Seeking optimal material distribution in a nuclear system to maximize a response function of interest has been a subject of considerable interest in nuclear engineering. Examples are the optimal fuel distribution in a nuclear reactor core to achieve uniform burnup using minimum critical mass and the use of composite materials with an optimal mix of constituent elements in detection systems and radiation shielding. For such studies, variational methods have been found to be useful but, they have been used for standalone analyses often restricted to idealized models, while more elaborate design studies have required computationally expensive Monte Carlo simulations ill-suited to iterative schemes for optimization. Such an inherent disadvantage of Monte Carlo methods changed with the development of perturbation algorithms but, their efficiency is still dependent on the reference configuration for which a hit-and-trial approach is often used. In the first illustrative example, this paper explores the computational speedup for a bare cylindrical reactor core, achievable by using a variational result to enhance the computational efficiency of Monte Carlo design optimization simulation. In the second example, the effect of non-uniform material density in a fixed-source problem, applicable to optimal moderator and radiation shielding, is presented. While applications of this work are numerous, the objective of this paper is to present preliminary variational results as inputs to elaborate stochastic optimization by Monte Carlo simulation for large and realistic systems.

The present work studies the effect of introducing MOX fuel on Westinghouse AP1000 neutronic parameters. The neutronic calculations were performed by using the MCNP6 code with the ENDF/B-VII.1 library and the new release of the ENDF/B-VIII, the AP1000 core with three 235U enrichment zones (2.35 %, 3.40 %, and 4.45 %). The obtained results showed that the simulated model for the AP1000 core satisfies the optimization criteria as a Westing- house reference. The results which included: effective multiplication factor, keff, delayed neutron fraction, beff, excess reactivity, rex, shutdown margin, temperature reactivity coefficients, whole core depletion, neutron flux, power peaking factor and core power density, were calculated and compared with the available published results. The keff in the cold zero power was found to be 1.20495 and 1.20247 with the ENDF/B-VII.1 and the ENDF/B-VIII libraries, respectively, which matches the value of 1.205 presented in the AP1000 Design Control Document for the UO2 fuel core. On the other hand, keff in the cold zero power was found to be 1.19988 and 1.19860 for MOX core with the ENDF/B-VII.1 and the ENDF/B-VIII libraries, respectively, which show good reception and confirm the safety of the design and efficient modeling of AP1000 reactor core.

To understand the nuclear structure for most elements, it is essential to investigate the nuclear excitations by using high precision gamma-ray spectroscopy in which intensive measurements should be carried out. This is becoming a new challenge for the radiation scientific community nowadays, where the instrumentations and technical advances must be developed to be used in a wide range of applications. To discover the weakest nuclear reaction, the maximum probability of the detection system of the total energy of any released individual photon must be determined. In this work, a new mathematical method to calculate the absolute full-energy peak efficiency of asymmetrical polyhedron germanium detector is presented. This type of detector can be arranged in array, forming ?complex detectors of encapsulated germanium crystals?, with the solid angle reaching 82 % of total solid angle coverage, i. e., with the highest possible efficiency and with a good quality of spectral response. In addition, the photon path length was enclosed in the mathematical method to determine its attenuation through different materials such as, the detector active medium and any other material in-between source-detector system during the measuring process. The comparison between the efficiency calculated in this work and that of the published Monte Carlo simulation showed a good agreement and a small variation. However, the method discussed in the current work can be useful in nuclear safeguards, in overcoming the huge difficulties in identification of the energy range of radioactive isotopes and their quantities in nuclear waste.

Editorial Board of the Nuclear Technology & Radiation Protection journal regrets to in form the audience of the journal that in the list of authors of the article APPLICATION OF AN ELECTRONEGATIVE GAS AS A THIRD COMPONENT OF THE WORKING GAS IN THE GEIGER-MULLER COUNTER by Luka S. PERAZIC, Cedomir I. BELIC, and Dalibor B. ARBUTINA published in the Vol. 33 (2018), 3, pp. 268-274, was made a mistake concerning the third author''s name. It should be as follows: Dalibor S. ARBUTINA Editorial Board offers an apology for this mistake to Mr. Dalibor S. Arbutina and the readers of the Nuclear Technology & Radiation Protection journal. <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/NTRP1803268P">10.2298/NTRP1803268P</a></b></u>

The computed tomography has become a standard tool in radiation therapy treatment planning. Additionally, there is a growing awareness of the dose delivered to the part of the body outside the target volume. The ionizing radiation carries a stochastic risk of malignancy, therefore, the doses should be kept as low as reasonably achievable in order to provide an adequate information needed for the radiotherapy planning. The objective of this work was to set up the initial diagnostic reference levels and correlate to the image quality that would be used in the future optimization of localization scans. To quantify the doses from computed tomography localization scans at the University Hospital Rijeka, local diagnostic reference levels were established for five most common procedures of different anatomical regions; head, head and neck, pelvis, breast and thorax. The Computed Tomography Dose Index volumetric and the Dose-Length Product were used as dose indicators and scanning parameters were also recorded. The image quality assessment was performed for each set of images. The results were compared to the seldom published data in order to compare the clinical practice. The image quality for almost all of the body regions are scored as acceptable in average but require improvement. It is shown that the optimization of radiotherapy protocols is required. Therefore, these results will be used as a guideline for that process. The establishment of the national diagnostic reference levels for computed tomography localization procedures in radiation therapy is the next step and is currently an ongoing process.

