Dry Vent of Reactor 2 May Have Released Largest Amount of Radioactive Materials, Not Explosions

The paper by a Tokyo University researcher that was finally published nearly one year after he took the samples at the front gate of Fukushima I Nuclear Power Plant and in Iitate-mura in Fukushima Prefecture (see my post from yesterday) has this very interesting chart.

It shows the spacial dose of radiation at the front gate of Fukushima I Nuke Plant and the timeline of events at the plant in March. The largest spike seems to be around or after 12AM on March 15, and the label on the spike says "Dry vent at reactor no.2".

On checking the information from March 2011, I find that TEPCO did the dry vent at Reactor 2 at 12AM on March 15, 2011 for a few minutes. At first (on March 20), TEPCO announced they'd done the dry vent sometime on March 16 and 17, but on March 21 retracted that statement and said the dry vent was done at 12AM on March 15. (See Sankei Shinbun article on 3/21/2011.)

It is not clear whether the company informed the residents or the government before the the Reactor 2 dry vent on March 15 which caused a huge spike in radiation, and which may be the biggest contributor to radiation contamination in wide areas in Tohoku and Kanto. From the Sankei article it doesn't look like they gave any prior notice. This is the same company that didn't even tell the plant workers that the vent on Reactor 1 was about to be carried out on March 12.

Dry vent releases different types of radioactive materials compared to wet vent.

The peak that appears to the right side of the largest peak is after the hydrogen explosion of Reactor 4, but not at the time of explosion. I suspect the peak may have been the result of some event on Reactor 2's Suppression Chamber which seems to have taken place about the same time as the Reactor 4 hydrogen explosion. TEPCO says it was not "explosion" that happened at the Reactor 2 Suppression Chamber but still doesn't say what it was.

The second largest peak was when the fire broke out on Reactor 3 on March 16. The white smoke was seen at 8:30AM on March 16, and the radiation level at the front gate of the plant shot up to 10,000 microsieverts/hour (10 millisievert/hour) at 10:40AM (Asahi Shinbun 3/16/2011).

Again, it is just too bad that the researcher had to sit on the data for 11 months for his article to be published in a peer-review magazine.

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#Fukushima I Nuke Plant: Workers Knew About the Extremely High Radiation Around Exhaust Stack

They may not have known the exact number (well, for that matter, no one knows because the survey meter went overscale at 10 sieverts/hr), but they've been running past the area when they have to enter Reactor 1 building to install the external heat exchanger to the Spent Fuel Pool, according to the tweets by a worker currently at Fukushima I Nuclear Power Plant.

So much for TEPCO's word that "there is no work planned near the area, and there will be no effect on the progress of the work at the plant", which is technically correct, at least the first half.

There may not be any work planned in the area there, BECAUSE RADIATION IS TOO HIGH. There may be no work planned there, but the workers have to go near it to enter the Reactor 1 building. The radiation is so high that the workers, with all their full protection gear and equipment and construction materials they carry, have been running past the area in order to minimize radiation exposure.

So it's been known.

More information from his tweets:

(Someone asked if it's true that TEPCO does not have the survey meter that can measure more than 10 sievert/hr radiation.) I think that's correct. We do have the instrument to measure the radiation of the nuclear fuel rods, but I wonder what happened to that. Broke?

(Referring to the area where over 10 sievert/hr radiation has been detected,) the radiation level around the exhaust stacks has been too high to even go near, ever since the accident started. Not just the area around the stack for Reactors 1 and 2, but also the stack for Reactors 3 and 4.

Debris are removed by shielded heavy equipment or remote-controlled equipment. That (10+ sievert/hr) spot was found during such operation.

We have to run when we go by the stack to enter Reactor 1. That's hard work. My legs hurt already from climbing up and down the stairs in the reactor building. Now I appreciate elevators!

All the elevators inside the reactor buildings at Fukushima I Nuke Plant are broken.

As to the worker who measured the radiation with the survey meter attached to a stick, Hiroaki Koide of Kyoto University says he must have spent only 1 or 2 seconds near the stack to get 4 millisieverts radiation.

Let's see. 2.78 millisieverts for one second, if the radiation was 10 sieverts/hr.

Koide thinks the radiation level is impossibly high to be coming from inside the duct or stack. He suspects there is a piece or two of the spent fuel blown out of the Spent Fuel Pool when Reactor 1 and Reactor 3 had hydrogen explosions.

He also says the protection suits that workers wear do nothing to protect them from gamma rays, unless they wear lead vests, but even then only marginally.

(For more of his comment, there's a transcript of the radio program that he appeared in, in Japanese.)

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Just In: Power Outage in Reactors 1 and 2 at #Fukushima I Nuke Plant, Nitrogen Injection Stopped

Kyodo News Japanese (3:52PM JST 6/8/2011):

　東京電力によると、８日午後、福島第１原発１、２号機で停電が発生、中央制御室の照明が消えた。ほかにも、１号機への窒素供給装置やモニタリングポストの一部が止まるなどの影響が出ており、同社が原因を調査している。

According to TEPCO, power went out in the afternoon on June 8 in the Reactors 1 and 2 at Fukushima I Nuclear Power Plant. The lights are out in the central control rooms. The nitrogen injection system in the Reactor 1 and some of the monitoring posts have stopped. TEPCO is investigating the cause.

A tweet from NHK's Science and Culture division says this about the nitrogen injection system:

停止というより、圧力が上昇したため窒素供給を待機中です

Rather, they halted the nitrogen injection because the pressure [inside the Containment Vessel] went up.

Minor electrical problem, I'm sure. Nothing to worry about. Besides, the Reactor 1's Containment Vessel has been breached. How could the pressure go up?

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