EXHIBIT 10.1

USEC Inc.

Common Stock

________

Underwriting Agreement

September 24, 2007

Goldman, Sachs & Co.,
Merrill, Lynch, Pierce, Fenner & Smith
Incorporated
As representatives of the several Underwriters
Named in Schedule I hereto,
c/o Goldman, Sachs & Co.,
85 Broad Street,
New York, New York 10004
Ladies and Gentlemen:

USEC Inc., a Delaware corporation (the “Company”), proposes, subject to the
terms and conditions stated herein, to issue and sell to the underwriters named
in Schedule I hereto (the “Underwriters”) an aggregate of 20,000,000 shares (the
“Firm Securities”) and, at the election of the Underwriters, up to 3,000,000
additional shares (the “Optional Securities”) of Common Stock (“Stock”) of the
Company (the Firm Securities and the Optional Securities that the Underwriters
elect to purchase pursuant to Section 2 hereof being collectively called the
“Securities”).

1. The Company represents and warrants to, and agrees with, each of the
Underwriters that:

(a) An “automatic shelf registration statement” as defined under Rule 405 under
the Securities Act of 1933, as amended (the “Act”) on Form S-3 (File
No. 333-146063) in respect of the Securities has been filed with the Securities
and Exchange Commission (the “Commission”) not earlier than three years prior to
the date hereof; such registration statement, and any post-effective amendment
thereto, became effective on filing; and no stop order suspending the
effectiveness of such registration statement or any part thereof has been issued
and no proceeding for that purpose has been initiated or threatened by the
Commission, and no notice of objection of the Commission to the use of such
registration statement or any post-effective amendment thereto pursuant to
Rule 401(g)(2) under the Act has been received by the Company (the base
prospectus filed as part of such registration statement, in the form in which it
has most recently been filed with the Commission on or prior to the date of this
Agreement, is hereinafter called the “Basic Prospectus”; any preliminary
prospectus (including any preliminary prospectus supplement) relating to the
Securities filed with the Commission pursuant to Rule 424(b) under the Act is
hereinafter called a “Preliminary Prospectus”; the various parts of such
registration statement, including all exhibits thereto but excluding Form T-1
and including any prospectus supplement relating to the Securities that is filed
with the Commission and deemed by virtue of Rule 430B to be part of such
registration statement, each as amended at the time such part of the
registration statement became effective, are hereinafter collectively called the
“Registration Statement”; the Basic Prospectus, as amended and supplemented by
any amendment or supplement related to the Securities immediately prior to the
Applicable Time (as defined in Section 1(c) hereof), is hereinafter called the
“Pricing Prospectus”; the form of the final prospectus relating to the
Securities filed with the Commission pursuant to Rule 424(b) under the Act in
accordance with Section 5(a) hereof is hereinafter called the “Prospectus”; any
reference herein to the Basic Prospectus, the Pricing Prospectus, any
Preliminary Prospectus or the Prospectus shall be deemed to refer to and include
the documents incorporated by reference therein pursuant to Item 12 of Form S-3
under the Act, as of the date of such prospectus; any reference to any amendment
or supplement to the Basic Prospectus, any Preliminary Prospectus or the
Prospectus shall be deemed to refer to and include any post-effective amendment
to the Registration Statement, any prospectus supplement relating to the
Securities filed with the Commission pursuant to Rule 424(b) under the Act and
any documents filed under the Securities Exchange Act of 1934, as amended (the
“Exchange Act”), and incorporated therein, in each case after the date of the
Basic Prospectus, such Preliminary Prospectus, or the Prospectus, as the case
may be; any reference to any amendment to the Registration Statement shall be
deemed to refer to and include any annual report of the Company filed pursuant
to Section 13(a) or 15(d) of the Exchange Act after the effective date of the
Registration Statement that is incorporated by reference in the Registration
Statement; and any “issuer free writing prospectus” as defined in Rule 433 under
the Act relating to the Securities is hereinafter called an “Issuer Free Writing
Prospectus”);

(b) No order preventing or suspending the use of any Preliminary Prospectus or
any Issuer Free Writing Prospectus has been issued by the Commission, and each
Preliminary Prospectus, at the time of filing thereof, conformed in all material
respects to the requirements of the Act and the rules and regulations of the
Commission thereunder, and did not contain an untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
to make the statements therein, in the light of the circumstances under which
they were made, not misleading; provided, however, that this representation and
warranty shall not apply to any statements or omissions made in reliance upon
and in conformity with information furnished in writing to the Company by an
Underwriter through Goldman, Sachs & Co. or Merrill Lynch, Pierce, Fenner &
Smith Incorporated (together, the “Representatives”) expressly for use therein;

(c) For the purposes of this Agreement, the “Applicable Time” is 6:15pm (New
York City time) on the date of this Agreement; the Pricing Prospectus as
supplemented by the Issuer Free Writing Prospectus set forth in Schedule II(b)
(the “Pricing Disclosure Package”), as of the Applicable Time, did not include
any untrue statement of a material fact or omit to state any material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading; and each Issuer Free
Writing Prospectus listed on Schedule II(a) and Schedule II(b) hereto does not
conflict with the information contained in the Registration Statement, the
Pricing Prospectus or the Prospectus and each such Issuer Free Writing
Prospectus, as supplemented by and taken together with the Pricing Disclosure
Package as of the Applicable Time, did not include any untrue statement of a
material fact or omit to state any material fact necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading; provided, however, that this representation and warranty
shall not apply to statements or omissions made in an Issuer Free Writing
Prospectus in reliance upon and in conformity with information furnished in
writing to the Company by an Underwriter through Goldman, Sachs & Co. expressly
for use therein;

