A chat with Stephen King, PhD student and NEST Fellow

Stephen spent four months at the Paul Scherrer Institute in 2019 working with the NEST-HYMERES project under the mentorship of Dr Abdelouahab Debhi.

Ensuring nuclear skills and education is an increasingly important challenge for NEA member countries, all of which need new generations of scientists and engineers for the continued safe and efficient use of nuclear technologies for a wide range of industrial, scientific and medical purposes. In this context, the NEA Nuclear Education, Skills and Technology (NEST) Framework was launched in 2019 with the collective effort of ten NEA member countries in order to build up skills vital for the future of the nuclear sector through multilateral co-operation.

The NEST-HYMERES Project, conducted at the Paul Scherrer Institute (PSI) in Switzerland alongside the NEA Joint Project Hydrogen containment experiments for reactor safety (HYMERES), addresses safety-relevant phenomena in nuclear reactor containments during accidents. Led by Professor Andreas Pautz, the project provides NEST Fellows with hands-on training opportunities during the experimental test campaigns carried out at the PSI Multipurpose Integral Test Facility for LWR Safety Investigations (PANDA) facility, one of the most advanced containment test facilities worldwide.  In parallel, it also aims at developing exploratory research projects under the guidance of experts at other NEST participating organisations.

The NEA spoke with Stephen King on his experiences as a NEST Fellow.  

Tell us about your NEST Fellowship: What has your training experience been like and what have you learnt?

My NEST Fellowship involved evaluating a computational technique that would help reduce the time needed to simulate a long-term computational fluid dynamic (CFD) calculation. The simulation could take up to a week to run on a super computer, so any effort to help reduce this duration was of interest. The technique entailed the use of a porous block to replace a 30x30 angled grid utilised to divert the path of a steam jet. The porous block was evaluated for its effectiveness in replicating the diversion of the jet and how much of an influence it would have in reducing the simulation time. I spent time learning not only how to use ANSYS Fluent, a CFD simulation software, but also techniques related to setting up and optimising the calculation.

Could you elaborate more? How do you think the NEST fellowship contribute to your knowledge and technical skills development?

 During my NEST Fellowship, I spent quite a bit of time building the foundation of my CFD skills in ANSYS Fluent and learning how to use the porous media approach in calculations. I was able to apply those skills when I returned to Texas A&M and I am now able to perform both experimental and computational work on the same subject. For example, in a project involving flow through a Pebble Bed Modular Nuclear Reactor (PBMR), I used a porous block to represent the complex geometry that is formed by the several thousand spheres in the real core. After running the simulations with the porous block, I was able to compare the data with experimental data from a scaled model I had created at the PSI and examine the differences.

Did your experience as a participant in the NEST HYMERES project influence your PhD research in any new and unexpected ways?

Before my NEST Fellowship , my research was exclusively experimental with some interest in CFD. My experience at the PSI allowed me to incorporate a couple of new techniques into my research involving CFD, namely the porous media model. Through implementing and running calculations with the porous model, I was able to engage in research involving not only experimental work, but also computational applications.

How about the relationship with your NEST mentor?

Dr Abdelouahab Dehbi was always monitoring my progress through weekly meetings and after completion of each task he always had a definitive plan on what I would be doing next. Furthermore, if I ever encountered a particularly difficult problem, Dr Dehbi was in close proximity and setting up a meeting to look at the results was never a difficulty. He was always willing to give me advice on what to look into and what sources to read, whereas without him I would have spent time searching the internet only to try many sources before I reached the solution needed.

There was a great benefit in being within such close proximity to Dr Dehbi. He always made himself available to examine my results and guide me in the best direction. Besides, the skillsets I developed could not be found in a manual or an online resource, but rather they came from the knowledge of individuals with years of experience.

What else did you appreciate about your NEST Fellowship?

What I appreciated the most is the relationships I built with my mentor Dr Abdel, as well as with other established scientists and fellow students. Even over a year later, I am still in touch with some of those whom I met at the PSI, and I hope we meet again. When discussing my research with other students, similarities can always be found, which increases our understanding of each other’s research topics.

I most certainly would recommend the NEST programme to other researchers in STEM, especially to those like me who would like to get experience at another institute outside of the United States.