•An extensive literature survey on inverted flow regime is carried out.•Existing interfacial heat transfer correlations interfacial frictional drag models were reviewed.•The inverted annular flow ...correlations utilized in modern reactor safety analysis codes are reviewed.
Understanding the inverted annular flow (IAF) boiling regime is crucial for various engineering disciplines. The IAF is a post-dryout, or post-CHF film boiling regime in forced convective flow in tubes or channels. The flow structure of the IAF is characterized by the liquid core present in the channel center, which is separated from the surrounding heating source by a vapor film envelope. It has been studied extensively as one of the film boiling regimes since 1950s. In the core reflooding phase of the light water reactors, in the event of the loss-of-coolant-accident (LOCA), one of the dominant heat transfer modes is film boiling. During that process, various flow regimes are generated in the flow channel, including the IAF. The IAF appears immediately downstream of the pre-CHF flow regime and initiates at the quench front. It gradually progresses to an inverted slug and dispersed flow as it travels downstream. For the improved safety of engineering systems, including modern and advanced nuclear reactors, proper utilization of heat transfer and drag coefficients of IAF for the postulated LOCA is crucial. The present study extensively reviews the existing correlations proposed for IAF heat transfer and drag. In addition, the flow regime transition criteria applicable for IAF, based on the liquid jet-breakup concept, are reviewed. IAF correlations utilized in modern reactor safety analysis codes will also be revisited.
•Modelling of thermal conductivity and melting temperature of minor actinide-MOX fuels.•Review of state-of-the-art data and correlations available in literature or in codes.•Inclusion of the effect ...of the homogeneous minor actinides Am and Np.•Separate-effect assessment against literature data, experimental and MD-calculated.•Integral application to the performance of a fast reactor, MA-MOX fuel pin.
Recycling and burning minor actinides (MA, e.g., americium, neptunium) in mixed-oxide (MOX) nuclear fuel is a strategic option for fast reactor concepts of Generation IV, especially considering the current interest in the ultimate radioactive waste management and sustainability improvement by better use of natural resources. Among the fuel properties, thermal conductivity and melting temperature are pivotal since they determine, respectively, the fuel temperature profile and the fundamental safety limit on the margin to fuel melting, hence impacting on the overall fuel performance under irradiation and allowing the safe irradiation of the fuel pin. Nevertheless, the available literature about Am- or Np-containing MOX is currently scarce, both regarding experimental data and models. Moreover, state-of-the-art fuel performance codes (FPCs, e.g., TRANSURANUS) do not account for the effects of minor actinides on MOX fuel properties. This work presents original correlations for thermal conductivity and melting temperature of minor actinide-MOX fuels, i.e., (U, Pu, Am, Np)O2-x, derived based on the available literature and accessible data, which are herein extensively reviewed. The assessment of the novel correlations is first performed in a statistical way, evaluating the regressor p-values which indicate their significance with respect to the available experimental dataset used for the fitting procedure. Additionally, the novel correlations for MA-MOX are assessed against both measured and calculated data (from Molecular Dynamics simulations), yielding an accuracy in line with the already existing correlations and with the state-of-the-art experimental uncertainties. Finally, the potential integral impact of a homogeneous minor actinide content in the fuel is illustrated on the basis of a fuel pin fast-ramped up to fuel melting during the HEDL P-19 irradiation experiment.
This study demonstrates a method for determining the isotopic composition of low-level (sub-pg) plutonium (Pu) directly from a cotton swipe. Environmental sample (ES) swipes are routinely employed as ...a tool for monitoring activities in nuclear facilities. Traditional ES swipe analysis, as employed in nuclear safeguards, utilizes laborious ashing, digestion, and chemical separation procedures prior to mass spectrometric (MS) analysis. Here, an innovative sample introduction technique employing a microextraction probe to extract Pu directly from the swipe surface is described. The microextraction probe lowers onto the swipe surface, seals on a small area (8 mm
2
), and delivers solvent (2% HNO
3
) to extract actinide material that may be present. The extracted analyte is subsequently directed into a sector field inductively coupled plasma (ICP)-MS for isotope ratio determination. This microextraction-ICP-MS method successfully determined the isotopic composition (
240
Pu/
239
Pu and
242
Pu/
239
Pu) of three Pu certified reference materials (CRM 136, 137, and 138) that were deposited (1 pg) onto ES swipes. The percent relative difference from the certified value, uncorrected for instrumental fractionation, was <2% for the
240
Pu/
239
Pu ratio on all three CRMs and <10% for the
242
Pu/
239
Pu ratio on CRM 136 and 138. The percent relative standard deviation, an estimate of the sample-to-sample isotopic precision, was <4% for the
240
Pu/
239
Pu and <15% for the
242
Pu/
239
Pu. Method limits of detection were determined, based on measurements of an enriched
244
Pu material, to be ∼7 fg. Additionally, a mixed uranium (U) and Pu deposition was made to determine the method's ability to simultaneously extract U and Pu and determine the isotopic composition of both analytes.
