Fukushima spent fuel pool over reactor 4 in danger of collapsing

Statistician

SeanW wrote: »

The RBMK reactor used at Chernobyl-4 was known to have a dangerously high positive void co-efficient. The entire technology should never have been used in the first place, and it was not used outside the Former Soviet Union because Western entities understood the dangers very clearly.

The high positive void co-efficient was not in itself 'unsafe'. In fact this attribute gives the controllers time to control the fission rate. The problem was that they were running the reactor at a very low power, which makes it harder to control. The operators were not adequately trained and they did not want to go above the chain of command.

That's very simplistic. It would be much safer to have 100 Light Water Reactors than it would be to have even 10 RBMKs.

Not really.
Chernobyl happened primarily because of human error. The reactor didn't just decide to blow up one day. As long as we have human error, we will have accidents.
There are still RBMKs in operation.

SeanW

Statistician wrote: »

The high positive void co-efficient was not in itself 'unsafe'. In fact this attribute gives the controllers time to control the fission rate. The problem was that they were running the reactor at a very low power, which makes it harder to control. The operators were not adequately trained and they did not want to go above the chain of command.

That's true, a combination of Soviet insanity and dreadful reactor design meant that an accident of that kind was inevitable.

The reactor didn't just decide to blow up one day.

No, but when I was an anti-nuke and I trusted the Green types, I was very much under the impression that it did.

There are still RBMKs in operation.

Yes, all in Russia. As a supporter of nuclear energy, I want them all decommissioned replaced with safe reactor types. They were a bad idea, and though I think with the modifications made after Chernobyl and more careful operation they may be OK, I'd still just as soon see the back of them.

Statistician

SeanW wrote: »

That's true, a combination of Soviet insanity and dreadful reactor design meant that an accident of that kind was inevitable.

The reactor design wasn't that bad. They could be made quickly and punched above their weight for power output. I would say they were designed as a result of the cold war and were not used anywhere else for the same reason.
If the reactor was run within operating parameters then the Chernobyl disaster would not have happened. Believe it or not, they had already made containment design improvements for unit 4.

Yes, all in Russia. As a supporter of nuclear energy, I want them all decommissioned replaced with safe reactor types. They were a bad idea, and though I think with the modifications made after Chernobyl and more careful operation they may be OK, I'd still just as soon see the back of them.

But you don't mind other reactor types?
In fact, I would say what the Japanese did (location of reactor) was worse. A tsunami and earthquake was likely.

I'll say again, it's human error that causes these accidents.

SeanW

Statistician wrote: »

The reactor design wasn't that bad. They could be made quickly and punched above their weight for power output. I would say they were designed as a result of the cold war and were not used anywhere else for the same reason.
If the reactor was run within operating parameters then the Chernobyl disaster would not have happened.

Hmmm ....

http://en.wikipedia.org/wiki/RBMK wrote:

However, it does make it considerably harder to control the reactor (especially at low power) and makes it imperative that the control systems are very reliable and the control room personnel (regardless of rank or position) are rigorously trained in the peculiarities and limits of the system. Neither of these requirements were in place at Chernobyl: since the reactor's actual design bore the approval stamp of the Kurchatov Institute and was considered a state secret, discussion of the reactor's flaws was forbidden, even among the actual personnel operating the plant.

Yeah, hand the keys of a nuclear volcano to a group of newly trained electrical engineers, have them to a dangerous "safety test" and don't even let them discuss what an inherently unsafe, difficult to control, ill concieved heap of crap the entire system is.

[sarcasm]I wonder why it didn't work? :rolleyes:[/sarcasm]

Believe it or not, they had already made containment design improvements for unit 4.

I don't believe it: one of the many design flaws of the RBMK reactor was that they usually skimped on containment buildings. While it's common for most nuclear reactors to have two large containment buildings - a primary and secondary containment vessel - the RBMKs including Chernobyl-4 only had a partial primary containment in the form of a Uppper Biological Shield, which proved to be about as useful as a chocolate fireguard.

But you don't mind other reactor types?

Absolutely. A safe nuclear reactor design is better than a coal fired power plant any day.

In fact, I would say what the Japanese did (location of reactor) was worse. A tsunami and earthquake was likely.

Yes, which is why little things like putting the diesel generators out of the way of potential floodwaters could have made all the difference.

I'll say again, it's human error that causes these accidents.

Can do, but it usually needs help from things like institutional insanity (like what they had in the Soviet Union) and awful reactor designs (also common in the Soviet Union), put the two of them together for long enough and of course something's gonna go BOOM eventually.

But I think that the wholesale quantities of both needed to cause a Chernobyl style accident could only have been found in the Former Soviet Union, or a similar hellhole.

Overheal

The problem with nuclear isn't the risk posed by the plants themselves but really what to do with all the waste. We still have very poor handling methods for storing spent fuel rods. Whats more they can still be used to create dirty bombs, and so you can't just dump them anywhere. South Carolina for instance, is large manufacturer of fuel rods. Inversely, we're also a large store for the spent fuel rods, and home to a Navy and Air Force base in Charleston. It's not by accident.

