The "more political thread" besides "Japan Earthquake: nuclear plants" scientific one

Astronuc

Don't read more into the terminology than temperature at 1 atm.

NUCENG has already discussed the use of the term.

Cold shutdown
The term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200 degrees Fahrenheit following a reactor cooldown.
http://www.nrc.gov/reading-rm/basic-...-shutdown.html

Shutdown implies that reactor/core is subcritical.

zapperzero

http://online.wsj.com/article/SB1000...581004368.html
Japan Officials Failed to Hand Out Radiation Pills in Quake's Aftermath says the title.
So much fail.

tsutsuji

http://online.wsj.com/article/SB1000...288145094.html "Japan Panel Says Nuclear Agency Manipulated Forums"

http://mdn.mainichi.jp/mdnnews/natio...na007000c.html criticality accident anniversary: Tokai Mayor "showed his anti-nuclear position."

tsutsuji

http://mdn.mainichi.jp/mdnnews/news/...dm010000c.html "The head of Japan's largest labor organization said Tuesday that the 6.8 million-strong body will seek to eventually realize a society not dependent on nuclear power, marking a shift from its previous stance of promoting atomic energy."

joewein

...which reminded me of a quote in a Japan Times interview with freelance journalist Satoshi Kamata published on Oct 2:

So if Rengo switches sides, it could be quite an interesting development, also considering the close links between Rengo and the currently ruling Democratic Party.

tsutsuji

http://mainichi.jp/select/jiken/news...40029000c.html The ministry of education is publishing and distributing to schools new versions of reading books about radioactivity. Expressions such as "Nuclear plants are built in such a way that makes them safe from big earthquakes or tsunamis" that were written in the old versions have been removed.

clancy688

That says a lot about their "newfound confidence" in safety measures. It probably would have been enough if they'd just slipped a "are supposed to be built in such a way" into the text, but I won't complain.

tsutsuji

http://www.yomiuri.co.jp/dy/national/T111015002391.htm English article about nuclear science education in Japanese schools.

Astronuc

Also from Yomiuri, NISA secretly calculated Fukushima meltdown risks / Agency considered worst-case scenario of 'China syndrome'
http://www.yomiuri.co.jp/dy/national/T111015002539.htm

The key statement is: "The calculations indicated that if cooling water could not be injected, . . . ."

So why didn't TEPCO come out and say that they believed some fuel may have melted. Well, they eventually did, but they didn't know, and they still don't know how much (they would be left simply speculating). And they (and we) won't know until the RPVs are opened and the cores are visually inspected.

From the hydrogen and activity release, it is clear there is a lot of damage to the fuel, but a lot of damage could have occurred well below the melting point of the fuel and cladding. The cladding and channels would have oxidized considerably at half the melting temperature of the Zircaloy-2 material. Once the cladding is breached, the inner Zr-liner would have rapidly oxidized at even lower temperature, and the fuel would have been exposed to the coolant, and it would have started to oxidize. Other than the volatiles, the severely oxidized fuel would have fallen into the coolant - but it would not have melted. Only if the core had gone completely dry (essentially adiabatic conditions) would the fuel have melted.

Since water is the source of hydrogen, there had to be water in or below the core, and that would reduce the likelihood of the core melting through the RPV. It remains to be seen if the cores in units 1, 2 and 3 ended up like TMI-2's damaged core.

zapperzero

Five years minimum, according to TEPCO roadmap.

Why in the name of Stinky Pete they do not just stick borescopes in there is beyond me.

Knowing the shapes and locations the fuel's in would help prevent recriticality and optimize cooling, so it's not like they would be doing it just to satisfy our curiosity.

Astronuc

It's not so easy. They would have thread it though one of the feedwater lines, and then get it through the feedwater sparger, and arounound the hardware above the core. Above the core are the moisture separator and steam dryer. To go in through the top, they'd have to remove the RPV head, and before that the plug. They have no heavy lifting equipment in place to do that. They'd have to remove the steel from the upper containment first.

See the details here - http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

NUCENG

IF the boroscope will fit through instrument lines, and the lines are intact, and the boroscope can survive the process conditions, and if water clarity permits, and if rad levels permit access to the penetration area by personnel to install the boroscope, there are routes to the drywell via the drywell and suppression chamber instrument lines, to the vessel outside the shroud through the vessel pressure and level instrument lines, and to the lower plenum inside the vessel through core differential pressure lines.

Navigate the IF minefield and get your camera is there and photograph the debris. Now what will you use that information for? What could you see that would change what they are doing now? They are still trying to ensure that the fuel, wherever it is, is covered and cooled to below 100 degC. Boiling keeps things stirred up and would probably be detrimental to getting useful pictures. How long was it before they inserted cameras at TMI? Is it worth the dose and risk to do this now, before completing site cleanup and building the containment "tent" structures?

I am curious, too. I "hope" they plan to look for the fuel before they start trying to remove it, but if it isn't at the top of their ppriority list right now, I can understand that, too.

zapperzero

We keep having this conversation, which says a lot about my pig-headedness and your patience, both.

I think after the tents are up working inside the reactor buildings will be harder not easier for the reason that radioactive steam will still be wafting out even if all the water is below 100 degrees Celsius.

I do not know if it is worth the dose. Maybe it is. Depends on what one would find. I would at least try to put a borescope into the drywell, below the RPV bottom head.

I may see that I need to add more boron ASAP because there is fuel and it is in a nasty configuration.

I may see that the RPV is whole, or I may see that it isn't, which would probably affect the choice of cooling lines and help me minimize water use.

I may see other, unexpected things, such as severely cracked walls/floors, a big honking hole in the middle of the drywell floor into which the fuel is sinking and so on and so forth. Interesting stuff that may make me change my priorities radically.

I may see nothing, in which case I would retrieve the borescope, see what sort of dose it got and if it got hit by any neutrons and call it a day. Then you'd criticize me (rightly, because hindsight is always 100%!) for wasting time, money and exposing people to unnecessary risk.

Astronuc

Assuming the core melted - from the top down - since the top would be first exposed if coolant was leaking from the bottom of the vessel, it is better to look from the top down - as was the case at TMI-2.

Alternatively, they could look at the outside of the RPV before opening it in order to determine any breaches to the primary systems and RPV. It may be possible that some pipes rupture, or some control rod drive mechanism (CRDM) housing tubes broke. That would be useful to know.

Some useful information on BWR details here - http://www.ansn-jp.org/jneslibrary/npp2.pdf

NUCENG

No criticism planned or intended. I have no argument with you personally and neither of us will make that decision.

tsutsuji

The IAEA is afraid that the Japanese government might set more severe decontamination standards than the IAEA is ready to accept:

Instead of "As low as reasonably achievable", the IAEA's philosophy seems to be "as high as reasonably achievable" :

zapperzero

This is all hypothetical, of course. But I expressed myself in that manner to emphasize the fact that I agree with you - such a venture may very well yield nothing but a net loss of time, money and human health.