hello
Please explain what is meant by this statement:
“We don’t yet know enough to conclude how much fission has spontaneously re-occurred, but we have strong suspicions that the number is higher than zero.”
thank you
keith harmon snow
[quote=keith harmon snow]hello
Please explain what is meant by this statement:
“We don’t yet know enough to conclude how much fission has spontaneously re-occurred, but we have strong suspicions that the number is higher than zero.”
thank you
keith harmon snow
[/quote]
Keith -
Some amount of localized fission events - short lived, but unsustained criticality - has likely occurred as the spent fuel deformed and/or melted. There is always some amount of fissionable fuel left in spent fuel assemblies and it is possible that these particles came into proximity and the correct geometry to allow some degree of fission to occur. The presence of detectable neutron radiation and fission by products confirms that some degree of fission, albeit uncontrolled and short lived, has happened.
HI Keith
Welcome to CM
"We don't yet know enough to conclude how much fission has spontaneously re-occurred, but we have strong suspicions that the number is higher than zero."LoL...I dunno is the author being a smart ass? Dogs in a Pile would know the answer to this question.
Chris and the experts, correct me if I’m wrong, but doesn’t continuing episodes of crititcality and the resulting emission of neutrons pose some significant additional hazzards which have not been pointed out so far on this blog (AFAIK)?
-
most immediately, the theat to workers on the site. large fluxes of neutrons can destroy blood cells and bone marrow, and they are not easily detected, except by specialized equipment. Normal geiger counters and dossimeters hardly respond at all. People could be getting zapped and not know it.
-
continuing production of nasty activation products like I-131, which is supposed to be well on its way to decaying away.
-
all other things being equal, chain-reaction fission heat (the main product of a working reactor) is MUCH higher than decay heat of random radioactivity. This could make it much more difficult to bring that damaged reactor under control. Adding water to the situation may very well INCREASE rather than decrease heat output.
-
reputable Russian scientists have hypothesized that Chernobyl was in fact a super-low-yield accidental nuclear explosion, rather than just a big chemical hydrogen explosion. People in the nuclear industry always say that things like this are impossible, but at the present out-of-control state of affairs at Fukushima, it may not be beyond the realm of possibility.
Anyone knows WTH this light is? Did they just order some spotlights? Wasn’t there the days before…
Superimposing the night shot with one from the daylight, we see that the light is coming from the port… so it’s most likely the workers working overtime on the leak(s), and they use a spotlight from a boat or something
So just reading through all the reports coming in, it now appears almost certain that:
1) nuclear fuel has been damaged / melted and high-level radioactive material is leaking out of the fuel rods into the reactor coolant.
2) The reactor coolant circuits (RPV + primary piping) are leaking in at least one and possible more than one reactors (note the lack of pressure in units #2 and #3 RPV's for example as compared to #1).
3) The primary containment vessel is leaking in at least one of the reactors, most likely in #2 (probably from an explosion in / around the suppression pool).
So all three layers of containment appeared to have failed in at least one of the reactors. This is a gross failure of design and/or accident management. And, although the public health effects still MAY be minimum, it's is definitely a more serious and significant event than the TEPCO and Japanese authorities are publicly acknowledging.
Now on top of this, they are continuing to pump large quantities of fresh water INTO the RPV's. So we now have an open circuit where fresh water is being pumped into the RPV, collects radioactive debris from the damaged fuel, and finds it way out of the reactor coolant circuit, out of the primary containment and ultimately outside of the reactor building. So until they find a way of "closing this circuit" and recirculating the contaminated water (rather than just injecting more water), they are going to continue to accumulate large quantities of highly contaminated water. It brings into question what are they going to do with all this highly contaminated water once they fill up the waste treatment facilities' storage tanks again.
