Research into ground-breaking, cost effective and faster techniques for decommissioning nuclear plants has earned a Lancaster University professor and his team a national industry award.
Head of Engineering Professor Malcolm Joyce received the Institution of Civil Engineers (ICE) James Watt Medal for the best paper published by the journal ‘Energy’.
The winning paper, Finding the Depth of Radioactivity in Construction Materials, was written by Professor Joyce together with Lancaster University Researcher Jamie Adams, Principal Scientist at Dounreay Site Restoration Ltd John Heathcote and Director of Cockermouth-based imaging technology company Createc Matthew Mellor.
The award was presented by ICE President Geoffrey French at the Institution’s ‘Awards for Papers’ ceremony, held at their Westminster headquarters. ICE Publishing receives more than 1000 new paper submissions per year.
The paper highlights a key challenge in the disposal of nuclear facilities is how to assess the extent of likelihood of radioactive contamination in construction materials and the ground.
The winning team looked at techniques to determine the depth of contamination by examining the energies of radiation emitted from the contaminated materials without the need to bore through a structure or destroy it in the process.
Currently, core drilling is in widespread use to identify the precise location of contamination. The process generates waste, presents a risk of contamination to workers carrying out the drilling and can also miss adjacent contamination.
Professor Joyce explains: “One of the silver linings in this cloud of potentially harmful radioactive contamination is that the vast majority of isotopes decay rapidly to the point at which they pose no harm.
“Of those that remain, caesium-137, isotopes of heavy elements and, to a lesser extent, cobalt-60, pose a challenge, justifying long-term care and maintenance but which are amenable to the technique described in our work.”
Some isotopes can be transported by water so, as a result of spills and leaks in buildings and the surrounding ground, these substances can pose a restriction on the ease with which structures and land are decommissioned.
They can represent significant challenges when decommissioning old facilities at nuclear power and process plants.
The Lancaster research, which focused on caesium, examined a technique developed to estimate the depth of contamination in silica-based materials such as sands, soils, concrete and hard core, non-destructively and non-invasively. The technique is based on the influence that the contaminated material has on the radiation emitted by the contamination.
The engineers used bespoke, sand-filled ‘phantoms’ or models, more often used in medical radiotherapy contexts, to study the caesium placed at differing depths.
The ‘phantoms’ replicate a small section of the concrete building material under scrutiny without the need to produce large amounts of radioactively contaminated material. Calibrated sliders were used to place the contaminated material in the sand.
At each depth, gamma rays were recorded at an external face of the phantom using a cadmium telluride detector.
Electromagnetic radiation peaks were monitored to determine energy sources and Principal Component Analysis (PCA), a long-established analytical method to extract salient patterns in multivariable datasets, was used.
“There are at least two possible applications of this technology,” adds Professor Joyce. “Localised radioactivity in natural environments resulting from nuclear accidents and within solid concrete structures where contamination may have either diffused through the concrete or has penetrated along construction joints.”
The next stage, to support the laboratory to site transfer of the technique, will be to take the tests out to actual decommissioning sites.