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Analiza občutljivosti referenčnih testnih primerov LMT-006 z OpenMC
No full textThe LEU-MET-THERM-006 (Low Enriched Uranium fissile material, METal physical form, THERMal spectrum, LMT-006 for short) series of experiments was carried out in 1969-1970 by the CEA (Commissariat á l\u27Energie Atomique), France in the experimental criticality facility of Valduc. The experiments are included in the ICSBEP (International Criticality Safety Benchmark Evaluation Project) handbook. The experiments consist of water-moderated and water-reflected metal tubes of low-enriched uranium (1.6%) arranged in arrays. A correlation of the reactivity with the fraction of epi-thermal fissions reveals a gradient wherein reactivity is higher for softer neutron spectra. This thesis models the LMT-006 benchmarks in OpenMC, verifies the results using the previously obtained MCNP6 results, and investigates the cause of the swing in reactivity through select sensitivity analysis and cross section perturbation.
Criticality benchmarks are a valuable resource for nuclear data and code validation. The obtained results of the LMT006 benchmark allows the validation of key cross sections with various nuclear data libraries. OpenMC, a free, open-source Monte Carlo neutron transport code, facilitates the sensitivity analysis and nuclear data validation with different libraries through its integrated Python API and NJOY interface. The results of this thesis contribute to the overall body of work of benchmark models, results, and nuclear data validation.Serija poskusov na skoraj-kritičnih sredicah LEU-MET-THERM-006 (Low Enriched Uranium fissile material, METal physical form, THERMal spectrum, LMT-006 na kratko) je bila v letih 1969-1970 izvedena na CEA (Commissariat á l’Energie Atomique), Francija v laboratoriju za eksperimentalno kritičnost Valduc. Poskusi so vključeni v priročnik ICSBEP (International Criticality Safety Benchmark Evaluation Project). Eksperimentalne sredice so sestavljene iz rešetke kovinskih cevi z nizko obogatenim uranom (1,6%), kjer se nevtroni s trki upočasnjujejo v vodi. Korelacija reaktivnosti z deležem epitermalnih fisij razkrije gradient, kjer je reaktivnost večja pri mehkejših nevtronskih spektrih. V magistrskem delu so podani rezultati modeliranja referenčnih testnih primerov LMT-006 z OpenMC, v primerjavi s predhodno pridobljenimi rezultat iz literature s programom MCNP6. Raziskani so možni vzroki za odstopanje reaktivnosti od referenčne vrednosti z analizo občutljivosti in s perturbacijami presekov za ključne jedrske reakcije. Merila kritičnosti so dragocen vir za validacijo jedrskih podatkov in programov. Dobljeni rezultati LMT006 omogočajo validacijo ključnih jedrskih presekov z različnimi knjižnicami jedrskih podatkov. OpencMC, brezplačen odprtokodni program za transport nevtronov z metodo Monte Carlo, olajša analizo občutljivosti in validacijo jedrskih podatkov z različnimi knjižnicami prek svojega integriranega API-ja Python in vmesnika za program NJOY za pripravo knjižnic presekov za OpenMC. Rezultati tega magistrskega dela prispevajo k celotnemu delu primerjalnih računskih modelov, rezultatov in validacije jedrskih podatkov
Validation and modification of fuel burnup with the use of ISOlib library in the CORD-2 program
Get PDFNa Inštitutu Jožef Stefan se računalniški paket CORD-2 uporablja za preračune sredice lahkovodnih reaktorjev. CORD-2 se uporablja že od leta 1990 in je bil že večkrat verificiran za izdelavo projektnih izračunov Nuklearne elektrarne Krško. V ta namen smo znotraj doktorskega dela razvili postopke, s katerimi smo zamenjali obstoječi WIMSD-5B transportni modul za celični izračun z Monte Carlo programom Serpent 2. Razvili smo postopek efektivne homogenizacijske metode (EDH) za izračun presekov na modelu osnovne celice, ki se trenutno uporablja v CORD-2 programskem paketu.
