Build More Nuke Plants, Part Two

Rob, funny you should mention that. I’ve been talking to Chuck Devore these past few days about exactly the same thing.

Here’s what he said to me about this:

It’s important not to understate the severity of what’s happened in Japan, but also important not to understate the safeguards that have been put in place and how fundamentally different the safeguards that have been put in place in plants in Japan are from Chernobyl in 1986. There was no containment dome in Chernobyl. And there are containment domes in Japan.

And what happens when you get a meltdown or a partial meltdown, as may be happening, is the substances you’re most concerned about–things like strontium and cesium and iodine–because those are elements that are easily picked up by the human body, in the case of strontium and cesium, they’re very similar, chemically, to calcium, so they tend to get absorbed into the bones and can cause bone cancer and leukemia; in the case of iodine it gets taken up by the thyroid gland. But it’s also very easy to combat, and that’s why the Japanese government is distributing the iodine pills, to prevent that.

The important thing, though, is the containment dome itself. And what happens when you have a meltdown, or partial meltdown, is that there’s a fair amount of very hot, as in vaporized, cesium and strontium and iodine that gets released. These are products of nuclear fission, and what’s happening is that these products of nuclear fission are embedded in the concrete of the containment dome. They’re very sticky: They like to seek out and find concrete when they’re at that temperature. And they actually bind with the wall of the containment dome. So even if there’s a partial rupture of the containment dome, which can happen, and there’s a crack in it, the bottom line is these materials are going to coat themselves, in their super-heated state, on the side of the walls of the containment dome. And as long as it functions as it’s supposed to, then the secondary damage–you’ve had the earthquake, and the tsunami–then the likelihood of civilian casualties at these nuclear power plants is actually very limited.

I don’t want to discount it — the bottom line is it’s a serious situation — but let’s look at Chernobyl: according to UN reports in the aftermath, roughly 50 people died at Chernobyl, about half of them being direct responders, people who were putting out the fire, and about half of them being civilians. So this is the worst nuclear power accident in the history of mankind, put that into context of Japan–we may be looking at thousands of people dead from the earthquake and tsunami. So in the greater context of things, this nuclear power plant meltdown is mainly in the minds of Western media as a big deal, when the big deal was the earthquake and tsunami.

Containment domes aren’t my specialty, but he sounded quite persuasive. I’d be curious to hear from other people who know more about this. Does this sound about right to them?  

  1. Claire Berlinski
    C

    Thanks for this, Cool Hand. Between you and Chuck, I’ve been persuaded not to freak out completely. 

  2. Orion

    Nicely done CoolHand.

    Thanks

  3. Stan Hjerleid

     Thanks CoolHand.  Fox News needs to hire you to bring some sanity to the hype.

  4. oddhan

    Thanks, CoolHand. I really think the US media has blown the real story here which is how Japan is handling the response to an immense Earthquake and tsunami. For one thing, none of the recent disasters has hit a nation as advanced and developed as Japan or the US. So I think the US and Europe could learn much from how Japan is coping.

    The nuke plant is a side show by comparison.

  5. Linda Mair

    The post I’ve found with the calmest reporting is at  http://www.mitnse.com They have a modified version of the report from Joseph Oehmen – which went viral earlier in the week – as well as frequent updates and explanations of which ‘Coolhand’ would approve. I do wish the ‘news’ reporters and politicians would do some reading on this website. The ‘chicken little’ specialists on TV after any disaster do a lot of harm with the constant drum beat of fear they try to instill in the public, the net effect of which is to turn people off to the real dangers in their lives. My thanks to Coolhand and to oddhan for adding information of value to the debate.

  6. Rob Long
    C

    Thanks, CoolHand!  Excellent stuff.

    I’m in LA, and I have to report that as of this morning, only the true morons are freaking out.

  7. Talleyrand

    Thanks Coolhand for the concise description above

    A simple question but one I cannot seem to get an answer to; what is producing the Hydrogen gas exactly? Is there some electrical current/charge being created as a byproduct of the nuclear reactions, causing dissociation of water viz a fuel cell? Or is it superheated steam causing water to break down into H2 and O2 gases and then igniting?

    Curious to hear that Sr and Ce etc are sticky in a vapourised state. I am concerned to hear about some of the spent reactor rods being housed in water baths with what appears to be no specific containment vessel holding them. Can this be true, especially if they have Pu products associated with them?

  8. Cas Balicki

    Thank you CoolHand! Excellent post.

  9. CoolHand

    Talleyrand: Thanks Coolhand for the concise description above

    A simple question but one I cannot seem to get an answer to; what is producing the Hydrogen gas exactly? Is there some electrical current/charge being created as a byproduct of the nuclear reactions, causing dissociation of water viz a fuel cell? Or is it superheated steam causing water to break down into H2 and O2 gases and then igniting?

