Analisi di un Incidente Non Mitigato di Tipo LOCA in un Reattore PWR Mediante il Codice MELCOR 2.1

La presente attività di tesi è stata svolta presso la Divisione di Sicurezza Nucleare dell’ENEA di Bologna ed è stata finalizzata ad analizzare, mediante il codice MELCOR 2.1, le conseguenze di tre incidenti severi non mitigati di tipo LBLOCA in un generico reattore nucleare ad acqua leggera pressurizzata (PWR) da 900 MWe. In particolare sono stati confrontati gli scenari incidentali relativi a tre distinti eventi iniziatori nel circuito di refrigerazione primario: la rottura a ghigliottina della gamba fredda (CL) del loop 1, della gamba calda (HL) del loop 1 e della surge line di connessione con il pressurizzatore. Le analisi MELCOR hanno indagato la progressione incidentale in-vessel, con particolare riferimento alle fenomenologie termoidrauliche e di degradazione del core. MELCOR infatti è un codice integrato che simula le principali fenomenologie riguardanti sequenze incidentali di tipo severo in reattori ad acqua leggera. Durante la prima fase dei tre transitori incidentali risultano predominanti fenomenologie di carattere termoidraulico. In particolare MELCOR predice la rapida depressurizzazione e il conseguente svuotamento del sistema di refrigerazione primario. I tre transitori sono poi caratterizzati dallo scoprimento completo del core a causa dell’indisponibilità del sistema di refrigerazione di emergenza. Il conseguente riscaldamento del core per il calore di decadimento e per ossidazione delle strutture metalliche conduce inevitabilmente alla sua degradazione e quindi al fallimento della lower head del recipiente in pressione del reattore nei tre scenari incidentali in tempi diversi. Durante la prima fase incidentale, di carattere prevalentemente termoidraulico, sono state rilevate le principali differenze fenomenologiche causate dalle differenti posizioni e dimensioni delle rotture. Il transitorio causato dalla rottura della CL si è confermato come il più gravoso, con fallimento anticipato della lower head rispetto agli altri due transitori considerati.

Vakavat reaktorionnettomuudet ja niiden mallintaminen Olkiluoto 1 ja Olkiluoto 2 laitosyksiköille MELCOR-ohjelman versiolla 2.1

Vakaviin reaktorionnettomuuksiin liittyviä ilmiöitä on tutkittu jo 1980-luvulta lähtien ja tutkitaan edelleen. Ilmiöt liittyvät reaktorisydämen ja muiden paineastian sisäisten materi-aalien sulamiseen sekä reagointiin veden ja höyryn kanssa. Ilmiöt on myös tärkeää tuntea ja niiden esiintymistä mallintaa käytössä olevilla laitoksilla, jotta voidaan varmistua turval-lisuusjärjestelmien riittävyydestä. Olkiluoto 1 ja 2 laitosten käyttölupa uusitaan vuoteen 2018 mennessä. Lupaprosessiin liit-tyy analyysejä, joissa mallinnetaan laitosten toimintaa vakavassa reaktorionnettomuudessa. Näiden analyysien tekoon Teollisuuden Voima Oyj on käyttänyt ohjelmaa nimeltä MEL-COR jo vuodesta 1994 lähtien. Käytössä on ollut useita eri ohjelmaversioita ja viimeisin niistä on 1.8.6, joka riittää vielä tulevan käyttöluvan uusintaprojektiin liittyvien analyysien tekoon. MELCOR:n vanhaa 1.8.6 ohjelmaversioita ei kuitenkaan enää päivitetä, joten siirtyminen uudempaan 2.1 versioon on tulevaisuudessa välttämätöntä. Uusimman versiopäivityksen yhteydessä on kuitenkin muuttunut koko ohjelman lähdekoodi ja vanhojen laitosmallien käyttö uudessa ohjelmaversiossa vaatii tiedostojen konvertoinnin. Tässä työssä esitellään MELCOR-version 2.1 ominaisuuksia ja selvitetään, mitä 1.8.6 versioon luotujen laitosmal-lien käyttöönotto versiossa 2.1 vaatii. Vaatimusten määrittelemiseksi laitosmalleilla tehdään ajoja molemmilla ohjelmaversioilla ja erilaisilla onnettomuuden alkutapahtuman määrittelyillä. Tulosten perusteella arvioidaan ohjelmaversioiden eroja ja pohditaan mitä puutteita laitosmalleihin konversion jälkeen jää. Näiden perusteella arvioidaan mitä jatkotoimenpiteitä konversio vaatii.

