Fukushima fallout compared to Chernobyls

NISA has decided to raise the crisis level of the Fukushima Daiichi Power Plant accident from level 5 to 7. A gov panel has estimated that the release of 10,000 terabecquerels of radioactive materials per hour continued for several hours.  Even though the gov. commission says the release has since come down to under 1 terabecquerel per hour and it is still examining the total amount of radioactive materials released, NISA says the reason for its decision is that the damaged facilities have been releasing a massive amount of radioactive substances, which are posing a great threat to human health and to the environment over a wide area.  According to an evaluation by the INES, level 7 accidents correspond with a release into the external environment radioactive materials equal to more than tens of thousands terabecquerels of radioactive iodine 131. One terabecquerel equals 1 trillion becquerels.

How bad is the Fukushima Fallout?

The Yomiuri Shimbun

How much radioactive material has so far been released into the atmosphere due to the Fukushima accident? Let’s compare the radioactive contamination caused by the current crisis to past nuclear accidents. (see comparison maps above)

Fallout of cesium-137 has been monitored for every 24-hour period since March 18 at observation points in each prefecture, except quake-hit Fukushima and Miyagi. Cesium-137 is an international indicator for radioactive contamination.

Monitoring data has shown the total fallout of cesium-137 in Hitachinaka, Ibaraki Prefecture, for 18 days through Tuesday morning was 26,399 becquerels per square meter. In Shinjuku Ward, Tokyo, the figure was 6,615 becquerels per square meter.

Rain on March 21-22–the first since the nuclear crisis began–brought down a large amount of cesium-137, spreading the contamination to Tokyo and 13 prefectures in and around the Kanto region.

Although many people believe their lives have been free of radioactive contamination, history shows that radioactive materials were widely dispersed during the 20th century, sometimes dubbed the Atomic Age.

Domestic studies on radioactive fallout date back to 1957, three years after the exposure to radiation of the crew of the tuna boat Fukuryu Maru No. 5 after an atmospheric nuclear test by the United States. One crew member died six months after the incident.

This test took place amid the Cold War when the United States and the Soviet Union conducted a large number of nuclear tests. In 1962 alone, at least 178 nuclear tests took place, dispersing plutonium and other radioactive materials into the atmosphere. In Osaka, 688 becquerels per square meter of cesium-137 was measured in May 1963.

The worst case of radioactive contamination was the accident at the Chernobyl nuclear power plant in Ukraine, then a Soviet republic, in April 1986. About 7 tons of radioactive materials–about 400 times what was released by the atomic bomb dropped on Hiroshima–were released across the Northern Hemisphere. In Kanazawa, cesium fallout was 318 becquerels per square meter in May that year.

Areas within 30 kilometers of the Chernobyl plant were incredibly contaminated–as much as 1.48 million becquerels per square meter in some areas. Residents in these areas were evacuated. In parts of Germany and other nations, more than 70,000 becquerels per square meter were detected. In Belarus and Moldova, also Soviet republics at the time, and other nations such as Austria and Finland, the average amount of fallout exceeded 10,000 becquerels per square meter.

The level of radioactive fallout in Hitachinaka and some other areas in the wake of the Fukushima crisis is believed to be higher than that reported in the 1979 Three Mile Island accident in the United States, and about the same as that reported in Europe after the Chernobyl incident.

Fallout levels in the Kanto region have been decreasing this month. Daily readings have been about the same as the early 1960s when so many nuclear tests were conducted. Some experts have said these levels pose no threat to people’s health. However, highly radioactive water leaked from the Fukushima plant into the ocean could cause severe damage to marine life.


Upper limit changes in a crisis

There are two reference levels for the effects of radiation exposure on health–one for normal times and another for emergencies. The everyday yardstick for radiation exposure for ordinary people is set on the safe side.

According to the International Commission on Radiological Protection (ICRP), the annual intake limit for artificial radioactive substances–excluding natural radiation such as from cosmic rays and from medical devices such as X-rays–is 1 millisievert (mSv) for ordinary people.

A becquerel is a unit for measuring a substance’s radioactivity, and is equal to the number of nuclear decays per second. A sievert is a unit to quantify the biological effects of radiation. Becquerels can be converted into sieverts through a formula that factors in elements including the type of nucleus and type of radiation exposure.