    Curious to hear that Sr and Ce etc are sticky in a vapourised state. I am concerned to hear about some of the spent reactor rods being housed in water baths with what appears to be no specific containment vessel holding them. Can this be true, especially if they have Pu products associated with them? · Mar 17 at 10:44am

    No problem guys, glad to finally be of some use around here.

    To answer your questions in order:

    The hydrogen gas is created via two mechanisms here.  First, at some finite temperature (which I can’t recall off the top of my head, and I’m at the shop right now, so no reference material is handy), the molecules of water will disassociate into free oxygen and free hydrogen.

    Continued . . . 

  10. CoolHand

    Yes.

    There are a number of very well informed folks blogging about this with very level heads.

    Bottom line:  No Chernobyl Redux, no matter what happens.

    The reactors scrammed within seconds of the start of the earthquake, so all this trouble has been in dealing with the residual decay heat (the heat put off by the fission byproducts continuing to decay to their stable forms).

    Once the reaction stops, the chance that the core is going to melt through everything (which is a myth with these kinds of reactors anyway) and then go boom is pretty much zero (it’s not zero, but very very low).

    What they were/are trying to prevent is the core (the fuel rod assemblies and their support structure inside the pressure vessel) overheating and melting.  Even with the reaction stopped, the residual heat for the first few days is enough to melt the fuel assemblies.  That is why they pump water through the core even after shutdown, and that’s the problem they’ve been fighting this whole time.

    Continued . . .

  11. CoolHand

    This is a similar mechanism to electrolysis (not identical, but the results are the same), which is one of the ways that pure hydrogen is manufactured (on purpose).

    Second, when superheated steam reacts with the Zircaloy fuel rod housing, hydrogen gas results as a byproduct.  This only happens if the rods overheat, or if the water level falls enough that the rods emerge out the top of the pool.

    It is likely that both mechanisms in combination are responsible for the hydrogen production at Fukushima.

    Now, about the spent rod pools.

    As I said above, even after the actual fission reaction stops, the byproducts produced by the process are unstable and continue to decay until they find their stable forms (usually as some lower power state, like a non-radioactive version of themselves).  This decay causes a lot of heat.  The heat isn’t as intense as that created by the actual fission process, but still a significant fraction thereof (usually 5%-10% of full power).  However, the byproducts decay quickly (exponentially) and eventually, the fuel will cool to a point where even passive cooling is no longer necessary.

    Continued . . . 

  12. CoolHand

    Once they get the pressure vessels refilled with water and maintain the water level for any length of time (a few days), the whole ordeal will be more or less over.  The waste heat will continue to fall exponentially as the fission byproducts decay away, and the whole mess will stabilize into what they call a “cold shutdown” condition.

    Once cold shutdown is achieved, the situation is stable and will remain so without further intervention.  Then they can start to clean up the mess (and what a mess it is).

    Containment wise, you have several layers in play here.

    The uranium fuel is in the form of cylindrical pellets, which get stacked up and slid into metal tubes (made of some really whiz-bang alloy of zirconium, chromium, iron, nickel, and hafnium).  That’s the first level of containment, the fuel rod assembly.

    Those are then assembled into bundles and put inside the steel reactor pressure vessel.  This assembly is called the core.  The pressure vessel (made from 5″-6″ of tonka tuff steel) is the second level of containment.

    Continued . . .

  13. CoolHand

    This is why the cooling pools are situated near the top of the containment structure, but outside it.

    When being refueled, the spent rods are quickly removed from the core and placed in the adjacent pool to continue cooling to their stable state.

    This allows the refueling process to proceed at a quicker pace, limiting the amount of time that personnel must be inside the structure.

    When the spent rods have finished cooling (after a few days to a few weeks), they are then removed from the pool and sent to secure dry storage elsewhere.

    The problem at Fukushima is that they were in the middle of a refueling and maintenance cycle, so some of the spent fuel pools had rods in them.

    Reactor #4 had all the rods that had been in the core inside the cooling pool so that maintenance could be done inside the pressure vessel.  This fuel was not spent, but merely in a holding pattern while the reactor vessel was being worked on.

    That is why there has been so much concern about the spent fuel pool at reactor #4.

    Continued . . . 

  14. CoolHand

    Inside the pressure vessel is where the cooling water circulates, and in this type of reactor (called a Boiling Water Reactor), where the steam for making power is generated.

    The pressure vessel is then encased inside another steel vessel, called the dry vault.  The dry vault is the third level of containment.

    Below the dry vault, and connected to it by large ducts is the pressure relief or blowdown chamber, a torus (doughnut) shaped chamber half filled with water, where steam from the pressure vessel can be vented to and condensed if necessary to relieve pressure.

    This is where the vented steam has been going when the engineers have bled the reactors for the last several days.  Normally, scrubbers and filters remove any particulates and radioactive isotopes that may be exhausted from this area, but all those systems depend on AC power, and there has been none to be had at the plants since the quake and tsunami.  This is also the structure that is said to be damaged in reactor #2.

    Continued . . .

