The OPAL neutron reflector “leak”.

Australian Greens senator Scott Ludlam has again this week called for Australia’s 20 MW OPAL research reactor to be closed down, following reports that a minor problem with the neutron reflector in this “tank-in-pool” reactor has yet to be rectified.

The facility has been out of operation for 11 of the past 14 months, during which time Australia has had to rely on costly imports of medical and scientific radionuclides from foreign suppliers in South Africa and Canada.

(Thanks to ANSTO for these images. Click through for large high-resolution images.)

The OPAL reactor core sits in the centre of a heavy water neutron reflector, which itself sits within the reactor’s large pool of light water, as we see in the above diagram.

In the centre of the circular heavy water vessel is the nuclear fuel itself, an array of 16 fuel assemblies. The large and small holes that pass through the entire height of the reflector, into the reactor core, support the generation of products such as transmutation-doped silicon and medical and scientific radionuclides as well as supporting neutron irradiation experiments. Several different neutron beamlines are also installed into the reactor, set up for different neutron spectra, including a liquid deuterium moderated cold neutron source.

Here, the square reactor “core” is clearly visible in the centre of this photograph, illuminated strongly by its own Čerenkov radiation, with the round neutron reflector surrounding it, pierced by the aforementioned ports for the irradiation of samples, with the greater reactor pool, containing light water, surrounding that.

The purpose of the neutron reflector is to improve neutron economy in the reactor, and hence to increase the maximum neutron flux – neutron flux being a fundamentally important metric of the performance and usefulness of a research and isotope production reactor.

To maximise the neutron flux or neutron economy in the reactor, heavy water, being a good moderator, basically a material from which elastic scattering of neutrons readily occurs, is used to construct a neutron reflector, immediately surrounding the reactor.

You’ve got light water from the pool seeping into the heavy water neutron reflector that surrounds the reactor. So, the light water from the pool is “leaking” into the reactor components, in towards the reactor. The reflector vessel is kept at a lower pressure than the light water at ambient pressure in the reactor pool. Any leakage pathway at all will allow light water to seep into the reflector vessel, diluting the heavy water. This issue was first identified in December of 2006, following commissioning of the new reactor, and attempts have been made to address the problem during an extended shutdown, which have been somewhat, but not totally, successful.

The sole consequence of this is that it dilutes the expensive heavy water. Of course, some people, and some media reports, seem to persist in documenting such a “leak” as though it were luminous green radioactive goo tricking out into suburban Lucas Heights.

If the heavy water is diluted to any significant extent, the efficiency of the neutron reflector is diminished, and the neutron flux that is achieved under nominal operating conditions is diminished, making the reactor less efficient for neutron beam experiments, neutron irradiation or radionuclide production. There is absolutely nothing here of any health physics or safety significance, at all, period. This dilution of the heavy water in the reflector vessel has absolutely no significance with regards to safety of the facility.

The Greens have derided ANSTO’s comments on the nature of the fault as “spin” and link these technical concerns to some kind of supposed, imaginary potential for safety concerns in the future. Of course, Ludlam wouldn’t know what a neutron reflector was if it bit him, and he has a proven track record of carrying on fervently about issues of nuclear science and technology, whilst possessing an alarming lack of understanding of such science and technology; especially for a federal politician.

Once the heavy water in the vessel becomes diluted, the only way to un-dilute it is via the same methods of deuterium enrichment such as those originally used to make it – such as distillation, or the Girdler sulfide process. In the case of a high deuterium concentration, as in a tank of somewhat diluted heavy water, distillation is the best option. Apparently, ANSTO are planning to construct a small-scale heavy water re-distillation system for online re-enrichment of some of the heavy water passing through the reflector circulation loop. This will fully counteract the problem, and allow the use of the reactor with the fullest efficiency for research and isotope production.

Nuclear Australia has got more to add about this issue, and ANSTO’s response to media reports and the Greens’ misleading statements is to be found here.

Anyway, Senator Ludlam and the Greens are not just content with calling for the reactor to be shutdown until the heavy water dilution issue can be rectified or nullified, however – they are quite adamant in calling for the permanent shutdown of the reactor.

“We think the safest solution for this reactor is for it to be shut down and for the waste to be contained properly,” Greens senator Scott Ludlam said this week. Importing radionuclides from international suppliers such as in South Africa and Canada could continue, he said.

In addition to the production of medical radionuclides, the reactor is used to produce neutron-transmutation-doped silicon boules for microelectronics – a valuable commercial service marketed by ANSTO – as well as for the production of radiopharmaceuticals and scientific radiochemicals. The radionuclides, most of them employed in nuclear medicine, typically commonly produced with ANSTO’s reactor, are thus:

Samarium-153 – 1.93 days
Molybdenum-99 – 2.75 days
Indium-111 – 2.83 days
Iodine-131 – 8 days
Chromium-51 – 27.8 days
Iodine-125 – 59.4 days

Half-lives are as indicated. The short half-life of ¹⁵³Sm, the basis of the onocological radiopharmaceutical Quadramet, in particular means that importation of this radionuclide is difficult and impractical, and it is essentially unavailable in the absence of an operating isotope production reactor in Australia.

We’ve learned from painful experience that the supply of expensive imported radionuclides has been subject to delays or interruptions to supply during shutdowns of OPAL (and HIFAR) in the past. On the basis of ANSTO’s past experience, it can reasonably be assumed that still worse problems would arise if Australia were to be totally reliant upon imported radionuclides. The supply problems arise from a range of causes, such as weather delaying flights, aviation regulations relating to radioisotopes being carried with other goods, or opposition from freight pilots.

The International Atomic Energy Agency has identified the “growing problem of refusal by carriers, ports and handling facilities to transport radioactive material” as a significant problem for nuclear medicine and scientific research involving radionuclide importation across the world, and has initiated processes intended to identify ways in which it can be overcome. A number of international, such as British Airways, no longer accept carriage of radioactive material, and others have imposed tight restrictions. Unless a way can be found to reverse such trends, shipments of radionuclides across the world will become increasingly problematic.

