Fukushima No. 1 loss of coolant due to earthquake 7

[electricpete]

It is kind of odd that I134 is more than 100x higher than anything else on the chart. Yet since it has a short half-life, it must have been created by decay recently. You'd think the activity of the parent isotope of I134 (whatever it is) would show up in comparable concentration but there is nothing comparable to I134 in concentration.

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[electricpete]

I guess the I134 is probably a bogus number (awaiting more info).

Officials at Japan's stricken Fukushima Daiichi nuclear plant late Sunday retracted their announcement that they had found puddles at the facility's No. 2 reactor containing 10 million times more radioactivity than would be found in water in a normally functioning nuclear reactor.

"The number is not credible," Tokyo Electric Power Co. spokesman Takashi Kurita, said, according to the Associated Press. "We are very sorry."

It was not immediately clear what led to the inaccurate reading of the water, or what the real level was. The company said on its website that there was a "mistake in the assessment of the measurement of iodine-134."

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[trottiey]

The revised results are out:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110327e15.pdf

So you would actually have to drink a tumbler or so of the stuff to guarantee death. Or go wading through it for a few hours.

I've got to say I'm relieved. Not because of the toxicity level, but because the presence of any significant amount of I-134 would have indicated very bad stuff about the internal state of that reactor.

 

[unclesyd]

The news is reporting all manner of difficulties at the site along with another earthquake (6.5). The can't pump the highly radioactive water from the turbine building as there is no place to put it. The sea level radioactivity around the plant is rising. To top this off there are reports of radioactive rain on the US East Cost, no mention of levels other than it's safe.

The reports of rain showing radioactivity got me to thinking about what levels of radioactivity were seen in rainwater during the atmospheric testing era. In reality it may not have been measured design as the instrument's of the day with any accuracy were lab instruments and quite bulky. For measuring low levels of radioactivity the "Cutie Pie"" was about the only thing outside the labs. I remember going to class on the operation of the meter we were told to always keep the polyethylene cap on the meter due to high levels of Beta Radiation occasionally seen.

 

[MintJulep]

"under the limit"

What limit?

 

[unclesyd]

Isn't the Iodine Isotope I ^-131 instead of I ^-134

 

[electricpete]

The link 27 Mar 11 19:15 lists 3 isotopes of Iodine. I assume they are all fission products or decay daughters of fission products. For example certain isiotopes Tellurium (52 protons) can beta decay to Iodine (53 protons)


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[trottiey]

There are at least 5 isotopes of iodine with any semblance of stability. Iodine-131 is generally the isotope of most concern to health because its half life is 8 days - short enough to be highly radioactive, but long enough to find a human being and infiltrate it.

Iodine-134 only has a half-life of 53 minutes, and it is not a decay daughter of any long-life fission product. Therefore the presence of iodine-134, if it had been real, would have indicated that the reactor resumed criticality in the last few days, and/or that some new physics was taking place. Very unexpected and very bad. But it was just a lab error.

 

[electricpete]

A gloomy interpretation of events is that Unit 2 fuel has melted through the reactor vessel, and unit 2 containment is also breached from the hydrogen explosion:

http://www.guardian.co.uk/world/2011/mar/29/japan-lost-race-save-nuclear-reactor

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[MintJulep]

I also noted that article states that the drywell has been flooded.

Earlier I saw some news agency's cartoon animation showing that the drywell had been flooded, but discounted it in light of a preponderance of reports suggesting that seawater was being introduced to the reactor vessel only.

 

[cloa]

Given the desperation of the water flooding and difficulties in access, a lot of water probably missed its desired targets so where would spilled water have gone?

 

[mauner]

How can you determine that fuel has melted through the reactor vessel based on radiation levels?

What does the RPV provide 4" steel = 1/10 thickness?

Does anyone know the contact raditation reading for a spent fuel bundel out of water?

Could abnormal radiation levels occur due to a shift in the fuel when it melted to the bottom of the vessel?

What about the CRDM's and the undervessel support structure?

 

[electricpete]

What does the RPV provide 4" steel = 1/10 thickness?

If you're talking about shielding for gamma's, the rule I remember is 1" steel reduced to 1/10. So 4" would reduce gamma radiation to 0.0001. I'm sure it depends on gamma energy

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[electricpete]

How can you determine that fuel has melted through the reactor vessel based on radiation levels?

I assume the conclusions came from not only review of radiation levels but review of isotope levels present in the water of turbine building and in the ditch. I guess maybe (?) they suggest a direct path from melted fuel to the outside.

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[electricpete]

If you're talking about shielding for gamma's, the rule I remember is 1" steel reduced to 1/10. So 4" would reduce gamma radiation to 0.0001. I'm sure it depends on gamma energy

Whoops, I was wrong ....you were right. 2" of lead of 4" of steel or 24" of water is about a tenth thickness.


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[electricpete]

I would also mention that if you google Richard Lahey cited in the link above, you'll see he is no slouch. He was very involved in BWR development at GE and remains very involved in advanced nuclear technology development today. One caveat I would mention is that his words are paraphrased in tha that link by a journalist, I would like to see what he wrote directly.

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[electricpete]

I guess maybe (?) they suggest a direct path from melted fuel to the outside.

Well, I guess it is obvious there must be some path when fission products show up outside. But perhaps the ratio of the isotopes gives some idea about the path. For example, certain isotopes travel as gas, certain are water soluble, certain travel only as particles etc.

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[electricpete]

Correction: "certain isotopes" should've been "certain elements". (it is generally not the specific isotope, but the specific element that is relevant for transfer mechanisms).

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[cloa]

Naturally- if its Radon assuming its one of isotopes that has a half life long enough for the small quantities to get out then it escape as a gas.

 

[cloa]

Does anyone know what radiation protection clothing that Fukushima workers are using- since I heard of a company that produces clothing that is an effective as lead plates but actually wearable?