Selasa, 27 Maret 2012

Fukushima update....

INES Level 1 Contamination at Fukushima II (Daini), Caused by the Spill of Contaminated Water from Fukushima I (Daiichi), Says NISA

TEPCO transported 140 liters of the water after being treated by the cesium absorption towers (SARRY, Kurion) from Fukushima I Nuclear Power Plant to Fukushima II (Daini) Nuclear Power Plant for nuclide analysis, but somehow the water spilled and contaminated the buildings in Fukushima II.

Duh. Why TEPCO needed to transport a large quantity of contaminated water just for analysis, no one knows. The water contained maximum 700 becquerels/cubic centimeter of radioactive materials, so the 140 liters of this water could contain 700 x 1000 x 140 = 98 million becquerels of radioactive materials.

First, the overview of the incident from Jiji Tsushin (3/27/2012):

Contaminated water from Fukushima I for analysis spilled at Fukushima II Nuclear Power Plant, says TEPCO


TEPCO announced on March 27 that the contaminated water spilled from the container and contaminated desks and corridors at Fukushima II Nuclear Power Plant. The water contained radioactive strontium and other nuclides, and was brought from Fukushima I Nuclear Power Plant to Fukushima II Nuclear Power Plant for analysis. The Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry has instructed TEPCO to report the details, as the company is likely to have been in violation of the regulation that specifies how the contaminated water should be handled.


According to TEPCO and the NISA, contamination was found at 7 locations in the service building for Reactors 3 and 4 at Fukushima II Nuke Plant, on the desks and corridors. Maximum 700 becquerels per cubic centimeter of radioactive materials have been found from the locations of the spill. There is no worker exposed to the contamination.
"140 liters" information comes from the ad hoc NISA press conference on March 27 at 9:15PM (that's unusual these days).

More detailed information from the press conference, by Ryuichi Kino:
東電の発表では、汚染は206Bq/cm2 [sic] という話だったが、保安院の発表では、最高700Bq/cm3と聞いているとのこと。ただ、運んでいた量が全部で140L。なんでこんなに多量の汚染水を運んでいたのかは、今のところ不明。保安院によれば今回の漏洩量は少ないが場合によっては汚染された水のすべてが漏洩した可能性があり、その場合に想定される放射性物質の量などからすると、国際原子力事象評価尺度(INES)の対象になり、暫定でINESレベル1と判断しているとのこと。

TEPCO announced the contamination as 206 Bq/cubic centimeter, but NISA says max 700 Bq/cubic centimeter. Total amount of the water was 140 liters. It's not known why such a large quantity of contaminated water was being transported. According to NISA, the amount of leak this time was small, but depending on the situation the entire amount could have leaked. If that was the case, INES (International Nuclear Event Scale) should be applied to the incident because of the amount of radioactive materials that would have been released; consequently, NISA considers the incident as INES Level 1, on a provisional basis.


Another question. TEPCO touched on this spill very lightly at the 6PM press conference, and said there was only one contamination. But NISA says there were 7 locations that were contaminated. The spill happened at 12:42PM, and TEPCO didn't have the details at the press conference, 5 hours after. Too slow.
Kino also reports this was the second time TEPCO transported a large quantity of contaminated water from Fukushima I to Fukushima II.
(Additional information)
Kino also says that the contaminated water is routinely sampled by the affiliate companies (probably Toshiba, Hitachi, and other top-tier contractors) for testing at their facilities.


73 Sierverts/Hr Radiation Inside Reactor 2 Containment Vessel at #Fukushima I Nuke Plant

Not that surprising, but here's how Yomiuri Shinbun (3/28/2012) puts it:

TEPCO announced on March 27 that they directly measured the radiation levels inside the Containment Vessel at Fukushima I Nuclear Power Plant for the first time since the accident had started, and the maximum level was 73 sieverts/hour.


It is the highest level measured after the accident. If one is exposed to radiation at this level, the radiation sickness including vomiting starts in less than one minute, resulting in death in about 8 minutes. TEPCO says "It is impossible for human workers to work inside the CV. In order to fully understand the condition inside, it will be necessary to develop equipments that withstand high levels of radiation."