The reactor and its associated neutron guides and instruments are used for neutron radiography, neutron scattering imaging, neutron reflectometry and other advanced neutron-beam based research and technological applications, neutron activation analysis, for example for forensic applications, as well as the analysis and testing of materials under neutron irradiation and research into the potential for Boron Neutron Capture Therapy as a potent weapon against cancer – which requires the patient to be bought to a nuclear reactor to produce the thermal neutron flux required.

Even if some radionuclides can be imported, clearly our research reactors in Australia are of significant importance and usefulness in such fields. If radionuclides are to be imported from foreign suppliers, they are still being produced in similar nuclear reactors – if a research reactor is such a dangerous thing, as is suggested by these groups, why should foreign nations be subjected to such a burden for the production of radiopharmaceuticals which are for the benefit of us? Why shouldn’t we take responsibility for our own reactor, if we have decided that we value the benefits of its products, and we’re not prepared to forgo them?

The Green Glass Sea

The Green Glass Sea sounds like a nice little story. It’s only a book pitched at teenagers/children, but it sounds like a cute book, telling a famous story in an interesting way. I’ll have to see if I can get my hands on a copy.

Researchers develop filter for nuclear waste

Apologies for the thread title, we have this essentially inevitable problem where newspaper headlines aren’t always the best description of science and technology.

http://www.theaustralian.news.com.au/story/0,25197,24370728-2702,00.html

Australian researchers say they have created a low-cost material to filter and safely store nuclear waste. The potential breakthrough for the environment was made by a team of scientists from Queensland University of Technology, led by Associate Professor Zhu Huai Yong from the School of Physical and Chemical Sciences.

(Tip to NEI Nuclear Notes for finding the story.)

Prof Zhu said the discovery was particularly important as the world increased its reliance on nuclear energy.

“You have to keep nuclear waste somewhere for hundreds of years,” Dr Zhu said.

“Water is used to cool nuclear reactors and during the mining and purification of nuclear material, so waste water is a big problem.

“For example, there is a lake in the United States filled with millions of gallons of nuclear waste water.”

But if the waste was stored conventionally in lakes or steel containers, there was a danger it could leak and pollute the land around it.

Well, I’m not so sure about what he’s talking about here. I seriously hope they’re not talking about water used at nuclear generating stations as “nuclear waste”, for example – clearly Lake Anna in Virginia, for example, does not contain millions of gallons of “nuclear waste”, or anything of any radiological significance at all, for that matter.

Alternatively, perhaps they’re talking about “tailings” waste from uranium mining and extraction? I’m not sure, but in any case, I’m not particularly concerned about waste from uranium mining and extraction, since it contains naturally occurring radionuclides such as radium which occur naturally in the ground, in exactly the same amounts that they’re naturally present in the earth, which can be put right back into the earth.

Professor Zhu said the QUT team had discovered how to create nanofibres, which are millionths of a millimetre in size and can permanently lock away radioactive ions by displacing the existing sodium ions in the fibre.

“We have created ceramic nanofibres which attract and trap radioactive cations (positively charged ions), possibly forever,” he said.

“The ceramic material can last a very long time, much longer than the radioactivity of a radioactive ion.”

Ceramic was also more chemically stable than metal, could last much longer and was much cheaper to make than steel.

The ceramic nanofibres were made from titanium dioxide, a mineral found abundantly in Australia and used to colour white paint.

The fibres were mixed with caustic soda and heated in a laboratory oven to make the ceramic material.

The nanofibres, which are up to 40 micrometres in length, look like white powder to the human eye, Prof Zhu said.

“The fibres are in very thin layers, less than one nanometre in width, and the radioactive ions are attracted into the space between the layers,” he said.

“Once the ceramic material absorbs a certain amount, the layers collapse to lock the radioactive ions inside.”

It sounds like they’ve created an artificial ceramic nanomaterial based on the well-studied chemistry of perovskite materials, in this case saturated with Na⁺ ions, forming something like Na₂Ti₃O₇ or Na₂TiO₃, perhaps.

Perovskite materials can contain all kinds of different anions – positively charged ions, usually metals – bound up inside their crystal structure. Strontium titanate and barium titanate are both well-studied materials with interesting properties. Strontium titanate is a common chemical form in which radioactive ⁹⁰Sr is used when it’s packaged in sealed radioactive sources, such as the very large ⁹⁰Sr sources that form the basis of ⁹⁰Sr radioisotope thermoelectric generators, because it’s essentially a completely inert, insoluble solid ceramic material from which the radionuclide cannot leach, dissolve or otherwise escape.

These perovskite-type materials, and their ability to “lock up” essentially any alkali metal or alkaline earth metal, as well as transition metals, actinides and just about any metal, really, inside their crystal structure is well studied technology with regards to the disposal of radioactive waste and radioactive byproduct material, both fission products and plutonium-contaminated defence wastes, and indeed, these materials are the fundamental basis of the use of Synroc type materials for radioactive waste immobilisation.

Now, it’s difficult to speculate, based on nothing more than a newspaper report, but I’m guessing that where such a perovskite material is turned into a nanomaterial, with nanoscale structure, and loaded with sodium ions, you end up with something that is kind of like an interesting inorganic ion-exchange material. (Ion-exchange materials are of course an important part of nuclear chemistry, both for recovering and recycling nuclear materials, and decontaminating waste materials.)

If you take some waste water that is contaminated somehow, say, with nuclear fission products like ⁹⁰Sr or ¹³⁷Cs, (and providing it’s not economical to recover such materials for useful purposes), I suppose you can simply run it through a bed of this material, and those ions (Sr²⁺ and Cs⁺, assuming that they’re in soluble forms) become permanently substituted into the perovskite. Then, this material can be sintered, and you have the radionuclide contamination converted straight into a chemically inert, insoluble ceramic. Unlike an ion-exchange material, however, once those cations are in the material, the idea is that they will be permanently retained there.

