Imaging and location of fast neutron emissions by real-time time-of-flight

Lead Research Organisation: Lancaster University
Department Name: Engineering

Abstract

The proposed research comprises a study into a different way in which to use neutrons to characterise nuclear environments. The proposed project is a collaboration led by the Department of Engineering at Lancaster University with expertise from the Culham Centre for Fusion Energy. Neutrons make up approximately half of the subatomic particles that constitute the nuclei of matter around us. They are uncharged and therefore do not interact strongly with the environment in comparison with other common forms of radiation such as gamma rays, protons electrons etc. However, they are emitted as a result of nuclear reactions in reactors and particle accelerators and are thus present in many environments associated with truly global applications of nuclear technology such as nuclear power, propulsion, the prevention of nuclear proliferation and nuclear medicine. Fortunately, because fast neutrons do not travel at the speed of light in the same way that gamma rays do, they are readily separated from gamma rays on the basis of how long they take to travel a set distance. This approach is widely referred to as 'time-of-flight' (ToF).

Exploiting the difference between the speed of fast neutrons and gamma rays on the basis of their time-of-flight is currently limited to rather esoteric applications such as finding the energy of neutrons at standards laboratories and particle accelerator facilities, for example at NPL and nTOF (CERN), respectively. Whilst this application is very important in the specific field of radiation metrology, wider application of the technique to infer the location of radioactive substances and the distribution of radiation emissions in industry and medicine has not yet been achieved.

The focus of this proposal is to invert the widely-accepted ToF approach referred to above (by which the usual objective is to estimate the energy of neutrons) to see if we can locate and image the origin of fast neutrons in environments where they arise. The hypothesis at the focus of this proposal is that, based on our prior knowledge of the energy distribution of neutrons in typical environments of interest (such as power reactors and medical facilities), is to determine whether it is possible to obtain an estimate of the distance from the site of detection to the site of neutron emission. This information might then be used to locate and potentially image a neutron-emitting system or substance; an Engineering use of the time-of-flight method that has not been explored before. This research will thus determine whether time-of-flight, performed digitally and in real-time, can be used to indicate the location and to potentially image a source of neutron radiation. The key objective of this research is to determine whether the ToF approach can be applied as an Engineering capability that will have a range of potential applications in industry and medicine. These include for example: preventing the theft of nuclear materials (nuclear safeguards), nuclear reactor characterisation, nuclear security and the characterisation of neutron fields that result from the use of protons in cancer therapy.

Planned Impact

We envisage six areas of impact: nuclear security & safeguards; proton therapy; 3He replacement; nuclear reactor monitoring & accident recovery; nuclear decommissioning and neutron metrology and fusion. These are all of exceptional relevance at the current time for both the UK research community, UK society and UK industry & commerce. They are also areas that are, without exception, of relevance to the global community in this field at the present time.

For example:

- In the nuclear security and safeguards area significant impact is plausible in the area of improved monitoring and characterisation for nuclear materials. With many more power reactors being built in a widening international nuclear power community, mixed with a variety of reactor designs and new concepts such as small modular reactors etc., there is an increasing need to safeguard the international transfer of fuel against the risk of proliferation. This research will advance the characterisation of fast neutrons from fission reactions which are often the sole basis for the detection of these materials via, for example, 240Pu spontaneous fission or stimulated fission in 235U.

- Proton and hadron therapy are highly topical at the present time due to the significant potential they hold for the treatment of cancer, especially in children. However, the high-energy protons used in these therapies can yield a significant neutron flux that, if unchecked, can be a source of dose to both patients and clinicians. This research will advance the spatial characterisation of fast neutrons in these environments.

- Virtually all helium-3 detectors currently in use in the detection of neutrons for security, safeguards and plutonium stockpile monitoring will have an alternative technology identified as a replacement due to supply constraints on 3He; this research will impact this need. This area clearly has significant commercial and societal relevance, especially in the UK as we hold the largest civil plutonium stockpile currently reliant on 3He monitoring.

- Reactor monitoring and accident recovery has been cast into the public eye relatively recently as a result of the effects of the earthquake and subsequent Tsunami on the Fukushima Daiichi reactors in Japan. This research will advance current capabilities in the spatial characterisation of fast neutron fields that is highly relevant to monitoring containment environments in both pressurised water reactors and boiling water reactors. It is also relevant to reactor monitoring during all anticipated phases of operation i.e. steady-state operation, shutdown and post-accident.

- Nuclear decommissioning remains an important and significant requirement for many countries that have legacy facilities from past nuclear activities. This research will benefit decommissioning activities where the presence of nuclear material is suspected; for example where fuel waste residues are present in process systems and aged reactor systems.

