Earthquake in Japan

[Umfriend]

Because it's not like, uhm, if these reactors blow, the antinuke power brigade had a point after all?

[Dr Mordrid]

Only so far as water cooled reactors that can melt down. There are many reactor designs that are neither water cooled nor capable of melting down. Some have a normal operating state where the reactants are dissolved in molten salts that have a very low vapor pressure - a very safe and proven design.

Many of these don't even use uranium as a primary fuel - they use thorium. More common, cheaper, far fewer long-lived actinides as waste and often self-regulating. Molten salt is one of these.

[Sasq]

Considering Japans land mass, as well as Japans limited (read negligble) natural resources in the power department, nuclear power really is their only option considering the population/land mass.

That said, the company(s) have been known to be very Mr Burnsesq in their maintenance.

[J1NG]

Just glad fellow MURC'ers are all safe over there.

Unsure about the ongoing reactor business though...

J1NG

[Wulfman]

Any confirmation that the reactor should have been end-of-life in March 2011 ("now") anyway? Murphy...

[Dr Mordrid]

The Wiki article on the Fukushima reactor has a good rundown on what's known so far..

Article....

[Dr Mordrid]

NOAA: tsunami wave heights

Beautiful, scary and too big to use [ img ]

NOAA image....

[Brian Ellis]

Combining info from various sources:

All 6 reactors at the plant are ancient Generation II technology from 1971-1979. They are all General Electric immersion boiling water reactors, which is not considered "best technology" by modern standards. The #1 is the smallest, pilot plant, and is 40 years old and must be considered as "end-of-life". Fortunately, 3 of the reactors were closed down for maintenance. Of the 3 that were working, it is essential that the reactor fuel is immersed at all times. This has not been the case with #1 and #3, hence the problems leading to overheating at the top of the fuel rods and the consequent rise in temperature. MY SPECULATION: did the bottom fed (poor technology) control rods not reach the top, for some reason? The basic cause of the problem was that there was a grid power failure, which meant there was not enough power available to keep the BWRs running in emergency mode. I suggest that this was poor technology that required a grid connection. The emergency supply was given by batteries with a limited lifetime. AFAIK, the reactor pressure vessel and the containment shield are intact in all reactors, although controlled venting has been necessary to avoid a dangerous pressure build-up, leading to a "small" release of radionuclides from reactors 1 and 3. Details of this are not yet forthcoming, but is being played down. The worst-case scenario may be plutonium from #3. These problems have been exacerbated by the use of sea water for emergency purposes.

One big question is whether this could happen with a modern Generation IIIa reactor? The answer is categorically NO. They are not grid-dependent and have each multiple diesel generators to supply full control power. The control rods are all gravity-fed and are held in normal working position by solenoids. All safety devices cut the power to the solenoids and ordinary and emergency control rods drop immediately down into the core. Emergency cooling is done by gravity-fed water from tanksabove the reactors; this is pumped in an initial emergency phase to sprays; if this is insufficient, flooding takes place. The volume of available water is sufficient to cool the reactor to safe limits. All the safety devices are quadruple-redundant.

Getting back to Fukishima, one may ask why some of the modern safety systems, such as the multiple diesels and the gravity-fed water, were apparently not post-fitted.

I admit that some of this is speculation from reading between the lines of the sparse info released.

[Sasq]

The story will play out Brian, and I am fuzy on details, but all the TEPCO reactors have issues that have never been correctly addressed.

[Dr Mordrid]

Combining info from various sources:
>
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I admit that some of this is speculation from reading between the lines of the sparse info released.

Brian - looking at similar, perhaps even more detailed data on reactors 1 - 3, and with the perspective of having worked with rather hot radionuclides, all I can say that would be comprehensible to the others here is:

WTF WERE THEY THINKING ??!!??

There is absolutely no reason why the upgrades you outlined should not have been done, and more. IMO they should have been replacing those boiling water reactors before even thinking about expanding, as in 10-15 years ago.

Dumb, dumb, dumb. I might go so far as to say both regulatory and corporate heads need to roll.

[Brian Ellis]

Update to my previous post:

It appears that they DID have diesel backups but they failed after one hour. See http://www.bbc.co.uk/news/world-12723092 - this implies a choice of 1) insufficient redundancy 2) unsuitable machinery installed 3) inadequate testing and maintenance 4) insufficient power generation capacity, implying unreliability 5) not enough diesel fuel.

Take your choice, 1-5, but, whichever you choose, it displays, IMHO, cynical negligence on the part of ****youshima Dai-Ichi and/or its bosses in Tokyo Electric Power Co. BTW, I think, if my Japanese is correct, Dai-Ichi means No. 1, in the sense that they are the best (Sasq will correct me if I'm wrong!)

[Dr Mordrid]

It seems the reactor core cooling system pumps were steam driven, but their controls (valves etc.) use DC from batteries that need recharging by the generators. The problem is that these were not placed where they'd be protected from flooding (not sufficiently elevated) and may have not had redundancy. Also a problem is that the batteries could only power the control system for 8 hours - obviously a far too thin margin.

Again I ask: WTF ?!!??

[Brian Ellis]

Do you mean WTF..K-you-shima?

[Dr Mordrid]

Whatever displays disgust best. Hell, if generators were so important to the safety of the facility why not mount them on a friggin roof? Stilts? Whatever it took .... I've seen that kind of installation on the coasts of the Great Lakes, so why not the Pacific?

[UtwigMU]

You also have to account for magnitude of earthquake. 8.8 is extremely unlikely, the highest zone you build for is 8. Also when you are planning buildings you usually presume that when earthquake hits, there is no strong wind and roof is not fully cowered with snow... Though when designing nuclear plants you take all worst case scenarios in consideration.

Here we had 8.8 earthquake and tsunami, if you look at where the plant is and where the epicenter was, the water washed over the plant. Despite current problems I think it could have been worse and plant withstood what was probably beyond worst case scenario predicted.

Obviously cooling is a problem and I don't think they have many options left. Using sea water as emergency is a first since sea water causes corrosion and you don't want to do it with reactors. They are pumping sea water inside reactor and the level is not rising. Also they are pumping in boric acid (during Chernobyl aftermath it was being poured by helicopters)

Since the building blew off (probably by-product hydrogen exploding with oxygen and steam) the question is to what extent is the reactor still contained.

The partial meltdown has already occurred at one of reactors and once that happens you cannot manipulate control rods (once they tried to insert control rods in Chernobyl, since reactor's thermal power output was rapidly rising, the water evaporated, the rods twisted and the graphite tipped control rods shattered and jammed, a fire broke out). Here the rods were automatically inserted at time of earthquake but high temperatures and explosion might have damaged cooling pipes.

For some strange reason, the night before earthquake I was reading up on Chernobyl disaster online. The accident there occurred because they were testing whether the steam from spinning down turbine is enough to power emergency cooling for 2 minutes until diesel generators are online.