Slavnov-Taylor identities for the 2+1 dimensional noncommutative CPN-1 model

In the context of the 1/N expansion, the validity of the Slavnov-Taylor identity relating three- and two-point functions for the 2 + 1-dimensional noncommutative CP(N-1) model is investigated, up to subleading 1/N order, in the Landau gauge.

Dynamical generation of mass in the D = (2+1) Wess-Zumino model

In this work we study the dynamical generation of mass in the massless N = 1 Wess-Zumino model in a three-dimensional spacetime. Using the tadpole method to compute the effective potential, we observe that supersymmetry is dynamically broken together with the discrete symmetry A(x) -> A(x). We show that this model, different from nonsupersymmetric scalar models, exhibits a consistent perturbative dynamical generation of mass after two-loop corrections to the effective potential.

3-Nitrophenol-4,4 '-bipyridyl N,N '-dioxide (2/1): a DFT study and CSD analysis of DPNO molecular complexes

The title 2:1 complex of 3-nitrophenol (MNP) and 4,4'-bipyridyl N, N'-dioxide (DPNO), 2C(6)H(5)NO(3)center dot C(10)H(8)N(2)O(2) or 2MNP center dot DPNO, crystallizes as a centrosymmetric three-component adduct with a dihedral angle of 59.40 (8)degrees between the planes of the benzene rings of MNP and DPNO (the DPNO moiety lies across a crystallographic inversion centre located at the mid-point of the C-C bond linking its aromatic rings). The complex owes its formation to O-H center dot center dot center dot O hydrogen bonds [O center dot center dot center dot O = 2.605 (3) angstrom]. Molecules are linked by intermolecular C-H center dot center dot center dot O and C-H center dot center dot center dot N interactions forming R(2)(1) (6) and R(2)(2) (10) rings, and R(6)(6) (34) and R(4)(4) (26) macro-rings, all of which are aligned along the [(1) over bar 01] direction, and R(2)(2) (10) and R(2)(1) (7) rings aligned along the [010] direction. The combination of chains of rings along the [(1) over bar 01] and [010] directions generates the three-dimensional structure. A total of 27 systems containing the DNPO molecule and forming molecular complexes of an organic nature were analysed and compared with the structural characteristics of the dioxide reported here. The N-O distance [1.325 (2) angstrom] depends not only on the interactions involving the O atom at the N-O group, but also on the structural ordering and additional three-dimensional interactions in the crystal structure. A density functional theory (DFT) optimized structure at the B3LYP/6-311G(d,p) level is compared with the molecular structure in the solid state.

Enzymatic Kinetic Resolution of tert-Butyl 2-(1-Hydroxyethyl)phenylcarbamate, A Key Intermediate to Chiral Organoselenanes and Organotelluranes

The enzymatic kinetic resolution of tert-butyl 2-(1-hydroxyethyl) phenylcarbamate via lipase-catalyzed transesterification reaction was studied. We investigated several reaction conditions and the carbamate was resolved by Candida antarctica lipase B (CAL-B), leading to the optically pure (R)- and (S)-enantiomers. The enzymatic process showed excellent enantioselectivity (E > 200). (R)- and (S)-tert-butyl 2-(1-hydroxyethyl) phenylcarbamate were easily transformed into the corresponding (R)and (S)-1-(2-aminophenyl)ethanols.

5-Methyl-2,4-bis(methylsulfanyl)tricyclo[6.2.1.0(2,7)]undeca-4,9-diene-3,6-dione

The structure analysis of the title compound, C(14)H(16)O(2)S(2), shows the SMe and H atoms of the bond linking the six-membered rings to be syn and also to be syn to the bridgehead -CH(2)- group. Each of the five-membered rings adopts an envelope conformation at the bridgehead -CH(2)- group. The dione-substituted ring adopts a folded conformation about the 1,4-C center dot center dot center dot C vector, with the ketone groups lying to one side. The cyclohexene ring adopts a boat conformation.

The line structure of balanced ternary designs with block size three, index three and rho(2) = 1, 2

In this paper necessary and sufficient conditions for a vector to be the fine structure of a balanced ternary design with block size 3, index 3 and rho(2) = 1 and 2 are determined with one unresolved case.

Application of the maximum entropy method to the (2 + 1)D four-fermion model

We investigate spectral functions extracted using the maximum entropy method from correlators measured in lattice simulations of the (2+1)-dimensional four-fermion model. This model is particularly interesting because it has both a chirally broken phase with a rich spectrum of mesonic bound states and a symmetric phase where there are only resonances. In the broken phase we study the elementary fermion, pion, sigma, and massive pseudoscalar meson; our results confirm the Goldstone nature of the π and permit an estimate of the meson binding energy. We have, however, seen no signal of σ→ππ decay as the chiral limit is approached. In the symmetric phase we observe a resonance of nonzero width in qualitative agreement with analytic expectations; in addition the ultraviolet behavior of the spectral functions is consistent with the large nonperturbative anomalous dimension for fermion composite operators expected in this model.

