We are a bunch of Nuclear Scientists and Engineers in New Mexico - Ask Us Anything!

It seems like the biggest challenge facing mass nuclear power generation is public perception. Do you think this is something our culture can overcome, and what do you think it will take?

I think it’s something we can and must overcome. It’ll take big contributions from both the technical and social sciences. On the technical side, the industry needs to deliver advanced reactors that can compete with natural gas power plants and even wind and solar + storage. It looks like some of the new passively safe and factory produced designs that are working their way through the regulatory process will be able to do that. Even if they get an operating license, they’ll need a social license.

That’s where the whole ecosystem of nuclear advocacy groups can contribute by telling the story about how this incredible energy source, first pioneered by nature itself at least 1.7 Billion years ago, with the Oklo natural nuclear reactor in Gabon, can help bring us back from ecological collapse as a result of climate change. My nonprofit, Generation Atomic, is working at doing this with a team of volunteers doing outreach activities in their communities, as well as with creative musical approaches like this music video at the experimental breeder reactor and this climate parody of sound of silence. We need the nuclear for climate concept to go viral if we're going to be successful... so if you have ideas, strategies, resources to help-- we need your help.

Adding to what Eric said, I think us nuclear engineers can do a lot to fix nuclear's public perception problem. I could spend all day talking about this, but I think the two most important things for nuclear engineers to fix are:

1. Be visible.
2. Have an approachable message.

For point #1, most nuclear engineers become nuclear engineers because we don't like public speaking, interacting with people, or dealing with any human problems. Math, physics, and coding are safe and have lots of intriguing problems to solve. Anti-nuclear people are the opposite - they thrive on interacting and debate, and they believe they're working for a righteous cause. It's up to us nukes to do what u/ericgmeyer has done and create platforms to interact with the public and get our message out. People need to talk with real-life nuclear engineers, tour real nuclear power plants, and see the actual benefits that nuclear power has on their communities.

For point #2, nuclear has a unique PR challenge because of how complicated it is. If you need to understand quantum mechanics to understand why nuclear power is safe, then nuclear will never solve its PR problem. Nuclear engineers tend to be very detailed oriented and they also focus on the "gotcha's" and pitfalls of systems. These are great characteristics for effective engineers, but not for effective PR. We tend to answer questions with too much detail, too many qualifiers, and in a way that people can't relate to or understand. We need to have concise answers that are simple and easy to understand. I.e., instead of answering the question of "Is nuclear power safe?" with...

• "Due to the particle-wave nature of matter, nuclear cross sections have thousands of discrete energy resonances. As the temperature of material increases, Dopplar Broadening broadens the range of the resonances, resulting in a net increase of neutron absorption and thus a negative reactivity coefficient..."

We need to respond with...

• "Yes, nuclear reactors are safe. In fact, they are designed so that the physics of the reactor will shut itself down if the fuel temperature increases too much."

On the subject of Molten Salt Reactors, the Thorium based reactors showed great promise in regards to cleaning up the wastes left behind from other types of reactors. How come these aren't developed more actively? What are the factors that keep the development back?

You’re correct that MSRs have promise for cleaning up waste from other reactors. Only about 5% of the atoms in nuclear fuel have fissioned when the fuel is considered “spent”, but the residuals of fissioned nuclei will “poison” the fission chain reaction (by absorbing neutrons) so that it cannot continue. Additionally, the life of fuel in a reactor is limited by the radiation damage from neutrons on the metal cladding around the nuclear fuel - too much time in the reactor will weaken the cladding beyond its design limits, so the time fuel can spend in the reactor is limited.

MSRs are nice because you don’t need to worry about either of these issues. You can chemically separate the fission products that disrupt the chain reaction, and material science concerns are not an issue since your fuel is liquid.

As you mentioned, MSRs have shown good promise for recycling fuel from other reactors - you essentially dissolve the fuel from traditional reactors into MSRs and let it fission away. There are a couple of technical concerns with this, MSR fuel tends to accumulate certain isotopes (e.g. Cm-244, which generates a significant amount of heat, making it a significant concern with long-term repository storage). Fast reactors (i.e. reactors that rely on high-energy, or “fast”, neutrons for their fission chain reaction) can actually destroy Cm-244 and other heat-generating isotopes, but they generally do not use molten/liquid fuel. However, there are a couple of chloride-based molten salt fast reactor designs that have been gaining some momentum in the community, and the day may come when we see fast-spectrum MSRs used to burn fuel from other reactors.

