#High Flux Isotope Reactor

[thirdchoiceurl]

Oh cool whats NAA? Also I've heard of using neutrons to treat nuclear waste, but I was never able to find any recent papers on it? Or maybe I wasn't using the correct search terms.

NAA stands for Neutron Activation Analysis. There’s a few varieties, but in our lab we typically do Delayed Gamma Neutron Activation Analysis or DGNAA. We bombard samples with a strong flux of thermal neutrons from the reactor, and the neutrons are absorbed by all manner of atoms in the material. In doing so, the stable nuclei are transmuted into short-lived radioisotopes that then decay via beta emission and emit gamma photons with characteristic energies. By using a scintillator and photomultiplier with an MCA (or the HPGe setup if it’s available (it never is) and we have the nitrogen (we never do)), we can then build a gamma ray spectrum that tells us exactly which trace elements are in the sample and, through cross-section analysis, we can get good measures of exactly how much of each element is present.

It’s an incredibly powerful tool for detecting and characterizing trace elements, with sensitivity several thousand times beyond purely chemical methods. One of the recent experiments we did analysis for involved mapping ancient trade routes in Central America by using pottery shards to identify the characteristic minerals of specific clay deposits and correlating them with how far they had traveled from their origin point. The amount of information that can be found from the atomic fingerprint of an object is astounding.

My pet project (the “refried beans” theory of nuclear waste as some of my buddies call it) is typically referred to as waste transmutation. High-level nuclear waste is produced from the processing of spent fuel, which is laden with highly radioactive fission products that pose a serious danger to anyone who may carelessly handle it in the present or future. While many of these fission products are short-lived and decay almost completely while the fuel waits in the cooling pool of its reactor, some isotopes (especially Caesium-137 and Strontium-90) have half-lives in the range of decades and product abundance above 5%. These nuclides are in the sour spot of maximum danger, with half-lives short enough to be ferociously radioactive even in tiny quantities and long enough that one can’t simply wait for them to decay significantly in a human lifetime.

My project, which is currently a bunch of spreadsheets and slideshows I use to try to convince someone to let me mess around with some highly corrosive extremely radioactive nitric acid salts, involves intercepting the fission product waste after reprocessing separates out the industrially useful heavy radioactinides and placing that waste back into the neutron flux of a reactor or accelerator. In doing so, preliminary simulations show that significant portions of the long-term waste activity can be reduced as the hardy and problematic long-lived isotopes are transmuted into short-lived ephemeral products that decay into stable nuclei in a matter of days rather than centuries.

This process isn’t without its drawbacks and hazards. Waste to be transmuted must be carefully chemically treated to remove elements like Calcium or Chlorine which can absorb neutrons from the beam and become new nuclear waste. Another issue is that the transmutation process makes the waste drastically more radioactive for a brief period of time. No fission product exists can be transmuted directly into a stable isotope, we can only pre-empt their decay. In time, the refried waste and the untreated waste will release the exact same quantity of radiation, and forcing it to undergo centuries’ worth of decay in a matter of weeks will make it extremely hot both physically and metaphorically.

It’s a work in progress.

[nelc]

HFIR Refueling: July 2015 by Oak Ridge National Laboratory

Via Flickr:

The High Flux Isotope Reactor at Oak Ridge National Laboratory is the highest flux reactor-based source of neutrons for research in the United States, and it provides one of the highest steady-state neutron fluxes of any research reactor in the world. Operating at 85 MW, an average fuel cycle for the HFIR generally runs for approximately 26 days—depending on the experiment loading for that cycle—followed by a refueling and maintenance outage for various scheduled calibrations, modifications, repairs, and inspections.

The reactor underwent routine refueling in July 2015, as seen in these photos. While submersed, the spent fuel emits a luminescent blue glow due to Cherenkov radiation, in which shedding electrons move through the water faster than the speed of light. Once removed from the reactor, spent fuel is then relocated into an adjacent holding pool for interim storage.

This image shows the removal of a HFIR fuel element as it passes through a hatch in the top head of the reactor vessel during defueling operations.

Image credit: Genevieve Martin/ORNL

[cetaceous]

Refueling the High Flux Isotope Reactor, July 2015 Oak Ridge National Laboratory, Oak Ridge, Tennessee image credits: Genevieve Martin & Jason Richards/ORNL

[materialsscienceandengineering]

Thorium-228 supply ripe for research into medical applications

As a medical isotope, thorium-228 has a lot of potential—and Oak Ridge National Laboratory produces a lot.

That's one reason ORNL researchers are especially excited about studies looking at different medical applications for the radioisotope. ORNL produces large quantities of Th-228 for the Department of Energy's Isotope Program as a byproduct of actinium-227 production.

Both Ac-227 and Th-228 are created when ORNL irradiates radium-226 in the High Flux Isotope Reactor. Maximizing the production of Ac-227, used in cancer treatments, is the goal, but the process also produces a significant amount of Th-228.

Th-228 is used to make radium-224/lead-212 generators. These generators allow the radium-224 extracted from Th-228 to decay over time and produce lead-212 and bismuth-212 for research on targeted alpha therapy, attacking metastatic skin cancers and neuroendocrine tumors with minimal damage to surrounding tissue.

Read more.

[sciencespies]

Scientists Take Fundamental Measurements of Einsteinium for the First Time

https://sciencespies.com/news/scientists-take-fundamental-measurements-of-einsteinium-for-the-first-time/

Scientists Take Fundamental Measurements of Einsteinium for the First Time

Using an unprecedentedly small sample, scientists have taken the first fundamental measurements of the highly radioactive element einsteinium. The results were published on February 3 in the journal Nature.

Einsteinium was first created in 1952 in the aftermath of the first hydrogen bomb test on the island of Elugelab, which is now a part of the Marshall Islands in the Pacific Ocean. But the element’s most common form, on the rare occasions that it is produced, degrades by half every 20 days. Because of the element’s instability and the inherent dangers of studying a super radioactive element, the last attempts to measure einsteinium were in the 1970s, Harry Baker reports for Live Science. The new research not only sheds light on einsteinium and other very heavy elements, but also gives future chemists a model for conducting research on vanishingly small samples.

“It is a very small amount of material. You can’t see it, and the only way you can tell it is there is from its radioactive signal,” says University of Iowa chemist Korey Carter, a co-author on the research, to Live Science.

