Deciphering the measured ratios of Iodine-131 to Cesium-137 at the Fukushima reactors

TL;DR

This paper analyzes the ratio of Iodine-131 to Cesium-137 in Fukushima reactors to determine the timing of nuclear reaction cessation, combining theoretical calculations with real plant data.

Contribution

It provides a method to infer the shutdown time of nuclear reactions using isotope ratio measurements at Fukushima.

Findings

Calculated isotope ratios match observed data

Ratios indicate the reactor shutdown occurred within a specific timeframe

Method can be applied to other nuclear accident assessments

Abstract

We calculate the relative abundance of the radioactive isotopes Iodine-131 and Cesium-137 produced by nuclear fission in reactors and compare it with data taken at the troubled Fukushima Dai-ichi nuclear power plant. The ratio of radioactivities of these two isotopes can be used to obtain information about when the nuclear reactions terminated.