Z uporabo novega računskega orodja Serpent-GNOMER smo preverili izvedbo projektnih izračunov za Nuklearno elektrarno Krško. Izračune smo primerjali z eksperimentalnimi in vzporednimi CORD-2 preračuni, kjer smo opravili primerjavo ključnih parametrov. Rezultati analize so pokazali, da metoda Monte Carlo še ni primerna za rutinsko uporabo, lahko pa služi kot referenčna rešitev za preveritev determinističnih izračunov.
CORD-2 obravnava zgorevanje goriva z uporabo predhodno generirane knjižnice izotopske sestave, tako imenovano knjižnico ISOlib. Le ta je generirana v odvisnosti od povprečnih obratovalnih pogojev med zgorevanjem. V trenutni verziji programa CORD-2 ne moremo upoštevati efekta hlajenja med remontom. Zato smo izpeljali faktorje hlajenja s katerimi izboljšamo izotopsko sestavo goriva. Izpeljali smo splošno obliko faktorjev, ki so odvisni od časa hlajenja, obogatitve goriva in končne zgorelosti goriva. Z uporabo empiričnih popravkov na enostavnem konzervativnem modelu dosežemo, da se razlika zaradi efekta hlajenja zmanjša.At the Jožef Stefan Institute the CORD-2 simulator is used for core design calculations of PWR\u27s. The CORD-2 system has been validated for nuclear design calculations and has been used for the verification of the NPP Krško reload cores since 1990. New approach was developed where the existing WIMSD-5B code for lattice cell calculations was replaced with Monte Carlo code Serpent 2. The homogenization procedure was developed using the same methodology currently used in the CORD-2 system, namely the effective diffusion homogenization method (EDH), to obtain the cell homogenized cross sections and to use them in fuel assembly calculations.
In this work the reactor core analysis of the Krško NPP has been performed using newly developed core simulator Serpent-GNOMER. The comparison versus measurements and CORD-2 calculations for the key core parameters is performed. The results indicate that replacing the present transport solver with a Monte Carlo solver is (still) out of the question for routine calculations but it can be treated as a reference case for validating and fine-tuning of the deterministic computational scheme.
The treatment of burnup in CORD-2 is based on a predefined library of isotopic composition vectors called the ISOlib library. This library is constructed as a function of average fuel assembly operating conditions during burnup. Changes in the isotopic composition during outage were not accounted for in the original CORD-2 calculations. The cooling factor method was developed to improve the prediction of the isotopic composition. Derived cooling factors are in general form and they are dependent on cooling period, fuel enrichment and final burnup. We have demonstrated that derived corrections diminish the error in the calculated reactivity for a simple geometry model which represents the conservative approach
MODEL MONTE CARLO ZA DONOS NEVTRONOV PRI INTERAKCIJI NIZKO ENERGIJSKIH DEVTERONOV S TARČAMI V TRDNEM STANJU
Get PDFThe construction of the nuclear fusion plant \u27ITER\u27 has started in 2009 at Cadarache, France. The ITER machine represents a milestone in the civil use of the nuclear fusion energy. The physics of ITER is based on the fusion reaction between deuteron and triton nuclei (d-t). The deuteron-deuteron reaction (d-d) is also interesting and is foreseen for the next generation of fusion reactors. The experimental activities carried out in the context of the ITER neutronics involve intense fields of neutrons produced with a linear accelerator for deuterons, a target containing tritium or deuterium and auxiliary structures, such as the detector system, cooling system, room walls, etc. Experimental data have been obtained from the FNG (Frascati Neutron Generator, Italy), FNS (Fast Neutron Source, Japan), OKTAVIAN (Osaka University, Japan) and IRMM (Institute for Reference Materials and Measurements, EU). An independent method was developed at FNG for the simulation of the d-t neutron spectra at different angles. The FNG source routine models the Monte Carlo deuteron transport in solid tritiated targets as done in the well known SRIM code. The neutrons are generated according to the tabulated probability of the d-t reactions as for the DROSG2000 code. The FNG source routine is implemented into the MCNP distributions. The user is asked to define into the MCNP input file the deuteron energy (up to 10 MeV), the beam width and the target dimensions and composition. This source routine has been chosen as starter for the present thesis. Improvements and extensions were introduced.