The researchers worked with a slightly more stable version of einsteinium that takes 276 days to lose half its material. Every month, the sample lost about seven percent of its mass. To protect the sample—and the researchers—from its radioactive decay, the team created a 3-D-printed sample holder for the task.

“There were questions of, ‘Is the sample going to survive?’ that we could prepare for as best as we possibly could,” says Carter to Gizmodo’s Isaac Schultz. “Amazingly, amazingly, it worked.”

Einsteinium sits at the very bottom of the periodic table, in a row of heavy elements called called the actinides among neighbors like uranium and plutonium. All actinides are highly radioactive and most aren’t found in nature. When atoms get very big, like actinides are, it becomes difficult for chemists to predict how they’ll behave because they have so many sub-atomic particles with opposing charges that are barely held together.

For example, the particles around the outside of an atom are the negatively charged electrons, and the outermost electrons are called valence electrons. The number of valence electrons that an atom has determines how many other atoms it can form bonds with. Because einsteinium is so big, it’s hard to predict its valence value, but in the new paper, the researchers were able to measure it.

“This quantity is of fundamental importance in chemistry, determining the shape and size of the building blocks from which the universe is made,” writes Keele University chemist Robert Jackson in the Conversation. “Einsteinium happens to lie at an ambiguous position on the periodic table, between valence numbers, so establishing its valence helps us understand more about how the periodic table should be organized.”

The team got their einsteinium from the Oak Ridge National Laboratory’s High Flux Isotope Reactor. Normally, the Oak Ridge reactor makes californium, which is useful for things like detecting gold and silver ore. Californium and einsteinium have a lot in common, so the latter is often a byproduct of californium production. It’s tough to separate them, which is why the lab only got a very small sample of einsteinium—about 200 billionths of a gram—and even then, it was too contaminated with californium to conduct some of their tests.

The team bombarded a some of their einsteinium with high-energy light using the Stanford Synchrotron Radiation Lightsource in order to take measurements. In one result, the team found that while most actinides reflect a longer wavelength than the light shot at them, einsteinium does the opposite, and reflects shorter wavelengths. The team also found that when other elements bonded to einsteinium, the bonds were slightly shorter than they’d predicted.

“That tells us that there is something special about einsteinium, in that it doesn’t behave as we expected,” says lead author Rebecca Abergel, a chemist at the University of California, Berkeley’s, to Shamini Bundell and Nick Howe at Nature News.

#News

[atomic-operator]

HFIR’s Cherenkovlic Glow

The High Flux Isotope Reactor at Oak Ridge National Laboratory is the highest flux reactor-based source of neutrons for research in the United States, and it provides one of the highest steady-state neutron fluxes of any research reactor in the world. Operating at 85 MW, an average fuel cycle for the HFIR generally runs for approximately 26 days—depending on the experiment loading for that cycle—followed by a refueling and maintenance outage for various scheduled calibrations, modifications, repairs, and inspections.

[diffractor]

Nuclear Physics Infodump: Nucleosynthesis Part 3:

Prev

6: Rapidly adding neutrons (the r-process). Sure, adding neutrons is fine, but when you add them slowly (one a year or so) you tend to creep along a certain path in the table of isotopes. But what if you’ve got a really big neutron flux? Like, several neutrons being added per second. Then you keep getting neutrons until you get to the point where the isotope just can’t hold any more, and then it beta-decays (with a really short half-life) to the next isotope, which also has a shitload of neutrons, and decays with a short half-life…. When the process shuts off, everything beta-decays back down to the line of stability, and that’s how you get heavy elements and also cross the gap past bismuth to get thorium and uranium!

Well, only part of that is right, the part about beta-decaying back to the line of stability. People thought that supernovas did this (actually they don’t). So it was a mystery for a while, but now we know what does it.

It’s merging neutron stars! Neutron stars are pretty much a big ball of neutrons, that are kept as neutrons by immense pressure (free neutrons decay). So when neutron stars merge, sure you get a black hole, but there’s also a whole lot (about a solar mass) of neutronium being violently splatted into space in all directions. And it now doesn’t have the pressure keeping it stable, so it beta decays into however many protons it takes to be stable. So at least the “start with something really neutron-rich and have it decay to the stability line” part checks out. This makes everything from molybdenum to bismuth, and also thorium and uranium. Of course, the s-process makes a bunch of these as well. But for the rarer stuff made by the s-process, this is where most of it comes from. Specifically, if it’s between molybdenum and bismuth, and I didn’t say most of it comes from the s-process, most of it comes from a neutron star merger. This includes the rare noble metals, the (rarer) rare-earth elements, and all of the thorium and uranium. Thank a neutron star for your gold ring.

7: Something that removes neutrons or adds protons (p-process): 

Ok, so the combination of the s and r process makes almost all the types of elements. But they only make isotopes that are of the form [take a big wad of neutrons, let it beta decay until it has enough protons to be stable, there’s your produced isotope]. There are some isotopes (very rare isotopes, but they still exist), which can’t be made this way! They’ve got too many protons and not enough neutrons, and there’s another isotope with less protons and more neutrons where the beta decay will stop first. Where did they come from?

Well, we don’t really know. We’ve got some good candidates, but none of them alone are enough to explain all the rare proton-rich nuclei. (p-process for proton). One of them is the standard supernovas we dismissed earlier. If you hit a nucleus with high-energy gamma rays, it may knock out a few neutrons. So when a supernova goes off, the energy from the explosion may strip neutrons off some atoms, getting you small amounts of these rare isotopes. Also, when neutrinos hit a nucleus, they may be able to change a neutron into a proton-electron pair, so black hole accretion disks (neutrino wind from really hot matter) and supernovas can make some of them. There are other speculative sources.

Recap: And that’s it! The big bang, ordinary nuclear fusion, cosmic ray atom splitting, type Ia supernovas (nuclear fusion on steroids), slow neutron irradiation, neutronium decay from merging neutron stars, and stuff involving ordinary supernovas and neutrino winds and mysterious other processes.

8: Humans

Ok, we can’t replicate the big bang, and we’ve got enough hydrogen and helium around for it to not be worth it even if we could. Stars and Ia supernova produce enough of the standard nuclear fusion stuff, and it takes a lot of energy, again not worth it. Particle accelerator atom splitting has the problem that it just produces a big trash pile of random atoms, and you can’t make that much of them. That leaves the last three.

The s-process is replicable by just putting stuff next to an active nuclear reactor, nuclear reactions emit a bunch of neutrons into the environment. 

