I was reading this article from earlier this year by a former NRC Chairwoman (Allison MacFarlane) who seemed to cast SMR/MSR advocates as if they are essentially used-car salesmen.
> Nobody knows what the numbers [on waste products] are, and anybody who gives you numbers is selling you a bridge to nowhere because they don't know,
> Nobody's been able to answer my questions yet on what all these wastes are and how much of them there are, and how heat-producing they are and what their compositions are,
> My sense is that all of these reactor folks have not really paid a lot of attention to the back end of these fuel cycles,
Now, while she's correct that "Nobody's really doing this right now.", (though blatantly incorrect with "Nobody has ever set up a molten salt reactor and used it to produce electricity." since there are at least a couple - including ORNL's MSRE), I'm confused by the claim that nobody can answer her on what the fission products would be.
I've seen breakdown - simulations that seem to be able to simulate the approximate proportions of different fission products (with, obviously, some variability acknowledged).
So I'm confused. Is she right and SMR/MSR advocates simply haven't done the calculations for what the waste products would look like in terms of composition and quantity? Or is she misrepresenting and disparaging many of the Gen4 advanced reactors with vague assertions of a lack of consideration? Or something somewhere in between?
It seems to me that either these companies advocating these new reactors are blazing a trail so aggressively to get it started that they haven't considered what it will look like once its done, OR she, a former Chairwoman of the NRC, is actually trying to undermine advancement of the nuclear energy industry.
Either case isn't great and I'm trying to not be depressed by either conclusion. Any insight would be appreciated.
In the wikipedia article on nuclear fission there is an animation demonstrating the two uranium masses coming into close proximity and a neutron hitting a Uranium-235 isotope and splitting into two fission products along two additional neutrons being ejected in different directions from the interaction. How does one mathematically determine the trajectories of these products and neutrons to accurately simulate nuclear fission? Does the attack angle of the initial neutron play a crucial role in determining these trajectories?
I've been reading about fission and fusion and so far I understand that energy is released if an atom lighter than Iron-56 fusions and an atom heavier than Iron-56 fissons, because the net binding energy of the result of the reaction is higher than initially. I also understand that it's because there is mass lost, and thanks to Einstein's equation we know this mass is lost in the form of energy. What I don't understand is why the mass is lost - why does the higher binding energy equal less mass?
I originally posted this in r/Idontworkherelady, and it got content policed. So I'm trying it here because I was there to offer technical support - I wrote the bleeding manual - even if my main function was to sell the stuff to people I judged wouldn't be ringing tech support too often.
TL;DR : Prospective customer makes hopelessly vague request. OP briefly investigates and declines the 'opportunity'. OP and their employer GTFO.
A fair few years before the new and exciting job at XYZ Inc I mentioned in my last post, I learnt my trade somewhere else. Just to make it confusing, we'll call them XYZ Limited. XYZ Ltd did all-sorts, basically they were a one-stop-shop for industrial fixes. Anything from "I need a motor for my conveyor belt and it goes about this fast", to all the power, transmission and control gear on a machine to make berets - the hats - start to finish in less than a minute a piece. Berets are knitted by the way, never realised that until I saw them being made.
Anyway, you come to XYZ Ltd with your specification - that means you understand your manufacturing process and design the parts that actually interface with the materials and product, and then you tell us how and when they're supposed to move. We engineer that and sell you a kit of parts to do the job including commissioning if you need it. These jobs might be a one-off or they might be low-production jobs where the customer called off repeat kits as they sold machines.
You get the idea. My job at XYZ Ltd was to be the technical expert on a particular technology/product range. Enquiries came in, and if they looked like they needed my kind of tech, they landed on my desk. Assuming it was my area, I worked out how to do the job, using other XYZ Ltd products as well if needed, and then went back and quoted the customer. Often it was necessary to see the thing first hand to really understand, and it also helped drum up sales to go round prospects with the sales reps. So my time was spent maybe 60/40 in the office/field.
So one day I'm in the office and a fax lands on my desk. Customer specification, quotation required.
"We have released these tender documents to several potential suppliers in your industry, and your best price and a speedy response will be needed for XYZ Ltd to have any chance of getting the order."