This study demonstrates a method for determining the isotopic composition of low-level (sub-pg) plutonium (Pu) directly from a cotton swipe.
Rationale
Hesperidin (HES) is a well‐known citrus bioflavonoid phyto‐nutraceutical agent with polypharmacological properties. After 2019, HES was widely used for prophylaxis and COVID‐19 treatment. ...Moreover, it is commonly prescribed for treating varicose veins and other diseases in routine clinical practice. Pharmaceutical impurities and degradation products (DP) impact the drug's quality and safety and thus its effectiveness. Therefore, forced degradation studies help study drug stability, degradation mechanisms, and their DPs. This study was performed because stress stability studies using detailed structural characterization of hesperidin are currently unavailable in the literature.
Methods
In the HES enrichment method crude HES was converted to its pure form (98% purity) using column chromatography and then subjected to forced degradation under acid, base, and neutral hydrolyses followed by oxidative, reductive, photolytic, and thermal stress testing (International Conference on Harmonization guidelines). The stability‐indicating analytical method (SIAM) was developed to determine DPs using reversed‐phase high‐performance liquid chromatography (C18 column with methanol and 0.1% v/v acetic acid in deionized water 70:30, v/v at 284 nm). Further, structural characterization of DPs was performed using liquid chromatography‐electrospray ionization‐tandem mass spectrometry (LC‐ESI‐MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. In addition,
in silico
toxicity predictions were performed using pKCSM and DataWarior freeware.
Results
HES was found to be susceptible to acidic and basic hydrolytic conditions and yielded three DPs in each, which were detected using designed SIAM. Of six DPs, three were pseudo‐DPs (short lived), and the remaining were characterized using LC–MS/MS and NMR spectroscopy. The tentative mechanism of the formation of proposed DPs was explained. The proposed DPs were found inactive from
in silico
toxicity predictions.
Conclusions
Hesperidin was labile under acidic and basic stress conditions. The potential DPs were characterized using LC‐ESI‐MS/MS and NMR spectral techniques. The proposed mechanism of formation was hypothesized. In addition, to identify and characterize the DPs, a SIAM, which has broad biomedical applications, was successfully developed.
Phytosterols and phytostanols are natural products present in vegetable oils, nuts, and seeds, or added to consumer food products whose intake is inversely associated with incidence and prognosis of ...several cancers. Randomized cancer prevention trials in humans are unfeasible due to time and cost yet the cellular processes and signaling cascades that underpin anti-cancer effects of these phytochemicals have been explored extensively in vitro and in preclinical in vivo models. Here we have performed an original systematic review, meta-analysis, and qualitative interpretation of literature published up to June 2020. MEDLINE, Scopus, and hand-searching identified 408 unique records that were screened leading to 32 original articles that had investigated the effects of phytosterols or phytostanols on cancer biology in preclinical models. Data was extracted from 22 publications for meta-analysis. Phytosterols were most commonly studied and found to reduce primary and metastatic tumor burden in all cancer sites evaluated. Expression of pAKT, and markers of metastasis (alkaline phosphatase, matrix metalloproteases, epithelial to mesenchymal transcription factors, lung and brain colonization), angiogenesis (vascular endothelial growth factor, CD31), and proliferation (Ki67, proliferating cell nuclear antigen) were consistently reduced by phytosterol treatment in breast and colorectal cancer. Very high dose treatment (equivalent to 0.2-1 g/kg body weight not easily achievable through diet or supplementation in humans) was associated with adverse events including poor gut health and intestinal adenoma development. Phytosterols and phytostanols are already clinically recommended for cardiovascular disease risk reduction, and represent promising anti-cancer agents that could be delivered in clinic and to the general population at low cost, with a well understood safety profile, and now with a robust understanding of mechanism-of-action.
•Different types of PRHR heat exchangers in NPP were classified and analyzed.•Studies of tube external heat transfer mechanism were reviewed.•Heat transfer correlations and their performances were ...summarized.•Recommendations were provided for future research.
The nuclear power plant (NPP) has been developing for more than 60 years. Since Gen III NPP, the passive safety system has been firstly used to enhance operational safety, develop reliability and performance of the advanced nuclear power plant. There are several types of passive safety systems in existing Gen III NPPs, and the passive residual heat removal (PRHR) heat exchanger is a key facility in passive safety system. This paper mainly focuses on the tube external heat transfer mechanism and correlations study since the existing investigation is not sufficient, especially tube external subcooled boiling heat transfer research of PRHR heat exchanger in Gen III NPPs. The tube external heat transfer mechanism of PRHR heat exchanger is deeply analyzed here, and the empirical correlations proposed in literature are carefully summarized and classified in order to broaden the heat transfer calculation methods.