Humans have figured out how to do a p-process, because there are a few proton-rich radioactive isotopes useful in medicine (and you only need microscopic amounts), and those are made by either whacking a target with an intense radiation beam to make it lose neutrons, or whacking it with hydrogen/deuterium/helium to make it gain protons by fusion. This has very low yield, but you don’t need that much to start with.

Finally, the r-process in theory could be duplicated by adapting nuclear bombs for much lower yield (halfway between a nuke and a nuclear reactor meltdown) and a much longer neutron pulse and setting off about 10 of them next to your target, one every 1/10th of a second. Nobody’s actually done this though. We know it’s doable, we’ve found unusually neutron-rich isotopes in nuclear fallout, and there’s presumably room for engineering a nuke to maximize thermal neutron production and minimize a blast, but I don’t know how to do it.

Next

[fumpkins]

Chemicals track Fukushima meltdown :

Radioactive sulphur signal contributes to proof of disaster.

Radiation from the harmed Fukushima Daiichi nuclear power station in Japan was discovered in California not long after the mishap. TEPCO

Researchers in California are reporting raised levels of radioactive chemicals in the environment in the weeks following the catastrophe at Japan’s Fukushima Daiichi nuclear reactor. The measurements are the current proof that the reactors melted down catastrophically.

Scientists at the University of California, San Diego (UCSD), state that radioactive sulphur from the stricken power plant reached California in late March, 2 weeks after the crisis at Fukushima started. The sulphur is a spin-off of emergency situation treatments taken right away after the mishap. The work is released in the Procedures of the National Academy of Sciences1

On 11 March, the Fukushima Daiichi plant was shaken by a magnitude-9 earthquake and knocked with a 13- metre-high tsunami. The catastrophe knocked out emergency situation generators created to support systems that cooled the plant’s 3 running reactors.

In a desperate effort to slow heating and prevent an overall disaster, operators flooded the reactor cores with boric acid and sea water. However it didn’t work: in Might, the Tokyo Electric Power Business, which manages the plant, revealed that regardless of their best shots, the reactors at Fukushima Daiichi had melted down completely.

Chemical corroboration

The current measurements appear to validate that. For numerous years, Mark Thiemens, a chemist at UCSD, and his group have actually been determining climatic levels of a radioactive isotope of sulphur, 35 S, which is typically created by cosmic rays striking argon atoms in the environment. On 28 March, the group discovered levels of radioactive sulphur dioxide gas (35 SO 2) and sulphate aerosols (35 SO 4 -2) that were well above the natural background.

The chemicals positioned “no danger” to citizens in San Diego, states Thiemens. In reality, it took a year to even establish devices delicate sufficient to determine levels as low as these, he states.

Thiemens and his coworkers think that the radioactive sulphur was produced from chlorine in the sea water utilized to flood the reactors. The chlorine atoms most likely taken in neutrons from the destroyed nuclear fuel, and were transmuted into 35 S. They then left the reactor in both gas and aerosol kind and were spread out throughout the ocean by strong westerly winds.

AD

On the basis of designs, the group approximates that around 400 billion neutrons per square metre ‘dripped’ from the reactor cores at the time of the disasters.

Although 400 billion might seem like a lot, it’s small in contrast with the regular flux of neutrons inside a reactor, states Patrick Regan, a nuclear physicist at the University of Surrey in Guildford, UK. Regan states that the neutrons do not show that the melted reactors rebooted after the emergency situation started, however are a clear spin-off of sea water inside the reactors.

Thiemens states that the most considerable contribution of the measurement might remain in assisting scientists to much better comprehend how sulphates and other aerosols take a trip through the environment after a nuclear mishap. Fukushima supplied a single, well specified source of traceable radiation, he states. Follow-up research studies with Japanese coworkers “will be really considerable in distinctively dealing with how, and how quickly, radioactivity spreads”.

Recommendations

Priyadarshi, A., Dominguez, G. & Thiemens, M. H. Proc. Natl Acad. Sci. U.S.Ahttp://dx.doi.org/10.1073/pnas.1109449108 (2011).

New post published on: https://livescience.tech/2018/03/27/chemicals-track-fukushima-meltdown/

[indianfitnesscare]

New Dental Material May Revolutionize Implant Dentistry

New Dental Material May Revolutionize Implant Dentistry

Fernando Luis Esteban Florez, an assistant professor at the University of Oklahoma Health Sciences Center, College of Dentistry, is conducting research at the High Flux Isotope Reactor (HFIR) at the Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL) to try to change that. ‘Neutrons can be used to probe structures within organic tissues in a nondestructive way and allow to…

[man-and-atom]

As with many reactors around the world, both power and non-power types, the Petten HFR is supposed to be shut down not many years from now.  Especially with the longtime world-leading source, NRU at Chalk River, Ontario, now out of the picture, a serious problem in supplying radiopharmaceuticals has begun to develop.  The ability to co-produce two radioelements, technetium & xenon, in one operation certainly will help.

[sciencebulletin]

Tungsten isotope helps study how to armor future fusion reactors

The inside of future nuclear fusion energy reactors will be among the harshest environments ever produced on Earth. What's strong enough to protect the inside of a fusion reactor from plasma-produced heat fluxes akin to space shuttles reentering Earth's atmosphere? Zeke Unterberg and his team at the Department of Energy's Oak Ridge National Laboratory are currently working with the leading candidate: tungsten, which has the highest melting point and lowest vapor pressure of all metals on the periodic table, as well as very high tensile strength—properties that make it well-suited to take abuse for long periods of time. They're focused on understanding how tungsten would work inside a fusion reactor, a device that heats light atoms to temperatures hotter than the sun's core so that they fuse and release energy. Hydrogen gas in a fusion reactor is converted into hydrogen plasma—a state of matter that consists of partially ionized gas—that is then confined in a small region by strong magnetic fields or lasers. "You don't want to put something in your reactor that only lasts a couple of days," said Unterberg, a senior research scientist in ORNL's Fusion Energy Division. "You want to have sufficient lifetime. We put tungsten in areas where we anticipate there will be very high plasma bombardment." In Read the full article

[juniperpublishers-imst]

Nuclear Power from Lunar ISRU - Juniper publishers

Journal of Insights in Mining Science & Technology

Abstract

Thorium on the lunar surface can be transmuted into fissile uranium suitable for a controlled chain reaction to provide heat. Thorium is fertile, requiring bombardment by neutrons to become a suitable nuclear fuel. Oxides of thorium are dense and can be concentrated and beneficiated from comminuted regolith via inertial or thermal means. A neutron flux can be provided by encasing thoria within a beryllium and graphite vessel, which emits neutrons upon exposure to gamma rays or galactic cosmic rays. After a brief period at protactinium the transmuted material becomes U-233, a desirable fuel because decay product half-lives are below 100 years. When compressed into fuel pellets the uranium oxide is configured into a reactor through which a working fluid can extract thermal power. With regolith tailings as shielding such a reactor can operate safely for 30 years. A century later, the site can be harvested for specialty elements and then made available for other uses. The advent of launch-safe nuclear rockets in space greatly expands the potential for in situ resource utilization, a space-based economy, and profitable exploitation of the asteroid belt.

