This topic contains 9 replies, has 1 voice, and was last updated by Clark 2 years, 10 months ago.
April 25, 2016 at 14:20 #33702
Thirty years ago the Chernobyl explosion spread radioactive toxins across Europe, killed uncounted thousands through cancer and other radiation-related illnesses, and continues to cause birth defects and illnesses in Belarus, Russia, and Ukraine.
Nothing, zilch, has come up with a proven method for dealing with waste that remains active for millennia.
Interestingly thorium reactors that ‘appear’ to be inherently safe, were not developed because they did not produce a valuable side-product; weapons grade plutonium…
June 28, 2016 at 12:01 #34072
Mark, thanks for posting this; sorry to have been so long in replying. The Guardian article you link to is misleading about the Chernobyl disaster, even more so than the World Nuclear Association article it references. Contrary to both articles, the second, larger, explosion was indeed a (small) nuclear explosion. From the Guardian article:
The net result of this errant test was a massive steam explosion, replete with enough kick to blow the 2,000 ton reactor casting clean through the roof of the reactor building.
Despite the sheer explosive force of the eruption, what ensued was not a nuclear blast. The spectre of the cold war has left an unfortunate conflation between nuclear weapons and nuclear power, but it is important to note that they operate on very different principles. <b>The Chernobyl explosion was instead a conventional high-pressure failure due to excess steam [Clark’s note: this is blatantly misleading]</b>. Seconds later, the remaining coolant flashed to steam and a second <b>even greater explosion</b> occurred, dispersing the shattered nuclear core and effectively terminating the chain reaction.
No mention that the greater explosion was a nuclear explosion. The World Nuclear Association present only one of several theories, known by 2009 at the latest to be false:
Two explosions were reported, the first being the initial steam explosion, followed two or three seconds later by a second explosion, <b>possibly</b> from the build-up of hydrogen due to zirconium-steam reactions.
Note how WNA cover themselves with the word “possibly”. However, if we check Wikipedia:
However, the sheer force of the second explosion, and the ratio of xenon radioisotopes released during the event, indicate that the second explosion could have been a <b>nuclear power transient</b>; the result of the melting core material, in the absence of its cladding, water coolant and moderator, undergoing runaway prompt criticality <b>similar to the explosion of a fizzled nuclear weapon.</b> This nuclear excursion released 40 billion joules of energy, the equivalent of about ten tons of TNT. The analysis indicates that the nuclear excursion was limited to a small portion of the core.
Of course with Wikipedia we must always check references, and the reference for this is an academic paper:
Estimation of Explosion Energy Yield at Chernobyl NPP Accident, Sergey A. Pakhomov, Yuri V. Dubasov, Pure and Applied Geophysics, May 2010, Volume 167, Issue 4, pp 575-580
The value of the 133Xe/133mXe isometric activity ratio for the stationary regime of reactor work is about 35, and that for an instant fission (explosion) is about 11, which allowed estimation of the nuclear component of the instant (explosion) energy release during the NPP accident. Atmospheric xenon samples were taken at the trajectory of accident product transfers (in the Cherepovetz area); these samples were measured by a gamma spectrometer, and the 133Xe/133mXe ratio was determined as an average value of 22.4. For estimations a mathematic model was elaborated considering both the value of instant released energy and the schedule of reactor power change before the accident, as well as different fractionation conditions on the isobaric chain. Comparison of estimated results with the experimental data showed the value of the instant specific energy release in the Chernobyl NPP accident to be 2·105–2·106 J/Wt or 6·1014–6·1015 J (100–1,000 kt). This result is matched up to a total reactor power of 3,200 MWt. However this estimate is not comparable with the actual explosion scale estimated as 10t TNT. This suggests a local character of the instant nuclear energy release and makes it possible to estimate the mass of fuel involved in this explosion process to be from 0.01 to 0.1% of total quantity.
Ironically, this “nuclear power excursion”, otherwise known as prompt criticality, blew the damaged core to pieces, dispersing the fuel and terminating the nuclear reaction. Although this released further radioactive pollutants into the atmosphere it prevented ongoing meltdown such as the three that apparently continue at Fukushima, five years after that disaster.
June 28, 2016 at 12:07 #34073
This does appear to be deliberate deception by the Guardian journalist David Robert Grimes, since parts of the article seem to have been directly copied from Wikipedia. Therefore, Grimes must have read the Wikipedia article and thus known that the second explosion was a prompt-critical explosion.