So why aren’t MSRs pursued more actively? Because fuel cycle issues don’t currently limit nuclear reactors. They will eventually, but they're not a significant concern today. Nuclear reactors don’t produce very much waste (all of the waste from ~60 years of nuclear power could fit on a single football field), and as u/nucl_thompson mentioned nuclear waste disposal is not a technical problem - it’s a political problem. We also have enough easily accessible uranium to fuel conventional reactors for the next 100-800 years, so there’s no pressing need to develop molten salt/thorium/fast breeder reactors in the near-term. The thing that limits nuclear reactors is economics. Natural gas is really cheap right now, and nuclear doesn’t receive the same kinds of subsidies as wind/solar, so nuclear plants are seen as a risky investment.

The economics of nuclear could certainly change in time - a carbon tax would likely fix things, and just building some plants would probably help too. We were churning out nuclear plants like crazy in the 70’s and 80’s, and now we’re hardly building any. The US capability for building nuclear plants has atrophied, and building a new plant today is about 2-4 times as expensive as it used to be (even adjusted for inflation). If we start building enough new nuclear plants again, then the economies of scale will kick in and make nuclear significantly less expensive.

Physics question for you: I have some background in physics at the nuclear scale (Physical Chemistry), and understand some of the basics of how nuclear interactions work (de Broglie, neutron cross-sections, etc.), but most of that is surface knowledge or stuff for chemistry, not nuclear physics.

So my question is, could you explain the difference between fast spectrum and thermal spectrum reactors?

Fast spectrum reactors primarily use high energy (i.e. fast) neutrons for their fission chain reaction, and thermal spectrum reactors use low-energy (i.e. thermal energy) neutrons for their fission chain reaction. All fission neutrons are emitted at fast energies, so thermal reactors remove energy from these fission neutrons by making them collide with light materials (i.e. hydrogen, carbon, beryllium, etc.). These light materials are known as "moderators."

Why does this matter for nuclear reactors? The probability of causing a fission (i.e. the neutron's fission cross section) is much higher for thermal neutrons than for fast neutrons, so it's easier to sustain a chain reaction for a thermal reactor than for a fast reactor.

However, fast reactors have their own advantages, namely because fission events release more neutrons when caused by fast neutrons. Fast fissions release so many more neutrons that it's possible to design fast-spectrum breeder reactors, where you make more fissile fuel than you consume by converting non-fissile U-238 (or Th-232) into fissile Pu-239 (or U-233). In fast breeders you need one neutron to carry on the chain reaction, and another to be absorbed by U-238/Th-232 to create another fissile isotope to replace the one that was just fissioned. Thermal-induced fission reactions generally don't release enough neutrons to allow for fuel breeding (although thorium-based MSRs are the exception to this rule).

who are the top 1-2 most important current females you know of in nuc energy or anything energy?

most important = most impactful contribution that has seen / is seeing positive results / effects

Definitely Rita Baranwal, as u/FlavivsAetivs mentioned. I'll also mention Kristine Svinicki, who is currently the Chair of the Nuclear Regulatory Commission. I haven't been very involved with NRC policies in recent years, but I did get to talk with Kristine several years ago and I remember her having an excellent vision on the role and direction of the NRC.

I'd also mention Angela Chambers, who leads the DOE/NNSA's Nuclear Criticality Safety Program. I do research on criticality safety and interact with Angela somewhat regularly, and it seems like she's doing an great job!

It's also worth mentioning that the current President and the President-elect of the American Nuclear Society are both women in nuclear!

I’m concerned about climate change and believe nuclear power is one of our best options for combating it. What’s the most effective way I can encourage the construction of new plants in my area, as a regular citizen? Should I be raising public awareness and talking to politicians? Or can I somehow invest in them directly?

not on the panel disclosure I would say the first step to encouraging the use a nuclear in your area is to get an idea of what your energy mix currently looks like. Maybe you have a plant nearby that can use support at NRC community meetings, on local news channels, or just in the general public perception. But if you dont have any plants close by you probably have gas or coal plants close by. A great way to start is to just get in contact with your local and state politicians(I know i try to email or call as often as a I can). If you are looking to go a more direct approach i believe you can email companies directly, just to say that you hope they would consider your community for a future project. Chances are if there are coal plants nearby, they will have to be replaced in the near future. So try to push for nuclear to be the replacement!

