Fukushima Update - Temperature below 100 C

Update # 52: August 21, 2011

 by Nelle Maxey

As reported at NHK this morning, two of the government's plans to lift contamination bans have had to be scraped.

Evacuation orders to remain in effect

"The government has decided to have Prime Minister Naoto Kan explain to municipalities near the Fukushima Daiichi plant that exclusion orders in some areas will remain in effect due to high levels of radiation.

The government had planned to consider lifting exclusion orders within 20 kilometers from the plant after cold shutdown of the reactors has been achieved.

However, it has decided to keep off-limits the areas where it is not safe for people to return home for a long time.

Areas subject to the measure are those quite close to the plant and where radiation levels remain very high.

The government will arrange for Kan to explain to affected municipalities that exclusion orders will likely remain in effect for a long time and about how the government will support the former residents.

The government's nuclear accident task force indicated on August 9 that some areas are likely to be too contaminated for people to return home for a long time.

It plans to work with local municipalities to decide on long-term measures and plans for reconstruction." Sunday, August 21, 2011 16:44 +0900 (JST)

More contaminated cows from Fukushima

"Beef from 5 more cows from a Fukushima farm has been found to be contaminated with radioactive cesium in excess of the government-set safety limit.

The revelation by Fukushima Prefecture on Saturday followed reports one day earlier that beef from 4 cows from the same farm had been found to contain radioactive cesium twice the safety standard.

This prompted the central government on Friday to put off lifting a shipment ban on Fukushima beef…." Sunday, August 21, 2011 08:58 +0900 (JST)

Here is SKF on the cattle issue:

4,000 Potentially Radioactive Cows Without Radioactive Rice Hay May Have Been Shipped from One Farm in Namie-Machi, Fukushima

"Radioactive beef from Fukushima meat cows (then Miyagi, then Iwate, then…) was first in the news in early July. Then, the culprit was very quickly identified as radioactive rice hay that was stored outside when Fukushima I Nuke Plant started to spew out radioactive materials.

First they said the rice hay was fed to the cows because there was nothing else to feed due to supply disruption after the March 11 earthquake. Then it turned out that rice hay was integral part of fattening the meat cows before they were sold to the market.

Then the news broke on August 19 that some meat cows from Fukushima were highly radioactive even without radioactive rice hay.

And then it turns out that 4,000 such cows may have been shipped from one cattle farm in Namie-machi alone since the accident. The radiation level on the farm is high…."

Also here's another Japanese news story on the first 4 cattle found. Note that "reputation" and "rumour" are the concerns in this article, not public safety.

Fukushima officials worry new discovery of radioactive beef will harm reputation more

FUKUSHIMA — Officials here are disappointed that a new discovery of radioactive beef shipped from a Fukushima Prefecture farmer was discovered and caused the central government to delay lifting the ban on the prefecture's cattle shipments.

"Fukushima products have taken another blow to their reputation," said an official….

The other stories at NHK today concern the plant site.

The first, announces the temperatures at Unit 1 being below 100°C. It was previously reported the temperature at the bottom of the reactor pressure vessel (RPV) was below 100°C, however now the top of the RPV and 9 other temperature sensors are being reported as below the 100° C level. I have no idea where the other sensors are located, as only the the top and bottom of the RPV are reported on a daily basis in public records that I can find.

TEPCO: No1 reactor temperature down

"The operator of the Fukushima Daiichi nuclear power plant says all thermometers at the troubled No.1 reactor has registered temperatures lower than 100 degrees Celsius.

Tokyo Electric Power Company, or TEPCO, said on Saturday that all 19 thermometers at the No.1 reactor showed readings below 100 degrees as of 11 PM on Friday. It added the stable condition was unchanged 12 hours later.

As part of its effort to bring the plant under control, TEPCO has been working to achieve cold shutdown of reactors No.1, 2 and 3. The reactors' temperatures should continuously remain below 100 degrees…." Sunday, August 21, 2011 08:58 +0900 (JST)

While it is good news that the temperatures recorded in Unit 1 are below 100°C, it is less meaningful than one may suppose at first glance.

First, as has been pointed out previously, we don't know if the temperature reduction is due to the melted core moving down into the earth away from the reactor pressure vessel as it melts through the concrete floor of the "dry well". In other words, the heat source moving away from the temperature sensors.

Second, TEPCO is talking about a 12-hour interval as though that represents a "stable" reduction in temperature.

The temperature towards the top of the reactor vessel where water is being injected is labeled A below. This temperature has dropped 4.2°C since Friday's measurement. The temperature at the bottom of the reactor vessel (which we know the fuel core has burned through) has dropped 2.1°C since Friday (but has been below 100°C for about two weeks.)

Unit 1:

Date A B

8/21 97.6 90.4

8/20 98.2 91

8/19 101.8 92.5

8/18 102.3 93

8/17 102.4 93

8/16 102.4 93.1

8/15 102.5 93.3

Third, one month intervals show the temperature change required to bring Unit 1 to below 100° (at both the top and the bottom of the reactor vessel) has always been a matter of less than 20° C. See a comparison to Unit 2 and Unit 3 below.

