<p>There is a widespread use of thermal hydraulic codes in nuclear industry. The codesare used to analyse the transient and steady-state behavior of the nuclear powerplants. The US Nuclear Regulatory Commission that has long experience of developing such codes are now incorporating the capabilities of their earlier codes into one modern simulation tool, called TRACE. The code is under development and validation work is required especially in the field of BWR applications. Eventually the code is expected to replace similar codes such as TRAC and Relap5.</p><p>With this in mind, a TRACE model of Forsmark 1 has been set up to investigate how well it can simulate a plant transient. On the 25th of July, 2006 there was a disturbance at Forsmark 1 that caused the RPV water level and pressure to decrease.In this project, plant data acquired during the event are used to validate the model of Forsmark 1. The validation work is focused on comparing measured and calculated water and pressure levels in the RPC during the transient.</p><p>The results show qualitatively good agreement with the validation data, however during a period of the simulations there are large discrepancies concerning the pressure and water level in the RPV. In total, 13 simulations are performed, studying the influences of parameters such as simulation time-step size, the feed water flow boundary conditions and the steam line isolation valve characteristics. Based on the results of the simulations, a number of recommendations are made regarding suggestions for further work.</p>

There is a widespread use of thermal hydraulic codes in nuclear industry. The codesare used to analyse the transient and steady-state behavior of the nuclear powerplants. The US Nuclear Regulatory Commission that has long experience of developing such codes are now incorporating the capabilities of their earlier codes into one modern simulation tool, called TRACE. The code is under development and validation work is required especially in the field of BWR applications. Eventually the code is expected to replace similar codes such as TRAC and Relap5. With this in mind, a TRACE model of Forsmark 1 has been set up to investigate how well it can simulate a plant transient. On the 25th of July, 2006 there was a disturbance at Forsmark 1 that caused the RPV water level and pressure to decrease.In this project, plant data acquired during the event are used to validate the model of Forsmark 1. The validation work is focused on comparing measured and calculated water and pressure levels in the RPC during the transient. The results show qualitatively good agreement with the validation data, however during a period of the simulations there are large discrepancies concerning the pressure and water level in the RPV. In total, 13 simulations are performed, studying the influences of parameters such as simulation time-step size, the feed water flow boundary conditions and the steam line isolation valve characteristics. Based on the results of the simulations, a number of recommendations are made regarding suggestions for further work.

The dry out criterion (MCPR) has been calculated for the most limiting H2-events for Forsmarks unit 2 and 3, at operating points that are normally not analyzed before each cycle. The operating points that normally are regarded as the ones with the lowest margin to dry out are the ones where the thermal power is the highest at agiven recirculation flow. This report shows that this is not the case for Forsmark 3. MCPR-values at partial power operating points are higher for the limiting case inside rather than on the boundary of the region of operation. It is therefore recommended that the method for determining the dry out criterion for Forsmark 3 is revised to account for this effect. It is recommended that the number of operating points studied is increased or that a conservative value is established of how large the effect of operating point can have on MCPR. This conclusion does not, however, apply to Forsmark 2 where the most limiting case has its largest MCPR-values at the boundary. The effect on MCPR of changing the A/B- and scram-runback ramps of the recirculation pumps for Forsmark 3 has also been calculated. The alternative rampused was found to give a decrease in the MCPR value between about 20-30 units, depending on fuel type, at partial power operation. The full power limit would not change because the most limiting case at full power is not dependent on the runback ramp of the recirculation pumps.

It takes a very long time for ionizing radiation of used nuclear fuel toreturn to a natural background level, for this reason one of the requirements for theselection of the location of a repository was that the environment as well people'shealth would be protected from the harmful effect of radioactivity. This requirementmeans that the waste must be isolated in a geological formation. In Sweden therepository will be built in the crystalline bedrock. The location for the Swedish nuclearfuel repository at nearly 500 meters depth at Forsmark in Östhammar was decided 3June 2009. The repository will be located at Söderviken, close to the Forsmarknuclear power plant in a 1.90 billion year old bedrock that will accommodate 12,000tons of spent nuclear fuel. The bedrock of Östhammar is a seismically quiet, howeverthere is a large system of fracture zones and fractures at the site considered to havebeen formed shortly after the ductile shear zone deformaton. The geology isdominated by medium grained metagranite with mafic intrusions. These rock volumeshave been subjected to metamorphism and ductile deformation at c. 1.85 Ga.The site investigations shown that the bedrock composition was asexpected, except for a few locations of a porous granite (episyenite) and a fracturedbedrock down to about 200 meters depth. This rock is relatively uncommon, but mayaffect the quality of the repository. Most episyenites are geographical associated tofractures and fracture zones, but there are exceptions where there are no distinctrelationships to the latter.

