hosing Japanese Nuclear reactor with sea water

Their cell insertion/extraction unit seems to be defective, or worse... some cells overheated and melted, so are no longer extractable from the core. You saw the water vapor blast at the news today? This is really not good, not at all... We can fear the worst, I'm deeply sorry to say.

Bye.

A nuclear physicist on the beeb yesterday said that the explosion could well have been hydrogen gas, and if so, was probably not too much to worry about. He also mentioned cooling the cores with seawater as a sensible option. However, we should all hold back from alarmist what-ifs til the facts are known. Tony

Maybe they know but they is not tellin'. Innit.

On the radio this morning the Japanese stated that 2 reactors had suffered meltdown and a 3rd was probable.

So that is 3 out of 4 in real trouble.

David

I'm in that most dangerous position of having a little knowledge so will try and stay within my limits!

I guess the most striking thing about this for me is that the plant appears to be designed to withstand an earthquake but not a Tsunami as well - I would have hoped that the design basis accident would be a combination of both (not unreasonable if your power station is on the coast facing the fault line?). The combination of a severe earthquake (worse than a 1 in 100 year event) with a Tsunami to wipe out the back-up supplies seems to be the root cause of the problem.

As I say I'm not an expert in this type of plant (though I've worked with PWRs) but I'm not hugely concerned by the explosion. The key issue would have been if the explosion was inside the primary containment (like at Chernobyl) rather than outside (sort of like 3 mile island). Pouring in salt water to provide extra cooling makes sense to make it safe (well safer at least) but does render the reactor FUBAR (that's a techical term for unusable!) I think they are also pouring in stuff to kill any reaction which also makes sense.

The big problem is if the water boils off leaving the core exposed and the temperature spiralling (which would explain the Hydrogen build up). I don't think this is as a result of a problem with the fuel or the control rods per-se but the consequence of loss of secondary cooling and shed loads of heat knocking around in the now shutdown but still very hot reactors. I'm slightly bemused because, if it was a PWR, I thought that there would still be sufficent convection to produce sufficent flow. Perhaps I've remembered that wrong or this design is significantly different.

Given the levels of heat, I fear it will be at least a few days before we can breathe more easily. I don't think there is any doubt that there will be serious engineering challenges to be overcome to sort out what's left - it's going to be a bit of a mess inside the primary containment.

So overall I suspect Japan has some work to do to manage the next few days but is then down by at least 3 nuclear reactors for years to come. Ironically this potential loss of electrical supplies may well turn out to lead to more fatalities than the accident itself.

...my thoughts are with those in peril in Japan at this time but particularly the nuclear workers who are probably dealing with this whilst having no knowledge of whether their own families are safe. Here's wishing them luck on both fronts

Martin C

I guess we forget in these situations the hundreds of people killed every year directly from the supply and production of energy from fossil fuels (let alone its associated harms). When we hear of the risk from a nuclear incident perhaps we have to keep that in perspective.

Best of all not take our energy usage for granted.

Bruce

Well said Bruce, but it's more than hundreds. In China, 6700 deaths were reported in coal mines in 2002. Many believe that many deaths go unreported. In 2009, the Chinese government reported 2632 'official' fatalities.

As Scientific American put it :The popular conception of nuclear power is straight out of 'The Simpsons'

It is not residual heat but what is known as 'Decay heat', caused by radioactive decay that is still happening even though the reactor is shutdown and follows the atomic 'half-life' principle, hence the term 'Decay Heat', this heat output decays expontentially with time, . This is a fact of life for any type of reactor which is why 'post trip cooling' systems and their water / power supplies are an essential facet of any reactor design. It appears that the reactor withstood the earthquake as designed but the subsequent Tsunami disabled the back up power generators, probably by contaminating their fuel oil supplies with sea water. That together with the massive amounts of debris swept up in the seawater blocking the cooling water pumps thereby disabling the post trip cooling systems.
Flooding a reactors' primary circuit with sea water and Boric acid (Boron is a neutron absorber and ensures the reactor remains shutdown, i. e. sub critical) is a last resort and renders the reactor unservicable for future operation.

Are any reactor designs 'inherently' safe ?

It's a shame that an emergency reactor kill facility isn't mandatory on all reactor types.

Health and safety rules aren't helping. 

