Nuclear Power Plant In Switzerland Research Articles

Evaluation of the PAR Mitigation System in Swiss PWR Containment Using the GOTHIC Code

The installation of passive autocatalytic recombiners (PARs) in the containment of operating nuclear power plants (NPPs) is increasingly based on three-dimensional studies of severe accidents that accurately predict the hydrogen pathways and local accumulation regions in containment and examine the mitigation effects of the PARs on the hydrogen risk. The GOTHIC (Generation Of Thermal-Hydraulic Information for Containments) code is applied in this paper to study the effectiveness of the PARs installed in the Gösgen NPP in Switzerland. A fast release of a mixture of hydrogen and steam from the hot leg during a total station blackout is chosen as the limiting scenario. The PAR modeling approach is qualified simulating two experiments performed in the frame of the OECD/NEA (Organisation for Economic Co-operation and Development/Nuclear Energy Agency) THAI (Thermal-hydraulics, Hydrogen, Aerosols and Iodine) project. The results of the plant analyses show that the recombiners cannot prevent the formation of a stratified cloud of hydrogen (10% molar concentration), but they can mitigate the hydrogen accumulation once formed. In the case of the analyzed fast release scenario, which is characterized by increasing loads with large initial flow rate and high hydrogen concentration values, it is shown that, when a large number of recombiners are installed, the global outcome in relation to the combustion risk does not depend on the details of the single PAR behavior. The hydrogen ignition risk can be fully mitigated in a timeframe ranging from 15 to 30 min after the fast release, according to the dependence of the PAR efficiency model on the adopted parameters.

Fracture mechanics characterisation of reactor pressure vessel multi-layer weld metal

The multi-layer beltline welding seam of the Biblis C reactor pressure vessel was characterized by hardness, tensile, ISO-V impact and fracture toughness testing. The reference temperature, T0, was determined according to the test standard ASTM E1921 at different thickness positions of the multi-layer welding seam. Additionally, the influence of the specimen orientation on the ISO-V ductile-to-brittle transition temperature and T0 was investigated. In contrast to the T-S orientation (crack extension through the thickness) the crack front of the T-L oriented specimens (crack extension in welding direction) penetrates several welding beads. By means of fractographic and metallographic analyses of the fractured surface of fracture mechanics SE(B) specimens was shown that the distribution of the crack initiation sites is not necessarily correlated to the structure of the different welding beads along the crack front. Furthermore, it was found that the scatter of the fracture toughness values at cleavage failure, KJc, determined with T-S specimens is significantly higher than in case of the T-L specimens. T0 values measured at different thickness locations of the multi-layer welding seam vary in a range of about 40 K.The evaluated T0 values are used to determine the reference temperature RTTo for indexing the lower bound curve KIc(T) according to the Regulatory Guide ENSI-B01 for the ageing surveillance of nuclear power plants in Switzerland. It could be shown that the KIc values converted from the KJc values are enveloped by the lower bound curves.

Nuclear power plants and childhood leukaemia: lessons from the past and future directions

In the 1980s, leukaemia clusters were discovered around nuclear fuel reprocessing plants in Sellafield and Dounreay in the United Kingdom. This raised public concern about the risk of childhood leukaemia near nuclear power plants (NPPs). Since then, the topic has been well-studied, but methodological limitations make results difficult to interpret. Our review aims to: (1.) summarise current evidence on the relationship between NPPs and risk of childhood leukaemia, with a focus on the Swiss CANUPIS (Childhood cancer and nuclear power plants in Switzerland) study; (2.) discuss the limitations of previous research; and (3.) suggest directions for future research. There are various reasons that previous studies produced inconclusive results. These include: inadequate study designs and limited statistical power due to the low prevalence of exposure (living near a NPP) and outcome (leukaemia); lack of accurate exposure estimates; limited knowledge of the aetiology of childhood leukaemia, particularly of vulnerable time windows and latent periods; use of residential location at time of diagnosis only and lack of data on address histories; and inability to adjust for potential confounders. We conclude that risk of childhood leukaemia around NPPs should continue to be monitored and that study designs should be improved and standardised. Data should be pooled internationally to increase the statistical power. More research needs to be done on other putative risk factors for childhood cancer such as low-dose ionizing radiation, exposure to certain chemicals and exposure to infections. Studies should be designed to allow examining multiple exposures.