- Neutron metrology and fusion are important areas for this research since it builds directly on current neutron metrology capabilities and offers the potential for a new metrology service by which environments associated with these requirements might be characterised in terms of the neutron distribution in space as well as energy.

Publications

10 25 50
 
Description We have discovered important issues associated with the stability of the detector systems of relevance to this project when used in large numbers and as arrays.
We have now identified the major limitations on the processing speed of the digitisers and the potential influence these have on using the apparatus for time-of-flight.
We have perfected the ability to image sources of neutrons and gamma rays, at the same time, on the basis of the time-of-flight relationship between these radiations, s postulated in the original research proposal. This approach uses just two detectors, as opposed to an array, and is accurate to the level of +/- few centimetres which has significant potential for applications in reactor diagnostics, nuclear security and decommissioning of nuclear installations.
Exploitation Route They have been published and are being considered by other users. We have also identified a key measurement opportunity with MAST at CCFE (UKAEA, Culham) as this goes live later this summer and can then be characterised by the fast neutron TOF approach; the development of the data processing electronics has been adopted by another researcher at Lancaster for applications in neutron spectrometry; a paper has been accepted for publication at the PHYSOR2020 conference in Cambridge, April 2020 which will further highlight the outcomes of the funding and advertise its potential use to others. The work will be taken forward by the EPSRC 'ALACANDRA' responsive-mode project, led by M Joyce (not included as further funding as yet to start - April 2021 - and it is not yet shown on the Researchfish database).
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Security and Diplomacy,Transport

 
Description We have learnt, from our liaison with Oak Ridge National Laboratory, of a novel means for the measurement of plutonium for use in nuclear safeguards and this has precipitated a collaboration planned with the ESRF. Our measurements at Lancaster, which have been used to characterise the 252Cf neutron source, have been used by UKAEA Culham to testing optimisation processes for refining the location of the source. Our findings were published at the International Conference on Advancements in Nuclear Instrumentation Methods and their Applications (ANIMMA) in Porteroz, Slovenia, June 2019 which won the conference prize for best poster. Further, they have inspired a subsequent, responsive-mode EPSRC proposal that has been successful under M Joyce's leadership and which will start in April 2021.
Sector Energy
 
Title TOF mixed field source imaging 
Description By measuring the time between a gamma ray emitted from the fission in 252Cf and the correlated neutrons that follow, with a variety of detectors placed at different positions, a map can be built in terms of the distance of the source from an array of detectors and the location of the source can be inferred. 
Type Of Material Technology assay or reagent 
Year Produced 2019 
Provided To Others? Yes  
Impact Too early. 
 
Description Collaboration on the optimisation of mixed-field source localisation TOF data 
Organisation Culham Centre for Fusion Energy
Country United Kingdom 
Sector Academic/University 
PI Contribution We provided 252Cf source time-of-flight localisation data to modelling experts at Culham.
Collaborator Contribution Culham processed the data to optimise the location of the source based on 3D Chisq minimisation.
Impact 'Fast neutron time-of-flight source localisation using organic scintillators', V. Astromskas, S. C. Bradnam, L. W. Packer, M.D.Aspinall and M. J. Joyce, under correction. 'Experimental validation of real-time neutron time-of-flight imaging in 3-D space using a multi-element scintillator detection system', V. Astromskas, S. Bradnam, M. Aspinall, L. Packer, M. Gilbert, M. J. Joyce, Paper #07-1453 (poster), 6th International conference on Advancements in Nuclear Instrumentation Measurements Methods and their Applications (ANIMMA), Portorož, Slovenia, June 2019. 'Development of response modelling and imaging applications using Monte-Carlo simulation of time-of-flight neutron detection systems', Lee W. Packer, Mark R. Gilbert, Zamir Ghani, Vytautas Astromskas, Malcolm J. Joyce, accepted to PHYSOR2020, April 2020, Cambridge.
Start Year 2019
 
Description Equipment sharing with UKAEA Culham 
Organisation EURATOM/CCFE Fusion Association
Country United Kingdom 
Sector Academic/University 
PI Contribution We have loaned some of the ADRIANA equipment to users at the CCFE fusion site and this is being investigated for use in characterising MAST. Some money was made available to support the costs of a placement student to assist with this deployment in the summer of 2017.
Collaborator Contribution CCFE at Culham supervised the placement activity and are working on developing the use of the equipment for the MAST application.
Impact For example: 'In-situ detection of plutonium in soil', TIGHE Christopher, ANDREW Jeremy and JOYCE Malcolm, oral paper #225, IEEE ANIMMA, Liege, Belgium, June 2017.
Start Year 2017
 
