NANODOT+: NANOmaterials for the radiometric Detection Of Tritium - PLacement with USers

The Nuclear Power Industry is part of the utilities infrastructure that guarantees our energy supply. It has substantial environmental management responsibilities - especially pertaining to its statutory waste management responsibilities. Amongst these, UK Nuclear SiteOperators are required to produce annual reports summarising the previous year's discharges and results from the environmental monitoring programme. The dominant radioactive contaminants include Sr-90, Cs-137, Tc-99 and tritium (T), all beta emitters. Of these, T presents particular issues.

Tritium (T) is a radioactive isotope of hydrogen made during the routine operation of nuclear reactors. This can give rise to waterborne tritium in, inter alia, spent fuel (SF) cooling ponds and SF processing & waste treatment facilities - all potential sources of leakage to the ground and beyond. Waterborne T is most commonly present in groundwater in the form of tritiated water, HTO. As T is an isotope of H, HTO behaves indistinguishably from H2O and so is highly mobile in the environment- its migration rate being identical to the velocity of groundwater due to the HTO/H2O equivalency. This also makes HTO highly mobile in human tissue, with associated health risks - the WHO limit for T in drinking water is <10 kBq/L. Additionally, tritium is a concern to many industries i.e. sea fisheries often command extensive clean-up activities even where T is present at less than accepted statutory limits.

Thus there are pressing health & safety and economic needs for fast, accurate & precise analysis of T in the terrestrial and marine environments around nuclear sites and in the effluents and wastes arising from their operation/decommissioning. Tritium decays with a soft beta emission making rapid radiometric detection in the field very difficult. However Lancaster University (LU) have, for the last 5 years, been working in collaboration with Radiometric Instrumentation SME Hybrid Instruments on the development of a novel device for the measurement of tritium in groundwater that addresses all of these needs - the NANODOT Instrument (NANOmaterials for radiometric Detection Of Tritium).

NANODOT exploits recent advances in nanomaterials fabrication to create solid scintillators modified with nanoporous layers of palladium. By simple electrolysis, tritium may be selectively extracted from aqueous sample matrices and concentrated in the palladium layers. The beta particles emitted from the tritium then excite the scintillator which emits a photon. This is counted by an attached photomultiplier tube, so providing a measure of the tritium in the original sample. Beginning with a NERC PhD studentship for researcher Ghebrehiwot Berhane and subsequently further funded by awards from NERC and InnovateUK, NANODOT has been taken from Technology Readiness Level 1 (TRL1, feasibility) to TRL6 (full system demonstration in relevant environment) in just 5 years. Dr Berhane has led the research throughout.

This proposal, NANODOT+ (NANODOT - PLacement with USers) is for Dr Berhane to undergo 3 innovation placements, with a total length of 1 year, in which the applications of the NANODOT instrument are explored in (i) NNL, a HMG-owned business that provides technical support to Sellafield in meeting its statutory environmental radioactivity monitoring obligations and (ii) two SMEs in the Sellafield supply chain who also support them in discharging these obligations, LabLogic and Hybrid itself.

The outputs of the placements will be a series of case studies showing how the NANODOT instrument may support the host organisations in their T monitoring needs. Initial focus will be on T measurement in real groundwater samples - so taking NANODOT to TRL7, prototype demonstration in an operational environment - although this initial focus will subsequently expand to explore supporting other waste management needs (e.g. leak detection, effluent monitoring).