Analysis of PACTEL small break LOCA experiment using TRACE

A small break loss-of-coolant accident (SBLOCA) is one of problems investigated in an NPP operation. Such accident can be analyzed using an experiment facility and TRACE thermal-hydraulic system code. A series of SBLOCA experiments was carried out on Parallel Channel Test Loop (PACTEL) facility, exploited together with Technical Research Centre of Finland VTT Energy and Lappeenranta University of Technology (LUT), in order to investigate two-phase phenomena related to a VVER-type reactor. The experiments and a TRACE model of the PACTEL facility are described in the paper. In addition, there is the TRACE code description with main field equations. At the work, calculations of a SBLOCA series are implemented and after the calculations, the thesis discusses the validation of TRACE and concludes with an assessment of the usefulness and accuracy of the code in calculating small breaks.

Scaling analysis of small break experiments in PACTEL

The purpose of this thesis is to study the scalability of small break LOCA experiments. The study is performed on the experimental data, as well as on the results of thermal hydraulic computation performed on TRACE code. The SBLOCA experiments were performed on PACTEL facility situated at LUT. The temporal scaling of the results was done by relating the total coolant mass in the system with the initial break mass flow and using the quotient to scale the experiment time. The results showed many similarities in the behaviour of pressure and break mass flow between the experiments.

Modeling of Pressurizer Using APROS and TRACE Thermal Hydraulic Codes

Diplomityön tavoitteena on paineistimen yksityiskohtainen mallintaminen APROS- ja TRACE- termohydrauliikkaohjelmistoja käyttäen. Rakennetut paineistinmallit testattiin vertaamalla laskentatuloksia paineistimen täyttymistä, tyhjentymistä ja ruiskutusta käsittelevistä erilliskokeista saatuun mittausdataan. Tutkimuksen päätavoitteena on APROSin paineistinmallin validoiminen käyttäen vertailuaineistona PACTEL ATWS-koesarjan sopivia paineistinkokeita sekä MIT Pressurizer- ja Neptunus- erilliskokeita. Lisäksi rakennettiin malli Loviisan ydinvoimalaitoksen paineistimesta, jota käytettiin turbiinitrippitransientin simulointiin tarkoituksena selvittää mahdolliset voimalaitoksen ja koelaitteistojen mittakaavaerosta johtuvat vaikutukset APROSin paineistinlaskentaan. Kokeiden simuloinnissa testattiin erilaisia noodituksia ja mallinnusvaihtoehtoja, kuten entalpian ensimmäisen ja toisen kertaluvun diskretisointia, ja APROSin sekä TRACEn antamia tuloksia vertailtiin kattavasti toisiinsa. APROSin paineistinmallin lämmönsiirtokorrelaatioissa havaittiin merkittävä puute ja laskentatuloksiin saatiin huomattava parannus ottamalla käyttöön uusi seinämälauhtumismalli. Työssä tehdyt TRACE-simulaatiot ovat osa United States Nuclear Regulatory Commissionin kansainvälistä CAMP-koodinkehitys-ja validointiohjelmaa.

