Development of mixed field radiation detection techniques for oil and gas well logging.

The NuSec-mediated workshop in January 2018 produced a report in which the need to develop alternative detection and data interpretation methods in well logging was highlighted.
The detector development group at the University of Sheffield has a long track record of detector development for a range of particles including muons, neutrons and gammas. Our recent STFC-supported work on the development of neutron-sensitive detectors for water content monitoring has resulted in new expertise in the fabrication of neutron- sensitive foils being developed in house. This new capability sits alongside previous expertise in prototyping borehole detectors for CCS monitoring. Furthermore, due to a long-standing relationship with LabLogic we have access to a scintillator fabrication facility enabling short turnaround prototyping and development cycles. Along with our range of neutron sources (pulsed DT, AmBe, 252Cf) this places us in a unique position to be able to develop low-cost plastic scintillator and neutron-sensitive foil based detection systems for application in borehole configurations.
Via the studentship, we intend to explore the possibility of using scintillator blocks doped with different materials to produce finely segmented radiation detectors that can fit down a standard borehole. There are several advantages to this approach over standard methods, e.g.:
- use of a single detector that covers mixed fields using position-sensitive detection/ coincidence. On-site expertise in many different detector types is thus not required;
- deployment of a finely segmented detector made of many similar stacked "modules"
or "blocks" means the system has built in redundancy;
- the time from initial neutron generator pulse to detection of neutrons/gammas can
provide additional fine grained information not available when using radiological sources.
A further issue with current well logging technologies, as noted in papers, is the analysis of data. Gamma logs, e.g., are used as almost a qualitative measure. Similarly, neutron porosity measurements require further calibration to be effective. The inclusion of pulsed generators and associated particle detection yields supplementary information, however, this is at the cost of additional processing time and training. A solution for this is to use machine learning to extract quantities of interest, e.g. the total detected neutron/gamma counts from a borehole detector observed in a gated window after the initial generator pulse would serve as suitable input to a multivariate analysis (MVA) method such as a neural network. Such an MVA could be trained, via simulations, to extract relevant quantities of interest. These simulations could then be experimentally validated using a scenario in which a detector is placed in parallel with the Sheffield DT source and surrounded by volume of material (e.g. soil and/or rock) of known properties.
Whilst the borehole detector is the primary hardware focus of this application it is acknowledged that the fusion of plastic scintillator with neutron-sensitive foils may afford opportunities in other application areas such as environmental monitoring and the nuclear industry, where alternative format detectors employing the same underlying technology may be of interest.
The project output is therefore expected to comprise an operational borehole detector prototype with empirical comparisons with "standard" (e.g. 3He) methods as well as MVA-based software tools for signal discrimination.

Maximising impact is at the heart of the NuSec network, through the use of a range of funded impact activities that lie at the heart of the network's objectives. In this extension proposal we will continue to identify pathways to impact across the broad range of network activities.

Here we describe the wider impact that the NuSec network has achieved during Phase 1, and will continue to deliver in Phase 2.

1. The Beneficiaries
(i) Society - the nuclear security agenda is critical to national safeguarding and to the protection of society. A strong engagement between government agencies, academic and industry generates a benefit for all of society. A good example from Phase 1 of the network was our NuSec workshop on alternative technologies for the oil well logging industry. This brought together ~30 senior oil industry experts from Europe and US for a 2 day workshop at the Institute for Advanced Studies at Cambridge University.
(ii) People - the network continues to provide cross-fertilisation of technical expertise between research disciplines and the integration of the various stakeholder communities. Those engaging with the network extend their skills set and experience. The network offers grants to support a wide range of professional and researcher development skills, and to provide technical training opportunities to benefit researchers.

2. How the Network Activities will deliver Impact
The network delivers impact directly through its programme of regular and occasional activities.

Developing Strategic Partnerships
The network's primary objective has been to establish a forum for discussion and collaboration between the academic, industrial and defence sectors. This has accelerated the development of a strong research community in the nuclear science area, and has acted to broker interactions and partnership between the academic and MoD/Home Office communities. Our strategic partners each offer a unique input into the programme and are fully involved with the regular network meetings and technical workshops. Both the network's Management Group (MG) and End User Panel (EUP) are made up of key stakeholders who monitor the network's progress towards developing strategic partnerships. The independent Steering Board, representing the interests of the stakeholder groups, ensures the development of partnerships through these various activities.

Technology Development
The network will continue to receive direct funding from AWE to support pilot studies and small proof of concept studies. These are challenge-led projects that are focussed on the requirements of these government agency stakeholders. In this way the network develops technology demonstrators that address government requirements, for example as defined by the national counter terrorism strategy CONTEST which addresses the "...highest impact terrorist risks including even nuclear materials..." In Phase 1 of the network, NuSec awarded 15 of these pilot projects to UK Universities, which addresses technical challenges identified by the End Use Panel.

Dissemination activities
All network outputs are unclassified, and the majority are publicly available and openly disseminated, including technical workshop presentations, results from pilot studies, scoping documents and position papers. Dissemination uses a dedicated website to promote the network activities and outputs, and the University's Surrey Research Insight digital open access repository to store and disseminate network outputs and documents. The network showcase meeting will publicise the network outputs to a wider audience.

Supporting Researcher Engagement: The network will provide a series of opportunities for researchers to develop their technical skills and knowledge.

Full details are given in the separate Pathways to Impact Statement