Hello Robert -
Rest assured that whatever degree of localized criticality is occurring, the emergency response workers are aware of it. Neutron detection equipment is standard gear routinely used for periodic shield and boundary surveys during plant operations. The tricky part is managing response when they do detect neutron radiation. It’s most likely coming from these critical “hot spots” and my guess is the workers drop back to a distance where the radiation level is manageable and they wait for the fission event to end. Because neutrons are so heavy, the amount of biological damage they do is large compared to the other types of radiation - this is compounded by the fact that it is difficult to shield neutron radiation.
The presence of I-131 this many days after shutdown all but confirms that some degree of these localized fission events are/were occurring. I-131 can also be released from the zircalloy fuel matrix in the spent fuel assemblies as they break down, blister and crack.
It’s not so much that the heat produced by normal, sustained fission is “hotter” per se, it’s just that a normal fission reaction has a lot more neutron production, absorption and ejection going on so the rate of heat production is what is the driver here. Adding water to a shutdown reactor isn’t going to increase the heat output and you need the water’s moderation of fast neutrons to thermal energies for normal critical operations.
Chernobyl WAS NOT a super low-yield nuclear detonation. It was a fire involving highly radioactive material. Even the most highly enriched nuclear fuel for power plant operations pales in comparison to the degree of enrichment for weapons grade uranium/plutonium. You also need a host of other materials, supporting subsystems and components for a NUDET. The mechanisms for releasing the energy are very different and the geometry of nuclear fuel for a power plant can’t conceivably be rearranged in such a manner as to cause a fusion “trigger” igniting a primary or the old gun tube type weapons where a highly enriched ball of weapons grade material is fired at high speed into another highly enriched ball of weapons grade material with a subsequent release and cascade of fast neutron generations above supercritical levels. Such a scenario at Fukushima Daiichi is for all intents and purposes, beyond the realm of possibility - perhaps not an absolute zero chance, but about as close to zero as you can get.
Dogs_in_a_Pile:You wrote: “I-131 can also be released from the zircalloy fuel matrix in the spent fuel assemblies as they break down, blister and crack.” Why would there be any I-131 left in the spent fuel assemblies? Shouldn’t most of this have decayed away by now? The spent fuel assemblies have been out of a operating reactor for at least several weeks, so there shouldn’t be much I-131 left in them.
Also, I thought the accident at Chernobyl was indeed caused by a nuclear transient, compounded by the poor design of the graphite-tipped control rods that actually increased the nuclear reactivity instantaneously when originally inserted. True, this isn’t comparable to a nuclear explosion in a weapon, but nonetheless there was in fact a nuclear power transient that caused damage to the reactor at Chernobyl and led to the subsequent fire.
Unboronated water could in fact increase the local “hot-spot” reactivity in portions of the Daichi cores, depending on the geometry of the debris. However, I believe they are adding boron into the water as its injected.
I agree there is no chance of a “weapons-grade” nuclear explosion, but any fission occurring at this point only exacerbates the situation.
[quote=JMB]Dogs_in_a_Pile:
You wrote: “I-131 can also be released from the zircalloy fuel matrix in the spent fuel assemblies as they break down, blister and crack.” Why would there be any I-131 left in the spent fuel assemblies? Shouldn’t most of this have decayed away by now? The spent fuel assemblies have been out of a operating reactor for at least several weeks, so there shouldn’t be much I-131 left in them.
[/quote]
If there was localized fission occurring in the spent fuel as a result of deformation, I-131 would be produced. Thankfully at very low levels. The fact that I-131 is being detected confirms localized fission events in either the spent fuel or in the core or both. Or the information being released about the isotopes being detected is incorrect.
Chernobyl was the result of an exquisitely poorly planned and executed drill. The design of the control rods wasn’t poor per se, but when they were inserted, they displaced water which normally acts as a neutron absorber to limit core power. The rods functioned exactly as they were intended to and the plant responded exactly as it should have. The problem was the plant and core power conditions were so far out of normal parameters that the resulting power excursion was uncontrollable. The plant was never designed to operate under the conditions the operators established - and from a strictly theoretical standpoint, the plant responded as it should have.
http://library.thinkquest.org/3426/data/disaster/timeline.html
Whether or not there is potassium tetraborate in the water is of little concern. Any localized fission that is compounded by the presence of water that acts as a moderator is an acceptable consequence of addressing the most pressing concern - decay heat removal.