Research on atomic-bomb survivors suggests that the incidence of cancer increases if the radiation dose exceeds 100 mSV. The annual limit of 1 mSv was set on the grounds that if a person is exposed to this level every year until age 80, the total radiation dose will be less than 80 mSv.

But during emergencies, such as an accident at a nuclear power plant, this level is often increased. The Nuclear Safety Commission of Japan has said people should stay indoors if the annual radiation dose exceeds 10 mSV.

The ICRP in 2007 issued an advisory saying the annual radiation limit for ordinary people can be raised to 20 mSv to 100 mSv during an emergency. The ICRP’s suggestion of this temporary level is based on lessons learned from the Chernobyl disaster and other incidents.

“Even if people are exposed to 20 mSv of radiation in a year, they wouldn’t experience any symptoms such as nausea or burns. Raising the upper limit could increase the risk of cancer, but if there are other merits, such as avoiding the need to evacuate, it might be a feasible option,” according to Yasuhito Sasaki, an executive director at the Japan Radioisotope Association.

Whether to change the annual limit on radiation intake from the normal level to an emergency level is decided by the NSC after considering the scale of the radioactive contamination and doses in different areas and reporting on this to the government.

Radiation intake limits for workers at nuclear facilities are set at 100 mSv over five years, but this limit was raised to 250 mSv following the accidents at the Fukushima No. 1 nuclear plant.

The ICRP has also issued an advisory that the emergency exposure limit for rescue and other personnel should be between 500 mSv and 1,000 mSv over five years.

(Apr. 11, 2011)
The Japanese Nuclear and Industrial Safety Agency (NISA) today issued a new provisional rating for the accident at the Fukushima Daiichi nuclear power plant on the IAEA International Nuclear and Radiological Event Scale (INES).

The nuclear accident at Fukushima Daiichi is now rated as a level 7 “Major Accident” on INES. Level 7 is the most serious level on INES and is used to describe an event comprised of “A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures”. Japanese authorities notified the IAEA in advance of the public announcement and the formal submission of the new provisional rating.

The new provisional rating considers the accidents that occurred at Units 1, 2 and 3 as a single event on INES. Previously, separate INES Level 5 ratings had been applied for Units 1, 2 and 3. The provisional INES Level 3 rating assigned for Unit 4 still applies.

The re-evaluation of the Fukushima Daiichi provisional INES rating resulted from an estimate of the total amount of radioactivity released to the environment from the nuclear plant. NISA estimates that the amount of radioactive material released to the atmosphere is approximately 10 percent of the 1986 Chernobyl accident, which is the only other nuclear accident to have been rated a Level 7 event.

Earlier ratings of the nuclear accident at Fukushima Daiichi were assessed as follows:

On 18 March, Japanese authorities rated the core damage at the Fukushima Daiichi 1, 2 and 3 reactor Units caused by loss of all cooling function to have been at Level 5 on the INES scale. They further assessed that the loss of cooling and water supplying functions in the spent fuel pool of the Unit 4 reactor to have been rated at Level 3.

Japanese authorities may revise the INES rating at the Fukushima Daiichi nuclear power plant as further information becomes available.

INES is used to promptly and consistently communicate to the public the safety significance of events associated with sources of radiation. The scale runs from 0 (deviation) to 7 (major accident).

For further information on the INES scale: http://www-ns.iaea.org/tech-areas/emergency/ines.asp

Further details regarding this development can be found in the following NISA press release [pdf]


Japan to raise Fukushima crisis level to worst

NHK World News

The Japanese government’s nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale.

The Nuclear and Industrial Safety Agency made the decision on Monday. It says the damaged facilities have been releasing a massive amount of radioactive substances, which are posing a threat to human health and the environment over a wide area.

The agency used the International Nuclear and Radiological Event Scale, or INES, to gauge the level. The scale was designed by an international group of experts to indicate the significance of nuclear events with ratings of 0 to 7.

On March 18th, one week after the massive quake, the agency declared the Fukushima trouble a level 5 incident, the same as the accident at Three Mile Island in the United States in 1979.

Level 7 has formerly only been applied to the Chernobyl accident in the former Soviet Union in 1986 when hundreds of thousands of terabecquerels of radioactive iodine-131 were released into the air. One terabecquerel is one trillion becquerels.

The agency believes the cumulative amount from the Fukushima plant is less than that from Chernobyl.

