I have seen a lot of people worry about the radiation hazard of depleted Uranium to populations.
I could care less - Uranium is quite toxic as a chemical. The chemical hazard of Uranium to people is far far higher than its radiation hazard, enough so that any sane risk calculation would ignore the risk contribution from the radiation - the radiation portion of the risk is far smaller than the uncertainty in the associated chemical hazards.
I was a safety officer in a chemical process lab > 50 years ago. I remember a meeting where a very old bottle of a particularily dangerous chemical was found on a shelf. Nobody knew about it. One chemist was worried that it was a carcinogen. The old expert's comment was - 'who cares, that stuff is classified as a chemical weapon. It will kill you long before you get cancer from it."
In terms of risk to life, property and large scale destruction, I worry about dam failures.
I believe that long term federal funding of R&D at universities is the source of such nonscience. The politicians pick and choose what research to fund, dangling money to university post docs, assistant professors, and the professors who make the paper-count and funding cut. For example, the US approach to CO2-caused global warming was creating the $500M/year Renewable Energy Labs, which PRESUMES such an effect and EXCLUDES nuclear power. It distributes money to build an UNRELIABLE, expensive electricity system, because Congress lures voters with "green" mantras.
This article's distorted official nonscience about radiation effects on health is another example.
Did you ever notice how many academic papers end with "needs more study", a flag to attract funding.
Gone are the days when a monopoly took 10% of your phone bill to fund scientists who tinkered with semiconductors to invent transistors, or listen to radio noise to discover the origin of the universe.
Perhaps the answer is to create fewer PhDs scrambling for funding so the universities can pay them. Another might be to fund research with less political direction, somehow. Or maybe research should be funded by the billionaires who want to pay back society. That's how musicians and artists were funded centuries ago.
Similar sort of misinformation going on in Canada, no surprise.
It comes mostly from perennial antinuke activist Gordon Edwards, who frequently presents himself as Canadian Coalition for Nuclear Responsibility (CCNR).
He regularly receives "intervenor" funding from the CNSC - Canadian Nuclear Safety Commission - either directly or by contract from various antinuke groups, such as CELA (Canadian Environmental Law Association).
In recent years, Edwards has been campaigning against Canada’s project for used CANDU fuel disposal in a DGR (Deep Geological Repository), which is now slated to be built in western Ontario, about 30km west of the town of Ignace – which applied to participate in the site selection process 15 years ago, and voted overwhelmingly in favor of “hosting” the project early last year (2024).
Needless to say, Edwards’ scare mongering includes “the I-129 problem” – see linked picture below, which is a screen grab from a YouTube video from one of Edwards’ presentations last year.
First of all, it’s rare that nuclear fuel bundles have so much as a pinhole defect: When one does, it is immediately detected in the reactor, and the defective fuel bundle is removed.
Secondly, the thermal conditions inside the reactor are pretty fierce, with 300°C and high-pressure, high-velocity flow.
Once the defective fuel bundle is removed and placed into the cooling pool for storage, it stops leaking, because the thermal conditions are benign.
Used nuclear fuel bundles are barely warm, after 50 to 70 years of surface storage, whereas the boiling point of Iodine is 184.3°C, and for Cesium the boiling point is 671°C.
Perhaps more importantly, Edwards is talking about the extremely long-live isotope Iodine-129, not the short-lived isotope Iodine-131.
Iodine-131 is of concern in reactor operation, but NOT in long-term storage: It is completely gone in a few months following removal from the reactor. Iodine-129 remains in the used fuel for a very long time, but its radioactivity is extremely low: Canada’s nuclear regulator, the CNSC, requires prophylactic iodine pill distribution in the vicinity of nuclear power plants, but does NOT require their distribution around long-term used fuel storage sites, because the remaining Iodine-129 is insignificant, and there is no possibility of a million used fuel bundles getting pulverised while in storage – at least not until the next ice age, with the advancement of thick glaciers.
Third, let’s not forget – as Edwards does every time – that used CANDU fuel is 99% natural uranium, with just 0.6% fission products.
Out of that 0.6% only a small fraction are volatile species like Iodine-129 (I129).
Most is trapped in the ceramic pellet crystalline structure, with a small fraction available for release if the fuel were damaged during a transport accident.
Each fuel bundle is comprised of ceramic uranium fuel pellets, containing 19.2kg of Uranium, inside 37 zircaloy tubes that are welded shut (ie. half a kilo of uranium pellets in each tube).
