Tag Archives: fusion energy

Structural damage assessment using infrared detectors in fusion environments

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Schematic representation of plasma flux in a fusion reactorAbout six months ago, I described the success of my research group in detecting the early stages of the development of damage in structural components using small, cheap devices based on infrared measurements [see ‘Seeing small changes is a big achievement‘ on October 26th, 2022] after it had been reported in the Proceedings of the Royal Society.  The research was motivated by the needs of the aerospace industry and largely supported via the European Union’s Horizon 2020 research and innovation programme.  We are planning to extend the research to allow our technology to be used for diagnostics in future fusion power plants.  Plasma facing components in these powerplants will experience significant structural and functional degradation in service due to the extreme condition in the reactor.  Our aim is to develop systems based on our infrared monitoring technology that can identify and track material degradation without the need for plant shutdown thereby enabling unplanned maintenance to be undertaken at the earliest sign of component failure.  We are collaborating with the UKAEA and are looking to recruit a PhD student to work on the project supported by the GREEN CDT and Eurofusion.  If you are interested or know someone who might be interested then please follow this link for more information.

Reference:

Amjad, K., Lambert, C.A., Middleton, C.A., Greene, R.J., Patterson, E.A., 2022, A thermal emissions-based real-time monitoring system for in situ detection of cracks, Proc. R. Soc. A., 478: 20210796.

Admiral’s comments on fission hold for fusion 70 years later

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Last month the US Energy Secretary, Jennifer Granholm announced a successful experiment at the Lawrence Livermore National Laboratory in which 192 lasers were used to pump 2.05 mega Joules of energy into a capsule heating its contents to 100 million degrees Centigrade causing fusion of hydrogen nuclei and the release of 3.15 mega Joules of energy.  An apparent gain of 1.1 mega Joules until you take account of the 300 mega Joules consumed by the 192 lasers.  The reaction in the media to this fusion energy experiment and the difficulties associated with building a practical fusion power plant, such as the Spherical Tokamak Energy Production (STEP) project in the UK (see ‘Celebrating engineering success‘ on November 11th, 2022) reminded me of a well-known memorandum penned by Admiral Rickover in 1953.  Rickover was first tasked, as a Captain, to look at atomic power in May 1946 not long after first human-made self-sustaining nuclear chain reaction was initiated in Chicago Pile #1 during an experiment led by Enrico Fermi in 1942.  He went on to become Admiral Rickover who directed the US Navy’s nuclear propulsion programme and the Nautilus, the first nuclear-powered submarine was launched in 1954.  With thanks to a regular reader of this blog who sent me a copy of the memo and apologies to Admiral Rickover, here is his memorandum edited to apply to fusion energy:

Important decisions about the future of fusion energy must frequently be made by people who do not necessarily have an intimate knowledge of the technical aspects of fusion.  These people are, nonetheless, interested in what a fusion power plant will do, how much it will cost, how long it will take to build and how long and how well it will operate.  When they attempt to learn these things, they become aware the confusion existing in the field of fusion energy.  There appears to be unresolved conflict on almost every issue that arises.

I believe that the confusion stems from a failure to distinguish between the academic and the practical.  These apparent conflicts can usually be explained only when the various aspects of the issue are resolved into their academic and practical components. To aid in this resolution, it is possible to define in a general way those characteristics which distinguish one from the other.

An academic fusion reactor almost always has the following basic characteristics: (1) It is simple. (2) It is small.  (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose . (7) The reactor is in the study phase.  It is not being built now.  On the other hand, a practical fusion reactor can be distinguished by the following characteristics: (1) It is being built now.  (2) It is behind schedule. (3) It is requiring an immense amount of development on apparently trivial items. (4) It is very expensive. (5) It takes a long time to build because of the engineering development problems. (6) It is large. (7) It is complicated.

The tools of the academic-reactor designer are a piece of paper and a pencil with an eraser. If a mistake is made, it can always be erased and changed.  If a mistake is made, it can always be erased and changed.  If the practical-reactor designer errs, they wear the mistake around their neck; it cannot be erased.  Everyone can see it. 

The academic-reactor designer is a dilettante.  They have not had to assume any real responsibility in connection with their projects.  They are free to luxuriate in elegant ideas, the practical shortcomings of which can be relegated to the category of ‘mere technical details’.  The practical-reactor designer must live with these same technical details.  Although recalcitrant and awkward, they must be solved and cannot be put off until tomorrow.  Their solutions require people, time and money.

