The dissolved oxygen in a coolant can affect the oxidation properties of structural materials. A desirable oxide phase formation is achieved by manipulating the oxygen level in the coolant, which can mitigate structural material degradation in nuclear power plants. Therefore, the role of dissolved oxygen in the corrosion of structural materials in aqueous environments needs to be understood. In this study, a short-term corrosion test (up to 300 h) of Ferritic/Martensitic steels (F/M steels; FeCrW model alloys), namely, Fe12Cr1W, Fe9Cr1W, and Fe9Cr, in stagnant water at 360 °C was performed in a pressurized autoclave with the dissolved oxygen concentration controlled to 1 ppm or a very low level (<1 ppm). The results of the corrosion tests showed that an increase in the oxygen level in the water elevated the corrosion potential, allowing the phase transition of iron oxide from magnetite (Fe3O4) to hematite (Fe2O3), whereas there was no significant correlation between the concentrations of the alloying elements Cr and W and the oxide growth rate. In addition, hematite was found to mitigate further oxide growth. Finally, a mechanism for the growth of the initial oxide layer was proposed based on the experimental results.
This research aims to investigate the application of the hot pressing (HP) sintering process in the fabrication of W-B-Fe-Cr-C advanced shielding materials and analyze the relationship between their microstructure and mechanical properties. The findings reveal that the HP sintering process can effectively produce reactive sintered boride (RSB) materials with high density and engineering application size. The results indicate that the residual stress in RSB-HP improves its bending strength to some extent. Residual stress and granular structure are both related to phase aggregation during sintering. Microstructural analysis has unveiled the granular organizational characteristics and the pathways of crack propagation within the RSB-HP. These discoveries hold significant importance for comprehending the potential of the HP sintering process in the context of nuclear fusion shielding material preparation and provide a scientific foundation for further optimizing the sintering process and performance of RSB materials.
Sharmin Jahan, Jannatul Ferdous, Md Mahidul Haque Prodhan
et al.
Handling of radioisotopes may cause external and internal contamination to occupational workers while using radiation for medical purposes. This research aims to monitor the internal hazard of occupational workers who handle 131I. Two methods are used: in vivo or direct method and in vitro or indirect method. The in vivo or direct method was performed by assessing thyroid intake with a thyroid uptake monitoring machine. The in vitro or indirect method was performed by assessing urine samples with the help of a gamma-ray spectroscopy practice using a High-Purity Germanium (HPGe) Detector. In this study, fifty-nine thyroid counts and fifty-nine urine samples were collected from seven occupational workers who were in charge of 131I at the National Institute of Nuclear Medicine and Allied Sciences (NINMAS), Dhaka. The result showed that the average annual effective dose of seven workforces from thyroid counts were 0.0208 mSv/y, 0.0180 mSv/y, 0.0135 mSv/y, 0.0169 m Sv/y, 0.0072 mSv/y, 0.0181 mSv/y, 0.0164 mSv/y and in urine samples 0.0832 mSv/y, 0.0770 mSv/y, 0.0732 mSv/y, 0.0693 mSv/y, 0.0715 mSv/y, 0.0662 mSv/y, 0.0708 mSv/y.The total annual effective dose (in vivo and in vitro method) was found among seven workers in average 0.1039 mSv/y, 0.0950 mSv/y, 0.0868 mSv/y, 0.0862 mSv/y, 0.0787 mSv/y, 0.0843 mSv/y, 0.0872 mSv/y. Following the rules of the International Commission on Radiological Protection (ICRP), the annual limit of effective dose for occupational exposure is 20 mSv per year and the finding values from this research work are lesser than this safety boundary.
The critical rod position search has been one of the issues in the Monte Carlo (MC) reactor analysis. This paper proposes a practical and simple approach for the critical rod position search based on the neutron balance equation and the monotonic relation between the control rod absorption rate and the total rod insertion length. The proposed method was implemented in an inline manner within the McCARD, the MC reactor design code, so that the critical rod position is calculated and updated for each fission source iteration. The numerical results in a typical fast reactor problem demonstrate the promising performance of the proposed method in the critical rod position search calculation. Furthermore, the cycle depletion calculation was performed to show the capability of the McCARD to simulate the rodded operation condition. By addressing the critical rod position search problem through the neutron balance approach, the applicability of the MC code in the advanced reactor design will be expanded.