Attending NRC community meetings is definitely helpful! I attended a few in Oak Ridge/Knoxville, and NukeE's are often too busy to attend these meetings (which is a shame!) Having any pro-nuclear representation at these meetings definitely helps, and just standing up and saying that you support nuclear power helps a ton!

Hi Nick! Question for all, should we be testing weapons again to inform our numerical models and overall Verification and validation of those models? What are the drawbacks and pros? Thanks!

Personally, it might help with modeling, but we shouldn't start testing nuclear weapons again.

The US has signed the Comprehensive Nuclear Test Ban Treaty, which states that we will not test nuclear weapons, or participate in the testing of nuclear weapons. We do perform subcritical nuclear tests, which help validate weapons simulations.

So the pros of full scale testing would be better data, but the cons would be potential world wide condemnation, and could lead to other countries testing weapons as well.

Some additional info, prepared with help from Rian:

Although the U.S. maintains readiness to conduct an underground nuclear explosive test if necessary, the U.S. continues to observe the 1992 nuclear test moratorium (we want other countries to as well) and have been able to continually certify that our nuclear weapon stockpile is safe, secure, and effective. I would refer you to the Annual Department of Energy Stockpile Stewardship Report to Congress that provides more detail regarding the extensive technical activities involved (including verification and validation efforts). This is consistent with current U.S. policy as stated in the 2018 Nuclear Posture Review that "The United States will not resume nuclear explosive testing unless necessary to ensure the safety and effectiveness of the U.S. nuclear arsenal, and calls on all states possessing nuclear weapons to declare or maintain a moratorium on nuclear testing.” 

Do you think it is possible to create a fusion reactor that actually works in as sustained way. That is, one that generates electricity for low cost for the masses?

For fusion reactors to succeed we certainly need to hit breakeven (i.e. designing a fusion reactor that produces more energy than it takes to run) and stabilize the fusion plasma so that it produces a steady source of energy, but IMO the biggest challenge to fusion power is material science and radiation damage.

Each fusion reaction emits a high energy neutron, and these neutrons rip through materials and make the entire plant radioactive. Fusion plants actually produce more radioactivity than fission plants thanks to these neutrons (although the radioactivity from fusion plants has a half-life of about 12 years, making it less long-lived than radioactivity from fission reactions). The real kicker here is the radiation damage: being exposed to that many high-energy neutrons weakens and eventually destroys whatever material is used to contain the fusion reaction (i.e. the "inner wall" material). A production-level fusion plant might have to shut down once every year or two to replace the entire inner wall, which could itself take a year or two and would expose workers to a ton of radioactivity. Running a plant for 2 years before shutting it down for another 2 years makes for very bad economics, and it's possible that fusion reactors may never be feasible due to economics.

This radiation damage issue in fusion reactors is so bad that nuclear engineers joke that we'll have fusion reactors right after we get enough "unobtainium" to use for the inner wall.

There is some hope for fusion reactors: aneutronic fusion reactions (i.e. fusion reactions that don't emit any neutrons, and thus would cause significantly less radiation damage). The downside here is that aneutronic fusion reactions require even more temperature, pressure, and plasma stability than conventional Deuterium-Tritium fusion reactions. Until we hit breakeven for D-T fusion, there's no hope of achieving aneutronic fusion reactors.

what's the best youtube or site to efficiently learn basics of energy stuff if anyone knows?

What Is Nuclear is pretty good too! Paging u/whatisnuclear !

measurement is a big/huge everywhere in every single field

what's the most advance tech/thing that is used to measure at this lab? what does that thing basically do? what's the main flaw of that most advance thing?

It's hard to pick one most advanced thing that labs measure, but I will point out the LANSCE facilities at LANL. LANSCE is a high-energy linear accelerator that uses high-energy protons to produce neutrons for a wide variety of experiments. Some of these experiments include isotope production, proton radiography, and nuclear data measurement. I'm actually giving a lecture on nuclear data measurement tomorrow, and the ELI5 version is that measuring nuclear data involves solving the Schrodinger Equations for neutron-nuclei interactions. We can't solve these equations directly, so we instead develop models that are fitted to nuclear data measurements. These measurements require producing neutrons with very finely tuned energies and measuring interaction probabilities for these neutrons. The quality of our depends on how precisely we can tune the energies of these neutrons, so getting finer neutron energy resolutions would improve these facilities.