The radiation survey was done by inserting the dosimeter through the same pipe that had been used for the endoscope on March 26. 8 locations were measured, at 50 to 100 centimeters off the inner wall of the Containment Vessel. The radiation levels were 31 to 73 sieverts/hour. The levels are more than 100,000 times as high as the levels during a regular maintenance. It is probably due to the melted core that has dropped to the CV and radiation from the radioactive materials that have dispersed inside the CV.
The dosimeter was capable of measuring up to 1,000 sieverts/hour radiation. 19 TEPCO workers and 16 Toshiba workers spent one hour, receiving maximum 1.69 millisievert per person for the work.As you can see from the TEPCO's handout below, all the measurements were above the grating, and the radiation levels 100-centimeter off the wall were higher than those at 50 centimeters.


73Sv/h in container vessel

During the endoscope operation of 3/26/2012, Tepco measured the radiation level of inside of container vessel. Tepco published the data the next day, 3/27/2012.
It was measured at 8 points, 50~100cm away from the wall.
The highest reading was 73Sv/h.(100,000 times higher than the radiation level of the container vessel in periodic checkup) Other readings were 31.1~57.4 Sv/h.
73Sv/h in container vessel3

73Sv/h in container vessel4
In this level of radiation, human starts vomiting within a minute and dies within 8 minutes. It is impossible to have human work inside of container vessel.

Actually, Tepco did not intend to watch the fuel debris in this endoscope operation. Tepco is assuming that the fuel is in pedestal, which is separated from where they checked with endoscope this time with concrete wall. (Like this picture below.)

73Sv/h in container vessel

To see where Tepco assumes the fuel debris is, they have to put the camera under the pressure vessel, surrounded by the concrete of pedestal. About this potential attempt, actual Fukushima worker Happy11311 tweeted like this below.

The highest reading of 73 Sv/h was lower than I thought, but no one can get close to there. Probably it is higher than 1000Sv/h  inside or in front of the entrance of the pedestal. The endoscope used this time can’t resist the radiation of  higher than 1000Sv/h so it would be over scale.

The fuel debris has not been checked yet, but this operation made it clear that it would take considerable amount of time to fill container vessel with water as Tepco is planning, or it would be simply impossible. and they are planning to take out the fuel in 10 years but it would take way more than 10 years. I don’t know how long it takes.


Long and tough road ahead for work to decommission Fukushima nuclear reactors, The Mainichi Daily News, Dec. 8, 2011 (Emphasis Added):
  • It is expected to take more than 30 years to decommission crippled reactors
  • Workers [...] would have to venture into “uncharted territory”
  • Filled with hundreds of metric tons of highly radioactive nuclear fuel
  • Work would have to be done in a “territory where humans have not stepped into before,” said a senior official of TEPCO
  • 1,496 fuel rods [???] from the No. 1 to 3 nuclear reactors
  • 3,108 fuel rods from nuclear fuel pools of the No. 1 to 4 reactors
Filling Containment Vessel with Water
  • According to experts, filling the containment vessels with water completely to shield radiation is the “foremost and biggest hurdle”
  • It is necessary to spot and repair damaged parts in the containment vessels
  • Up to about 5,000 millisieverts per hour of radiation — lethal levels — have been detected in the reactor building of the No. 1 reactor
  • In April, TEPCO said it would bring the nuclear plant under control by filling the reactors with water
  • Subsequent analysis of the accident suggested that the No. 1 and 2 reactors had holes of up to 50 square meters caused by hydrogen explosions and the like [EX-SKF said Mainichi article was mistranslated. The original Japanese says the size of holes as 50 square centimeters, not meters.]
  • In May, TEPCO said it had scrapped its plan to repair the containment vessels and suspended the work to fill them with water
  • Removing Melted Fuel
    • Workers have been fighting an uphill battle to remove crumbled fuel
    • Most of the fuel melted and apparently dropped into the containment vessel from the bottom of the pressure vessel at the No. 1 reactor
    • A single fuel rod contains about 170 kilograms of uranium
    • About 254 tons of uranium in the reactors alone must be recovered
    • Between the upper lid and the bottom of a containment vessel is up to 35 meters
    • Work has to be done to chop off and recover melted and crumbled fuel by using remote controlled cranes
    • Melted fuel is mixed with metal from fuel pellets and reactor parts

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