International Journal of Nuclear Energy Science and Technology (7 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.
Differential probabilistic space-temporal model for real-time power prognosis in failures in a nuclear reactor
by Alejandro Nuñez-Carrera
Abstract: The aim of this paper is the neutronic flux prognosis in a nuclear reactor for faults in the measurement of local power reactor monitors (LPRMs) in real time using a differential probabilistic space-temporal model (DPSTM). The LPRMs do provide inputs to the average power range monitor (APRM). The LPRM house a fission chamber and their associated signal cables. The failure of one or more chains of LPRMs is common during the operational cycle. The circuit average only LPRM signals that are operational and the output from the averaging circuit for each APRM channel is the route to the process computer. The DPSTM allows a reliable reconstruction of the real time signals of those LPRMs that are out of order. The DPSTM is evaluated in terms of predictive accuracy for different time horizons and compared to a time series. The DPSTM based prognosis methodology was developed and validated with real signals of Ringhals stability benchmarks.
Keywords: BWR; LPRM; APRM; Ringhals NPP; Bayesian network; neutron flux; spatial-temporal model; Markov random; prognosis process; real time.
Proton-induced spallation of mercury and xenon targets for neutron flux produced between CEM03.01 and INCL4-ABLA spallation packages
by Abdessamad Didi, Hassane Dekhissi
Abstract: Accelerator-driven subcritical reactors (ADS) are one of the pathways considered for the incineration of minor actinides. They use a proton beam accelerator up to a GeV energy, bombarding a spallation target, usually made of a material of high atomic number (W, Pb, Ta or U). The neutrons generated during the spallation reactions are then multiplied. The main goal of this study is to make a comparison between two models of physical packages via the Monte Carlo code MCNP6. The first package is the INCL4-ABLA and the second one is the CEM03.01. We have deduced the best package according to the neutron production rate. In this study, we are interested in two cylindrical targets of natural mercury and xenon, 20 cm in height and 20 cm in diameter, and a proton beam varying from 0.1 to 1.5 GeV.
Keywords: spallation; neutron flux; yield neutron; accelerator; high energy; MCNP.
Enhanced calculations of fusion barrier distribution for heavy-ion fusion reactions using the Wong Ffrmula
by Fouad A. Majeed, Fatima M. Hussain, Yousif A. Abdul-Hussien
Abstract: The effect of coupled channels in heavy ion fusion reaction for the systems 40Ca + 192Os, 40Ca + 194Pt, and 48Ca + 197Au are discussed. The fusion cross-section, σ_fus, the fusion barrier distribution, D_fus, and fusion probability P_fus are investigated. The fusion barrier distribution is calculated using numerical three point, five point and Wong methods. Full quantum coupled channels calculations are performed using CCFULL code with all order coupling to compare with available experimental data. The χ^2 values for the cases of no coupling and coupling effects included shows clearly that the present calculations are in good agreement with the experimental data.
Keywords: Wong formula; coupled channel; CCFULL code; heavy ion fusion.
Small modular reactor core neutronic evaluation via Monte Carlo method
by Reza Akbari, Dariush Rezaei Ochbelagh, Ahmad Gharib
Abstract: The Small Modular Reactors (SMRs) have been getting a lot of positive attention recently, because of their features such as lower initial costs, better safety features than older power reactors, district heating, co-generation, energy storage, desalination, and hydrogen production. Most of the SMRs are in their different design stages, so demonstrating the differences and similarities of the different aspects (economic, safety, neutronic, etc.) of these new integral reactors in comparison to the conventional large reactors is valuable and useful in the design procedure. The main purpose of this study is an evaluation of the SMART reactor core (an SMR with certified design) neutronic parameters via the Monte Carlo method using the MCNPX code. The SMART neutronic parameters, such as axial and radial distributions of neutron fluxes, Power Peaking Factors (PPFs), effective delayed neutron fraction, xenon and samarium effects, burnup calculation and neutron flux energy spectrum, have been assessed. Daily load following operation in soluble-boron-free with control regulating banks is one of the best SMART reactor core advantages. Accordingly, the effects of main regulating bank insertion in SMART core have been evaluated. For developed model verification, some of the neutronic parameters have been compared with the SMART Standard Safety Analysis (SSAR) and show proper match. Then other neutronic parameters of the SMART core as a pioneer SMR have been calculated and evaluated.
Keywords: small modular reactor; SMART; neutronic assessment; Monte Carlo method.
Study of the nuclear structure of 58,62Ni isotopes using the F5PVH effective interaction
by Khalid Jassim, Aqel I. Faris
Abstract: The nuclear structure of 58,62Ni nuclei has been calculated using F5PVH as an effective interaction for 1f5/2 2p3/2 2p1/2 shell model wavefunctions. Skyrme-Hartree Fock (SKX), Harmonic Oscillator (HO) and Woods-Saxon (WS) potentials were used to calculate the single particle wavefunction. The core-polarisation effects have been adopted using the shape of Tassie model. The level schemes are compared with the experimental data up to 3.42 MeV and 4.018 MeV for 58Ni and 62Ni, respectively. In this study, very good agreements are obtained for all nuclei. Results from C2 form factor and charge density distribution calculations give good agreement with the experimental data with no adjustable parameters.
Keywords: shell model; electron scattering; elastic and inelastic scattering.
Reactivity worth calculation for control rod groups of the VVER-1000 nuclear reactor considering shadowing effect using Monte Carlo method
by Zahra Tabadar, GholamReza Ansarifar, Kamal Hadad, Masoud Jabbari
Abstract: Global core calculations use the diffusion equation to predict theoretically the nuclear reactor behaviour. However, this equation is not valid in strong absorbing media where the neutron spectrum is a rapidly varying function of the position, such as control rods or burnable poisons. In this paper, to overcome this difficulty, the Monte Carlo simulation has been performed and the VVER-1000 reactor core in the MCL (Reactor Minimally Controlled Power Level) condition is modelled using the MCNPX2.6 code to calculate the reactivity worth of the control rod groups. The calculations in this model are divided in to four steps. At first, the integral and differential worth is calculated for control groups 8, 9 and 10 with 50% overlapping, and the shadowing effect is considered. In the other three steps the integral and differential reactivity worth of control groups 8, 9 and 10 is calculated separately (without overlapping). In each step, the core is maintained critical by variation of the boron concentration. In these processes the boric acid coefficient is achieved while the core is critical. The results are compared with experimental values that the maximum relative error for differential worth of control rods groups with considering the shadowing effect is 17.8% and for integral worth is 16.7%. The results show good agreement with experimental values.
Keywords: control rod group; VVER-1000 nuclear reactor; Monte Carlo; reactivity worth calculation; MCNPX2.6 code; shadowing effect.