June 28, 2016 at 12:36 #34077
Grief, that Guardian article is a travesty. It tries to separate nuclear power generation from nuclear weapons, and therefore fails to mention that the Chernobyl reactor design was compromised, specifically because it was designed to perform two purposes – electricity production and plutonium production for nuclear weapons fabrication, as was the British Magnox programme (though the British reactor design was probably safer).
It also makes much reference to UNSCEAR, the group set up to “handle” the conflict of interest between the UN World Health Organisation WHO and the Nuclear Non-Proliferation Treaty, administered by the UN International Atomic Energy Authority IAEA. UNSCEAR seems a rather shady body as evidenced by the brevity of the Wikipedia article about it. The entire article is based on <b>just one reference<b>, and that one is from UNSCEAR itself!
Grief I could go on and on… I haven’t even started on how we got into this mess, and the sacking of Alvin Weinberg.
July 1, 2016 at 22:06 #34138
Note from the Pakhomov and Dubasov paper, that even at the very low efficiency of an unconfined reaction, less than a thousandth of the nuclear fuel in the core was sufficient to produce a nuclear explosion.
There is more nuclear fuel in the core of just one power reactor than would be exploded in all-out global nuclear war. We already have over four hundred such reactors on Earth, plus many reactors for weapons and isotope manufacture. The contamination potential doesn’t bear thinking about.
July 2, 2016 at 06:40 #34140
Many thanks Clark for your very informative comments. It should not be forgotten that the so-called depleted Uranium weapons have also been shown to involve a nuclear fusion reaction. The range of isotopes found in samples taken from sites hit by depleted uranium weapons in the Iraq war has been shown to be incompatible with any description of the action of the weapons not involving some kind of thermonuclear reaction, and most consistent with a thermonuclear fission reaction. Hence the sickness of many Iraq war veterans is unsurprising. The British and US militaries have kept virtually all the scientific research on depleted uranium secret, because the legal reality is that depleted uranium weapons are nuclear weapons, and their use on the battlefield is illegal. The devastation of society due to nuclear fallout in all countries where depleted uranium has been used – including Iraq, Afghanistan and Serbia – is beyond comprehension.
July 2, 2016 at 16:41 #34159
Bhante, I agree entirely that depleted uranium (DU) weapons should be banned, but not for the reasons given in your comment. There is much misunderstanding about DU, including just how much of the stuff there is:
Zoom in for detail. That’s just one of three such yards in the USA alone. Each of those little blobs is a metal cylinder of depleted uranium hexafluoride about the size of a van, stacked two or three high. You can see that they’re slowly turning black as they corrode away from both inside and out like this:
I suppose it’s cheaper to stockpile DU than to dispose of it properly; there may also be misguided objections from various environmentalist groups which are hindering disposal. Such DUF6 is the inevitable tailings from the uranium enrichment process, primarily for nuclear electricity generation. To increase the proportion of U235 above that in natural uranium, excess U238 has to be removed, and that’s what is in those yards. Let’s hope the economic system doesn’t collapse since staff are required to constantly patch up the cylinders. Hexafluoride is a very water soluble form of uranium, making the uranium very easy to ingest. It HAS to be kept out of the groundwater.
Uranium is a potent poison chemically; it’s a toxic metal most affecting the kidneys, but also the rest of the renal system, the brain and central nervous system, DNA, bone and muscle, reproduction, the respiratory and gastrointestinal systems, the liver, skin, eyes, and the immune system. It really is very nasty, without considering its nuclear properties at all. Radioactive effects proceed mostly from its breakdown product radon, which is radioactive but also gaseous making it very mobile. Chemical toxicity must not be underestimated as to do so trivialises its effects, which would let the entire chemical industry off the hook.
I hope that the above convinces you that I take DU very seriously indeed, and I hope you’ll forgive me for questioning some of the claims you refer to in your comment. The debate has become polarised, with cover-up on the establishment side but also exaggerated and sensationalist claims from some anti-nuclear activists. I oppose this because false claims are easily discredited and alienate the scientific community, who we need to take the matter seriously when they advise governments.
