Advanced Compton-geometry gamma radiation imaging for radionuclide measurement in soils and geomaterials

Lead Research Organisation: University of Liverpool
Department Name: School of Engineering

Abstract

The continued releases of radioactive material from the earthquake-damaged Fukushima Dai-ichi nuclear power station in Japan, with the risks to water, coastal environments, agricultural land, animals and human health have drawn international concern. The incident, together with the Chernobyl disaster a generation earlier, has highlighted the importance of being able to detect, measure and monitor radiation in our environment. This is no easy challenge - the amounts of radioactivity are often low (relative to controlled medical or industrial settings) or highly dispersed through soils, sediments and water. There is also a considerable background radiation all around us, not only from the legacy of human nuclear technology but from natural minerals, gases (eg. radon, a major problem in some regions), cosmic and solar sources. On the other hand, this radioactivity is used widely by earth and environmental scientists to date rocks, monitor sediment movement and geomorphological changes, or the growth rates and life histories of plants and animals.

If we are to measure environmental radioactivity, not just to help clean-up and recovery after an accidental release but also to monitor sites, prevent releases and support the safe operation and decommissioning of nuclear facilities (as well as support that range of scientific research needs), then we need continuous improvement of sensors which can detect and quantify radiation sources to higher resolution, lower detection thresholds and shorter measurement times.

The current generation of sensors is based on mechanical collimators, a technology similar to the 'pixellated' image sensors in digital cameras, in which the radiation arriving at any point on the surface is used to build up a 2D image of the radiation source. Nuclear physicists at the University of Liverpool have recently developed a new approach for detection of gamma radiation called Compton-geometry imaging. In this approach, two sensors are placed one in front of the other and the measurement is based on the scattering of radiation between them. The technique is powerful because the position of the radiation source is located by mathematically reconstructing the origin of many scattering events, rather than by the physical position of the incident radiation on the collimator surface. This 'electronic' collimation can resolve the position of the source with much greater accuracy and sensitivity than mechanical collimation, has the advantage of being able to locate the source in 3D, and yields smaller, lighter detector equipment with potential savings in measurement time. Currently, only two other research groups in the world are working with this technology.

The objective of this proposal is to understand how this powerful new technology can be optimised for environmental gamma radioactivity measurements. Research so far has focused on the development of prototype Compton cameras for industrial and medical applications, which present very different challenges to the environmental conditions described earlier. By combining a world leading expertise in device development in close collaboration with academic and industry end-users in environmental science and engineering, this Technology Proof-of-Concept proposal aims to develop design criteria, optimised system specifications, and a first prototype for a Compton camera which we intend will set a benchmark for the next generation of environmental radioactivity sensors. Imagine being able to locate a radioactive substance beneath the ground and monitor how it moves with changes in water flow or sediment movement. Or to watch, using a portable device, in real-time how plants and animals take up radioactive materials from contaminated soils and move them into the food chain. Star Trek science? Perhaps for now, but the environmental Compton camera that is the long-term goal of this research project moves us a significant step closer towards that vision.

Planned Impact

Stakeholders and Industry
Stakeholder organisations and groups will benefit from development of new technology areas with potential commercial benefits and the promise of higher-quality data to support more reliable models and decision-making tools to improve the effectiveness of policy decisions and post-incident management. Although the proposed project is short-term and proof-of-concept, there are a range of longer-term beneficiaries whose contact with the project will include:
(i) Project partner NNL (Letter of Support), through close engagement with the development of novel environmental Compton imager technologies; bilateral knowledge exchange to develop mission-specific requirement sets during system specification; and by strengthening knowledge exchange relationships with scientists and engineers at Liverpool;
(ii) A range of National and International statutory nuclear and environmental regulators (e.g. UK NDA, Environment Agency (EA), Japanese Government (through ONDA's ISET-R project) will benefit potentially from the proposed detection methodology to refine and enhance processes and outcomes from emergency planning, routine monitoring (to comply with Environmental permits and statutory regulation) and long term monitoring or remediation; we will engage with these through our investigator and partner networks, including the Liverpool-led ARCoES network which has a strong portfolio of links with stakeholders in the nuclear environmental industry;
(iii) The commercial potential of the prototype Compton imager specification will be evaluated as part of the final reporting to identify any developing commercialisation pathways as they arise.


General Public
The subject of environmental radioactivity in the current climate of proposed nuclear installations and policy development is sensitive, and particularly with our partnership with potential end-users at Fukushima we will take great care to convey clear and coherent information to the public sphere, with the overarching aim of increasing public confidence and understanding of radioactivity in the environment. There is significant opportunity for the technology, objectives and outcomes of this proof-of-concept project to yield high profile stories about the application of UK science and technology in internationally-important environmental settings.

