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Refeat R.M.,Nuclear and Radiological Regulatory Authority NRRA
Kerntechnik | Year: 2015

A tendency to increase the discharge burnup of nuclear fuel for Advanced Pressurized Water Reactors (PWR) has been a characteristic of its operation for many years. It will be able to burn at very high burnup of about 70 GWd/t with UO2 fuels. The U-235 enrichment must be higher than 5 %, which leads to the necessity of using an extremely efficient burnable poison like Gadolinium oxide. Using gadolinium isotope is significant due to its particular depletion behavior ("Onion-Skin" effect). In this paper, the MCNPX2.7 code is used to calculate the important neutronic parameters of the next generation fuels of PWR. K-infmity, local peaking factor and fission rate distributions are calculated for a PWR assembly which burn at very high burnup reaching 70 GWd/t. The calculations are performed using the recently released evaluated Gadolinium cross section data. The results obtained are close to those of a LWR next generation fuel benchmark problem. This demonstrates that the calculation scheme used is able to accurately model a PWR assembly that operates at high burnup values. © 2015 Carl Hanser Verlag GmbH & Co. KG. Source

Louis H.K.,Nuclear and Radiological Regulatory Authority NRRA
Kerntechnik | Year: 2014

Reactor kinetic parameters are very important for safety analysis in power reactors. This paper focused on calculations of kinetic parameters such as the effective delayed neutron fraction (ßeff), the neutron generation time (Λ) and the prompt neutron lifetime lp for PWR. In this paper the burn-up calculations were performed to calculate kinetic parameters as a function of burn-up for a PWR when fueled with standard UO2 fuel and MOX (Mixed-Oxide) fuel in order to study the impact of burn-up on these parameters. The calculations were performed using the Monte Carlo code MCNPX. The core chosen for the simulation is based on a 4-loop Westinghouse PWR power plant. The calculations were performed from beginning of the life to the end of life 210 days and compared with safety values taken from the design control document of an API000 PWR. The results are in agreement for UO2 but not for MOX until end of cycle (EOC). Source

Elabd A.A.,Nuclear and Radiological Regulatory Authority NRRA | Attia M.S.,University of Jeddah | Attia M.S.,Ain Shams University
Journal of Luminescence | Year: 2015

Abstract A new, simple and sensitive method for the assessment of UO22+ was developed. The method is based on the quenching of the fluorescence intensity of the thin film optical sensor 1-(2,3,4-trimethoxybenzyl) piperazine [Trimetazidine] doped in sol gel matrix in the presence of different UO22+ concentrations in DMSO. The remarkable quenching of the fluorescence intensity of Trimetazidine by various UO22+ concentrations was successfully used as a new optical sensor for the assessment of UO22+ in DMSO at λexem=340/374 (nm). The mechanism of the interaction between the optical sensor and UO22+ was discussed. The calibration plot was achieved over the concentration range 1.7 × 10-6-4.9 × 10-8 mol L-1 with a correlation coefficient of (0.999) and limit of detection (LOD) and limit of quantification (LOQ) are 4.1 × 10-8 and 1.2 × 10-7 mol L-1, respectively. © 2015 Elsevier B.V. All right sreserved. Source

Elabd A.A.,Nuclear and Radiological Regulatory Authority NRRA | Attia M.S.,University of Jeddah | Attia M.S.,Ain Shams University
Journal of Luminescence | Year: 2016

A new fluorescent optical sensor for highly sensitive and selective assessment of UO2 2+ in aqueous samples was introduced. The response of the sensor is based on the fluorescence quenching of [(+)-(S)-methyl 2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)acetate] (Clopidogrel) embedded in polymethylmethacrylate (PMMA) polymer by UO2 2+. The sensor displays; wide concentration range from 1.0×10-9 to 4.0×10-6 mol L-1, limit of detection (LOD) and limit of quantification (LOQ) are 2.6×10-10 and 7.8×10-10 mol L-1, respectively with a relatively fast response time of less than 60 s. The present sensor was revealed good response characteristics with respect to stability, reproducibility, sensitive and selectivity. Also, the response and quenching mechanisms for the present sensor were discussed. © 2015 Elsevier B.V. Source

A new "turn-off" fluorescent sensor for determination of thorium (Th(iv)) by thin film of 2-(acetyloxy)-N-(5-nitro-2-thiazolyl)-benzamide (L) embedded in sol-gel matrix was introduced. The high efficiency of quenching was caused by non-covalent binding of the positively charged Th(iv) to the negatively charged L. The quenching mechanism is discussed. Judging from temperature and UV-visible absorbance spectra, the quenching mechanism was proved to be static. The stoichiometry and binding ability of L during complexation with Th(iv) were estimated by Job's, Hill's and modified Benesi-Hildebrand plots. Under optimized conditions, a fluorescence quenched at λex/λem = 420/482 (nm) after 2 min, which was linearly related to the concentration of Th(iv) in the range of 3.0 × 10-8 to 1.0 × 10-6 mol L-1. By comparing with selected developed optical sensors, the present sensor exhibits remarkable advantages with satisfactory results that could be used as a tool in nuclear-safeguards material accountability measurements for Th(iv) determination as a "turn-off" fluorescent sensor. © 2016 The Royal Society of Chemistry. Source

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