Between the Poles

Fukushima Daiichi: Three damaged reactors brought below 100 degrees C

TEPCO has reported that the radiation being emitted from Fukushima Daiichi has droped by a half from a month ago.  The latest measurements indicate that radiation emitted from the damaged reactors is 100 million becquerels per hour.  TEPCO says that this equates to about 0.2 millisievert per year of radiation measured at the fringes of the plant.

An important reason for the drop in radiation emissions is that the temperatures of the three damaged active reactors were brought below 100 degrees C late in September dramatically reducing the amount of radioactive steam released into the atmoshere.

According to the Wall Street Journal the emissions from the plant have continued to decline from their peak March 15.

• March 15 - 800 trillion Bq/hr
• March 25-26 - 2.5 trillion Bq/hr
• April 4-6 - 0.29 trillion Bq/hr
• June 20-28 1 billion Bq/hr
• July 26-Aug 12 - 200 million Bq/hr
• Sep 1-17 - 200 million Bq/hr
• Oct 3-13 - 100 million Bq/hr

US nuclear power plant shut down after East Coast earthquake

One of the causes of the massive problems at Fukushima Daichi after the magnitude 9 earthquake earlier this year was loss of offsite power, which resulted in loss of cooling function and to partial meltdown of reactor fuel rods.

Yesterday afternoon, a magnitude 5.9 earthquake occurred in Virginia (which we felt in Ottawa) with its epicentre just 20 miles away from Dominion Virginia Power's North Anna nuclear power plant.  As a result of the earthquake, the power plant lost offsite power from the grid.  As happened at Fukushima Daiichi, emergency diesel backup generators fired up, but unlike Fukushima Daiichi, the plant wasn't hit by a subsequent tsunami.  Still the plant's operators shut down (inserted control rods to stop the spontaneous nuclear reaction) the plant's two reactors as a precautionary measure.  No damage was reported at North Anna, but it is not clear when the company would restart the plant.  The plant declared an emergency, officially an "alert", the second level of emergency classification, according to Nuclear Regulatory Commission (NRC) guidelines.

According to the NRC several nuclear plants declared 'unusual events', the lowest level of emergency classification, when they sensed the seismic activity, but none of the US's other nuclear power plants were seriously affected by the earthquake.

Fukushima Daiichi: Large release of radioactive material into seawater April 1-6

TEPCO has estimated the total release of radioactive material into seawater in the six days following April 1.

• 4,700 Tbq

For comparison the estimated total release of radioactive material at Three Mile Island is about 1/10,000th of TEPCO's estimate.  The total release at Chernobyl was nearly 400 times greater.  However, TEPCO's estimate is only for radioactive material released into seawater during a period of six days.

Three Mile Island (about 1/10,000 of TEPCO's estimate)

• 0.481–0.629 Tbq of I-131

(No detectable amounts of the long-lived radioactive cesium and strontium escaped to the environment at TMI.)

Chernobyl (nearly 400 times greater than TEPCO's estimate)

• 1,760,000 Tbq of I-131
•      85,000 Tbq of Cs-137

Fukushima Daiichi: Japan makes it illegal to enter within 20 km of plant

Fukushima Daiichi Nuclear Power Plant remains in a dangerously unstable state.  TEPCO's roadmap estimates that that it will take several months to stabilize the plant. 

The Chief Cabinet Secretary Yukio Edano said "The plant has not been stable. We have been asking residents not to enter the area as there is a huge risk to their safety,"  The Japanese government has just announced that it is now illegal to enter the evacuation zone around the Fukushima Daiichi nuclear reactor.  The mandatory evacuation zone includes the region within 20 km of the plant plus named locations to the northwest of the plant where high dosage and deposition levels have been reported.

Fukushima Daiichi: Radiation dosage levels 20 km and more from plant

MEXT reports radiation dosage readings every three hours in the region 20 km and greater from the Fukushima Daiichi nuclear power plant.  The latest maximum readings reported Apr 20 occur ar reading posts [32] and [83].