After 50 years of storage, prior to shipment to a DGR, the amount of I129 in used fuel is 0.29 MBq/kgU (Where “MBq” stands for Mega-Becquerels or millions of Becquerels, and is listed per kilogram of Uranium (kgU) initially in the fuel bundles).
For comparison, the human body contains about 0.008 MBq of radioactivity, more than half of which is natural Potassium-40 (K40).
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) use a dose conversion factor of 0.044 mSv/MBq for I129.
So, if ALL the I129 in a kilogram of used fuel were released and 100% of it absorbed by nearby people, the radiation dose they would receive (in milli-Sieverts, or “mSv”) would be 0.29 MBq/kgU x 0.044 mSv/MBq = 0.013 mSv (collective dose, not individual dose).
For comparison, the typical annual radiation dose Canadians get from natural background sources is between about 1.2 and 4 mSv, or roughly 150 times more (depending on where in Canada you live).
Of course in reality, only a tiny fraction of the I129 in that kilogram of used fuel could be released, and it’s extremely unlikely that anywhere near 100% of that would de absorbed by nearby people (or anything else).
Lastly, let’s remember that Iodine-129 occurs naturally in trace quantities in the environment, because uranium is ubiquitous in the ground and in oceans and lakes:
Somewhat like Radon gas, I129 comes from uranium, albeit in somewhat different ways.
While Radon is simply a decay product of uranium, I129 is produced by spontaneous fission of uranium, as well as fission due to neutrons in cosmic rays hitting uranium atoms.
Jaro knows what he's talking about. Choristers should check out his Facebook page.
I would only add it's not THE dose, It's the dose rate profile. I-129 not only can only deliver a minuscule dose, it can only deliver that dose very very slowly. That's why dose rate dependent models such as SNT need arbitrary precision arithmetic in order to avoid 64 bit underflow when dealing with I-129.
Dear David, “factual” sounds great, but the “balanced” part sounds weird: Facts balanced with fiction?
Not my cup of tea.
Regarding the plutonium issue.
The quote that “all plutonium is considered to be of equal "sensitivity" for purposes of IAEA safeguards in non-nuclear weapon States” does NOT jibe with what IAEA Safeguards specialist Dr. Jeremy Whitlock is on record as stating: IAEA definitely recognises different degrees (non-equal) of sensitivity.
You should get a quote from him.
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Personally, I prefer to quote the US DoE from their April 2014 weapons plutonium disposition agreement between Russia and the US, “Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon‐Grade Plutonium Disposition Options”.
“Although isotopic degradation is not included in the explicit conditions for disposition codified in the PMDA, as amended, it was one of the key considerations in the negotiation of burnup limits for the Russian sodium-cooled fast reactors.
Isotopic degradation occurs so much faster in light-water cooled reactors that it was effectively ignored as a consideration in setting the 20 MW-d/kgHM burnup limit for LWRs.”
“An additional consideration, which is not codified in the PMDA but which underlies the actual disposition criteria, is isotopic degradation.
The batch-average burnup values were included in the disposition criteria in part to ensure isotopic degradation significantly beyond the PMDA definition for weapons plutonium (Pu-240/Pu-239 ratio < 0.10).
The BN-800 chief designer estimated that the Pu240/Pu-239 isotopic ratio averaged over any given discharged batch of BN-800 fuel would be about 0.17.
This number was also officially reported by Rosatom.
Thus, an additional implicit requirement beyond the specific requirements codified in the PMDA is that the Pu-240/Pu-239 isotopic ratio averaged over a given batch of discharged spent plutonium fuel assemblies should be ≥ 0.17.
There is also a good article on the topic of spontaneous neutron emission at the following link.
It's mainly about U238 in HEU, but the issue is the same: Time between spontaneous neutron emission (Pu240 being much worse), for various compositions, and how it affects weapon design/performance.
On the Proliferation Potential of Uranium Fuel for Research Reactors at Various Enrichment Levels
Alexander Glaser
Program on Science and Global Security, Princeton University , Princeton, NJ, USA
Published online: 01 Feb 2007.
---------------
The fission yield (or "explosive yield") is calculated using the following semi-empirical formula, that is based on numerous experiments (published in the journal Nuclear Science & Engineering), and assumes a typical Gaussian fission pulse profile, where the area under the curve is the total fission yield energy (and which is roughly calculated as pulse height times half-width)
'k' is the neutron multiplication factor or reactivity.
For example, for 4% excess reactivity k = 1.04 and the yield is 2.5 tonnes TNT equivalent.
