20 U.S.C. § 9105

(a) In general The Director may, in accordance with applicable provisions of title 5, appoint and determine the compensation of such employees as the Director determines to be necessary to carry out the duties of the Institute. (b) Appointment and compensation of technical and professional employees (1) In general Subject to paragraph (2), the Director may appoint without regard to the provisions of title 5 governing the appointment in the competitive service and may compensate without regard to the provisions of chapter 51 or subchapter III of chapter 53 of such title (relating to the classification and General Schedule pay rates), such technical and professional employees as the Director determines to be necessary to carry out the duties of the Institute. (2) Number and compensation (A) In general The number of employees appointed and compensated under paragraph (1) shall not exceed ⅕ of the number of full-time regular or professional employees of the Institute. (B) Rate of compensation (i) In general Except as provided in clause (ii), the rate of basic compensation for the employees appointed and compensated under paragraph (1) may not exceed the rate prescribed for level GS–15 of the General Schedule under section 5332 of title 5 . (ii) Exception The Director may appoint not more than 3 employees under paragraph (1) at a rate of basic compensation that exceeds the rate described in clause (i) but does not exceed the rate of basic pay in effect for positions at level IV of the Executive Schedule under section 5315 of title 5 . (c) Voluntary services The Director may accept and utilize the voluntary services of individuals and reimburse the individuals for travel expenses, including per diem in lieu of subsistence, in the same amounts and to the same extent as authorized under section 5703 of title 5 for persons employed intermittently in Federal Government service. (d) Experts and consultants The Director may use experts and consultants, including panels of experts, who may be employed as authorized under section 3109 of title 5 .