Good news and bad news, mostly just uncertain news. A cable needed to power equipment has been installed. It turns out that one of the reactors uses Plutonium. Ooops.
Cable reaches Japan nuclear plant
Fukushima on Thursday: Prospects starting to look good 'Worst probably over'
The story of the quake- and tsunami-stricken Fukushima Daiichi nuclear powerplant continues to unfold, with reports suggesting that the situation with respect to the three damaged reactors at the plant may soon be stabilised without serious consequences. The focus of attention has now moved to problems at a pool used to keep spent fuel rods cool. There remain no indications that anyone has yet suffered any radiation health effects, and the prospect is growing that this will remain the case.
Engineers at Japan's stricken Fukushima nuclear power plant have successfully connected a power line to reactor 2, the UN's nuclear watchdog reports.
Restoring power should enable engineers to restart the pumps which send coolant over the reactor.
emergency workers focused their efforts on the storage pool at reactor 3, the only unit at the site that runs on mixed oxide fuel, which contains reclaimed plutonium. The strategy appeared to conflict with comments made by US nuclear officials and Sir John Beddington, the UK government's chief science adviser, who are most concerned about the storage pool at reactor 4, which they say is now completely empty.
"The water is pretty much gone," Beddington said, adding that storage pools at reactors 5 and 6 were leaking. "We are extremely worried about that. The reason we are worried is that there is a substantial volume of material there and this, once it's open to the air and starting to heat up, can start to emit significant amounts of radiation."
All of the fuel rods in all of the other reactors are made essentially of uranium with a zirconium cladding to seal in radioactive emissions. Reactor 4 uses something different. Its fuel rod are only 94% uranium, with 6% plutonium stirred in and then the same zirconium shell. This mixed oxide (hence the MOX moniker) formulation has one advantage--and a number of disadvantages.
The advantage--no surprise--is money. Plutonium is a natural byproduct of radioactive decay and spent fuel rods are thus full of the stuff. You can always put them into long term storage for a few dozen millennia--which is where most spent rods have to go-but you can also reprocess some of the waste and combine it with pricier uranium for a cheaper and still energy-intensive rod. With nuclear power still more expensive than fossil fuels like coal, manufacturers need to save where they can to remain competitive, and MOX is a good budget cutter.
But MOX is also temperamental. Physicist Arjun Makhijani, president of the Institute for Energy and Environmental Research in Takma Park, MD., spoke to TIME earlier in the week and heaped scorn on the Mark 1 reactors used at the Daiichi site. His criticism in that conversation was the comparatively flimsy (by nuclear reactor standards at least) containment vessels used in the Mark 1s. But he's no fan of the use of MOX either.
Finally, here's the latest areal footage from the site:
For more information and essays about the Earthquake, Tsunami and Nuclear Reactor problems in Japan CLICK HERE.
I'm still not getting over the fact that they're storing the spent fuel rods in something that's esentially an indoor swimmingpool.
Unless the world and I have had bad info these last 6 days, the MOX fuel is used in Daiichi reactor no. 3, not 4 as reported here by TIME. That's why the water spraying operations have focused there instead of on 4 (even though it is likely that the spent fuel pool in no.4 is entirely water free.)
I can't see the video, but if the MOX is near the end of its life, the plutonium is (probably) mostly fissioned away. Plutonium is a biproduct of fission. U238 absorbs a neutron, becomes U239 then Np239 then Pu239.
The U they use in MOX is probably depleted U238 which is cheap. That is the same depleted uranium used in anti-tank rounds because it is so dense (and pyrophoric when it goes through armor).
All reactors that use U238 in their fuel end up with Pu in their spent fuel. The danger from spent fuel is not from the Pu, it is from the fission products.
