Eduardo Manzanares-Acuña

Neutron and gamma-ray spectra of 239PuBe and 241AmBe.

Neutron and gamma-ray spectra of 239PuBe and 241AmBe were measured and their dosimetric features were calculated. Neutron spectra were measured using a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. The 239PuBe neutron spectrum was measured in an open environment, while the 241AmBe neutron spectrum was measured in a closed environment. Gamma-ray spectra were measured using a NaI(Tl) scintillator using the same experimental conditions for both sources. The effect of measuring conditions for the 241AmBe neutron spectrum indicates the presence of epithermal and thermal neutrons. The low-resolution neutron spectra obtained with the multisphere spectrometer allows one to calculate the dosimetric features of neutron sources. At 100 cm both sources produce approximately the same count rate as that of the 4.4 MeV gamma-ray per unit of alpha emitter activity.

Multielement measurements in Mexican cigarette tobacco

The concentration of 21 elements in cigarette tobacco in nine different brands manufactured and commercially available in Mexico has been determined using neutron activation analysis. The concentration range of the measured elements (in μg g−1) were: As, (four brands) <0.55–3.24; Ba, 64–251; Br, (four brands) 49–136; Ce, <0.3–1.7; Co, 0.29–0.55; Cr, <0.8–2.4; Cs, 0.091–0.40; Eu, <0.03; Fe, 420–680; Hf, <0.03–0.13; K, (four brands) 18300–40300; La, (four brands) <0.2–0.66; Na, (four brands) 309–566; Rb, 19–50; Sb, <0.7; Sc, 0.13–0.22; Se, <0.7; Sm, (four brands) 0.07–0.14; Sr, 227–472; Th, <0.1–0.17 and Zn, 14–56. The results are compared with the literature values for the concentration of the above elements in cigarette tobacco from other countries.

Elemental content in ground and soluble/instant coffee

The concentration of thirty-four elements in twelve coffee brands has been measured using instrumental neutron activation analysis. The samples investigated included four brands of commercially available ground coffee and eight brands of soluble/instant coffee. The elements measured were Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Gd, Hf, K, La, Lu, Mg, Mn, Na, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, Ti, Tm, U, V, Yb and Zn. Twenty four elements were found to be below the detection limit in one or more samples. These elements were Ce, Cr, Fe, V, As, Eu, Ba, Dy, Gd, Hf, La, Lu, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, Ti, Yb, Tm, and U.

Niveles de plomo en la población de alto riesgo y su entorno en San Ignacio, Fresnillo, Zacatecas, México

Objective. To determine the lead concentration in the blood of children and nursing or pregnant women from San Ignacio, Fresnillo, in Zacatecas, Mexico as well as in soil, plants, ash and lead-glazed pottery, in order to determine exposure due to a metal-recycling facility. Material and Methods. The study was carried out from December 2004 to April 2005. Lead in blood was measured with anodic stripping voltammetry, while dispersive energy X-ray fluorescence was used in the other matrices. Results. Based upon the criteria outlined in the Official Mexican Standards, 90% of the children was identified as category I, 5% as category II and another 5% as category III. The soil in the land near the facility contained from 73 to 84 238 ∝g/g, with an average of 4940 ∝g/g. Larger lead concentrations were found on sites located closer to the facility. San Ignacio’s soil contained, on average, 109 ∝g/g. High lead levels were found in glazed pottery and the concentration in agricultural crops was greater than 300 ∝g/g. Conclusions. Although the majority of children in San Ignacio have blood lead concentrations considered to be acceptable according to the Official Mexican Standards, several studies indicate that deleterious effects on children’s health exist even at low concentrations. The land around the metal recycling facility is contaminated with lead, and to that extent, the crops that are produced there, once ingested, are a source of contamination, which is compounded by the use of glazed pottery. Manzanares-Acuna E, Vega-Carrillo HR, Salas-Luevano MA, Hernandez-Davila VM, Letechipia-de Leon C, Banuelos-Valenzuela R. Niveles de plomo en la poblacion de alto riesgo y su entorno en San Ignacio, Fresnillo, Zacatecas, Mexico. Salud Publica Mex 2006;48:212-219.