  15. CoolHand

    Because the rods are still viable, there was some concern that they could go critical in the spent fuel pool and begin to heat up from fission, not just decay heat.

    However, there are many precautions in place that prevent that sort of thing.  First, the geometry of the spent fuel pools is deliberately different from the core, to prevent the attainment of the necessary neutron density to create fission.  In other words, they spread the rods out in such a fashion that the neutrons aren’t happening in a high enough concentration around the fuel to cause a fission reaction.

    Second, the cooling pool water is inoculated with boric acid.  This acid “poisons” the cooling water, preventing fission reactions by absorbing whatever free neutrons are created by the rods naturally.

    And, in some cases (and I don’t know that this is how they do things in Fukushima), the spent fuel pool will be segregated into several separate wells where the fuel rods can be shielded from one another.  These partitions are usually made from a boron impregnated material such that they just absorb any free neutrons they happen to encounter.

    Continued . . . 

  16. CoolHand

    Inside the dry vault, there is another structure, made from graphite impregnated concrete (shaped like a tall open topped drinking glass) inside which the reactor pressure vessel rests.  This structure is called the biological shield, and is meant to catch the entire contents of the pressure vessel, should the entire mass simply turn liquid (it won’t, but just in case, this concrete drinking glass is there to catch and contain it).

    The biological shield is the fourth level of containment (or the third, since it’s actually inside the dry vault, but whatever).

    Outside all of that, encasing the entire menagerie I just described, is eight more feet of steel reinforced concrete, called the outer containment structure.

    The outer containment structure is the fifth and final level of containment.

    Outside that structure is a steel girder and sheet metal building, whose sole function is to keep the weather off the containment structure.  This building is what has filled with hydrogen gas (disassociated by the high heat in the core, and vented into the blowdown chambers, and subsequently into the weather cover building) and blown up.

    That about covers it, for now anyway.

    Hope it helps.

  17. CoolHand

    Now, that all said, if the water drains away from those rods, during the portion of their decay heat cycle where they still require active cooling, they will melt.

    This is obviously bad.

    What we don’t know how long the rods were in the pool, and how hot they were when the disaster struck.  If they’d been in there a few days to a couple of weeks already, they are likely cool enough already to survive being left in the pool with no active cooling for a while.  If they just took them out the day of the quake, then they’ll be as hot as they could be, and will require the active circulation of the cooling water to prevent boiling the pool dry.

    Unfortunately, I’ve not heard anything about when the rods were actually extracted from the #4 core.

    I did read yesterday evening that TEPCO reports the water temperature in the spent fuel pool of reactor #4 as ~85º C.

    Continued . . .

  18. CoolHand

    The bit above about the core running away and melting through everything being a myth with this type of reactor goes like this:

    In order for fission to occur, the neutron has to hit a uranium nucleus and cause it to split.  This is a lot harder to do than you’d think, seeing as how atoms are mostly open space, it’s pretty easy to miss, and those neutrons are going mighty fast, so there’s not a lot of residence time inside the uranium or the core itself for them to hit another atom.  The probability of a collision is low, and fission doesn’t happen.

    In order to increase this probability, a moderator is introduced to slow the neutrons down and give them a little more time inside the core in which to find a uranium atom to run into.

    Here is where the big difference between our (the west’s) reactors, and the old Soviet reactors comes in.

    Our reactors use water (called light water, ’cause heavy water is something totally different) as the moderator, as well as for cooling.  If you remove the water, the fission reaction stops.

    Continued . . .

  19. CoolHand

    That is below boiling, even five or six days after the loss of active coolant circulation, which tells me that the rods had been in the pool for some time before things went all pear shaped, so their temperature had been reduced quite a lot before the cooling water stopped circulating.

    That’s what it looks like to me, BUT I MUST STRESS THAT I DO NOT KNOW THAT FOR SURE TO BE THE CASE.

    Those are the best answers I have for you.

    Hope it helps.

    For more up to date information, go check out the Brave New Climate blog.

    They are a hard core Global Warmist site, but on this particular front, they are very level headed and are bringing to the table some very good information.

    The above link is to their update for today, which is almost entirely devoted to the topic of the spent fuel pools and what is going on with them.

    It’s worth the read.

  20. CoolHand

    In fact, the hotter the core gets, the slower the reaction gets, such that it partially self regulates.  This is called negative feedback, and it’s the reason why light water reactors don’t run away.

    No matter what, these kinds of reactors cannot run away and melt through the earth.  However, if you remove the water, the core will still melt from decay heat, even though the actual reaction has stopped.  If the absolute worst happens and the core melts, the goop will set in one of the myriad containment structures I outlined above until the decay heat has subsided, and then it’ll solidify into a big block of useless (radioactive) lava that can be disposed of.

    The old Soviet reactors (like those used at Chernobyl) used solid graphite as the moderator.  Two things to note here.  First, the graphite is always present, so the reaction will continue so long as a sufficient mass of fuel exists to provide neutrons.  Second, graphite burns if you get it hot enough.

    Continued . . .

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