Fukushima Daiichi NPS Prompt Report 2013

This is a follow-up report on the statuses of steam-like gas found wafting through the air near the central part of the fifth floor(equipment storage pool side) of Unit 3.

Please refer to the following dust analysis result, sampled near the steam-like gas wafting place.

[Dust analysis result at the top of the Unit 3]

    Iodine 134: below the detection limit

    Cesium 134: 4.0×10^-5 Bq/cm3

    Cesium 137: 7.1×10^-5 Bq/cm3

For a half year, Cesium 137 has varied between 1.0×10^-3 Bq/cm3 and 1.0×10^-5, Cesium 134 has varied between 5.0×10^-4 Bq/cm3 and 1.0×10^-5Bq/cm3. The results today were between these ranges and there were data over the detection limits*.

* Detection limits

　　　Iodine 131 volatile:7.0×10^-6 Bq/cm3, granulous:4.2×10^-6 Bq/cm3　　

　　　Cesium 134 volatile:1.5×10^-5 Bq/cm3, granulous:8.2×10^-6 Bq/cm3　

　　　Cesium 137 volatile:2.1×10^-5 Bq/cm3, granulous:1.1×10^-5 Bq/cm3　

Given the result and the status of the plant, we assume that the steam was generated as a result of that rain has leaked through gaps near the cover and has heated at the head of the primary containment vessel.

We will continue to monitor the status closely.