Spectrometry and dosimetry of a neutron source

Using the Monte Carlo methods, the spectrum, dose equivalent and ambient dose equivalent of a 239PuBe have been determined at several distances. The spectrum and both doses were determined to 100 cm with a Bonner sphere spectrometer. These quantities were obtained by unfolding the spectrometer count rates using artificial neural networks. The dose equivalent was measured with the area neutron dosemeter Eberline model NRD, to 100, 200 and 300 cm. All the measurements were carried out in an open space to avoid the room-return. With these results, it was found that this source has a yield of 8.41E(6) n/s. †Paper presented as a contribution to the 10th International Symposium on Solid State Dosimetry, Mexico City (24–28 September 2007).

Elemental analysis of air dust from Zacatecas City, Mexico

Abstract The concentration of 25 elements in air dust particulate matter collected in 27 sites distributed along Zacatecas City in Mexico was determined using instrumental neutron activation analysis. The objective of the study was to characterize the elemental composition in the particulate matter. The concentration range (in μg/g) of the measured elements was as follows: As (3.99 – 63.1); Ba (240 – 4330); Br (1.56 – 23); Ce (22.1 – 187); Co (4.86 – 39.9); Cr (54.9 – 184); Cs (2.24 – 19.7); Eu (0.21 – 0.88); Fe (10 600 – 37 400); Hf (1.46 – 6.31); Hg (0.34 – 12.2); K (2600 – 15 600); La (3.84 – 84.8); Na (2070 – 10 800); Rb (24.1 – 120); Sb (6.21 – 20.9); Sc (3.14 – 16.1); Se (

Neutron source for Neutron Capture Synovectomy

Monte Carlo calculations were performed to obtain a thermal neutron field from a 239PuBe neutron source inside a cylindrical heterogeneous moderators for Neutron Capture Synovectomy. Studied moderators were light water and heavy water, graphite and heavy water, lucite and polyethylene and heavy water. The neutron spectrum of polyethylene and heavy water moderator was used to determine neutron spectra inside a knee model. In this model the elemental composition of synovium and synovial liquid was assumed like blood. Kerma factors for synovium and synovial liquid were calculated to compare with water Kerma factors, in this calculations the synovium was loaded with two different concentrations of Boron.

Monte Carlo-based method to determine the strength of a neutron source

The utilization of a gamma-ray spectrometer with a 7.62 Ø×7.62 cm NaI(Tl) detector, with a spherical moderator, has been studied with the aim to measure the neutron fluence rate and to determine the neutron source strength. Moderators with a large amount of hydrogen are able to slowdown and thermalize neutrons; once thermalized, there is a probability for thermal neutrons to be captured by hydrogen, producing 2.22 MeV gamma rays. The pulse-height spectrum collected in a multichannel analyzer shows a photopeak around 2.22 MeV whose net area is proportional to total neutron fluence rate and to the neutron source strength. The characteristics of this system were determined by a Monte Carlo study using the MCNP 4C code, where a detailed model of the NaI(Tl) was utilized. Spheres of diameters 3, 5, and 10 inch were used as moderators, and the response was calculated for monoenergetic and isotopic neutrons sources.

Mammography X‐Ray Spectra Simulated with Monte Carlo

Monte Carlo calculations have been carried out to obtain the x‐ray spectra of various target‐filter combinations for a mammography unit. Mammography is widely used to diagnose breast cancer. Further to Mo target with Mo filter combination, Rh/Rh, Mo/Rh, Mo/Al, Rh/Al, and W/Rh are also utilized. In this work Monte Carlo calculations, using MCNP 4C code, were carried out to estimate the x‐ray spectra produced when a beam of 28 keV electrons did collide with Mo, Rh and W targets. Resulting x‐ray spectra show characteristic x‐rays and continuous bremsstrahlung. Spectra were also calculated including filters.

Absorbed Dose in the Uterus of a Three Months Pregnant Woman Due to 131I

The use of 131I is widely used in diagnostic and treatment of patients. If the patient is pregnant the 131I presence in the thyroid it becomes a source of constant exposition to other organs and the fetus. In this study the absorbed dose in the uterus of a 3 months pregnant woman with 131I in her thyroid gland has been calculated. The dose was determined using Monte Carlo methods in which a detailed model of the woman has been developed. The dose was also calculated using a simple procedure that was refined including the photons’ attenuation in the woman organs and body. To verify these results an experiment was carried out using a neck phantom with 131I. Comparing the results it was found that the simple calculation tend to overestimate the absorbed dose, by doing the corrections due to body and organs photon attenuation the dose is 0.14 times the Monte Carlo estimation.