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This could have been homecoming week in this pretty seaside town. Seven months after most residents fled as explosions rocked the nearby Fukushima Daiichi nuclear plant, the Japanese government has declared it safe to return to Hirono.But a week after the country’s Nuclear Disaster Minister lifted the government’s evacuation recommendation for Hirono and three other towns, no one has returned. The only people in Hirono are the same hard-core few who ignored the evacuation advisory all along, plus the teams of rescue workers who use the town as a base while they race to and from the battle to repair the four damaged reactors to the north.

For the rest of the town’s pre-disaster population of 5,500 – including the outspoken mayor – an assurance from Tokyo is nowhere near enough to persuade them to return. Most prefer to remain, for now, in cramped temporary accommodations further from Fukushima Daiichi.“I don’t plan to come back, ever,” said a middle-aged woman who briefly visited Hirono this week to retrieve belongings from the two-storey home that she and her family fled on March 12, the day after the tsunami that set in motion the worst nuclear disaster since Chernobyl. She paused to take in her abandoned home’s view of the ocean and its now-unkempt garden. “I’ll never feel safe here. I’ll never feel secure.”

Hirono and the three other towns that the government is encouraging residents to return to are in a third zone, between 20 and 30 kilometres from the plant. Pregnant women and hospitalized patients were advised to evacuate the towns in mid-April, the rest of the 58,500 who live in the area were told at the same time to be ready to flee “on a moment’s notice.” All left immediately, with the exception of 300 steadfast residents, most of them elderly enough to claim they aren’t worried about the long-term effects of radiation.

Contaminated soil a concern at Los Alamos lab, Reuters, July 11, 2011: [...] crews at the Los Alamos National Laboratory have begun removing contaminated soil from nearby canyons out of a concern that flash flooding could wash toxins into the Rio Grande [that supplies drinking water for Santa Fe and many other communities] officials said on Monday. [...] The soil in the canyons above Los Alamos National Laboratory, the linchpin of American’s nuclear weapons industry, contains materials with trace amounts of radiation [...] Over the weekend, about 1,200 cubic yards of contaminated soil was removed primarily from two canyons — Los Alamos and Pajarito — that run through lab property, [ Fred deSousa, spokesman for the lab's environmental control division] said.

An Assessment of Los Alamos National Laboratory Waste Disposal Inventory, Radioactive Waste Management Associates, November 2009:

Since the beginning of its operations LANL has disposed of millions of gallons of radioactive and hazardous waste throughout the laboratory grounds and in the canyons that surround the laboratory. [...]

The U.S. Nuclear Regulatory Commission released recommendations this week based on lessons from Japan's Fukushima Daiichi nuclear plant disaster, declaring that events like those at Fukushima are unlikely to occur in the United States because of stringent safety measures and regulations.

The 90-day study suggested developing equipment and procedures for U.S. nuclear reactors to keep the core and spent fuel pool cool and requiring that facilities' emergency plans address prolonged station blackouts and events involving multiple reactors.

A roadmap toward decommissioning of the damaged Fukushima Daiichi nuclear power plant indicates that the removal of melted nuclear fuel rods at the plant may begin in 10 years. NHK has obtained the mid- and long-term roadmap which was presented when officials from the operator of the Fukushima plant, government officials in charge of nuclear safety, and manufacturers of nuclear reactors met last week. The draft roadmap drawn up by the government's Nuclear Safety Commission and Tokyo Electric Power Company says they tentatively set a target date to begin removing fuel rods that melted and fell to the bottom of the reactor. The work is considered to be the most important phase in the decommissioning process. The roadmap indicates that removal will start in 2021 if technology essential for the work has been developed before that. The timeline is believed to have been set based on measures taken following the 1979 Three Mile Island accident in the United States. But unlike the US case, as reactor containment vessels were damaged at the Fukushima complex, they need to be fixed and filled with water. The roadmap shows that reactor buildings could be finally demolished and cleared away after the removal of melted fuel rods is completed, and that it will possibly take dozens of years.

