International Journal of Nuclear Energy Science and Technology (11 papers in press)
Burn/breed: a wavelet-based nuclear fuel burnup and decay heat code
by Hesham Nasif
Abstract: Burn/breed is a code designed to aid in the analysis, prediction and optimisation of fuel burnup performance and decay heat calculation in a nuclear reactor. The code uses the output parameters generated by the Monte Carlo neutronics codes to determine the isotopic inventory as a function of time and power density. Burn/breed directly uses the neutron absorption tally/reaction information generated by Monte Carlo code for each nuclide of interest to determine the nuclide inventory. When the isotope inventories have been calculated for a specific reactor operation and cooling period, the decay heat can be derived. Beside the U-235 and Pu-239 decay chains, the code includes the U-233 decay chain to manage the possible scenarios for using thorium in a nuclear fuel cycle. This paper describes the theoretical basis of this code, and shows the results of the code for two test cases. The results show good agreement with other codes for the first test case and with the experimental results for the second test case.
Keywords: burn/breed; burnup; decay heat; nuclear reactor; Monte Carlo; isotopic inventory; wavelet; U-233 decay chain.
Testing in sodium and qualification of the bearings used in inclined fuel transfer machine of prototype fast breeder reactor
by S. C. S. P. Kumar Krovvidi, Punniyamoorthy R, Sreedhar B K, Chandramouli S, Padmakumar G, Raghupathy S, Selvaraj P
Abstract: Track roller type double row deep groove ball bearings made of SS-440C material are used in the inclined fuel transfer machine (IFTM) of the prototype fast breeder reactor (PFBR). The bearings are unlubricated hence need to operate under sodium and subsequently in cover gas at 50oC. The number of rotations of the bearings during 40 years of the reactor operation is 1.15 million. This paper presents the experiment carried out to examine the performance of the bearings used in IFTM under simulated conditions as in the reactor. The bearing was initially tested in air, in argon and in sodium at 200oC. It is observed that the frictional torque value of the sodium wetted bearing in cover gas at 50oC is increased owing to solidified sticking sodium on the bearing. Wear in the bearings is significant after 1,065,000 rotations. This paper presents the scheme of testing of the bearing, details of the test facility, test results and discussion. The frequency of replacement of the bearings in IFTM of PFBR is arrived at based on the experiment. This experiment gave better insight into the use of bearings for under-sodium applications.
Keywords: bearings; SS 440C; testing in sodium; SFR application.
Threat modelling on nuclear and radioactive materials based on intelligent approach
by Altab Hossain, A.Z.M. Salahuddin, M.S. Akbar
Abstract: Threat modelling and assessments are the process of gathering, organising and analysing existing or potential threats and deemed to have the capability to lead to a malicious act. Potential adversaries may attempt to unauthorised removal of nuclear materials (NM) or other radioactive materials (RM) for which a physical protection system (PPS) is designed, and therefore must be assessed and prevented. In case of an undesired condition, the authorities have to carry out analytical activities to detect risky circumstances. Hence, in spite of the various methods for threat modelling, it is essential to systematically analyse these threats. Therefore, in this paper, a threat-modelling technique using a fuzzy logic based intelligent approach is designed. The technique involves linking the relationship between input parameters of capability, intent, material and vulnerability and an output parameter of threat level for nuclear and radioactive materials and their adaptation for the early forecast of irregular behaviour. For inputs, overall capabilities of 70%, overall likelihood of 60%, and impact of 60%, the output threat level is estimated as 76.5% for the domestic group deploying an RDD at an annual celebration. Results obtained from the study show the good performance of the developed model compared with results considering a single fuzzy inference system.
Keywords: nuclear materials; physical protection system; threat modelling; Fuzzy logic.
