Japan Nuclear Disaster Models From 2002

A Japan Atomic Energy Institute paper from 2002 recently surfaced online. This paper was the technical estimations of what would happen if a nuclear reactor on the Pacific coast of Japan were to have a catastrophic accident. The models included radiation dispersal under a variety of scenarios and also illness and death rates under multiple scenarios.

The plant for the experiment is  “1100MWe BWR5 with Mark-II type containment– One of the most common plant type in Japan“. Based on the location on the maps included in the paper the reactor used was either unit 6 at Fukushima Daiichi or one of units 1-4 at Fukushima Daini. The scenario is for one reactor failure, not 3 reactor failures plus spent fuel pools as was experienced at Fukushima Daiichi.

Of the included reactor scenarios the one that closest resembles the Fukushima disaster is failure of cooling + overpressure damage. Below are two graphs, one in English, another in Japanese. They show the reactor damage scenarios, distance from the plant and mortality.

Some interpretations of the data in this report using the closest to Fukushima Daiichi model available. These do not mean specifically these things will happen, this is what the model shows under the scenario details they used:

The model used does not differentiate between a unit 2 style containment failure and a unit 3 or Chernobyl style containment failure. A containment failure can vary greatly in how much of the nuclear fuel is released into the environment.

The containment system in the model reactor is newer, technically improved and larger than the containment used in units 1-4 at Fukushima Daiichi. Unit 1 at Fukushima Daiichi has a slightly smaller containment than units 2-4. There have been concerns expressed that the smaller containment had less volume, making it more prone to failure. These slight differences in the reactors would result in changes to the amount of radiation released and would then change all these other outcomes.

20 km away will cause max. 1 out of 500 deaths, an exclusion zone of 100 km will cause max. 1 out of 5000 deaths. The diagram may explain the 20 km exclusion zone. all curves go down beond 20 km away from the plant.

Acute deaths = deaths for direct exposure to NPP wave radiaton + explosion deaths.
The two sharply-dropping lines on the Japanese chart show acute death.
Please make note that at 100 Km. distance values are not 0. Moreover X axis is logarithmic.

Tokio-Fuku distance= 230 Km. Our estimate for 230 Km. death rate ~ 10*-4.Tokio Metropolis population 34,500,000 (2007)34500000/10000.  3450 deaths in Tokio only.
Again, this is based on this model scenario, not exact situations currently going on.
These mortality models include late onset cancers and also survivable cancers based on
the details in the report.

There’s the MOX factor to consider too, the addition of MOX fuel is not included in the model. MOX fuel in reactor 3 may have played a role in the speed of the meltdown and adds plutonium and related isotopes into the releases different than what would be seen with uranium fuel.

The report in English, includes a series of PowerPoint slides at the end.
*This report also talks at length about ways radiation is absorbed by people, they may
not be included in the Japanese language report.

The report in Japanese as part of a JAERI journal

JAERI report that explains the OSCAAR modeling system in English

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