I'd also like to point out designing a reactor is a lengthy process. Designs being actively developed Today wouldn't even be conceivable as ready to build plants until the 2030s. And then you still have to actually build them. As a result, You have to figure the plans for Fukushima were probably being drafted way back in the 50s. 60 years later, the design (BWR) had an accident. Three Mile Island (PWR) was designed aroudn the same time, commissioned around the same time, and had an accident back in 79. Hey guess what, no earthquake necessary.

Solair

SeanW:

That's actually one of the reasons why I am not totally opposed to the UK's plans to build new nuclear power plants.

The existing UK fleet is getting very old !! Wyfla, the last working Magnox (first generation British gas-cooled system) plant, which is not very far from Dublin was built starting in the early 60s and has been online since 1971 and was due to shut down several years ago but has been kept going out of economic necessity.

I would worry that keeping creaking old reactors going, is a much riskier option than putting up with new ones being built to replace them.

There's really no way that the UK's likely to be able to switch to alternatives to nuclear power in the medium term, but there should be some kind of a plan to do so in the long term and phase it out in say 30 years.

I would also think that spending billions on energy waste reduction (i.e. reducing building energy losses, etc etc and renewables / electricity storage systems (pumped storage etc) might actually offset the need for extra nuclear capacity and would still reduce CO2 output, without all the legacy costs associated with nuclear i.e. decommissioning / waste management.

When you consider the cost of construction + maintenance + waste disposal / storage of these plants, the economics start to make less and less sense. When you throw in the decomissioning costs, it's even worse.

The UK's current estimates run at about £73.6 billion and will take about 100 years to complete. The cost at the moment is running at over 2 billion a year in decommissioning alone.

The UK's fleet of AGR (Advanced Gas-cooled Reactors) built in the 1970s and 1980s came in massively over-budget, really late and astronomically expensive.

One plant took 20 years to build!!!! (Started in 1965 and was connected to the grid in 1985!!) It was 13 YEARS late.

I just think we need to do some real cost:benefit analysis of nuclear power as unlike conventional power, it's not just the initial build and fuel costs.

Decommissioning a normal gas/oil/coal plant is a relatively VERY trivial matter in comparison!

ScumLord

Statistician wrote: »

After the Chernobyl disaster we heard how the design was improved (+/- void coefficient, graphite core, tipped control rods and containment) and such a thing could never happen to new reactors.

There isn't much they can do to the design of current reactors it's a flawed design in that they where built to take advantage of the waste for nuclear weapons. New plants don't even need to run on uranium and switching to another element would reduce risk drastically.

Solair

The main reason the RMBK wasn't ever exported is because the only reason you would need such a crazy system was to produce plutonium for weapons.
So, other than the USSR, no Eastern Bloc country would have wanted them.

The Russians more commonly used a system called VVER for civil nuclear energy. It's quite a safe system, and is comparable to modern Western designs. It's a pressurized water plant with good levels of containment.

A modified version, with better containment and more modern controls is even used in Finland and also in the Czech Republic.

Same goes for the UK Magnox designs. They had a dual purpose in the past.

Magnox, being gas-cooled however, is arguably a hell of a lot safer than RMBK. It has quite a lot of nice safety features, such as being able to cool passively in the event of an emergency, no risk of steam explosions etc etc as the coolant is a gas to begin with. The same goes for the AGR design which came later.

Nowadays, these countries are all trying to desperately get rid of stock piles of plutonium by 'burning' it in MOX fuel as they no longer need all the nuclear weapons.

So, a lot of the safety compromises, including using MOX fuel (as in Fukushima) are unfortunately byproducts of nuclear weapons programmes or decommissioning of same.

Run_to_da_hills

It looks like Tepco dose not have the money to sort out Reactor 4.

"The problems at reactor 4 are the greatest short-term threat to humanity and has the potential to destroy our world and TEPCO doesn’t have the money to fix them".

http://peakoil.com/enviroment/tepco-not-enough-money-to-handle-fukushima-nuclear-reactor-4-problems/

Solair

They really shouldn't be leaving this to TEPCO.

In the US, UK or France this would be immediately taken over by a state nuclear decommissioning agency of some sort with the full support of the state and probably the military too.

I am surprised this isn't the case in Japan.

Leaving it to a bankrupt utility company seems absolutely crazy.

The USSR was able to put vast resources into cleaning up Chernobyl because it was a huge military-industrial complex with vast manpower, nuclear experience and an ability to just sweep aside the civilian stuff in the case of a national emergency. It was also a dictatorship / command economy. However, in situations like Fukushima, sometimes that kind of system tends to work best rather than letting a private company try to deal with something that's probably beyond its abilities.

It also means that you can evacuate people efficiently etc etc.

I'm not for a moment saying that the USSR was a nice regime, or a nice place to live, but I'm getting the impression that in Japan it's the other extreme where the Government is deferring to a private company in a nuclear disaster!

TEPCO's financial situation shouldn't even enter into the argument at all. The money should be made available by the state, and the resources put in regardless!

Statistician

Here is a press release from the Radiological Protection Institute of Ireland:

http://www.rpii.ie/Site/Media/News-and-Updates/Impact-of-Fukushima-on-Ireland.aspx