Trend analysis in input data for PSA

The focus of this paper is to form a conclusion on the validity of the postulate on absence of trends in reliability data for Nordic nuclear power plants. Trends in this case imply an increasing reliability parameter with time, corresponding to degradation in component malfunction frequency. A non parametric test method, the Wilcoxon rank sum test, was applied to data sets representing observations of component malfunctions presented in the T-book. Linear trends of magnitude corresponding to that can barely be detected by the test were postulated and added to tabulated reliability parameters. The trend containing parameters were extrapolated in time till today and used in PSA models, comparing results to those obtained while running the same sequences with tabulated parameters. The conclusions of this thesis are that time dependant trends can be observed in reliability data today. These trends are, in one case, insignificant with respect to PSA results. In the other case the trend is most likely decreasing with respect to frequency, yielding a lower malfunction probability, instead of a heightened as was postulated

Desorption of n-alkanes from graphene: a van der Waals density functional study

A recent study of temperature programmed desorption (TPD) measurements of small n-alkanes (CNH2N+2) from C(0001) deposited on Pt(111) shows a linear relationship of the desorption energy with increasing n-alkane chain length. We here present a van der Waals density functional study of the desorption barrier energy of the ten smallest n-alkanes (N = 1 to 10) from graphene. We find linear scaling with N, including a nonzero intercept with the energy axis, i.e., an offset at the extrapolation to N = 0. This calculated offset is quantitatively similar to the results of the TPD measurements. From further calculations of the polyethylene polymer we offer a suggestion for the origin of the offset.Comment: 3 pictures, 1 tabl