The TerraPower "wave reactor" concept is backed by Microsoft's Bill Gates, is endorsed by Republican presidential hopeful Jon Huntsman Jr. and has gotten a receptive ear from President Obama's Energy Department. But it's headed overseas for its next crucial step, if ongoing negotiations with a foreign sponsor are successfully completed, says Roger Reynolds, TerraPower's technical adviser.

"We've had conversations with the Chinese, the Russians, the Indians, the French," Reynolds said in an interview. "We have an aggressive schedule where we think it is important to get something built and accumulate data so that we can eventually build them in the U.S. Breaking ground in 2015, with a startup in 2020, is more aggressive than our current [U.S.] regulatory structure can support."

In addition to its unique fuel cycle, the TerraPower design employs a high-temperature, liquid metal core cooling technology suited to a breeder reactor with "fast" neutron activity, rather than today's predominant reactors whose water cooling systems slow neutrons.

Tokyo Electric Power Co. and the government on Oct. 17 released a newly revised a road map to bring the stricken Fukushima No. 1 nuclear power plant under control. It shows that a “cold shutdown” of the Nos. 1, 2 and 3 reactors at the plant will be achieved by the end of the year. The reactor cores suffered meltdowns after the March 11 earthquake and tsunami inflicted severe damage, but the temperature in the lower part of the pressure vessels has now fallen below 100 C. As of Oct. 15, it was between 73 C. and 83 C. The amount of radioactive substances released from the reactors has been halved from the level in September when the road map was earlier revised. It is estimated that the three reactors are now releasing radioactive substances at the rate of about 100 million becquerels per hour maximum, about one-eighth of a millionth the level immediately after the nuclear crisis started.

Tepco and the government said that with this rate, the annual exposure to radiation in the Fukushima No. 1 compound will be around 0.2 millisieverts maximum, lower than the goal of one millisievert. They also said that the level of contaminated water in the reactor building basements has stabilized. In view of those factors, Tepco and the government said in their newly revised road map that the “cold shutdown” will be achieved by the end of this year. But it must be emphasized that the state of “cold shutdown” that Tepco and the government speak of does not meet the true definition of a cold shutdown — when the temperature inside the pressure vessel is below 100 C and the reactors no longer release radioactive substances. Therefore, achieving this state would not mean that the nuclear crisis has been brought under control.

About 19 percent of airborne fallout from the Fukushima nuclear disaster was deposited in Japan, and only about 2 percent made it to other land areas in Asia and North America, according to a study published this week by the European Geosciences Union. The bulk was absorbed by the Pacific Ocean.

Opponents of nuclear energy have seized on the European study because it describes the total release at Fukushima as “massive.” It finds that twice as much cesium 137 was released at Fukushima than originally reported. And it says “high concentrations” reached North America and Europe. It examines two radionuclides in particular–xenon 133 and cesium 137–and measures the total release in terabecquerels.

Altogether, we estimate that 6.4 TBq of 137Cs, or 19 percent of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean,” the authors write. “Only 0.7 TBq, or 2 percent of the total fallout were deposited on land areas other than Japan.” Scientists generally regard ocean absorption of fallout preferable to land deposits, because water absorbs radiation and the volume of the ocean dilutes it. On land, radioactive isotopes can be consumed by livestock and concentrated in milk and other food sources. The study also notes that airborne emissions of cesium 137 continued until March 19, when Japanese authorities began spraying water on the spent fuel pool of reactor #4. “This indicates that emissions were not only coming from the damaged reactor cores, but also from the spent-fuel pool of unit 4 and confirms that the spraying was an effective countermeasure.”

“Fortunately, due to the maintenance outage and the survival of one diesel generator, it seems that unit 5 reactor cores as well as spent fuel ponds have not suffered major fuel damage,” says the study. Though, Reactor No. 5 is mentioned again several pages later: “Total a posteriori [experienced levels] 133Xe emissions are 16.7 EBq, one third more than the a priori value [predicted levels] of 12.6 EBq (which is equal to the estimated inventory) and 2.5 times the estimated Chernobyl source term of 6.5 EBq.

