If at any time the moneys available in the fund are insufficient to enable the Secretary of Energy to discharge his responsibilities under this subchapter, he shall issue to the Secretary of the Treasury notes or other obligations in such forms and denominations bearing such maturities, and subject to such terms and conditions, as may be prescribed by the Secretary of the Treasury. This borrowing authority shall be effective only to such extent or in such amounts as are specified in appropriation Acts. Such authorizations may be without fiscal year limitations. Redemption of such notes or obligations shall be made by the Secretary of Energy from appropriations or other moneys available under this section. Such notes or other obligations shall bear interest at a rate determined by the Secretary of the Treasury, which shall not be less than a rate determined by taking into consideration the average market yield on outstanding marketable obligations of the United States of comparable maturities during the month preceding the issuance of the notes or other obligations. The Secretary of the Treasury shall purchase any notes or other obligations issued hereunder and for that purpose he is authorized to use as a public debt transaction the proceeds from the sale of any securities issued under chapter
31 of title
31, and the purposes for which securities may be issued under that chapter are extended to include any purchase of such notes or obligations. The Secretary of the Treasury may at any time sell any of the notes or other obligations acquired by him under this subsection. All redemptions, purchases, and sales by the Secretary of the Treasury of such notes or other obligations shall be treated as public debt transactions of the United States.