Y(tTNT) = 7.246E-27 * exp (4 * ln (k - 1) + 74)
Examples of a few calculation results are as follows.
k.……......……………Yield
1.001………0.001 kgTNT
1.002………0.016 kgTNT
1.005…..……0.62 kgTNT
1.007…….……2.4 kgTNT
1.01……………10 kgTNT
1.04….……..2550 kgTNT
1.1……….……..100 tTNT
1.2……………..1.6 ktTNT
1.3……………..8.1 ktTNT
1.4……………25.5 ktTNT
---------------------------------------------
Weapons Pu production reactors run the fuel to one-tenth the burnup of CANDU fuel, and CANDU reactors run the fuel to 6½ times less burnup than LWRs.
The issue with fuel burnup is that it affects the isotopic composition of the Pu produced: At very low burnup it’s almost 100% Pu239, while at high burnup it’s roughly 50/50, with the other 50% being Pu240.
Now, if you take into account that a bomb “pit” has a total of about 5kg of Pu or about 20kg U235, then the total neutron emission rate comes to about 6n/s for U235 and 2,500,000n/s for Pu extracted from high burnup fuel (or reactor-grade Pu, “RGPu”, in contrast to weapons grade, “WGPu”).
What matters here is the inverse of those numbers: How much time BETWEEN NEUTRONS on average.
That comes to 0.4 MICRO-seconds for RGPu and 0.17 seconds for U235.
In a mass of fissile material that is being “assembled” from one or more pieces, the time of concern is how much elapses between when the assembly has reached a reactivity (neutron multiplication factor) of 1.000 and whatever maximum reactivity it could potentially reach in its optimum configuration (that might be a reactivity on the order of 1.2 for a fairly effective bomb).
But regardless of where between 1.000 and 1.2 the reactivity is at any stage of the assembly, nothing happens until the first neutron appears, to trigger the fission chain reaction: Theoretically, if there were never any neutrons around, the 1.2 reactivity configuration could exist indefinitely.
In reality, we know there will be neutrons around, with little time for assembly between them: 0.4 micro-seconds for RGPu and 0.17 seconds for U235.
Now, guesstimating the approximate size of the components and their assembly speed, we can easily see which option has a good chance of succeeding and which doesn’t.
For example, in a U235 gun-type device, the assembly speed might be around 1.5km per second, while for an implosion device (with radially converging shock wave) it might be as much as 6km per second.
Also, for the U235 gun-type device the required travel distance between 1.000 and 1.2 reactivity might be around 10cm, while for the Pu implosion device it might be about 5cm of radial distance.
So, traveling 10cm at 1.5km per second would take 67 micro-seconds, while traveling 5cm at 6km per second would take 8 micro-seconds.
Now divide that into the average time between neutrons, and you get (0.17 ÷ 0.000,067 = ) a factor of 2,540 for U235 assembly, but you get only (0.000,000,4 ÷ 0.000,008 = ) a factor of one-twentieth for RGPu assembly.
Conclusion: The U235 device has ample margin for success, while the RGPu device has none, even with sophisticated implosion assembly.
In fact, the U235 is likely to disintegrate from its peak reactivity configuration before a neutron appears: Consequently electronic devices are required to supply external neutrons, in timing with peak reactivity during assembly.
Citizendium is not Wikipedia. We don't suppress debate, we allow each side to make their case, in their own words. That is what I meant by "balance", not giving facts and nonsense equal weight. The nonsense appears only on our debate pages, and is easily debunked by our nuclear experts. These discussions allow our readers, mostly journalists, to see that they are not getting only one side of an issue. It is important that we include the nonsense, if it is widely believed. I haven't heard anything about the I-129 problem, but if I do, we will publish both that and Jack's rebuttal.
The debate on whether plutonium can be "spiked" with non-fissile isotopes to avoid the risk of diversion, is one of the few debates that we have not been able to resolve. It comes down to details of weapons design that are classified. On the Yes side we have the articles cited on the design of the ThorCon and the Integral Fast Reactor. On the No side, we have the articles by weapons designers Mark and Garwin, and the statement from the IAEA, which presumably had access to the classified information.
My take is that we will never be able to resolve this debate, and therefore we must do better on diversion control, especially if we are considering deploying thousands of reactors worldwide. But we are getting way off track. Check our article on Nuclear Proliferation. Maybe we can continue this discussion on your Rad Toolbox page.
As for “Maybe we can continue this discussion on your Rad Toolbox page”, that would be really off-topic in that group – although I generally don’t delete posts by members, when they go off-topic.
Similarly for my other group, “Communities [interested in] hosting nuclear storage / repository facilities”.