Chernobyl was a breeding reactor designed to make plutonium for Soviet weapons. The design was modified to generate power plus make plutonium. That was why Chernobyl used graphite as a moderator. When a neutron hits a nucleus, it recoils depositing some of its energy. Because mass and energy both are conserved, the âbestâ moderator would be something that has the same mass as a neutron, a proton. When there are lots of protons around (as in a water moderated reactor), the water is the moderator the neutrons slow down really fast (they start out at a couple MeV). The cross-section for fission is a pretty strong function of neutron energy, slower works better. In light water reactors, the design philosophy is to make the reactivity of the core âstableâ, which means if it gets hot from too much fission, you want the reactivity to go down. That is how these reactors were designed, when water in them boils, it generates a void, the void has fewer protons in it, the neutrons don't slow down as much, fewer neutrons cause fission, the number of fissions goes down.
All breeder reactors use something other than hydrogen as a moderator. The Candu reactors use deuterium and natural uranium. Chernobyl and Sellafield used graphite. Fermi 1 which melted down and the Clinch River Breeder reactor used liquid sodium.
The âproblemâ with using plutonium in reactors is that plutonium is really easy to make nuclear weapons from. Trivially easy because in fresh fuel, there are no nasty fission products to deal with. That âproblemâ is only present before the fuel is put into a reactor. After a few minutes, the fuel becomes intensely radioactive (from the fission products). I think that as a rule, any MOX should be irradiated with neutrons before it leaves the fuel factory so it is intensely radioactive and can't be picked up bare handed without lethal radiation exposure. That does increase the exposure risk for workers, but reduces the chance of diversion to weapons.
This is the entire problem with fuel reprocessing (done properly). All the processes were developed to recover plutonium for weapons, so they produce plutonium that is free from everything ânastyâ. All those ânastyâ things in there make it harder to make weapons from. The transuranics especially are difficult to remove, but essential to do so for weapons production because they have high levels of spontaneous fission, so there are always lots of neutrons floating around. That makes is a lot harder to get the supercritical Pu assembly that you need to get a good yield from a nuclear weapon. Leave those transuranics in the Pu you recycle for fuel and the fuel is somewhat safer and easier to use. You want a lot of neutrons floating around your core when you start it up.
There are 3 main isotopes of Pu that result from U238. They are Pu239, Pu240 and Pu241. Pu239 is the most desired for weapons, the others are much less desirable because they have high spontaneous fission rates. The longer Pu239 is in a reactor, the more of it becomes Pu240 and Pu241 and the crappier it is for making weapons. That is why Chernobyl was designed to be refueled while it was still running. They could put U238 in, irradiate it, take it out and reprocess it for Pu239 before it had built up much Pu240. As fuel in power reactors, they are essentially the same. Pu240 and Pu241 have much shorter half lives than does Pu239.
daedalus2u, according to what I read, this is Plutonium added to the Uranium ... about 20 percent by mass ... not a fission product of the uranium. I can't vouch that what I read was accurate, but that's what it said (I think it was the Guardian article linked in my lates news post ... number 4)
The IAEA has "clarified" their statement on the power cord:
"Japan Earthquake Update (17 March 2011, 16:55 UTC) - CLARIFIED
Japanese authorities have informed the IAEA that engineers were able to lay an external grid power line cable to Unit 2. The operation was completed at 08:30 UTC. "
So much for good news...
Haha, sorry - it seems I inadvertently discovered the secret code for removing text (<>).
"Were able" was clarified to "have begun", and "The operation was completed at 08:30 UTC." was clarified to "The operation was continuing as of 20:30 UTC, Tokyo Electric Power Company officials told the Nuclear and Industrial Safety Agency."
Good news: They have a diesel generator on the site
Bad news: it's on reactor 5 & 6, where the problems are less severe.
More bad news:
They didn't proceed with the power lines as planned but had to stop
Still more bad news: Hydrogen over reactor 4
You can get a short, decent description of how MOX is used (as well as great updates about what is happening from a nuclear engineer) here:
Actually, as my nuclear engineer dad explains ALL fuel rods contain plutonium because of radioactive decay.
The MOX fuel use is recent, but he also points out that only some of the fuel rods in the reactor are MOX.
Evelyn, yes, that is what I said, repeating what was reported from Japan, and it was quite clear until the issue was badly obscured. Thanks for the link.
Oh my god. What a day it was. I will pray to god. That day should not be happen again.