This master thesis is done within the Energy Systems Engineering program at Uppsala University and performed for Forsmarks Kraftgrupp, Vattenfall. The nuclear power plant at Forsmark consists of three BWR units and is an important component in the Swedish power system. The nuclear power units are individually connected to the 400 kV transmission grid to export their production, but also to supply the units with auxiliary power when needed. As a backup the units are also connected to the 70 kV grid and each have several sub grids supported by backup diesel engines and batteries.This is to guarantee that the nuclear power units always have electrical power to support their vital auxiliary systems. To evaluate the function of the separate local power grids of Forsmark’s nuclear units and their interaction with the offsite grid, the simulation software Simpow have been used. With Simpow, the function of controllers, pumps and motors, vital for the plants safety, can be analyzed for different operation conditions and plant changes. Today the Electrical Power Analysis and Plant Engineering Group are in the process of changing from Simpow to new simulation software, PowerFactory. During this process the question of how to best implement the plant controller have been raised. The plant controller controls the thermal power, pressure and water level of the reactor, all contributing to the dynamics of the units power supply during operation. An implementation of the plant controller exist in Simpow for the plant’s older units Forsmark 1 and 2, but for the newest unit Forsmark 3 there is only a standard model of a steam turbine with governor implemented. In this thesis the effect of the plant controller systems are investigated to serve as a basis for implementation of the plants dynamics in the modelling of Forsmark 3 in PowerFactory.

The cycling of water in the landscape is influenced by climate change on different time scales and in different directions regarding warming or cooling trends. Along with a changing climate, also the landscape and subsurface conditions, such as permafrost extent, may change in a long-term perspective. Permafrost and hydrology are intimately connected but the interactions between them are poorly understood, and the hydrological response to climate change is complex. The first part of this thesis investigates the effects of different drivers of future changes in hydrological flow and water storage components in the present day temperate Forsmark catchment in Sweden. The role of taliks and their influence on the exchange of deep and shallow groundwater in permafrost environments are also studied. This is done by a simulation sequence where the site is exposed to the landscape, climate and permafrost changes expected from site-specific numerical modeling. In the second part of this thesis, present day periglacial hydrological processes are studied in the Two Boat Lake catchment in western Greenland by field and model investigations of the site. The presence of a through talik below the Two Boat Lake, and data from a deep bedrock borehole into the talik, enable studies of the hydrological interactions between the lake and the talik. The spatial and temporal variability of the different water balance components of the catchment are quantified and the interactions between the surface water and the supra- and sub-permafrost groundwater are analyzed. The results show that the investigated changes in climate and permafrost influence hydrology more than the investigated landscape changes. Under permafrost conditions, the general direction of the exchange between deep and shallow groundwater may change relative to unfrozen conditions. The simulation studies of Forsmark show that the relative topography between taliks governs the recharging and discharging conditions, which is consistent with results from Two Boat Lake. The lake is located at high altitude relative to other taliks and hydraulic measurements indicate recharging conditions. The talik recharge is small compared to other water balance components and does not influence the lake level, which instead is found to be controlled by evapotranspiration and water inflow from the active layer. This is concluded from numerical simulations that take into account and combine evapotranspiration with other surface and subsurface hydrological processes. This thesis highlights the need to integrate surface and subsurface process modelling in order to quantitatively understand and represent the dynamics and complexity of hydrological interactions in periglacial catchments.

This thesis is the final part of bachelors program of Nuclear Engineering at UppsalaUniversity (program code KKI1). The work has been carried out in cooperation withForsmark Kraftgrupp AB. The topic studied deals with possible improvements ofefficiency at the planning department at block 2 in Forsmark i.e. FMP2. FMP2 plans and coordinates over 3,000 operations which is carried out during theannual overhaul of block 2 in Forsmark. Inspections, fuel replacement and repairs areincluded in the annual overhaul. The overhaul shall contribute to secure and reliableoperation of the block. The overhaul shall mitigate the risk of unplanned downtime. Also accidents, financiallosses and damage to reputation among public and the Regulators (i.e. SSM and IAEA)shall be avoided. The time for overhaul depends on actions that must be executedand the complexity of the work. Normally, the overhaul time last for a number ofweeks and in rarely cases it can last for months. One topic in the thesis has been to find and describe a way for the planningdepartment (FMP2) to improve status control in ongoing overhaul activities and toincrease the planning department efficiency i.e. to save time for the planningdepartment. With better status control and faster work in the planning departmentthe total overhaul time can be expected to be shortened. Additionally the thesisdiscusses the importance of reliable and secure nuclear power management with therespect to society. The thesis is partly based on examine of current work practices, a literature studyand interviews with employees. The literature study addresses interaction betweenhumans and technology and how to accomplish good decisions. The interviews havebeen made to gather experiences from earlier used working methods. This report shows that FMP2 's current working model is good, although not perfect.It is probable that efficiency improvements at the individual level can be reached thatincreases employed personnel working capacity. Enhanced efficiency can also bereached by using better computer programs that manages the functions that currentlyrequire several separate IT-systems. A number of recommendations are given in thereport for how operations can be improved. Among other things, a proposal toexplore how extraordinary working efforts shall be rewarded. The nuclear power energy importance for the Swedish electricity power balance hasbeen discussed. The conclusion is that customers, electricity generators and thepublic benefits from reliable and secure nuclear power management.

