#Fukushima I NPP: TEPCO Admits Error 7 Months Later, Says All-Beta from Observation Hole Along Embankment Was 10 Million Bq/L, Not 900K Bq/L

(UPDATE) It may not just be about groundwater samples along the embankment. All the high-density all-beta/strontium analyses done at Fukushima I NPP, including the analyses of all-beta/strontium in the RO (reverse osmosis) waste water, may be wrong. Or TEPCO says they "cannot deny the possibility that the analyses were wrong." (from a tweet by @jaikoman who tweets just about every single TEPCO and NRA press conference)

Jiji Tsushin just reported the same thing. The information is from the press conference on February 7, 2014.

For more information about the RO waste water leak of August 2013, go to this link.

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Of that, strontium-90 alone turned out to be 5 million Bq/L. The reason (excuse)? Wrong measurement method used. Or something to that extent that even people who know a lot about nuclide analysis are scratching their heads trying to figure out how that happened.

Yomiuri Shinbun has the best summary of the situation (2/7/2014):

力は６日、福島第一原子力発電所の護岸にある観測用の井戸の一つで、昨年７月５日に採取した地下水から、放射性ストロンチウムが１リットル当たり５００万ベクレル検出されたと発表した。

On February 6, TEPCO announced that 5 million Bq/Liter of radioactive strontium was detected from the groundwater sample taken on June 5 last year from one of the observation wells on the embankment of Fukushima I Nuclear Power Plant [the embankment is located between the turbine buildings and the plant harbor].

国の放出基準の１６万倍以上で、地下水の過去最高値（１リットル当たり５１００ベクレル）の約１０００倍に上った。東電はこの約半年間、ストロンチウム単独の濃度は「測定結果が誤っている可能性がある」として公表していなかった。

The density is 160,000 times that of the legal limit for release into the ocean, and it is about 1,000 times that of the highest density in the groundwater that had been measured so far (5,100 Bq/L). TEPCO didn't disclose the result of measurement of strontium alone, as the company believed there was a possibility that the result of measurement was wrong.

東電は今回の地下水について、採取直後の昨年７月、ストロンチウムを含む様々な放射性物質の総量（全ベータ）を同９０万ベクレルと発表していた。東電は６日、「高濃度の全ベータは測定上限を超え、軒並み過小評価していた」と説明。この地下水の実際の全ベータは同約１０００万ベクレルとの見方を示した。最近は、高濃度の場合は薄めて分析する方法に変えているという。

As to this particular sample, TEPCO had announced on July last year that the sample had contained 900,000 Bq/L of all-beta including strontium. On February 6, TEPCO explained that they had "underestimated all of the results of high-density all-beta, which [in fact] exceeded the upper limit of measurement." This particular sample may contain about 10 million Bq/L of all-beta, according to TEPCO. The company recently switched to a different method of analysis that uses diluted samples when the density of radioactive materials is high.

So this is the lowdown of the case of strontium more abundant than all-beta, all thanks to the faulty measurement by TEPCO.

Browsing through the documents released by TEPCO, the particular observation hole was No.1-2, which is no longer used as the result of waterglass injection into the soil in the embankment. It is close to where the extremely contaminated water from Reactor 2 turbine building had been found leaking in April 2011 (via the underground electrical trenches).

From TEPCO's document for the press (2/6/2014; English label is by me), the location of No.1-2 observation hole:

TEPCO inserted the newly disclosed 5 million Bq/L for strontium-90 but the number for all-beta remains uncorrected, at 900,000 Bq/L (which TEPCO now says 10 million Bq/L instead):

10,000,000 Bq/L of all-beta, or 10,000 Bq/cubic centimeter of all-beta. That's the same order of magnitude of all-beta in the water that gets contaminated after circulating through the reactors (see my September 2013 post), but the levels of cesium-134 and cesium-137 in this sample water is too low for this water to be the contaminated water that is currently circulating the reactors.

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