The National Nuclear Laboratory (informally NNL, formerly Nexia Solutions) is a UK government owned and operated nuclear services technology provider covering the whole of the nuclear fuel cycle. It is fully customer-funded and operates at six locations in the United Kingdom. Its customers have included the Nuclear Decommissioning Authority, Sellafield Ltd, Westinghouse, the Health and Safety Executive, the Ministry of Defence, the UK Atomic Energy Authority, VT Nuclear and British Energy. It also has links with academia, including collaborative agreements on waste immobilisation and disposal with the University of Sheffield and on nuclear materials research with the University of Manchester.
A mobile robot platform was developed with on-board, stand-off LIBS and Raman probes as part of a broader system for in situ 'total characterisation' in nuclear environments. This includes gamma spectrometry and 3D imaging via LIDAR and photogrammetry. All characterisation techniques were guided by a 3D point-cloud model generated from the robot's imaging systems, enabling precise positioning near target zones. The LIBS probe operated at a stand-off distance of 10 cm and successfully detected lead in a single shot, with signal quality comparable to benchtop instruments. It also distinguished metals such as stainless steels, nickel, and Incoloy using principal component analysis. The Raman probe used a collimated laser beam and acquired spectra from several metres away. It identified organic materials common in decommissioning environments, including plastics and EDTA, and differentiated concentrations of dibutyl and tributyl phosphate in low-odour kerosene, organophosphates relevant to uranium and plutonium removal. Both probes were tested in a simulated hot cell environment, operating entirely on battery power. Contamination detection of non-radioactive analogues of radioactive decay products like strontium and caesium on stainless steel and cement was demonstrated, supporting clean-up and disposal operations and decision making. Spectral, spatial, and radiological data are integrated into a database that updates a digital twin, enabling layered visualisation in a virtual environment. The robot can be deployed for periodic surveys, such as annual inspections of disused hot cells, to monitor environmental degradation. This data-driven approach supports auditable decision-making for waste disposal and remediation priorities.
Background:Spent AGR (advanced gas-cooled reactor) fuel cladding may suffer from stress corrosion cracking (SCC) during the interim storage period in cooling ponds and compromise the structural integrity of fuel storage. Objective:To better understand the effect of SCC, a new small punch test (SPT) setup was developed in this study that can use a small volume of sample to limit the safety concerns about irradiated materials. Methods:The SPT setup accelerated SCC in a surrogate material 304 stainless steel by introducing a circulation of a heated corrosive solution. Preliminary tests were performed to find the loading and environmental conditions that can develop SCC in the surrogate material. A finite element model was used to estimate the mechanical behaviour of the material during the test. Results:Several samples were tested under different conditions, and SCC and other forms of corrosion behaviours were observed on the samples. The effects of different corrosive environments were obtained by further characterisation including scanning electron microscopy (SEM) and optical profilometry. Conclusions:The experiment demonstrated the new setup can develop SCC from a small volume of sample in a short period of time. Several improvements are listed including extra procedures to enable the experiments on the irradiated fuel materials.
Water present in nuclear legacy materials, such as spent nuclear fuel and fuel element debris, can impact both the chemical and structural stability of these materials. Subsequently, the suitability of these materials for disposal in geological repositories is degraded. Water ingress increases the potential for radioactive material to be dispersed and for neutronic properties to be augmented due to changes in neutron moderation by the constituent hydrogen. This risk necessitates the detection and quantification of water in what can be complex nuclear contexts. Neutron capture γ-ray analysis is of particular interest in this regard: this review provides a summary of the methods and equipment used to apply this to the problem of water assay in nuclear materials. Whilst relatively few directly relevant reports have been published concerning the measurement of water in spent nuclear fuel, the detection of hydrogen and the measurement of its characteristic 2.223 MeV γ-ray following the 1H(n,γ)2H reaction has been studied more extensively. This approach for detecting water in composite materials and its impact on PGAA of other materials is considered. The review concludes with the current applications of the capture γ-ray analysis technique and the potential of its use for water ingress assay nuclear materials at Fukushima Daiichi and Chernobyl.
Measurements of methane (CH4) molecules containing two rare isotopes (13CH3D and 12CH2D2), also termed doubly substituted or “clumped” isotopologues, have the potential to provide two additional isotopic dimensions to help investigate the mechanisms underlying global atmospheric trends in CH4. In this work, we summarise the current state of research on doubly substituted CH4 isotopologues, with an emphasis on compiling results of all relevant work. The database comprises 1475 records compiled from the literature published until April 2025 (https://doi.org/10.5285/51ae627da5fb41b8a767ee6c653f83e6, Defratyka et al., 2025). For field samples, 40 % of records were sourced from natural gas reservoirs, while microbial terrestrial (e.g., agriculture, lake, wetland) samples account only for 12.5 %. Lakes samples contribute 75 % to collected microbial terrestrial samples. There is limited or no representation of samples coming from significant microbial CH4 sources to the atmosphere, like wetlands, agricultural practices and landfills. To date, laboratory experiments were mostly focused on microbial (28 % of samples from laboratory experiments) and pyrogenic (15 %) methanogenesis or anaerobic (16 %), and aerobic (8 %) CH4 oxidation, with only single study of photochemical oxidation via OH and Cl, which constitutes 5 % of the laboratory experiments entries. The distinct ranges of Δ13CH3D and Δ12CH2D2 values measured in these studies suggests their potential to improve our understanding of atmospheric CH4. This work provides an overview of the major gaps in measurements and identifies where further studies should be focussed to enable the highest impact on understanding global CH4.