To paraphrase Bernard Cohen, you can take this material, if you want to dispose of it, turn it into a rock, then take the rock and put it in the rock’s natural habitat, deep inside the earth.

Nuclear fuel recycling in the United States

Earlier this month an editorial was posted on GreenvilleOnline.com titled Nuclear reprocessing is risky and impractical, laying out the case against recycling of nuclear fuels (or at least the case against conventional methods for recycling of conventional nuclear fuels). (Thanks to Atomic Insights for the story tip.)

The editorial states:

Nuclear reprocessing separates plutonium from radioactive waste so that it can be reused to generate additional energy. However, reprocessing also has an unfortunate side effect: It dramatically increases the volume of radioactive waste.

Of course, if the alternative to nuclear fuel recycling is to take all the used fuel and label it as supposed “waste” material, and of course that is the alternative, then it’s a universally accepted fact that of course recycling of the nuclear fuel reduces the volume of material that is considered “waste”.

Typical used fuel from a typical LWR with a LEU fuel consists of approximately 96% uranium-238 and 235, which is completely unchanged in the reactor from the original fuel, about 3% of fission product nuclides, about 1% of plutonium, about half of which is plutonium-239 and half of which is comprised of other plutonium nuclides, and small trace quantities of other actinides, including a little U-236, U-232, Np-237, Am-241 and what have you.

Even if nuclear reprocessing involves only taking the uranium from that nuclear fuel, then immediately, with uranium separation alone, you’ve removed 96% of the mass of the radioactive “waste” that you need to deal with – and that’s without any consideration of the valuable, useful materials which constitute the other four percent.

If “nuclear waste” is such a terrible concern, the the first thing that should be done is to make sure we’re not wasting it.

The separation of plutonium is not necessary in any way for the use of nuclear energy, nor is it required at any point for the efficient recycling of used uranium fuels. The separation of plutonium, contrary to popular belief, is not the point of nuclear recycling. Separation of plutonium is an integral part of nuclear weapon building, and it is certain technologies which were developed for this latter purpose which have, historically, been applied to the recycling of power reactors fuels.

To construct a nuclear fission weapon from plutonium does indeed require the chemical separation of pure plutonium from uranium irradiated within a nuclear reactor – but that’s the only thing that requires separation of plutonium. This is why separation of plutonium, or the possibility of it, seems to be viewed with distrust and suspicion, especially at the Savannah River Site, perhaps, given its historical mission of the production of weaponisable plutonium via nuclear reactors and PUREX extraction.

Even if you want to use plutonium from used civilian reactor fuel efficiently, and recycle it back into the recycled nuclear fuel, where it serves as a potent, valuable energy source, chemical separation of plutonium is not needed. Even though most established, mature efforts for the recycling of nuclear fuels at the industrial scale involve the PUREX process, which was designed and established specifically to support the production of separated plutonium for nuclear weapons, there is no reason why this process is essential at all. It’s quite straightforward to modify the chemistry of the solvent extraction process so that the plutonium is kept combined with the other actinides, so that this material can be recycled into new nuclear fuel without any material being produced that presents any proliferation risk. That is what is done with the COEX or DIAMEX chemical processes, and what can be done even better via pyroprocessing or in-situ separation of nuclear poisons in a molten salt reactor.

Even if the potential for diversion and weaponisable plutonium was considered so grave that we were insistent of taking the plutonium and disposing of it in some kind of deep geological repository, this would only constitute 1% of the fuel – so, we wouldn’t be losing much of the fuel, really. However, plutonium-239 is a moderately long lived nuclide – with a half-life of 24,400 years, it doesn’t just go away overnight if put in a geological repository. So, in decades to come, the material could still be removed, and weaponised.

The only proper way to get rid of plutonium, if you’re really concerned about nuclear weapons proliferation, is to fission it in a nuclear reactor – and, lo and behold, you get plenty of clean, safe energy to boot, at the same time.

According to the Union of Concerned Scientists, “After reprocessing … the total volume of nuclear waste will have been increased by a factor of twenty or more ….”

Of course, that’s simply absurd. What sort of definition of reprocessing are they using? What evidence is provided for such a claim?

For instance, discharges of iodine-129, a very long-lived carcinogen, have contaminated the shores of Denmark and Norway at levels 1,000 times higher than nuclear weapons fallout.

Well, does that tell us anything? What is the background dose rate to the public as a result of the nuclear weapons fallout, and what is the contribution added to the dose rate to the public as a result of nuclear fuel reprocessing?

Health studies indicate that significant excess childhood cancers have occurred near French and English reprocessing plants.

Is there any peer-reviewed, scientifically motivated, literature which demonstrates the existence of such excess childhood cancers, and demonstrates, or even reasonably motivates, a causal connection between the two?

In 2003, for example, researchers from Harvard’s Kennedy School of Government said that reprocessing costs more than twice as much as safe, on-site interim storage of nuclear waste.

The report cited, from the Belfer Center for Science & International Affairs at Harvard University, The Economics of Reprocessing vs. Direct Disposal of Spent Nuclear Fuel, states:

At a uranium price of $40/kgU (comparable to current prices), reprocessing and recycling at a reprocessing price of $1000/kgHM would increase the cost of nuclear electricity by 1.3 mills/kWh. Since the total back-end cost for the direct disposal is in the range of 1.5 mills/kgWh, this represents more than an 80% increase in the costs attributable to spent fuel management (after taking account of appropriate credits or charges for recovered plutonium and uranium from reprocessing).

Furthermore, the editorial’s authors continue with much the same assertion:

In 2007, the National Academies of Science (NAS) noted that no reprocessing technology currently on the table “is at a stage of reliability and understanding that would justify commercial-scale construction” and the report therefore concluded “there is no economic justification for going forward with this program at anything approaching a commercial scale.”