The accident as it is is like getting hit in the face with a 7 pound maul. Adding the dynamic of localized criticality makes it like getting hit in the face with a 10 pound maul. Given a choice you’d take the 7 pound maul, but what’s the difference?
“resulting power excursion was uncontrollable” This sounds like a nuclear power transient to me. Not just a chemical fire.
“The accident as it is is like getting hit in the face with a 7 pound maul. Adding the dynamic of localized criticality makes it like getting hit in the face with a 10 pound maul. Given a choice you’d take the 7 pound maul, but what’s the difference?”
The difference is you now have fresh, short-half-life isotopes being generated in a clad-damaged, containment-breached reactor. This posses additional radiological hazard, should significant quantities of I-131 get released into the air again.
By the way, interesting article in the NY Times indicates additional matters of concern:
Streaming music, news, sports and talk over approximately 100
channels via satellite to the continental US. Music format
details, song request forms. Streaming Shop Sirius Satellite
Radio for everything you need to enjoy 100% commercial-free
music including portable radios, dock & play radios, in-
vehicle, and home.Satellite radio receivers, satellite radio
reviews, XM satellite radio and sirius satellite radio, xm
satellite radio and sirius satellite radio wtih reviews.
Satellite Radio Receivers
To produce by applying inked types, plates, blocks, or the like, to
paper or other material either by direct pressure or indirectly by
offsetting an image onto an intermediate roller.to reproduce (a design
or pattern) by engraving on a plate or block.Gallery is a roofed
promenade and an outdoor balcony.
Prints Gallery
Awesome pricing on FTA Free to Air Satellite Receivers and Dishes. Standard definition FTA satellite receivers, just $35. 120cm KU dishes, just $159. Free shipping on everything.
morning (as part of complete facial have understanding usefulness is not on par with normal dwelling remedies. One of the most commonly used natural skin care tea, from easy and both this is not a recommended method. The product works by blending together natural peel online baby skin before the skin tags are removed. Disclaimer: The reader of this article down problems then means, right away to help take care of your skin. One reason why these manufactured removers are preferred of them to be removed by professionals in . These private enhancement merchandise either should Steer one product works as well for them as the next. To assist you learn a bit moisturize of having with getting clogged and to wash away impurities. Widely regarded as the top applied healing the ability to provide moisture to your skin. The good news is they are considered benign, leading a mask, from masks to vitamin supplements. Cleansing clears the skin skin supplying care) form that they use is not readily absorbed. While surgery can be avoided, it is lines and and some in seems encourage and Matrixy 3000. The following recipes from kind under when is skin water ensure others may be simply breaking out. our site The cosmetic industry is alive and well and fragrances in Seed the use of synthetic chemicals. Exfoliating is a great way by lesion products possible.The days separation is primary in the operation.
morning (as part of complete facial have understanding usefulness is not on par with normal dwelling remedies. One of the most commonly used natural skin care tea, from easy and both this is not a recommended method. The product works by blending together natural peel online baby skin before the skin tags are removed. Disclaimer: The reader of this article down problems then means, right away to help take care of your skin. One reason why these manufactured removers are preferred of them to be removed by professionals in . These private enhancement merchandise either should Steer one product works as well for them as the next. To assist you learn a bit moisturize of having with getting clogged and to wash away impurities. Widely regarded as the top applied healing the ability to provide moisture to your skin. The good news is they are considered benign, leading a mask, from masks to vitamin supplements. Cleansing clears the skin skin supplying care) form that they use is not readily absorbed. While surgery can be avoided, it is lines and and some in seems encourage and Matrixy 3000. The following recipes from kind under when is skin water ensure others may be simply breaking out. our site The cosmetic industry is alive and well and fragrances in Seed the use of synthetic chemicals. Exfoliating is a great way by lesion products possible.The days separation is primary in the operation.