rtrapasso -> RE: OT: Massive 8.9 quake in northern Japan (3/21/2011 1:48:36 PM)
|
quote:
ORIGINAL: ncdawg quote:
ORIGINAL: Cap Mandrake quote:
ORIGINAL: ncdawg Actually, during an accident the majority of the hydrogen production isn't from the disassociation of water, it's caused by the "zirc-water" reaction between the zircalloy cladding of the fuel rods and water (or steam). When the zircalloy cladding reaches approximately 2200 deg-F, it undergoes an exothermic reaction with water creating zirconium dioxide and hydrogen. Due to the hydrogen explosion inside the containment at Three Mile Island, all U.S. PWRs (and maybe the newer BWRs ?) have been required to install hydrogen recombiners or hydrogen burners inside containment. For the older BWRs with the "light-bulb and torus" type containments, hydrogen recombiners are not required. These older BWRs have a hardened & filtered vent that runs between the wetwell region of the containment & the plant stack. My guess is that the hydrogen explosions seen at Fukushima were due to zirc-water reactions in the spent fuel pools (this is definitely what happened at Fukushima 4, since there was no fuel in the number 4 reactor). That (the reaction between the fuel rod zircalloy and the steam) is the explanation given at the MIT site. Certainly, as the pools are not pressurized, doesn't the presence of that much hydrogen prove that the spent fuel rods were at least partly uncovered and hot as hell? How else could it reach 2200 deg F? As for pumping water to the SFR pools, we were told the backup diesels were wrecked by the tsunami and the battery backup gave up at about 8 hrs. Since there was no fuel in the Unit 4 reactor, the hydrogen had to come from the Unit 4 spent fuel pool. So yes, the fuel in the Unit 4 spent fuel pool must have been uncovered. The link listed below gives updates on the status of the Fukushima reactors updated several times daily. I have found this link to be the best source of information (the reports from the news media have been utterly useless). Even better, this site is in English (sort of)! http://www.jaif.or.jp/english/ This is the whole rationale of them using the fire hose cannons and air drops on no. 4 reactor: the cooling pool is essentially empty, and they are trying to refill it from above. Per prior posts, the fuel rods had been reported as "glowing red" from satellite, so they are visible from above. Of course, since the pool has essentially been ruptured, they can only attempt to cool down the rods by continually dumping water on them. Eventually, if they are going to prevent a meltdown of the spent fuel rods in the cooling pools, they are going to have to either fix the leaks (good luck), move the rods, or entomb them in something that won't run out. IIRC, the Russians used a mixture of sand and boric acid dumped into burning radioactive material to damp down the reaction. Maybe something similar could be used.
|
|
|
|