 Introduction

Lunar missions involving in situ resource utilization (ISRU) require ample supplies of thermal and electrical energy. Solar power is a poor choice, being diffuse, and intermittent. Operations in permanently shadowed regions (PSR) get no sunlight, inviting complex reflection or conversion and beaming schemes to power operations on the floors of ultra-cold craters. Nuclear power is an oft-cited option, as technology is readily available for the reactor to only go “hot” after being installed on the moon. Even for such reactor designs, the uranium needed is already part of the payload, and this material is radioactive, albeit at a low level. Many people, often unaware of radioactive uranium in their own granite countertops, have a deep-seated fear of anything radioactive inside a rocket, worried it might explode and spread the contamination across the environment. It is possible, therefore, that even “nearly safe” nuclear reactors launched from earth will experience significant public protest, resistance, Congressional pressure, and lawsuits. Another solution exists and is explored in this paper.

The US nuclear power development, starting with the Manhattan Project, had two primary purposes: electric power generation, and radioisotope generation for bombs made of uranium, plutonium, and hydrogen. Because of this dual focus, the enrichment of the U-235 fraction of uranium was the pathway used for nearly all applications. A modest effort in breeder reactors was made, which pursued the transmutation of thorium via the neutron flux from U-235 reactors to make U-233. This

lighter isotope of uranium is fissile, as is U-235 (most uranium is U-238, which is stable), and makes a suitable fuel, but less well-suited to bomb-making. Such work is all but extinct in 2019, and is almost forgotten, except by a few passionate advocates. The moon has very little uranium but amounts of thorium which are at or above typical abundances on earth’s crust - from which the moon is believed to have been formed. If this resource can be concentrated and transmuted, it will be possible to fuel nuclear reactors which can be launched completely free of radioactive material. Furthermore, the high-density nuclear fuel comes from local resources on the moon, helping to reduce launch mass of each such reactor.

Materials and Methods

Concentrating Thorium

Thorium is found across a large expanse of the moon’s Near Side with concentrations of 10-20 parts per million (ppm) [1]. Impact fracturing from meteoric bombardment has embedded or aggregated thorium dioxide (ThO2, or “thoria”) into other minerals, classified as agglutinates [2]. Thoria is an especially dense mineral with a specific gravity 10 times that of water. A straightforward concentration method is to comminute thorium-rich surface dust (average diameter 70 microns [3,4]) by grinding or milling to nanometer-sized particulates and then separate them in the lunar gravity using standard sorting techniques. Lunar soil, called regolith, includes free particles of iron-nickel metal left by impacts of stony iron type meteorites.

 Native alloys of these metals will have densities of approximately 8 and may not segregate effectively from thoria-rich agglutinates.Being magnetic, the iron-nickel fraction can be extracted by electromagnet, perhaps driven by electric current delivered by arrays of solar cells. This is a simple and low-energy method of concentrating thorium, likely to be used first.

To achieve greater purity and higher concentration of thorium another method is to exploit the exceptionally high melting point of thoria mineral, at around 3500 K. In addition to its value as a nuclear fuel, this refractory property of thoria has great value in other areas of lunar ISRU, including the extraction of oxygen and silicon from regolith [5,6]. At the extreme temperature needed to refine thoria, crucible materials are a challenge. The skull crucible method7 was developed to produce crystals of refractory zirconia and uses radio frequency (rf) inductive heating to melt the interior of a bolus or “gob” of mineral. The rf coils and the exterior of the bolus are cooled with a working fluid in communication with a radiative heat exchanger (convection is absent on the moon, and conduction through regolith is impractically slow), such that the interior of the charge is liquefied while the exterior remains solid. The gentle gravity of the moon (1/6 that of earth) will cause thoria to settle to the bottom of the melt. The supernatant magma is then poured off, perhaps into forms to create bricks for paving and building, and the remainder will be concentrated thoria. A fortuitous side benefit of the skull crucible method is the evolution of abundant amounts of oxygen, released from common lunar minerals such as quartz, olivine, anorthosite, pyroxene, and ilmenite [7-10]. The skull crucible method is obviously energy intensive, and is therefore a second generation thoria concentration method, used once the first U-233 fission reactor is operating on the moon.

Thorium Transmutation

Neutron bombardment of thorium (element 90, mass 232) results in its transmutation to protactinium (Pa, element 91). The extra neutron, being composed of a proton plus an electron, decays by electron emission (beta radiation) to leave behind an additional proton and thereby change the chemical identification of this isotope. The Pa-233 intermediate product has a half-life of 27 days and decays by beta radiation to become U-233. This isotope of uranium is fissile and suitable as a nuclear fuel.

Although space is filled with radiation, very little is neutrons. Outside of an atomic nucleus, wild neutrons have a half-life of 10.3 minutes, only slightly longer than the transit time of light from the sun to the earth’s orbit. Energetic solar flares produce neutrons in the sun’s corona, which, at relativistic speeds, have a retarded decay time relative to the moon, and can reach the surface. However, such neutrons fluxes are infrequent. Further, because the moon rotates relative to the sun with a synodic period of 27.3 days, only a few locations see the sun more than 50 percent of the time, and these are generally remote from thorium ore bodies. A more reliable source of neutrons for transmutation can be obtained by exposing beryllium (Be) to gamma rays. Gamma rays are abundant in space, making them a health risk for humans, and are generated by galactic cores, solar flares, supernovae, and even lightning on earth. There is a gamma ray background pervading the universe for which no source has been conclusively identified and is called the gamma ray “fog”. Gamma rays are more energetic than X-rays, with each photon having energies above 100,000 electron volts (eV). Data from the Fermi Gamma Ray Space Telescope indicates a flux of approximately 0.5 photons per second through each square centimeter of space [11]. When gamma rays impinge on beryllium metal, neutrons are generated [12]. A Be vessel containing Th and exposed to gamma rays will therefore transmute or “breed” U-233 fuel (Figure 1).