If there was only 12.6 EBq of xenon-133 inventory that could be emitted from reactors 1-3 and spent fuel pool No. 4 — yet 16.7 EBq was experienced — where did the extra xenon come from, according to the study? “There is the possibility of additional releases from unit 5.” Another possibility is that recriticality has occurred in one of the reactor units. The study says the a priori emissions could have been overestimated, but discounts the notion that the initial 12.6 EBq figure so poorly underestimated the amount of xenon in Reactors 1-3 and SFP 4, “It is unlikely that the 133Xe inventories of the reactor units 1–3 were one third higher than estimated.”

ABSTRACT: ACPD – Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition SOURCE: Discussion Paper See also: Report: Fukushima Reactors No. 5, 6 now in crisis — Cesium outside release points up 1,000% in recent days — Local says Hitachi engineers coming to help (VIDEO)

A plan to connect six reactors at the crippled Fukushima No. 1 nuclear power plant, which could have reduced the damage from the Great East Japan Earthquake and tsunami, never left the drawing board, according to sources. Tokyo Electric Power Co. sources said while consideration had been given in 2006 to connecting all sources of electricity at all six reactors, no decision was made because of technical problems. However, nuclear engineering experts said the work could have been implemented and added that overconfidence about the low possibility of all reactors losing all their electrical sources was likely behind the failure to proceed with the reconstruction work.

"TEPCO officials likely concluded that there was no need to spend time and money because of an overconfidence that a loss of electricity sources would never occur," said Tadahiro Katsuta, associate professor of nuclear engineering at Meiji University. "If the work had been carried out, there was the possibility that damage could have been reduced." After the March 11 tsunami hit the Fukushima No. 1 plant, the No. 1 to No. 4 reactors lost their electrical sources. The inability to properly cool the reactors led to a core meltdown and hydrogen explosions that severely damaged the reactors and spewed large amounts of radioactive materials into the atmosphere. The No. 5 and No. 6 reactors were connected in terms of electricity sources and the emergency diesel generator at the No. 6 reactor, which was the only one that continued to work, enabled cooling to continue at those two reactors.

As an emergency measure, TEPCO officials laid electrical cables between all six reactors by April 25. Because TEPCO proceeded with such work after the quake and tsunami, experts said if reconstruction work had been conducted in 2006, there was the possibility that a major accident could have even been prevented. According to former TEPCO executives, a plan was considered in 2006 to strengthen the electricity facilities at the Fukushima No. 1 plant to avoid a critical accident that might occur should all electrical sources be lost due to a natural disaster. The No. 1 to No. 4 reactors on the south side of the plant were connected by electrical cables and those four reactors could share electricity if the need arose.

Radioactive materials from the damaged Fukushima No. 1 nuclear plant reached the Kanto region mainly via two routes, but they largely skirted the heavily populated areas of Tokyo and Kanagawa Prefecture, an expert said. Relatively high levels of radioactive cesium were detected in soil in northern Gunma and Tochigi prefectures and southern Ibaraki Prefecture after the Fukushima No. 1 nuclear power plant was damaged by the March 11 Great East Japan Earthquake and tsunami. But contamination was limited in Tokyo and Kanagawa Prefecture, where 22 million people live. Hiromi Yamazawa, a professor of environmental radiology at Nagoya University, said the first radioactive plume moved through Ibaraki Prefecture and turned northward to Gunma Prefecture between late March 14 and the afternoon of March 15.

Large amounts of radioactive materials were released during that period partly because the core of the No. 2 reactor at the Fukushima No. 1 plant was exposed. "The soil was likely contaminated after the plume fell to the ground with rain or snow," Yamazawa said, adding that western Saitama Prefecture and western Tokyo may have been also contaminated. Rain fell in Fukushima, Tochigi and Gunma prefectures from the night of March 15 to the early morning of March 16, according to the Meteorological Agency. The second plume moved off Ibaraki Prefecture and passed through Chiba Prefecture between the night of March 21 and the early morning of March 22, when rain fell in a wide area of the Kanto region, according to Yamazawa's estimates.

He said the plume may have created radiation hot spots in coastal and southern areas of Ibaraki Prefecture as well as around Kashiwa, Chiba Prefecture. Yamazawa said the plume continued to move southward, without approaching Tokyo or Kanagawa Prefecture, probably because winds flowed toward a low-pressure system south of the Boso Peninsula. "It rained slightly because the low-pressure system was not strong," said Takehiko Mikami, a professor of climatology at Teikyo University. "Contamination in central Tokyo might have been more serious if (the plume) had approached more inland areas." According to calculations by The Asahi Shimbun, about 13,000 square kilometers, or about 3 percent of Japan's land area, including about 8,000 square kilometers in Fukushima Prefecture, have annual exposure levels of 1 millisievert or more.

