EXHIBIT 10.1

SECOND AMENDMENT TO AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT

This SECOND AMENDMENT TO AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT dated
as of October 16, 2006 (this “Amendment”), among USEC INC., a Delaware
corporation (“Holdings”), UNITED STATES ENRICHMENT CORPORATION, a Delaware
corporation (“Enrichment” and, together with Holdings, the “Borrowers”), the
LENDERS UNDER THE CREDIT AGREEMENT REFERRED TO BELOW WHICH ARE PARTY HERETO,
JPMORGAN CHASE BANK, N.A., as Administrative and Collateral Agent (the
“Administrative Agent”), and THE OTHER FINANCIAL INSTITUTIONS WHICH ARE NAMED IN
THE CREDIT AGREEMENT AS “AGENTS” THEREUNDER WHICH ARE PARTY HERETO, amends the
Amended and Restated Revolving Credit Agreement dated as of August 18, 2005, as
previously amended by that certain First Amendment to Amended and Restated
Revolving Credit Agreement dated as of March 6, 2006 (as amended, the “Credit
Agreement”), among the Borrowers, the Lenders party thereto, the Administrative
Agent and the other financial institutions named therein as “agents” thereunder.

WHEREAS, the Borrowers have requested that the terms “Availability”, “Borrowing
Base Reserves (Inventory)” and “Collateral Availability” as defined in
Section 1.01 of the Credit Agreement be amended to provide for the Senior Note
Reserve (as defined in the Credit Agreement) to be included within the term
Borrowing Base Reserves (Inventory) rather than separately deducted from the
calculation of Availability and Collateral Availability; and

WHEREAS, the Administrative Agent and the Lenders are willing to amend
Section 1.01 of the Credit Agreement to revise the terms “Availability”,
“Borrowing Base Reserves (Inventory)” and “Collateral Availability” as provided
herein, subject to the terms and conditions set forth herein;

NOW, THEREFORE, in consideration of the foregoing and the agreements contained
herein, the parties hereby agree as follows:

1. Capitalized Terms.

Capitalized terms used herein which are defined in the Credit Agreement have the
same meanings herein as therein, except to the extent that such meanings are
amended hereby.

2. Amendments to Section 1.01 of the Credit Agreement.

Subject to the satisfaction of the terms and conditions set forth in Section 4
hereof and in reliance on the representations set forth in Section 3 hereof, the
Borrowers, the Lenders and the Administrative Agent agree that Section 1.01 of
the Credit Agreement be and it hereby is amended, by deleting the terms
“Availability”, “Borrowing Base Reserves (Inventory)” and “Collateral
Availability” and replacing them with the following new terms:

“‘Availability’ means, at any time, the difference between (a) the lesser at
such time of (i) the aggregate Commitments of all Lenders and (ii) the Borrowing
Base, and (b) the sum at such time of (i) the unpaid principal balance of the
Loans and all accrued interest, fees and expenses plus (ii) the LC Exposure.”

“‘Borrowing Base Reserves (Inventory)’ means, as of any date of determination,
such reserves in amounts as the Administrative Agent may from time to time
establish and revise (upward or downward) in its Permitted Discretion upon
reasonable prior notice to the Credit Parties to reflect, among other things:
(a) potential material adverse landlord claims resulting from the absence of
landlord waivers, environmental costs, rent, the cost of tails disposition not
otherwise covered by surety bonds or Letters of Credit and estimated DOE Lease
Turnover Obligations, (b) potential shortfalls in inventory of (i) natural
uranium meeting applicable ASTM specifications needed to meet the Credit
Parties’ obligations to Customers and/or (ii) enriched uranium meeting
applicable ASTM specifications needed to meet the Credit Parties’ obligations to
Customers, (c) potential mark-to-market costs, (d) inventory subject to other
liens, (e) variances between estimated and physical amounts of inventory, and
(f) the Senior Note Reserve; provided that, upon the Administrative Agent’s
receipt of a letter agreement or other writing from the DOE in form and
substance satisfactory to the Administrative Agent in its Permitted Discretion
granting the Administrative Agent rights to access and dispose of collateral on
the premises leased from the DOE by the Borrowers, the Administrative Agent
shall no longer require a reserve for estimated DOE Lease Turnover Obligations.”