The nuclear industry has reached a similar conclusion. A 2007 report by the Keystone Center, underwritten by various utility companies, said “reprocessing of spent fuel will not be cost-effective in the foreseeable future.”

The “reprocessing is not economically competitive” argument basically boils down to the idea that recycling the used fuel is more expensive than the inefficient, once-through use of newly mined uranium.

People are frequently concerned about the environmental intensiveness of uranium mining and the handling of radioactive wastes from nuclear power – and yet recycling and efficient re-use of nuclear fuels minimise the requirement for both of these things. To me, the argument against recycling because recycling costs more is ridiculous, and it’s essentially equivalent to eschewing the use of alternative energy systems in favor of more coal, because coal is cheaper.

What really goes on at the Large Hadron Collider – Part 2: or, How I Learned to Stop Worrying and Love the Black Hole

No, black holes produced in the Large Hadron Collider (LHC) aren’t going to kill you, eat Geneva, or destroy the Earth. If those black holes are formed, it will be really quite fantastic, and it will represent everything that we’ve hoped for from LHC and more.

I’ll take a couple of hours from my Saturday afternoon to write this, and hopefully it will reduce, even if just infinitesimally, the number of stupid conversations I have to listen to where people’s entire knowledge of particle physics comes from the Herald Sun. I consider that a worthwhile investment of my time, and if it means that I don’t have to hear about teenage girls tragically taking their own lives for absolutely no reason at all because of such nonsense, then I feel that that’s a really good thing, too.

If the centre-of-mass energy of two colliding elementary particles (a maximum of 14 TeV for collisions in the Large Hadron Collider) reaches the Planck scale, , and their impact parameter, , is smaller than the corresponding Schwarzschild radius, , then a black hole will indeed be produced. However, the energy corresponding to the Planck scale, , is a lot of energy, if you’re an experimental physicist. Such energies are entirely outside the reach of the experimental physicist – so, surely, generation of microscopic black holes (hereafter, ) at the Large Hadron Collider (LHC) has got to be impossible – doesn’t it?

According to the Standard Model of Particle Physics, generation in a particle collider is indeed impossible at the TeV-scale energies associated with the current generation of high energy experimental particle physics endeavors, such as the LHC. The much-publicised speculations regarding the possibility of formation at the LHC are based on speculative hypotheses derived from theoretical models of cosmology and particle physics beyond the standard model (“new physics”).

Certain models put forward some years ago by theoretical physicists offer a seemingly neat and efficient lead into answering the questions, such as those of the hierarchy problem, of interest to particle physicists, and involve the existence of higher spatial dimensions.

The novelty of these higher-dimensional models lie in the fact that it is no longer necessary to assume that these dimensions are of sizes close to the Planck length (). Rather, large extra dimensions could be as large as around a millimetre, if we suppose that the `fields of matter’ – those fields of relevance to electroweak interactions and QCD, for example – `live’ in the 3+1 dimensional hypersurface of our 3-brane – our familiar 3+1 dimensional world – and that only the gravitational field can interact across the higher-dimensional universe. Experiments involving the direct measurement of Newtonian gravity put upper bounds on the size of extra dimensions to a value of less than a few hundred microns. Under such an approach, the traditional Planck scale, corresponding to , is no more than an effective scale and the real fundamental Planck scale in dimensions is given by , where is the volume associated with the extra dimensions. In 10 dimensions, with radii associated with the extra dimensions of the Fermi scale, we find .

OK, now, if you’re thinking that that all sounds horribly complicated, I understand. I don’t understand it all, either. Allow me to try and re-explain that.

Imagine two particles being smashed together within the collider. As they come together, their gravitational interaction increases according to the familiar inverse square law of classical gravitational physics. The formation of a black hole, at least the astrophysical ones with which we’re familiar, is a phenomenon which is all about gravity. For the force of gravity to become strong enough to create a black hole in our proton-proton system, these protons would have to be bought together inside a distance on the scale of the Planck length – . The energy corresponding to such a distance scale is – an energy that dwarfs the most energetic cosmic rays known – which themselves dwarf the proudest achievements of Earthly accelerator physicists.

But this all assumes that the gravitational force exists only within the familiar world of three dimensions. If gravity extends across the higher spatial dimensions, the force of gravitational interactions increases much more rapidly with increasing proximity of the particles, and at very small length scales associated with high energy experimental particle physics, it’s just barely possible that such phenomena can start to become relevant.

So suppose when the particles interact with these very high energies, they’re interacting on the scale of the higher-dimensional world. As gravity “becomes strong”, black hole formation could start to become relevant on a length scale on the order of . That is still an inconceivable scale compared to everyday experience, but it is a factor of ten thousand trillion times closer to our reach than the Planck scale in a three-dimensional universe. And this length scale corresponds to energies on the order of only a couple of teraelectron volts. It is these TeV-scale energies that are well within the grasp of the LHC.

NB: For an extremely readable introduction to these possibly daunting concepts of theoretical particle physics and cosmology, which is fully accessible to all readers, with no prior knowledge of advanced physics required, Lisa Randall’s Warped Passages is suggested reading.

If such models are have any meaning, it is effectively a natural choice (and not an arbitrary one based on phenomenological motivations) because it essentially presents a resolution to the heirarchy problem. [1]

If the signature of the decay of a microscopic black hole is observed within the LHC’s detectors, then on that day, these fascinating models are no longer theoretical physics – they represent our best empirically-motivated description of what nature is.

If the Planck scale is thus accessible down into the TeV range, then -generation in TeV-scale particle collider experiments is indeed possible. It could be, maybe. The 14 TeV centre-of-mass energy of the LHC could allow it to become a black hole factory with a production rate as high as perhaps about .

