Update #63: Sept 22 & 23
At the Plant Site
Before we go to our first story, I need to correct an assumption I made regarding the gas decontamination systems that TEPCO announced a few days ago. I thought they were talking about filtering the radioactive gas out of the vent systems. This not the case at all.
What they intend to do is, as TEPCO puts it, "install a facility to maintain the PCV pressure at around atmospheric so as to reduce the leak of radioactive materials from the vessel after RPV bottom temperatures going down below 100 degrees C." Since I haven't read any details about this "facility" they are intending to install, I'm not sure what the technical information is. All do know is that they must cut a pipe leading out of the reactor to install it. That is what they were preparing for yesterday when they discovered the pipe at Unit 1 had higher than expected concentrations of hydrogen.
So the big story today concerns that hydrogen gas which has been detected in a pipe at Unit 1. Its presence is not unexpected since hydrogen is produced when ionizing radiation comes in contact with water as is currently going on in the reactors which are in meltdown. This is why nitrogen has been injected into the reactors for months. The nitrogen binds oxygen and reduces the chances of explosion since hydrogen and oxygen are required for a hydrogen explosion to occur.
However, the concentration of more than 1% was apparently a surprise to TEPCO. Yomiuri Shimbun carried the article below yesterday, which explains the situation.
As you see by the comments from SKF and Physics Forum which follow the Yomiuri story, not everyone is as sanguine about the hydrogen as TEPCO is.
Hydrogen detected in pipe at Fukushima No. 1 reactor
Hydrogen has been detected in a pipe at the No. 1 reactor at the Fukushima No. 1 nuclear power plant, but there is no possibility it will cause an explosion "in the immediate future," the plant's operator said Friday.
According to Tokyo Electric Power Co., hydrogen of at least 10,000 parts per million was detected at two spots in a pipe passing through the containment vessel on the reactor building's first floor. This concentration was higher than TEPCO had anticipated.
Although TEPCO is not certain how much hydrogen is still inside the vessel, the utility believes it is possible the concentration of the highly flammable gas is higher than had been assumed.
In air and liquid, 10,000 ppm is equivalent to 1 percent. Air containing at least 4 percent hydrogen and 5 percent oxygen is at risk of causing explosion.
TEPCO has been injecting nitrogen into the containment vessel since April so it is assumed there is virtually no oxygen. As a result, the utility ruled out the possibility of an explosion "in the immediate future."
The hydrogen was detected during an examination of the pipe before installation of a radioactive gas purification system inside the containment vessel. TEPCO said it had closely examined the hydrogen concentration and would inject nitrogen into the pipe to flush out the remaining hydrogen.
TEPCO said it had expected hydrogen would still be inside the containment vessel, but that it would have no effect on the radioactive gas purification system.
The nuclear plant's Nos. 1, 3 and 4 reactors were damaged by hydrogen explosions in the days after the March 11 earthquake and tsunami knocked out the plant's cooling systems.
Physics Forum has some comments on this posted today
Originally Posted by tsutsuji
- The upper detection limit of the instrument (1%) being reached, the actual hydrogen concentration is unknown.
- Tepco explains that because the oxygen concentration is low, "the probability of a hydrogen explosion is extremely low".
I hope I'm not the only one who sees a bit of an issue here. Am I?"
This update was posted today at SKF.
It Is More Than 40,000 ppm Hydrogen Gas, not 10,000 ppm Inside Reactor 1 CV Pipe
Just last night I reported on the hydrogen gas detected inside the pipe leading to the Reactor 1 Containment Vessel. TEPCO, according to the report and by their own press conference, said the density was "over 10,000 ppm".
Well. It was an understatement if the worker who tweets from Fukushima I Nuke Plant is correct. He says they went back to test the locations again with the meter that can measure up to 40,000 ppm. The meter maxed out. It is over 40,000 ppm, or over 4%.
The media and TEPCO reported the number as "over 10,000 ppm", which is technically correct. "Over 40,000 ppm" is definitely over 10,000 ppm.