Date A B

8/14 103.1 93.8

7/14 117 102.8

6/14 112.8 97.6

5/14 114.5 90.4

It is readily apparent looking at the monthly interval data that choosing a 12-hour interval to claim successful stabilization may be a bit premature since the temperature has fluctuated up and down significantly in the past: down from mid May to mid June, Up from mid June to mid July, down from mid July to mid Aug.

We can only hope the downward trend continues.

I have been collecting temperature and water injection rate data and looking at it every day. Here is the comparative data from Unit 2 and 3.

Unit 2 is operating at the highest overall temperature of the 3 units. It looks like this today, August 21

A: 107.2℃

B: 114.5℃

Compared to the temperatures on Aug 1

A: 111.7 ℃

B: 123℃

So the top of the RPV temperature has dropped 4.5° this month and the bottom of the RPV temperature has dropped 8.5°C.

However, looking at the monthly interval data since May, we see an overall temperature reduction of 7.3°C in the top of the RPV and a temperature INCREASE at the bottom of the RPV of 4.1°C. This increase occurred in July and has still not been reduced to the mid May temperature level.

Is this due to the "ongoing re-criticality" that are spoken of? That is, the fuel calming down and then being re-excited to emit more radioactivity?

Again I don't know.

Date A B

8/14 108.5 115.4

7/14 111.6 125.3

6/14 108.2 107.6

5/14 114.5 111.3

Unit 3 is different in all respects from Units 1 & 2.

Remember this is the reactor with the MOX fuel and it is also the one that suffered the largest explosion.

First, the temperature at the top of the RPV has always been recorded as higher than at the bottom of the RPV. I have seen no explanation or discussion of this anywhere.

Unit 3 is also requiring approximately 2.5 times the amount of injected water to keep it cool compared to the other 2 units.

And it operated at the highest temperatures until the last month when the RPV temperatures dropped below those of Unit 2.

TEPCO said recently they will reduce cooling water flow into Unit 3 from 9 cubic meters/hr to (eventually they hope) 3 cubic meters/hr.

However, the temperature is already RISING as they reduced the water over the last couple of days by 1 cubic meter/hr (from 9.0 to 8.0).

This does not bode well for their plan.

Unit 3

Date A B

8/21 108.8 104.8

8/20 107.8 103.8

8/19 107.1 104.1

8/18 106.2 103.9

Looking at the overall reduction in temperature over the 4 months from mid May to Mid August we see a much larger reduction in temperature than in Units 1 & 2.

8/14 107.7 104.2

5/14 165 151.5

At the top of the RPV, the temperature has been reduced by 57.3°C

At the bottom of the RPV, the temperature has been reduced by 47.3°C.

Looking at the monthly intervals, the top of the RPV temperature has steadily declined, but the bottom of the RPV fluctuated up in mid june and then down in both mid july and mid August.

8/14 107.7 104.2

7/14 148.9 116.5

6/14 150.1 165.9

5/14 165 151.5

Perhaps these comparisons are meaningless. I just don't know. Though I hope someone out there in the blog-o-sphere will comment.

What I do know is that TEPCO is cherry-picking information for press releases and that they either do not know why the various temperature anomalies exist or they aren't releasing the information if they do know.

I forwarded an SKF comment on this story yesterday titled, SARRY joins the under-performers. See that post for details on this story.

New system improves Fukushima decontamination

"Tokyo Electric Power Company says it has succeeded in increasing the capacity of a water decontamination system at the Fukushima Daiichi nuclear power plant by 1.5 times.

The utility began to use a Japanese-made system on Thursday along with a French-made system to remove radioactive substances from water. The water is then being injected back into the reactors to cool them.

TEPCO decided to introduce the new system as the existing decontamination system was plagued with problems, and the foreign-made components repeatedly clogged up…." Sunday, August 21, 2011 01:59 +0900 (JST)

Here is an interesting article from Asahi. Don't hold your breathe though about learning the levels of radioactive materials in the melted fuel rods. It will be at least 4 years according to this article before TEPCO develops the techniques for testing the levels of plutonium, urnaium and other nuclear substances in each reactor's melting fuel rods. As reported previously it will be at least 10 years (some say 20) before the fuel rods can be removed.

Nonproliferation rules require tests on Fukushima fuel

August 19, 2011

By Hisae Sato/Staff Writer

"The government will spend about 600 million yen ($7.84 million) developing tests to comply with the International Atomic Energy Agency rules that require Japan to identify levels of plutonium, uranium and other nuclear substances in the damaged fuel rods at the Fukushima No. 1 nuclear power plant.

The accident is believed to have left a mess of highly radioactive material in the No.1 to No. 3 reactors, with fuel rods and rod cases melting and reforming into disparate particles and lumps.

But IAEA rules insist that Japan will have to specify exactly how much radioactive substances have been left if the substances are removed from the reactors. That has never been done and will require new testing techniques…." 

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