Japan Earthquake: nuclear plants

a.ua.

http://www.tepco.co.jp/nu/fukushima-...ssaiboku-j.pdf

A large amount of cobalt 60 at fuel rods from 4 pools.
The result of the criticality and neutron radiation flux.?

jim hardy

do you know where was that measured?

Reactor steel is selected for low cobalt content but it's not zero.
Might be coming from the steam dryers or shroud , if they're in the pool.

http://www.evs.anl.gov/pub/doc/Cobalt.pdf
Co60 is a comparatively penetrating gamma ray that'll go considerable distance.

NUCENG

I may be mistranslating, so please help me out. But this appears to be data about debris and tree clearance samples. The reports for Co-60 Bq/gm activity are four orders of magnitude lower than Cs-137. Agreed, Co-60 is a very energetic radiation source, but its activity is hardly a "large amount" wwhen compared to thre total source term in the samples.

The two exceptions samples 4U-N01 and N03 are described as Unit 4 "rubble???". I don't see any tie to 4 spent fuel pools. a.ua. can you explain?

a.ua.

4U‐N01 Rubbed with a cloth rod, it is dirt that remains on the rag.

Hmm, maybe the neutron flux was coming from the spent fuel, which got taken out at the planned preventative maintenance.?

But in Chazhma Bay also had a lot of cobalt 60.



jim hardy thank you!

NUCENG

Sorry, I didn't understand that. Jim is right that activation of Cobalt is the masin source of Co-60, and that requires a neutron flux consistent with your last post, but if I was reading Japanese correctly the sample was near Unit 4. Your initial post suggested there was a lot of Co-60 from the four spent fuel pools. Were you suggesting criticality in Unit 4 SFP to explain the Co-60 in the samples or a wider problem at all the reactors. I'm trying to clarify only.


Woops just saw the fine print about the Russian submarine accident. I'll take another look. Co-60 has a very low yield as a fission product in light water reactors with low enrichment. It is possible that changes in a criticality accident or it may be due to higher Co-59 inventory in old Soviet fuel design. More to follow.

NUCENG

It is clear that the fission product yield of Co-60 is near zero and that wouldn't be significantly different in a criticality accident even assuming fast fission. Old Soviet Submarine fuel designs may have used stainless steel cladding which would explain increased Co-60.
So it looks to me like the release of Co-60 is not likely to be fuel debris. Activation of steel or other materials containing Cobalt is the only likely source of Co-60 at Fukushima. If the samples (cloth swipes) were taken from the fuel pool or some rubble outside of Unit 4 it means that we can't really tell whether that indicates a criticality event. The dryers and separators and the old core shroud at unit 4 would be possible sources for debris. If these were stored in the equipment pool under water, I'm unsure how a hydrogen gas explosion in unit 4 would have blown parts of these items outside the building. They would haave been at opposite ends of the refuel floor. If these items were on the refuel floor it would be more likely.

a.ua.

NUCENG
Yes they were taken from the fuel pool.

SteveElbows

Hello, I am back after taking my eyes off the situation for some months. Have we discussed any reports or data relating to the following translation of a press article? It is concerning the time that water injection into reactor 3 may have stopped, with the possibility that it stopped 6 hours earlier than TEPCO had previously assumed.

http://ex-skf.blogspot.co.uk/2013/03...r-3-those.html

The press report is only days old, but it sounds like the data it is based on is from last year, any ideas about this data?

People may remember that I was always rather unimpressed with the timing & water assumptions TEPCO used when attempting to estimate core damage based on factors such as decay heat and water levels in the reactor. So I am pleased to hear that they are apparently going to redo their analysis in response to this data. I hope that this time they also do not simply use the most optimistic of assumptions in terms of when fire-engine pumped water injection started, and do not assume that this was uninterrupted and sufficient once it began. Especially in light of the other stuff discussed earlier about the possibility that a lot of that water ended up in the condenser.

SteveElbows

The other thing I dont think I see mentioned here from recent months is that on February 1st TEPCO published a huge number of photographs from the early days of the disaster. Some of them are the same or very similar to ones they released previously, others are from different angles or show thing we didnt see before.

I havent had time to look closely at every single one of them, but I didnt spot anything too interesting upon initial inspection.

There were however a number of additional images similar to the one we previously found that shows clouds of material escaping from reactor 2 on March 15th. (see 3rd zip file for these). A few similar shots taken a few days later in zip number 8.

Zip 16 appears to contain many shots of the attempted water spraying at night of reactor 3, a video of which had long ago caused some confusion here about the target due to the side of the building they were attempting it from. Zip 11 contains shots from a similar mission conducted in daytime a day or two earlier, the last shot of which is one of the highest resolution/sharpest photos of reactor 3 building damage that I've seen.

Zip 20 contains some more shots of the March 21st reactor 3 smoke event.

There may be others that interest people, these were just the ones that immediately caught my eye. But I expect they would have been more interesting if we had been able to see them closer to the time they were taken, rather than all this time later.

http://photo.tepco.co.jp/en/date/201...30201-01e.html

jim hardy

If they announced finding those data last fall I must've missed it.
I followed jstolfi's plots.

From your exskf aeticle:
so it had been misplaced, overlooked, or dismissed ?
Not a criticism of TEPCO, just that's how things go when you're investigating such messes. They're puzzles, one gets pieces of information that don't fit and it takes a long time to make sense of it all. Been there, done that. Glad to hear they're still working on it.

Well, yeah..
If my memory is any good,
that's around the time they measured a few neutrons at the gate.
Direction of breeze was variable.
Might have vented some unexpected soot.

Ever watch Detective Columbo piece together his mysteries?


old jim

tsutsuji

The 4U-N01 and 4U-N02 samples are from the rubble found in the fresh fuel assemblies removed from SFP 4 last summer : http://www.tepco.co.jp/en/nu/fukushi...20828_01-e.pdf

4U-N01 is from the rubble collected by filtering the water in a cloth after washing the fuel ;

4U-N02 is from the rubble found between the rods after removing the channel box(es).

LabratSR

TEPCO releases document that answers questions about the use of the harbor at Fukushima.

http://www.tepco.co.jp/en/nu/fukushi...30327_01-e.pdf

tsutsuji

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tsutsuji

http://www3.nhk.or.jp/news/genpatsu-...330/index.html The multinuclide removal facility's test run using real highly contaminated water will begin on 30 March. The facility can remove 62 kinds of radioactive substances. The test run had been planned for last September, but it incurred a 6 month delay caused by a number of problems such as finding that the containers were not strong enough. The NRA approved Tepco's countermeasures last week. At first only the first one of the 3 lines shall be tested. The test is expected to take 4 months. As there are two other lines to test next, there is no prospect that normal operation can start within 2013 as originally planned. Including the groundwater that seeps in, 400 tons of contaminated water are produced everyday at Fukushima Daiichi.

http://www.tepco.co.jp/en/nu/fukushi...30329_01-e.pdf Overview of the Multi-nuclide Removal Equipment (ALPS) at Fukushima Daiichi Nuclear Power Station