In carrying out the purposes of this chapter the Commission shall not use the cost-plus-percentage-of-cost system of contracting.

No contract entered into under the authority of this chapter shall provide, and no contract entered into under the authority of the Atomic Energy Act of 1946, as amended, shall be modified or amended after August 30, 1954, to provide, for direct payment or direct reimbursement by the Commission of any Federal income taxes on behalf of any contractor performing such contract for profit.