Design and validation of stateful composite RESTful web services

A web service is a software system that provides a machine-processable interface to the other machines over the network using different Internet protocols. They are being increasingly used in the industry in order to automate different tasks and offer services to a wider audience. The REST architectural style aims at producing scalable and extensible web services using technologies that play well with the existing tools and infrastructure of the web. It provides a uniform set of operation that can be used to invoke a CRUD interface (create, retrieve, update and delete) of a web service. The stateless behavior of the service interface requires that every request to a resource is independent of the previous ones facilitating scalability. Automated systems, e.g., hotel reservation systems, provide advanced scenarios for stateful services that require a certain sequence of requests that must be followed in order to fulfill the service goals. Designing and developing such services for advanced scenarios with REST constraints require rigorous approaches that are capable of creating web services that can be trusted for their behavior. Systems that can be trusted for their behavior can be termed as dependable systems. This thesis presents an integrated design, analysis and validation approach that facilitates the service developer to create dependable and stateful REST web services. The main contribution of this thesis is that we provide a novel model-driven methodology to design behavioral REST web service interfaces and their compositions. The behavioral interfaces provide information on what methods can be invoked on a service and the pre- and post-conditions of these methods. The methodology uses Unified Modeling Language (UML), as the modeling language, which has a wide user base and has mature tools that are continuously evolving. We have used UML class diagram and UML state machine diagram with additional design constraints to provide resource and behavioral models, respectively, for designing REST web service interfaces. These service design models serve as a specification document and the information presented in them have manifold applications. The service design models also contain information about the time and domain requirements of the service that can help in requirement traceability which is an important part of our approach. Requirement traceability helps in capturing faults in the design models and other elements of software development environment by tracing back and forth the unfulfilled requirements of the service. The information about service actors is also included in the design models which is required for authenticating the service requests by authorized actors since not all types of users have access to all the resources. In addition, following our design approach, the service developer can ensure that the designed web service interfaces will be REST compliant. The second contribution of this thesis is consistency analysis of the behavioral REST interfaces. To overcome the inconsistency problem and design errors in our service models, we have used semantic technologies. The REST interfaces are represented in web ontology language, OWL2, that can be part of the semantic web. These interfaces are used with OWL 2 reasoners to check unsatisfiable concepts which result in implementations that fail. This work is fully automated thanks to the implemented translation tool and the existing OWL 2 reasoners. The third contribution of this thesis is the verification and validation of REST web services. We have used model checking techniques with UPPAAL model checker for this purpose. The timed automata of UML based service design models are generated with our transformation tool that are verified for their basic characteristics like deadlock freedom, liveness, reachability and safety. The implementation of a web service is tested using a black-box testing approach. Test cases are generated from the UPPAAL timed automata and using the online testing tool, UPPAAL TRON, the service implementation is validated at runtime against its specifications. Requirement traceability is also addressed in our validation approach with which we can see what service goals are met and trace back the unfulfilled service goals to detect the faults in the design models. A final contribution of the thesis is an implementation of behavioral REST interfaces and service monitors from the service design models. The partial code generation tool creates code skeletons of REST web services with method pre and post-conditions. The preconditions of methods constrain the user to invoke the stateful REST service under the right conditions and the post condition constraint the service developer to implement the right functionality. The details of the methods can be manually inserted by the developer as required. We do not target complete automation because we focus only on the interface aspects of the web service. The applicability of the approach is demonstrated with a pedagogical example of a hotel room booking service and a relatively complex worked example of holiday booking service taken from the industrial context. The former example presents a simple explanation of the approach and the later worked example shows how stateful and timed web services offering complex scenarios and involving other web services can be constructed using our approach.

VVER-440 Thermal Hydraulics as a Computer Code Validation Challenge

This thesis concentrates on the validation of a generic thermal hydraulic computer code TRACE under the challenges of the VVER-440 reactor type. The code capability to model the VVER-440 geometry and thermal hydraulic phenomena specific to this reactor design has been examined and demonstrated acceptable. The main challenge in VVER-440 thermal hydraulics appeared in the modelling of the horizontal steam generator. The major challenge here is not in the code physics or numerics but in the formulation of a representative nodalization structure. Another VVER-440 specialty, the hot leg loop seals, challenges the system codes functionally in general, but proved readily representable. Computer code models have to be validated against experiments to achieve confidence in code models. When new computer code is to be used for nuclear power plant safety analysis, it must first be validated against a large variety of different experiments. The validation process has to cover both the code itself and the code input. Uncertainties of different nature are identified in the different phases of the validation procedure and can even be quantified. This thesis presents a novel approach to the input model validation and uncertainty evaluation in the different stages of the computer code validation procedure. This thesis also demonstrates that in the safety analysis, there are inevitably significant uncertainties that are not statistically quantifiable; they need to be and can be addressed by other, less simplistic means, ultimately relying on the competence of the analysts and the capability of the community to support the experimental verification of analytical assumptions. This method completes essentially the commonly used uncertainty assessment methods, which are usually conducted using only statistical methods.