It's also very much worth noting that LANL has a wide array of plutonium characterization facilities. From Rian:

Los Alamos National Laboratory has the nation’s only facility capable of handling large quantities of plutonium for manufacturing pits and power sources and for conducting basic R&D.  I would not call it a flaw, but working with plutonium is not easy because of the safety and security concerns that are unique to this element!  

Sandia National Laboratories have a ton of neat experimental facilities, including the Z Machine, the ACRR, and some really nice experiments that we use to confirm the accuracy of nuclear data. Sandia is also where they conducted these awesome tests on spent fuel shipping casks, and also these awesome tests that simulate what would happen if someone crashed a airplane into the side of a nuclear power plant.

Lastly, I'll also mention that UNM has its own small nuclear reactor (of which u/CarlWillisNuclear is a Senior Reactor Operator!) Our students actually get to operate the reactor as part of their coursework - this is all done under supervision, of course, but our reactor is so small and so well-designed that you couldn't get it into an unsafe configuration even if you tried.

When used fuel is moved from a civil nuclear reactor to a fuel pool, how many hours (minimum) have already passed since the fuel was actually in use? How many hours need to have passed since the fuel was in use, in order for the fuel rods to not get dangerously hot if they are not immersed in water?

After spending at least one year in the spent fuel pool, fuel can be placed into dry cask storage. When placed into dry cask storage, the fuel is placed into a sealed container that is surrounded by an inert gas, and conductive/convective heat transfer with air around the outside of the cask is sufficient to keep the fuel at a safe temperature. Dry cask storage is nice because the spent fuel can stay in the casks more-or-less indefinitely. Because of dry casks, nuclear waste disposal isn't a problem we need to solve anytime in the near future - the waste is perfectly fine sitting in dry casks on concrete pads next to nuclear plants until we solve the debate on the politics of nuclear waste (which could take awhile!)

I don't know off the top of my head how long it is between when the fuel moves from a reactor into the spent fuel pool after an outage, but I don't think it's a huge amount of time (outages are expensive because you need to buy replacement power for the reactor, so they tend to be as short as possible). Upon shutdown nuclear fuel produces about 7% of the power of an operating reactor (due to the radioactive decay of fission products), but this decreases very rapidly.

what's the most important thing anyone that knwos nothing about nuclear energy (or anything any topic) should know about it?

One fission reaction releases about 50,000,000 times as much energy as one coal combustion reaction. Nuclear is extremely energy-dense, which means that it produces a relatively small amount of waste and consumes requires a very small amount of land.

Also, nuclear reactors are very safe - they are designed so that the reactor will shut itself down if the fuel temperature increases too much. Some designs even have passive cooling, meaning that you can break literally every cooling pipe in the reactor and the reactor will stay at a safe temperature (due to natural circulation in the coolant, or natural convection around the reactor vessel).

Do you think nuclear power is sustainable going forward towards a “greener” future? Or do you think as wind/ solar/ and hydro advance that nuclear power will be phased out because of the level of risk the waste created poses?

I think that nuclear power is necessary for any carbon-free energy portfolio.

Hydro is great, but most of the rivers in the US that are suitable for hydro power already have dams. There's not much room for growth in hydro power.

Wind in solar are great in some places, but their downside is that they are extremely variable sources of electricity. They make lots of power when the sun is shining and the wind is blowing, but we have to replace that power somehow when it's not windy or sunny. To make matters worse, wind and solar can sometimes produce too much power, which isn't great for electric grid stability and leads to negative electricity prices. Advancements in energy storage technology can help mitigate these issues, but those advancements would likely involve battery technology, which is notoriously bad for the environment. In many ways wind and solar are fortunate to avoid most of these issues because they produce so little power right now - once they start generating more than 10-20% of our electricity (they generate 8% of our electricity now), they will need to confront these limitations.

In my ideal energy portfolio, we would have hydro wherever we can, wind and solar where it makes sense, and we would use nuclear power to make up the rest (probably >50%) of the energy load. Current PWR reactors are not very good for adjusting to rapid changes change in energy demand (which would happen if you have a significant source wind/solar generation), but other reactor designs (BWRs and some next-generation designs) can be used for load-following.

I know you guys know tons of awesome women in nuclear science and engineering, why didn't you include at least one in this group of experts?

Originally this panel included a woman in nuclear who's kicking butt all over LANL, but unfortunately she was on travel during this AMA and couldn't participate. I should mention that the current President and the President-elect in the American Nuclear Society are both women, and it seems like the gender balance in nuclear has become much more balanced in recent years!

what do you feel is the most fascinating thing chemE ppl can do that isnt related to https://en.wikipedia.org/wiki/Los_Alamos_National_Laboratory

and why do you feel that way?

