Is maturity amount of nhai/rec bond after 3 years taxable?

Dear CAclubIndia Member/experts,

I have just sold the ancestral property of my father. For saving purpose if i invest 50,00,000/- in NHAI/REC bond u/s 54EC will the Maturity Amount be Taxable?

Though interest earned on these will be taxed under income from other source. Will the Principal amount received after 3 years be taxed again? or can i invest the same in any manner i want to?

Thanks in advance.