Many studies are underway to make a precise evaluation of the cross-section for the creation of black holes via parton collisions, but it appears that the naive geometric approximation, , is quite reasonable for setting the orders of
magnitude. [1]

The possibility of the presence of large extra dimensions would be doubly favourable for the production of black holes. The key point is that it allows the Planck scale to be reduced to accessible values, but additionally, it also allows the Schwarzschild radius to be significantly increased, thus making the condition for black hole formation distinctly easier to satisfy.

One notable property of any microscopic black holes that could result from LHC collisions is that these black holes will have radii corresponding to the TeV scale – – much smaller than the size of the large extra dimensions. Hence, any can be considered as totally immersed in a D-dimensional space (which has, to a good approximation, a time dimension and large (non-compact) spatial dimensions.) It follows that such a does indeed rapidly `evaporate’ into fundamental particles, with an extremely short lifetime, on the order of . [1] This argument is exclusively based on the same theoretical physics that predicts the possibility of microscopic black hole formation at TeV-scale energies, and is completely independent of the oft-cited argument regarding Hawking radiation.

The temperature of the , typically about 100 GeV under such conditions, is much lower than it would be for a black hole of the same mass in a four-dimensional space, but nevertheless, the black hole retains the expected characteristic quasithermal radiation spectrum corresponding to its temperature.

In the case of the hypothetical microscopic black holes, if they can be produced in the collisions of elementary particles, they must also be able to decay back into elementary particles. Theoretically, it is expected that microscopic black holes would indeed decay via Hawking radiation, a mechanism based on fundamental physical principles, for which there is general consensus as to the validity.

It is well established in the literature that there is no way that a produced at the LHC could possibly be able to accrete matter in a potentially Earth-destroying fashion, even if, somehow, it turned out that such a black hole could be particularly stable. [3] [4] If the physical models that provide a basis for considering the possibility of formation in TeV-scale particle collisions are indeed valid, then microscopic black holes could be produced not only by our particle collider experiments, but also in high energy cosmic ray interactions, and those black holes would have stopped in the Earth or in other astronomical bodies. The stability of these astronomical bodies demonstrates that such black holes, if they exist, cannot possibly present any credible danger of planetary destruction.

Familiar astrophysical black holes have very large masses, ranging from several solar masses to perhaps as high as a billion solar masses for the largest supermassive black holes. On the other hand, the maximum centre-of-mass energy of collisions in the LHC corresponds to an equivalent mass of the order of solar masses. If a microscopic black hole is produced in the LHC, it will have a mass far, far, far smaller than any black hole with which astrophysicists may be familiar, and possibly markedly different characteristics as well.

The rate at which any stopped black hole would accrete the matter surrounding it and grow in mass is dependent on how it is modeled. Several scenarios for hypothetical matter accretion into a terrestrial black hole have been studied and reported in the literature, where well-founded macroscopic physics has been used to establish conservative or worst-case-scenario limits to the rate of accretion of matter into a terrestrial black hole.

In the extra-dimensional scenarios that motivate the possibility of formation at TeV-scale energies (but which also motivate the extreme instability of those black holes), the rate at which the would accrete matter would be so slow, in a ten-dimensional universe, that the Earth would survive for billions of years before any harm befell it – a limiting time scale for Earth’s survival which is comparable to that already set by the finite main-sequence lifetime of the Sun.

At the intersection of astrophysics and particle physics, cosmology and field theory, quantum mechanics and general relativity, the possibility of -production in particle collider experiments such as the LHC opens up new fields of investigation and could constitute an invaluable pathway towards the joint study of gravitation and high-energy physics. Their possible absence already provides much information about the early universe; their detection would constitute a major advance. The potential existence of extra dimensions opens up new avenues for the production of black holes in colliders, which would become, de facto, even more fascinating tools for penetrating the mysteries of the fundamental structure of nature. [1]

The production of microscopic black holes at the LHC is just barely possible, perhaps. These microscopic black holes do not represent some kind of doomsday scenario for the Earth – quite the opposite, in fact.
They represent, arguably, some of the most incredible insights into exciting new physics that we could wish to take away from the LHC, with profoundly interesting implications for the future of physics.

There have also been suggestions over the years that there may exist magnetic monopoles, particles with non-zero free “magnetic charge”. As was originally established by Dirac, any free magnetic charge on a monopole will be quantised, as is electric charge, and necessarily much larger in magnitude than the elementary quantum of electric charge. For this reason, past efforts to look for evidence of a magnetic monopole have looked for strongly ionising particles with quantised magnetic charge.

In some grand unified theories, though not in the Standard Model of particle physics, magnetic monopoles are predicted to possibly be able to catalyse the decay of the protons comprising ordinary baryonic matter, into leptons and unstable mesons. If this is the case, successive collisions between a monopole and atomic nuclei could release substantial amounts of energy. Magnetic monopoles which may possess such properties are predicted to have masses as high as , [4] or higher, making them far too massive to be produced at the LHC.

The impact of such magnetic monopoles interacting with the Earth has been presented and quantitatively discussed in the literature [2], where it was concluded that the potential for a monopole to catalyse nucleon decay would allow the monopole to destroy nothing more than an infinitesmal, microscopic quantity of matter – nucleons – before exiting the Earth.

Independent of this conclusion, if magnetic monopoles could be created in collisions in the LHC, high-energy cosmic rays would already be creating numerous magnetic monopoles, with many of them striking the Earth and other astronomical bodies. Due to their large magnetic charges and strong ionising effect, any magnetic monopoles thusly generated would be rapidly stopped within the Earth.

The continued existence of the Earth and other astronomical bodies over billions of years of bombardment with ultra-high-energy cosmic rays demonstrates that any such magnetic monopoles can not catalyse proton decay at any appreciable rate. If particle collisions within the LHC could produce any dangerous magnetic monopoles, high-energy cosmic ray processes would already have done so. [3] [4]

As with the consideration of the possbility of the formation of black holes in TeV-scale particle collisions at LHC, the continued existence of the Earth and other astronomical bodies such as the Sun demonstrate that any magnetic monopoles produced by high-energy processes – be they in a particle collider or in a high-energy cosmic ray interaction – must be harmless.