Please therefore link to references to support the claim: “The range of isotopes found in samples taken from sites hit by depleted uranium weapons in the Iraq war has been shown to be incompatible with any description of the action of the weapons not involving some kind of thermonuclear reaction, and most consistent with a thermonuclear fission reaction”. The thermonuclear reaction is the fusion reaction, not fission, though a fission explosion is employed to ignite fusion. Uranium and plutonium can’t be fused since the reaction products would have atomic number and atomic weight about twice as high as the highest in the table of elements. The evidence you refer to, if accurate, would more likely indicate either that an H-bomb had been exploded (which would be impossible to conceal), or that the isotopes had come from some other source…
…see, I have encountered tentative indications of a cover-up, probably corporate, that some weapons sold as being DU are not made from DU at all, but from reactor waste – try searching “dirty DU”. Why the hell this was done I haven’t a clue but I think it is being concealed (played down to the max, and muddying of the water) because some company (probably a major armaments manufacturer) would get sued out of existence, and the US etc. governments could never permit that. So please post those links as they may lead me to another piece of the jigsaw.
July 2, 2016 at 20:09 #34162
It would probably make more sense, and be easier legally, to get depleted uranium weapons classed and banned as chemical weapons, rather than nuclear weapons.
The military’s stated reason for using DU is for armour-piercing munitions, because of DU’s great hardness and high density. Given the enormous stockpiles of true depleted uranium, this reason provides no excuse whatsoever for using “dirty DU”. But actual DU should still be banned because of its chemical toxicity, especially as some is vaporised and some becomes an aerosol when DU munitions hit armour plating, their intended target, leading to uranium being inhaled.
“Dirty DU” is a misnomer (part of the attempt to spread confusion, in my opinion). Depletion (of U235) is the other side of the coin to enrichment. “Dirty DU” hasn’t been depleted; it’s a by-product from the reprocessing of “spent” nuclear fuel.
July 18, 2016 at 22:03 #34262
Continued from this comment:
The uranium and/or plutonium fuel in each nuclear warhead degrades after about 9 years, and has to be replaced. That’s why we have a totally white elephant called ‘nuclear power’, which the markets won’t touch but the government totally subsidises because it needs a constant supply of fuel for all those nuclear warheads, to ‘keep us safe’.
Well it was like that (Magnox etc.) but I don’t think it is any more. Mostly, nuclear power just dwarfs weapons manufacture, making the weapons side seem insignificant – I suppose it give it cover. 180 warheads for Trident, you say? That’s only about a tonne of plutonium, isn’t it? I think there’s about 50 tonne under guard, last I heard at Sellotape. What’s the mass of the fuel in a typical Pressurised Water Reactor? The US has about half a million tonnes of depleted uranium, which implies the production of about fifty thousand tonnes of PWR fuel rods, which implies spent fuel in a similar sort of quantity. This will all need to be transmuted in something like AMSTER:
July 18, 2016 at 22:48 #34263
We don’t really know what the dangers are of Molten Salt reactors; there have only been two built that anyone’s heard of; the Aircraft Reactor Experiment ARE, and the Molten Salt Reactor Experiment MSRE in the late ’60s early ’70s, both at Oak Ridge National Laboratory in the US. Things like AMSTER are conceptual; designs and computer simulations.
MSRs look safer in theory; no pressurisation and can’t melt down for a start. The bad news is they need graphite moderator, and that’s what caught fire at Windscale (and Chernobyl, but that was an effect of the accident rather than a cause). Weinberg designed both the MSRs and the PWR, but he wanted only the MSR licensed for civilian use, considering the PWR suitable for smaller scale military propulsion only. So they just sacked him.
The MSRE was under ten megawatt. I’d like to see a 100 megawatt MSR prototype. It’s a very versatile design because the nuclear fuel is liquid (molten at about 650 centigrade). Suitably prepared, U233, U235, plutonium and “spent” fuel can all be fed into the reaction and, in theory, burned almost completely down to reaction products; isotopes in the middle of the table of elements, many of which have industrial uses and most having much shorter half-life than the spent fuel that went in.
It looks good in principle. Maybe one day a better way to dispose of “spent fuel” AKA “transuranic waste” might be found, but the little MSRE looked remarkably tame, as nuclear power reactors go, so I think it’s time to try the next size up. They’ve been making the “waste” for seventy years and not one disposal reactor has yet been prototyped.