Fake Banner
    Japan's Nuclear Tragedy - Is A Solution Close At Hand?
    By Richard Mankiewicz | March 16th 2011 11:00 AM | 5 comments | Print | E-mail | Track Comments
    More Articles
    All Articles
    About Richard

    I used to be lots of things, but all people see now is a red man. The universe has gifted me a rare autoimmune skin condition known as erythroderma...

    View Richard's Profile
    South Korea has agreed to send some 50 tons of boron from its reserves to Japan to help fight the nuclear disaster at the Fukushima reactor plant.

    The scientists at TEPCO have been sent samples for analysis and a decision should be made pretty quickly. [Reuters, Korea Herald]

    However, this seems to have been lightly reported and I blog this here more in the hope of an answer to a niggling question I've had since the start of this tragedy. Why have the operators at Fukushima not used boron carbide to absorb neutrons rather than boric acid? It seems as if, for whatever reasons, liquid boron is liable to evaporate along with the water.

    Boron carbide is already used for the control rods and some reactor designs have ball-bearings that can be dumped into the core in case the rods are not functioning. The initial idea of using boric acid seemed fine at the time but obviously isn't working and TEPCO have run out of stocks.

    So, I'm not sure if the boron that may be coming from Korea is in metallic or liquid form. I studied nuclear reactors many years ago - indeed even then the BWR looked like a cheap shoddy design - so if my idea of using boron carbide is dumb, feel free to shoot it down.

    In either case, a solution may be at hand.

    Comments

    Getting boron from South Korea would be time consuming. My understanding is that there is an immediate need to get water onto the spent fuel rods. Helicopters aren't an option because of the radiation plume. Do they have any blimps/ airships that could be moored with cables and used as unmanned water delivery vehicles?
    Sorry, it's not exactly on the thread but I saw your blog looking for solutions....

    John Simpson, NZ (not verified) | 03/16/11 | 16:24 PM
    vongehr
    Boron solids would just fall onto the ground and be useless. Boric acid (H3BO3) solves especially well in hot water. This means it automatically goes to the hot places where it is needed to capture thermal neutrons. Around 170 C, it dehydrates into metaboric acid (HBO2 + H2O). Above 300 C, it turns into tetraboric acid (H2B4O7). Sure, at some point it will evaporate, but as long as (clean, acidic) water is added, it stays mostly around where it is needed.
    Sascha Vongehr | 03/16/11 | 23:46 PM
    rychardemanne
    Thanks Sascha
    but some reactor designs use boron pellets specifically to shut down a reactor. I don't understand what you mean by they'd just "fall onto the ground." I meant pushing them into the reactors and into the spent fuel pools (smart idea having the spent fuel right next to the reactor core!)

    Wikipedia updates mention boron pellets and carbide and yet their reference links don't... much... except that the French have already sent 95 tons of the stuff. Yet again, unclear if in solid or liquid form.

    An article here on how fragile the control rods are in many of Japan's BWRs - published in 2006 but relevant in that there were news snippets of the control rod lights indicating that some had stuck. Just adds to the feeling that the geometry of these cores has been compromised.
    Richard Mankiewicz | 03/18/11 | 12:28 PM
    vongehr
    You mean using a vast quantity of small pellets so that the whole whoosh basically behaves like a fluid and swamps the whole reactor (core should also be fully breached then, as you would not be able to pour your pellet "fluid" through the pumps or mere cracks) and spent fuel pools filling it all up until the last rod is covered. Thats a heck of a lot of boron and helicopters dumping it and after that, all you can do further is basically making a concrete dome over it and have another monument to human fail thats gonna be there for forever. I do not think this idea is all that good or even doable.
    Sascha Vongehr | 03/19/11 | 00:40 AM
    Samshive
    Everyone, the problem at Japan is not about keeping the reactors sub-critical. The Reactors will NOT go critical again because the control rods are inserted. 
    There is a very slight risk of criticality at the Spent Fuel Pools. But the main risk here is indirect. Criticality in the Spent Fuel Pools would be a local event (not all the rods will become critical - and only a small part of the rod will achieve criticality). If it occurs in the Spent Fuel, it could heat up the water further - exposing the fuel rods and subjecting the environment to higher levels of radiation.  Also, the rod would not remain critical for very long due to the negative feedback as temperature increases in fuel. You of course want to avoid criticality in all but controlled circumstances (like in the reactor), but if it does occur in the Spent Fuel Pool, you would not get a Chernobyl like event - the worst case scenario would be that the water in the pool would be depleted and some of the fuel would melt and huge amount of radiation will be released, but there would be no explosion in the fuel.
    Siju Mammen | 03/19/11 | 02:20 AM