I'll call the possible customer D-Tech. For Dunce.
This thing runs to seven pages, which isn't a bad sign in itself - the devil is always in the detail, so the mor
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I am wondering why this difference between nuclear fusion and fission exists. Fission is dominated by the kinetic energy increase of the products while fusion is dominated by radiation (correct me if that's wrong). So I thought that Coulomb repulsion between the products of a fission reaction (they are very close together immediately after fission) could explain it. But then again, the kinetic energy increase is covered by mass-energy-equivalence and this is a completely different concept than Coulomb repulsion. So this left me confused.
When a neutron is absorbed by a u235 nucleus, what precisely determines which fission products are produced? Is it the exact location into the nucleus in which the neutron is absorbed, the energy of the neutron? Or something else?
So, in going from basically knowing zilch about nuclear power to being a casual enthusiast, something really started bugging me.
So, you've got fissile fuel. Typically Uranium 233/235 or Plutonium 239/240.
And when that stuff fissions, some neutrons go out and one of a couple things happen:
- Hits a fissile atom. Atom fissions into two halves 'n s'more neutrons
- One of them is in the ~90-100 isotopic number range
- One of them is in the ~130-140 isotopic number range
- These are products of fission
- Hits a fertile atom. Atom absorbs neutrons.
- Might absorb more than one
- Typically results in ~234-242 isotopic number range atoms
- These are actinides
- Hits a neutron absorber. Absorbs neutrons, slightly changes.
- These are typically existing fission products or control rods
So, the first group seems like actual fission products, because they're the direct product of a fission event. They can be scary radioactive, but most of them don't survive the 10-year mellow period in the spent fuel pool after usage.
In fast reactors, they're theoretically the only waste product. In current burner reactors, they're basically a fraction of a percent of the stuff stored in dry cask.
Now, actinides are basically more... fission adjacten. They are not produced by a fission, but by neutrons hitting fertile stuff (or fissile stuff and not fissioning?). Why are these called "long lived fission products"? Are they called that by anyone other than the NPP-adverse? Given that anything in the over-230 isotoipc number range is, for all intents and purposes, still fuel, why is it treated identically to the sometimes violently radioactive stuff in the sub-200 isoptic number range?
Also, is there a better term than "isotopic number" to describe that stuff? I know "atomic weight" is wrong, 'cause AFAIK that's just the proton count (kinda-sorta).
If I blow up the earth, blame that guy who ate a gherkin 2 weeks ago.
I've read on C-14 diamond batteries, RTG using Sr-90. How about Cesium isotopes?
Curious about all manners of harnessing... movement, electricity, heat, even using to radiate foods?
One idea I had (and I'd like its stupidity pointed out) is that since FP seem (to me) kind of unique in how they just keep generating heat no matter how hot they get.
So, for example, devices which would look to people as perpetual-motion-machines? Use FP heat to expand a gas similar to how combustion engines drive a shaft? The gas itself could be a FP.
I'm not a mechanical engineer so possibly there's already an index of ideas like this (but good ones), or obvious reasons why FP can't be employed in many situations (aside from the need for radiation shielding)?
Diamond batteries, with their beta radiation being absorbed by outer layers of the diamond's carbon, is an example where the implementation incorporates radiation shielding.
I'd assume most devices that incorporate heating-of-water could be configured so not-even-gamma escapes?
The fusion Dream has been with us for decades, The ITER project as been around near as long as i've been alive.
But looking at it in the context of the modern smart grid and what a good gigawatt fission plant can produce, and I'm not clear what advantage fusion would allow.
What will a typical fusion plant look like? Put simply; a large building with a sophisticated core and plenty of shielding, producing heat for a steam generator. In terms of grid planning and construction, from what I understand it's broadly the same challenge as a fission plant.
And in terms of power produced, the studies i've read about DEMO suggest a plant would produce power in the same range as a fission plant, ie: two gigawatts
If the construction costs are broadly similar(in an ideal situation where the tech is stable and routine) then we could put a cost on it of $2 billion per gigawatt.
The major advantage of Fusion is the unlimited amount of fuel and negligible waste.
But are either of those issues a problem for us at the timescales we are talking about?