Link invariants associated with gauge equivalent solutions of the Yang-Baxter equation: The one-parameter family of minimal typical representations of Uq[gl(2|1)]

In this paper we investigate the construction of state models for link invariants using representations of the braid group obtained from various gauge choices for a solution of the trigonometric Yang-Baxter equation. Our results show that it is possible to obtain invariants of regular isotopy (as defined by Kauffman) which may not be ambient isotopic. We illustrate our results with explicit computations using solutions of the trigonometric Yang-Baxter equation associated with the one-parameter family of minimal typical representations of the quantum superalgebra U-q,[gl(2/1)]. We have implemented MATHEMATICA code to evaluate the invariants for all prime knots up to 10 crossings.

Disciplina 2.1: economia brasileira

A disciplina teve como principais conte??dos: a necessidade do Estado. Externalidades e bens p??blicos. Padr??es de interven????o do Estado e as fun????es econ??micas: alocativa, distributiva e estabilizadora. Equidade e efici??ncia. O financiamento do Setor P??blico. Sistema Tribut??rio Brasileiro. Pol??tica econ??mica: fiscal, monet??ria e cambial

Disciplina 2.1: economia brasileira

Da industrializa????o brasileira ?? crise do desenvolvimentismo na d??cada de 80. A estabiliza????o da economia: do Plano Real aos dias atuais. As pol??ticas de desenvolvimento dos anos 90 e a crise do final da d??cada. A pol??tica macroecon??mica atual: fundamentos e principais resultados. Desenvolvimento econ??mico, distribui????o de renda e pobreza. A atual crise financeira: causas, desenvolvimento, pol??ticas antic??clicas e situa????o do Brasil. Um breve panorama das agendas priorit??rias do governo atual

Conjecture about global fixed-priority preemptive multiprocessor scheduling of implicit-deadline sporadic tasks: the utilization bound of SM-US(sqrt(2)-1) is sqrt(2)-1

Consider global fixed-priority preemptive multiprocessor scheduling of implicit-deadline sporadic tasks. I conjecture that the utilization bound of SM-US(√2−1) is √2-1.

Studies on human anti-rabies immunization in Brazil: II - Preliminary evaluation of the 2-1-1 schedule for human pre-exposure anti-rabies immunization, employing suckling mouse brain vaccine

This study reports preliminary results of virus neutralizing antibody (VNA) titers obtained on different days in the course of human anti-rabies immunization with the 2-1-1 schedule (one dose is given in the right arm and one dose in the left arm at day 0, and one dose is apllied on days 7 and 21), recommended by WHO for post-exposure treatment with cell culture vaccines. A variant schedule (double dose on day zero and another on day 14) was also tested, both employing suckling mouse brain vaccine. A complete seroconversion rate was obtained after only 3 vaccine doses, and almost all patients (11 of 12) presented titers higher than 1.0 IU/ml. Both neutralizing response and seroconversion rates were lower in the group receiving only 3 doses, regardless of the sample collecting day. Although our results are lower than those found with cell culture vaccines, the geometry mean of VNA is fully satisfactory, overcoming the lower limit recommended by WHO of 0.5 IU/ml. The 2-1-1 schedule could be an alternative one for pre exposure immunization, shorter than the classical 3+1 regimen (one dose on days 0, 2, 4 and 30) with only three visits to the doctor, instead of four.

Observações sôbre a terapêutica da ascaridiose com o hidroclorato e com o ciclamato de 2,3,5,6 – Tetrahidro - 6 fenil - imidazo (2,1-b) tiazol

Os autores estudam a ação do ciclamato e do cloridrato de 2, 3, 5, 6, - Tetrahidro-6-fenil-imidazo (2,1-b) tiazol no tratamento da ascaridiose. Foram tratados ao todo 84 indivíduos sendo 48 com o cloridrato e 36 com o ciclamato. O índice de cura com o primeiro foi de 83,9% e com o segundo de 76,4%. Nenhuma reação colateral foi observada com o emprêgo do cloridrato sendo que com o ciclamato 53,6 dos pacientes apresentaram sintomas discretos de intolerância. Os índices de cura assemelham-se aos observados com a piperazina que é a medicação clássica para terapêutica da ascaridiose.