Gamma ray energies from space span seven orders of magnitude in eV, so some neutrons generated will be fast, and thus more likely to pass through without capture. Graphite acts as a neutron moderator to slow down fast neutrons to become thermal (slower) neutrons with a higher capture cross section by the thorium nucleus. To enhance neutron flux within the Th it is advantageous to use a neutron mirror material, which deflects wild neutrons back into the material to be transmuted. Beryllium is an excellent neutron mirror, as is graphite. Therefore, a vessel wall with exterior made of Be and interior made of graphite is a good design choice. The vessel must protrude proud from the lunar surface, ideally on a hilltop, and be sized to balance neutron capture probability with neutron flux intensity. Figure 1 illustrates one design configuration of a thorium transmutation vessel.

Fuel Considerations

Nuclear fission reactors often use pellets or spheres containing oxides of the fissile species. The U-233 urania derived from thoria will already be in the oxide form UO2. The enrichment of U-233 in the mineral charge of the transmutation vessel will depend on the concentration of thoria and the time of exposure. Once removed from the vessel, this fuel can be compressed into pellets using mechanical or hydraulic compression. Cylindrical pellets are loaded into fuel rods and inserted into the reactor core. If lunar-sourced U-233 fuel pellets are used, this allows for a nuclear reactor to be launched from earth having no radioactive materials in the payload manifest. Although the lunar surface is depleted of uranium relative to the earth’s crust, it is not negligible3. There may be some U-232 contamination of the thoria, and this complicates the thorium fuel cycle. The skull crucible method is one means for separation of thorium from uranium prior to transmutation, if required depending on system considerations. Chemical methods for Th-U separation have been developed as early as 1949 [13].

Thorium fuel cycle byproducts generally decay within a century, greatly reducing the well-known problems of disposing spent nuclear fuel. Some of these byproducts emit gamma rays. It may be possible to accelerate the breeding of U-233 using the hot waste, once the first fuel cycle of a lunar nuclear reactor is completed. The lunar surface is bombarded by radiation constantly: alpha, beta, gamma, energetic protons, and more. Relative to earth, which is protected by an atmosphere and a magnetosphere, humans on the moon must make protection from radiation second only to protection from the vacuum of outer space. It is a hostile environment and requires much shielding. A commonly envisioned method of radiation protection for humans is a layer of regolith some two meters thick. Applying this logic to spent fuel rods, the expedient of a shallow grave, with markers, signs, and beacons, should be sufficient to prevent harm to humans for a hot century [14-16].

Results

The thorium atom has a radius of 240 picometers, while oxygen is 60, so that thorium forms 2/3 of the area of the thoria molecule. Assuming that 50 percent of the impinging gamma rays produce a neutron from the Be outer casing, and assuming that 50 percent of these neutrons are absorbed by a thorium atom (including reflection within the vessel), the number of transmutations with 0.5 gamma ray particles arriving per second, per square cm, is 1.6E13. Assuming a critical mass of 15kg of nuclear fuel to start the reactor, and a time to fuel of three years, accounting for two Pa half-lives in this duration, a cylindrical transmutation vessel of 2 meters height requires an interior radius of 21cm.

One transmutation vessel holds 0.28 cubic meters of thoria. At 12 ppm concentration of thoria, each charge, sufficient for one nuclear reactor with a 30-year supply, requires considerable excavation and concentration operations. For a compacted regolith density of 2200 kg/cu.m this calls for 51,000 metric tons to be processed. Given the lighter gravity on the moon, this requires the same energy as processing 8,600 MT on earth. As a point of comparison, for a large, mature mining operation on earth, this much mass is moved every 20 minutes (Figure 2).

Discussion

The infrastructure needed to process lunar thorium into nuclear reactor fuel is non-trivial. First generation equipment includes: excavation equipment; ball mills; gravity sorters on a shaker table; electromagnet and solar panels; transmutation vessel; and a fuel pellet compaction device. Second generation equipment includes skull crucible apparatuses driven by rf generators, and a liquid cooling system with extensive radiative heat exchangers. Three years after the first transmutation vessel is filled, the first lunar nuclear reactor can be started up. Start-up generally requires an extra source of neutrons to initiate the fission chain reaction, but as can be seen above, these neutrons can be provided by a layer of beryllium exposed to cosmic rays. Once the first nuclear reactor is operational, second generation refining techniques can be brought online, greatly improving the throughput and purity of the thoria concentration operations. Assuming that mining equipment is operated by battery or fuel cell, the electric power from the nuclear reactor can significantly enhance the rate of ore excavation and concentration. A third generation becomes possible when the first reactor has its fuel rods removed, the gamma rays for which can increase the breeding rate of Th to U-233. It can be seen that the infrastructure investment has an accelerating payback in capability of lunar operations. These favorable economics are further augmented by the additional value which can be provided.

With more power to excavate, the mining operations can provide fuel pellets as an export commodity. Beachhead customers will be other settlements and mining operations on the moon, but also on Mars, and possibly at ore-rich asteroids. To reach these more distant destinations will require fast rockets. The obvious solution is a nuclear thermal rocket (NTR) which superheats hydrogen gas and passes it through a de Laval nozzle to generate thrust. The NTR is powered by U-233, and the hydrogen can be obtained by water ice mining in permanently shadowed regions of the moon. Extraction of water ice from ultra-cold craters can be facilitated by the warmth from spent fuel rods, and a nearby nuclear power station can provide the electrical current needed to electrolyze the water and produce hydrogen. If the NTR-powered spacecraft configure their hydrogen fuel tanks to surround the crew capsule the capture cross section for ionizing space radiation of the fuel significantly reduces exposure for the humans inside.

