Development of Cross-Section Library for DYN3D Code

At present, SSTC NRS uses the HELIOS code for generation of few-group cross-section libraries for WWER core calculations. There is an urgent issue of selecting the appropriate approach to implement the cross-section library into the DYN3D code. The paper overviews the application of approaches used by SSTC NRS, such as a multidimensional table and polynomial dependences. The capabilities and possible extension of each approach are described with inherent advantages and disadvantages. In addition, the model development and cross-section preparation for the WWER-1000 radial reflector taking into account discontinuity factors are discussed. Brief results of calculations with the use of different approaches are presented.На даний час ДНТЦ ЯРБ використовує спектральний код HELIOS для підготовки малогрупових бібліотек нейтронно-фізичних констант тепловидільних збірок (ТВЗ) активних зон ВВЕР. У процесі розробки моделей ТВЗ виникає актуальна проблема вибору правильного підходу до реалізації бібліотеки констант у коді DYN3D. У даній роботі надано результати досліджень підходів, що використовує ДНТЦ ЯРБ, — реалізації бібліотеки у вигляді багатовимірної таблиці й поліноміальних залежностей. Розглянуто підходи ДНТЦ ЯРБ до вирішення проблеми розробки моделі та підготовки нейтронно-фізичних констант радіального відбивача для ВВЕР-1000 з урахуванням факторів розривності. Наведено короткі результати розрахункових досліджень при використанні різних підходів.В настоящее время ГНТЦ ЯРБ использует спектральный код HELIOS для подготовки малогрупповых библиотек нейтронно-физических констант тепловыделяющих сборок активных зон ВВЭР. В ходе разработки моделей тепловыделяющих сборок возникает актуальная проблема выбора правильного подхода к реализации библиотеки констант в коде DYN3D. В данной роботе представлены результаты исследований подходов, используемых ГНТЦ ЯРБ, — реализации библиотеки в виде многомерной таблицы и полиномиальных зависимостей. Показаны подходы к решению проблемы разработки модели и подготовки нейтронно-физических констант радиального отражателя для ВВЭР- 1000 с учетом факторов разрывности. Даны краткие результаты расчетных исследований при использовании различных подходов

Experience and Perspective of Best-Estimate Approach Application for RIA Analysis

The use of best-estimate approach for WWER safety analysis in RIA is considered. The relevance of this problem is concerned with small margin to acceptance criteria under the conservative approach and becomes stronger under power uprate of nuclear power plants. Previous experience in this area for WWER-1000 reactor types is overviewed. The necessity to extend these activities for successful implementation of the best-estimate approach is noticed and areas of further work are discussed.Рассмотрены вопросы использования и реализации подходов наилучшей оценки для анализа безопасности ВВЭР в реактивностных авариях. Актуальность проблемы связана с малыми запасами до критериев приемлемости при реализации консервативного подхода, особенно усиливается в условиях повышения номинального уровня мощности реакторной установки. Представлен краткий обзор предыдущего опыта в этой области для реакторов ВВЭР-1000. Указана необходимость расширения работ для успешной реализации подходов наилучшей оценки, обсуждены направления дальнейшей деятельности.Розглянуто питання використання та реалізації підходів найкращої оцінки для аналізу безпеки ВВЕР у реактивнісних аваріях. Актуальність проблеми пов’язана з малими запасами до критеріїв прийнятності при реалізації консервативного підходу, що особливо посилюється в умовах підвищення номінального рівня потужності реакторної установки. Представлено короткий огляд попереднього досвіду в цій галузі для реакторів ВВЕР-1000. Зазначено необхідність розширення робіт для успішної реалізації підходів найкращої оцінки, обговорено напрями подальшої діяльності

The Application of the TRANSURANUS Fuel Performance Code to WWER Fuel: An Overview

The present review paper outlines the collaborative efforts for the establishment of the TRANSURANUS version for the simulation of VVER fuel pin behavior, which has been presented at this series of international conferences organized by the INRNE since 1994. The paper therefore starts with very briefly reviewing the development of the TRANSURANUS fuel performance code in collaboration with various organizations from EU member states operating VVER reactors. The development started with the application to normal operating conditions in the frame of different bilateral agreements supported by the European Commission and the IAEA (e.g. PHARE and PECO projects), followed by the specific project dedicated to its application to the loss of coolant type accidents (EXTRA). In the second part of the paper, a summary will be given of the verification, validation and benchmarking efforts, on the basis of the experimental data included in the IFPE database of the NEA, as well as in the frame of the co-ordinated research projects of the IAEA (e.g. FUMEX, FUMAC), and most recently also the Euratom project ESSANUF co-ordinated by Westinghouse Electric Sweden. Finally, we will outline the current plans for further improving the simulation capabilities of VVER fuels by means of TRANSURANUS

Morphological and molecular characterization of an African freshwater fish trypanosome, including its development in a leech vector

