Design of a boiling water reactor equilibrium core using thorium-uranium fuel

In this paper the design of a Boiling Water Reactor (BWR) equilibrium core using thorium is presented; a heterogeneous blanket-seed core arrangement concept was adopted. The design was developed in three steps: in the first step two different assemblies were designed based on the integrated blanket-seed concept, they are the blanket-dummy assembly and the blanket-seed assembly. The integrated blanketseed concept comes from the fact that the blanket and the seed rods are located in the same assembly, and are burned-out in a once-through cycle. In the second step, a core design was developed to achieve an equilibrium cycle of 365 effective full power days in a standard BWR with a reload of 104 fuel assemblies designed with an average 235U enrichment of 7.5 w/o in the seed sub-lattice. The main operating parameters, like power, linear heat generation rate and void distributions were obtained as well as the shutdown margin. It was observed that the analyzed parameters behave like those obtained in a standard BWR. The shutdown margin design criterion was fulfilled by addition of a burnable poison region in the assembly. In the third step an in-house code was developed to evaluate the thorium equilibrium core under transient conditions. A stability analysis was also performed. Regarding the stability analysis, five operational states were analyzed; four of them define the traditional instability region corner of the power-flow map and the fifth one is the operational state for the full power condition. The frequency and the boiling length were calculated for each operational state. The frequency of the analyzed operational states was similar to that reported for BWRs; these are close to the unstable region that occurs due to the density wave oscillation phenomena in some nuclear power plants. Four transient analyses were also performed: manual SCRAM, recirculation pumps trip, main steam isolation valves closure and loss of feed water. The results of these transients are similar to those obtained with the traditional UO2 nuclear fuel

Simulador para un yacimiento de gas basado en una solución numérica explícita

En este trabajo se presenta las ecuaciones fundamentales para desarrollar un simulador de yacimiento de gas acoplado a un pozo productor. El simulador se construye utilizando la ecuación gobernante para el pozo en estado estacionario, la cual está acoplada a la ecuación de flujo del yacimiento escrita en forma explícita. La ecuación del pozo se resuelve numéricamente utilizando un esquema de diferencias finitas hacia adelante, mientras que se usa un esquema iterativo para la ecuación explícita del yacimiento con el fin de encontrar la presión en cada bloque numérico a cada paso de tiempo. El simulador depende del tamaño del paso de tiempo para obtener soluciones numéricas estables y consistentes, por lo que el número de bloques para discretizar el yacimiento es reducido. A pesar de esta restricción, el simulador es de utilidad para estimar reservas y el influjo al pozo, realizar la interpretación de pruebas de presión y análisis nodal, etc. El simulador se aplicó en un caso base, donde se determinó las presiones a lo largo del pozo, en fondo de pozo, y en el yacimiento

Prevalence of high-risk HPV genotypes, categorised by their quadrivalent and nine-valent HPV vaccination coverage, and the genotype association with high-grade lesions

BACKGROUND: The new nine-valent vaccine against human papillomavirus (HPV) includes the four HPV genotypes (6, 11, 16, and 18) that are targeted by the older quadrivalent HPV vaccine, plus five additional oncogenic types (31, 33, 45, 52, and 58) remain significantly associated with high grade lesions. We aimed to determine the prevalence of high-risk HPV genotypes in unvaccinated subjects and the association of these genotypes with the incidence of high-grade lesions. We also assessed which, if either, of these two HPV vaccines could have prevented these cases. METHODS: This cross-sectional study, conducted from 4 January 2010 to 30 December 2011, was composed of 595 women attending the Hospital General Universitario de Elche (Spain) gynaecology department who were positively screened for opportunistic cervical cancer by pap smears and HPV detection during a routine gynaecological health check. The pap smear results were classified using the Bethesda system. HPV genotyping was performed with the Linear Array HPV genotyping test, and viruses were classified by the International Agency for Research on Cancer assessment of HPV carcinogenicity. Odds ratios (ORs) with their 95% confidence intervals (95% CI) were estimated by logistic regression, adjusting for age and immigrant status. The prevented fraction among those exposed (PFe-adjusted) was determined as a measure of impact. RESULTS: At least one of the additional five high-risk HPV genotypes present in the nine-valent HPV vaccine was detected in 20.5% of subjects. After excluding women with genotype 16 and/or 18 co-infection, high-risk genotypes (31, 33, 45, 52, and 58) were associated with a higher risk of intraepithelial lesion or malignancy: adjusted OR?=?3.51 (95% CI, 1.29-9.56), PFe-adjusted?=?0.72 (95% CI, 0.22-0.90). Genotypes that are still non-vaccine-targeted were detected in 17.98% of the women, but these were not significantly associated with high-grade lesions. CONCLUSION: The greater protection of the nine-valent HPV vaccine is likely to have a positive impact because, in the absence of genotype 16 or 18 infection, these five genotypes on their own remained significantly associated with high-grade lesions

Search for a vector-like quark T′ → tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at s \sqrt{s} = 13 TeV

A search for the electroweak production of a vector-like quark T′, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at = 13 TeV, corresponding to an integrated luminosity of 138 fb−1. This is the first T′ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T′ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T′ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κT = 0.25 and a relative decay width Γ/MT′ < 5%

Measurement of the Higgs boson inclusive and differential fiducial production cross sections in the diphoton decay channel with pp collisions at s \sqrt{s} = 13 TeV

The measurements of the inclusive and differential fiducial cross sections of the Higgs boson decaying to a pair of photons are presented. The analysis is performed using proton-proton collisions data recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 137 fb$^{−1}$. The inclusive fiducial cross section is measured to be $σ_{fid}$=73.4$^{+5.4}_{−5.3}$(stat)$^{+2.4}_{−2.2}$(syst) fb, in agreement with the standard model expectation of 75.4 ± 4.1 fb. The measurements are also performed in fiducial regions targeting different production modes and as function of several observables describing the diphoton system, the number of additional jets present in the event, and other kinematic observables. Two double differential measurements are performed. No significant deviations from the standard model expectations are observed

A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer

A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp → pp + Z/γ + X, in proton-tagged events from proton–proton collisions at √s = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. odelindependent upper limits on the visible production cross section of pp → pp + Z/γ + X are set