The domestically developed prompt fission neutron uranium logging (PFNUL) instrument for uranium exploration represents a significant advancement in China’s deep uranium mining efforts, although it has considerable challenges and complexity. This paper presents the development of a new prompt fission neutron uranium logging instrument (named UNL4) that integrates a domestic D-T neutron generator, two \({^{3}\hbox {He}}\) proportional detectors, a lanthanum bromide ( \(\hbox {LaBr}_{3}\) ) gamma-ray detector, and a digital multi-channel pulse amplitude analyzer. The near \({^{3}\hbox {He}}\) detector is shielded with 1 mm of cadmium (Cd) and 5 mm of high-density polyethylene (HDPE), enabling efficient epithermal neutron detection, whereas the far \({^{3}\hbox {He}}\) detector measures thermal neutrons. A \(\hbox {LaBr}_{3}\) detector is employed for gamma-ray detection, primarily originating from uranium decay. High-speed analog-to-digital converter (ADC) and field-programmable gate array (FPGA) technologies are used to achieve rapid acquisition and transmission of both dual-energy neutron time spectra and gamma spectra. Moreover, this paper proposes a fast signal-shaping method, which reduces the dead time effect in \({^{3}\hbox {He}}\) detectors on neutron time spectra. Experiments conducted in standard model boreholes with varying uranium contents demonstrated a strong linear relationship between the epithermal-to-thermal neutron ratio (E/T) and uranium content, with a fitting coefficient of \(R^2>0.999\) , confirming the accuracy of the instrument. The E/T value repeatability, in both short-term (3.16% RSD) and long-term (1.2% RSD) measurements, showed excellent stability. In addition, the instrument demonstrated good performance at neutron-logging speeds of \(0.3\sim {3\,\mathrm{m/min}}\) (E/T values) and gamma logging speeds of \(1\sim {10\,\mathrm{m/min}}\) . Through measurements in two ore sections of the PU model with uranium contents of 87.1 ppm and 45.6 ppm showed that RD remained below approximately 10% at logging speeds of 0–2 m/s in both cases, satisfying the requirements for engineering applications. This marks the first successful development of a neutron-logging instrument for uranium exploration based on a domestic neutron generator and signifies an important contribution to uranium resource exploration.