Educational opportunities and outreach
The investigator team has a network of international partners in and exchanges with Japan, the US and Taiwan in nuclear science and engineering which will generate lasting impact in strengthening academic-stakeholder networks around this developing technology. By developing educational experiences around the environmental applications of the Compton sensor technology (for example, 'towards the technology of the Star Trek tri-corder'), we will promote the science of environmental radiography to girls and boys at school level and the wider public, encouraging them into STEM education. The PDRA will be enrolled as a STEM Ambassador and British Science Association member and will take part in outreach and public appreciation of science activities both locally (e.g. Merseyside National Science and Engineering Week) and nationally (e.g., British Festival of Science).

Publications

10 25 50
 
Description The objective is to develop new methods and technologies for environmental sensing of gamma radiation using a Compton-geometry imaging device. The work funded under the grant has produced:
1. the first near-real time timelapse images of radioactive tracer transport through a sand bed using the Compton device.
2. comparative data for radioactive tracer transport and fate in sand and two types of soils, including one from Fukushima, Japan, which clearly demonstrate the relative immobility of the tracer (caesium-137) in clay-rich soils. As well as demonstrating the efficacy of the method, the data are consistent with the main remediation strategy employed at Fukushima (soil top-scraping).
3. new technical methodologies for Compton data processing and calibration to enable, for the first time, direct quantification of source position AND activity from image data. This is a significant advance which provides a strong base for use of the Compton technology in environmental tracer applications, for example monitoring rates of soil-plant transfer of radioactive material under different conditions.
Exploitation Route Through co-I Boston and PDRA Dormand, we are developing collaboration in this area with Berkeley National Lab in the US who do work on similar systems, with different applications.

Through the relationship developed with Japan partner Onda (Tsukuba University), the findings may be applied directly in research projects based in the Fukushima region and monitoring work done by the Japan Ministry of Forestry in support of remediation of the disaster-affected area.

A follow-up PhD student currently in place will pursue both the US and Japan collaborations and extend the range of possible forward options for use of the work funded here.

With the proof of concept for use of the Compton devices for environmental media and flows at bench scale, there is significant potential for integration of this capability into further applied environmental research into radioactivity-affected environments.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Construction,Energy,Environment,Security and Diplomacy

 
Description The PDRA was involved in engagement activities via NERC and the Natural History Museum, supporting the public promotion of science and engineering applied to environmental problems. Through the project, the PI formed collaborative relationships with Tsukuba University, Japan with the following non-academic impacts: - visit to Japanese Ministry of Forestry sites in Fukushima region, dialogue with officials in how to better support environmental monitoring and remeditation using this NERC technology - working with the Japan Nuclear Human Resource Development Network to co-ordinate international training activities benefiting graduate students in both Japan and UK.
First Year Of Impact 2014
Sector Agriculture, Food and Drink,Education,Environment,Government, Democracy and Justice,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal,Policy & public services

 
Description Knowledge transfer to Japan Ministry of Forestry
Geographic Reach Asia 
Policy Influence Type Influenced training of practitioners or researchers
 
Description EPSRC/ESRC Centre for Doctoral Training in Multidisciplinary Risk and Uncertainty (held at University of Liverpool)
Amount £50,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 10/2014 
End 09/2018
 
Title Novel method for direct quantification of source activity and position in Compton data 
Description The work has underpinned development of new data processing algorithms and a calibration procedure combining both computer simulation and physical measurement in order to enable the extraction of data on source activity as well as position from Compton geometry detectors. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact These are still developing, most notably through potential collaborations with Berkeley National Lab, USA, and with a major commercial developer of radiometric instrumentation. 
 
Description UoL-Japan Nuclear Human Resource Development Network 
Organisation University of Tsukuba
Country Japan 
Sector Academic/University 
PI Contribution Visit to Japan to meet with research team at Tsukuba, visit Fukushima field sites, discuss potential research applications and disseminate knowledge on the techniques used.
Collaborator Contribution Hosting including staff time during visit to Tsukuba; dialogue and discussion in respect of research applications; visit to Liverpool to design and development an international training programme between Liverpool and Tsukuba.
Impact Knowledge transfer.
Start Year 2014
 
Description Natural History Museum Science Uncovered 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact PDRA on the project attended the event at the NHM in London

Very busy day, plenty of discussion on the Compton camera technology and potential environmental applications.
Year(s) Of Engagement Activity 2014