Recent calculations of the lithium vapor box divertor using SOLPS have demonstrated that far Scrape-Off Layer (SOL) baffling and the corresponding far SOL lithium evaporation are unnecessary for divertor performance. The plasma, acting as a virtual baffle, is sufficient to block the neutral lithium from escaping the divertor region in a configuration known as the lithium vapor “cave.” Here, extensions of this PFC design simplification are presented which show that significantly less obtrusive PFCs can provide similar divertor performance. Differences in upstream concentration are predicted depending on the depth and size of the lithium emitting aperture, the shape of the private flux region (PFR) structure, and the location within the PFR of the deuterium puff. SOLPS predictions for (nLi/ne)LCFS vary between 0.020 and 0.049. For the first time, the effect of E×B drifts on predictions for a lithium vapor box divertor is also examined, with the resulting solutions having lower inner divertor heat flux but higher outer divertor heat flux for a given lithium evaporation rate. The differences between the PFC designs are minimized with drifts enabled, indicating design flexibility. The increased PFC design flexibility reported here, along with improved SOLPS modeling with drifts, are important steps towards a final design.
The mechanics underlying photon and electron interactions was validated using our developed Brachytherapy computer code for high Dose Rate (HDR). By comparing the photon cross-section utilizing multiple physics libraries in the developed code, the results were benchmarked against experimental and theoretical findings. Klein-Nishina and experimental cross-section results were in good agreement with the Livermore library results. For two therapeutically relevant materials, the first scattered electron range was measured within 1 mm and 2 mm, which has significant implications for the interpretation of the kernel dose spikes observed in previous research.
In light of current global issues concerning the depletion of non-renewable energy sources and degradation of our atmosphere, there has been an increased interest in the topic of nuclear fusion. Fusion, a process that was discovered in the early 20th century, began development internationally in the 1930s, and continues to be studied today. As the nature of the atomic nucleus was being explored, it was hypothesized early on that fusion was the process behind the power generated by the sun and stars. This quickly led to the idea of harnessing that power, but it seemed as if the problems would not be overcome. Within the past 20 years, the intensity of fusion research has increased as a result of the growing sustainable energy problem the Earth faces. There are a number of practical engineering problems that implementing functional fusion reactors face. Two of the most daunting have been creating strong enough magnetic fields and maintaining the necessary conditions of temperature, pressure, density for a long enough period of time to generate sufficient amounts of energy to be competitive with current power plants. In addition, politically fusion has often been conflated with an anti-nuclear (bomb and fission) movement. Due to the frequent comparisons between the two, there may be stigma against the construction of fusion reactors. As the climate and energy crisis have changed public thinking, however, it is possible that the public opinion has changed. There are a number of important positive aspects to exploiting nuclear fusion. It does not produce greenhouse gasses. It has an abundant supply of initial fuel (which are isotopes of hydrogen). It does not generate dangerous radioactive waste. And unlike wind and solar power it is not an intermittent source of energy and can be integrated more easily into the existing power distribution grid.One aspect of this work is to assess what people know and are interested in learning about nuclear fusion. Another is to introduce and explain current efforts to develop fusion reactors on a global scale. A survey has been developed to assess attitudes towards nuclear fusion. In particular, the survey is being distributed to high school students as they will be the important future decision makers about sources of energy. We also looked at some global data of the distribution and development of energy sources, which show that developed countries are not necessarily changing their power sources, but new sources may be more likely to be implemented in other parts of the world. The effort for a sustainable fusion reaction remains very much an international effort. This poster serves to illustrate the background and general process of modern nuclear fusion reactors, as well as dissect the benefits (both numerical and psychological) and roadblocks our planet faces to integrate fusion into our energy grid. From these factors we determine that the benefits to fusion are far beyond the problems that serve as walls towards its implementation.
Eman Ismail Gheriany, Osama Ahmed Abbas, Emad Mohamed EL-Sherbiny
The acquisition of new nanomaterials with unique properties for biomedical application is an essential requirement and many nanoparticles are being studied to test their possible application in therapy. The present study aimed to evaluate the effect of nano-cerium/hydroxyapatite (nCe/HAp) as a regenerative agent for the juvenile hormones and the improvement of dyslipidemia in adult and aged rats. This study included two main groups of albino male rats (adult and aged), each of sixteen rats. Each group was divided equally into two subgroups, control and treated. Treated rats were injected intravenously with 75 mg/kg b. w. nCe/HAp weekly for four weeks. At the end of the experiment, the blood samples were collected between 12:00 and 1:00 (mid-dark) for biochemical analysis. The measurements of dehydroepianrsterone, dehydroepianrsterone sulphate, melatonin, and testosterone hormones were performed as well as lipid profile was analyzed. The obtained results revealed that nCe/HAp has a pronounced positive effect on juvenile hormones value and lipid profile status in adults more than in aged rats. Based on the experimental results, it can be established that nCe/HAp has a potential effect on improving the level of juvenile hormones in adult and aged rats. Therefore, it may candidate nCe/HAp composite as a regenerative drug in the event of hormonal imbalance resulting from dysfunction or aging in the future.
