Heat Generation in Fukushima Power Reactors is a 0.3% level as of March 21

 

Reactors No.1 through 3 were shut down on March 11 due to the earthquake.

 

The heat generated after the shut down, called the decay heat generation, has been assumed to be about 5% of the power level at the time of shut down. This decay heat was the cause of fear particularly because the ECCS failed.

 

However, the amount of decay heat generation declines with time. Therefore, we estimate the amount of decay heat generated at the 11th day after the shut down (March 22, 2011).

 

The figure below shows estimated decay heat as a ratio to the full power. There are three curves in the figure, which are under different assumptions, but they are mostly close to each other for the time of 10~11th day after the shut down. The ratio is 0.003 or 0.3% of the full power, nearly one twentieth (1/20) of the level at the time of shut down. This is a good news because the possibility of core melt down is far less now than during the first few days after the shutdown. Also, managing the decay heat is much easier now.

 

At the 115th day after the shut down, the level becomes approximately 0.1%.

 

 

Note 1E4=0.12 days, 1E6=11days, 1E7=115 days, 1E8=1150 days

Decay Power = Decay Heat Generated

 

 

References

http://prr.hec.gov.pk/Chapters/1335-9.pdf

Decay Heat Generation in Fission Reactors

Decay Heat Estimates for MNR