As with the case of black hole production within the LHC, these arguments are not to say that such a process could not occur – only that such processes are not dangerous.

Whilst the existence of a magnetic monopole is viewed with the most extreme skepticism by the overwhelming majority of physicists, perhaps there is just the most remote possibility that it could be. The formation of a magnetic monopole at the LHC will not endanger the Earth, but if such a monopole was to be detected, we would of course find ourselves faced the prospect of re-writing two hundred years of physics.

As with the formation of a microscopic black hole, the formation of a magnetic monopole does not represent some kind of doomsday scenario – it represents one of the most incredible revelations we could possibly hope to find from experiments at the LHC.

References and suggested reading:

[1] Aurelien Barrau and Julien Grain
The case for mini black holes
CERN Courier, 2004.
http://cerncourier.com/cws/article/cern/29199.

[2]:
J P Blaizot, John Iliopoulos, J Madsen, Graham G Ross, Peter Sonderegger, and Hans J Specht.
Study of potentially dangerous events during heavy-ion collisions at the LHC: report of the LHC safety study group.
CERN, Geneva, 2003.

[3]:
Savas Dimopoulos and Greg L. Landsberg.
Black holes at the LHC.
Phys. Rev. Lett., 87:161602, 2001.

[4]:
John Ellis, Gian Giudice, Michelangelo Mangano, Igor Tkachev, and Urs Wiedemann (LHC Safety Assessment Group).
Review of the safety of LHC collisions
Journal of Physics G: Nuclear and Particle Physics, 35(11):115004 (18pp), 2008.

The nuclear industry’s biggest challenge: PR

This is the New Statesman’s special supplement on energy issues from last year. It’s worthwhile reading.

Now, I know, it’s unfortunate that I missed this, and I’m now about a year late to the table, but this is a really good piece, it’s worth reading. As well as a great piece of the need for improved PR and public education about nuclear power, which was the main bit I was interested in at first, there are interesting pieces on wind energy, the geopolitics of natural gas supplies in Europe, battery technology, and a great piece by physicist Brian Cox, suggesting that, since we do have access to ample sustainable energy, energy “conservation” as a long term goal is both immoral and dangerous.

What really goes on at the Large Hadron Collider?

What really goes on at the Large Hadron Collider?

What are the questions that it actually seeks to answer? I’ll begin by outlining these questions.

The Higgs mechanism: Can the Higgs boson be empirically detected? What if it doesn’t actually exist?

(A bit of trivia about the Higgs boson:
When Leon Lederman wrote The God Particle, and coined that phrase, which journalists love, and scientists hate, he originally wanted to call it the goddamn particle, but the publisher wouldn’t allow it.)

Even if a Higgs boson is not found, at the TeV-scale energies being probed here, there will be an extremely good chance of getting some insights into whatever process is responsible for things like electroweak symmetry breaking, if it’s not the Higgs mechanism.

The Hierarchy Problem: Why is gravity such a very weak force, compared to the other fundamental forces? Is the answer related to higher spatial dimensions, or to supersymmetry?

Higher dimensions: Can we empirically “see” evidence of higher spatial dimensions in the universe in high-energy particle interactions? What are those dimensions like? What are their properties?

CP-violation: How was CP-violation established in the primordial universe, to the degree that it was? What mechanism is responsible for the CP-violation, and the resultant amount of matter in the cosmos?

Dark matter: It’s quite well accepted today that there is indeed “dark matter”, and it is comprised of weakly-interacting particles that have a significant amount of mass. Exactly what are these particles? Could the lightest supersymmetric particles, such as the neutralino, if they exist, be consistent with the dark matter?

Black holes: If “micro black holes” really could be produced in LHC interactions, do they behave as predicted by Hawking, evaporating and radiating Hawking radiation?

Supersymmetry: If supersymmetric particles can be observed, what is the mechanism responsible for supersymmetry breaking, making the s-particles so massive, compared to the familiar standard model particles? Can the existence of supersymmetry explain the strength of gravity, or the composition of dark matter?

Every one of these areas is potentially going to be answered, or research is going to be considerably furthered, by work at the LHC.

An entire book (or many) could be written on each and every one of these things. For now, though, I’ll elaborate a little on just one of these areas of interest – CP-violation and its connection to cosmology.

One of the great open problems in physics at the moment is the question of why the Universe has so much matter in it, and essentially no antimatter.

If matter and antimatter (quarks and antiquarks, fundamentally) were created in equal amounts following the Big Bang, then all the matter and antimatter would annihilate, and the matter-filled Universe we see would not exist.

Something that we might expect, perhaps somewhat naively, from laws of physics is CP-symmetry – that is, that the laws of physics are ’symmetrical’ under CP-transformation (CP- as in a combination of both Charge and Parity operators.) In other words, basically, the laws of physics are “symmetrical” between matter and antimatter, since CP-symmetry is the symmetry between matter and antimatter. We might expect particles and antiparticles should behave “symmetrically” in every way.

However, as per the above, this isn’t true. At least, it’s not always true. There exists some mechanism whereby CP-symmetry is perturbed, just a tiny bit – it was perturbed just enough in the early universe to create the universe that we see. This is CP-violation, an example of a symmetry violation in physics.

The CP operator is the product of two: C for charge conjugation, which transforms a particle into its antiparticle, and P for parity, which creates the mirror image of a physical system. The strong interaction and electromagnetic interaction seem CP-invariant, but a slight degree of CP-violation is observed in weak interactions under certain conditions.