I haven’t thought it important to create a group specifically on the topic of nuclear weapons and proliferation, but when the issue does come up in other forums, I usually cite the US “Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon‐Grade Plutonium Disposition Options”, which is quite clear on Plutonium and is an official statement.
LD50 for potassium iodide in an adult is the ballpark of 0.1 kg. Ten grams causes acute poisoning symptoms. I-129 will kill you chemically before it can irradiate you to death. It isn't a radiological hazard to begin with.
You know the answer. Fear sells. Easy to score points, and make a buck.
Just finished Robert Zubrin's "merchants of despair". It is a real eye-opener.
So sad that the most potent energy source available to mankind has become ensconced in a seemingly perfectly inert urn of fear, ignorance and politics. How do we turn things around?
Just a side note. You said: "One of the more abundant fission products is iodine-129. " I-129 makes up 0.7% of the fission products. Still, I suppose that means there are kg produced per year per reactor.
I-131 produces 4 billion times more radiation energy than equal quantities of I-129. The only real evidence of harm from I-131 that I am aware of was Chernobyl, when they did not stop kids from consuming highly contaminated food. Some of these kids did get 1Gy and more in the months of their exposure. This would be a few tens of mGy/day. Doses over the same time period from equal amounts of I-129 would be measured in pico-Gy/day. BTW, some of the effects in Belarus/Ukraine were due to the kids having Iodine deficient diets.
Just for fun I asked what if all the I in a thyroid was I-129. A thyroid can only contain about 10^19 I atoms. Imagine that they were all I-129, all the time. There are about 500 trillion seconds in a half life (5* 10^14). That means about 20,000 Bq of low energy radiation.
"More abundant" was misleading. Thanks correction.
It's not the dose. It's the dose rate profile. I know I sound like I'm in a loop, but no matter how many times I repeat that mantra, you guys keep talking about THE dose. The choir seems to be made up of closet LNTers.
"Radiant energy" sounds like dose to me. Did you mean "radiant power"?
I don't think so. According to my numbers, ingesting a nanogram of I-131all aty once will result in a total dose that is 4.2 billion time larger than ingesting a nanogram of I-129, in agreement with your numbers. But the dose rate profiles
are also quit different in shape. The I-129 DRP will fall off with a half life of about 80 days (teh bio half-life) The I-131 DRP wil fall off with a half-life slightly smaller than 8 days. (teh decay half-life).
It's not just dose rate. That's as bad as it's just dose. It's dose rate profile.
I showed that peak dose rates were pico-Gy/day. I am not worried about dose rate profile in this situation, and you can't consider biological half life when you don't know the rate at which the I-129 is being ingested. I simply showed that no matter how much I-129 is in the environment, it is unlikely to give dose rates above a few pico-Gy/day.
I do acknowledge that I meant Radiation power, not energy
Funny. I asked ChatGPT to compare the risks of I129 with natural iodine and compare dose conversion factors and LD50s for typical iodine compounds.
It proceeded, or rather not, to decide not to answer my question and instead provide a third party link to a suicide call center of some sorts.
Indeed, it is rather worrying to see dairly newspaper articles of kids killing themselves with radioactive iodine compounds stolen from the plutonium reprocessing plant around the corner. What's the world coming to? And this comes after reports of kids doing "toping" with 60000 RPM carbon composite centrifuges doing up high enriched uranium in their treehouses!!
Well as long as the nanny state trumps Skynet we at least don't have to worry about "artificial" intelligence taking over!
May I remind everybody that AI generated content is banned from this site. Regurgitated conventional wisdom falls somewhere between vulgarity and partisan political statements.
But it's not that simple. I've corresponded with Prof Wainwright on her paper. She honestly believes she has done nuclear power a favor by obliquely questioning deep geologic disposal of I-129. She has been so thoroughly indoctrinated she does not need to be suborned.
I have seen a lot of people worry about the radiation hazard of depleted Uranium to populations.
I could care less - Uranium is quite toxic as a chemical. The chemical hazard of Uranium to people is far far higher than its radiation hazard, enough so that any sane risk calculation would ignore the risk contribution from the radiation - the radiation portion of the risk is far smaller than the uncertainty in the associated chemical hazards.
I was a safety officer in a chemical process lab > 50 years ago. I remember a meeting where a very old bottle of a particularily dangerous chemical was found on a shelf. Nobody knew about it. One chemist was worried that it was a carcinogen. The old expert's comment was - 'who cares, that stuff is classified as a chemical weapon. It will kill you long before you get cancer from it."
In terms of risk to life, property and large scale destruction, I worry about dam failures.
