Several incidences of nuclear smuggling during the past few decades have raised the demand for the development of a strong “on-site” nuclear forensic infrastructure. High-resolution γ-ray spectrometry (HRGRS) plays an important role in nuclear forensics. However, the existing methodologies, developed primarily for nuclear fuel cycle applications, are relative and rely on the availability of a standard, limiting their use for the absolute assay of special nuclear materials in nonstandard geometry samples with an unknown matrix, which is vital to make a quick “on-site” decision on the severity, potential radiological threat, and intended use of an interdicted package. In this work, a methodology has been developed using HRGRS for quantifying fissile (235U, 239Pu) and other radioisotopes, which is applicable to sealed packages without requiring the knowledge of the sample geometry and the matrices. By combining experiments and Monte Carlo simulations, an iterative methodology has been proposed for “point” to “extended” source absolute efficiency transformation and demonstrated further for the absolute isotopic assay of uranium and plutonium standards, mock-up nuclear forensic samples, and an unknown nuclear material mixture with a nonstandard geometry, compound matrices, and a wide variation in the elemental and isotopic compositions with a view to imitate an “on-site” experience. The present methodology requires an assay time of only a few minutes to an hour and thus promises “on-site” nuclear forensic analysis of suspected flagged packages at borders and ports using high-resolution γ-ray spectrometry. Furthermore, the present methodology is versatile and can also be adopted for wider applications, beyond nuclear forensics.

The objective of the present study is to develop a selective and fast separation media for cesium ions for nuclear fission studies. Here, ammonium molybdophosphate (AMP)-like moieties have been synthesized in situ in a polymer gel with bis[2-(methacryloyloxy)ethyl] phosphate as the monomer. Two types of ethyl] phosphate) and poly (bis[2-(methacryloyloxy)ethyl] phosphate-co-acrylic acid), have been prepared using in situ UV polymerization and characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. The successful formation of the Keggin structure of [PMo 12 O 40 ] 3− in the modified gels has been confirmed by the presence of its distinctive spectral signatures. The AMP-modified gels have been shown to extract Cs + at all of the studied acid concentrations (0.5−8 mol L −1 ) and are found to be selective for Cs + in the presence of other fission products (Ba 2+ , Eu 3+ , Ce 3+ ) and even in the presence of bulk lead nitrate. A selectivity ratio as high as ∼47 for cesium ion with respect to other fission products has been obtained. The kinetics of Cs + ion uptake has been observed to be fast with >90% uptake in ∼8 s, which is almost two orders of magnitude faster than the Cs + adsorbents/extraction methods reported so far to the best of our knowledge. This fast kinetics can be attributed to the hydrophilic and porous nature of the synthesized polymer gel. The AMPmodified gels were successfully tested for the selective and fast separation of short-lived cesium isotopes produced in neutroninduced fission of 235 U and allowed us to experimentally determine the half-life of one of the short-lived isotope of cesium, i.e., 140 Cs, which was found to be in excellent agreement with the literature-reported value (t 1/2 = 63.7 s). This is a significant improvement over previous studies and can have a variety of interesting applications not only in nuclear physics studies but also for the separation processes where Cs + needs to be separated in a minimum time scale.