Galactic cosmic ray intensities (GCRs) observed by five neutron monitors (NMs) have been used to study cosmic ray modulations between 1971 and 2007. The influence of interplanetary magnetic polarity (IMF) states has been studied for the A < 0 and A > 0 epochs. A comparison of the spectra for both positive IMF polarities indicated different solar origins. The spectra have different power amplitudes and most peaks of different locations. In addition, the differences in the cosmic ray modulations, conditions for solar activity minima and maxima periods are probably associated with the influence of drift effects. The observed differences are related to the 22-year cycle in heliospheric modulations of cosmic rays, leading to the different shapes of CR maxima and the hysteresis effect. Accordingly, drift effects dependent on the polarity of the global solar magnetic field may play a significant role in the observed differences between maxima and minima periods. The drift mechanism is enhanced during periods of low to moderate SA, i.e., around solar cycle minima, during negative polarity periods, when A < 0.
The analysis of research reactor transients depends on the kinetic parameters (i.e. effective neutron generation time Λ∗ and the effective delayed neutron fraction βeff).In this work we will calculate these parameters using the MCNP code. Effects of burn up and of Be reflector and cobalt irradiation device on kinetic parameters were also studied using the MCNP code. The results were compared with reported values. The calculations were performed for the start-up core configuration (reference core configuration) at different burn up steps with equilibrium concentration and with zero concentration of Xe, and repeated for the sixth core configuration (core configuration during the study).
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