We study boron, carbon, nitrogen, and oxygen isotopes with a newly constructed shell-model Hamiltonian developed from a 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)$\hbar${}$\omega${} excitations. Especially, it correctly describes the drip lines of carbon and oxygen isotopes and the spins of the ground states of 10B and 18N while some former interactions such as WBP and WBT fail. We point out that the inclusion of 2$\hbar${}$\omega${} excitations is important in reproducing some of these properties. In the present (0+2)$\hbar${}$\omega${} calculations small but constant E2 effective charges appear to work quite well. As the inclusion of the 2$\hbar${}$\omega${} model space makes a rather minor change, this seems to be related to the smallness of the 4He 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.

A new $\alpha$-emitting isotope ${}^{214}\mathrm{U}$, produced by the fusion-evaporation reaction ${}^{182}\mathrm{W}({}^{36}\mathrm{Ar},4\mathrm{n}){}^{214}\mathrm{U}$, was identified by employing the gas-filled recoil separator SHANS and the recoil-$\alpha$ correlation technique. More precise $\alpha$-decay properties of even-even nuclei ${}^{216,218}\mathrm{U}$ were also measured in the reactions of ${}^{40}\mathrm{Ar}$, ${}^{40}\mathrm{Ca}$ beams with ${}^{180,182,184}\mathrm{W}$ targets. By combining the experimental data, improved $\alpha$-decay reduced widths ${\delta }^2$ for the even-even Po-Pu nuclei in the vicinity of the magic neutron number $N=126$ are deduced. Their systematic trends are discussed in terms of the $N_p{N}_n$ scheme in order to study the influence of proton-neutron interaction on $\alpha$ decay in this region of nuclei. It is strikingly found that the reduced widths of ${}^{214,216}\mathrm{U}$ are significantly enhanced by a factor of two as compared with the $N_p{N}_n$ systematics for the $84\le Z\le 90$ and $N<126$ even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the $\pi 1f_{7/2}$ and $\nu 1f_{5/2}$ spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

The N=130 short-lived isotope 223Np was produced as evaporation residue (ER) in the fusion reaction 40Ar + 187Re at the gas-filled recoil separator Spectrometer for Heavy Atom and Nuclear Structure (SHANS). It was identified through temporal and spatial correlations with α decays of 215Ac and/or 211Fr, the third and fourth members of the α-decay chain starting from 223Np. The pileup signals of ER(223Np)–α(223Np)–α(219Pa) were resolved by using the digital pulse processing technique. An α decay with half-life of T1/2=2.15(52100) μs and energy of Eα=9477(44) keV was attributed to 223Np. Spin and parity of 9/2− were tentatively proposed for the ground state of 223Np by combining the reduced α-decay width and large-scale shell-model calculations. This assignment together with the proton separation energy disprove the existence of a Z=92 subshell closure

Neutronic performance is investigated for a potential accident tolerant fuel (ATF), which consists of U₃Si₂fuel and FeCrAl cladding. In comparison with current UO₂-Zr system, FeCrAl has a better oxidation resistance but a larger thermal neutron absorption cross section. U₃Si₂has a higher thermal conductivity and a higher uranium density, which can compensate the reactivity suppressed by FeCrAl. Based on neutronic investigations, a possible U₃Si₂-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, U₃Si₂-FeCrAl system is a potential ATF candidate from a neutronic view.

The properties of loosely bound proton-rich nuclei around $A=20$ are investigated within the framework of the nuclear shell model. In these nuclei, the strength of the effective interactions involving the loosely bound proton $s_{1/2}$ orbit is significantly reduced in comparison with that of those in their mirror nuclei. We evaluate the reduction of the effective interaction by calculating the monopole-based-universal interaction ($V_{\mathrm{MU}}$) 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.