“‘Collateral Availability’ means at any time the remainder of (a) the Borrowing
Base minus (b) the sum of (i) the unpaid principal balance of the Loans and all
accrued interest, fees and expenses plus (ii) the LC Exposure.”

3. No Default; Representations and Warranties, etc.

Each of the Borrowers represents and warrants to the Lenders and the
Administrative Agent that as of the date hereof (a) the representations and
warranties of the Credit Parties contained in Article III of the Credit
Agreement are true and correct in all material respects as of the date hereof as
if made on such date (except to extent that such representations and warranties
expressly relate to an earlier date, in which case they shall be true and
correct in all material respects as of such date); (b) the Borrowers are in
compliance in all material respects with all of the terms and provisions set
forth in the Credit Agreement and the other Financing Documents to be observed
or performed by them thereunder; (c) no Default or Event of Default shall have
occurred and be continuing; and (d) the execution, delivery and performance by
the Borrowers of this Amendment (i) have been duly authorized by all necessary
corporate and, if required, shareholder action on the part of the Borrowers,
(ii) will not violate any applicable law or regulation or the organizational
documents of any Borrower, (iii) will not violate or result in a default under
any material indenture, agreement or other instrument binding on any Borrower or
any of its assets and (iv) do not require any consent, waiver or approval of or
by any Person (other than the Administrative Agent and the Lenders) which has
not been obtained.

4. Conditions Precedent. The Amendment shall become effective on the date of
this Amendment (the “Second Amendment Effective Date”); provided that, on or
before the Second Amendment Effective Date, the Administrative Agent shall have
determined that each of the following conditions precedent shall have been
satisfied:

(a) Counterparts of Amendment. The Agent shall have received either (i) a
counterpart of this Amendment signed on behalf of the Borrowers and the Required
Lenders and counterparts of the Ratification of Guarantees attached hereto
signed on behalf of NAC Holdings Inc. and NAC International Inc., as guarantors,
or (ii) written evidence reasonably satisfactory to the Agent (which may include
telecopy transmission of a signed signature page of this Amendment or such
Ratification of Guarantees, as applicable) that such parties have signed a
counterpart of this Amendment and such Ratification of Guarantees, as
applicable.

(b) Consent Fee. As consideration for the amendments to the Credit Agreement set
forth herein, the Borrowers shall have paid to the Administrative Agent for the
account of each Lender that executes and delivers to the Administrative Agent a
duly executed counterpart to this Amendment prior to the Second Amendment
Effective Date, a consent fee equal in amount to ten one hundredths of one
percent (10 basis points) of the amount of such Lender’s Commitment as in effect
immediately prior to the Second Amendment Effective Date.

5. Miscellaneous.

(a) The Borrowers, the Lenders and the Administrative Agent hereby ratify and
confirm the terms and provisions of the Credit Agreement and the other Financing
Documents and agree that, except to the extent specifically amended hereby, the
Credit Agreement, the other Financing Documents and all related documents shall
remain in full force and effect. Nothing contained herein shall constitute a
waiver of any provision of the Financing Documents.

(b) The Borrowers agree to pay all reasonable expenses, including legal fees and
disbursements, incurred by the Administrative Agent in connection with this
Amendment and the transactions contemplated thereby.

(c) This Amendment may be executed in any number of counterparts (including by
way of facsimile transmission), each of which, when executed and delivered,
shall be an original, but all counterparts shall together constitute one
instrument.

(d) This Amendment shall be governed by the laws of the State of New York and
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns.

[Signature Pages Follow]

1 IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly
executed by their respective authorized officers as of the day and year first
above written.

