The Mudcat Café TM
Thread #136314   Message #3112487
Posted By: josepp
12-Mar-11 - 02:03 PM
Thread Name: BS: Japan Nuclear plant disaster, 2011
Subject: RE: BS: Nuclear plant disaster looming
////As someone who has "worked in" nuclear power plants, you have never heard of "fuel rods"?////

No. I've heard of fuel plates. These have to arranged in a very specific way inside the reactor. The rods are made of hafnium and when they are inserted, they absorb the neutrons that cause fission thereby squelching the fission process which, it turn, shuts down the reactor if the all the rods are fully inserted simultaneously, i.e. a reactor scram. But even the shutdown has to be carefully monitored for some 30 hours or so due to what is called a build up of "poisons". Now, I haven't worked in a nuclear plant since the 80s and so there might be new designs but I haven't heard of any until now.

////What was your job there?////

I ran the electric plant.

////(sputter, sputter) The nuclear fuel is composed as cylindrical pellets, inserted into nickel alloy fuel rod and then with its brothers and sisters installed within the reactor vessel///

As I said, that may be a new design but every plant I worked in used fuel plates. These plates are very thin. Pellets? You're sure about that? The plates have to be very, very thin. You can't just have a big glob of fission material. And then they're encased in nickel, you say? How does the moderator get to them? What is the moderator?? Maybe they've had some technological breakthroughs since the 80s. First time I've heard of it though.

The rods I know of were hafnium and were necessary to control the rate of fission. I know of one plant that used water instead of rods but I never worked there and am not sure how that worked (I knew several people that did work there).

///The steam would be generated from the coolant heated by the reaction taking place within the fuel rods.///

But how is the reaction taking place, that's what puzzles me. You have to have a moderator and I don't know what that would be in the case of pellets encased in nickel. How are the neutrons getting to the fuel to trigger the fission??? Then the moderator heats up and then is carried along via huge pumps to a set of tubes into what is called a pressurizer which is heated by steam. There is water surrounding the tubes and the heat is transferred to this water of what is called the secondary. This is the water that becomes steam that powers the turbines that turned my generators. That can't let the primary water do that because, obviously, it's been inside the reactor.

////You're correct that an atomic explosion as with a bomb would be unlikely at this nuclear reactor.////

It would be impossible. It would be like two cars colliding into the shape of a huge cannon and balls and the chemicals in the cars' various systems forming a volatile substance that causes the cannon to go off and blow down a building or two. It's literally that remote of a possibility.

///What happened at Chernobyl, however, was bad enough to be "alarmed" at, don't you think?////

Yes, but you're talking about the Russians. Who would you trust to build a better plant? The Russians or the Japanese? I'm not saying this isn't a catastrophe athat can't get worse. An 8.9 earthquake? God knows what is still waiting to happen. But I am saying there won't be any nuclear explosions unless someone sets off a nuclear bomb.

////There the nuclear fuel rods melted down, caught fire, and there was a plume of highly radioactive gas which devastated the surrounding downwind area, and dispersed radiation worldwide.////

How could a cloud of gas disperse radiation? Radioactivty I could see. I mean, I suppose there might be ways but none I know of offhand.

I've never read about what caused the Chernobyl disaster but I would assume if the "fuel rods" melted it would less of a catastrophe than if the hafnium rods melted thereby not allowing the reactor to shutdown so that the fission rate balloons out of control.

///You say that is "unlikely to happen" with a 40 year old Japanese nuclear reactor./////

I'm saying it can't happen. A nuclear plant, no matter how old it is, cannot cause a nuclear explosion because it is not set up like a nuclear bomb. A meltdown is not a nuclear explosion.

////I don't think anyone should be reassured by your statement. But I could be wrong. I hope so.////

You have to be wrong or all my training was bullshit. I'm not saying a meltdown can't happen and wouldn't be catastrophe but I am saying a nuclear explosion simply cannot happen in a nuclear plant unless someone sets off a nuclear bomb inside it.