Clinical Learning Environment and Supervision. Development and Validation of the CLES Evaluation Scale

The purpose of the study is: (1) to describe how nursing students' experienced their clinical learning environment and the supervision given by staff nurses working in hospital settings; and (2) to develop and test an evaluation scale of Clinical Learning Environment and Supervision (CLES). The study has been carried out in different phases. The pilot study (n=163) explored the association between the characteristics of a ward and its evaluation as a learning environment by students. The second version of research instrument (which was developed by the results of this pilot study) were tested by an expert panel (n=9 nurse teachers) and test-retest group formed by student nurses (n=38). After this evaluative phase, the CLES was formed as the basic research instrument for this study and it was tested with the Finnish main sample (n=416). In this phase, a concurrent validity instrument (Dunn & Burnett 1995) was used to confirm the validation process of CLES. The international comparative study was made by comparing the Finnish main sample with a British sample (n=142). The international comparative study was necessary for two reasons. In the instrument developing process, there is a need to test the new instrument in some other nursing culture. Other reason for comparative international study is the reflecting the impact of open employment markets in the European Union (EU) on the need to evaluate and to integrate EU health care educational systems. The results showed that the individualised supervision system is the most used supervision model and the supervisory relationship with personal mentor is the most meaningful single element of supervision evaluated by nursing students. The ward atmosphere and the management style of ward manager are the most important environmental factors of the clinical ward. The study integrates two theoretical elements - learning environment and supervision - in developing a preliminary theoretical model. The comparative international study showed that, Finnish students were more satisfied and evaluated their clinical placements and supervision with higher scores than students in the United Kingdom (UK). The difference between groups was statistical highly significant (p= 0.000). In the UK, clinical placements were longer but students met their nurse teachers less frequently than students in Finland. Arrangements for supervision were similar. This research process has produced the evaluation scale (CLES), which can be used in research and quality assessments of clinical learning environment and supervision in Finland and in the UK. CLES consists of 27 items and it is sub-divided into five sub-dimensions. Cronbach's alpha coefficient varied from high 0.94 to marginal 0.73. CLES is a compact evaluation scale and user-friendliness makes it suitable for continuing evaluation.

Validation Studies of Thermal-hydraulic Code for Safety Analysis of Nuclear Power Plants

This thesis gives an overview of the validation process for thermal hydraulic system codes and it presents in more detail the assessment and validation of the French code CATHARE for VVER calculations. Three assessment cases are presented: loop seal clearing, core reflooding and flow in a horizontal steam generator. The experience gained during these assessment and validation calculations has been used to analyze the behavior of the horizontal steam generator and the natural circulation in the geometry of the Loviisa nuclear power plant. The cases presented are not exhaustive, but they give a good overview of the work performed by the personnel of Lappeenranta University of Technology (LUT). Large part of the work has been performed in co-operation with the CATHARE-team in Grenoble, France. The design of a Russian type pressurized water reactor, VVER, differs from that of a Western-type PWR. Most of thermal-hydraulic system codes are validated only for the Western-type PWRs. Thus, the codes should be assessed and validated also for VVER design in order to establish any weaknesses in the models. This information is needed before codes can be used for the safety analysis. Theresults of the assessment and validation calculations presented here show that the CATHARE code can be used also for the thermal-hydraulic safety studies for VVER type plants. However, some areas have been indicated which need to be reassessed after further experimental data become available. These areas are mostly connected to the horizontal stem generators, like condensation and phase separation in primary side tubes. The work presented in this thesis covers a large numberof the phenomena included in the CSNI code validation matrices for small and intermediate leaks and for transients. Also some of the phenomena included in the matrix for large break LOCAs are covered. The matrices for code validation for VVER applications should be used when future experimental programs are planned for code validation.

Formation and Control of Trace Metal Emissions in Co-Firing of Biomass, Peat, and Wastes in Fluidised Bed Combustors

