New Fukushima Radiation Release Estimates Compiled

Fukushima Radiation Release Estimates

This is one of the questions we are asked the most, “how much radiation was released from Fukushima”. Many of the estimates out there are old initial estimates of the meltdown phase and do not include radiation releases over the years.

In our effort to answer this question we found a wide variety of research and estimates. With time researchers were able to use other tools and testing to create a better idea about how much has been released.

These estimate ranges are presented to give an idea of the broad range of official estimates and are not a specific scientific study. What these widely divergent estimates show is that there is a need for a more honest and accurate study of this issue.


Fukushima Vs. Chernobyl

We looked at these two disasters since they are frequently compared to each other. The extremely high levels, all in petabecquerels are problematic even if there is a considerable difference between the two.

Fukushima Releases To The Air

These numbers were established by using the range of estimates that were either “all radiation”  or at least included cesium 137 and iodine 131 for the initial phase of the disaster. The estimates for the years following the accident are based on TEPCO’s admitted hourly release rates. These totals are for the time period through December 12, 2013

Air high:   16886 Pbq
Air low:         900 Pbq

Fukushima Releases To The Sea

These numbers include initial releases and also over time releases based on oceanography institute estimates. These totals are for the time period through December 12, 2013

Sea high:     960 Pbq
Sea low:       520 Pbq

*Does not include radiation that escaped via air but fell into the sea or that washed out to sea via rivers.

Fukushima Combined Releases To Sea & Air

Combined high: 17846 Pbq (74.5% of total inventory at the plant)
Combined low:     1420 Pbq (5.9% of total inventory at the plant)

Chernobyl Release Estimates

The release estimates provided by UNSCEAR were used for comparison.
Air:               8385 Pbq
Sea:                 20 Pbq
Combined:  8405 Pbq


Combined Air & Sea Releases

Fukushima Radioactive Inventory

The total number of assemblies on site as either reactor fuel or spent fuel at Fukushima Daiichi is 14605. This includes units 1-6 and the common pool. Based on TEPCO’s statements cited by UPI we backtracked to get a rough estimate of the radiation potential per assembly. We came up with a rough number of 1.64 Pbq per assembly. Radiation levels would be varied per assembly depending on the age of any spent fuel, with older fuel having less inventory available due to decay. If anything this estimate would be an overestimate of the plant inventory that could be potentially released.


Number of assembles

Inventory in Pbq

Total in reactors 1-3



Total in SFP 1-4 plus common pool



Combined total at risk there 1-4



Plant total including units 5-6 reactor and SFPs



It is assumed that most of the radiation releases were from units 1-3 out of the reactor with some potential from the spent fuel pools.


Release Estimates Vs. Plant Inventory

This graph shows how drastic the high end of the radiation releases at the plant is when compared to the total inventory at the plant. TEPCO gave some estimates of what they think is the percentage of each melted down unit to be released to the atmosphere during the initial disaster.

Unit 1 = 20% released (130 Pbq)
Unit 2 = 40% released (360 Pbq)
Unit 3 = 35.5% released (230 Pbq)

*TEPCO considers 110 Pbq of releases to have an unknown source and a total initial release at the plant of 900 Pbq



Fukushima High Estimates:

To Air




To Sea




Fukushima Low Estimates:

To Air



To Sea



Fukushima Inventory & Percentages


Chernobyl Release Estimates

More information can be found in our spreadsheet where we collected a variety of research sources into the radiation release estimates. Please cite us as a source for any republication of any of this data and please do not reproduce any of our work in whole without permission.

This article would not be possible without the extensive efforts of the SimplyInfo research team
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