Beam port filters in a TRIGA MARK III nuclear reactor to produce epithermal neutrons for BNCT.

Glioblastoma multiforme is the most common and aggressive brain tumor and it is difficult to treat with conventional surgery, chemotherapy, or radiation therapy. An alternative treatment is boron neutron capture therapy which requires an energy modulated beam of neutrons and a10B drug capable of adhering to the tumor. In this work, MCNP6 Monte Carlo code was used to evaluate the effect on the neutron spectrum by placing two filters along the radial beam tube of the TRIGA Mark III nuclear reactor of ININ in Mexico. Every filter was made with the same amount and type of materials: Steel and Graphite for filter 1 and Cadmium, Aluminum, and Cadmium (Cd + Al + Cd) for filter 2. Two cases were analyzed for each filter as follows: Case A for filter 1 was considering 30 cm of steel and 30 cm of graphite, while for case B, the dimensions of filter 1 were 15 cm of steel, 15 cm of graphite, 15 cm of steel and 15 cm of graphite. Cases A and B for filter 2 were analyzed considering the same dimensions and amount of materials. The work was in the aim to produce epithermal neutrons for boron neutron capture therapy. Neutron spectra were calculated at three sites along the beam tube and two sites outside the beam tube; here, the ambient dose equivalent, the personal dose equivalent, and the effective doses were also estimated. At a distance of 517 cm of core, in case B, results in an epithermal-to-thermal neutron fluence ratio of 30.39 was obtained being larger than the one recommended by the IAEA of 20.

CubBonner - A novel passive neutron area monitor.

Responses of a novel passive neutron area monitor, named CubBonner, were calculated. The responses were estimated for sixty monoenergetic neutrons, from 10-9 to 20 MeV, with the MCNP5 code. The CubBonner is a cubic polyethylene moderator and a gold foil as thermal neutron detector. The ambient dose equivalent response was calculated for three cubes (5″, 8″ and 10" side) with the gold foil at the cube's centers. The moderator cube having the best ambient dose equivalent response was used to estimate the neutron fluence and the 197Au(n,γ) responses per history. The ambient dose response per unit mass of gold was compared with the response of the Berthold LB 6411 active neutron area monitor, and the response for the (n,γ) reaction in the gold foil was compared with the evaporation photo neutrons produced in linear accelerators for radiotherapy.

Synthesis and thermoluminescent response to γ-rays and neutrons of MgB4O7:Dy and MgB4O7:Dy,Na.

MgB4O7 doped with rare earths and alkaline elements has been reported as a good TLD because of its high sensitivity, effective atomic number close to that of biological tissue and low fading. In this work, thermoluminescent matrices were synthesized of MgB4O7:Dy and MgB4O7:Dy, Na to evaluate their thermoluminescent response (TL) when exposed to γ-rays and neutrons. The amount of Dy was studied in a concentration range of 0.01-1.5 mol% of total doping, while for Na the concentration of 0.5 mol% was established to determine the TL response as a function of doping. The synthesis of the powders was carried out by the method of wet reaction assisted by heat treatment and the samples were characterized by techniques of scanning electron microscopy and X-ray diffraction to determine the size of grain and crystallographic phase. For the dosimetric study, thermoluminescent phosphors were irradiated with a source of 137Cs at an estimated dose 6.8 ±â€¯0.4 mGy to evaluate their response to γ-rays exposure, while for neutrons a source of 241AmBe was used (estimated dose of 3.1 ±â€¯0.1 mGy). The thermoluminescent responses are similar for all materials exposed to γ-rays as for neutrons, the differences are shown to 280 °C, where a peak of high temperature is observed in materials exposed to neutrons.

Doses in eye lens, thyroid, and gonads, due to scattered radiation, during a CT radiodiagnosis study.

X-ray images used for radio-diagnosis are very useful to evaluate the progress of a treatment or to have a better diagnosis. However, during the interaction between the incoming X-ray beam and the body surface, part of the radiation is scattered out reaching other parts of the body delivering an undesirable dose. In this work the dose in eye lenses, thyroid, and gonads of a solid water phantom was measured using thermoluminescent dosimeters, while a Computer Tomography of the torso was obtained. With the measured absorbed dose the effective dose was calculated. Thus, the effective dose in the eye lens, thyroid, and gonads is approximately 57, 214 and 9 µSv respectively. The largest effective dose was on that area located nearest to the region where the radiation is scattered.

Neutron production in the interaction of 12 and 18 MeV electrons with a scattering foil inside a simple LINAC head.

The characteristics of photons and neutrons produced during the interaction between a monoenergetic (12 and 18 MeV) electron beam and a tungsten scattering foil enclosed into a 10 cm-thick tungsten shell have been determined using Monte Carlo methods. This model was used aiming to represent a linac head working in electron-mode for cancer treatment. Photon and neutron spectra were determined around the scattering foil and to 50 and 100 cm below the electron source. Induced photons are mainly produced along the direction of the incoming electron beam. On the other hand, neutrons are produced in two sites, mainly in the inner surface of the linac head and in less extent in the scattering foil. The neutron spectra are evaporation neutrons which are emitted isotropically from the site where are produced leaking out from the linac head, reaching locations were the patient is allocated.