Conclusion

Shown here for the first time is a means for safely fueling nuclear reactors in space whereby no radioactive material is exposed to the risks of a rocket launch. Mining operations which are modest by earth standards, are needed to jump-start an expanding economy of ISRU capabilities which greatly multiply the power, speed, and safety of human operations in space. Nuclear reactors fueled by transmuted thorium native to the moon will drive extraction of hydrogen, oxygen, silicon, aluminum, titanium, and iron. Fast rocket ships powered by NTR open up the entire solar system to extraction of resources useful on earth, such as platinum-rich asteroids which can greatly reduce the cost of fuel cell systems on earth, making possible a hydrogen economy with no atmospheric carbon involved. Nuclear reactors burning U-233 are far safer than reactors currently in use on earth and produce generally short-lived byproducts which decay away in a century. The thorium fuel cycle is ill-suited to bomb makers, so the risks of nuclear war in space, using the technologies presented here, are far less than other means of space warfare. Rather, this new approach has the potential to expand the human economic sphere, open up new frontiers for science and industry, and to help improve life back home on earth.

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[cetaceous]

High Flux Isotope Reactor (HFIR) during a Fuel Change-out Oak Ridge National Laboratory, Oak Ridge, Tennessee image credit: Oak Ridge National Laboratory

[sciencespies]

Neutrons probe ultra-cold condensate for insight into quantum matter

https://sciencespies.com/physics/neutrons-probe-ultra-cold-condensate-for-insight-into-quantum-matter/

Neutrons probe ultra-cold condensate for insight into quantum matter

ORNL scientists Adam Aczel and Gabriele Sala stand beside the High Flux Isotope Reactor’s FIE-TAX instrument. Ross and her team used FIE-TAX to explore ytterbium silicate’s microstructure and find evidence for a BEC phase. Credit: ORNL/Genevieve Martin

Bose-Einstein condensates are macroscopic quantum phases of matter which appear only under very particular conditions. Learning more about these phases of matter could help researchers develop a better understanding of fundamental quantum behaviors and possibly contribute to future quantum technology.

That’s why Kate Ross and Ph.D. candidate Gavin Hester, researchers from Colorado State University, are at the Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL) to probe a material called ytterbium silicate. Ross believes ytterbium silicate, the only magnetic material based on a rare-earth element that shows evidence of a Bose-Einstein condensate, may hold the key to understanding quantum phenomena in other magnets based on rare-earth elements. By probing samples of ytterbium silicate with neutrons, Ross hopes to generate a detailed map of this unique Bose-Einstein condensate and then use that map to validate her hypothesis by identifying exotic quantum states in other magnetic materials. Ross and her collaborators discuss their findings in their paper published in the journal Physical Review Letters.

“If we can get a better understanding of the Bose-Einstein condensate we see in this material, then we could potentially use that knowledge to discover similar many-body quantum states in other magnetic materials based on rare-earth elements,” said Ross.

Ross explains that the Bose-Einstein condensate, also known as a BEC phase, is a quantum fluid in which particles stop behaving like individual entities and instead behave like waves moving in sync with one another across the fabric of a single, unified system. It’s unlike any solid, liquid, gas, or plasma and appears only at temperatures close to absolute zero, or 0 K (about -460°F). Scientists still have much to learn about this unique state of matter, but there is hope that its unique properties may one day contribute to advanced materials.

“There is no direct link between Bose-Einstein condensates and current proposals for quantum technology. But we also have a lot to learn about how this material behaves, and answering some of these fundamental questions about quantum phenomena will be the foundation for future scientific achievement,” said Hester.

For starters, it’s long been assumed that Bose-Einstein condensates can’t appear in magnetic materials based on rare-earth elements because those particular magnetic interactions didn’t seem to be isotropic enough for a BEC phase to appear. But, having observed evidence of a BEC phase in ytterbium silicate during past experiments, Ross and her team suspect this assumption could be false.

“We were really surprised when we saw the evidence for a BEC phase. It suggests that ytterbium is a much more versatile ingredient for forming many-body quantum states than we previously thought,” said Ross.

To better understand ytterbium silicate’s ability to host a BEC phase, Ross used the Cold Neutron Chopper Spectrometer instrument, or CNCS, at ORNL’s Spallation Neutron Source (SNS) and the Fixed-Incident Energy Triple-Axis Spectrometer, or FIE-TAX, at the High Flux Isotope Reactor (HFIR) to probe crystallized samples of ytterbium silicate. Complementary X-ray and neutron scattering measurements were performed at Argonne National Laboratory and the National Institute of Standards and Technology.

These experiments have been in the works for nearly 4 years. Ross’ research group first started growing samples of ytterbium silicate and mapping out the behavior of this material back in 2015. With their collaborators, they used various probes at Colorado State University and Sherbrooke University in Canada to get a first look at the material’s behavior, but they were eager to use neutron scattering to probe their samples.

“Neutrons are deeply penetrating, and as they pass through our samples they stir up these emergent quantum particles in such a way that we can accurately gauge exactly how those particles behave within ytterbium silicate’s microstructure,” said Hester.

To prepare their samples for neutron scattering, Ross and her collaborators had to cut and align every individual crystal so that each was oriented in the same direction. Furthermore, Ross had to both expose her ytterbium silicate samples to a magnetic field and use a special cooling chamber to bring them down to a chilly -459.28°F, which is colder than interstellar space and very close to absolute zero.

“Putting this experiment together took a lot of work, but the data we got was definitely worth the effort,” said Ross.

Ross and Hester hope that their work will not only shed light on how ytterbium silicate’s BEC phase is unique, but also give researchers a better understanding of quantum phenomena generally as they appear in other magnetic materials based on rare-earth elements.

“We’re definitely interested in learning more about this BEC phase in ytterbium silicate specifically, but we hope that what we learn here will also help our colleagues discover more quantum states in rare-earth–based materials. This fundamental understanding is essential for forming the material platforms of future quantum technologies,” said Ross.

Explore further

Studying quantum phenomena in magnetic systems to understand exotic states of matter

More information: Gavin Hester et al. Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb2Si2O7, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.027201

Provided by Oak Ridge National Laboratory

Citation: Neutrons probe ultra-cold condensate for insight into quantum matter (2019, December 2) retrieved 2 December 2019 from https://phys.org/news/2019-12-neutrons-probe-ultra-cold-condensate-insight.html

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#Physics

[neuronium]

Cold Fusion: Inside Tony Stark's Palladium ARC-Reactor 

Early generations of Iron Man armor were powered by the electromagnet device that Tony Stark built with the help of Ho Yinsen, using scraps of the Jericho Missile when he was attacked and captured by the Ten Rings.  Originally, Tony created the Palladium Mini-Arc Reactor to keep shrapnel from reaching his heart. He later used it to power his Mark I suit.