Radiation levels exceed permissible limit

The science ministry says the amount of radiation accumulated over about half a month in some areas of Fukushima Prefecture has exceeded the permissible level for a whole year.

Since March 23rd, the ministry has been measuring radiation levels in 15 locations more than 20 kilometers away from the crippled Fukushima Daiichi nuclear power plant.

At one location, in Namie Town about 30 kilometers northwest of the plant, 14,480 microsieverts of radiation had accumulated over the 17-day period to Sunday.
8,440 microsieverts of radiation were observed in Iitate Village.

In another location in Namie, the amount reached 6,430 microsieverts.
People would be exposed to this accumulated amount of radiation if they had stayed outdoors throughout the entire period.

The level at one location was more than 14 times the 1,000 microsieverts that the International Commission on Radiological Protection recommends as the long-term annual reference level for people. The recommended level of 1,000 microsieverts excludes radiation from the natural environment and medical devices.

Hiroshima University Professor Kiyoshi Shizuma says most of the radiation observed in Fukushima is believed to be radioactive cesium that has fallen to the ground.

Shizuma advises residents to wear masks to avoid inhaling radioactive substances mixed with dust.
He points to the need to take samples both from the air and the ground for detailed analyses in order to assess any possible impact on human health.

Monday, April 11, 2011 21:20 +0900 (JST) NHK World News


Greenpeace says that an analysis report prepared by nuclear safety expert Dr Helmut Hirsch shows that by March 23 2011, Japan’s nuclear crisis has already released enough radioactivity to be ranked at Level 7 on the International Nuclear Event Scale (INES). This is the scale’s highest level, and equal to the 1986 Chernobyl nuclear disaster.

Hirsch’s assessment, based on data published by the French government’s radiation protection agency (IRSN) and the Austrian governments Central Institute for Meteorology and Geodynamics (ZAMG) found that the total amount of radionuclides iodine-131 and caesium-137 released between March 11 and March 23have been so high that the Fukushima crisis already equates to three INES 7 incidents.


In the meantime, details are being released on TEPCO’s handling of the crisis in the initial stages, PM Kan’s ability to handle the administration is sliding fast amidst escalating criticism from LDP, decentralized authorities and the local population, and the U.S. is launching charges at the Japanese government for its lack of early information dissemination

TEPCO tardy on N-plant emergencyCriticism within DPJ of Kan, Okada at boiling pointDPJ unable to stop decline / LDP secures No. 1 party spot in 40 prefectural assemblies (Apr.12) | Ishihara easily wins reelection / Tokyo governor takes 4th term; DPJ suffers setback in local polls (Apr.11) | Fukushima Gov. Sato rejects meeting with TEPCO presidentThousands protest N-power amid Fukushima plant crisis (Apr.11)


Fact-box- International nuclear event scale explained

REUTERS – Japan on Tuesday raised the severity level of its nuclear crisis to put it on par with the Chernobyl accident 25 years ago, the worst atomic power in history.

But what does that mean?

The International Atomic Energy Agency (IAEA) — an inter-governmental organization for scientific co-operation in the nuclear field — said it uses the scale to communicate to the public in a consistent way the safety significance of nuclear and radiological events.

The International Nuclear and Radiological Event Scale, or INES, ranges from one to seven. The most serious level is a seven, which refers to a “major accident,” while a one is an “anomaly”. The scale is designed so the severity of an event is about 10 times greater for each increase in level.

The following are some examples of accidents according to their INES level from the IAEA, see http://www.iaea.org/Publications/Factsheets/English/ines.pdf


A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures.

* CHERNOBYL, Soviet Union (now Ukraine), 1986 – An explosion and fire released large quantities of radioactive contamination into the atmosphere, which spread over much of Western Russia andEurope.


A significant release of radioactive material likely to require implementation of planned countermeasures.

* KYSHTYM, Soviet Union (now Russia), 1957 – Significant release of radioactive material to the environment from explosion of high activity waste tank.


A limited release of radioactive material likely to require implementation of some planned countermeasures and several deaths from radiation.

* THREE MILE ISLAND, USA, 1979 – Severe damage to reactor core. This event galvanized opposition to a growing core anti-nuclear power movement in the United States. After this event, energy companies did not start the construction of any new reactors in the United States for over 30 years and stopped work on several reactors that were already under construction.