This thesis presents a closer look at correlations between major meteorological events and groundwater level responses observed in deep boreholes drilled in the bedrock at Forsmark, which is situated ca. 120 km north of Stockholm in the Fennoscandian Shield, Sweden. Understanding how large geological structures are hydraulically connected to the surface is of great importance as a repository for spent nuclear fuel is intended to be built in Forsmark. Understanding monitoring data under natural conditions gives greater knowledge of how the hydrogeological system near the surface might be affected during the construction, operation and closing phases of the repository.The hydrological monitoring of each borehole is performed in intervals (sections), i.e., the ground-water levels in the bedrock are measured at different depths. At the different depths, changes in pressure from different meteorological events is measured. A major precipitation event was recorded during a few hours between 21 and 22 September 2014. Groundwater level responses in four deep drill holes show different reaction rates and magnitudes depending on borehole location, the structures they inter-sect, and depth in the bedrock. Furthermore, the properties of the deformation zones determine how the groundwater levels respond to meteorological events. Previous work reveals that gently dipping defor-mation zones have higher hydraulic diffusivity than the steeply dipping deformation zones.Two major air pressure events combined with groundwater level reactions in two deep bedrock bore-holes were also analysed. A lowering of the air pressure resulted in a higher sea level, which is seen in the boreholes as an increase in the groundwater level and vice versa.Clear responses from meteorological events are seen where boreholes intersect gently dipping deformation zones that leads all the way up to the ground surface. / Syftet med examensarbetet är att studera korrelationer mellan diskreta meteorologiska händelser och responser hos grundvattennivåerna i djupa borrhål i kristallint berg. Undersökningsområdet är berggrun-den i Forsmark, Östhammars kommun, ca 120 km norr om Stockholm. Ett framtida slutförvar för använt kärnbränsle är planerat att byggas där och stora mängder meteorologisk, hydrologisk och geologiska data har tagits fram i detta område av Svensk Kärnbränslehantering AB (SKB). SKB har bland annat en meteorologisk mätstation och stort antal djupa borrhål med ett flertal tryckgivare i varje borrhål. Borr-hålens medellängd är ca 700 m.Tidigare undersökningar i området redovisar exempel på korrelationer mellan nederbörd och grund-vattennivånresponser i berggrunden. Hydrauliska responser har också observerats vid flera interferens-tester i området. Ett intressant exempel på korrelation mellan nederbörd och grundvattennivå är att tryck-förändringar kan skönjas 500 m ner i berget längs med flacka deformationszoner. Ett annat exempel är en korrelation mellan skillnader i lufttryck och responser i ett djupt borrhål som ligger ca 500 meter från havet. Skillnader i lufttryck mellan Sverige och Finland skapar förändringar i havsytans nivå. Högtryck i Finland och lågtryck i Sverige ger en ökad havsytenivå vid Sveriges kust och detta påverkar vatten-trycket i djupa borrhål där dessa korsar deformationszoner som finns både under hav och land. Ett slags vågsystem ute i havet kunde ses som ökat och minskat vattentryck i ett borrhål på land.I detta arbete har en djupare undersökning av kopplingar mellan nederbörd och lufttryckprocesser på land och responser i djupt berg gjorts. Vid studier av insamlade data har korrelationer mellan meteoro-logiska och hydrologiska pulser på ytan och responser i djupa borrhål påträffats. Fyra kärnborrhål, KFM02A, KFM06A, KFM10A och KFM03A, utspridda i området, påvisar dessa samband.Tydliga responser i grundvattennivåer sker i berget där borrhålen korsar deformationszoner som går ända upp till markytan. Skillnad i respons kan också ses beroende på om de korsande deformations-zonerna är brant stupande eller svagt stupande. Svagt stupande deformationszoner har en högre hydraulisk diffusivitet än de brant stupande och detta beror bland annat på storleksskillnader i horisontella och vertikala spänningar. Kontrasten i spänningarna håller de svagt stupande zonerna öppna vilket resulterar i en hög hydraulisk diffusivitet.