Description Research collaboration with Oak Ridge National Laboratory, Tennessee United States 
Organisation Oak Ridge National Laboratory
Country United States 
Sector Public 
PI Contribution The equipment made available via the ADRIANA grant has been transported to Oak Ridge National Laboratory for joint, collaborative measurements to be made there in their laboratories. Our contribution was the loan of the equipment and the secondment of researchers to ORNL in the US for 2 weeks.
Collaborator Contribution The partners (ORNL) made available their laboratories and their expertise and radioactive materials for analysis and use.
Impact For example: 'Real-time determination of Rossi-? distribution, active fast neutron multiplicity, neutron angular distribution and neutron spectrum using organic liquid scintillators', paper #2434, N-09-2, R. Sarwar, V. Astromskas, C. H. Zimmerman, S. Croft and M. J. Joyce, IEEE NSS 2017, Atlanta.
Start Year 2016
 
Description 'Real time double-dealing in fast neutron assay', Georgia Institute Tech. (US, 2017). 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact An invited talk at the Georgia Institute of Technology to research groups there, i.e. academic researchers, undergraduate and postgraduate students.
Year(s) Of Engagement Activity 2017
 
Description 141. 'A comparison of high-resolution gamma-ray spectroscopy and accelerator mass spectrometry for environmental assay of plutonium', M. J. Joyce, Invited paper, NSS-WS1 I - Instrumentation and Measurement in Nuclear Media workshop, IEEE Nuclear Science Symposium and Medical Imaging Conference, Sydney, November 2018, #3054. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited presentation on research sponsored by RAIN at the IEEE Nuclear Science Symposium, Sydney, Australia.
Year(s) Of Engagement Activity 2018
URL https://www.eventclass.org/contxt_ieee2018/online-program/session?s=NSS-WS1+I
 
Description 268. 'Instrumentation approaches to radioactivity assessments in decommissioning, environmental analysis and materials assay', Invited talk, IEEE NSS workshop - Advanced Measurements and Instrumentation for/in Research Reactors, InMe-01, Atlanta (US, October 2017). 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited paper to an official workshop of the IEEE Nuclear Science Symposium/Medical Imaging Conference, Atlanta, GA, USA.
Year(s) Of Engagement Activity 2017
URL http://ewh.ieee.org/soc/nps/nss-mic/2017/Workshops.html#NI
 
Description 269. 'A short history of real-time, fast neutron detection and its applications', Paul Scherer Institute (Switzerland, December 2017). 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact An invited talk at the Paul Scherrer Institute on neutron assay and its relevance to autonomous assessments.
Year(s) Of Engagement Activity 2017
 
Description Chair of conference session at the IEEE Nuclear Science Symposium, Sydney, Australia, November 2018. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I was co-chair of the Nuclear Instrumentation and Measurements for Reactors session at the IEEE NSS-MIC in Sydney, Australia in November 2018.
Year(s) Of Engagement Activity 2018
URL https://www.eventclass.org/contxt_ieee2018/online-program/session?s=N-09#s42
 
Description INVITED paper #06-1412, 6th International conference on Advancements in Nuclear Instrumentation Measurements Methods and their Applications (ANIMMA), Portorož, Slovenia, June 2019. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact An invited talk delivered to the ANIMMA 2019 conference in Slovenia.
Year(s) Of Engagement Activity 2019
 
Description INVITED paper, Workshop #1, 17th June 2019, 6th International conference on Advancements in Nuclear Instrumentation Measurements Methods and their Applications (ANIMMA), Portorož, Slovenia. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact I gave an invited keynote to this workshop at the international ANIMMA conference: 'Real-time, combined neutron/?-ray imaging, radiography and tomography of sources and systems'.
Year(s) Of Engagement Activity 2019
 
Description Invited talk: 'Real-time, fast neutron detection and its applications', Reactor Centre, Jošef Stefan Institute (Slovenia, 2018). 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact An invited talk given to employees and researchers at the Slovenian reactor institute, including people from the Japanese Atomic Energy Agency and the Japanese National Maritime Research Institute.
Year(s) Of Engagement Activity 2018
 
Description UK Government's Nuclear Innovation Research Advisory Board, NIRAB. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact I am a serving member of the UK Government's Nuclear Innovation Research Advisory Board, NIRAB.
Year(s) Of Engagement Activity 2018
URL http://www.nirab.org.uk/about-us/about-nirab/