Medical physics. Medical radiology. Nuclear medicine, Nuclear engineering. Atomic power
Dong-Hun Shin, Hae-Yong Jeong, Moon-Ghu Park
et al.
A combined safety approach, which uses a best-estimate computer code and adopts conservative assumptions for safety systems availability, is developed and applied to the safety margin evaluation for the Loss of Condenser Vacuum (LOCV) of the 1000 MWe Korean Nuclear Power Plant. The Multi-dimensional Analysis of Reactor Safety-KINS standard (MARS-KS) code is selected as a best-estimate code and the PAPIRUS program is used to obtain different initial operational conditions through random sampling of control variables. During an LOCV event, fuel integrity is not threatened by the increase in Departure from Nuclear Boiling Ratio (DNBR). However, the high pressure in the primary coolant system and the secondary system might affect the system integrity. Thus, the peak pressure becomes a major safety concern. Transient analyses are performed for 124 cases of different initial conditions and the most conservative case, which results in the highest system pressure is selected. It is found the suggested methodology gives similar peak pressures when compared to those predicted from existing methodologies. The proposed approach is expected to minimize the time and efforts required to identify the conservative plant conditions in the existing conservative safety methodologies.
Many probes are proposed to determine the quark-gluon plasma and explore its properties in ultra-relativistic heavy-ion collisions. Some of them are related to initial states of the collisions, such as collective flow, Hanbury-Brown-Twiss (HBT) correlation, chiral magnetic effects and so on. The initial states can come from geometry overlap of the colliding nuclei, fluctuations or nuclear structure with the intrinsic geometry asymmetry. The initial geometry asymmetry can transfer to the final momentum distribution in the aspect of hydrodynamics during the evolution of the fireball. Different from traditional methods for nuclear structure study, the ultra-relativistic heavy-ion collisions could provide a potential platform to investigate nuclear structures with the help of the final-state observables after the fireball expansion. This chapter first presents a brief introduction of the initial states in relativistic heavy-ion collisions, and then delivers a mini-review for the nuclear structure effects on experimental observables in the relativistic energy domain.
In the 75 years since the end of World War II there is still no agreement on the answer to the question of why the presumed race between the USA and Nazi-Germany to build the atomic bomb did not take place. New insights and answers are derived from a detailed analysis of the most important document on the subject, the official report of a German army ordnance dated February 1942. This authoritative document has so far not been adequately analyzed. It has been overlooked, particularly that the goal of the Uranium Project was the demonstration of a self-sustaining chain reaction as a precondition for any future work on power reactors and an atomic bomb. This paper explores why Werner Heisenberg and his colleagues did not meet this goal and what prevented a bomb development program. Further evidence is derived from the research reports of the Uranium Project and from the Farm Hall transcripts. Additional conclusions can be drawn from the omission of experiments, which could have been possible and would have been mandatory if the atomic bomb would have been the aim of the program. Special consideration is given to the role of Heisenberg in the Uranium Project.
Yoshihiko SHINODA1,2,3,, Shouji TSUCHIDA4 and Hiroshi KIMURA5 1Wakasa Wan Energy Research Center, 64521 Nagatani, Tsuruga-shi, Fukui 9140192, Japan 2Nuclear Power and Energy Safety Engineering, University of Fukui, 391 Bunkyo, Fukui, Fukui 9108507, Japan 3Japan Atomic Energy Agency Tsuruga Head O‹ce, 6520 Kizaki, Tsuruga, Fukui 9148585, Japan 4Graduate School and Faculty of Safety Science, Kansai University, 71 Hakubai-cho Takatsuki-shi, Osaka 5691098, Japan 5Public Outreach, NPO, 1111 Nedsu, Bunkyou-ku, Tokyo 1130031, Japan (Received November 14, 2013; accepted in revised form April 30, 2014; published online July 10, 2014)
ι-Carrageenan is a biodegradable and biocompatible biomaterial which potentially stabilizes colloidal silver nanoparticles (AgNPs). The present study explored gamma radiosynthesis of AgNPs at varied concentration of ι-carrageenan solutions. The reaction system contained 1.0 mM silver precursor from silver nitrate salt. Gamma irradiation was conducted at doses up to 20 kGy under simple condition, i.e., atmospheric gases and without addition of hydroxyl radical scavenger. The behavior of AgNPs in suspension was characterized based on their surface plasmon resonance (SPR) absorption spectra which were measured using UV-vis spectrophotometer. The results show that colloidal AgNPs were successfully radiosynthesized due to dual stabilizing/reducing activity of ι-carrageenan. The degradation product of ι-carrageenan shows antioxidant activities, which increase the reducing condition of the reaction system. TEM micrograph reveals that the nanoparticles are spheroid in shape and monodisperse with an average particle size of below 10 nm. The SPR spectra indicate that the highest AgNPs concentration is found for irradiation at a dose of 10 kGy and ι-carrageenan concentration of 1.0 % (w/v). However, instability of AgNPs occurred a day after radiosynthesis due to oxidative dissolution and agglomeration. Further works on pH adjustment and optimization on irradiation dose and ι-carrageenan concentration are critical to improve the stability of colloidal AgNPs.