Probabilistic safety analysis of external floods – method and application

AbstractThe events of Fukushima amplified the scientific interest in the improvement of methods for probabilistic safety assessment (PSA) of extreme external events. The assessment of consequences of external floods belongs to this group of events. The paper presents the key steps of methodology for probabilistic safety assessment of external floods and a recent application for a nuclear power plant in Switzerland. The presented methodology is an extension of earlier activities and provides more focus on the PSA methodology part that may be applicable also for other studies.

Fair play in energy policy decisions: Procedural fairness, outcome fairness and acceptance of the decision to rebuild nuclear power plants

To raise public acceptance of new energy policies, promoting the fairness of the outcomes and of the decision-making procedure has been suggested. Very few studies have examined the role of fairness in public acceptance of rebuilding nuclear power plants. Therefore, using a large mail survey, we investigated the public’s acceptance of the decision to rebuild nuclear power plants in Switzerland by 2020. The study examined the influence of procedural fairness and outcome fairness on the acceptance of this decision, as well as other factors such as risk perception and benefit perception. Additionally, we investigated the moderating influence of general attitudes towards nuclear power on the relation between fairness and decision acceptance. Results indicated that outcome fairness strongly increased decision acceptance, along with general attitudes towards nuclear power and perceived economic benefits. Procedural fairness had only a small impact on decision acceptance. The influence of fairness on decision acceptance did not seem to depend on general nuclear attitudes. Our findings imply that, in the case of rebuilding nuclear power plants, perceived benefits and outcome fairness are important determinants of acceptance of the decision, while procedural fairness only has a limited impact.

Authors' response to: Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study: Figure 1

von Kernkraftwerken) 2 in the regression analyses of the inverse distance to the nearest nuclear power plant (NPP). He misinterprets numerically similar results that were reported on different scales: the results given on page 31 of our web appendix 2 are incidence rate ratios (IRRs) and not comparable to the KiKK study, which reported the untransformed regression coefficients. The regression coefficient in our study was 0.55 (95% confidence interval (CI) 1.22 to 2.32) in the resident cohort and 0.29 (2.36 to 1.79) in the birth cohort; clearly different from the 1.75 (95% lower confidence bound 0.65) in the German study. Schadelin also sees a discrepancy between our results for the resident cohort (using address of residence at diagnosis and showing a slight decrease of risk closer to NPPs) and the birth cohort (using address at birth and showing a slight increase of risk), but ignores the wide confidence intervals (which both include the null). We agree with Schadelin that the 1/distance model makes strong assumptions about the relation between dis- tance and risk. Due to the sharp increase of the function as distances approach zero, the few cases in close proximity to the NPPs will strongly influence regression parameters. Whereas the assumption that potential effects of radioactive emissions are limited to their immediate proximity is plausible, the precise functional form between distance and cancer incidence is unknown. Korblein pooled our data with results from two studies from Germany and the United Kingdom to suggest that our study 'confirms the excess of leukae- mia' observed in the latter studies. Given the large number of previous studies, the three studies included by Korblein represent a highly selected subset. For example, it is unclear why the French study by Laurier 3 was not included. This study reported a standardized incidence ratio (SIR) for the 0- to 5-km zone around NPPs of 0.96 (95% CI 0.31-2.24). In the UK the most recent figures (20 observed and 16.35 expected cases) published by the Committee on Medical Aspects of Radiation in the Environment (COMARE) 4 differ from those used by Korblein. Of note, COMARE reported a combined SIR of 1.07 (95% CI 0.92-1.26) from a random-effects meta- analysis of 37 estimates from five countries. 4 Korblein rightly points out that the 95% CI of the rate ratio estimate from the main analysis of child- hood leukaemia in 0- to 4-year olds just includes the point estimate (2.19) of the German KiKK study. However, there is in fact considerable disagreement between the two studies. Assuming that the true IRR for leukaemia in 0- to 4-year olds comparing the 0- to 5-km zone with the 415-km zone around NPPs is indeed 2.2 (as estimated in the KIKK study), the probability of observing an IRR of 1.2 (as in our study) is 0.03 (Figure 1) and the power of rejecting the null hypothesis of no association at the 5% significance level is 76%. Chirga argues that estimates of mean annual radiation doses originating from nuclear power plants (NPPs) are uncertain and that actual doses might fluctuate over time. He suggests that short spikes in emissions could increase the incidence of childhood cancer. Whereas we cannot exclude this possibility, we reiterate that our study provides little evidence that the rate of childhood cancer is higher in the proximity of NPPs. The few cases of cancer occur- ring in excess of the expected number of cases among

Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study

Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study

Planning, implementation and evaluation of an emergency exercise at the Paul Scherrer Institute

Abstract Like all nuclear power plants in Switzerland, the Paul Scherrer Institute in Villigen (PSI), Switzerland, has the duty to conduct an emergency exercise every year. The two monitoring authorities ENSI (Swiss Federal Nuclear Safety Inspectorate) and the BAG (Federal Office of Public Health – FOPH) use this exercise for their yearly audit of the emergency organization. The emergency organization of the Paul Scherrer Institute consists of the emergency staff, the fire brigade, the first aid station, the traffic- and the security platoon and the radiation safety, the latter consisting of the decontamination group, the radio analytics group and the measurement group (for radioactivity dispersion calculations). The framework is set up by the ENSI beforehand, based on a fixed cycle. For the emergency exercise of 2009 a plane crashing into the interim storage facility of the federal government (BZL) at PSI was assumed. This contribution describes the approach of the planning process, the performance and the evaluation of the exercise.

Ground-based remote sensing profiling and numerical weather prediction model to manage nuclear power plants meteorological surveillance in Switzerland

Abstract. The meteorological surveillance of the four nuclear power plants in Switzerland is of first importance in a densely populated area such as the Swiss Plateau. The project "Centrales Nucléaires et Météorologie" CN-MET aimed at providing a new security tool based on one hand on the development of a high resolution numerical weather prediction (NWP) model. The latter is providing essential nowcasting information in case of a radioactive release from a nuclear power plant in Switzerland. On the other hand, the model input over the Swiss Plateau is generated by a dedicated network of surface and upper air observations including remote sensing instruments (wind profilers and temperature/humidity passive microwave radiometers). This network is built upon three main sites ideally located for measuring the inflow/outflow and central conditions of the main wind field in the planetary boundary layer over the Swiss Plateau, as well as a number of surface automatic weather stations (AWS). The network data are assimilated in real-time into the fine grid NWP model using a rapid update cycle of eight runs per day (one forecast every three hours). This high resolution NWP model has replaced the former security tool based on in situ observations (in particular one meteorological mast at each of the power plants) and a local dispersion model. It is used to forecast the dynamics of the atmosphere in the planetary boundary layer (typically the first 4 km above ground layer) and over a time scale of 24 h. This tool provides at any time (e.g. starting at the initial time of a nuclear power plant release) the best picture of the 24-h evolution of the air mass over the Swiss Plateau and furthermore generates the input data (in the form of simulated values substituting in situ observations) required for the local dispersion model used at each of the nuclear power plants locations. This paper is presenting the concept and two validation studies as well as the results of an emergency response exercise performed in winter 2009.

Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study.