The greater the degree of CP-violation present in the early Universe, the greater the amount of matter left in the Universe. Thus, the understanding of CP-violation plays an important role in cosmology, in explaining the amount of matter in the universe, which is a rather important quantity, from the point of view of physical cosmology.

Quoteth Wikipedia a bit because I’m getting sick of writing and can’t remember exact dates and all the names:

Until 1956, parity conservation was believed to be one of the fundamental geometric conservation laws (along with conservation of energy and conservation of momentum). However, in 1956 a careful critical review of the existing experimental data by theoretical physicists Tsung-Dao Lee and Chen Ning Yang revealed that while parity conservation had been verified in decays by the strong or electromagnetic interactions, it was untested in the weak interaction. They proposed several possible direct experimental tests. The first test based on beta decay of Cobalt-60 nuclei was carried out in 1956 by a group led by Chien-Shiung Wu, and demonstrated conclusively that weak interactions violate the P symmetry or, as the analogy goes, some reactions did not occur as often as their mirror image.

Only a weaker version of the symmetry could be preserved by physical phenomena, which was CPT-symmetry. Besides C and P, there is a third operation, time reversal (T), which corresponds to reversal of motion. Invariance under time reversal implies that whenever a motion is allowed by the laws of physics, the reversed motion is also an allowed one. The combination of CPT is thought to constitute an exact symmetry of all types of fundamental interactions. Because of the CPT-symmetry, a violation of the CP-symmetry is equivalent to a violation of the T-symmetry. CP violation implied nonconservation of T, provided that the long-held CPT theorem was valid. In this theorem, regarded as one of the basic principles of quantum field theory, charge conjugation, parity, and time reversal are applied together.

From that last paragraph, of course, we arrive at the seemingly incredible conjecture, which is absolutely true, that an antiparticle is a corresponding particle… it’s just traveling backwards in time, as was explained perhaps most famously by Richard Feynman. That is indeed how Quantum Field Theory predicts the existence of antiparticles.

The (neutral K) meson (or kaon) consists of a down quark and a strange antiquark – – and its corresponding antiparticle is of course made up of a strange and an anti-down, .

Similarly, the is , and the is . (B mesons, by definition, contain a b quark/antiquark, which is why they’re named thus, and kaons contain a strange combined with a non-strange quark.)

These mesons can ‘oscillate’ back and forth – with a particle spontaneously turning into the antiparticle, and vice versa, as shown in this Feynman diagram.

But the transition between particle and antiparticle and between antiparticle and particle don’t occur at quite the same rate – because of the CP-violating term!

Whilst CP-violation was first experimentally discovered, it was discovered in neutral Kaon interactions – but today, most experimental studies of CP-violation deal with the B-mesons.

Two of today’s best known particle physics experiments investigating CP-violation in the decay of B-mesons are the Belle and BaBar experiments – where B mesons are produced in electron-positron collisions using particle accelerators – the latter at the Stanford Linear Accelerator, and the former at an electron-positron synchrotron collider at KEK in Japan. The interaction points are surrounded by optimised detectors to watch the decay of the B-mesons created. When, say, a decays into some stuff, say a and a couple of leptons, the anti-reaction, a decaying into the corresponding antiparticles, will occur, but at a different rate.

The observation of these decay events inside these detector experiments, like LHCb and Belle, provides insights into the mechanism by which the symmetry is broken to the degree that it is.
The LHCb detector experiment on the LHC is intended to be very similar in nature to these existing experiments – with similar goals.

Not Even Wrong: LHC and Doomsday

Yes, you’ve heard it all before. Black holes, strangelets, and even attack from Nibiru.

I will not spent any time entertaining such things, which we’ve thoroughly dismissed as nonsense already, other than to look at the latest in a long line of rubbish anti-science claims.

Yesterday, a group of LHC critics filed a suit against CERN in the European Court of Human Rights, in Strasbourg . The authors of the suit are physicists, professors and students largely from Germany and Austria, who feel that the operation of the $10 billion Large Hadron Collider near Geneva, poses grave risks for the safety and well-being of the 27 member states of the European Union and their citizens.

Who are these authors? What are their qualifications? What are their arguments? Does their science stack up?

Bosenovas are a new risk theory in the suit, besides the better known Strangelets and Lowered Vacuum State theories. Unlike the others there is some experimental evidence for a Bosenova, but this phenomenon of implosion/explosion has only been produced in small groups of atoms of Rubidium-85 in an ultracold state, a Bose-Einstein Condensate.

What might occur at the LHC, is a new type of Bosenova from what amounts to a BEC used there as a coolant, an ultracold Superfluid Helium II, of about 60 metric tonnes in the LHC ring, and a further 60 tonnes of somewhat warmer Superfluid Helium I in refrigeration plants on the surface connected to the subterranean main ring. Whether possible or not is unknown, no experiments having been done by CERN to rule out the possibility, nor any theoretical model studies.

A bosenova is a very small, supernova-like explosion, which can be induced in a Bose–Einstein condensate (BEC) by changing the magnetic field in which the BEC is located, so that the BEC quantum wavefunction’s self-interaction becomes attractive. This is a poorly understood, very, very interesting phenomenon – but it’s not dangerous, and it’s of little relevance to the LHC.

This stuff is taken from this page…

But superfluid Helium II BEC is being used in great quantities as a coolant in certain nuclear reactors and particle accelerators.

The possibilities of a giant BEC bosenova produced in superfluid Helium II haven’t been investigated. The matter is urgent as 120 T of superfluid Helium II are being used at the Large Hadron Collider at Geneva, whose energies far surpass any other collider’s, not only beam energies, but RF applied, extreme Tesla Fields by superconducting magnets, and electrical energies equivalent to the consumption of Geneva…

“superfluid Helium II BEC”…. well, it’s just liquid helium. Liquid helium’s quantum-hydrodynamical properties are really cool indeed, but it’s just liquid helium. These days, liquid helium is routine technology.