A a government panel on Friday said that decommissioning the crippled Fukushima Daiichi nuclear power plant is likely to take 30 years or more, local media reported. “We set a goal to start taking out the (core) debris within a 10-year period,” the panel under the Japan Atomic Energy Commission said in a draft, according to Kyodo News. “It is estimated that it would take 30 years or more to finish decommissioning.”

TOKYO (Kyodo) -- Removing the melted nuclear fuel from the crippled reactors at the Fukushima Daiichi power plant should start within 10 years after the plant's cold shutdown, and decommissioning is likely to take 30 years or more, a government panel projected in a draft report released Friday.

"We set a goal to start taking out the (core) debris within a 10-year period...and it is estimated that it would take 30 years or more (after the cold shutdown) to finish decommissioning," the draft said.

Download: U.S. Nuclear Power after Fukushima | U.S. Nuclear Power after Fukushima -- Summary

The report outlines and explains 23 specific recommendations, listed below.   = Key recommendation that the NRC should make a top priority. Preventing and Mitigating the Effects of Severe Accidents Extend the scope of regulations to include the prevention and mitigation of severe accidents. Require reactor owners to develop and test emergency procedures for situations when no AC or DC power is available for an extended period. Modify emergency planning requirements to ensure that everyone at significant risk from a severe accident--not just the people within the arbitrary 10-mile planning zone--is protected.

Improving the Safety and Security of Spent Fuel The NRC should require plant owners to move spent fuel at reactor sites from storage pools to dry casks when it has cooled enough to do so. The NRC should require reactor owners to improve the security of existing dry cask storage facilities. The NRC should require plant owners to significantly improve emergency procedures and operator training for spent fuel pool accidents Making Existing Reactors Safer The NRC should enforce its fire protection regulations and compel the owners of more than three dozen reactors to comply with regulations they currently violate.

TEPCO has announced that as of today, the final additions to the enclosure structure at No. 1 reactor building have been made (air circulation and filtration equipment) and that the inspection of the structure and systems by NISA is completed satisfactorily. The structure itself has been completed for a while, but this might be considered as the official commissioning of the entire structure and ventilation system.-TEPCO has also announced that it will drastically increase the amount of water being injected to No. 1 reactor in order to cut down on evaporation inside the structure. It appears that the high humidity environment is hampering the ability to work inside, so TEPCO will increase the feed rate through the feed line (normal feedwater injection line) upward from 4 cubic meters per hour to 7.5 cubic meters per hour over four days. When the conditions of the plant are ascertained at that point TEPCO will further increase water flow. This will also reduce drastically any gaseous emissions to the enclosure from the damaged reactor.

TEPCO has discovered a nearly or else completely sheared axle shaft casing on the overhead crane at the common spent fuel building at Fukushima Daiichi. The cause is yet unknown, and no hazard is posed at this time. -TEPCO is almost ready to place the gas handling system (improvised arrangement) at No. 2 reactor plant (to handle gases in the primary containment) into operation. This system will filter out radioactive airborne contaminants. Similar systems will be employed eventually at all three reactors.

Finally, airborne releases from Fukushima Daiichi continue to decline .. contrary to many reports on anti-nuclear sites .. as shown by these two panels from a report issued by the Japanese Prime Minister's office.

