• Nuclear Engineering and Technology
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• 제42권3호
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• pp.259-270
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• 2010

New generation nuclear reactors are designed using advanced safety analysis methods. A thorough understanding of different interacting physical phenomena is necessary to avoid underestimation and overestimation of consequences of off-normal transients in the reactor safety analysis results. This feature requires a multiphysics reactor simulation model. In this context, a coupled dynamics model based on a multiphysics formulation is developed indigenously for the transient analysis of large pressurized VVER reactors. Major simplifications are employed in the model by making several assumptions based on the physics of individual phenomenon. Space and time grids are optimized to minimize the computational bulk. The capability of the model is demonstrated by solving a series of international (AER) benchmark problems for VVER reactors. The developed model was used to analyze a number of reactivity transients that are likely to occur in VVER reactors.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.222-232
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• 2024

New modular factory-built methodologies implemented in the construction and industrial plant industries may bring down costs for modular reactors. A factory-built environment brings about benefits such as; improved equipment, tools, quality, shift patterns, training, continuous improvement learning, environmental control, standardisation, parallel working, the use of commercial off shelf equipment and much of the commissioning can be completed before leaving the factory. All these benefits combine to reduce build schedules, increase certainty, reduce risk and make financing easier and cheaper.Currently, the construction and industrial chemical plant industries have implemented successful modular design and construction techniques. Therefore, the objectives of this paper are to understand and analyse the state of the art research in these industries through a systematic literature review. The research can then be assessed and applied to modular reactors.The literature review highlighted analysis methods that may prove to be useful. These include; modularisation decision tools, stakeholder analysis, schedule, supply chain, logistics, module design tools and construction site planning. Applicable research was highlighted for further work exploration for designers to assess, develop and efficiently design their modular reactors.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.1-17
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• 2018

This article reviews the multiscale nature of stress corrosion cracking (SCC) observed by high-resolution characterizations in austenite stainless steels and Ni-base superalloys in light water reactors (including boiling water reactors, pressurized water reactors, and supercritical water reactors) with related opinions. A new statistical summary and comparison of observed degradation phenomena at different length scales is included. The intrinsic causes of this multiscale nature of SCC are discussed based on existing evidence and related opinions, ranging from materials theory to practical processing technologies. Questions of interest are then discussed to improve bottom-up understanding of the intrinsic causes. Last, a multiscale modeling and simulation methodology is proposed as a promising interdisciplinary solution to understand the intrinsic causes of the multiscale nature of SCC in light water reactors, based on a review of related supporting application evidence.

• Environmental Engineering Research
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• 제20권1호
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• pp.65-72
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• 2015

A comparative study on response of a toxic compound thiocyanate ($SCN^-$) was carried out in continuous and fed batch moving bed reactor systems. Both systems had three sequential anaerobic, anoxic and aerobic reactors and operated at same hydraulic retention time. Feed $SCN^-$ was first increased from 600 mg/L to 1,000 mg/L for 3 days (shock 1) and then from 600 to 1,200 mg/L for 3 days (shock 2). In anaerobic continuous reactor, increase of effluent COD (chemical oxygen demand) due to shock load was only 2%, whereas in fed batch reactor it was 14%. In anoxic fed batch reactor recovery was partial in terms of $SCN^-$, phenol, COD and $NO{_3}{^-}$-N and $NO{_2}{^-}$-N removals and in continuous reactor complete recovery was possible. In both systems, inhibition was more significant on aerobic reactors than anaerobic and anoxic reactors. In aerobic reactors ammonia removal efficiency deteriorated and damage was irreversible. Present study showed that fed batch reactors showed higher substrate removal efficiency than continuous reactors during regular operation, but are more susceptible to toxic feed shock load and in nitrifying reactor damage was irreversible.

• Journal of Microbiology and Biotechnology
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• 제16권2호
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• pp.232-239
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• 2006

The microbial activity and bacterial community structure of activated sludge reactors, which treated free cyanide (FC), zinc-complexed cyanide (ZC), or nickel-complexed cyanide (NC), were studied. The three reactors (designated as re-FC, re-ZC, and re-NC) were operated for 50 days with a stepwise decrease of hydraulic retention time. In the re-FC and re-ZC reactors, FC or ZC was almost completely removed, whereas approximately 80-87% of NC was removed in re-NC. This result might be attributed to the high toxicity of nickel released after degradation of NC. In the batch test, the sludges taken from re-FC and re-ZC completely degraded FC, ZC, and NC, whereas the sludge from re-NC degraded only NC. Although re-FC and re-ZC showed similar properties in regard to cyanide degradation, denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA gene of the bacterial communities in the three reactors showed that bacterial community was specifically acclimated to each reactor. We found several bacterial sequences in DGGE bands that showed high similarity to known cyanide-degrading bacteria such as Klebsiella spp., Acidovorax spp., and Achromobacter xylosoxidans. Flocforming microorganism might also be one of the major microorganisms, since many sequences related to Zoogloea, Microbacterium, and phylum TM7 were detected in all the reactors.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1814-1820
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• 2023

