The Secretary is authorized to hire qualified personnel necessary to carry out the Secretary’s duties under subsection (a), under section
1418 of this title, and under part D of subchapter IV, without regard to the provisions of title 5 relating to appointments in the competitive service and without regard to chapter 51 and subchapter III of chapter 53 of such title relating to classification and general schedule pay rates, except that no more than 20 such personnel shall be employed at any time.