Radiation dose rate assessment around patients in PET/CT units
by Maged Emad El-din, R.M.M. Mahmoud, Ibrahim Eid, M.R. Ezz El-din, R.A. Rizk
Abstract: Radiation exposure assessment for PET/CT units is strongly needed for protection of the work staff and developing working practice and shielding design. The objective of this paper is to assess the radiation exposure resulting from radioactive patients injected with different activities of 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) in Positron Emission Tomography/Computed Tomography (PET/CT) units. This objective is fulfilled by measuring the dose rates practically inside and outside PET/CT rooms around radioactive patients using a calibrated survey meter. Afterwards, the dose rates are estimated mathematically using a Monte Carlo simulation model. The results show that the dose rates on a patients body surface decrease greatly with distance, and it is recommended for PET/CT staff to stand at distances more than 1.5 m from radioactive patients if possible during direct contact. Also, it is found that the shielding thickness of 3 mm lead and 25 cm ordinary concrete for the selected room dimensions is adequate and effective for the ɣ-radiation arising from radioactive patients. The practically measured dose rates around radioactive patients are quite similar to mathematically predicted results, and slight differences may be attributed to the difference between the estimated 18F biological half-life and real biological half-life owing to different biological uptake or excretion time from one patient to another.
Keywords: shielding; Monte Carlo simulation; positron emission tomography; radioactive patients.
Probabilistic fracture mechanics analysis of reactor pressure vessel with underclad and through-clad cracks under pressurized thermal shock transient
by Kuen-Tsann Chen, Kuen Ting, Anh Tuan Nguyen, Lihua Wang, Yuan Chih Li, Tai Liang Kuo
Abstract: Semi-elliptical underclad cracks resulting from the fabrication process of a reactor pressure vessel (RPV) were able to be detected by a non-destructive testing method. The effects of the cracks on the structural integrity of the RPV are determined to be negligible by deterministic fracture mechanics (DFM) analyses. However, after long-term operation under severe conditions, the RPV becomes brittle and susceptible to damage, especially when subjected to pressurised thermal shocks (PTS). Currently, the probabilistic fracture mechanics (PFM) analysis of RPVs with the cracks should be applied to evaluate the safety of operation alongside DFM. To the best of the authors knowledge, few studies or computer codes have applied probabilistic assessment for such cracks, including FAVOR 12.1, a computer code specifically designed to perform PFM analysis for RPV under PTS transients. Therefore, this study conducts PFM analysis for cracks by modifying the calculation procedure of FAVOR 12.1. The results show that during the lifetime of a nuclear power plant, such cracks will not threaten the RPVs safety. Additionally, three methods were proposed to improve FAVOR 12.1s ability to perform PFM analysis for axial through-clad cracking.
Keywords: stress intensity factor; reactor pressure vessel; probabilistic fracture mechanics; pressurised thermal shock.
An analytical nodal method for energy multigroup discrete ordinates transport calculations in two-dimensional rectangular geometry
by Welton Menezes, Hermes Alves Filho, Ricardo Barros
Abstract: A spectral nodal method for energy multigroup X,Y-geometry, discrete ordinates (Sn) problems in a non-multiplying medium is developed. This analytical coarse-mesh method is referred to as the multigroup spectral Greens function constant nodal (SGF-CN) method. The SGF-CN method uses the multigroup SGF method for numerically solving the one-dimensional transverse-integrated Sn nodal equations with constant approximations for the transverse leakage terms. As the energy group transfer scattering source terms are treated analytically in the proposed method, the only approximations occur in the group transverse leakage terms. Numerical results are given to illustrate the methods accuracy for coarse-mesh calculations.
Keywords: discrete ordinates; multigroup model; fixed source; spectral nodal method.
Coupled channel calculations using semi-classical and quantum mechanical approaches for light and medium mass systems
by Fouad A. Majeed, Khalid H.H. AlAteah, Malik S. Mehemed
Abstract: A semi-classical and full quantum mechanical approaches have been used to study the effect of channel coupling on the calculations of the total fusion reaction cross-section σfus, the fusion barrier distribution Dfus and the reaction probability for the light systems (4He+233U, 13C+48Ti) and the medium system (46Ti+46Ti). The semi-classical approach used in the present work is based on the method of the Alder and Winther for Coulomb excitation. The results obtained from our semi-classical and full quantum mechanical calculations are compared with the available experimental data. The semi-classical calculations agree reasonably with the full quantum mechanical treatment and they were able to reproduce the experimental data in details for the total fusion reaction cross-section σfus, the fusion barrier distribution Dfus and the probability of the reaction.
Keywords: semi-classical treatment; quantum treatment; breakup reaction; light systems; medium systems.