Background Previous studies on childhood cancer and nuclear power plants (NPPs) produced conflicting results. We used a cohort approach to examine whether residence near NPPs was associated with leukaemia or any childhood cancer in Switzerland.Methods We computed person-years at risk for children aged 0–15 years born in Switzerland from 1985 to 2009, based on the Swiss censuses 1990 and 2000 and identified cancer cases from the Swiss Childhood Cancer Registry. We geo-coded place of residence at birth and calculated incidence rate ratios (IRRs) with 95% confidence intervals (CIs) comparing the risk of cancer in children born <5 km, 5–10 km and 10–15 km from the nearest NPP with children born >15 km away, using Poisson regression models.Results We included 2925 children diagnosed with cancer during 21 117 524 person-years of follow-up; 953 (32.6%) had leukaemia. Eight and 12 children diagnosed with leukaemia at ages 0–4 and 0–15 years, and 18 and 31 children diagnosed with any cancer were born <5 km from a NPP. Compared with children born >15 km away, the IRRs (95% CI) for leukaemia in 0–4 and 0–15 year olds were 1.20 (0.60–2.41) and 1.05 (0.60–1.86), respectively. For any cancer, corresponding IRRs were 0.97 (0.61–1.54) and 0.89 (0.63–1.27). There was no evidence of a dose–response relationship with distance (P > 0.30). Results were similar for residence at diagnosis and at birth, and when adjusted for potential confounders. Results from sensitivity analyses were consistent with main results.Conclusions This nationwide cohort study found little evidence of an association between residence near NPPs and the risk of leukaemia or any childhood cancer.

Characterization Factors for Thermal Pollution in Freshwater Aquatic Environments

To date the impact of thermal emissions has not been addressed in life cycle assessment despite the narrow thermal tolerance of most aquatic species. A method to derive characterization factors for the impact of cooling water discharges on aquatic ecosystems was developed which uses space and time explicit integration of fate and effects of water temperature changes. The fate factor is calculated with a 1-dimensional steady-state model and reflects the residence time of heat emissions in the river. The effect factor specifies the loss of species diversity per unit of temperature increase and is based on a species sensitivity distribution of temperature tolerance intervals for various aquatic species. As an example, time explicit characterization factors were calculated for the cooling water discharge of a nuclear power plant in Switzerland, quantifying the impact on aquatic ecosystems of the rivers Aare and Rhine. The relative importance of the impact of these cooling water discharges was compared with other impacts in life cycle assessment. We found that thermal emissions are relevant for aquatic ecosystems compared to other stressors, such as chemicals and nutrients. For the case of nuclear electricity investigated, thermal emissions contribute between 3% and over 90% to Ecosystem Quality damage.

Comparison of 3D reaction rate distributions measured in an Optima2 BWR assembly with MCNPX predictions

As part of a joint research programme between the Paul Scherrer Institute (PSI) and swiss nuclear, with the co-operation of the Leibstadt nuclear power plant in Switzerland and fuel suppliers Westinghouse Sweden, measurements and calculations have been made of the axial and radial distributions of fission and 238U capture rates in the fuel rods of a Westinghouse SVEA-96 Optima2 boiling water reactor assembly. The measurements, made in the zero-energy research reactor PROTEUS at PSI, have been compared with calculations carried out using the Monte Carlo code MCNPX. The results reported are for the regions near the ends of the part-length fuel rods, which are a feature of SVEA-96 Optima2 assemblies. The sudden increase in moderation above the ends of the part-length rods leads to power peaking in the adjacent rods. Careful attention needs to be given to this phenomenon in the deployment of such fuel, the present paper providing experimental evidence for the ability of a stochastic code to predict such effects.

Operational experiences in BWR spent fuel transport and storage systems for KKL: TN52L, TN97L and TN24 BHL

The Leibstadt (KKL) nuclear power plant in Switzerland has opted to ship spent fuel to the central facility at Zwilag for interim storage. In the mid-1990s, Cogema Logistics was contracted by KKL for the supply of the TN52L and TN97L transport and storage casks for boiling water reactor (BWR) fuel types. In 2003, KKL also ordered from Cogema Logistics the supply of six TNTM24 BHL transport and storage casks. This paper shows how all the three cask designs have responded to the needs of KKL to ship and store BWR spent fuel. In addition, it highlights the already significant operational feedback about the TN52L and TN97L casks by the operators of KKL and Zwilag.