We have decades of uranium around, and if you compare the amount of prospecting done, it's much less than other minerals, so much more materials should be out there to be found.
And while waste is an issue now, the combination of better storage plus proper breeder reactors will eliminate most all high level waste.
In short, what advantages does fusion offer over a well designed modern fission plant in an environment with proper breeder reactors and storage solutions?
https://upload.wikimedia.org/wikipedia/commons/6/68/ThermalFissionYield.svg
I realize that the products will tend to be unstable because of the large number of neutrons for their atomic weight, but what's the deal with all of this technetium? Why is that a preferred fission product for Pu-239 and U-235?
Then there's the weird two-peaked distribution of the fission product mass. I wouldn't find a bimodal distribution particularly weird, except that in this case in the middle it drops to essentially zero.
Hi all, I'm a humanities boffin trying to understand the physics of storing fission products after all the longer lived actinides have been fissioned away in a GenIV reactor. (Either Integral Fast Reactor or LFTR, although I love the sound of the LFTR!) Many websites and youtube videos tell us that burning nuclear 'waste' (all those actinides) could power America for 1000 years and the UK 500 years (and who knows how much waste Russia and China have to burn away, and how long they would last)? Seen in this perspective, so called 'nuclear waste' is actually an incredibly useful resource. But.
But there's those fission products to store. OK, I was happy when I heard that they were so 'hot' that we only had to store them 300 years. That's fine. But what about the much longer lived fission products? Are they so much longer lived that they're not really that radioactive to worry about in the first place? Or even if they are, are they such a small fraction of the overall waste that leaving them in the 300 year underground bunker is not an issue? Or can the longer lived be separated out of the shorter lived fission products to be specially buried in a deep subduction zone plate or something like that? Just trying to understand safe nuclear disposal. I was happy when I thought nuclear 'waste' would just be burned and then stored for 300 years, but now it appears a bit more nuanced. https://en.wikipedia.org/wiki/Long-lived_fission_product
I know that many radioisotopes of certain elements (caesium, xenon, etc.) are collected as byproducts of fission reactions, but is there any way to directly control the type or amount of a specific byproduct, one that could perhaps be more easily disposed of? My first guess would be no, because what little I know of nuclear reactions tells me that, unlike chemical reactions, the nucleus is not easily manipulated by things like temperature, etc.
I'm working on incorporating a fission product yield curve to show some advanced high schoolers (see previous post here) the discrepancy in fission product masses. I think it's a cool part of the fission process, hopefully they will as well.
I am including a 'standard' fission product yield curve for the thermal fission of U-235, but also a curve for the fast fission of U-235, to show how the curves broaden and form a singular peak at high neutron energies. My question is: why does this happen? I have not found a satisfactory answer in the RadPhysics text I have with me currently (Shultis & Faw... ehh) or Google.
My (&coworker's) conjecture: At low energies, neutrons are actually absorbed into the target nucleus for fractions of a second, inducing oscillations into the struck nucleus. This causes the non-symmetry in fp masses, because the atom will split along the weak point, which is not necessarily the 'center.' In fast fission, the neutrons are at much higher energies and thus impart more energy to the atom - shortening/removing the oscillatory period and essentially just 'busting the atom apart.' Is this even close to correct? Thanks!
I've seen advocates of Liquid Fluoride Thorium Reactor (LFTR) claim that because it's (theoretically at least) possible to burn off actinides completely, reactor's waste would need only 300 years of storage, 10 half-lives of Sr-90 and Cs-137.
I appreciate that transuranics are major problem requiring long term storage but would long-lived fission products really be a non-issue? Tc-99 or maybe Sn-126?
I can read their decay energy and half-life from Wikipedia but it's difficult to grasp how big an issue would a ton of Tc-99 be. Safe enough to not require long-term storage? Sprinkle on ground and build a parking lot over it?
Diagram linked is from LFTR's Wikipedia page.
Sorry in advance for the lengthy question.
In nuclear fusion, two atoms collide at extremely high speeds and create one. This is what happens in stars. If we could find a way to do this on Earth in a controlled environment, would we be able to use the eventual products for nuclear fission? If so, would this be an "unlimited" source of energy?
