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The latest USGS earthquake risk maps for the first time show the probability of earthquakes next year in the central and eastern U.S. The new USGS hazard model estimates where, how often and how strongly earthquakes may could occur in the central and eastern United States during calendar year 2016. Also for the first time they include human-induced in addition to natural earthquake risk. Induced earthquakes are linked to human activities the most important of which is wastewater disposal from oil and gas production operations (wastewater from fracking).
According to USGS the central U.S. has experienced a dramatic increase in tremors over the past six years.
Average number of earthquakes of magnitude 3 or greater per year in central U.S. 1973-2008 24 2009-2015 318 2015 1010 2016 (to Mar 15) 226
The largest recent earthquake in the region, a magnitude 5.6 tremor, occured near Prague, Oklahoma near several active injection wells.
By way of history the biggest earthquake in the U.S. east of the Rockies was the 1811/1812 New Madrid earthquakes of estimated magnitude 7.6 -8.0. This occurred near the Mississippi just south of the tip of Illinois where Missouri, Arkansas, Tennessee, and Kentucky come together. Significant risk of major seismic activity in this area continues.
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.
On March 11 both the Fukushima Daini and Daiichi Nuclear Power Plants were hit by a 15 meter tsunami which disabled backup power and reactor cooling systems. By March 12 off-site power was restored to the Daini plant, and by March 15 all four reactors had been brought safely to a cold shut down. At Daiichi off-site power to cooling systems wasn't restored until April 4, with the result that Units 1-3 reactors and Unit 1-6 spent fuel pools could not be adequately cooled for weeks. (Image WNN)
On April 11 there was a magnitude 7 earthquake that resulted in a failure of off-site power at Daiichi. It appears that there are no operational backup diesel power generators at Daiichi, and the power outage resulted in an interruption of reactor and spent fuel cooling for 50 minutes.
TEPCO has just reported that it is planning multiple backup power sources to ensure that cooling at the plant will not be interrupted. On Thursday emergency diesel generators and pumps for Units 1 to 3 were relocated to positions 23 meters above sea level. In addition provision has been made for mobile backup power, on trucks and fire engines. Work has already begun to rewire the transmission power lines to the plant. In addition TEPCO is considering setting up a second system for pumping water into the reactors.
Tuesday the Prime Minister of Japan, Naoto Kan, said that he has instructed TEPCO to develop a roadmap to stabilize the Fukushima Daiichi power plant. Wednesday Masataka Shimizu, president of TEPCO, said that the firm is in the final stages of developing a roadmap, and that TEPCO hopes to make its plans public soon. Shimuzu said that TEPCO's main obligation is to get the plant under control. He also said that the reactors in Units 1 through 4 must be scrapped, implying that Units 5 and 6 are salvageable.
Wednesday the area experienced a magnitide 6.3 earthquake. Although workers were temporarily evacuated, off-site power to the plant was not affected and the plant suffered no damage.
Monday 5:16 PM, JST (04:16 a.m. Monday April 11 ET) The Japan Meteorological Agency reported an earthquake of magnitude 7.0 with an epicenter in Fukushima Prefecture at a depth of 10 kilometers. The agency issued tsunami warnings for the coastal areas of Ibaraki Prefecture. The Meteorological Agency lifted the tsunami warnings fifty minutes later.
TEPCO ordered outside workers at Fukushima Daiichi to evacuate temporarily, but TEPCO said that "radiation figures at monitoring posts around the plant remain unchanged."
TEPCO said water injection into the reactors was suspended for 50 minutes after off-site power was shut down by the earthquake. TEPCO said that off-site power was restored for Units1, 2 and 3 and water injection resumed for these reactors after a suspension of about 50 minutes.
A short video taken about one km from the plant by a worker has been released by TEPCO. It shows what is now said to be at least 14 to 15 m high tsunami hitting the plant about an hour after the magnitude 9 earthquake March 11.
I blogged earlier about what Tohoku Electric and other utilities operating nuclear power plants are doing to prepare for earthquake and tsunami emergencies such as were experienced at Fukushima Daini and Daiichi.
TEPCO has released details of large tide walls that would protect the Kashiwazaki Kariwa Nuclear Power Station and its seven reactors from tsunamis. Kashiwazaki Kariwa is the largest nuclear power plant in the world. It was was off line for two to three years after the 2007 Niigata-Chuetsu earthquake caused damage to the plant, but not to the reactors.
Based on the experience at Fukushima, TEPCO says it has installed facilities on the upland part of the site to provide backup power and water injection to reactors and spent fuel pools to ensure cooling function in the event of a tsunami flooding the reactor buildings. TEPCO is also proposing to install tide barriers with watertight doors at Kashiwazaki Kariwa units 1 to 4. The intention is to prevent flood waters from entering the nuclear reactor buildings where power supply facilities and emergency diesel electric power generators are installed. Reportedly at Fukushima Daiichi backup generators were rendered inoperable by the 14 m tsunami and fuel tanks were washed away.