If I was a ChemE in nuclear I would want to work on radioisotope pharmaceuticals, such as Ac-225. Cancer cells have a much higher metabolism than normal cells, and the idea with radioisotopes is to attach a radioactive nuclide to glucose (which is consumed rapidly by the cancer cells). Once the radioisotopes are in the cancer cells, you can either locate the tumor by using detectors to track where the isotope's radiation is emitted, or you can bump up the dose of the radioisotopes to the point where they will kill the cancer cells. This avoids intrusive surgery and spares your healthy cells from receiving a significant dose by turning cancer's high metabolism against itself!

I have some work on advanced ceramics and ceramic matrix composites for next gen nuclear reactors. Much of the work in this area focuses on SiC/SiC for fuel rods; however, I think there are some other applications for non SiC/SiC ceramics. One example, say, a molten salt heat exchanger than can operate up to 1000C without needing EBCs. So, as I push my research forward, what are the worthwhile endeavors in your opinion? Where do you see advanced ceramics playing a role in next gen nuclear?

I think SiC fuels will definitely play a role in next-generation reactors, be they in the form of SiC-clad accident-tolerant fuel rods, or in TRISO fuel. In fact, there's a lot of interest in the DoD right now in designing a TRISO-fueled reactor that can be deployed to military bases. The DoD pays upwards of $400/gallon for diesel fuel at bases, and about half of all military fatalities occur due to supply chain logistics. Designing a reactor that could be parked on a forward operating military base could save a lot of money, and a lot of lives.

One of the teams in UNM's Senior-level Reactor Design class actually looked into designing one of these reactors, and they did a really good job.

What are you gonna be for Halloween?

Gonna do a Tommy Wiseau/Greg Sestero couples costume. Oh hai Reddit!

I am 16 and really into nuclear power.

My questions

1.) Could we see (LFTR) Liquid Fluoride Thorium Reactors being used for power generation in the future?

2.) Do you think there is hope with the the presidential candidates, Andrew Yang and Cory Booker with their views of supporting nuclear energy?

3.) I know a bunch about the Three Mile Island plant. Was it not smart to have only one working phone line at the plant in the late 70's that made it harder to get in contact with the operators at the plant during the incident in 1979?

4.) How do you personally feel about the Pennsylvania State government not financially backing the owner(s) of reactor one at Three Mile Island. That lead to the permanent lowering of the control rods and the plant being disconnected from the power grid?

5.) How much hope is there for using thorium as the main fuel in the future? (At least until we figure out hydrogen fusion and make it practical.)

6.) What can I do to get myself more involved in the world of nuclear as still being a high school student?

Thanks for the awesome r/IAma.

1) Possibly, I think a large government program to build nuclear reactors and other low carbon sources will be needed to fight climate change.

2) Senator Booker has been a strong supporter of nuclear for years, and has helped to enact pro-nuclear legislation. Hopefully he continues to be a good advocate and partner.

3) I don't really know anything about the phone situation.

4) It's a shame that TMI-1 was closed. It was a safe plant and had a license to operate for another ~15 years. Some other states have been able to pass legislation to prevent closures like this - NY, NJ, and IL all passed bills to keep plants open. Hopefully PA does too.

5) Thorium really isn't a fuel - it's fertile. If you put it in a reactor alone, pretty much nothing would happen. However, if thorium is bombarded with neutrons, some of the thorium can become Uranium-233, which also fissions like U-235. India has been doing some research with thorium, but you'd need new reactors to actually be able to make use of thorium/U-233. There are companies out there working on it though!

6) If you can, join the American Nuclear Society. They have great resources, and a digital magazine with tons of news. Also, read all the news you can about the industry, and try to get an summer internship if there is a nuclear company nearby. You can also read introductory books - Introduction to Nuclear Engineering is a good one if you have some physics background.

Thanks, I am currently in Algebra 2/trig for math the top class available for my grade. And for science class, planing to take physics next year. And physics 2 the year after that.

Nice, keep up the good work!

Adding to what Nick said,

1.) Could we see (LFTR) Liquid Fluoride Thorium Reactors being used for power generation in the future?

I addressed molten salt breeder reactors in a previous post. They're a cool idea, and we will certainly need to build breeder reactors eventually, but right now nuclear plants are not limited by a lack of uranium - they're limited by economics.

