[Reactor4] Exposure dose to remove the lid of PCV4 was 7.8 timers higher than new fuel from SFP4

Tepco removed the lid of PCV4 on 8/10/2012. It’s supposed to be a part of the entire removal process of spent fuel assemblies in SFP4, but Tepco did not announce more specific reason to remove it.

They are to remove the lid of RPV4 by early October.

The exposure dose of the workers was remarkable. 36 workers were involved and the highest reading of the exposure dose was 0.39 mSv for 15 minutes work. It’s 1.56 mSv/h.

Tepco estimated the exposure dose would be 0.8 mSv/d, which is only 0.03 mSv/h.

The actual exposure dose was 52 times higher than estimated.

Also, when they removed the new fuel from SFP4 in July, the highest exposure dose was 0.62 mSv for 3 hours work, which is 0.20 mSv/h. (cf. [Reactor4] Photos and videos to take out the new fuel assemblies)

The exposure dose to remove the lid of PCV4 was 7.8 times higher than the one to remove the new fuel assemblies from SFP4. [Link]

The graph is below to compare. By the way, according to Tepco’s announcement, there was no fuel in PCV4 supposedly.

 

 

 

↓ Tepco’s handout about the removal of PCV4 lid. [Link]

 

 

 

↓Video released by Tepco [Link]

Iori Mochizuki