JNES Calculation of the Amount of Radioactive Materials Released from #Fukushima I Nuke Plant

Japan Nuclear Energy Safety Organization (JNES), an independent administrative corporation under the Ministry of Economy, Trade and Industry, issued the result of its calculation of radioactive amounts released from Fukushima I Nuclear Power Plant in the first week of the nuclear accident.

From JNES presentation (3/27/2013), unit is petabecquerel (1x10^15) and 1 petabecquerel is 1,000 terabecquerels:

From March 11 to March 17, 2011,

I-131: 250 to 340 petabecquerels (or 250,000 to 340,000 terabecquerels)
Cs-134: 8.3 to 15 petabecquerels (or 8,300 to 15,000 terabecquerels)
Cs-137: 7.3 to 13 petabecquerels (or 7,300 to 13,000 terabecquerels)

For I-131, JNES's calculation, which is based on the accident progress analysis, is closest to TEPCO's number which is the highest (500 petabecquerels, or 500,000 terabecquerels).

In the image below (English labels added by me), from the top row, the entities that did the analysis are:

• Japan Nuclear Energy Safety Organization (JNES)

• TEPCO

• Japan Atomic Energy Agency (JAEA)

• Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

• Central Research Institute of Electric Power Industry (CRIEPI)

All except JNES based their calculation on the actual measurement of radioactive materials.

I find it interesting that JNES's calculation shows potentially more Cs-134 than Cs-137. From the actual measurements on the ground, I believe the ratio has been 1:1 to 1:1.2.

On the night of March 11, 2011, the now-defunct Nuclear and Industrial Safety Agency (NISA) had JNES do the simulation using the Emergency Response Support System (ERSS) to predict the progression of the accident. JNES faxed the result of the simulation for Reactor 2 to NISA as early as 9PM on March 11, the simulation for Reactor 1 by noon on March 12 (more than three hours before the explosion), and the simulation for Reactor 3 at 6:30AM on March 13. The faxed results for Reactor 2 was delivered to the Prime Minister's Official Residence just past midnight on March 11 (early hours of March 12). (Jiji Tsushin, 9/3/2011)

No one acted on them.

NISA was trying to figure out the areas to have people evacuate. In addition to ERSS, the agency also ordered SPEEDI simulations done, using the information that the agency collected on its own. The agency dropped that effort when Prime Minister Kan and his ministers thought they knew best and drew concentric circles around the plant and decided the evacuation zones, ignoring the emergency protocol that specifically said they should use SPEEDI simulations for that purpose. (Asahi Shinbun's "Trap of Prometeus" Part 2)

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Diet Independent Investigation Commission Report: Fuel Debris Re-Melt of Reactor 3 May Have Caused March 21 and 22, 2011 Spike in Radiation Levels

On page 243 of its 646-page main report (available in Japanese only, for now), the National Diet Independent Investigation Commission on the Fukushima I Nuclear Power Plant accident speculates on the causes of the spikes in radiation levels at monitoring stations in March 2011. (This particular page was mentioned in a tweet by Professor Ryugo Hayano at Tokyo University Physics Department.)

The Commission seems to have concluded that Reactor 1 released large amounts of radiation on March 15 and 16, and again on March 21, 2011. It also suspects the fuel debris (corium) re-melt of Reactor 3 for the spike of radiation on March 21 and 22, 2011. In the latter, the Commission cites a research paper by Fumiya Tanabe published earlier this year but was reported in August last year.

(Tanabe is the one who also said Reactor 2 Suppression Chamber and Dry Well were damaged in the earthquake, and the efforts to vent released a large amount of radioactive materials from the breaches.)

The particular section discusses the recriticality issues and the hydrogen explosion in Reactor 4. The Commission writes in the subsection titled "a. outside monitoring data" that says (my personal translation):

We referred to the outside monitoring data regarding the short-lived nuclides that are produced should the recriticality occur.

At the CTBT Monitoring Post in Takasaki City in Gunma Prefecture, increased amounts of nuclides, including the short-lived nuclides, were sampled and observed around March 15 [2011]. However, we cannot deny the possibility that they were produced during the course of the regular reactor operation [as opposed to being produced by recriticality] or that they were decay products of such nuclides.

According to the measurement by the Japan Chemical Analysis Center, the amount of tellurium-129, iodine-132, and xenon-133 showed rapid increase, but it is likely that they were originated in the normal reactor operation.

