International Journal of Nuclear Energy Science and Technology (8 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.
Study of Grodzins product in collective nuclear structure
by Harish Mohan Mittal, Amit Bindra
Abstract: Systematic dependence of Grodzins product 〖E(2〗_1^+)*B(E2)↑ on the nucleonic promiscuity factor, i.e. P-factor = (NpNn)/(Np+Nn), is studied in the Z = 50-82 N = 82-126 major shell space. The anomalous behaviour is noticed for N = 88-90, where the Grodzins product 〖E(2〗_1^+)*B(E2)↑ fails to maintain the constancy corresponding to P≥4. The P≥4 is recognised for enhanced collectivity, where p-n interaction of the order of ~250 keV begins to dominate the pairing interaction of ~1 MeV. The P-factor also resolves the anomaly of not obtaining a smooth universal Casten curve in NpNn scheme. The approximate constancy in Grodzins product 〖E(2〗_1^+)*B(E2)↑ is noticed for well deformed nuclear region. We have studied, for the first time, the relation between Grodzins product 〖E(2〗_1^+)*B(E2)↑ and the P-factor.
Keywords: Grodzins product; nuclear structure; P-factor.
Surface diffuseness parameter with quasi-elastic scattering for some heavy-ion systems
by Qasim J. Tarbool, Khalid S. Jassim, Ali Abojassim
Abstract: Itemised studies of the surface properties of the inter-nucleus potential in heavy-ion reactions have been achieved using large-angle quasi-elastic scattering at sub-barrier energies close to the Coulomb barrier height for (_3^6)Li +(_30^64)Zn and (_3^7)Li + (_30^64)Zn systems. In this piper, the nuclear potentials have been expressed using the Woods-Saxon (WS) formula. The effect of rotational deformation was included for the nucleus (_30^64)Zn with ground state rotational band up to the 4+ states. The single-channel (SC) and coupled-channels (CC) calculations have been carried out to elicit the diffuseness parameter of the nuclear potential as well as the potential depth. These calculations have been performed by using (CQEL) program, which is considered the latest version of computer code (CCFULL). The chi square method χ2 played an important role in determining the best fitted value of the diffuseness parameter. Through CC calculations with inert projectile and rotational target for (_3^6)Li + (_30^64)Zn and (_3^7)Li + (_30^64)Zn systems, we got full compatibility of diffuseness parameter with the standard value 0.63 fm with χ2 = 0.130 and χ2 = 0.163, respectively, while the SC calculations give 0.64 fm and 0.65 fm, respectively.
Keywords: coupled-channels calculations; heavy-ion fusion reactions; deep sub-barrier energies; quasi-elastic scattering; Woods-Saxon potential.
New study of various target neutron yields from spallation reactions using a high-proton beam energy
by Abdessamad Didi, Ahmed Dadouch, Mohamed Bencheikh, Otman Jai, Otman El Hajjaji
Abstract: The spallation target plays an important role in the construction of an accelerator-driven system. Its purpose is to generate a neutron flux produced by cascaded spallation reactions using heavy nuclei, the latter being bombarded by a high-intensity proton beam. In this study, we have examined several heavy materials, including uranium, thorium, tungsten, tantalum, lead, bismuth and mercury. The aim of this is to optimise a high-intensity neutron flux to be useful in several fields of applications, such as medicine and transmutation of nuclear waste. In this paper, we have shown when the spallation target changes as the neutron flux varies. For example, uranium and thorium produce a very intense amount of neutrons followed by lead, tungsten, mercury and bismuth and lastly tantalum. We found these results by the variation of the proton beam energy from 0.1 GeV to 3 GeV, then with the variation of the geometry. Finally, we validated this study with experimental and theoretical results.
Keywords: spallation; transmutation; Monte Carlo; MCNP; heavy materials; yield neutron; accelerator-driven system.
On the potential of water desalination as a proxy for energy storage systems in nuclear power plants
by Bassam Khuwaileh, Ahmed Ishag
Abstract: Nuclear energy is a promising source of power, proven viable in the cogeneration of electricity and water alike. However, a major challenge for (but not limited to) nuclear power generation is the maximisation of the power plant efficiency. Operating power plants with high to maximum efficiency has a profound effect on energy prices and environmental conditions for obvious reasons. One proposed strategy is to use energy storage systems for later discharge of power. However, this option entails transmission losses and a considerable capital cost. Therefore, this work explores the potential of water desalination as a proxy for energy storage systems in nuclear power plants. The current work explores various water desalination technologies and compares their performance in terms of the economics, water quality and production capacity. Three case studies have been adapted, including APR1400, SMART and NuScale technologies. On the desalination side, Reverse Osmosis (RO), Multi-Stage Flash (MSF), Multi-Effect Distillation (MED) and hybrid combinations were studied. Results indicate that various desalination techniques can replace energy storage systems with justifiable capital cost and yet provide fresh water with acceptable quality. Specifically, RO can use the excess power produced via nuclear reactors during low demand periods with relatively low costs, without introducing new radiation release pathways.
Keywords: water desalination; nuclear power; energy storage systems.
Improving of phenomenological formula for nuclear energy decay (Q-value) of heavy and super-heavy nuclei
by Firas Al-Jomaily, Hala Hadi
Abstract: The phenomenological formula of Qα-values (alpha decay energies) for heavy and super-heavy nuclei is presented using a modification of a liquid drop model, which is composed of effects of volume energy, Coulomb energy, symmetry energy and binding energy of alpha particles. It can be employed to validate the experimental observations and calculations to a large extent of heaviest nuclei with high accuracy for root mean square deviation (0.54) and standard deviation (0.38), which are useful for future experiments. In the comparison of computed Qα-values with experimental data an excellent agreement has been obtained. These results indicate the acceptability of the approach. Furthermore, the theoretical quantity (S) has been proposed in order to predict the Qα-value of alpha particles. This is done by partial differentiation of both sides of Qα-value with respect to the mass number (A), this quantity describes the Qα-value dependence of A. These results show agreement between the behaviour of S and Qα-values. The separation energy difference (Sp-Sn) increases with increasing mass number, on the whole.
Keywords: Qα-value; alpha decay; super-heavy nuclei; liquid drop model.
Searching for the optimum number of integral burnable absorber rods used in PWR assembly
by Ahmed Galahom
Abstract: This article discusses the effect of different integral burnable absorber numbers (IBAs) on the neutronic characteristics of a Pressurized Water Reactor (PWR) to provide a suitable safety level. MCNPX code version 2.6 was used to design a three-dimensional model for PWR assembly. The designed model has been validated by comparing the output values of the infinity multiplication factor (Kinf) with a previously published value. The designed MCNPX model was used to analyse the radial distribution of thermal neutrons and the power through the PWR assembly with and without IBA. Owing to the high absorbtion cross-section of gadolinium, it has been used as a burnable absorber material in the IBA rods. The gadolinium suppressed the power in the regions where it was distributed. The existence of IBA rods has a large effect on the Kinf. This effect decreases gradually with burnup owing to the degradation of gadolinium. The gadolinium isotopes' degradation was analysed with burnup. Different numbers of IBA rods were investigated to optimise the suitable number that can be used in the PWR assembly. The reactivity has been investigated for different numbers of IBAs. The gadolinium effect on the concentration of 135Xe and 149Sm resulting from the fission process was analysed.
Keywords: PWR; IBAs; MCNPX code; gadolinium 2O3.
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.