Svensk Kärnbränslehantering AB beslutade 2009 att bygga ett slutförvar av använt kärnbränsle i anslutning till kärnkraftverket i Forsmark. Tekniken för slutförvaret går ut på att omge kapslarna med bentonitlera som skydd mot vatten och bergsrörelser. Studier har dock påpekat att bentonitleran riskerar att kemiskt erodera om jonstyrkan (baskatjonerna) i grundvattnet som omsluter förvaringen blir för låg. Baskatjoner består av natrium, kalium, kalcium och magnesium. Dessa joner är viktiga för bland annat att neutralisera syror i mark och vatten. Förekomsten av dessa har sedan 90-talet minskat men kan påverkas av både ökad nederbördsmängd och ökad temperatur i vissa regioner. Baskatjoner kan lakas ur marken när pH minskar eller komma via deposition från nederbörden. Studien syftar till att utreda vilka faktorer som påverkar dels förekomsten av baskatjoner, dels dess trender i tre olika vattentyper i Forsmark: grunt grundvatten, sjövatten och vattendrag. Dataunderlaget för baskatjonerna kom från Svensk Kärnbränslehantering AB och nederbördsmängd och temperatur från Sveriges Meteorologiska och Hydrologiska Institut. De statistiska testerna som utfördes var främst Wilcoxon rank-sum test, Spearmans rangkorrelation, Mann-Kendalls trend- test och Sen’s slope-metoden. Analyserna har utförts med statistikprogramvaran R och de geografiska med QGIS. Resultatet visade att flera provtagningspunkter låg på en låg altitud och inom samma delavrinningsområde. Det fanns små skillnader i baskatjonskoncentrationen i de tre vattentyperna oberoende av berggrund, jordart eller terräng. Dock återfanns högst koncentration i de flesta fall i grunt grundvatten vilket kunde bero på höga halter natrium från havsvattnet samt kalksten i jordlagren. Korrelationerna var få varav sulfat var den som tydligast visade på ett förhållande med baskatjonerna i alla tre vattentyperna. Inte heller kunde en samvariation med temperatur och nederbörd statistiskt säkerställas. Trenderna visade på minskande koncentration av baskatjoner i grunt grundvatten och i sjövatten. Om dessa trender fortsätter utifrån studiens resultat kan det på sikt finnas en risk för erodering av bentonitleran runt kapslarna till följd av landhöjning och utbyte av det nuvarande bräckta grundvattnet. / The Swedish Nuclear Fuel and Waste Management Company decided in 2009 to build a final repository for spent nuclear fuel in connection with the nuclear power plant in Forsmark. The technology for the final repository involves surrounding the capsules with bentonite clay as protection against water and rock movements. However, studies have pointed out that the bentonite clay is at risk of chemically eroding if the ionic strength of the groundwater surrounding the repository becomes too low. Base cations consist of sodium, potassium, calcium, and magnesium. These ions are important for neutralizing acids in soil and water. The occurrence of these has decreased since the 90s but can be affected by both increased rainfall and increased temperature in certain regions. Base cations can further be leached from the soil when the pH decreases or come via deposition from precipitation. This study aims to investigate which factors affect the presence of base cations and their trends in three different types of water in Forsmark: shallow groundwater, lake water and stream water. The data set for the base cations came from the Swedish Nuclear Fuel and Waste Management Company and rainfall and temperature from the Swedish Meteorological and Hydrological Institute. The statistical tests performed were mainly the Wilcoxon rank-sum test, Spearman's rank correlation, Mann-Kendall's trend test and Sen's slope method. The analyzes have been performed with the statistical software R and the geographic ones with QGIS. The result showed that several sampling points were at a low altitude and within the same sub-catchment. There were small differences in base cation concentration in the three water types regardless of bedrock, soil type or terrain. However, the highest concentration was found in most cases in shallow groundwater, which could be due to high levels of sodium from seawater and limestone in the soil layers. The correlations were few, of which sulfate was the one that most clearly showed a relationship with the base cations in all three water types. Nor could a co-variation with temperature and precipitation be statistically ensured. The trends showed a decreasing concentration of base cations in shallow groundwater and in lake water. If the trends continue based on the results, in the long term there may be a risk of erosion of the bentonite clay that surrounds the capsules because of land uplift and replacement of the current brackish ground water.

The society changes rapidly and is heavily dependent on energy. The Energy usage in buildings account for about 40% of total Sweden's energy usage, where energy is used by buildings for electricity, cooling and heating. Therefore, energy is an important issue in today's society from an energy use approach to stop the global warming. In this work, a survey was carried out by an office building in Forsmark Kraftgrupp AB to find out about energy use and create a basis for energy-saving measures. The IDA ICE 4.7.1 program was used to simulate the building's energy use by creating a base model of the building. After that, the base model has been compared with different energy efficiency measures to check where the biggest and least energy saving potentials occur. The result shows that the total energy use in the office building is 198 125 kWh / year. The simulations show that energy efficiency measures could reduce energy use in the building by 81 962 kWh / year, which corresponds to 41.4% of the total energy use. Time control of ventilation systems gives the largest energy savings of 51, 2 kWh / m2, year.