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Void fraction and flow regime determination by means of MCNP code and neural network

Rabiei A., Shamsaei M., Kafaee M., Shafaei M., Mahdavi N.

Nukleonika

2012

Vol. 57, No. 3

345-349

One of the non-intrusive and accurate methods of measuring void fraction in two-phase gas liquid pipe flows is the use of the gamma-transmission void fraction measurement technique. The goal of this study is to describe low-energy gamma-ray densitometry using an 241Am source for the determination of void fraction and flow regime in water/gas pipes. The MCNP code was utilized to simulate electron and photon transport through materials with various geometries. Then, a neural network was used to convert multi-beam gamma-ray spectra into a classification of the flow regime and void fraction. The simulations cover the full range of void fraction with Bubbly, Annular and Droplet flows. By using simulation data as input to the neural networks, the void fraction was determined with an error less than 3% regardless of the flow regime. It has thus been shown that multi-beam gamma-ray densitometers with a detector response examined by neural networks can analyze a two-phase flow with high accuracy.

Investigation of the dose enhancement factor of high intensity low mono-energetic X-ray radiation with labeled tissues by gold nanoparticles

Ranjbar H., Shamsaei M., Ghasemi M. R.

Nukleonika

2010

Vol. 55, No. 3

307-312

The aim of radiotherapy is to maximize the dose applied to the tumor while keeping the dose to the surrounding healthy tissue as low as possible. To further enhance dose to a tumor, techniques to radiosensitization of the tumor, using high atomic number elements, have been proposed. The aim of this study was to investigate the influence of using gold nanoparticles as a contrast agent on tumor dose enhancement when the tissue is irradiated by a typical mono energy X-ray beam. To improve the conventional radiotherapy enhancement of the absorbed dose in a tumor tissue and to spare the skin and normal tissues during irradiation in the presence of concentration agent, a model based on a Monte Carlo N-Particle eXtended (MCNPX) computer code has been designed to simulate the depth dose in a phantom containing an assumed tumor. Test was carried out in two phases. In phase 1, verification of this model using the MCNPX was evaluated by comparing the obtained results with those of the published reports. In phase 2, gold was introduced into assumed tumor inside the phantom at different depths in the simulation program. Simulation was performed for four different concentrations of gold nanoparticles using a low mono-energetic parallel beam of synchrotron radiation. The obtained results show that the optimum energy for dose enhancement is found to be around 83–90 keV for all gold concentrations. The dose enhancement factor is increased linearly with concentration and diminished in depth along the central beam in the tumor. This approach of introducing contrast agents in conventional radiotherapy could hopefully prepare new treatment planning and improve the efficiency of tumor therapy.