* WINDSCALE PILE, UK, 1957 – A release of radioactive material following a fire in a reactor core

* GOIANIA, Brazil, 1987 – Four people died and six people received high doses of radiation.


A minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls and fuel melt, or damage to fuel resulting in more than 0.1 percent release of core inventory, and the release of significant quantities of radioactive material within an installation with a high probability of significant public exposure.

* TOKAIMURA, Japan, 1999 – Fatal overexposure of workers following a criticality event at a nuclear facility.

* SAINT-LAURENT-DES-EAUX, France, 1980 – Melting of one channel of fuel in the reactor with no release outside the site.

* FLEURUS, Belgium, 2006 – Severe health effects for worker at a commercial irradiation facility as a result of high doses of radiation.

(Reporting by Bernie Woodall in Detroit and Scott DiSavino in New York, editing by Miral Fahmy)


Japan raises nuclear crisis to on par with Chernobyl

TOKYO (Reuters) – Japan raised the severity of its nuclear crisis at the Fukushima Daiichi nuclear plant to a level 7 from 5, putting it on par with the Chernobyl nuclear disaster in 1986.

The rating reflects the initial severity of the crisis not the current situation which has seen radiation levels drop dramatically.

Japan is struggling to regain control of the Fukushima Daiichi nuclear plant after a massive earthquake and tsunami devastated its northeast on March 11, and is facing a major humanitarian and economic crisis.

The International Nuclear and Radiological Event Scale (INES)ranks nuclear incidents by their severity from 1 to a maximum of 7.

Here are some comments on the higher rating:



“We think it’s very different from the accident in Chernobyl. First of all, the emission of radioactive substances is about 10 percent of the amount of Chernobyl. In the case of Chernobyl, 29 people died due to rapid absorption of massive radiation. That’s not the case in Fukushima.

“In the case of Fukushima, we had an explosion due to leaked hydrogen, blowing the roof off a building but the reactor containment vessel and reactor pressure vessel remains in the original shape, despite some leaks. In the case of Chernobyl, they could not keep working after the accident due to massive leaks of radioactive substances. In Fukushima, we still have engineers working to resolve the situation.”


“I think raising it to the level of Chernobyl is excessive. It’s nowhere near that level. Chernobyl was terrible — it blew and they had no containment, and they were stuck.

“Their containment has been holding, the only thing that hasn’t is the fuel pool that caught fire. I don’t see those as the same event. If they want to do that, that’s fine. I think they’re being overly pessimistic.”


“Raising the level to a 7 has serious diplomatic implications. It is telling people that the accident has the potential of causing trouble to our neighbours.

“I think a level 7 is very extreme.”


“According to the INES rating procedure, a provisional rating is given at the onset of an accident. The rating remains on a provisional status until the accident is deemed over, when a final rating is given upon analysis by a committee of experts. As for Daiichi the problems are still ongoing. This is a preliminary assessment, and is subject to finalisation by the International Atomic Energy Agency.”

(Reporting by Yoko Nishikawa, Mayumi Negishi and Elaine Lees; Editing by Michael Perry)


Q+A: How does Fukushima differ from Chernobyl? By Mayumi Negishi

TOKYO | Tue Apr 12, 2011 8:27am EDT

(Reuters) – Japan on Tuesday raised the severity level of its nuclear crisis to put it on par with the 1986 Chernobyl accident, the world’s worst nuclear power disaster.

But for all their criticism of how Tokyo Electric Power Co and Japan’s government are handling the crisis at the Fukushima Daiichi nuclear power plant, experts agree with them on one point: Fukushima is not another Chernobyl.

“Fukushima has its own unique risks, but comparing it to Chernobyl is going too far. Fukushima is unlikely to have the kind of impact on the health of people in neighboring countries, the way Chernobyl did,” said nuclear specialist Kenji Sumita at Osaka University.

Here are the main points of how the two accidents differ.


Unit 4 at Chernobyl was a water-cooled and graphite-moderated reactor — a combination that can and did yield a runaway chain reaction. A series of gross errors and misjudgment by operators resulted in an explosion and fire that catapulted radioactivity into the upper atmosphere.

The resulting release of radiation has been compared to 10 times that released by the 1945 U.S. nuclear bomb attack on the Japanese city of Hiroshima.

