Category Archives: MyResearch

Work, rest and play in Smallville

Predicting release rates of hydrogen from stainless steel

The influence of hydrogen on the structural integrity of nuclear power plant, where water molecules in the coolant circuit can be split by electrolysis or radiolysis to produce hydrogen, has been a concern to engineers for decades. However, plans for a hydrogen economy and commercial fusion reactors, in which plasma-facing structural components will likely be exposed to hydrogen, has accelerated interest in understanding the complex interactions of hydrogen with metals, especially in the presence of irradiation. A key step in advancing our understanding of these interactions is the measurement and prediction of the uptake and release of hydrogen by key structural materials. We have recently published a study in Scientific Reports in which we developed a method for predicting the amount hydrogen in a steel under test conditions. We used a sample of stainless steel as an electrode (cathode) in an electrolysis cell that split water molecules producing hydrogen atoms that were attracted to the steel. After loading the steel with hydrogen in the cell, we measured the rate of release of the hydrogen from the steel over two minutes by monitoring the drop in current in the cell, using a technique called potentiostatic discharge. We used our measurements to calibrate a model of hydrogen release rate, based on Fick’s second law of diffusion, which relates the rate of hydrogen motion (diffusion) to the surface area perpendicular to the motion and the concentration gradient in the direction of motion. Finally, we used our calibrated model to predict the release rate of hydrogen over 24 hours and checked our predictions using a second measurement based on the hydrogen released when the steel was melted. So, now we have a method of predicting the amount of hydrogen in a steel remaining in a sample many hours after exposure during electrolysis without destroying the test sample. This will allow us to perform better defined tests on the influence of hydrogen on the performance of stainless steel in the extreme environments of fission and fusion reactors.

Source:

Weihrauch M, Patel M, Patterson EA. Measurements and predictions of diffusible hydrogen escape and absorption in cathodically charged 316LN austenitic stainless steel. Scientific Reports. 13(1):10545, 2023.

Image:

Figure 2a from Weihrauch et al , 2023 showing electrolysis cell setup for potentiostatic discharge experiments.

Conflicted about cost-benefit analysis of international conferences

3 Replies

Last week I wrote about my stimulating experience of attending a conference in Orlando, Florida and presenting our recent research to the experimental mechanics community for the first time in four years. Whilst there, I was conscious of the ecological footprint of my trip – the venue was making extensive use of single use plastics on a scale that surprised me. However, my trans-Atlantic flight had an order of magnitude larger impact. It is difficult to find a reliable estimate of the carbon emissions for a return flight between the UK and Florida but 1,267 kg CO2 from the Guardian newspaper website lies between a lower bound estimate of 856 kg CO2 from iata.org and and an upper bound of 2,200 kg CO2 from myclimate.org. This is equivalent to about one-sixth of my annual domestic carbon footprint of 9,000 kg CO2 using the calculator on the World Wildlife Fund website. The UK average footprint is 9,300 kg CO2/capita and the global average is 6,300 kg CO2/capita. The question is whether it is justifiable to generate additional emissions to attend a research conference? The prime motivation of the research that I presented is to support the development of aircraft which are lighter with less embedded carbon and use less energy while also having a longer useful life. Ultimately, supporting the aviation industry to achieve its target of zero-net emissions by 2050. The carbon emissions of the global aviation industry in 2021 were 720 Mt CO2 [see IEA report]; hence, if my research contributes towards one hundredth of a percent reduction in these emissions then this would be 72,000 kg CO2/year. It seems reasonable to cause a tenth of this annual saving each year (7,200 kg CO2/year) for the next ten years in order to deliver the required technology, i.e., committing one year’s savings to achieve an annual saving in perpetuity. The problem is that I do not have a reliable estimate of the carbon footprint of my research activities. I supervised an MSc student a couple of years ago who conducted a carbon audit of the School of Engineering and estimated the carbon emissions due to research alone to be 61,531 kg CO2 excluding heating, lighting and travel. My group might be responsible for 10% of these emissions, i.e., about 6000 kg CO2; hence, adding about 1,200 kg CO2 to interact with other researchers at a conference seems reasonable and within a budget of 7,200 kg CO2. However, it is difficult to find reliable data to use in estimating carbon emissions for these activities and so perhaps the key conclusion is that we need more and better carbon audits to allow more informed decision-making. In the meantime, perhaps attendence at an international conference once every four years is sufficient.

Image: Tayeb Mezahdia

Busman’s holiday

Leave a reply

A couple of weeks ago, I travelled to my first international conference following the pandemic lockdowns. It was stimulating to hear presentations from well-established researchers who I had not seen in person for four or five years and to meet new researchers who had joined our community since 2019. It was exciting to present our own research to an international audience for the first time and get instant feedback on it. Of course, it helped that we met in Orlando, Florida. If a change is as good as a rest then I had a four day rest from my usual work routines. You could call it a holiday in the sense that a holiday is a day of festivity during which we celebrate in a joyful or exuberant way, according to the dictionary, and I felt we joyfully celebrated our research. I gave three presentations on our work on low-cost, real-time crack monitoring described in ‘Seeing small changes is a big achievement’ on October 26^th, 2022; on additive manufacture of reinforced flat plates (see ‘On flatness and roughness’ on January 19^th, 2022); and on a further development of the research described in ‘Less certain predictions’ on August 2^nd 2017. Listening to other speakers caused my own thoughts to wander and I found myself using my phone as a mental prosthetic or expert system [see ‘Thinking out of the skull’ on March 18^th, 2015] to provide me with information about definitions, to remind me about previous research, both ours and other people’s, as well as to refresh my memory on previous ideas via this blog [see ‘Amplified intelligence’ on January 4^th, 2023]. Susan Greenfield, feared that such devices and activity might lead to formation of smaller neuronal assemblies in the brain and consequential loss of creativity [see ‘Digital hive mind’ on November 30^th 2016]; instead, I found myself making faster connections and creating new ideas for future research. However, I recorded them, as Leonardo di Vinci would have done – in my notebook! My excuse is that my phone was too busy being an expert system and writing my notes by hand allowed my brain to connect the fragments of ideas and thoughts into some sort of coherency [see ‘Space between the words’ on July 6^th, 2022]. Besides writing four posts for this blog in as many days, I have a list of new ideas to accelerate existing projects and start new ones. So, whilst post-pandemic I will not be returning to business as usual in terms of international travel, a small number of infrequent trips would appear to be worthwhile, especially if our research helps move our economies towards their zero emissions targets.

Image: photograph from entrance to conference hotel.

Realize Engineering

An engineering commentary for everyone on the first Wednesday of every month