The worker tweeted: [Japanese characters removed]
And today [September 23; they knew about "over 10,000 ppm" the day before] we went to measure using the meter that can measure up to 4%. It was 4% max. So the work [to cut the pipe] was cancelled, and TEPCO made an announcement.
I didn't know, as I'm not very knowledgeable about chemistry, but it seems there's a chance of explosion if hydrogen gas is more than 4%.
SKF continues:
"He is wondering if zirconium cladding is still melting and reacting, producing hydrogen.
But as one reader of this blog points out after putting two posts from yesterday together (the one about Reactor 4 SFP water radiolysis and the one about the hydrogen detection in the Reactor 1 CV pipe), it may be possible that the water radiolysis is happening somewhere deep inside the reactor building where boiling water is getting irradiated and generating hydrogen gas."
So the upshot of all this is that of course they couldn't cut the pipe since a 4% concentration of hydrogen could explode when it came into contact with the oxygen in the air.
What it means to the stability of the reactors is a whole other question on which I will keep you informed as details become available.
Contamination
Now here is an interesting story from SKF considering the on-going problem with the amount of radioactive contaminated water at the plant site. Thursday, September 22, 2011
TEPCO To Sprinkle Low-Contamination Water from Reactor 5 and 6 Turbine Bldgs in the Fuku I Compound after they treat the water to remove as much radioactive materials and salt as possible from the water.
TEPCO seems to be running out of storage space for contaminated water, and at the same time is worried that the wood piles may catch fire after the trees were cut down to make room for storage facilities on the west side of the plant.
From Yomiuri Shinbun (9/22/2011):
- TEPCO disclosed the plan on September 22 to treat the low-contamination water and sprinkle the treated water in the Fukushima I Nuke Plant compound. The low-contamination water came from Reactors 5 and 6, and is currently stored in temporary storage facilities.
The company says there will be hardly any effect to the surrounding environment, but there may be objections from the local municipalities.
- In Reactors 5 and 6, a large amount of seawater flowed into the turbine buildings and other buildings when the tsumani hit. In addition, rainwater and the groundwater have seeped in. TEPCO has been transferring this low-contamination water to the temporary storage tanks and to the "Megafloat", and there are currently 16,350 tonnes.
Tepco has been clearing the forest inside the compound in order to set up the temporary storage tanks. The company is planning to sprinkle the treated water on the wood piles and the surrounding areas to prevent the wood piles from catching fire and to suppress the dust. The water will be treated to reduce the density of radioactive materials to the level allowed for the ocean bathing (50 becquerels/liter and below for radioactive cesium), and be desalinated.
Asahi Shinbun has the information on how "low" the contamination is in this water, and it is 0.01 becquerel/ milliliter (= cubic centimeter). So, in one liter the density is 10 becquerels/liter. If both newspapers are right, then TEPCO will only have to do the desalination.
Comments to this story on SKF from readers:
"This to me was the most bizarre story to come out of Tepco in a while. The latest typhoon just dumped huge amounts of water all over Japan. There is absolutely no need to spread water around to reduce fire risk. They are actually increasing the fallout level by doing this. I'm OK with the idea of turning Fukushima Daiichi into a nuclear waste site (let's face it, it already is) so storing the water there is OK with me, but spreading it around the site to "reduce fire risk"?? Facepalm."
"I'm sure none of this will impact the fantasy road map TEPCO has been dreaming about. I'm surprised they don't just make another ocean dump like they did in the early days of the disaster. At 10 Bq/L this water could be sold as a health drink in Japan. Fire suppression could be done by selling the wood to coffin makers for super eco-points. Maybe they can give TEPCO eco-points for "sprinkling" the water instead of just dumping it."
NHK reported yesterday that
Radioactive iodine spread south of nuclear plant
A Japanese government survey shows that radioactive iodine emitted from the Fukushima Daiichi nuclear plant spread not only northwestward but also to the south of the plant.