- The methodology, originally developed for the d-t neutron source, has been extended to d-d neutron sources.
- Assuming the the SRIM code constitutes the reference calculation for the deuteron transport in matter, its implementation in the source routine has been cross-checked by extracting from the latter the same quantities as provided by the original code.
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- In the present version of the source routines, the cross sections are internally generated from built in table based on modern evaluated nuclear data files instead of tables obtained from the DROSG200 code.
- Since the model may be used up to 10 MeV deuteron energy, the relativistic kinematics has been implemented to avoid unnecessary approximations.
- Simulations of the bare neutron source spectra and angular yields measurements have been carried out to validate the model.
- New editions of the d-t and d-d source routine have been released for the latest versions of the MCNP codes and tested on LINUX and WINDOWS machines. The validation activities with the FNG and IRMM experimental data suggested a possible application of the source routine for the characterisation of neutron spectrometers in the MeV energy region.
The source routine has been adopted to simulate integral benchmark experiments at FNG, FNS and OKTAVIAN. Brand new MCNP benchmark models have been developed for inclusion of all the available experimental information. It is shown that the d-t source routine is an accurate tool for the generation of the source eutrons. It also demonstrates to be useful for the evaluation of the neutron source term and associated uncertainties. The accuracy of the analyses is pursued to the point that the quality of the nuclear data employed in the simulation can be assessed. To this extent, the case of a new evaluation of the neutron interaction nuclear data for Manganese-55 is tested. A set of integral benchmark experiments has been used in the validation phase of the nuclear data. The computational models rely on the source routine, the object of the thesis. In conclusion, the source routine claims the inclusion of the major features responsible for the experimental resolution associated with the source term. The doctoral thesis explores its usage in the context of the experimental activities for ITER. The future exploitation of the source routine for the simulation of worldwide experiments might become an occasion to compare it with the source models available in the other laboratoriesGradnja fuzijske elektrarne ITER se je pričela leta 2009 v Cadarachu v Franciji. ITER predstavlja mejnik v rabi fuzijske energije. Reaktor ITER bo deloval na osnovi zlitja jeder devterija in tritija (D-T). Naslednja generacija fuzijskih reaktorjev bo predvidoma delovala na osnovi reakcije zlitja dveh jeder devterija (D-D).
Problem modeliranja medsebojnega vpliva devterona v tritijevih in devterijevih tarčah predstavlja zanimiv primer uporabne fizikalnih modelov in jedrskih podatkov. Problem zahteva natančno obravnavo elastičnega sipanja (fizikalni modeli), neelastičnih elektronskih trkov (običajno so podani v obliki tabel) in fuzijskih jedrskih podatkov (kateri podatki so na voljo in kateri evalvirani podatki naj se uporabijo). Namen doktorskega dela je, da pokaže, da se lahko razvije take računske modele, ki imajo trdno fizikalno osnovo in so numerično stabilni pri opisu podatkov iz nevtronskega fuzijskega eksperimenta.