Tony’s palladium reactor does not appear to have any of the distinguishing features of a thermal reactor, such as cooling loops or turbines. As such, it must generate electricity directly without first generating heat, which makes sense, since a thermal reactor would likely burn Tony Stark's chest. Although it doesn’t address the heat problem like one proposed by Ryan Carlyle (Gizmodo), cold fusion offers an alternative scientific (hypothetical) mechanism on how the reactor works.

Cold fusion describes a form of energy generated when hydrogen interacts with various metals like nickel and palladium. Cold fusion is a field of condensed matter nuclear science (CMNS), and is also called low-energy nuclear reactions (LENR), lattice-assisted nuclear reactions (LANR), low energy nanoscale reactions (LENR), among others.

Cold fusion is also referred to as the Anomalous Heat Effect AHE, reflecting the fact that there is no definitive theory of the elusive reaction. It is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. This is compared with the "hot" fusion which takes place naturally within stars, under immense pressure and at temperatures of millions of degrees, and distinguished from muon-catalyzed fusion.

The Fleischmann-Pons Effect of Excess Heat When hydrogen, the main element of water, is introduced to a small piece of the metal nickel or palladium, a reaction occurs that can create excess heat and transmutation products. Excess heat means more heat comes out of the system than went in to the system. The excess heat can make hot water and useful steam to turn a turbine and produce electricity.

Cold fusion devices are typically small table-top laboratory experiments, ranging in size from tiny test-tubes to small refridgerator-sized generators. In spite of the relatively small size of the cells, the cold fusion reaction produces so much heat, it is more than can be accounted for by chemical means. and therefore must be some type of new nuclear mechanism, for cold fusion is not like today’s dirty and dangerous nuclear power.

No radioactive materials are used in cold fusion. LANR occurs as the tiny protons, neutrons and electrons of hydrogen interact, releasing energy slowly, through heat and photons, without the dangerous radiationassociated with conventional nuclear reactions, and cold fusion makes no radioactive waste

Here Is How Cold Fusion Reactor Works:

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A voltage is applied to two electrodes immersed in electrolytic solution of heavy water and lithium salts. This establishes the flow of current from the strip of palladium, acting as the cathode, to several platinum coils, acting as the anode. Temperature sensor measures the temperature of the electrolyte solution within the cell. As one of the cooling water that surrounds it, in the larger jacket container

Within the solution, many of the D2O heavy water molecules are dissociated into OD- and D+ ions. When the voltage is applied into the electrodes, the OD- ions are attracted to the positively charged platinum anodes, where they lose an electron and combine with the other OD ions to reform back into D2O, while the remaining Oxygen atoms combine to for O2 which escape as gas to the surface of the solution.

Meanwhile the D+ ions are attracted to the negatively charged palladium cathode where they quickly find an electron on the surface of the cathode to neutralize their charge. This cathode is made of palladium atoms arranged in a face centered cubic lattice. Some deuterium atoms whoop their way into the lattice by popping through inter-atomic sites within the lattice. Two deuterium atoms bump into each other along the surface of palladium cathode, and form a D2 molecule that is too big to enter the lattice. These D2 molecules clustered to form bubbles that rise up in the electrolyte solution. Simultaneously, new D2O molecules are dissociated in the electrolyte into more OD- and D+ ions. So, the process continues as long as the voltage is applied

However, when the SuperWave Principle is used to vary the current with a pattern of rising and falling nested oscillations, the loading of deuterium atoms within the palladium lattice is enhanced and so is the fluxing of deuterium atoms in and out of the cathode. As the concentration of deuterium in the lattice across the cathode's surface increases,  the deuteriums start to go their way deeper into the lattice, popping into neighboring inter-atomic sites. As the deuterium occupies more of these interiia sites, the lattice’s dimension increases a little. This lattice expansion causes mechanical stresses in the cathode, that impose resistance to deuterium diffusion, thus requiring higher current to force more deuterium atoms into the lattice until it reaches saturation.

When the concentration of deuterium within the lattice is high, they begin to move more collectively (not all at once but increasingly synchronized over time). At this point, phase of deuterium atoms begin to disappear, fusing together to form an atom of helium-4 isotope. Significant amount of heat is released in this fusion process. The energy released by each helium atom that appears 24 MeV is dissipated by the lattice as heat, rising the temperature of palladium electrode and the surrounding electrolytic solution

The amount of energy being generated by this fusion reaction is five million times greater than if those same two deuterium atoms were chemically combined to form a single D2 molecule and ten times larger than the oxidation reaction to create a D2O heavy water molecule. It is this excess heat that is causing such excitement within scientific community. 

The main reason scientists consider cold fusion unlikely is simple. Fusion involves the conversion of light elements to heavier elements, especially hydrogen to helium. This conversion isn't like turning, say, water or carbon dioxide into something else. Hydrogen and helium are elements—you cannot alter their nature under ordinary circumstances. And by ordinary circumstances, I mean hydrogen fusion in anything short of the conditions inside a star—millions of degrees in temperature, and unthinkably high pressure. Otherwise, two hydrogen atoms just can't be crushed together hard enough to fuse into one helium atom.

Cold fusion is also improbable (at least as an energy source) because it would produce loads of deadly radioactivity. Any scientists near enough to their instruments to get a good reading would almost certainly be fried by radiation. Indeed, one wag has suggested that if a scientist lived long enough to show up for the inevitable press conference announcing his results, that's almost ipso facto proof that, whatever interesting thing he might have done, he didn't induce nuclear fusion.

Source : Infinite Energy Magazine

[damiencordle]

I Found This Interesting. Joshua Damien Cordle

Cosmic rays may soon stymie quantum computing

The practicality of quantum computing hangs on the integrity of the quantum bit, or qubit.

Qubits, the logic elements of quantum computers, are coherent two-level systems that represent quantum information. Each qubit has the strange ability to be in a quantum superposition, carrying aspects of both states simultaneously, enabling a quantum version of parallel computation. Quantum computers, if they can be scaled to accommodate many qubits on one processor, could be dizzyingly faster, and able to handle far more complex problems, than today's conventional computers.

But that all depends on a qubit's integrity, or how long it can operate before its superposition and the quantum information are lost -- a process called decoherence, which ultimately limits the computer run-time. Superconducting qubits -- a leading qubit modality today -- have achieved exponential improvement in this key metric, from less than one nanosecond in 1999 to around 200 microseconds today for the best-performing devices.

