enactment of this Act providing for a one-time submission of claims covering periods described in the preceding sentence. Such guidance shall provide for a 180-day period for the submission of such claims (in such manner as prescribed by such Secretary) to begin not later than 30 days after such guidance is issued. Such claims shall be paid by such Secretary not later than 60 days after receipt. If such Secretary has not paid pursuant to a claim filed under this subsection within 60 days after the date of the filing of such claim, the claim shall be paid with interest from such date determined by using the overpayment rate and method under section 6621 of such Code. 316. Extension of Oil Spill Liability Trust Fund financing rate (a) In general Section 4611(f)(2) is amended by striking December 31, 2017 and inserting December 31, 2018 . (b) Effective date The amendment made by this section shall apply on and after January 1, 2018. IV Modifications of energy incentives 401. Modifications of credit for production from advanced nuclear power facilities (a) Treatment of unutilized limitation amounts Section 45J(b) is amended— (1) by inserting or any amendment to after enactment of in paragraph (4), and (2) by adding at the end the following new paragraph: (5) Allocation of unutilized limitation (A) In general Any unutilized national megawatt capacity limitation shall be allocated by the Secretary under paragraph (3) as rapidly as is practicable after December 31, 2020— (i) first to facilities placed in service on or before such date to the extent that such facilities did not receive an allocation equal to their full nameplate capacity, and (ii) then to facilities placed in service after such date in the order in which such facilities are placed in service. (B) Unutilized national megawatt capacity limitation The term unutilized national megawatt capacity limitation means the excess (if any) of— (i) 6,000 megawatts, over (ii) the aggregate amount of national megawatt capacity limitation allocated by the Secretary