Environmentally harmful consequences of fossil fuel utilisation andthe landfilling of wastes have increased the interest among the energy producers to consider the use of alternative fuels like wood fuels and Refuse-Derived Fuels, RDFs. The fluidised bed technology that allows the flexible use of a variety of different fuels is commonly used at small- and medium-sized power plants ofmunicipalities and industry in Finland. Since there is only one mass-burn plantcurrently in operation in the country and no intention to build new ones, the co-firing of pre-processed wastes in fluidised bed boilers has become the most generally applied waste-to-energy concept in Finland. The recently validated EU Directive on Incineration of Wastes aims to mitigate environmentally harmful pollutants of waste incineration and co-incineration of wastes with conventional fuels. Apart from gaseous flue gas pollutants and dust, the emissions of toxic tracemetals are limited. The implementation of the Directive's restrictions in the Finnish legislation is assumed to limit the co-firing of waste fuels, due to the insufficient reduction of the regulated air pollutants in the existing flue gas cleaning devices. Trace metals emission formation and reduction in the ESP, the condensing wet scrubber, the fabric filter, and the humidification reactor were studied, experimentally, in full- and pilot-scale combustors utilising the bubbling fluidised bed technology, and, theoretically, by means of reactor model calculations. The core of the model is a thermodynamic equilibrium analysis. The experiments were carried out with wood chips, sawdust, and peat, and their refuse-derived fuel, RDF, blends. In all, ten different fuels or fuel blends were tested. Relatively high concentrations of trace metals in RDFs compared to the concentrations of these metals in wood fuels increased the trace metal concentrations in the flue gas after the boiler ten- to hundred-folds, when RDF was co-fired with sawdust in a full-scale BFB boiler. In the case of peat, lesser increase in trace metal concentrations was observed, due to the higher initial trace metal concentrations of peat compared to sawdust. Despite the high removal rate of most of the trace metals in the ESP, the Directive emission limits for trace metals were exceeded in each of the RDF co-firing tests. The dominat trace metals in fluegas after the ESP were Cu, Pb and Mn. In the condensing wet scrubber, the flue gas trace metal emissions were reduced below the Directive emission limits, whenRDF pellet was used as a co-firing fuel together with sawdust and peat. High chlorine content of the RDFs enhanced the mercuric chloride formation and hence the mercury removal in the ESP and scrubber. Mercury emissions were lower than theDirective emission limit for total Hg, 0.05 mg/Nm3, in all full-scale co-firingtests already in the flue gas after the ESP. The pilot-scale experiments with aBFB combustor equipped with a fabric filter revealed that the fabric filter alone is able to reduce the trace metal concentrations, including mercury, in the flue gas during the RDF co-firing approximately to the same level as they are during the wood chip firing. Lower trace metal emissions than the Directive limits were easily reached even with a 40% thermal share of RDF co-firing with sawdust.Enrichment of trace metals in the submicron fly ash particle fraction because of RDF co-firing was not observed in the test runs where sawdust was used as the main fuel. The combustion of RDF pellets with peat caused an enrichment of As, Cd, Co, Pb, Sb, and V in the submicron particle mode. Accumulation and release oftrace metals in the bed material was examined by means of a bed material analysis, mass balance calculations and a reactor model. Lead, zinc and copper were found to have a tendency to be accumulated in the bed material but also to have a tendency to be released from the bed material into the combustion gases, if the combustion conditions were changed. The concentration of the trace metal in the combustion gases of the bubbling fluidised bed boiler was found to be a summary of trace metal fluxes from three main sources. They were (1) the trace metal flux from the burning fuel particle (2) the trace metal flux from the ash in the bed, and (3) the trace metal flux from the active alkali metal layer on the sand (and ash) particles in the bed. The amount of chlorine in the system, the combustion temperature, the fuel ash composition and the saturation state of the bed material in regard to trace metals were discovered to be key factors affecting therelease process. During the co-firing of waste fuels with variable amounts of e.g. ash and chlorine, it is extremely important to consider the possible ongoingaccumulation and/or release of the trace metals in the bed, when determining the flue gas trace metal emissions. If the state of the combustion process in regard to trace metals accumulation and/or release in the bed material is not known,it may happen that emissions from the bed material rather than the combustion of the fuel in question are measured and reported.

Benchmarked Quality Measurement Process in a Software Validation Process

Jatkuva laadunmittaus osana ohjelmistoprosessia on yleistynyt ohjelmistoyritysten keskuudessa viime vuosien aikana. ISO 9001:2000 -laatustandardi vaatii yrityksiltä tuotteiden ja prosessien laadun mittaamista ja seuraamista. Laadun mittareiden valinta on haastava tehtävä. Yritykset luulevat usein mittaavansa laatua, vaikka ne todellisuudessa mittaavatkin ohjelmistojen eri ominaisuuksia kuten kokoa tai monimutkaisuutta. Tässä diplomityössä kehitetään ohjelmistojen validointiprosessiin vertailuun perustuva laadunmittausprosessi ohjelmistotuotteiden laadun arviointiin, mittaamiseen ja seurantaan. Laatumittarit valitaan ennalta määriteltyjen kriteereiden mukaisesti, ja niille asetetaan tavoitearvot vertailuanalyysistä saatujen tulosten perusteella. Laadunmittausprosessin lisäksi työssä annetaan suositus prosessin käyttöönotosta ja käytöstä osana yrityksen toimintaa, mikä mahdollistaa jatkuvan seurannan sekä kehityksen tulevaisuudessa.