But researchers at MIT, MIT Lincoln Laboratory, and Pacific Northwest National Laboratory (PNNL) have found that a qubit's performance will soon hit a wall. In a paper published in Nature, the team reports that the low-level, otherwise harmless background radiation that is emitted by trace elements in concrete walls and incoming cosmic rays are enough to cause decoherence in qubits. They found that this effect, if left unmitigated, will limit the performance of qubits to just a few milliseconds.

Given the rate at which scientists have been improving qubits, they may hit this radiation-induced wall in just a few years. To overcome this barrier, scientists will have to find ways to shield qubits -- and any practical quantum computers -- from low-level radiation, perhaps by building the computers underground or designing qubits that are tolerant to radiation's effects.

"These decoherence mechanisms are like an onion, and we've been peeling back the layers for past 20 years, but there's another layer that left unabated is going to limit us in a couple years, which is environmental radiation," says William Oliver, associate professor of electrical engineering and computer science and Lincoln Laboratory Fellow at MIT. "This is an exciting result, because it motivates us to think of other ways to design qubits to get around this problem."

The paper's lead author is Antti Vepsäläinen, a postdoc in MIT's Research Laboratory of Electronics.

"It is fascinating how sensitive superconducting qubits are to the weak radiation. Understanding these effects in our devices can also be helpful in other applications such as superconducting sensors used in astronomy," Vepsäläinen says.

Co-authors at MIT include Amir Karamlou, Akshunna Dogra, Francisca Vasconcelos, Simon Gustavsson, and physics professor Joseph Formaggio, along with David Kim, Alexander Melville, Bethany Niedzielski, and Jonilyn Yoder at Lincoln Laboratory, and John Orrell, Ben Loer, and Brent VanDevender of PNNL.

A cosmic effect

Superconducting qubits are electrical circuits made from superconducting materials. They comprise multitudes of paired electrons, known as Cooper pairs, that flow through the circuit without resistance and work together to maintain the qubit's tenuous superposition state. If the circuit is heated or otherwise disrupted, electron pairs can split up into "quasiparticles," causing decoherence in the qubit that limits its operation.

There are many sources of decoherence that could destabilize a qubit, such as fluctuating magnetic and electric fields, thermal energy, and even interference between qubits.

Scientists have long suspected that very low levels of radiation may have a similar destabilizing effect in qubits.

"I the last five years, the quality of superconducting qubits has become much better, and now we're within a factor of 10 of where the effects of radiation are going to matter," adds Kim, a technical staff member at MIT Lincoln Laboratotry.

So Oliver and Formaggio teamed up to see how they might nail down the effect of low-level environmental radiation on qubits. As a neutrino physicist, Formaggio has expertise in designing experiments that shield against the smallest sources of radiation, to be able to see neutrinos and other hard-to-detect particles.

"Calibration is key"

The team, working with collaborators at Lincoln Laboratory and PNNL, first had to design an experiment to calibrate the impact of known levels of radiation on superconducting qubit performance. To do this, they needed a known radioactive source -- one which became less radioactive slowly enough to assess the impact at essentially constant radiation levels, yet quickly enough to assess a range of radiation levels within a few weeks, down to the level of background radiation.

The group chose to irradiate a foil of high purity copper. When exposed to a high flux of neutrons, copper produces copious amounts of copper-64, an unstable isotope with exactly the desired properties.

"Copper just absorbs neutrons like a sponge," says Formaggio, who worked with operators at MIT's Nuclear Reactor Laboratory to irradiate two small disks of copper for several minutes. They then placed one of the disks next to the superconducting qubits in a dilution refrigerator in Oliver's lab on campus. At temperatures about 200 times colder than outer space, they measured the impact of the copper's radioactivity on qubits' coherence while the radioactivity decreased -- down toward environmental background levels.

The radioactivity of the second disk was measured at room temperature as a gauge for the levels hitting the qubit. Through these measurements and related simulations, the team understood the relation between radiation levels and qubit performance, one that could be used to infer the effect of naturally occurring environmental radiation. Based on these measurements, the qubit coherence time would be limited to about 4 milliseconds.

"Not game over"

The team then removed the radioactive source and proceeded to demonstrate that shielding the qubits from the environmental radiation improves the coherence time. To do this, the researchers built a 2-ton wall of lead bricks that could be raised and lowered on a scissor lift, to either shield or expose the refrigerator to surrounding radiation.

"We built a little castle around this fridge," Oliver says.

Every 10 minutes, and over several weeks, students in Oliver's lab alternated pushing a button to either lift or lower the wall, as a detector measured the qubits' integrity, or "relaxation rate," a measure of how the environmental radiation impacts the qubit, with and without the shield. By comparing the two results, they effectively extracted the impact attributed to environmental radiation, confirming the 4 millisecond prediction and demonstrating that shielding improved qubit performance.

"Cosmic ray radiation is hard to get rid of," Formaggio says. "It's very penetrating, and goes right through everything like a jet stream. If you go underground, that gets less and less. It's probably not necessary to build quantum computers deep underground, like neutrino experiments, but maybe deep basement facilities could probably get qubits operating at improved levels."

Going underground isn't the only option, and Oliver has ideas for how to design quantum computing devices that still work in the face of background radiation.

"If we want to build an industry, we'd likely prefer to mitigate the effects of radiation above ground," Oliver says. "We can think about designing qubits in a way that makes them 'rad-hard,' and less sensitive to quasiparticles, or design traps for quasiparticles so that even if they're constantly being generated by radiation, they can flow away from the qubit. So it's definitely not game-over, it's just the next layer of the onion we need to address."

This research was funded, in part, by the U.S. Department of Energy Office of Nuclear Physics, the U.S. Army Research Office, the U.S. Department of Defense, and the U.S. National Science Foundation.

Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu. Note: Content may be edited for style and length.

Journal Reference:

Antti P. Vepsäläinen, Amir H. Karamlou, John L. Orrell, Akshunna S. Dogra, Ben Loer, Francisca Vasconcelos, David K. Kim, Alexander J. Melville, Bethany M. Niedzielski, Jonilyn L. Yoder, Simon Gustavsson, Joseph A. Formaggio, Brent A. VanDevender, William D. Oliver. Impact of ionizing radiation on superconducting qubit coherence. Nature, 2020; 584 (7822): 551 DOI: 10.1038/s41586-020-2619-8