BORROWERS:

USEC INC.

By: /s/ John C. Barpoulis

Name: John C. Barpoulis
Title: Sr. Vice President, Chief Financial Officer and Treasurer

UNITED STATES ENRICHMENT CORPORATION

By: /s/ John C. Barpoulis

Name: John C. Barpoulis
Title: Sr. Vice President, Chief Financial Officer and Treasurer

ADMINISTRATIVE AGENT:

JPMORGAN CHASE BANK, N.A., as Administrative and Collateral Agent

By: /s/ James M. Barbato

Name: James M. Barbato
Title: Vice President

LENDERS:

JPMORGAN CHASE BANK, N.A.

By: /s/ James M. Barbato

Name: James M. Barbato
Title: Vice President

MERRILL LYNCH CAPITAL, a division of MERRILL LYNCH BUSINESS FINANCIAL SERVICES
INC., as

Co-Syndication Agent and a Lender

By: /s/ Mary Beth O’Keefe

Name: Mary Beth O’Keefe
Title: Assistant Vice President

GMAC COMMERCIAL FINANCE LLC, as Co-Documentation Agent and a Lender

By: /s/ Thomas Maiale

Name: Thomas Maiale
Title: Director

WACHOVIA BANK, NATIONAL ASSOCIATION, as Co-Documentation Agent and a Lender

By: /s/ Jason Searle

Name: Jason Searle
Title: Vice President

SIEMENS FINANCIAL SERVICES, INC.

By: /s/ Mark Picillo

Name: Mark Picillo
Title: Vice President

SOVEREIGN BANK

By: /s/ Charles H. O’Donnell

Name: Charles H. O’Donnell
Title: Vice President

N.M. ROTHSCHILD & SONS LIMITED

By: /s/ N. A. Wood / Derek McCrone

Name: Nicholas Wood / Derek McCrone
Title: Director / Assistant Director

WELLS FARGO FOOTHILL, LLC

By: /s/ Mark Bradford

Name: Mark Bradford
Title: Vice President

WESTERNBANK PUERTO RICO

By: /s/ Miguel A. Vazquez

Name: Miguel A. Vazquez
Title: President, Business Credit Division

THE FOOTHILL GROUP, INC.

By: /s/ R. Michael Bohannon

Name: R. Michael Bohannon
Title: Senior Vice President

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RATIFICATION OF GUARANTEES

Each of the undersigned Guarantors hereby acknowledges and consents to the
foregoing Second Amendment to Amended and Restated Revolving Credit Agreement
dated as of October 16, 2006 (the “Second Amendment”) among USEC Inc.
(“Holdings”), United States Enrichment Corporation (“Enrichment” and, together
with Holdings, the “Borrowers”), the Lenders party thereto, JPMorgan Chase Bank,
N.A., as administrative agent and collateral agent (the “Administrative Agent”),
and the other financial institutions named therein as “agents”, confirms that
the obligations of the Borrowers under the Credit Agreement, as previously
amended by that certain First Amendment to Amended and Restated Revolving Credit
Agreement dated as of March 6, 2006, and as amended by the Second Amendment,
constitute “Guaranteed Obligations” guarantied by and entitled to the benefits
of each respective Amended and Restated Guarantee dated as of August 18, 2005
executed and delivered by each such Guarantor to the Administrative Agent, the
Issuing Bank, the Lenders and the other Secured Parties (each a “Guarantee” and
collectively, the “Guarantees”), agrees that its respective Guarantee remains in
full force and effect and ratifies and confirms all of its obligations
thereunder. Capitalized terms used but not otherwise defined herein shall have
the meanings attributed to them in the Guarantees.

GUARANTORS:

NAC HOLDING INC.

By: /s/ Kent S. Cole
Name: Kent S. Cole
Title: President

NAC INTERNATIONAL INC.

By: /s/ Kent S. Cole
Name: Kent S. Cole
Title: President

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