TRACE ja sen käyttö painevesilaitosten mallinnuksessa

Tässä kandidaatintyössä on esitelty U.S. NRC:n kehittämä TRAC/RELAP Advanced Computational Engine termohydrauliikkamallinnusohjelmisto sekä sillä luodun yksinkertaistetun painevesilaitoksen mallin pienimuotoinen simulointi.

Validation of plant dynamic model by online and laboratory measurements – a tool to predict online COD loads out of production of mechanical printing papers

COD discharges out of processes have increased in line with elevating brightness demands for mechanical pulp and papers. The share of lignin-like substances in COD discharges is on average 75%. In this thesis, a plant dynamic model was created and validated as a means to predict COD loading and discharges out of a mill. The assays were carried out in one paper mill integrate producing mechanical printing papers. The objective in the modeling of plant dynamics was to predict day averages of COD load and discharges out of mills. This means that online data, like 1) the level of large storage towers of pulp and white water 2) pulp dosages, 3) production rates and 4) internal white water flows and discharges were used to create transients into the balances of solids and white water, referred to as “plant dynamics”. A conversion coefficient was verified between TOC and COD. The conversion coefficient was used for predicting the flows from TOC to COD to the waste water treatment plant. The COD load was modeled with similar uncertainty as in reference TOC sampling. The water balance of waste water treatment was validated by the reference concentration of COD. The difference of COD predictions against references was within the same deviation of TOC-predictions. The modeled yield losses and retention values of TOC in pulping and bleaching processes and the modeled fixing of colloidal TOC to solids between the pulping plant and the aeration basin in the waste water treatment plant were similar to references presented in literature. The valid water balances of the waste water treatment plant and the reduction model of lignin-like substances produced a valid prediction of COD discharges out of the mill. A 30% increase in the release of lignin-like substances in the form of production problems was observed in pulping and bleaching processes. The same increase was observed in COD discharges out of waste water treatment. In the prediction of annual COD discharge, it was noticed that the reduction of lignin has a wide deviation from year to year and from one mill to another. This made it difficult to compare the parameters of COD discharges validated in plant dynamic simulation with another mill producing mechanical printing papers. However, a trend of moving from unbleached towards high-brightness TMP in COD discharges was valid.

Improving Evaluation and Development Capability in Verification and Validation

Validation and verification operations encounter various challenges in product development process. Requirements for increasing the development cycle pace set new requests for component development process. Verification and validation usually represent the largest activities, up to 40 50 % of R&D resources utilized. This research studies validation and verification as part of case company's component development process. The target is to define framework that can be used in improvement of the validation and verification capability evaluation and development in display module development projects. Validation and verification definition and background is studied in this research. Additionally, theories such as project management, system, organisational learning and causality is studied. Framework and key findings of this research are presented. Feedback system according of the framework is defined and implemented to the case company. This research is divided to the theory and empirical parts. Theory part is conducted in literature review. Empirical part is done in case study. Constructive methode and design research methode are used in this research A framework for capability evaluation and development was defined and developed as result of this research. Key findings of this study were that double loop learning approach with validation and verification V+ model enables defining a feedback reporting solution. Additional results, some minor changes in validation and verification process were proposed. There are a few concerns expressed on the results on validity and reliability of this study. The most important one was the selected research method and the selected model itself. The final state can be normative, the researcher may set study results before the actual study and in the initial state, the researcher may describe expectations for the study. Finally reliability of this study, and validity of this work are studied.

Modelling of the PWR PACTEL vertical steam generator with the TRACE code

The behavior of the nuclear power plants must be known in all operational situations. Thermal hydraulics computer applications are used to simulate the behavior of the plants. The computer applications must be validated before they can be used reliably. The simulation results are compared against the experimental results. In this thesis a model of the PWR PACTEL steam generator was prepared with the TRAC/RELAP Advanced Computational Engine computer application. The simulation results can be compared against the results of the Advanced Process Simulator analysis software in future. Development of the model of the PWR PACTEL vertical steam generator is introduced in this thesis. Loss of feedwater transient simulation examples were carried out with the model.