The boiling water reactors at Fukushima do not have a combustible graphite core. The nuclear fuel in reactors No. 1, No. 2 and No. 3 was allowed to melt at least partially, but operators have since succeeded in cooling both the reactors and the spent fuel pools and no chain reaction is happening now.

As long as cooling operations continue and Japan can prepare tanks fast enough to store the contamination overflow, Japan can still hope to buy time to figure out how to bring the reactors to a cold shutdown.


Chernobyl had no containment structure and nothing stopped the trajectory of radioactive materials into the air.

Fukushima’s reactors are built on granite foundations and are surrounded by steel and concrete structures. The reactor vessels and containment structures, as well as some of the pipes leading from the reactors, are likely to have been damaged by the March 11 tsunami and recurring earthquakes. But with radiation levels now down to a sliver of what they were at the peak, experts say that the structures are still holding.

Chernobyl contaminated an area as far as 500 km (300 miles) from the plant, and an area spanning 30 km (18 miles) around the plant is still an exclusion zone and uninhabited.


At Fukushima, there have been no deaths so far due to radiation. Eight people have been injured. More deadly have been the 9.0 magnitude quake that hit on March 11 and the aftershocks that have rocked the site while workers tried to bring the plant under control. Two have died and three have been critically injured.

At Chernobyl, the initial explosion resulted in the death of two workers. Twenty-eight of the firemen and emergency clean-up workers died in the first three months after the explosion from acute radiation sickness and one died of cardiac arrest.


Bungling, yes. Disorganized, incoherent and sometimes contradictory, yes. But it is difficult to accuse Japanese officials or TEPCO of intentionally covering up information, with round-the-clock updates and a steady stream of data.

Chernobyl was initially covered up by the secretive Soviet state, which remained silent for two days. But authorities, obliged by huge radiation releases throughout Europe, gradually disclosed details of the accident, showing unprecedented Soviet-era openness.


It’s not over yet. One month since the March 11 earthquake and tsunami, workers still have to inject water into the reactors, creating more contaminated water that is hampering the restoration of power to pumps to cool the reactors and bring them to a cold shutdown.

The situation led a frustrated and demoralized TEPCO spokesman to say that the total fallout could exceed that of Chernobyl. Fukushima involves loss of control at four reactors and potentially more radioactive material, that could continue to seep, leak or burst into the environment.

Officials have said that if power cannot be restored to the cooling pumps, there are other measures, such as air cooling, and that in a worst-case scenario, they could try water entombment in the reactors whose containment structures are sound.


At the Diplomat’s Blog, How Bad is Fukushima, Alexander Sich says that people don’t know how to read data figures and are frightened by the seemingly high number of 10,000 terabecquerels, and disagrees with the 7 rating saying that it is “grist for the sensationalist mill”… read more and also Nuclear Experts: Japan’s nuclear disaster will have limited reach

See also Doc’s Green Blog’s Fukushima vs. Chernobyl comparison for more perspectives on this.


U.S. ‘frustrated’ over Japan’s lack of N-information | High radiation well past no-go zone: Greenpeace

For those who want to look at what happened at Chernobyl, since Chernobyl is frequently used by the press as a basis for comparison, see:

20 Years Later a UN Report Provides Definitive Answers and Ways to Repair Lives (5 SEPTEMBER 2005 | GENEVA)

The new numbers are presented in a landmark digest report, “Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts,” released by the Chernobyl Forum. The digest, based on a three-volume, 600-page report and incorporating the work of hundreds of scientists, economists and health experts, assesses the 20-year impact of the largest nuclear accident in history. The Forum is made up of 8 UN specialized agencies, including the International Atomic Energy Agency (IAEA), World Health Organization (WHO), United Nations Development Programme (UNDP), Food and Agriculture Organization (FAO), United Nations Environment Programme (UNEP), United Nations Office for the Coordination of Humanitarian Affairs (UN-OCHA), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the World Bank, as well as the governments of Belarus, the Russian Federation and Ukraine. The Forum’s report aims to help the affected countries understand the true scale of the accident’s consequences and also suggests ways the governments of Belarus, the Russian Federation and Ukraine might address major economic and social problems stemming from the accident. Members of the Forum, including representatives of the three governments, will meet September 6 and 7 in Vienna at an unprecedented gathering of the world’s experts on Chernobyl, radiation effects and protection, to consider these findings and recommendations. The report is in two parts