If, during the 6-month period beginning on the date of a repayment of a loan financed by an issue 95 percent or more of the net proceeds of which are used to provide projects described in section
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(d), such repayment is used to provide a new loan for any project so described, any bond which is issued to refinance such issue shall be treated as a refunding issue to the extent the principal amount of such refunding issue does not exceed the principal amount of the bonds refunded.