Electron field emission limiting the accelerating gradient in superconducting cavities remains the dominant setback in cavity production. The need to understand and control the field emission has become increasingly important because of the prospect of using high-gradient structures in linear colliders. Since building an accelerator structure is a complicated and costly process, elimination of unnecessary steps has priority. In this paper an analysis of the influence of the enhanced field emission in superconducting radio frequency cavity together with modal field calculations by using COMSOL finite elements package has been presented. The obtained results reveal that the electric field required for the field emission is generated in the cavity irises. The imperfection of the cavity surface leading to very high fields is modelled by a simple cone. The estimated value of the enhancement factor for the cone tip of around 4 is in a good agreement with the data found in the literature. In addition, from the slopes and the intercepts of the Fowler-Nordheim plots, a dependence of the enhancement factor and the effective area on the work function has been estimated.

This work reports on the spatial rainbows occurring in transmission of 10 keV protons through hexapole lens. Positive potentials of the lens electrodes are set to be 0.9, 2, and 5 kV. The spatial rainbows and corresponding proton distributions are calculated by using an accurate analytical approximation of the numerically obtained lens potential. Further, for the positive potential of the lens electrode equal to 0.9 kV, it has been shown that application of catastrophe theory leads to a simple polynomial non-linear mapping, generating accurate spatial rainbows at the exit and in the drift space behind the lens.

In the present investigation, a surface-deposited polonium was measured in 37 houses in Rasht and Ramsar cities of Iran with the aim of evaluating the retrospective radon concentration. The CR-LR technique is widely used in this regard, but for the first time, Lexan polycarbonate detectors were used to measure the activity of 210Po planted in glassy objects. These detectors were placed on glassy surfaces for 153 to 365 days. A passive cylindrical diffusion chamber was used for the contemporary radon concentration measurements. The diffusion chamber consists of the Lexan polycarbonate films as a solid state nuclear track detectors and filter. The surface-deposited 210Po activity concentration was found to vary from 0.26 to 11.96 mBqcm-2 with average of 2.62 mBqcm-2. The sensitivity of 210Po to polycarbonate was determined to be 0.06456 track per cm2 per mBqhcm-2. Thus, the radon concentration was found to vary from 122 to 4840 Bqm-3 with an average value 1243 Bqm-3 and the contemporary radon concentration in the area was found to vary from 15 to 2420 Bqm-3 with an average 513 Bqm-3. The results indicate that there is a significant correlation between the concentration of the retrospective radon and the concentration of the contemporary radon gas in the indicated areas with a coefficient of 0.80672.

The aim of this paper is applying statistical laws and enlargement law to determine a redundancy level of nanotechnology computers with a pre-given statistical confidence. We have tested radiation hardness of MOS memory components (commercial EPROM memory) using both Monte Carlo simulation method and experimental procedure. Then, by using the statistical enlargement law, we have performed the analysis of redundancy optimization of MOS structure for nanotechnology computers, under the influence of background radiation, and obtained more than satisfying results.

This study presents the concentrations of radionuclides and heavy metals in twenty-six table olive (Olea europaea L.) samples, and an assessment of the health risks associated with their consumption. The samples were collected from different towns in the Mediterranean region of Turkey, one of the major olive-producing countries in the world. The average activity concentrations of 226Ra, 232Th, 40K, and 137Cs in the edible parts of the table olive samples were found as 37.9 ? 4.1, 7.1 ? 0.5, 274.6 ? 14.7, and 7.2 ? 0.7 Bqkg (dw), respectively, by using a gamma ray spectrometer. The effective radiation dose due to the intake of these radionuclides through ingestion of olive samples varied from 3.4 to 22.7 ?Sv with an average value of 11 ? 1 ?Sv. The average concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, and Pb in the edible parts of the table olive samples were determined as 2.04, 11.08, 166.60, 0.20, 10.29, 13.81, 14.34, 4.50, and 4.55 ?gg?1, respectively, by using an inductively coupled plasma optical emission spectrometer. Based on the measured content of the radionuclides and heavy metals, the results imply that table olives are safe for human consumption.