The science ministry sampled soil at 2,200 locations, mostly in Fukushima Prefecture, in June and July, and created a map indicating the extent of the radioactive contamination as of June 14th.
Officials were able to obtain data for iodine 131 at only 400 locations, because of its short half-life of 8 days.
The latest map shows that iodine 131 spread northwest of the plant, just like cesium 137 as indicated on an earlier map. But the substance was also confirmed south of the plant at relatively high levels.
The researchers found that accumulation levels of iodine 131 were higher than those of cesium 137 in coastal areas south of the plant.
Ministry officials say clouds that moved southward over the plant apparently caught large amounts of iodine 131 that were emitted at the time.
Iodine 131 could cause thyroid cancer through internal exposure. The ministry is therefore trying to determine at what levels the substance spread immediately after the accident at the plant in March.
So the upshot of this story is the Japanese government is (in a round-about way) finally admitting that children in Tokyo and others areas south of the plant are at risk for thyroid cancer, just like Dr. Busby has been saying. To bad it is well past time the do anything much about it!
Remember the yellow rain in Tokyo last March after the explosions?
ENENews carries unconfirmed reports today that yellow rain occurred in North Kanto following the typhoon.
ENENews also carries this rather odd story where an international organization is restricting teams participating in the MotoCross event being held in Japan from taking their own food.
Just like the government did with school lunches.
IRTA restricts MotoGP teams from taking personal food supply to Japan
MotoGP news, September 23, 2011:
"International Racing Teams Association (IRTA) has warned the MotoGP teams not to carry any type of food items to Japan.
The teams are conscious about the nuclear radiation at the surroundings of the Twin Ring Motegi circuit [100 km from meltdowns]. […]
In order to be cautious, many teams requested to take their personal food supply to Japan. However, the IRTA issue an order which read, "We have been asked by Dorna to inform you that you should not pack food with your freight. Discovery by the Japanese Customs could result in delays or penalties imposed by the Japanese authorities." […]
The IRTA document further stated as, "We repeat that, in our opinion, transport of food is unnecessary. Government agencies have not issued any general warnings about food consumption. Furthermore the independent report commissioned by Dorna reported on sampling and testing of many types of food at Motegi and the surrounding area and found absolutely no problems.
This Canadian story was reported earlier in the week at ENENews. Here is the original story from an online First Nations news source,
Fish Tests Radiation Negative, But Where's It From
The Canadian Food Inspection Agency (CIFA) has deemed fish tested in the wake of the Japan nuclear disaster as radiation free, but will not divulge where samples were taken from.
According to the CFIA, results from 12 fish samples showed minimal detectable levels of the radioactive particles Cesium -134 and Cesium -137. The results are below Health Canada's "actionable levels," said CFIA spokesperson Mark Clarke. The CFIA released the results of its tests on Friday, September 16.
West Coast salmon migration routes are near waters that are feared contaminated with radioactive fallout from the nuclear reactor that was damaged by the earthquake and subsequent tsunami in Japan last spring. The agency did not answer repeated questions about where the samples were taken from in B.C., saying only that they were came from various processing stations.
The testing was done just as a precaution, authorities said. They had not expected to find anything. They waited till now because, although the twin disasters happened in March, the fish did not return to spawn until now.
Stó:lō Tribal Council fisheries advisor Ernie Crey said he is puzzled at the agency's reticence about where the fish were taken from.
There have been a plethora of papers released this week in connection with the various safety conferences.
Here are two important ones from the conference in Japan which are reported on at SKF.
Go to the links to read the summary discussions of the papers and questions which arise.
There are some good discussions in the readers comments too.
This about the explosion in the Spent Fuel Pool in Unit 4 which TEPCO never satisfactorily explained.
This one concerns the fact that the earthquake was responsible for the damage in Reactor 2. The explosion in reactor 2 occurred in the wet well (torus) well down in the basement of the plant. This is why there were no photos like the other explosions . . . only reports of a noise.