​

2.) Do you think there is hope with the the presidential candidates, Andrew Yang and Cory Booker with their views of supporting nuclear energy?

The politics of nuclear is definitely interesting, and usually frustrating! Republicans deny that climate change exists, and Democrats deny that nuclear is the solution! I definitely hope that Andrew Yang, Cory Booker, and other pro-nuclear folks have a stronger influence on our policies, and there's no reason why nuclear should be so controversial. For Republicans it should represent energy dependence and energy security, and Democrats should realize that it's our largest source of carbon-free electricity! Hopefully this will change with better PR and organizations like Generation Atomic!

​

6.) What can I do to get myself more involved in the world of nuclear as still being a high school student?

A couple of things in addition to what Nick said: The American Nuclear Society local chapters usually work with the Boy Scouts of America and Girl Scouts of America to offer "Nuclear Science" merit badges. If you're a part of either of those organizations, I'd recommend seeing if there are any merit badge workshops near you. UNM students help award 100+ GSA Nuclear Science merit badges last year, and we're always interested in teaching more people about nuclear.

I would also encourage you to look into nuclear engineering as you get close to graduating from high school. There's actually a shortage of nuclear engineers right now, so you can get a pretty competitive salary right out of school with an undergraduate degree. There are 20+ NE programs nationwide, and don't be afraid to visit colleges to see what they offer (UNM has fairly cheap tuition, and we offer some great scholarships for out-of-state students!) If you're lucky, they might even give you a tour of their research reactors!

Computer science student here. How did you guys keep going when times were tough? Are any of you from lower-class households?

Honestly I don't know how much stress I can take between studying, working and dealing with family strife. I know there's no 'perfect solution' for decompressing, but how do you guys make the most of your free time? Nothing I do seems to help me relax anymore...

I came from a solidly middle-class household, but at UNM we have plenty of students who come from lower class households - students who are working multiple jobs while in school, who have kids, or who entered college after spending years in another career or in the military.

All I can say is to stick with it, it will all definitely be worth it once you land that first serious job after graduation. Also, UNM has free counseling resources for students (and faculty!) and many other universities do too. Mental healthcare unfortunately has a stigma in the US, but I would always encourage you to seek out counseling if things ever feel too tough, or if you just need someone to talk to or bounce ideas off of.

Personally, I treat myself like a houseplant with complicated emotions. Get enough sleep, stay hydrated, get some sunshine/exercise, don't eat junk, and make time for your hobbies when you can. Doing these things won't guarantee that you feel good, but you're not giving yourself a fair chance if you're not doing these things.

For hobbies, I enjoy cycling, swing dancing, cooking, hiking in the summer, skiing in the winter, playing video games when I can make time for it, and brewing beer. Cheers!

Is there any method to reduce the half life of waste nuclear materials?

Yes and no. Without access to a black hole, you can't change the half-life of an individual isotope, but you can separate the super-long-lived stuff from isotopes with shorter half-lives. Most of the radioactivity in spent nuclear fuel is due to very long-lived actinides - stuff like americium, curium, berkelium, etc. These isotopes can be used as fuel in fast reactors, so you can chemically separate (i.e. reprocess) the spent fuel, stick these actinides into a fast reactor, and wait until they fission.

After you remove these actinides and all of the isotopes that have medical applications (e.g. Mo-99 and Ac-225), the isotopes that are left in nuclear waste (mostly Co-60 and Sr-90) have a half-life of about 5-30 years. The rule of thumb is that radioactivity needs 10 half-lives of time until it is essentially stable, and it's very easy to build a container that can hold nuclear waste for 50-300 years. (There are plenty of houses and even trees that have been around for longer than that!)

What about bacteria that eat nuclear waste?

https://www.newscientist.com/article/mg23431211-300-radiation-eating-bacteria-could-make-nuclear-waste-safer/

I've heard about bacteria like that, but I admittedly don't know much about them. The premise from the article makes sense though - the bacteria can't reduce the half-life of waste, but if waste is a nutrient to them, then they could help immobilize the waste should a storage cask rupture.

Have you met Bill Gates?

I have not, but Jim Walther has! Bill brought his kids to the Nuclear Science Museum during a trip to Albuquerque several years ago.

Several of my friends at TerraPower have also met Bill - he sometimes attends the larger TerraPower meetings, and he's invited a big group over for dinner in the past. I've heard good things, and apparently he has an outstanding memory for technical details.