The defence force aren't allowed to let the personel to enter an area having >100mSv/h. The helicopters could not fly below 90m. Radiation at 90m approx 90mSv/h.

Radiation at perimeter of power station is 290mSv/h

Radiation at 30m above reactor was approx 250mSv/h 

So, if the pilots where able to be exposed to a radiation level similar to other emergency workers, a lot more water would have hit the target.

It's political correctness gone mad.

Tough talk is probably pretty easy from half way 'round the world.

DCT

Second here, I once read about some kind of "Inherently Safe" reactor. Could someone please explain??

Regards,
Michel

DCT,

"Tough talk is probably pretty easy from half way 'round the world."

That's the point I was making. I keep forgetting that there are people who use phrases like 'political correctness gone mad' seriously.

So here is a question.

Should the authorities (and we are surely talking internationally rather than locally) consider placing a few employees at serious risk (or even inevitable harm) to avert a situation that may affect tens of thousands or even millions around the world.

I hope that is not where we may be with this.

Bruce

So here's an answer.

Like everything else it's a matter of judgement. Their judgement. Not ours. We know nothing about it.

David

It would be a matter of ethics as well as judgement, indeed it is a well known ethical and philosophical chestnut that has been kicked around in a variety of (theoretical) scenarios. Potentially this current crisis might make that real.

Some people might have a view on that philosophical question. I thought that may be an interesting debate, irrespective of our knowledge (or otherwise) with regard to the specifics.


Bruce

Bruce,

As it happens I'm pretty interested in ethics and I was thinking of a moral judgement just as much as a technical one. It's really hard to imagine (to take it to an extreme for a moment) that anyone would argue it was right to let everyone on the planet die rather than ask a few individuals to take a risk which would be considered too great under normal circumstances, but in any given instance the judgement of whether or not to do so depends upon  specific practical details and assessments of risk to which in this instance, we are not privy . We could have a theoretical discussion about it, but I think it would be pretty meaningless. I see ethics as a practical business of making actual moral decisions in specific circumstances. Discussion is helpful if it helps to clarify and refine that process, but too easily gets sidetracked by a search for a set of absolute principles or a universally applicable moral calculus, which, when applied in practice, lead to some profoundly immoral decisions. One size doesn't fit all and in this case we don't know the measurements.

I pretty much agree with all that David, I use principles to make decisions with varying amounts of ethical challenge every day, but hope that I do so on an indivudual and personal basis. I absolutely agree that ethics are not about a 'universal moral calculus', exactly the opposite.

I'm aware that as a population (and indeed a forum community) we don't always have the same priorities or values, and these inform individual choices.

I quite like a stimualting discussion about such issues, helps me to understand and think about other viewpoints.

All the best, thanks for replying

Bruce

When the chips are down, you ask amongst those with the required skills for volunteers (or you ask for volunteers and give them the necessary training). You promise to look after their dependents if this becomes necessary.

Cheers

Don

Thing is that if the "chips were down" there would be no need to ask the few to step up to the plate, they'd do it without asking.



Willy.

What is a bit surprising is that the only reports of iodine being offered to Japanese residients seems for British people living there. Surely this kind of thing should be planned for strategically in any territory running niclear power plants.

After Chernobyl this measure was brought in very fast by the Polish Health Authorites, and indeed even now iodised salt is the norm there even after all this time. It is a question of protecting the Thyroid gland from picking up radio-active isotopes of iodine ...

ATB from George

It would appear that that cultural millstone Saving Face could be a primary obstacle in this disaster.

The denial of the severity of the problem, then no need to take action compounds the problem.

I am no engineer but the reactors are 100m from the sea. they could have flown in large generators and large water pumps and us the sea water. But instead they chose helicopters to drop water as in a forest fire scenario.

There is also the continous contradictory information being given.. it is undercontrol. it is getting worse. The manager of the complex was shown i n tears when he finally admitted that the problem was severe.

The govt itself has contributed to this lack of information, to the press which i read.

To give those affected by radiation Iodine is an admission of the severity of the problem, so FACE means that it has not been given.

Japan is the 3rd richest country in the world. it is a massive 1st world industrial  powerhouse with world class technology.

Yet

It seems incapable of pumping vast quantities of sea water 100m  onto the reactors and the waste fuel rod storage.

As it has 50 odd reactors and is a Seismic series of Islands i find this lack of forethought and vision amazing.

David