I believe that long term federal funding of R&D at universities is the source of such nonscience. The politicians pick and choose what research to fund, dangling money to university post docs, assistant professors, and the professors who make the paper-count and funding cut. For example, the US approach to CO2-caused global warming was creating the $500M/year Renewable Energy Labs, which PRESUMES such an effect and EXCLUDES nuclear power. It distributes money to build an UNRELIABLE, expensive electricity system, because Congress lures voters with "green" mantras.
This article's distorted official nonscience about radiation effects on health is another example.
Did you ever notice how many academic papers end with "needs more study", a flag to attract funding.
Gone are the days when a monopoly took 10% of your phone bill to fund scientists who tinkered with semiconductors to invent transistors, or listen to radio noise to discover the origin of the universe.
Perhaps the answer is to create fewer PhDs scrambling for funding so the universities can pay them. Another might be to fund research with less political direction, somehow. Or maybe research should be funded by the billionaires who want to pay back society. That's how musicians and artists were funded centuries ago.
Similar sort of misinformation going on in Canada, no surprise.
It comes mostly from perennial antinuke activist Gordon Edwards, who frequently presents himself as Canadian Coalition for Nuclear Responsibility (CCNR).
He regularly receives "intervenor" funding from the CNSC - Canadian Nuclear Safety Commission - either directly or by contract from various antinuke groups, such as CELA (Canadian Environmental Law Association).
In recent years, Edwards has been campaigning against Canada’s project for used CANDU fuel disposal in a DGR (Deep Geological Repository), which is now slated to be built in western Ontario, about 30km west of the town of Ignace – which applied to participate in the site selection process 15 years ago, and voted overwhelmingly in favor of “hosting” the project early last year (2024).
Needless to say, Edwards’ scare mongering includes “the I-129 problem” – see linked picture below, which is a screen grab from a YouTube video from one of Edwards’ presentations last year.
Edwards also includes “the Cs-135 problem”.
https://cdn-images-1.medium.com/v2/resize:fit:1500/1*oG8Uka43J0Z_98ld_xYXqQ.png
My comments on Edwards’ claims were as follows:
First of all, it’s rare that nuclear fuel bundles have so much as a pinhole defect: When one does, it is immediately detected in the reactor, and the defective fuel bundle is removed.
Secondly, the thermal conditions inside the reactor are pretty fierce, with 300°C and high-pressure, high-velocity flow.
Once the defective fuel bundle is removed and placed into the cooling pool for storage, it stops leaking, because the thermal conditions are benign.
Used nuclear fuel bundles are barely warm, after 50 to 70 years of surface storage, whereas the boiling point of Iodine is 184.3°C, and for Cesium the boiling point is 671°C.
Perhaps more importantly, Edwards is talking about the extremely long-live isotope Iodine-129, not the short-lived isotope Iodine-131.
Iodine-131 is of concern in reactor operation, but NOT in long-term storage: It is completely gone in a few months following removal from the reactor. Iodine-129 remains in the used fuel for a very long time, but its radioactivity is extremely low: Canada’s nuclear regulator, the CNSC, requires prophylactic iodine pill distribution in the vicinity of nuclear power plants, but does NOT require their distribution around long-term used fuel storage sites, because the remaining Iodine-129 is insignificant, and there is no possibility of a million used fuel bundles getting pulverised while in storage – at least not until the next ice age, with the advancement of thick glaciers.
Third, let’s not forget – as Edwards does every time – that used CANDU fuel is 99% natural uranium, with just 0.6% fission products.
Out of that 0.6% only a small fraction are volatile species like Iodine-129 (I129).
Most is trapped in the ceramic pellet crystalline structure, with a small fraction available for release if the fuel were damaged during a transport accident.
Each fuel bundle is comprised of ceramic uranium fuel pellets, containing 19.2kg of Uranium, inside 37 zircaloy tubes that are welded shut (ie. half a kilo of uranium pellets in each tube).
After 50 years of storage, prior to shipment to a DGR, the amount of I129 in used fuel is 0.29 MBq/kgU (Where “MBq” stands for Mega-Becquerels or millions of Becquerels, and is listed per kilogram of Uranium (kgU) initially in the fuel bundles).
For comparison, the human body contains about 0.008 MBq of radioactivity, more than half of which is natural Potassium-40 (K40).
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) use a dose conversion factor of 0.044 mSv/MBq for I129.
So, if ALL the I129 in a kilogram of used fuel were released and 100% of it absorbed by nearby people, the radiation dose they would receive (in milli-Sieverts, or “mSv”) would be 0.29 MBq/kgU x 0.044 mSv/MBq = 0.013 mSv (collective dose, not individual dose).