Izdelan podprogram, ki je rezultat tega doktorskega dela, vsebuje vse glavne elemente mehanizmov, ki določajo izvorni člen. Neposredno so ovrednotene anizotropnost D-T in D-D fuzijskih reakcij, upočasnjevanje devteronov v trdnih tarčah ter geometrija in sestava tarč. V doktorskem delu je opisana njegova raba v kontekstu eksperimentalnih aktivnosti za ITER. V okviru tega je bil opravljen razvoj MCNP modelov za analizo integralnih referenčnih eksperimentov FNG, FNS in OKTAVIAN. Bodoča uporaba podprograma za izvor bi lahko obsegala simulacije eksperimentov v različnih laboratorijih po svetu in primerjavo z njihovimi lastnimi modeli izračunov izvornega člena
Analiza metode vstavitve za meritev reaktivnosti kontrolnih palic
Get PDFThe rod insertion method presents an efficient way of measuring the reactivity worth of control rods in a nuclear reactor. This is an inherently dynamic method, which is why we highlighted the differences between the static and the dynamic reactivity. Direct comparison of results based on the static and the dynamic reactivity relies heavily on adequate time-resolved three-dimensional numerical simulation. In the present work, this is achieved by updating the Gnomer computer program to support such calculation and verifying it on representative test cases. In the following, improvements of the rod insertion method are based on experimental data from the Krško nuclear power plant. Due to the results of the analysis, some of the methodological assumptions are retained (e.g. continuous insertion), while others are ameliorated (e.g. flux redistribution correction). A new correction is added, namely the reactivity overshoot compensation. It takes into account the dynamic effects after the control rod has reached its fully inserted state, and as such increases the total rod worth measurement consistency. Lastly, conversion from dynamic to static reactivity worth is established by following the examples in the literature and by using kinetic simulation. Thus – with the updated methodology – the rod insertion method is proven to yield excellent results in comparison to the well-established boron dilution method, and can be used as replacement.Metoda vstavitve predstavlja učinkovit način za merjenje vrednosti reaktivnosti kontrolnih palic v jedrskem reaktorju. To je v svojem bistvu dinamična metoda, zato osvetljujemo razlike med dinamično in statično reaktivnostjo. Direktna primerjava rezultatov na osnovi statične in dinamične reaktivnosti je močno oprta na ustrezno časovno odvisno numerično simulacijo v tridimenzionalni geometriji. Slednja je v pričujočem delu izvedena prek namenske posodobitve računalniškega programa Gnomer, njegove nove kinetične zmogljivosti pa so preverjene na reprezentativnih testnih primerih. V nadaljevanju so izboljšave metode vstavitve osnovane na podlagi eksperimentalnih podatkov iz Nuklearne elektrarne Krško. Analiza je pokazala, da je nekaj predpostavk moč ohraniti v metodologiji (npr. enakomerno vstavljanje), pri drugih pa so smiselne izboljšave (npr. izboljšan popravek redistribucije fluksa). Dodan je tudi povsem nov popravek, in sicer kompenzacija prenihaja reaktivnosti. Ta z upoštevanjem dinamičnih učinkov potem, ko je kontrolna palica dosegla maksimalno vstavljenost, pripomore k bolj konsistentni meritvi njene celotne vrednosti reaktivnosti. Nazadnje je na podlagi zgledov iz literature prek kinetičnih izračunov vpeljana tudi pretvorba iz statične v dinamično vrednost reaktivnosti. S tako posodobljeno metodologijo daje metoda vstavitve odlične rezultate, povsem primerljive s splošno uveljavljeno metodo redčenja borove kisline, kateri lahko služi za zamenjavo
Razvoj inkrementalne metodologije za sledenje od zgorevanja odvisnih izotopskih vektorjev gorivnih elementov v programu TRIGLAV za raziskovalne reaktorje
No full textAn incremental methodology has been developed to consider the isotopic changes of the fuel elements during their burnup process in the TRIGLAV code. Through the modification of the internal subroutines and the implementation of new and auxiliary programs, the incremental scheme tracks the exact isotopic concentrations of the pin-cells (fuel elements) as they undergo the depletion cycle by saving the specific material compositions of the unit-cells at every intermediate burnup step in master isotopic libraries. These updated libraries, carrying the isotopic vectors of the fuel as a function of burnup, serve as input data in the subsequent cross-section homogenization before undergoing the global diffusion calculation. The resulting burnup and isotopic distributions from this new methodology were compared with the data from the