(UPDATED with Wind Direction/Speed Info) Mysterious Dust at #Fukushima I Nuke Plant Update: Where Did It Come From?

(UPDATE 8/20/2013) TEPCO keeps records of wind direction at the West Gate, which is close to Monitoring Post 5. For August 19, 2013, wind was from:

9:30AM: south-east, 2.2m/s
9:40AM: south-south-east, 2.2m/s
9:50AM: south-east, 2.3m/s
10:00AM: south-south-east, 2.9m/s
10:10AM: south-south-east, 3.5m/s

In other words, the Anti-Seismic Building was more or less directly down-wind from Reactors 1, 2 and 3.

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This is an update of the previous post on mysterious dust that contaminated workers waiting for bus on August 19, 2013.

On the second incident of workers contaminated with radioactive materials while waiting for the bus to take them to the Entry/Exit Checkpoint at the gate, TEPCO seems to have gotten a little bit more curious than in the first incident, and actually did something that may (or may not) be worthwhile in figuring out where the radioactive materials may be coming from.

First, the timeline (from TEPCO's handout for the press in Japanese, 8/19/2013):

9:29AM: "high" alarm sounded from the continuous dust monitoring system (outside)

9:34AM: "high" alarm sounded from the continuous dust monitoring system (inside)

9:50-10:10AM: dust sampling

10:04AM: "high-high" alarm sounded from the continuous dust monitoring system (inside)

10:12AM: announced that workers should put on masks in the areas that are exempt from wearing masks

10:20AM: two workers out of three (affiliate company) who boarded the bus in front of the Anti-Seismic Building at 9:55AM were found with contamination (13 Bq/cm2, 7 Bq/cm2)

10:57AM: the workers were decontaminated

13:00AM: the workers took WBC, found with no internal radiation exposure

Result of dust sampling in front of the Anti-Seismic Building, from 9:50-10:10AM:

• Cs-134: 2.6 x 10^-4 Bq/cm3 (2.6E-4, or 0.00026 Bq/cm3)

• Cs-137: 5.8 x 10^-4 Bq/cm3 (5.8E-4, or 0.00058 Bq/cm3)

Dust sampling at the location up-wind, about 2 hours later (at the extra-high-voltage switching station for Reactors 1 and 2), from TEPCO's alert for the press, 8/19/2013:

From 12:48PM to 1:08PM:

• Cs-134: 3.2 x 10^-5 Bq/cm3 (3.2E-5, or 0.000032 Bq/cm3)

• Cs-137: 7.2 x 10^-5 Bq/cm3 (7.2E-5, or 0.000072 Bq/cm3)

From 1:50PM to 2:10PM:

• Cs-134: 8.0 x 10^-6 Bq/cm3 (8.0E-6, or 0.000008 Bq/cm3)

• Cs-137: 2.1 x 10^-5 Bq/cm3 (2.1E-5, or 0.000021 Bq/cm3)

And where is this switching station located? Right behind Reactors 1 and 2, on a terrace.

From TEPCO's handout for the press on 10/19/2012 when there was a brush fire in the area near the switching station:

The location of the Anti-Seismic Building, Entry/Exit Control, and Switching Station (English labels are by me):

How about down-wind location? TEPCO even checked the monitoring station No.2 located down-wind from the Anti-Seismic Building. From the alert to the press, 8/19/2013:

"Monitoring Post No.2, located down-wind from the Anti-Seismic Building, didn't show significant change. However in order to closely examine the incident, we expanded the monitoring range by 1,000, and found the following rise in radiation levels":

• From 10AM to 10:20AM: rise of 42/1000 microsievert/hour

• From 1:30PM to 1:50PM: rise of 31/1000 microsievert/hour

*Normal monitoring: significant digits of 2.

また、免震重要棟の風下に設置されているモニタリングポスト－２の値について、有意な変動は確認されませんでしたが、事案についてより詳細な確認を行うため、測定レンジを1000倍に拡大して確認したところ、以下の時間帯で通常の監視桁数を下回る範囲での指示上昇が確認されました。
・午前10時00分から午前10時20分　42／1000［μSv/h］の上昇
・午後１時30分から午後１時50分　31／1000［μSv/h］の上昇
※通常の監視桁数はμSv/hの有効数字２桁

Where is the monitoring station No.2 located? (English labels and red circles added by me)

"Happy", the worker who's been tweeting from Fukushima I Nuke Plant since March 2011, said this yesterday:

免震棟前の汚染は、2号機と3号機の窒素封入作業時間の先日(12日)と本日の時系列を洗い出し、因果関係を調べた方がいいかも…。あと詳細な核種分析も…。

About the contamination in front of the Anti-Seismic Building, it may be a good idea to examine the timelines for both August 12 and today [August 19] of the nitrogen injection work in Reactors 2 and 3, and see if there is any causality. And do detailed nuclide analysis.

Speaking of nitrogen injection, TEPCO released the alpha-nuclide monitoring results from the gas management systems in Reactors 1, 2 and 3 on August 12, 2013, and 0.19 Bq/cm3 of all-alpha was found in the condensed water from the Reactor 3 system.

TEPCO recently did the gas management system sampling test of gamma nuclides (cesium iodine) for Reactor 2 and Reactor 3, but the samples were taken on August 7 and August 3 respectively, and the result was ND.

Contamination still remains a mystery.

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