The most range of electricity pie chart is thermal power as a 33% in Korea.  Changes:  On a pie chart of the sources of electricity in Korea, thermal power is the largest share, at 33%.
Next is nuclear which we can be easy to mistake that it would be first.  This is followed by nuclear energy, which one might have expected to be the largest share of the chart.
After the disaster in japan, Korea is trying to decrease dependency of nuclear power due to potential risks of nuclear.
According to global trend of alternative energy, Korean government is struggling to grow up the industry to replace the reduced energy gap.  (Because orea has taken action since the Japanese disaster, change the tense of this sentence to be:)  Since the nuclear disaster in Japan, Korea has tried to decrease its dependency on nuclear power. thereby lowering the risk of a similar tragedy.
Although the renewable energy is 9.5% at this moment,i hope all people regarding this industry should do their best to save our wonderful earth.  Renewable energe comprises only 9.5% of the pie chart at the moment.  I hope that the decision makers in the industry will devote their best efforts to increase that number in order to save our wonderful planet.

This was a fine effort on your part, Yongbeom!  Notice, please, that I reconstructed your sentences to fall in line with the principles mentioned in my paper on business English.  I have made your sentences more concise and direct.  This structure leade your reader from eash idea to the next logical idea.  Let's discuss this during Monday's class.  Enjoy the rest of your weekend!