original -integral- scheme and from Serpent simulations through their relative differences. In every case the root-mean-squared deviations are less than 1%, so the model remains validated. Highest discrepancies arise from the TRIGLAV\u27s treatment of the unit-cells that represent partially inserted Control Rods. The analysis showed that the resulting burnup levels for the individual pin-cells are mismatching because in the incremental scheme the cross-section homogenization is following more closely the number density changes of the unit-cells at each intermediate step of the depletion cycle, hence impacting their specific burnup increments (dBU). It has also been noted that the individual isotope densities for particular pin-cells have increasing differences when compared (up to 5%) depending on their position inside the core, and thus on their burnup process. Overall, the study explored the physical effects of the isotopic changes in a research reactor and the significance of tracking the burnup-dependent isotopic concentrations of the fuel elements.Razvita je bila inkrementalna metodologija za sledenje izotopskim spremembam gorivnih elementov med njihovim procesom zgorevanja v programu TRIGLAV. S spremembo notranjih podprogramov in uvedbo novih ter pomožnih programov inkrementalna shema natančno sledi izotopskim koncentracijam gorivnih elementov (osnovne-celice) med ciklom zgorevanja goriva, pri čemer shranjuje specifično materialno sestavo osnovnih celic na vsakem vmesnem koraku zgorevanja v master izotopsko knjižnico. Te posodobljene knjižnice, ki vsebujejo izotopske vektorje goriva kot funkcijo zgorevanja, se uporabijo kot vhodni podatki pri nadaljnji homogenizaciji reakcijskih jedrskih presekov, preden se izvede globalni difuzijski izračun. Rezultati zgorevanja in izotopske porazdelitve iz te nove metodologije so bili primerjani s podatki iz izvirne integralne sheme ter s simulacijami s programom Serpent iz literature in z izračunom relativnih razlik. V vseh primerih so kvadratna povprečna odstopanja (RMS) manjša od 1%, kar potrjuje veljavnost modela. Največja odstopanja so povezana z obravnavo osnovnih celic, ki predstavljajo delno vstavljene kontrolne palice. Analiza je pokazala, da se dosežene ravni zgorevanja posameznih gorivnih elementov razlikujejo, ker inkrementalna shema bolj natančno sledi spremembam numerične gostote osnovnih celic na vsakem vmesnem koraku zgorevanja goriva, kar posledično vpliva na njihove specifične inkremente zgorevanja (dBU). Prav tako je bilo ugotovljeno, da imajo posamezne izotopske gostote pri določenih gorivnih elementih večje razlike (do 5%), odvisno od njihovega položaja v sredici reaktorja in s tem njihovega procesa zgorevanja. Na splošno je študija raziskala fizikalne učinke izotopskih sprememb v raziskovalnem reaktorju ter pomen sledenja izotopsko odvisnim koncentracijam gorivnih elementov med zgorevanjem
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mechanical properties and microstructural characterizations of potassium doped tungsten
No full textTungsten is a very promising candidate material for plasma facing components in fusion reactor due to its high melting temperature, high thermal conductivity, low tritium inventory and low erosion rate under plasma loading [1]. The main drawbacks are its poor mechanical properties. None of the W & W alloys developed so-far has been fully optimized for structure or armour application in fusion reactors. Nor have reference tungsten grades been fully characterized [2]. The tensile properties of tungsten in the vicinity of room temperature, the ductile-brittle transition must be considered because of its effect on yield strength and other mechanical behaviors. The potassium doped tungsten grade WVWM (as received and annealed at 1600°C) produced by Plansee AG could be a potential plasma facing material for future nuclear fusion facilities and reactors such as ITER and especially DEMO. For a better understanding of both recrystallization and ductile to brittle transition temperature, tensile tests are performed on potassium doped tungsten, WVWM, up to 2000°C at different loading rates (0.2 and 42 mm/min). The mechanical properties are highly dependent on the microstructure. The etched sample surface and fracture surface after tensile testing are microstructurally assessed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). All the obtained data will be summarized into a database that can be used for future modelling input and will be compared to the same grade material after neutron irradiation
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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