[32] Futaba county Namie town Akougi Teshichiro (About30km northwest)

• 21.3 μSv/h at 2011/4/20 16:25 (JAEA)

[83] Futaba county Namie town Akougi Kunugidaira (About20km northwest)

• 46.8 μSv/h at 2011/4/20 15:45 (JAEA)

Previous readings

April 16

• 25.3 μSv/h at 10:13  April 16 [32]
• 43.8 μSv/h at 11:15  April 16 [83]

March 31

• 38.0 μSv/h at reading post [32]
• 55.6 μSv/h at reading post [83]

Previous readings at [83]

• 87.0 μSv/h 2011/3/27 10:25 (21:25:00 Saturday March 26 ET)

Previous readings at [32]

• 45.0 μSv/h 2011/3/27 11:55 (22:55:00 Saturday March 26 ET)
• 50.0 μSv/h 2011/3/27 11:30 (22:30:00 Saturday March 26 ET)
• 105.0 μSv/h at 2011/3/20 15:03 (02:03 am Sunday March 20 ET)
• 110.0 μSv/h at 2011/3/20 14:03 (01:03 am Sunday March 20 ET)
• 110.0 μSv/h at 2011/3/20 13:03 (00:03 am Sunday March 20 ET)
• 132.0 μSv/h at 2011/3/19 11:20 (10:20 p.m. Friday March 18 ET)
• 136.0 μSv/h at 2011/3/19 10:20 (09:20 p.m. Friday March 18 ET)
• 135.0 μSv/h at 2011/3/19 9:20 (08:20 p.m. Friday March 18 ET)
• 150 μSv/hr Mar 18 13:32 (00:32:00 Friday March 18 ET)
• 140 μSv/hr Mar 18 12:33 (11:32:00 Thursday March 17 ET)
• 140 μSv/hr Mar 18 11:33 (10:32:00 Thursay March 17 ET)

 

Fukushima Daiichi: Radiation dosage levels at plant continue to decline

TEPCO is reporting radiation dosage levels at several locations at the plant as well as at the plant perimeter.

 

 

 

Previous readings reported by JAIF.

15:00, Apr. 20th (02:00 am Friday April 20 ET)

• 480μSv/h south side of the office building
• 60μSv/h Main gate 
• 24μSv/h West gate 

15:00, Apr. 15th (02:00 am Friday April 15 ET)

• 530μSv/h south side of the office building
• 70μSv/h Main gatt
• 28μSv/h West gate

15:00, Apr. 7th (02:00 am Thursday April 7 ET).

• 0.67 mSv/h (670 μSv/h) south side of the office building
• 108 μSv/h Main gate
• 43 μSv/h West gate

09:00, Apr. 3rd (20:00 Saturday April 2 ET)

• 0.83 mSv/h (830 μSv/h) south side of the office building
• 127 μSv/h Main gate
• 59 μSv/h West gate

21:00, Mar. 31st (08:00 am Thursday March 31 ET)

• 0.94 mSv/h (940 μSv/h) at the south side of the office builiding
• 148 μSv/h at the Main gate
• 70 μSv/h at the West gate

21:00, Mar. 30th (8:00 am Wednesday March 30 ET)

• 1.00 mSv/h (1000 μSv/h) at the south side of the office building
• 156 μSv/h at the main gate
• 72 μSv/h at the west gate

15:00, Mar. 30th (02:00 am Wednesday March 30 ET)

• 1.05mSv/h (1050 μSv/h) at the south side of the office building
• 163 μSv/h at the main gate
• 75 μSv/h at the west gate

09:00, Mar. 30th  (20:00:00 Tuesday March 29 ET)

• 1.05 mSv/h (1050 μSv/h) at the south side of the office building
• 169 μSv/h at the Main gate
• 78 μSv/h at the West gate

Earlier readings at the West Gate

• 120.0 μSv/h at 21:30, Mar. 28 (08:30 am Monday March 28 ET)
• 122.8 μSv/h at 15:30, Mar. 28 (02:30 am Monday March 28 ET)
• 132.5 μSv/h at the West gate at 16:00, Mar. 27 (03:00 am Sunday March 27 ET)

Fukushima Daiichi: Robots measure high dosage levels in Unit 1 and 3 reactor buildings

Sunday and Monday robots measured radiation dosage levels in Unit 1 and 3 reactor buildings.

Unit 1

TEPCO said the robots surveyed the first floor of Unit 1 for about 50 minutes.

The maximum radiation reading reported was 49 mSv/hr.

Unit 3

TEPCO said a robot attempted to survey inside Unit 3 for about 2 hours, but apparently debris restricted its movements.