Multigroup cross section (MG XS) generation by the UNIST in-house Monte Carlo (MC) code MCS for fast reactor analysis using nodal diffusion codes is reported. The feasibility of the approach is quantified for two sodium fast reactors (SFRs) specified in the OECD/NEA SFR benchmark: a 1000 MWth metal-fueled SFR (MET-1000) and a 3600 MWth oxide-fueled SFR (MOX-3600). The accuracy of a few-group XSs generated by MCS is verified using another MC code, Serpent 2. The neutronic steady-state whole-core problem is analyzed using MCS/RAST-K with a 24-group XS set. Various core parameters of interest (core keff, power profiles, and reactivity feedback coefficients) are obtained using both MCS/RAST-K and MCS. A code-to-code comparison indicates excellent agreement between the nodal diffusion solution and stochastic solution; the error in the core keff is less than 110 pcm, the root-mean-square error of the power profiles is within 1.0%, and the error of the reactivity feedback coefficients is within three standard deviations. Furthermore, using the super-homogenization-corrected XSs improves the prediction accuracy of the control rod worth and power profiles with all rods in. Therefore, the results demonstrate that employing the MCS MG XSs for the nodal diffusion code is feasible for high-fidelity analyses of fast reactors.
Several reasons such as no free lunch theorem indicate that there is not a universal Feature selection (FS) technique that outperforms other ones. Moreover, some approaches such as using synthetic dataset, in presence of large number of FS techniques, are very tedious and time consuming task. In this study to tackle the issue of dependency of estimation accuracy on the selected FS technique, a methodology based on the heterogeneous ensemble is proposed. The performance of the major learning algorithms of neural network (i.e. the FFNN-BR, the FFNN-LM) in combination with the diverse FS techniques (i.e. the NCA, the F-test, the Kendall's tau, the Pearson, the Spearman, and the Relief) and different combination techniques of the heterogeneous ensemble (i.e. the Min, the Median, the Arithmetic mean, and the Geometric mean) are considered. The target parameters/transients of Bushehr nuclear power plant (BNPP) are examined as the case study. The results show that the Min combination technique gives the more accurate estimation. Therefore, if the number of FS techniques is m and the number of learning algorithms is n, by the heterogeneous ensemble, the search space for acceptable estimation of the target parameters may be reduced from n × m to n × 1. The proposed methodology gives a simple and practical approach for more reliable and more accurate estimation of the target parameters compared to the methods such as the use of synthetic dataset or trial and error methods.
For a long time, research into integrated deterministic-probabilistic safety assessment has been continuously conducted to point out and overcome the limitations of classical ET (event tree)/FT (fault tree) based PSA (probabilistic safety assessment). The current paper also attempts to assert the reason why a technical transformation from classical PSA is necessary with a re-interpretation of the categories of risk. In this study, residual risk was classified into interpolating- and extrapolating-censored categories, which represent risks that are difficult to identify through an interpolation or extrapolation of representative scenarios due to potential nonlinearity between hardware and human behaviors intertwined in time and space. The authors hypothesize that such risk can be dealt with only if the classical ETs/FTs are freely relocated, entailing large-scale computation associated with physical models. The functional elements that are favorable to find residual risk were inferred from previous studies. The authors then introduce their under-development enabling techniques, namely DICE (Dynamic Integrated Consequence Evaluation) and DeBATE (Deep learning–Based Accident Trend Estimation). This work can be considered as a preliminary initiative to find the bridging points between deterministic and probabilistic assessments on the pillars of big data technology.