We use LHe cryostats every day in scientific research, and technical applications…. cryostats for scientific experiments, superconducting niobium RF resonator cavities for particle accelerators, superconducting magnets for Nuclear Magnetic Resonance Spectrometers, and (N)MRI imaging machines at most major hospitals.

These are all based around liquid helium cryostats, and none of them ever lead to “Bosenova” explosions, despite being constantly irradiated by cosmic ray particle showers.

“Extreme Tesla fields”?? It’s called a magnetic field. (Usually, when you build a magnet, you do tend to get a magnetic field.) Why is a magnetic field referred to as a “Tesla field”? Is it an attempt to invoke the aura of mystical, magical, pseudoscience, superstition and suspicion that surrounds Tesla’s name?

Also… there’s no such thing as a liquid-helium-cooled nuclear reactor. Unless you’re talking about superconducting magnets in ITER… and it’s not even built yet.

What happens next at the LHC will be the next big experiment in a superfluid Helium II BEC. It’s not part of the design parameters, as physicists assume that the helium will be stable based on its use in the much smaller, much less powerful, up to 250 GeV per beam, RHIC collider in Long Island, NY. CERN’s interests lie in producing the Higgs boson at the LHC, perhaps micro black holes and quark-gluon plasma. Even in the much awaited CERN safety study released last month, there’s absolutely nothing on a possible bosenova implosion/explosion. Of course to test the safety of the enormous LHC to handle foreseen and unforeseen events you’d need another disposable one. But at least it is possible to subject Helium II to some of these high energies and hadron beams as a test. Not at the low energies of the RHIC, but at Fermilab’s Tevatron, currently the most energetic collider with 0.9 TeV per beam, though still far short of the power of the monster LHC at ordinary operating conditions of 7 TeV and ultimately 1,150 TeV collisions of lead ions at nearly twice light speed. Helium II could simply be used as a target by Tevatron beams to see what would happen, besides being exposed to high and fluctuating Tesla fields, ionized by electrical currents, subjected to some of the extreme conditions anticipated at the LHC.

Superconducting cables, superconducting magnets, or superconducting niobium RF cavities in LHe cryostats are already in widespread use around the world. They’re just auxiliary pieces of technology that are associated with the particle accelerator. The liquid helium is just needed to keep those superconductors at the appropriate temperature, and it’s got nothing to do with the particle interactions themselves, and it’s nowhere the actual particle collisions.

Deliberately, carefully twiggling the wavefunction of a Rubidium-87 BEC in order to induce a “bosenova” on purpose is a far cry from saying that a magnet inside a helium dewar can spontaneously explode.

There’s still a suit in the Hawaii courts to delay LHC startup because of safety concerns like black hole and strangelet production. Lately and since I first considered the possible dangers of superfluid helium in my article of March 7, 2008, ‘The Almost Thermonuclear LHC’, the plaintiffs, Dr Walter Wagner and Luis Sancho have announced they will seek an addendum to their suit to include bosenova risks at the LHC.

Oh yes, because they’re so credible. I’m surprised they don’t file an addendum to their lawsuit to include the risk of disruption of the van Allen belts, allowing the return of the Annunaki from the planet Nibiru.

Good references:

CERN’s official LHC backgrounder, brochure and FAQ
http://cdsweb.cern.ch/record/1092437/files/CERN-Brochure-2008-001-Eng.pdf

I will probably post some more later. Until then, your comments and questions are fully welcomed, and will likely determine the direction of the next post.

Water and cooling requirements for large thermal power plants.

I was involved in a bit of discussion recently about the cooling of large thermohydraulic (i.e. heat engine) generatng stations, their use of water, and the like. I was thus inspired to to a bit of thinking, research and writing about the issue. The little essay or discussion piece that I’ve put together can be found here, and I encourage you to please have a read if you’re interested and tell me what you think. I’ll keep it online in that PDF since it’s a little long, and I’ve used a little math typesetting which is a hassle to transcribe across to the blog post.

Energy from Heaven and Earth

Has anyone read this book? If not, I recommend it. It’s one of those books that, despite being nearly thirty years old, seems to remain astonishingly relevant to this day.

For some readers, depending on what you may think of or know of the famous or slightly infamous Edward Teller, some of the points of the book may come across as a little surprising. Energy conservation is not enough. Coal is not enough. Nuclear energy is not enough. … turn down the thermostat… we can reduce our energy requirements for heating by wearing sweaters or warm underclothing. In fact, there are parts of this book where you’d be forgiven for thinking you’re reading the contemporary works of Romm, or Lovins, or Caldicott, where issues like domestic energy use is discussed.

From the origins of petroleum and fossil fuels, to the origins of fission fuels in the collapse of heavy stars, to the oil embargo and OPEC, to the expected detailed treatment of nuclear fission and fusion energy systems, to an impassioned call for reductions in domestic energy use – it’s all here, it’s all fully relevant today, and it’s all very interesting.

ENERGY FROM HEAVEN AND EARTH — Edward Teller — W H Freeman, 1979, 322 p., illus., “In which a story is told about energy from its origins 15 billion years ago to its present adolescence — turbulent, hopeful, beset by problems and in need of help.” Past, present, near and distant future uses of energy are discussed, together with energy policies. A model for the future is included.

A recommended piece of reading.

ScienceDebate 2008: Presidential candidate’s answers to the science questions facing America

http://www.sciencedebate2008.com/www/index.php?id=40

The presidential candidates provide their responses to the most important science questions facing the United States.

Unfortunately, they have not yet posted Senator McCain’s responses yet, hopefully they do so at some point in the near future. So, at the moment, all they’re really presenting are Obama’s responses to the questions. It still makes for interesting reading, though.

Interestingly, although not specifically asked about nuclear energy at all, Obama specifically mentions “A new generation of nuclear electric technologies” as one of his policy goals. Such bipartisan support, even to a slight degree, is a promising sign.