TEPCO is starting nitrogen injection in unit 3 of the Fukushima-I nuclear power plant to guard against the risk of hydrogen explosions, but it initially faced the obstacle of high radiation levels on the first floor of the reactor, where it wanted to connect the nitrogen pipes. Levels as high as 180 mSv/h between the truck bay entrance on the south-west and the containment at the center made this a no-go area. Efforts by a robot to vacuum radioactive dust off the floor on June 2 were ineffective. TEPCO finally solved the problem by laying 1 cm thick steel sheets on the floor around where workers needed to access.
The ex-skf blog reports that this solution was addressing intense gamma radiation coming up from the basement, penetrating the reinforced concrete floor. The unit 3 reactor building basement was estimated by TEPCO to be flooded with 6400 tons of water, containing 1.5 million Becquerels of Cs-134 per cm3 (Bq/cm3) and 1.6 million Becquerels of Cs-137 per cm3 (Bq/cm3). That amounts to 9,600 Terabecquerels (TBq) of Cs-134 and 10,200 Tbq of Cs-137 or 19,800 TBq in total. Besides that there are other radioisotopes such as Iodine and Strontium.
Because the 1 cm of steel (and below that probably more than 10 cm of concrete) still leave too much radiation through, TEPCO is considering another layer of steel sheets now.
Meanwhile, NHK reported yesterday (July 10, 2011 07:33 JST):
The Tokyo Metropolitan government has begun tracing beef from 6 cows shipped from a Fukushima farm where 11 other cows were found contaminated with high levels of radioactive cesium.
On Friday, tests detected 1,530 to 3,200 becquerels per kilogram of cesium in beef from the 11 cows raised in Minami Soma city, about 20 kilometers from the crippled Fukushima Daiichi nuclear power plant. The national safety limit is 500 becquerels. Tokyo ordered the beef to be removed from distribution.
But beef from 6 cows shipped from the farm to
Tokyo and Tochigi in May and June are believed to have already made it to market without radiation testing.
How did that beef end up with 3 to 6 times the legal limit of radioactive cesium? According to the farmer, the cows were raised on hay from last year, before the reactor catastrophe, but were drinking water from a local well.
The ex-skf blog translates a Yomiuri Shimbun article:
According to the investigation by Fukushima Prefecture, 2924 meat cows have been shipped from the same area since the end of April.
- Fukushima gov’t inspects farm over beef radiation concerns (Mainichi, 2011-07-11)
It has been reported that the cattle on the farm in Minamisoma had been fed straw that was not covered by a roof and therefore could have been exposed to fallout in rain.