We study boron, carbon, nitrogen and oxygen isotopes with a newly constructed shell-model Hamiltonian developed from monopole-based-universal interaction (VMU ). The present Hamiltonian can reproduce well the ground-state energies, energy levels, electric quadrupole properties and spin properties of these nuclei in full psd model space including (0 − 3) ω excitations. Especially, it correctly describes the drip lines of carbon and oxygen isotopes and the spins of the ground states of 10 B and 18 N while some former interactions such as WBP and WBT fail. We point out that the inclusion of 2 ω excitations is important in reproducing some of these properties. In the present (0 + 2) ω calculations small but constant E2 effective charges appear to work quite well. As the inclusion of the 2 ω model space makes rather minor change, this seems to be related to the smallness of 4 He core. Similarly, the spin g factors are very close to free values. The applicability of tensor and spin-orbit forces in free space, which are taken in the present Hamiltonian, is examined in shell model calculations.

The properties of loosely bound proton-rich nuclei around A = 20 are investigated within the framework of nuclear shell model. In these nuclei, the strength of the effective interactions involving the loosely bound proton s 1/2 orbit are significantly reduced in comparison with those in their mirror nuclei. We evaluate the reduction of the effective interaction by calculating the monopole-baseduniversal interaction (VMU ) in the Woods-Saxon basis. The shell-model Hamiltonian in the sd shell, such as USD, can thus be modified to reproduce the binding energies and energy levels of the weakly bound proton-rich nuclei around A = 20. The effect of the reduction of the effective interaction on the structure and decay properties of these nuclei is also discussed.

Neutronic performance is investigated for a potential accident tolerant fuel (ATF), which consists of U 3 Si 2 fuel and FeCrAl cladding. In comparison with current UO 2 -Zr system, FeCrAl has a better oxidation resistance but a larger thermal neutron absorption cross section. U 3 Si 2 has a higher thermal conductivity and a higher uranium density, which can compensate the reactivity suppressed by FeCrAl. Based on neutronic investigations, a possible U 3 Si 2 -FeCrAl fuel-cladding system is taken into consideration. Fundamental properties of the suggested fuel-cladding combination are investigated in a fuel assembly. These properties include moderator and fuel temperature coefficients, control rods worth, radial power distribution (in a fuel rod), and different void reactivity coefficients. The present work proves that the new combination has less reactivity variation during its service lifetime. Although, compared with the current system, it has a little larger deviation on power distribution and a little less negative temperature coefficient and void reactivity coefficient and its control rods worth is less important, variations of these parameters are less important during the service lifetime of fuel. Hence, U 3 Si 2 -FeCrAl system is a potential ATF candidate from a neutronic view.

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