Digital fast neutron assay of uranium

Lead Research Organisation: Lancaster University
Department Name: Engineering


It is well known that uranium has a special property whereby when configured in a particular arrangement and concentration it can sustain a nuclear chain reaction from which a great deal of energy can be derived. It is this property that has led it to be used exclusively throughout the world as the fuel for nuclear power reactors. However, perhaps less well appreciated is the fact that in its raw, un-irradiated state prior to use in a reactor uranium is quite benign in a radioactive sense, emitting relatively little radiation that can be of use in terms of characterisation. This is extremely important because whilst its use in reactors provides much electricity for peaceful uses, it is essential that the amount of uranium in existence is quantified and recorded so that diversion of it for illicit uses is detected. Often an important requirement of this activity is to be able to detect and assess quantities of uranium remotely, without touching it so that commercial activities associated with the production of fuel for reactors etc. can continue unhindered and so that the assessment is quick and effective. The existing detection medium for this purpose is an isotope of helium gas, 3He, which is now in short supply and very expensive which relies on the detection of slow neutrons.

In this project we intend to explore the use of fast neutrons with a different detector technology, organic scintillators, for the assessment of uranium compounds that are highly enriched in 235U and 233U. To carry out this research it is essential that we transport our equipment and expertise to the Oak Ridge National Laboratory in Tennessee in the United States because this laboratory is one of the only places in the world that combines access to these materials with resident world-leading expertise in their assessment. Of particular note to this travel request is that it will enable access to enriched levels of 235U not possible anywhere else combined with the UK's ADRIANA detector system that is also unique in the world. Further it will enable 233U to be explored in quantities not possible anywhere else that is essential to exploring materials security associated with the thorium nuclear fuel cycle.

Planned Impact

We anticipate that this project will result in impact in the following general areas:
- Extending the digital fast neutron prior art to uranium highly-enriched in 235U and the scenarios associated with such materials to bring the fast neutron technique to the attention of experts at the Oak Ridge National Laboratory (ORNL).
- Extending fast neutron techniques to significant quantities of 233U that is of great significance to current international debate around the thorium fuel cycle and resulting in debate in the industrial / national laboratory community associated with this area of the nuclear discipline.
- Establishing an international partnership between the UK's fast neutron digital assay capability and ORNL, the world's leading uranium laboratory to be established resulting in impact for the UK nuclear community, particularly that associated with the National Nuclear Users' Facility.

In a specific context, we expect impact in the following areas:
- Confirming and advancing the reputation of the UK as a leader in nuclear safeguards research at a critical time for nuclear new build.
- Consolidating the UK's position as a leader in the search for a replacement for 3He and the application of fast neutron methods.
- Highlighting the possibility of improved methods for the characterisation of uranium-based orphan wastes, particularly in the context of decommissioning, waste management and non-proliferation.
- At technical level from challenging accepted ideas associated with die-away assay of uranium and changing the way it is done to incorporate fast neutrons.
- Stimulating a programme of the exchange of UK staff and students with Oak Ridge, many of whom who benefit from EPSRC programmes.
- Consolidating Oak Ridge intentions to set-up a related capability to the NNUF (ADRIANA) capability in the near future and the related impact on UK instrumentation businesses.
- A diversity of far-reaching impact benefits associated with the clean up of contaminated areas of the Oak Ridge site, advancing safeguards activities and opening up commercial possibilities for UK businesses such as JCS Ltd., Centronic, Kromek and Hybrid Instruments etc.


10 25 50
Description We have measured the 3rd and 4th fission neutron correlations for 252Cf for the first time. We have also measured the extent of the effects of cross-talk and photon breakthrough on the detection sensitivities of large arrays of detectors used for nuclear materials assay. These effects can be a significant source of uncertainty in the use of organic scintillators for nuclear safeguards, which is topical because of the supply constraints associated with 3He which has long been the preferred detection medium. From a more academic point of view, the measurements made under this award provided a means for experimental corroboration of a number of very advanced theoretical models and codes associated with the nuclear fission process, including for example the FREYA code development by Lawrence Livermore National Laboratory and another developed by the CEA, Cadarache, France.
Exploitation Route We have secured a 6-month STFC grant to continue this research for the benefit of the nuclear data community.
Sectors Energy,Security and Diplomacy

Description Our findings have stimulated Oak Ridge National Laboratory to talk to us about an allied approach to plutonium monitoring, which has then sensitised the ESRF to the possibility of being involved in these measurements, and an EPSRC Fellowship proposal has been submitted on this basis which is pending at the time of writing. An extensive review of one of our papers has led to impact amongst the USA community in this field, associated with measuring the 'third' neutron in fission events, and this research has also led to a close collaboration evolving with the French experts in this area from the CEA and Aix Marseille university. This activity has also led to some of the apparatus being seconded to Cavendish Nuclear Ltd. for a period of 6 months.
First Year Of Impact 2016
Sector Energy,Security and Diplomacy
Impact Types Policy & public services

Description Collaboration with CEA Cadarache concerning the FIFRELIN fission code 
Organisation French Alternative Energies and Atomic Energy Commission
Country France 
Sector Public 
PI Contribution We recorded fission data in collaboration with Oak Ridge National Laboratory and compared this with the outcome of the FIFRELIN fission code administered by the CEA at Cadarache in France.
Collaborator Contribution We discussed the outcome of the comparison extensively with Chebboubi and Litaize at the CEA at Cadarache, they provided access to the fission libraries necessary to run the codes effectively and also contributed significantly to a publication that describes the research in full.
Impact High-order angular correlation of californium-252 fission neutrons and the effect of detector cross-talk', M. J. Joyce, R. Sarwar, V. Astromskas, A. Chebboubi, S. Croft, O. Litaize, R. Vogt and C. H. Zimmerman, Nucl. Inst. Meth. A, online, February 2019.
Start Year 2017
Description Lawrence Livermore National Laboratory collaboration 
Organisation Lawrence Livermore National Laboratory
Country United States 
Sector Public 
PI Contribution We made measurements at Oak Ridge National Laboratory and compared these to the FREYA code developed and administered by LLNL.
Collaborator Contribution The experts at LLNL (R. Vogt) worked with us on the interpretation of the performance of the FREYA code and assisted extensively in the paper that was published based on this work in NIM.
Impact High-order angular correlation of californium-252 fission neutrons and the effect of detector cross-talk', M. J. Joyce, R. Sarwar, V. Astromskas, A. Chebboubi, S. Croft, O. Litaize, R. Vogt and C. H. Zimmerman, Nucl. Inst. Meth. A, online, February 2019.
Start Year 2018
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 INVITED Plenary, 20th June 2019, 6th International conference on Advancements in Nuclear Instrumentation Measurements Methods and their Applications (ANIMMA), Portoro┼ż, Slovenia,. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact I delivered an invited plenary talk at the ANIMMA conference in Slovenia, to a large audience and which was televised.
Year(s) Of Engagement Activity 2019