Or rural Queensland.

I'd be considered a catch.

Actually, no I haven't - I'm not in the nuclear industry any more, and when I was I was on the fuel processing side of things.

I will have a trawl around though, and see what I can find...


S

If the guys at the plant have been there from the start and getting, on average, 1 millisievert an hour, then they are probably feeling a bit sick by this point. A dose of a 1000 millisieverts and you are going to be very ill. 10,000 and you're dead.

Chest x-Ray is about 2 millisieverts

There are a number of sources around, but it's the change from reporting in microsieverts to millisieverts - and the admission that the spent fuel pool is holed that's a signal things have got a whole lot worse. That's inside containment on reactor no. 2.

Couple that with Murphy's law, the wind swinging round at exactly the wrong moment.

No I don't work in the nuclear industry, just a Physicist.

If you can find out how to get eyes in the back of your head then put me down for a couple - could do with them for monitoring my three year old

Don't your patients object to you typing on here during their appointments?

Mine came as standard after having First Born, then fitted with new, improved lenses when Tiddler arrived.

Cough

http://en.wikipedia.org/wiki/Physicist

Just a Physicist? That's something you should be proud of!


S

You should see a doctor about that.



Sorry. forgot, you are a doctor.

There you go.

Oh I am, it's one of my hats. However, most don't really have a clue what one is......

And I know a fair amount about how fission stations work, I've managed to stay out of getting wrapped up in all that business.

Your handy radiation guide:
http://twitpic.com/49mm4l

Has a way to go before it gets Chernobylly.

Wow, I get back from site and this thread has gone Nuclear LOL

To answer some of the questions raised....

No, I dont work in the nuclear industry any more.

Current doses for nuclear workers vary depending on what country you are talking about but are generally accepted to be around 50mSe per annum.

It is possible to take those doses and higher in a shorter period of time and still be OK as long as you are chemical cleaned afterwards. I have and I'm still here but have to say chemical cleaning is probably the most degrading process a human will ever have to go through, but if done in time will negate the effects of higher doses (up to a point). There are certain levels that its just not possible to clean a person from and radiation sickness is unstoppable.

Having been part of an emergency team dealing with an "incident", I know that what happens on the ground and what the media report are 2 completely different stories. I still shake my head sometimes and have a little giggle to myself about the things the media reported during that event.

As to the reason, why the teams from other countries are only now being called in - well there are certain protocols that need to be gone through when nuclear is involved. My guess would be those teams have been on standby at the request of the Japanese govt since day 1 or maybe day 2, but a Nuclear incident is not something the teams will just jump on a plane and fly in to. They need data and lots of it plus time to pull together the correct equipment and resources.

Plus there's nothing I've seen or heard that indicates the situation is out of control. Serious? absolutely! But out of control? No way. Not yet!

There are still a number of options available to the Japanese and as others have said, containment appears to be holding.

The releases that have occured are all involving volatile compounds which in an event like this is actually a good thing.

But if there are further generator failures and the cooling systems keep tripping out, the problem will escalate.

However, the reactors are stopped. Let’s be clear on that. The controls rods were inserted and THE REACTORS WERE STOPPED!

The problem now is how to dissipate the residual heat. That’s what the cooling water is for.

At the moment the scenario is the household equivalent of having a pot on the stove on very low heat. If the pot stays on the stove for long enough without the heat being removed the contents of the pot will eventually boil dry and the pot will melt, but it takes time to get to that stage and there are lots of things you can do to cool the pot if you cant take it off the stove.

Destruction of the external power source and hence the ability to run the cooling water system (taking the pot off the stove) is one of the most serious scenarios in nuclear power plant design and we spend an inordinate amount of time thinking about that when designing safety systems and backup systems. That’s why there were multiple sets of generators available and why there are multiple cooling water systems. What I’m not clear on at the moment is which actual cooling system failed. (I worked on PWRs not BWRs and while lots of systems are similar they are not absolutely identical)


The plant actually performed extremely well under the initial earthquake circumstances. It withstood an earthquake about 10 times bigger than what it had been designed to withstand (dont ya just love safety factors) and they stopped the reactors, but the tsunami was also proportionally bigger so it took out the generators and the residual cooling system. The safety systems designed into a typical BWR would consider all generators being taken out in one strike as a complete defence penetration and is probably the most unlikely scenario considered (at least it was in my day). But still there are the emergency battery driven systems to cope with that scenario but they are only designed to operate for a few hours - long enough to bring in more diesel generators. And again they did their job; things were being cooled nicely until the batteries ran out. Thats when the first line of defence started to fail and the outer casing of the fuel rods started to melt. But the rods themselves didn’t melt, only the outer casing and then only partially. What the operators will be doing at the moment is trying to keep the rods below the critical temperature (and before you ask no I don’t know exactly what that will be but it will be at least +2000deg I would guess) so the rest of the casing doesn’t melt.

The problem as I understand it is that due to the earthquake and other damages in the country and its infrastructure, its taking the Japanese longer to get the correct replacement generators on site. But even without the generators there are still things they can do. Think back to your high school science classes and what you were taught about how temperature and pressure are related. If you can't reduce the temperature you can reduce the pressure, which is what they’ve been doing when they vent the valves. That buys them time and as I said earlier, at the moment the vent gases are all volatile compounds. So the first line of defence (the casing on the rods) is still there but it has a few holes.

So for all you doom-mongerers out there - Yes if they can’t get the cooling system restored the core willeventually melt but complete core meltdown can take days and there are still multiple lines of defence to be used.

At the moment the plant operators will be doing what is called retreating the line of defence, ie as one safety mechanism starts to fail they start using the next one as well to the next one. But as each safety mechanism is used and they fall back a line the situation gets more serious which is why they are now bringing in other experts and their equipment cos the first line has been breached (not yet failed, just breached). Again standard protocol and part of the normal safety plan for a nuclear plant


Now this probably seems shocking and scary to you and the media are freaking as the operators fall back to each line safety system, but this is part and parcel of what we train the operators about, up to and including a core meltdown. I guarantee you that however much training you think you get in your job its nothing to what these guys get.

Anyway I’ve rambled on a bit. Its not easy to explain the safety systems of a nuclear plant in 3 words or less. Hopefully I haven’t been too technical but still covered most of the questions asked.

And by the way to whoever it was that said I earlier said the nuclear power was safe, go back and read my first post. I said it was statistically safer than coal fired energy. All systems have inherent risk and can never be considered fully safe. Just as well or I wouldn’t have had a job all those years ago.

Oh and if you ever get caught in a nuclear event.... dont bother with those paper face masks / surgical masks you see people wearing; they do sweet F%$& all, apart from make people that dont know any better feel safer and calm down the panickers.