an "official use only" report obtained by foia from the us nuclear regulatory commission (3/18/2011) written one week after the tsunami hit fukushima states, “the source term provided to narac was: (1) 25% of the total fuel in unit 2 released to the atmosphere, (2) 50% of the total spent fuel from unit 3 was released to the atmosphere, and (3) 100% of the total spent fuel was released to the atmosphere from unit 4.” narac produced a "worst case" speculative model based on these assumptions. however, this model did not include an assumption of a release from unit 1, and the assumption of "100% of the total spent fuel was released to the atmosphere from unit 4" has since been proven incorrect with the subsequent removal of the fuel from the spent pool fuel.