The maximum radiation reading reported was 57 mSv/hr.

The maximum permissible dose for Japanese nuclear workers was 100 mSv per year before the accident at Fukushima Daiichi. Shortly after the accident, the Japanese government increased the annual limit to 250 mSv for emergency situations. The World Health Organization considers 500 mSv/year acceptable for emergency work.

Fukushima Daiichi: Radiation dosage levels 20 km and more from plant decreasing

MEXT is recording radiation dosage readings every three hours in the region 20 km and greater from the Fukushima Daiichi nuclear power plant.  The latest maximum readings reported April 16 occur ar reading posts [32] and [83].

[32] Futaba county Namie town Akougi Teshichiro (About30km northwest)

• 25.3 μSv/h at 10:13  April 16

[83] Futaba county Namie town Akougi Kunugidaira (About20km northwest)

• 43.8 μSv/h at 11:15  April 16

Previous readings March 31

• 38.0 μSv/h at reading post [32]
• 55.6 μSv/h at reading post [83]

Previous readings at [83]

• 87.0 μSv/h 2011/3/27 10:25 (21:25:00 Saturday March 26 ET)

Previous readings at [32]

• 45.0 μSv/h 2011/3/27 11:55 (22:55:00 Saturday March 26 ET)
• 50.0 μSv/h 2011/3/27 11:30 (22:30:00 Saturday March 26 ET)
• 105.0 μSv/h at 2011/3/20 15:03 (02:03 am Sunday March 20 ET)
• 110.0 μSv/h at 2011/3/20 14:03 (01:03 am Sunday March 20 ET)
• 110.0 μSv/h at 2011/3/20 13:03 (00:03 am Sunday March 20 ET)
• 132.0 μSv/h at 2011/3/19 11:20 (10:20 p.m. Friday March 18 ET)
• 136.0 μSv/h at 2011/3/19 10:20 (09:20 p.m. Friday March 18 ET)
• 135.0 μSv/h at 2011/3/19 9:20 (08:20 p.m. Friday March 18 ET)
• 150 μSv/hr Mar 18 13:32 (00:32:00 Friday March 18 ET)
• 140 μSv/hr Mar 18 12:33 (11:32:00 Thursday March 17 ET)
• 140 μSv/hr Mar 18 11:33 (10:32:00 Thursay March 17 ET)

Fukushima Daiichi: TEPCO announces 6 to 9 month plan to get plant under control

TEPCO has announced a two phase plan to stabilize the Fukushima Daiichi Nuclear Power Plant.

Phase One - 3 months

• build new cooling systems outside Units 1 and 3 to cool down fuel
• patch the damaged section of Unit 2 reactor to contain radioactivity leakage

Phase Two - 3 to 6 months

TEPCO plans to

• lower the temperature of the nuclear fuel in all reactors to below 100^o Celsius
• cover the reactor buildings with giant covers with filters to prevent the release of radioactive substances into the air.
• set up equipment to purify contaminated water in tanks and other facilities.
• increase the number of monitoring points within the government-set evacuation areas
• neutralize the radioactive substances in soil and on buildings in the evacuation areas

Fukushima Daiichi: Iodine-131 concentrations in seawater 30 km off Fukushima coast exceeding legal limit

MEXT is reporting radioactive element concentrations in seawater samples taken 30 km off the coast of Fukushima Prefecture.  Below are the maximum readings for each day when samples have been taken since the end of March.

                                  I-131  Cs-137

[5] 2011/4/13 12:25pm  64.1    54.3  Bq/l

[4] 2011/4/11 10:55am  88.5    71.0  Bq/l

[3] 2011/4/9  11:00am   77.4    44.2  Bq/l

[6] 2011/4/7  12:00pm   56.3    19.8  Bq/l

[5] 2011/4/5  12:42pm   66.1    38.5  Bq/l

[6] 2011/4/3  11:04am   18.3    10.70 Bq/l

[5] 2011/4/1  11:29am   12.0    15.7  Bq/l

[6] 2011/3/30 10:54am    8.7      8.46 Bq/l

[5] 2011/3/28 11:06am     6.96   19.6  Bq/l

The regulatory limit for I-131 is 0.04 Bq/cm³ (40 Bq/l).  For Cs-137 the limit is 0.09 Bq/cm³ (90 Bq/l).