For comparison, the typical annual radiation dose Canadians get from natural background sources is between about 1.2 and 4 mSv, or roughly 150 times more (depending on where in Canada you live).
Of course in reality, only a tiny fraction of the I129 in that kilogram of used fuel could be released, and it’s extremely unlikely that anywhere near 100% of that would de absorbed by nearby people (or anything else).
Lastly, let’s remember that Iodine-129 occurs naturally in trace quantities in the environment, because uranium is ubiquitous in the ground and in oceans and lakes:
Somewhat like Radon gas, I129 comes from uranium, albeit in somewhat different ways.
While Radon is simply a decay product of uranium, I129 is produced by spontaneous fission of uranium, as well as fission due to neutrons in cosmic rays hitting uranium atoms.
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PS. Readers here are invited to invited to join my “Rad Toolbox” group on Facebook: https://www.facebook.com/groups/150981218802374
Jaro knows what he's talking about. Choristers should check out his Facebook page.
I would only add it's not THE dose, It's the dose rate profile. I-129 not only can only deliver a minuscule dose, it can only deliver that dose very very slowly. That's why dose rate dependent models such as SNT need arbitrary precision arithmetic in order to avoid 64 bit underflow when dealing with I-129.
I'm disappointed to hear this about Gordon Edwards. He has contributed some commentary to Citizendium on the topic of plutonium diversion.
"https://citizendium.org/wiki/Nuclear_proliferation/Debate_Guide#Blocking_Diversion_of_Plutonium_by_%22Spiking%22_the_Fuel
I would like to see your response to this. As Engineering Editor at CZ, I need to ensure that we have factual and balanced coverage of all debates.
Dear David, “factual” sounds great, but the “balanced” part sounds weird: Facts balanced with fiction?
Not my cup of tea.
Regarding the plutonium issue.
The quote that “all plutonium is considered to be of equal "sensitivity" for purposes of IAEA safeguards in non-nuclear weapon States” does NOT jibe with what IAEA Safeguards specialist Dr. Jeremy Whitlock is on record as stating: IAEA definitely recognises different degrees (non-equal) of sensitivity.
You should get a quote from him.
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Personally, I prefer to quote the US DoE from their April 2014 weapons plutonium disposition agreement between Russia and the US, “Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon‐Grade Plutonium Disposition Options”.
https://fissilematerials.org/library/doe14a.pdf
A few quotes:
“Although isotopic degradation is not included in the explicit conditions for disposition codified in the PMDA, as amended, it was one of the key considerations in the negotiation of burnup limits for the Russian sodium-cooled fast reactors.
Isotopic degradation occurs so much faster in light-water cooled reactors that it was effectively ignored as a consideration in setting the 20 MW-d/kgHM burnup limit for LWRs.”
“An additional consideration, which is not codified in the PMDA but which underlies the actual disposition criteria, is isotopic degradation.
The batch-average burnup values were included in the disposition criteria in part to ensure isotopic degradation significantly beyond the PMDA definition for weapons plutonium (Pu-240/Pu-239 ratio < 0.10).
The BN-800 chief designer estimated that the Pu240/Pu-239 isotopic ratio averaged over any given discharged batch of BN-800 fuel would be about 0.17.
This number was also officially reported by Rosatom.
Thus, an additional implicit requirement beyond the specific requirements codified in the PMDA is that the Pu-240/Pu-239 isotopic ratio averaged over a given batch of discharged spent plutonium fuel assemblies should be ≥ 0.17.
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Picture:
https://cdn-images-1.medium.com/v2/resize:fit:1500/1*eHcR8_Z9yLKPj2wi-Dzfew.jpeg
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There is also a good article on the topic of spontaneous neutron emission at the following link.
It's mainly about U238 in HEU, but the issue is the same: Time between spontaneous neutron emission (Pu240 being much worse), for various compositions, and how it affects weapon design/performance.
https://sci-hub.st/10.1080/08929880600620542
On the Proliferation Potential of Uranium Fuel for Research Reactors at Various Enrichment Levels
Alexander Glaser
Program on Science and Global Security, Princeton University , Princeton, NJ, USA
Published online: 01 Feb 2007.
---------------
The fission yield (or "explosive yield") is calculated using the following semi-empirical formula, that is based on numerous experiments (published in the journal Nuclear Science & Engineering), and assumes a typical Gaussian fission pulse profile, where the area under the curve is the total fission yield energy (and which is roughly calculated as pulse height times half-width)
'k' is the neutron multiplication factor or reactivity.