•Definition of new type 18 operator to enhance the model ability of GO methodology for MC(k,n) system.•Optimization of BN structure corresponding to large-scale MC(k,n) system.•Mapping procedure ...transforming GO model of MC(k,n) system to corresponding BN.•Fault diagnosis and improvement guidance of MC(k,n) system based on extended GO model and BN.
As a success-oriented system reliability and safety analysis technique, GO methodology is widely used in the modeling and analysis scenarios of critical safety engineering systems with signal flow, such as nuclear, chemical industry, electric power transportation, wireless network and microwave communication network. Consecutive-k-out-of-n systems are also widely applied in these fields, but due to their relatively complex logic, there are no corresponding graphical modeling and calculation methods. In this paper, the basic GO methodology is extended to support the modeling and analysis of multi-state linear and circular consecutive-k-out-of-n: F system (MLC(k,n) &MCC(k,n)) models. Two new operators are defined in graphical modeling to represent the two types of complex system logic. The multi-state logic semantics of the new operators and mapping rules to Bayesian networks (BN) are given. And the programmable process is presented to transform the extended GO model into BN, and the reliability of the MLC(k,n)/MCC(k,n) is calculated. Finally, three cases are used to verify i) the correctness of the method supporting multi-state model, ii) the efficiency and ability of the algorithm, and iii) the forward calculation and reverse diagnosis of the MLC(k,n) and MCC(k,n) systems with external shared components.
•Taking into account uncertainties is a key issue in nuclear power plant safety analysis using best estimate plus uncertainty methodologies. The OECD/NEA PREMUM project devoted to input uncertainty ...quantification has shown that inverse methods can exhibit strong user-effect. One of the main reasons was the lack of a clear guidance to perform a reliable analysis. This work is precisely devoted to the development of a first good practice guidance document for quantification of thermal-hydraulic code model input uncertainty.•The good practice guidance is structured following 5 elements that are summarized in the paper. Recommendations and open issues for future developments are also given.•This work emphasized that IUQ is a general process that involves a clear specification of the problem and efficient strategies to construct adequate experimental database. It also requires assessing the simulation model before quantifying input uncertainties. Finally, the validation of the quantified model input uncertainties has to be taken into account in order to check the acceptability of the results for the intended use. This work revealed the need to use mathematical tools integrating the physical knowledge in order to be rigorous, transparent and reproducible.•Even if part of the material to perform model IUQ is available, several remaining open issues should be tackled. This paper includes some development axes for future works. They concern the adequacy analysis of the experimental database, the construction of inverse propagation methods and the evaluation of the acceptability of the results in the validation and application domains.
Taking into account uncertainties is a key issue in nuclear power plant safety analysis using best estimate plus uncertainty methodologies. It involves two main types of treatment depending on the variables of interest: input parameters or system response quantity. The OECD/NEA PREMIUM project devoted to the first type of variables has shown that inverse methods for input uncertainty quantification can exhibit strong user-effect. One of the main reasons was the lack of a clear guidance to perform a reliable analysis. This work is precisely devoted to the development of a first good practice guidance document for quantification of thermal-hydraulic code model input uncertainty. The developments have been done in the framework of the OECD/NEA SAPIUM project (January 2017–September 2019). This paper provides a summary of the main project outcome. Recommendations and open issues for future developments are also given.
The use of molecular oxygen is unquestionably the green path to the selective oxidation of alcohols to aldehyde and ketones. However, this reaction class poses safety problems associated with mixing ...oxygen with organic substrates. Continuous membrane reactors offer an attractive solution, owing to their ability to keep the oxygen phase separated from the liquid substrate, while controlling the dosing of oxygen during reaction. In this work, we demonstrate a slurry loop membrane reactor for continuous oxidations as well as hydrogenations. The catalyst slurry was circulated around a loop, to which a saturator containing a flat Teflon AF-2400 membrane was connected, along with a crossflow filter to keep the catalyst particles within the loop. Under a recycle flowrate 100 times higher than the inlet, the residence time distribution was found to be comparable to that of an ideal CSTR. A remarkably high
k
L
a
of 1.2 s
−1
was achieved under a moderate specific power input of 2.4 kW m
−3
during styrene hydrogenation. Continuous aerobic oxidations of various primary and secondary alcohols were carried out for 6-7 h at 90-120 °C and 2-6 bar, using a 1 wt% Au-Pd/TiO
2
powder catalyst, leading to conversions between 17% and 75%. The reactor could also be operated in batch mode, achieving higher conversions, while scaled-up operations produced aldehyde yields of 0.4-19 g with only 88 mg of catalyst. Overall, the slurry loop membrane reactor provides significant advantages in terms of catalyst usage and process safety for aerobic oxidations.
A loop reactor was designed and employed in the safe oxidation of alcohols using a flat polymeric membrane for controlling oxygen dosing, a circulating catalyst slurry for efficient catalyst usage and an extendable loop volume for higher productivity.
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