All 3 entries tagged Fusion Power
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November 24, 2022
SOFT32 – A Reality Check for what fusion power really is
A belated entry considering that SOFT32 took place way back in September (incidently just after we had reproduced decent Gen2 RSB samples)
This is the first in a somewhat belated set of entries but this blog aims to be unlike others and not just get abandoned because things are busy, since that is more or less a given.
The 32nd Symposium on Fusion Technology (SOFT32) in Dubrovnik, Croatia took place from the 18th-23rd of September. This was the first hybrid/live conference since before 2020 since SOFT31 was a virtual conference held online. This conference is not long after JET's record-breaking dueterium-tritium campaign, holding a fusing plasma for 5s and ITER director Dr Bigot's untimely death in May.
Certainly, while there is a lot that can be done online, nothing beats the immersion that happened when you are interacting informally with people as well as being in the talks and the posters. It has given us a greater appreciation for the international effort to get fusion working and on how far ITER and JET has come.
The biggest takeaway was that each fusion reactor is more than just a reactor. For a tokamak reactor, the plasma chamber is only 1 part of the reactor. The reactor also has to comprise of the following facilities:
Cryoplant: Cooling the magnetic coils (LTS/HTS and copper) and cooling the dueterium/tritium for the fuel plant
Fuel plant: Harvesting and handling tritium from the fuel blanket within the reactor prior to use as fuel. Making the fuel pellets and injecting them into the reactor to fuel the plasma.
Gyrotrons: Powerful microwave resonators to pre-heat and energise the plasma prior to initiating fusion.
Neutral beam injector: Linear accelerator to initiate fusing plasma reactions once the plasma is energised from the gyrotrons:
Monitoring and diagnostics: Monitoring the status of the plasma, vacuum, shielding, magnets and blanket.
Heat rejection: Removal of heat both for useful work and 'cool' heat from the magnets and cryoplant.
When the scale of setting up a tokamak is understood it becomes clear that the reason fusion power takes such a long time is that it is very difficult and it has taken a long time just to appreciate what needs to be done alone.
So from this we can see that ITER is a very important project, not just because it was the only international collaborative project initiated between the USSR and America in 1987 but that it has also carved out a path to industrialization for companies and universities working on fusion power. This has also stimulated research and development into related technologies and facilities that are critical to a wide range of applications inside and outside of fusion power.
What is for certain is that we are now in a situation where practical fusion power is no longer falling in the trope of '20 years away and always will be' but there will be plenty of challenges involved.
With respect to the cWC-RSB project it has also shown just how much qualification reactor candidate materials require. Not just the shielding but also materials that form the blankets, divertors, coolant networks, steels and plumbing adjacent to the inner shielding. This goes a long way to why W is still the main candidate shielding material since it has the most testing and data. The recent succesful JET campaign was used in part to qualify the W:Be inner wall, referred to as the ITER-like wall.
So the biggest conclusion we can take from SOFT32 alongside all the networking and knowledge about fusion is what is needed for a practical shielding material and the experimental data needed. W has blazed the trail so that cWC-RSB can follow.
April 06, 2022
How To Irradiate Your Samples
Following some of the successes and pitfalls at the DCF facility we now have all the irradiations completed thanks to the dedicated staff at the Dalton Cumbrian Facility. Since the energies in this round of experiments were sufficiently below the threshold of activation, samples were dispatched in the post.
The next stage will be to clean and mount sample for cross-sectional imaging, hardness testing, EBSD and TEM but that will be discussed in a later entry since much of that work will be for publication.
So how does one get to irradiate samples in the first place? And what has this specific experiment got to do with the first goal of the Radiation Dense Materials concept?
First of all as with any new science experiment, you have to talk to people first, in person, online or by email. This is critical to ensure that you can flesh out the proposed experiment and see how feasible it is or isn't. By discussing the planned irradiation schedule with the staff at the Dalton Facility we were able to acertain that ambient and non-ambient irradiation was possible with the proton beam and the gamma irradiator.
One of the inherent difficulties of current irradiation facilities is that generally samples can only be irradiated by one type of radiation at one time, unless placed in a test reactor. This is similar to reproducing a painting but with only one brush and one pigment. Hence, it is important to state the limitations of irradiation testing on samples with this in mind.
So, how are samples actually irradiated? This depends on the method and the radiation used. For the gamma irradiator it is simply a case of tracking the face closest to the 60Co source and placing it in a low-activation borate glass. The 60Co irradiator is shown below:
For low-temperature (77K) irradiations, samples were placed in a dewar full of LN2. Since oxygen liquifies at 85K this forms a pool in the dewar which under gamma irradiation transforms to O3 which is solid at LN2 temperatures. Solid O3 is an explosion hazard and thus nescessitates emptying and renewing the LN2 every 5 kGy. The low-temperature high-dose gamma sample had 90 kGy in total.
For proton beam irradiation, sample preparation is more involved. Samples need to be mounted with a heat-resistant conductive adhesive (silver paste) and need alignment such that the beam energy and radiation time can be computed, the exact figures depending on the dosage and the target temperature. Samples mounted for proton-beam irradiation are shown below:
Since protons are charged particles, total proton dosage can be computed from the charge accumulated from the beam current. Alongside sample irradiation, other data from samples such as emissivity can be obtained from proton irradiation at elevated temperatures.
Data analysis is at the earliest stages with the following planned sequence (1) Cross-sectional imaging (2) microhardness measurements (3) EBSD and (4) TEM (specifics to be determined following from EBSD and HV measurements).
Ultimately, this work will form the outline for subsequent radiation work as this is a first for both cWC and RSB materials.
March 30, 2022
The Inaugural Entry – the life and times of the Radiation Dense Materials Group
Writing about web page https://warwick.ac.uk/fac/sci/physics/research/condensedmatt/radiation_dense_materials
Welcome to the Radiation Dense Materials Group Blog. This blog will showcase the latest research from this group alongside how the research came to be with notes and photos of facilities, locations and conference trips. This will give people an insight into how research takes place on a day-by-day basis and on how many steps it takes to get to where you want to be.
The Radiation Dense Materials group aims to sythesize, study and develop novel concept radiation dense materials with the initial aim of making compact radiation shielding for fusion reactors and to make practical fusion power generation possible by 2030. It is envisaged that this will only be one such application for radiation dense materials when considering the need to expand the nuclear sector as a carbon-free power source.
Nuclear fusion has the potential to be a safe, effective carbon-free power source but has been limited in part by the lack of materials that can both attenuate radiation effectively and withstand the extremes of temperature expected within a power-generating fusion reactor. The plasma-facing component is expected to withstand temperatures up to 1000oC during normal operation. Superconducting magnets require cryogenic cooling (<77K), both of which would be seperated from each other by the shielding/coolant/Tritium blanket by little more than 1-2 m in a compact spherical tokamak. The initial cWC-RSB concept aims to be able to satisfy both radiation shielding and mechanical aspects with respect to this application.
This blog aims to be as interactive as possible and to give people an insight into how scientific research takes place behind the scenes.