Analysis of fuel performance for VVER-1000 reactor using FRAPCON code
by Navid Taheranpour, Saeed Talebi
Abstract: The interaction between radiation and matter provides profound changes in material properties. Therefore, surveying and estimating changes in fuel properties and structural materials during the radiation exposure has paramount importance. Recently, in order to improve the efficiency of LWR, the fuel burn-up rate is increased. Increasing the fuel burn-up causes a rise in thermal and mechanical stresses in the high-radiation environment during reactor's operation; therefore, it is essential for fuel designer to have a thorough assessment of the behaviour of fuel rods during the reactor's operation. In this study, main fuel performance parameters are calculated for a VVER-1000 type reactor using FRAPCON-3.5 code under steady-state conditions and the results are compared with the requirements and acceptable criteria from valid references. Furthermore, constraints on design and safety of VVER reactors are discussed from the perspective of fuel performance.
Keywords: fuel performance; FRAPCON; VVER; PCI; PCMI.
Pin-by-pin minor actinides transmutation analysis for heterogeneous minor actinides target loaded core by reconstruction of neutron spectrum
by Satoshi Takeda, Kazumasa Kobayashi, Takanori Kitada
Abstract: A fast reactor named as minor actinides target loaded core has been developed for effective minor actinides transmutation. The core has a number of minor actinides target assemblies, which contain zirconium-hydride pins. Therefore, the neutron spectrum strongly depends on the location of the fuel pin in the core. In order to evaluate the amount of pin-by-pin minor actinides transmutation accurately, a reconstruction method is proposed. The method reconstructs the pin-by-pin neutron spectrum by combining results of the assembly calculation and the core calculation. The reference Monte Carlo calculation is carried out for verification of the proposed method. The results show that the proposed method provides an accurate pin-by-pin neutron spectrum and an accurate amount of the pin-by-pin minor actinides transmutation compared with conventional assembly-wise evaluation.
Keywords: fast reactor; minor actinide; Zr-H; neutron spectrum; transmutation; pin-by-pin; reconstruction; method of characteristics; Monte Carlo.
Analysis of a VVER-1000 in-core fuel management benchmark with DRAGON and DONJON
by W.F.G. Van Rooijen, Mohammad Jahirul Haque Khan, Alain Hébert, Vivian Salino
Abstract: This paper discusses the calculation of the IAEA benchmark entitled In-core fuel management code package validation for WWERs (IAEA-TECDOC-847) with the Version5 code system (DRAGON and DONJON). Calculations were performed for VVER-1000 cores. Cell calculations are done with DRAGON. Core calculations are done with DONJON, using CLE-2000 procedures to determine the reactor state at each depletion step, taking into account the control rod insertion pattern, reactor power, coolant inlet temperature and coolant mass flow. A multi-variate cross-section database for the core calculations is made with DRAGON. Calculated results are the critical boron concentration at each depletion step, and axial and radial power profiles at a few depletion steps. The present work serves as a feasibility study for the application of DRAGON and DONJON to VVER cores, and results are generally acceptable. Suggestions are made to improve the quality of the simulations.
Keywords: DRAGON; DONJON; VVER-1000; VVER lattice calculation; VVER core calculation; VVER core follow simulation; VVER core analysis; IAEA VVER benchmark; Rooppur nuclear power plant.
Study of gamma/X-ray interaction in some diodes and transistors
by H.C. Manjunatha, L. Seenappa, K.N.. Sridhar, Chikka Hanumantharayappa
Abstract: We have studied the gamma radiation effects by computing the parameters such as mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half value layer (HVL), tenth value layer (TVL) and electric conductivity for different types of diodes and transistors, such as small outline transistor. Among the all studied diodes, the diode DO-41 is less sensitive and the diode SOT-323 single diode is more sensitive to gamma radiation compared to other studied diodes. Among the all studied transistors, the transistor TO-220 is less sensitive and the transistor SOT-323 is more sensitive to gamma radiation compared to other studied transistors. The conductivities of transistor and diodes are not constant when they are exposed to high gamma dose. The conductivity varies with the energy of gamma radiation. This work is useful in the selection of electronic equipment in the fields of aerospace, nuclear reactor and weapons communities and particle accelerators.
Keywords: gamma/X-ray; diode; transistor.