In this paper we establish a three-dimensional (3D) numerical simulation model of domestic SiGe heterojunction bipolar transistor (SiGe HBT) by using technology computer aided design tools, to study the bias effect on single event effect (SEE) of SiGe HBT. The response relationship between SEE and the bias of SiGe HBT is identified based on the analyses of transient current peak and charge collection of each terminal. The results show that the worst biases for SEE are different for different terminals. Even for the same terminal, the worst biases for charge collection and transient current peak are different. This phenomenon is caused mainly by the influence of applied electric field and the change of carrier transport mode.

Since the coolant leaving the SCWR core contains an assortment of radioisotopes, it is necessary to identify appropriate materials for shielding ex-core components. Photon attenuation characteristics, photo-neutron production capacity and cost effectiveness of candidate materials were investigated in this study. WinXcom computer code was used for attenuation studies while other properties were surveyed in literature. High Z materials (lead and tungsten) show excellent gamma attenuation properties however they are expensive and could be vulnerable to photo-neutron production if used for shielding turbines or the pressure vessel exit steam-line. Barite concrete which is a moderate attenuator could also be susceptible to photo-neutron production if used for shielding components with high Nitrogen-16 activity. Heavy concretes with iron aggregates on the other hand show fair attenuation and are not susceptible to photoneutron production in the energy range of photons released from reactor water. In terms of cost, concretes are cheaper and easy to fabricate compared to high Z materials especially when a shield of intricate shape is required. Depending on the available space for the shield, heavy concretes would be the most appropriate materials for shielding the SCWR turbine and balance of plant. However in case of space limitation, their attenuation capacity can be enhanced by introducing high Z materials in reasonable proportions.

Coincidence summing effects arises when two or more γ-rays are emitted in a cascade from an excited nucleus and are detected within the resolving time of the detector. Without correction of such effects, the activity of radionuclides cannot be accurately determined. For the correction of summing effects, a new simulation method in GEANT4 was established to simulate the coincidence summing correction factors (CSF simu ) for an HPGe detector. In the simulation, a cylindrical and Marinelli beaker source containing several radionuclides were used with different volumes, covering the energy range from 59.50 keV to 1836.01 keV. In the case of volumetric sources, the coincidence summing correction factors for two nuclides ( 60Co and 88 Y) were calculated from the efficiencies at different points throughout the source volume. The dependence of the coincidence correction factor on the sample density was also carried out for some particular nuclide and photon energy. The same methodology of coincidence summing correction factor was applied for the complex decay scheme of 133 Ba and 152 Eu obtained a good agreement with the experimental results.

Mechanism of irradiation effects is analyzed for floating gate read only memorie s (ROMs). Phenomena in experiments are reasonably explained. It is proposed that failures in devices result from oxide trapped charge and interface trapped char ge generated by radiation in memory cells and peripheral circuitry. The neutron, proton and 60Co γ irradiation effects in FLASH ROM and EEPROM a re total dose effects.