A simplified analysis of the Chernobyl accident

We show with simplified numerical models, that for the kind of RBMK operated in Chernobyl: The core was unstable due to its large size and to its weak power counter-reaction coefficient, so that the power of the reactor was not easy to control even with an automatic system. Xenon oscillations could easily be activated. When there was xenon poisoning in the upper half of the core, the safety rods were designed in such a way that, at least initially, they were increasing (and not decreasing) the core reactivity. This reactivity increase has been sufficient to lead to a very high pressure increase in a significant amount of liquid water in the fuel channels thus inducing a strong propagating shock wave leading to a failure of half the pressure tubes at their junction with the drum separators. The depressurization phase (flash evaporation) following this failure has produced, after one second, a significant decrease of the water density in half the pressure tubes and then a strong reactivity accident due to the positive void effect reactivity coefficient. We evaluate the fission energy released by the accident

LONGITUDINAL EVIDENCE FOR DISCREPANT CHANGES IN NEGATIVE AFFECT REACTIVITY AND BLOOD PRESSURE REACTIVITY WITH AGE

Both affective and blood pressure (BP) reactivity are associated with long term risk of chronic disease and mortality. Thus, understanding age-related changes in negative affect and BP responses to everyday demands is vital for promoting healthy aging. However, few studies have examined both psychological and BP reactivity simultaneously, which would provide more comprehensive understanding of regulatory processes at play. For the present study, 232 adults aged 50-70 years were assessed at baseline and 6 years later with ambulatory BP monitoring and momentary electronic diaries. Reactivity coefficients were output from multilevel models and used to test changes in negative affective and ambulatory BP reactivity to task demand, longitudinally. Results indicate that both systolic and diastolic BP reactivity increase with age, while negative affect reactivity does not change with age. Results are discussed in the context of life course theories of role strain and role changes and socioemotional theories of aging.

Quality of life and sexual activity of women suffering from Polycystic Ovary Syndrome (PCOS)

Aim. The aim of this study was to search for a correlation between the quality of life and the sexuality of women with polycystic ovary syndrome (PCOS).Material and methods. The research was made with the use of the WHOQOL)-BREF questionnaire and the FSQ-28 scale. It included 72 women diagnosed with the (PCOS).Results. A better quality of life in the areas of psychology, social and background relations turned out to be to a moderate degree connected with the reactivity increase on the particular sexual reaction stages, excluding the sexual arousal domain. “Pain” and “relations with a partner” domains had a negative correlation with the given domains of the quality of life. The statistically significant correlation p<0.05 was observed between the overall quality of life and the following domains of the sexual response cycle: desire, lubrication, arousal, orgasm, foreplay and the relations with a partner.Conclusions. 1. All domains of the quality of life of women with PCOS are significantly connected with the majority of domains of the sexual response cycle. 2. The domains of the sexual response cycle are significantly differentiated by the sense of the quality of life. The perception of health in that respect is irrelevant.

Some questions on nuclear safety of heavy-water power reactor operating in self-sufficient thorium cycle

In this paper the comparative calculations of the void coefficient have been made for different types of channel reactors for the coolant density interval 0.8-0.01 g/cm3. These results demonstrate the following. In heavy-water channel reactors, the replacement of D2O coolant by H2O, ensuring significant economic advantage, leads to the essential reducing of nuclear safety of an installation. The comparison of different reactors by the void coefficient demonstrates that at the dehydration of channels the reactivity increase is minimal for HWPR(Th), operating in the self-sufficient mode. The reduction of coolant density in channels in most cases is accompanied by the increase of power and temperatures of fuel assemblies. The calculations show that the reduction of reactivity due to Doppler effect can compensate the effect of dehydration of a channel. However, the result depends on the time dependency of heat-hydraulic processes, occurring in reactor channels in the specific accident. The result obtained in the paper confirms that nuclear safety of HWPR(Th) lies on the same level as nuclear safety of CANDU type reactors approved in practice.

Development and Verification of Dynamics Code for Molten Salt Reactors

To perform transient analysis for Molten Salt Reactors (MSR), the reactor dynamics code DYN3D developed in FZR was modified for MSR applications. The MSR as a liquid fuel system can serve as a thorium breeder and also as an actinide burner. The specifics of the reactor dynamics of MSR consist in the fact, that there is direct influence of the fuel velocity to the reactivity, which is caused by the delayed neutrons precursors drift. This drift causes the spread of delayed neutrons distribution to the non-core parts of primary circuit. This leads to a reactivity loss due to the fuel flow acceleration or to the reactivity increase in the case of deceleration. For the first analyses, a 1D modified version DYN1D-MSR of the code has been developed. By means of the DYN1D-MSR, several transients typical for the liquid fuel system were analyzed. Transients due to the overcooling of fuel at the core inlet, due to the reactivity insertion, and the fuel pump trip have been considered. The results of all transient studies have shown that the dynamic behavior of MSR is stable when the coefficients of thermal feedback are negative. For studying space-dependent effects like e.g. local blockages of fuel channels, a 3D code version DYN3D-MSR will be developed. The nodal expansion method used in DYN3D for hexagonal fuel element geometry of VVER can be applied considering MSR design with hexagonal graphite channels.