Safety classification of systems, structures, and components (SSC) is an essential activity for nuclear reactor design and operation. The current regulatory trend is to require risk-informed safety classification that considers first, the severity, but also the frequency of SSC failures. While safety classification for nuclear power plants is covered in many regulatory and scientific publications, research reactors received less attention. Research reactors are typically of lower power but, at the same time, are less standardized i.e., have more variability in the design, operational modes, and operating conditions. This makes them more challenging when considering safety classification. This work presents the Integrated Risk-Informed Safety Classification (IRISC) procedure which is a novel extension of the IAEA recommended process with dedicated probabilistic treatment of research reactor designs. The article provides the details of probabilistic analysis performed within safety classification process to a degree that is often missing in most literature on the topic. The article presents insight from the implementation of the procedure in the safety classification for the MARIA Research Reactor operated by the National Center for Nuclear Research in Poland.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4465-4471
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• 2023

Hands-on education and training is a key part of fixing and developing technology knowledge and is an inherent part of many engineering and scientific curricula. However, access to large complex training facilities, such as nuclear reactor, could be limited by various factors, such as unavailability of those facilities in the region, high traveling costs or harmonization of the schedules of hands-on E&T with theoretical lectures and with the operational schedule of the facility. To handle the issue, several success stories have been reached with the introduction of the Internet Reactor Labs (IRL). The Internet Reactor Labs can strongly contribute to accessibility of training at research reactors and can contribute to improvements in their utilization. The paper describes the development of the Internet Reactor Lab at the VR-1 reactor of the Czech Technical University in Prague. Contrary to single-purpose IRLs, it presents various modalities of online teaching and training in experimental reactor physics and reactor operation in general as well as outreach activities that have been developed in recent years.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1670-1679
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• 2015

Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH₄⁺-N/m³/d and 0.10-0.21 kg NO₃^--N/m³/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH₄⁺ or NO₃^- loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

• 비파괴검사학회지
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• 제23권5호
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• pp.520-525
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• 2003

Fast Breeder Test Reactor (FBTR) is a 40MW (thermal) / 13.2MW (electrical), Plutonium - Uranium mixed carbide fuelled, sodium cooled, loop type nuclear reactor operating at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam. Its main aim is to generate experience in operation of fast reactors and sodium systems and to serve as an irradiation facility for development of fuels and structural materials fur fast reactors. Nuclear reactors pose difficulties to the NDT techniques used to monitor the conditions of the internal components. Sodium cooled fast breeder reactors have their own typical difficulties in using the NDT techniques. These are due to the need for operation in aggressive environment of nuclear radiation and sodium (molten/vapour), as well as the need to maintain leak tightness of a very high order during all states of reactor operation and shutdown for fuel handling, maintenance and remote inspection. This paper discusses the following NDT techniques, which have been successfully used for the past 15 years in FBTR: (i) Periscope and Projector, (ii) Core Co-ordinate Measuring Device and, (iii) Optical fiberscope. The inspection using these techniques have given confidence for further reactor operation at high power by giving useful data on the conditions of the components inside the reactor vessel.

• Advances in Energy Research
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• 제1권1호
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• pp.13-33
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• 2013

The present work is an attempt to provide an overview, about the status of R&D and current trends in Hydrogen Production using High Temperature Reactors. Bibliographic references from the INIS database, the Science Direct database and the NTIS database were downloaded and analyzed. Ten year data on the subject, published between 2001 and 2010, was selected for the study. Appropriate qued ry formulations on these databases, resulted in the retrieval of 621 unique bibliographic records. Using the content analysis method, all the records were analyzed. Part One of the analysis details Scientometric R&D indicators, Part Two is a subject-based analysis, grouped under: A. International Initiatives and Programmes for Hydrogen Production; B. European R&D initiatives for Hydrogen production; C. National Initiatives and Programmes for Nuclear Hydrogen Production; D. Reactor Technologies for Nuclear Hydrogen production; E. Fuel Developments; F. Hydrogen Production Processes using HTRs and G. Materials Consideration for Nuclear Hydrogen Production. The results of this analysis are summarized in the study.