Trypanosomes are ubiquitous blood parasites of fishes and at least 16 species were originally described infecting African freshwater fishes. This number was later reduced to six and in the late 1990s it was proposed that most records of freshwater fish trypanosomes across Africa are Trypanosoma mukasai Hoare, 1932. Recently, results from a molecular analysis of fish trypanosomes from the Okavango Delta, Botswana, reported the presence of at least two genotypic groups and concluded that the identification of T. mukasai remains problematic. The aims of the present study were thus to elucidate the life cycle of a freshwater fish trypanosome from southern Africa and to do a morphological and molecular characterization of this parasite from both the fish host and leech vector. To locate trypanosome stages, leeches were removed from fishes captured in the Phongolo River, South Africa, and fish blood films and leech squashes were Giemsa-stained and screened. To determine whether trypanosome stages in fishes and leeches were of the same genotype, DNA was extracted and fragments of the 18S rDNA gene were amplified and sequenced. Trypanosomes were detected in the fish families Cichlidae, Clariidae, Mochokidae and Schilbeidae. Sequence data showed that the trypanosome from one of the leeches, identified as Batracobdelloides tricarinata (Blanchard, 1897), was highly similar to those obtained from the plain squeaker, Synodontis zambezensis, with 0.7% difference recorded between them. From morphological and molecular data presented here, it is clear that the trypanosomes from Phongolo are closely related to those of the Okavango and should be considered as a single diverse species with genetic differentiation between 0.4–2.9%, under the 3–5% differences expected to be seen between true distinct species within the rRNA. Developmental stages of the trypanosome found in the leech B. tricarinata supports its status as the vector and the molecular evidence shows the relationship between the trypanosome in the fish and leech, but also illustrates the exceptional genetic and morphological diversity of a single species of trypanosome between host species. The work presented here provides us with clear information to take further steps in resolving the taxonomy and systematics of African freshwater fish trypanosome

Molecular mechanisms of thermal resistance of the insect trypanosomatid <i>Crithidia thermophila</i>

<div><p>In the present work, we investigated molecular mechanisms governing thermal resistance of a monoxenous trypanosomatid <i>Crithidia luciliae thermophila</i>, which we reclassified as a separate species <i>C</i>. <i>thermophila</i>. We analyzed morphology, growth kinetics, and transcriptomic profiles of flagellates cultivated at low (23°C) and elevated (34°C) temperature. When maintained at high temperature, they grew significantly faster, became shorter, with genes involved in sugar metabolism and mitochondrial stress protection significantly upregulated. Comparison with another thermoresistant monoxenous trypanosomatid, <i>Leptomonas seymouri</i>, revealed dramatic differences in transcription profiles of the two species with only few genes showing the same expression pattern. This disparity illustrates differences in the biology of these two parasites and distinct mechanisms of their thermotolerance, a prerequisite for living in warm-blooded vertebrates.</p></div

Molecular mechanisms of thermal resistance of the insect trypanosomatid Crithidia thermophila

In the present work, we investigated molecular mechanisms governing thermal resistance of a monoxenous trypanosomatid Crithidia luciliae thermophila, which we reclassified as a separate species C. thermophila. We analyzed morphology, growth kinetics, and transcriptomic profiles of flagellates cultivated at low (23°C) and elevated (34°C) temperature. When maintained at high temperature, they grew significantly faster, became shorter, with genes involved in sugar metabolism and mitochondrial stress protection significantly upregulated. Comparison with another thermoresistant monoxenous trypanosomatid, Leptomonas seymouri, revealed dramatic differences in transcription profiles of the two species with only few genes showing the same expression pattern. This disparity illustrates differences in the biology of these two parasites and distinct mechanisms of their thermotolerance, a prerequisite for living in warm-blooded vertebrates

Fuel Modelling in Accident Conditions (FUMAC)

Improved understanding of fuel performance can lead to a reduction in operating margins, increased flexibility in fuel management and improved operating economics. To better understand fuel performance, the IAEA has addressed different aspects of fuel behaviour modelling in a series of coordinated research projects aimed at assessing fuel performance codes and supporting countries with code development and application needs (FUMEX series); building a database of well defined experiments suitable for code validation, in association with the OECD Nuclear Energy Agency (OECD/NEA); transferring a mature fuel modelling code to developing countries and supporting its adaptation to the requirements of particular reactors; providing guidance on applying that code to reactor operation and safety assessments; and providing guidelines for code quality assurance, code licensing and code application to fuel licensing. The present publication describes the results of the coordinated research project on Fuel Modelling in Accident Conditions (FUMAC), initiated under the IAEA Action Plan on Nuclear Safety implemented after the accident at the Fukushima Daiichi nuclear power plant. The project, which ran from 2014 to 2018, followed previous projects on fuel modelling: D-COM 1982-1984, FUMEX 1993–1996, FUMEX-II 2002-2006 and FUMEX-III 2008-2012. The project participants used data derived from accident simulation experiments, in particular data designed to investigate the fuel behaviour during design basis accident and design extension conditions, to carry out calculations on selected priority cases identified at the first research coordination meeting. These priority cases were designed to support the participants’ individual priorities and were chosen as the best available to help determine which of the many models used in the codes most closely reflect reality. The cases were also used for verification and validation purposes, and for inter-code comparisons