From these monitoring data, we cannot find the data that clearly shows recriticality was taking place. However, it is apparent that there were large-scale releases of radioactive materials from Reactor 1 on March 15 and 16, and on March 21. The release of radioactive materials between March 15 and 17 is likely to have been caused by the damaged S/C (Suppression Chamber) and D/W (Dry Well) of Reactor 2, and by the Reactor 3 vent and the hydrogen explosion. As to the rise on March 21 and 22, we need to consider the possibility of the fuel debris re-melt in Reactor 3.

Well, in other words, we still don't know what happened and how it happened after 16 months. The Diet Commission quotes the data and research papers, but all it can do is to suspect everything, and ends up listing all possible causes for the releases of radioactive materials. I read the tweets between the researchers (including Professor Hayano who tweeted this particular page). They are nowhere near any conclusion.

The only thing that is notable for me is the mention of Reactor 1 as a large source of radioactive materials. Both TEPCO's and the government institutions' analyses indicate the release from Reactor 2 was an order of magnitude bigger than other reactors. I guess I will have to read the 646-page report to see if they have the data to back up their assertion about Reactor 1.

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TEPCO: 900,000 Terabecquerels (Iodine Equivalence) Released into the Air from #Fukushima I Nuke Plant in March 2011

TEPCO has come up with the latest estimate of the radioactive materials released from Fukushima I Nuclear Power Plant, and it is higher than everyone else's, at 900,000 terabequerels (iodine-131 equivalence) for the month of March, 2011.

Iodine 131: 500,000 terabequerels
Cesium 134: 10,000 terabecquerels
Cesium 137: 10,000 terabequerels

To conform to the INES, TEPCO multiplied the amount of cesium 137 by 40 to get the iodine equivalence (10,000 x 40 = 400,000). However, TEPCO did not use cesium-134 so that the total number could be compared with the numbers from other institutions.

Iodine equivalence of cesium 134 can be obtained by multiplying by 3. In the big scheme of things, the amount is negligible, as it would increase the total 900,000 terabequerels by only 30,000 becquerels.

From TEPCO's English press release (5/24/2012):

The Estimated Amount of Radioactive Materials Released into the Air and the Ocean Caused by Fukushima Daiichi Nuclear Power Station Accident Due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake (As of May 2012)

Due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake which occurred on March 11, 2011, TEPCO's facilities including our nuclear power stations have been severely damaged. We deeply apologize for the anxiety and inconvenience caused.

With regard to the accident at Fukushima Daiichi Nuclear Power Station, on April 17, 2011, we have compiled the roadmap towards restoration from the accident and on July 19 we accomplished the Step1 target "Radiation dose is in steady decline". Then on December 16 we confirmed the accomplishment of the Step 2 target "Release of radioactive materials is under control and radiation doses are being significantly held down". In addition, on December 21, 2011, we have compiled the "Mid-to-long-Term Roadmap toward the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4, TEPCO", for which we're currently working towards.

Along with the roadmaps mentioned above, we have been evaluating the amount of radioactive materials released into the air and the ocean as a result of the accident. The evaluation result (as of May 2012) is provided below.

As for the amount of radioactive materials released into the air, the evaluation was done from March 12 to 31, 2011. The estimated release amounts are as follows.
Noble gas: Approx. 5x10^17 Bq
Iodine 131: Approx. 5x10^17 Bq
Cesium 134: Approx. 1x10^16 Bq
Cesium 137: Approx. 1x10^16 Bq

The amounts of radioactive materials released in April and later in 2011 are not taken into account in this evaluation result as the released amounts were less than 1% of that in March 2011, which are considered to be insignificant.

As for the amount of radioactive materials released into the ocean, the evaluation was done from March 26 to September 30, 2011. The estimated release amounts are as follows.
Iodine 131: Approx. 1.1x10^16 Bq
Cesium 134: Approx. 3.5x10^15 Bq
Cesium 137: Approx. 3.6x10^15 Bq

As the equipments to directly measure the density of radioactive materials (such as the exhaust stack monitor) were unavailable due to the accident, the amount of radioactive materials released into the air was estimated by entering the measurement data (air dose rate, wind direction and wind speed) acquired by the monitoring cars in the power station and the observed values provided by the Japan Meteorological Agency into a program which calculates the amount of radioactive materials diffused into the air, with an assumption that the release rate of radioactive nuclides remains consistent. The evaluation result was then compared with the contamination density measurement result of soil provided by the Ministry of Education, Culture, Sports, Science and Technology, and our evaluation result has been validated.