Unfortunately for those who must make far-reaching decisions without the benefit of an intimate knowledge of fusion technology and unfortunately for the interested public, it is much easier to get the academic side of an issue than the practical side. For the large part those involved with academic fusion reactors have more inclination and time to present their ideas in reports and orally to those who will listen.  Since they are innocently unaware of the real and hidden difficulties of their plans, they speak with great facility and confidence.  Those involved with practical fusion reactors, humbled by their experiences, speak less and worry more.

Yet it is incumbent on those in high places to make wise decisions, and it is reasonable and important that the public be correctly informed.  It is consequently incumbent on all of us to state the facts as forth-rightly as possible.  Although it is probably impossible to have fusion technology ideas labelled as ‘practical’ or ‘academic’ by the authors, it is worthwhile both authors and the audience to bear in mind this distinction and to be guided thereby.

Image: The target chamber of LLNL’s National Ignition Facility, where 192 laser beams delivered more than 2 million joules of ultraviolet energy to a tiny fuel pellet to create fusion ignition on Dec. 5, 2022 from https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition

Celebrating engineering success

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Today is National Engineering Day [see ‘My Engineering Day’ on November 4th, 2021] whose purpose is to highlight to society how engineers improve lives.  I would like to celebrate the success of two engineers who are amongst the seventy-two engineers elected to the fellowship of the Royal Academy of Engineering this year.  Chris Waldon is leading the design and delivery of a prototype fusion energy plant, targeting 2040, and a path to the commercial viability of fusion.  This is a hugely ambitious undertaking that has the potential to transform our energy supply.  He is the first chief engineer to move the delivery date to within twenty years rather than pushing it further into the future.  My other featured engineer is Elena Rodriguez-Falcon, a leading advocate of innovations in engineering education that focus on encouraging enterprising and socially-conscious approaches to designing and delivering engineering solutions.  These are important developments because we urgently need a more holistic, sustainable and liberal engineering education that produces engineers equipped to tackle the complex challenges facing society.  Of course I am biased having worked and published with both of them.  However, I am not alone in my regard for them and will be joining other Fellows of the Royal Academy of Engineering at a dinner in London next week to celebrate their achievements.

If you don’t succeed, try and try again…

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Photograph of S-shaped plateYou would not think it was difficult to build a thin flat metallic plate using a digital description of the plate and a Laser Powder Bed Fusion (L-PBF) machine which can build complex components, such as hip prostheses.  But it is.  As we have discovered since we started our research project on the thermoacoustic response of additively manufactured parts (see ‘Slow start to an exciting new project on thermoacoustic response of AM metals‘ on September 9th, 2020).  L-PBF involves using a laser beam to melt selected regions of a thin layer of metal powder spread over a flat bed.  The selected regions represent a cross-section of the desired three-dimensional component and repeating the process for each successive cross-section results in the additive building of the component as each layer solidifies.  And there in those last four words lies the problem because ‘as each layer solidifies’ the temperature distribution between the layers causes different levels of thermal expansion that results in strains being locked into our thin plates.  Our plates are too thin to build with their plane surfaces horizontal or perpendicular to the laser beam so instead we build them with their plane surface parallel to the laser beam, or vertical like a street sign.  In our early attempts, the residual stresses induced by the locked-in strains caused the plate to buckle into an S-shape before it was complete (see image).  We solved this problem by building buttresses at the edges of the plate.  However, when we remove the buttresses and detach the plate from the build platform, it buckles into a dome-shape.  Actually, you can press the centre of the plate and make it snap back and forth noisily.  While we are making progress in understanding the mechanisms at work, we have some way to go before we can confidently produce flat plates using additive manufacturing that we can use in comparisons with our earlier work on the performance of conventionally, or subtractively, manufactured plates subject to the thermoacoustic loading experienced by the skin of a hypersonic vehicle [see ‘Potential dynamic buckling in hypersonic vehicle skin‘ on July 1st 2020) or the containment walls in a fusion reactor.  Sometimes research is painfully slow but no one ever talks about it.  Maybe because we quickly forget the painful parts once we have a successful outcome to brag about. But it is often precisely the painful repetitions of “try and try again” that allow us to reach the bragging stage of a successful outcome.

The research is funded jointly by the National Science Foundation (NSF) in the USA and the Engineering and Physical Sciences Research Council (EPSRC) in the UK (see Grants on the Web).

References

Silva AS, Sebastian CM, Lambros J and Patterson EA, 2019. High temperature modal analysis of a non-uniformly heated rectangular plate: Experiments and simulations. J. Sound & Vibration, 443, pp.397-410.

Magana-Carranza R, Sutcliffe CJ, Patterson EA, 2021, The effect of processing parameters and material properties on residual forces induced in Laser Powder Bed Fusion (L-PBF). Additive Manufacturing. 46:102192