For example, for 4% excess reactivity k = 1.04 and the yield is 2.5 tonnes TNT equivalent.
Y(tTNT) = 7.246E-27 * exp (4 * ln (k - 1) + 74)
Examples of a few calculation results are as follows.
k.……......……………Yield
1.001………0.001 kgTNT
1.002………0.016 kgTNT
1.005…..……0.62 kgTNT
1.007…….……2.4 kgTNT
1.01……………10 kgTNT
1.04….……..2550 kgTNT
1.1……….……..100 tTNT
1.2……………..1.6 ktTNT
1.3……………..8.1 ktTNT
1.4……………25.5 ktTNT
---------------------------------------------
Weapons Pu production reactors run the fuel to one-tenth the burnup of CANDU fuel, and CANDU reactors run the fuel to 6½ times less burnup than LWRs.
The issue with fuel burnup is that it affects the isotopic composition of the Pu produced: At very low burnup it’s almost 100% Pu239, while at high burnup it’s roughly 50/50, with the other 50% being Pu240.
Now, if you take into account that a bomb “pit” has a total of about 5kg of Pu or about 20kg U235, then the total neutron emission rate comes to about 6n/s for U235 and 2,500,000n/s for Pu extracted from high burnup fuel (or reactor-grade Pu, “RGPu”, in contrast to weapons grade, “WGPu”).
What matters here is the inverse of those numbers: How much time BETWEEN NEUTRONS on average.
That comes to 0.4 MICRO-seconds for RGPu and 0.17 seconds for U235.
In a mass of fissile material that is being “assembled” from one or more pieces, the time of concern is how much elapses between when the assembly has reached a reactivity (neutron multiplication factor) of 1.000 and whatever maximum reactivity it could potentially reach in its optimum configuration (that might be a reactivity on the order of 1.2 for a fairly effective bomb).
But regardless of where between 1.000 and 1.2 the reactivity is at any stage of the assembly, nothing happens until the first neutron appears, to trigger the fission chain reaction: Theoretically, if there were never any neutrons around, the 1.2 reactivity configuration could exist indefinitely.
In reality, we know there will be neutrons around, with little time for assembly between them: 0.4 micro-seconds for RGPu and 0.17 seconds for U235.
Now, guesstimating the approximate size of the components and their assembly speed, we can easily see which option has a good chance of succeeding and which doesn’t.
For example, in a U235 gun-type device, the assembly speed might be around 1.5km per second, while for an implosion device (with radially converging shock wave) it might be as much as 6km per second.
Also, for the U235 gun-type device the required travel distance between 1.000 and 1.2 reactivity might be around 10cm, while for the Pu implosion device it might be about 5cm of radial distance.
So, traveling 10cm at 1.5km per second would take 67 micro-seconds, while traveling 5cm at 6km per second would take 8 micro-seconds.
Now divide that into the average time between neutrons, and you get (0.17 ÷ 0.000,067 = ) a factor of 2,540 for U235 assembly, but you get only (0.000,000,4 ÷ 0.000,008 = ) a factor of one-twentieth for RGPu assembly.
Conclusion: The U235 device has ample margin for success, while the RGPu device has none, even with sophisticated implosion assembly.
In fact, the U235 is likely to disintegrate from its peak reactivity configuration before a neutron appears: Consequently electronic devices are required to supply external neutrons, in timing with peak reactivity during assembly.
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Citizendium is not Wikipedia. We don't suppress debate, we allow each side to make their case, in their own words. That is what I meant by "balance", not giving facts and nonsense equal weight. The nonsense appears only on our debate pages, and is easily debunked by our nuclear experts. These discussions allow our readers, mostly journalists, to see that they are not getting only one side of an issue. It is important that we include the nonsense, if it is widely believed. I haven't heard anything about the I-129 problem, but if I do, we will publish both that and Jack's rebuttal.
The debate on whether plutonium can be "spiked" with non-fissile isotopes to avoid the risk of diversion, is one of the few debates that we have not been able to resolve. It comes down to details of weapons design that are classified. On the Yes side we have the articles cited on the design of the ThorCon and the Integral Fast Reactor. On the No side, we have the articles by weapons designers Mark and Garwin, and the statement from the IAEA, which presumably had access to the classified information.
My take is that we will never be able to resolve this debate, and therefore we must do better on diversion control, especially if we are considering deploying thousands of reactors worldwide. But we are getting way off track. Check our article on Nuclear Proliferation. Maybe we can continue this discussion on your Rad Toolbox page.
