simulation of Light Water Reactors (CASL) multiphysics core simulator VERA. Typically, only nuclear data cross sections are considered when trying to obtain uncertainty information in reactor simulation applications. In this paper, uncertainty in both nuclear cross section data and fuel manufacturing processes is analyzed using VERA. Uncertainties due to cross sections was determined by generating one thousand perturbed cross section libraries using the cross section covariance data provided in the evaluated nuclear data library. Uncertainty due to manufacturing was also determined using stochastic sampling and VERA. The use of similar stochastic sampling techniques for the same problems allows for the direct comparison of uncertainty stemming from the two sources of uncertainty. Sample size is considered due to the potentially large computational cost of stochastic sampling techniques, as is demonstrated in a full core depletion. It was found that for the Pressurized Water Reactor (PWR) pincell case at Hot Zero Power (HZP), the standard deviation in the neutron multiplication factor produced by material uncertainty was 101 pcm, while the standard deviation in the neutron multiplication factor produced by cross section uncertainty was 730 pcm. While the uncertainty in neutron multiplication factor due to cross section uncertainty is larger than uncertainty due to manufacturing uncertainties, neglecting manufacturing uncertainties may be an unacceptable oversight in certain high-precision simulation applications.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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