Hello! Thank you for doing this ama! I have some questions. For a bit of background, Im a senior in NE working part time at my schools test reactor.

1. I know you guys are required to like MCNP but I wanted to ask about your honest opinion between MCNP and Geant4

2. My senior design focuses around accident tolerant fuel clad coatings and I wanted to ask if you guys have any coatings/coating methods that particularly pique your interests if any of you guys are familiar with the field?

3. If any of you guys did NE for your undergraduate, how was your school life like? I only have my schools program to base off, and I want to know if everyone had it as hard as I have it now or if my program is just excessive.

4. What would be the best things to do for an undergraduate to get a summer internship at los alamos?

5. My understanding of transport is a little iffy, so I wanted to ask about how computational codes compute transport because I know computing transport is extremely difficult?

Thank you!

1. Honestly I've never used Geant, but MCNP is certainly an outstanding code. Forrest Brown has done some amazing work in MCNP, and they have a really talented, young team. Another code worth mentioning is Serpent - its lead developer, Jaakko, is extremely bright, very nice, and fun to have a beer with!
2. Unfortunately I don't know much about SiC coating methods, but it seems like a very useful and timely senior design project!
3. I did NE for all three of my degrees. Junior year was tough, and senior year was crazy. It was certainly difficult, but I came out for the better because of it. I thought things got easier in graduate school - you get the chance to specialize in a specific area, and it's enormously exciting when you start to become one of the experts in your field!
4. The best way to get an internship is to know someone who's looking to host a summer student. Your professors can give you these connections, and you can also make them yourself at ANS conferences. A good GPA (> 3.5) will make all of this process much easier. Other than that, having some experience in the area where you want to intern can help, i.e. having coding (C++ or Fortran) experience if you want to work with the MCNP team, having taken a criticality safety class if you want to intern with the Nuclear Criticality Safety Division, etc. Having experience with your school's research reactor could position you well for work with LANL's critical experiments team (paging u/nucl_thompson !)
5. Transport codes all solve some approximation of the Boltzmann Transport equation. You essentially generate a big matrix by discretizing the problem in some way, and solving that matrix gives you the values of the neutron flux in your system. Discretizing the problem can get very complicated, as the neutron flux is a function of space, energy, and direction in the BTE. Different methods discretize the problem in different ways, but you can use the diffusion approximation to remove the angle/direction variables, or solve for a limited set of discrete angular fluxes (i.e. the Sn method), or homogenize regions spatially to reduce the number of spatial cells, or use the multigroup approximation to homogenize in energy. There are researchers who spend their entire lives developing more efficient ways to solve the Boltzmann Equations, and it's definitely not easy!

Would you or any other nuclear scientist ever consider running for a major political office? It seems both political parties willfully refuse to acknowledge that it's our best option.

From Rian:

There are plenty of nuclear engineers and scientists that show a strong interest in national policy issues, and find ways to participate at various stages of their career and education. For example, there are various programs like the Nuclear Engineering Student Delegation to Washington D.C. where students meet with nuclear policy makers and discuss key nuclear issues. Several of us on this thread have participated, myself in 2004 where the highlight was our meeting with then Senator Joe Biden to discuss the pertinent nuclear issues of the day. Many of the NESD alumni find their way back to DC at some point in their careers (e.g. one person from my year ended up at the White House National Security Council working on nuclear energy issues). There are many other programs at technical universities, congressional fellowships, etc... that you can find that provide additional opportunities. With all that said, I do hope more nuclear professionals and scientists in general consider running for political office which is a totally different ‘beast’ that I cannot personally speak to.

Hi, thanks for doing this AMA! I just got here, so I'm not sure if this has been asked yet. How far are we realistically from a working, stable fusion reactor - if it is even possible - in your opinion. Does the math ever work, will we see it in the next 50 years?

Welcome to the AMA! I answered a similar question previously:

For fusion reactors to succeed we certainly need to hit breakeven (i.e. designing a fusion reactor that produces more energy than it takes to run) and stabilize the fusion plasma so that it produces a steady source of energy, but IMO the biggest challenge to fusion power is material science and radiation damage.