WNN has reported the casualties at the Fukushima nuclear plants or that can be ascribed to the events at Fukushima Daiichi and Daini.
Three TEPCO workers have died at the plants, one at Daini and two at Daiichi. Two workers who were missing since the earthquake and tsunami March 11 were found dead in the -1 level (basement) of the turbine building of Unit 4 at Daiichi. According to TEPCO they had been "working to protect the safety of the Fukushima power station after the earthquake and tsunami." One worker died at Daini after being trapped with serious injuries in the crane operating console of one of the units during the earthquake. According to WNN these are the only deaths at Japanese nuclear power plants resulting from the earthquake, tsunami and nuclear emergency.
Since the earthquake 370 workers have been working at Daiichi to stabilize the damaged reactor units. Of these 21 have experienced radiation doses of over 100 millisieverts (mSv). According to WNN nuclear workers are permitted to receive a maximum aggregate dose of 20 mSv per year. If that limit is exceeded in any year, the worker is relieved of nuclear duties for the remainder of the year. In an emergency safety regulators may raise the aggregate maximum exposure to 100 mSv. Above 100 mSv it is possible to begin to relate radiation exposure statistically to health effects, specifically cancer. March 16 Japanese authorities authorized exposures of up to 250 millisieverts because of the seriousness of the situation at Daiichi. WNN says that at this point no one has been exposed to an aggregate annual dosage of 250 mSv.
To date "no effects on health or significant contamination cases" have been identified among the general public. The effects of prolonged exposure to elevated low level radiation on health is a controversial topic, but symptoms are not apparent immediately. We all experence exposure to background radiation which according to the US Center for Disease Control is typically about 3 mSv per year.
A magnitude 9 earthquake near Sendai occurred at 14:46 JST (05:46 UTC) on Friday, March 11. The subsequent tsunami hit Fukushima Prefecture about an hour later. There has been very little information about what happened at Daini and Daiichi in the first hours after the earthquake and tsunami that hit the two plants.
I first blogged about the earthquake and nuclear power plants in Japan 16:58 ET March 11 (06:58 am Saturday March 12 JST) or about 16 hours after the earthquake. At that point it had been reported that after the earthquake stopped off-ste power at Daiichi, a backup generator also failed and the cooling system was unable to supply water to cool the Unit 1 reactor, although at least one backup cooling system was being used, and that the reactor core remained hot even after the shutdown. TEPCO was reported to be bringing in mobile generators to restore the power supply. Pressure inside the containment of Unit 1 was continuing to increase, so at this point TEPCO had lost the ability to control pressure in the Unit 1 reactor pressure vessel. Pressure inside the reactor had risen to 1.5 times the level considered normal and the government announced that vapour would be vented from the unit, to lower the pressure in an effort to protect it from "a possible meltdown."
March 12 TEPCO reported that the pressure suppresion function was lost at Daiini and it was preparing to vent vapour from the reactors, but that Units 1,2, and 4 retained off-site power.
But outside of that there has been very little information about what happened at Daini and Daiichi in the first hours after the magnitude 9 earthquake and the tsunami that hit the two plants. March 13 I blogged about what WNN inferred had happened. According to NHK, "the plant's operator, Tokyo Electric Power Company, has so far only disclosed data from the day after the quake."
Friday, April 08, NHK has obtained "unreleased data" that shows that 7 hours after the earthquake and tsunami the water level inside the Unit 1 reactor dropped to 45 cm above the top of the fuel assembly, or about one-tenth the normal level, and 11 hours after that the fuel rods become exposed. According to Professor Naoto Sekimura of the University of Tokyo, the loss of cooling functions at the Unit.1 reactor followed by the exposure of the fuel rods may have led to the first hydrogen explosion March 12.
Units 2 and 3
At Units 2 and 3 emergency generators kept the water levels in the reactors 4 meters above the top of the fuel assembly. It was much longer, between a day and a half to 3 days before fuel rods in these reactors were exposed.
NISA has reported that the magnitude 7.1 earthquake that hit northeastern Japan Thursday, resulted in losing power on 2 of the 3 off-site power lines to the Onagawa Nuclear Power Plant. The plant is using the remaining off-site line to maintain cooling function at its nuclear reactors. It said that the cooling systems of three spent fuel pools also stopped, but have since been restored.
After the March 11 earthquake all the reactiors at Onagawa were shut down (control rods were inserted to stop the uranium chain reaction). Also a fire was reported at the Onagawa plant and an Article 10 emergency was declared at the plant for a brief period when elevated radiation levels were detected.
At the Higashidori nuclear power plant in Aomori Prefecture, the earthquake shut down all off-site power lines, and the plant has had to switch to emergency diesel power generators.
A nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture has also lost all outside power and is operating on emergency diesel generators.
No new deevlopments at the the damaged nuclear power plant at Fukushima Daiichi as a result of the earthquake have been reported. The US NRC has suggested that severe earth tremors like this could further damage reactor pressure vessels.