However, further data still needs to be collected to review the validity of our evaluation result, considering that the data was acquired only in a limited area (in the power station site) and that the evaluation was done under the assumption that the release rate of radioactive nuclides is consistent though it should actually vary for each nuclide and depending on the status of reactors (the release rate was estimated based solely on the small amount of data obtained during the evaluation period).

The amount of radioactive materials released into the ocean was estimated based on the monitoring data of radioactivity density of materials included in the seawater near the north/south water discharge channels at the power station. The evaluation was done at the Central Research Institute of Electric Power Industry by utilizing a program which calculates the diffusion of radioactive materials into the ocean.

However, further data still needs to be collected to review the validity of our evaluation result, considering that the evaluation was done based on a small amount of data acquired in a limited area (monitoring data of radioactivity density of materials included in the seawater near the north/south water discharge channels at the power station), and that individual evaluation was not done for each release factor (radioactive materials directly released from the power station, fallouts from the air, rainwater inflow, etc.).

We will continue our utmost efforts in maintaining the stable condition of our nuclear power stations and implementing the measures to decommission Units 1-4.

Attachments and reference information are available only in Japanese for now. TEPCO says they are being translated. However, the report itself is only available in Japanese. (It is likely to be "instruction" from the NISA, as before.)

I am reading the report, which has a specific mention of radiation contamination in the north-west corridor from the plant (Namie-machi, Iitate-mura) on March 15, 2011. (That will be a separate post later.)

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French Researchers: Lower Bound Estimates of Atmospheric Release of Iodine, Cesium from Fukushima "about 5 to 10 times less than the Chernobyl atmospheric releases"

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, D05122, 16 PP., 2012 (Received 27 September 2011; accepted 23 January 2012; published 9 March 2012)

Estimation of errors in the inverse modeling of accidental release of atmospheric pollutant: Application to the reconstruction of the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant

Victor Winiarek

CEREA, École des Ponts ParisTech–EDF R&D, Université Paris-Est, Marne la Vallée, France

INRIA Rocquencourt Research Centre, Paris, France

Marc Bocquet

CEREA, École des Ponts ParisTech–EDF R&D, Université Paris-Est, Marne la Vallée, France

INRIA Rocquencourt Research Centre, Paris, France

Olivier Saunier

Institute of Radiation Protection and Nuclear Safety, Fontenay-aux-Roses, France

Anne Mathieu

Institute of Radiation Protection and Nuclear Safety, Fontenay-aux-Roses, France


A major difficulty when inverting the source term of an atmospheric tracer dispersion problem is the estimation of the prior errors: those of the atmospheric transport model, those ascribed to the representativity of the measurements, those that are instrumental, and those attached to the prior knowledge on the variables one seeks to retrieve. In the case of an accidental release of pollutant, the reconstructed source is sensitive to these assumptions. This sensitivity makes the quality of the retrieval dependent on the methods used to model and estimate the prior errors of the inverse modeling scheme. We propose to use an estimation method for the errors' amplitude based on the maximum likelihood principle. Under semi-Gaussian assumptions, it takes into account, without approximation, the positivity assumption on the source. We apply the method to the estimation of the Fukushima Daiichi source term using activity concentrations in the air. The results are compared to an L-curve estimation technique and to Desroziers's scheme. The total reconstructed activities significantly depend on the chosen method. Because of the poor observability of the Fukushima Daiichi emissions, these methods provide lower bounds for cesium-137 and iodine-131 reconstructed activities. These lower bound estimates, 1.2 × 10^16 Bq for cesium-137, with an estimated standard deviation range of 15%–20%, and 1.9 − 3.8 × 10^17 Bq for iodine-131, with an estimated standard deviation range of 5%–10%, are of the same order of magnitude as those provided by the Japanese Nuclear and Industrial Safety Agency and about 5 to 10 times less than the Chernobyl atmospheric releases.

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Researchers at CEREA created the simulation map of cesium-137 deposition across the Pacific Ocean last year.

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