A. Stohl1, P. Seibert2, G. Wotawa3, D. Arnold2,4, J. F. Burkhart1, S. Eckhardt1, C. Tapia5, A. Vargas4, and T. J. Yasunari61NILU – Norwegian Institute for Air Research, Kjeller, Norway2Institute of Meteorology, University of Natural Resources and Life Sciences, Vienna, Austria3Central Institute for Meteorology and Geodynamics, Vienna, Austria4Institute of Energy Technologies (INTE), Technical University of Catalonia (UPC), Barcelona, Spain5Department of Physics and Nucelar Engineering (FEN),Technical University of Catalonia (UPC), Barcelona, Spain6Universities Space Research Association, Goddard Earth Sciences and Technology and Research, Columbia, MD 21044, USAAbstract. On 11 March 2011, an earthquake occurred about 130 km off the Pacific coast of Japan's main island Honshu, followed by a large tsunami. The resulting loss of electric power at the Fukushima Dai-ichi nuclear power plant (FD-NPP) developed into a disaster causing massive release of radioactivity into the atmosphere. In this study, we determine the emissions of two isotopes, the noble gas xenon-133 (133Xe) and the aerosol-bound caesium-137 (137Cs), which have very different release characteristics as well as behavior in the atmosphere. To determine radionuclide emissions as a function of height and time until 20 April, we made a first guess of release rates based on fuel inventories and documented accident events at the site.

This first guess was subsequently improved by inverse modeling, which combined the first guess with the results of an atmospheric transport model, FLEXPART, and measurement data from several dozen stations in Japan, North America and other regions. We used both atmospheric activity concentration measurements as well as, for 137Cs, measurements of bulk deposition. Regarding 133Xe, we find a total release of 16.7 (uncertainty range 13.4–20.0) EBq, which is the largest radioactive noble gas release in history not associated with nuclear bomb testing. There is strong evidence that the first strong 133Xe release started very early, possibly immediately after the earthquake and the emergency shutdown on 11 March at 06:00 UTC. The entire noble gas inventory of reactor units 1–3 was set free into the atmosphere between 11 and 15 March 2011. For 137Cs, the inversion results give a total emission of 35.8 (23.3–50.1) PBq, or about 42% of the estimated Chernobyl emission. Our results indicate that 137Cs emissions peaked on 14–15 March but were generally high from 12 until 19 March, when they suddenly dropped by orders of magnitude exactly when spraying of water on the spent-fuel pool of unit 4 started. This indicates that emissions were not only coming from the damaged reactor cores, but also from the spent-fuel pool of unit 4 and confirms that the spraying was an effective countermeasure. We also explore the main dispersion and deposition patterns of the radioactive cloud, both regionally for Japan as well as for the entire Northern Hemisphere. While at first sight it seemed fortunate that westerly winds prevailed most of the time during the accident, a different picture emerges from our detailed analysis

Exactly during and following the period of the strongest 137Cs emissions on 14 and 15 March as well as after another period with strong emissions on 19 March, the radioactive plume was advected over Eastern Honshu Island, where precipitation deposited a large fraction of 137Cs on land surfaces. The plume was also dispersed quickly over the entire Northern Hemisphere, first reaching North America on 15 March and Europe on 22 March. In general, simulated and observed concentrations of 133Xe and 137Cs both at Japanese as well as at remote sites were in good quantitative agreement with each other. Altogether, we estimate that 6.4 TBq of 137Cs, or 19% of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean. Only 0.7 TBq, or 2% of the total fallout were deposited on land areas other than Japan.Discussion Paper (PDF, 6457 KB)   Supplement (13 KB)   Interactive Discussion (Open, 0 Comments)   Manuscript under review for ACP   

Earthquakes are routinely measured by magnitude, or energy released. But the Nuclear Regulatory Commission (NRC)requires the nation's 104 nuclear reactors to withstand a predicted level of ground motion, or acceleration — something called g-force. What does that mean, magnitude-wise?

"I don't have what that translates into … unfortunately," NRC spokesman David McIntyre says. The agency released a statement Thursday to clarify its "earthquake measurements and design criteria," but it does not say what ground motion each reactor can handle. This muddiness heightens the concerns of industry critics, who have urged stricter safety rules after reactors at Japan's Fukushima Dai-ichi nuclear plant nearly melted down due to a magnitude-9.0 earthquake and tsunami on March 11.

A task force mandated by President Obama recommended in July that each U.S. plant be re-examined, given ongoing NRC research that shows the seismic risks for Eastern and Central U.S. nuclear power plants have increased. "The Virginia earthquake is now our local 911 call to stop delaying the implementation of stricter safety standards," Rep. Edward Markey, D-Mass., wrote in a letter this week to the NRC.