Thanks for the explanation, David.
I guess that makes sense.
As for “Maybe we can continue this discussion on your Rad Toolbox page”, that would be really off-topic in that group – although I generally don’t delete posts by members, when they go off-topic.
Similarly for my other group, “Communities [interested in] hosting nuclear storage / repository facilities”.
Perhaps you cover that topic as well?
It’s at https://www.facebook.com/groups/122702285266096/
I haven’t thought it important to create a group specifically on the topic of nuclear weapons and proliferation, but when the issue does come up in other forums, I usually cite the US “Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon‐Grade Plutonium Disposition Options”, which is quite clear on Plutonium and is an official statement.
LD50 for potassium iodide in an adult is the ballpark of 0.1 kg. Ten grams causes acute poisoning symptoms. I-129 will kill you chemically before it can irradiate you to death. It isn't a radiological hazard to begin with.
MIT Nuclear Engineering knows that. Why did they not say it?
You know the answer. Fear sells. Easy to score points, and make a buck.
Just finished Robert Zubrin's "merchants of despair". It is a real eye-opener.
So sad that the most potent energy source available to mankind has become ensconced in a seemingly perfectly inert urn of fear, ignorance and politics. How do we turn things around?
Just a side note. You said: "One of the more abundant fission products is iodine-129. " I-129 makes up 0.7% of the fission products. Still, I suppose that means there are kg produced per year per reactor.
I-131 produces 4 billion times more radiation energy than equal quantities of I-129. The only real evidence of harm from I-131 that I am aware of was Chernobyl, when they did not stop kids from consuming highly contaminated food. Some of these kids did get 1Gy and more in the months of their exposure. This would be a few tens of mGy/day. Doses over the same time period from equal amounts of I-129 would be measured in pico-Gy/day. BTW, some of the effects in Belarus/Ukraine were due to the kids having Iodine deficient diets.
Just for fun I asked what if all the I in a thyroid was I-129. A thyroid can only contain about 10^19 I atoms. Imagine that they were all I-129, all the time. There are about 500 trillion seconds in a half life (5* 10^14). That means about 20,000 Bq of low energy radiation.
"More abundant" was misleading. Thanks correction.
It's not the dose. It's the dose rate profile. I know I sound like I'm in a loop, but no matter how many times I repeat that mantra, you guys keep talking about THE dose. The choir seems to be made up of closet LNTers.
At least your last para talks about dose rate.
I was comparing dose/day of I-129 and I-131, so dose rate. Also Bq is per second, so again a rate. So I was entirely talking dose rate
"Radiant energy" sounds like dose to me. Did you mean "radiant power"?
I don't think so. According to my numbers, ingesting a nanogram of I-131all aty once will result in a total dose that is 4.2 billion time larger than ingesting a nanogram of I-129, in agreement with your numbers. But the dose rate profiles
are also quit different in shape. The I-129 DRP will fall off with a half life of about 80 days (teh bio half-life) The I-131 DRP wil fall off with a half-life slightly smaller than 8 days. (teh decay half-life).
It's not just dose rate. That's as bad as it's just dose. It's dose rate profile.
I showed that peak dose rates were pico-Gy/day. I am not worried about dose rate profile in this situation, and you can't consider biological half life when you don't know the rate at which the I-129 is being ingested. I simply showed that no matter how much I-129 is in the environment, it is unlikely to give dose rates above a few pico-Gy/day.
I do acknowledge that I meant Radiation power, not energy
Funny. I asked ChatGPT to compare the risks of I129 with natural iodine and compare dose conversion factors and LD50s for typical iodine compounds.
It proceeded, or rather not, to decide not to answer my question and instead provide a third party link to a suicide call center of some sorts.
Indeed, it is rather worrying to see dairly newspaper articles of kids killing themselves with radioactive iodine compounds stolen from the plutonium reprocessing plant around the corner. What's the world coming to? And this comes after reports of kids doing "toping" with 60000 RPM carbon composite centrifuges doing up high enriched uranium in their treehouses!!
Well as long as the nanny state trumps Skynet we at least don't have to worry about "artificial" intelligence taking over!
May I remind everybody that AI generated content is banned from this site. Regurgitated conventional wisdom falls somewhere between vulgarity and partisan political statements.
who donates the most money to MIT
For the Nuclear Energy Department, it's DOE.
But it's not that simple. I've corresponded with Prof Wainwright on her paper. She honestly believes she has done nuclear power a favor by obliquely questioning deep geologic disposal of I-129. She has been so thoroughly indoctrinated she does not need to be suborned.