Each fusion reaction emits a high energy neutron, and these neutrons rip through materials and make the entire plant radioactive. Fusion plants actually produce more radioactivity than fission plants thanks to these neutrons (although the radioactivity from fusion plants has a half-life of about 12 years, making it less long-lived than radioactivity from fission reactions). The real kicker here is the radiation damage: being exposed to that many high-energy neutrons weakens and eventually destroys whatever material is used to contain the fusion reaction (i.e. the "inner wall" material). A production-level fusion plant might have to shut down once every year or two to replace the entire inner wall, which could itself take a year or two and would expose workers to a ton of radioactivity. Running a plant for 2 years before shutting it down for another 2 years makes for very bad economics, and it's possible that fusion reactors may never be feasible due to economics.

This radiation damage issue in fusion reactors is so bad that nuclear engineers joke that we'll have fusion reactors right after we get enough "unobtainium" to use for the inner wall.

There is some hope for fusion reactors: aneutronic fusion reactions (i.e. fusion reactions that don't emit any neutrons, and thus would cause significantly less radiation damage). The downside here is that aneutronic fusion reactions require even more temperature, pressure, and plasma stability than conventional Deuterium-Tritium fusion reactions. Until we hit breakeven for D-T fusion, there's no hope of achieving aneutronic fusion reactors.

1. What's the real cost of nuclear waste management, is it expensive?
2. Did we underestimate the nuclear power generation if we don't include the waste management cost and the risk cost?
3. Somebody say it takes so long to build up a nuclear power plant, is it true?

Nuclear power plants actually pay for the cost of disposing of nuclear waste, as per the Nuclear Waste Policy Act. Every nuclear power plants in the US pays 1/10th of a cent per kWh produced, and this fee goes towards disposing of nuclear waste. These funds have paid for the construction of the Yucca Mountain facility, and even after paying for Yucca Mountain they still have some $48 B in the bank. I briefly lived in San Diego years ago, and they actually itemized the cost of nuclear waste disposal on my electricity bills - it was minuscule compared to everything else.

Nuclear power plants also pay for insurance to cover any nuclear-related accidents - presently they pay $450 M in annual insurance fees.

Hello, thank you for taking time out of your days to answer our questions. I have two questions. First, red or green? Second, where do you stand on the hatch vs Colorado debate? Thanks!

I prefer green to red, but both are amazing. I usually order Christmas. Red definitely has its place though, I made a mango-red chili chocolate cake this weekend and it was excellent. My "next homebrew to make" list definitely includes a beer-version of that cake.

Colorado green chilis ain't got nothing on Hatch!

I got one: not sure if someone has asked this already, but anyways! When do you think the mankind will be able to develop fusion technology and use it in reactors? Is its huge cost even worth it or should we gravitate toward other sources of energy?

Good question! I answered a very similar question in an above post.

Have you seen any aliens in New Mexico yet?

No, but I have gotten really good at Naruto-running.

Three questions:

Do you prefer alpha, beta, or gamma decay, and why?

What is cooler - pair production or pair annihilation?

Was Compton scattering named after violent events in south central L.A.?

Thank you for your input on these crucial questions.

Do you prefer alpha, beta, or gamma decay, and why?

I prefer gamma because it usually happens after a nucleus absorbs a neutron, which can produce some really cool isotopes (e.g. californium-252, einsteinium-254).

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What is cooler - pair production or pair annihilation?

Definitely pair production. There's something about having a photon excite matter from the imaginary realm into creation that seems magical. One could even say, "exciting."

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Was Compton scattering named after violent events in south central L.A.?

It is a little-known fact in nuclear, but the namesake of Compton scattering (Arthur Compton) was actually a huge fan of Dr. Dre. You might wonder how this is possible, since Arthur Compton died 24 years before N.W.A. released their first album, but Arthur Compton actually used his time machine to visit the future and download a bunch of Dre songs to his iPod. After becoming a fan of Dre, Compton traveled back in time and persuaded his ancestors to change his name to Compton. Fun facts!

From my perspective it doesn't seem like there is much resistance to new nuclear technologies from the people I know. To your knowledge have there been any national poles that show what the percentages are with regard to supporting nuclear or not?

There are! This Gallup poll shows that people are fairly split on nuclear power. If I had to guess, I'd say that public support for nuclear power started declining after Fukushima in 2011, and is probably low right now because of the perceived success of renewables (i.e. people thinking "if wind and solar are so great, why do we need nuclear?") I think renewables are great, and that they undoubtably have a place in our energy portfolio (especially in sunny New Mexico!), but we shouldn't ignore that solar produced about 8% as much electricity as nuclear in 2018. We're going to need nuclear if we want to be serious about stopping climate change.