(d) The documents incorporated by reference in the Pricing Prospectus and the
Prospectus, when they became effective or were filed with the Commission, as the
case may be, conformed in all material respects to the requirements of the Act
or the Exchange Act, as applicable, and the rules and regulations of the
Commission thereunder, and none of such documents contained an untrue statement
of a material fact or omitted to state a material fact required to be stated
therein or necessary to make the statements therein not misleading; any further
documents so filed and incorporated by reference in the Prospectus or any
further amendment or supplement thereto, when such documents become effective or
are filed with the Commission, as the case may be, will conform in all material
respects to the requirements of the Act or the Exchange Act, as applicable, and
the rules and regulations of the Commission thereunder and will not contain an
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein not misleading;
provided, however, that this representation and warranty shall not apply to any
statements or omissions made in reliance upon and in conformity with information
furnished in writing to the Company by an Underwriter through the
Representatives expressly for use therein; and no such documents were filed with
the Commission since the Commission’s close of business on the business day
immediately prior to the date of this Agreement and prior to the execution of
this Agreement, except as set forth on Schedule II(c) hereto;

(e) The Registration Statement conforms, and the Prospectus and any further
amendments or supplements to the Registration Statement and the Prospectus will
conform, in all material respects to the requirements of the Act and the rules
and regulations of the Commission thereunder and do not and will not, as of the
applicable effective date as to each part of the Registration Statement and as
of the applicable filing date as to the Prospectus and any amendment or
supplement thereto, contain an untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading; provided, however, that this representation
and warranty shall not apply to any statements or omissions made in reliance
upon and in conformity with information furnished in writing to the Company by
an Underwriter through the Representatives expressly for use therein;

(f) Neither the Company nor any of its subsidiaries has sustained since the date
of the latest audited financial statements incorporated by reference in the
Pricing Prospectus any material loss or interference with its business from
fire, explosion, flood or other calamity, whether or not covered by insurance,
or from any labor dispute or court or governmental action, order or decree,
otherwise than as set forth or contemplated in the Pricing Prospectus except as
would not, individually or in the aggregate, have a material adverse effect on
the management, properties, financial position, stockholders’ equity or results
of operations of the Company and its subsidiaries, taken as a whole (a “Material
Adverse Effect”); and, since the respective dates as of which information is
given in the Registration Statement and the Pricing Prospectus, there has not
been any change in the capital stock (except for de minimis issuances pursuant
to the Company’s Direct Stock Purchase Plan and 1999 Employee Stock Purchase
Plan and de minimis issuances of common stock upon the exercise of options
outstanding on the date hereof) or long term debt of the Company or any of its
subsidiaries or any material adverse change, or any development involving a
prospective material adverse change, in or affecting the general affairs,
management, financial position, stockholders’ equity or results of operations of
the Company and its subsidiaries, taken as a whole, otherwise than as set forth
or contemplated in the Pricing Prospectus;

(g) The Company and its subsidiaries have good and marketable title to all
personal property (other than intellectual property, which is covered by Section
1(v) hereof) owned by them, in each case that is material to the business of the
Company and its subsidiaries, taken as a whole, free and clear of all liens,
encumbrances and defects except those (1) pursuant to the Amended and Restated
Revolving Credit Agreement dated as of August 18, 2005 among the Company, United
States Enrichment Corporation and the lenders named therein, as further amended,
the (“Credit Agreement”) and the Amended and Restated Omnibus Pledge and
Security Agreement dated as of August 18, 2005 by the Company, United States
Enrichment Corporation, NAC Holding Inc. and NAC International Inc., in favor of
JPMorgan Chase Bank, N.A., as administrative and collateral agent for the
lenders (the “Security Agreement” and together with the Credit Agreement, the
“Credit Documents”), (2) such as are described in the Pricing Prospectus or
(3) such as do not materially affect the value of such property and do not
materially interfere with the use made and proposed to be made of such property
by the Company and its subsidiaries; and any real property and buildings held
under lease by the Company and its subsidiaries are held by them under valid,
subsisting and enforceable leases with such exceptions as are not material and
do not interfere with the use made and proposed to be made of such property and
buildings by the Company and its subsidiaries;

(h) The Company has been duly incorporated and is validly existing as a
corporation in good standing under the laws of the State of Delaware, with
corporate power and authority to own or to lease its properties and conduct its
business as described in the Pricing Prospectus, and has been duly qualified as
a foreign corporation for the transaction of business and is in good standing
under the laws of each other jurisdiction in which it owns or leases properties
or conducts any business so as to require such qualification, or is subject to
no material liability or disability by reason of the failure to be so qualified
in any such jurisdiction except where the failure to be so qualified would not,
individually or in the aggregate, have a Material Adverse Effect; and each of
the subsidiaries of the Company has been duly incorporated and is validly
existing as a corporation in good standing under the laws of its jurisdiction of
incorporation;

(i) The Company has an authorized capitalization as set forth in the Pricing
Prospectus and all of the issued shares of capital stock of the Company have
been duly and validly authorized and issued and are fully paid and
non-assessable and conform to the description of the Stock contained in the
Pricing Prospectus and the Prospectus; and all of the issued shares of capital
stock of each of the subsidiaries of the Company have been duly and validly
authorized and issued, are fully paid and non-assessable and (except for
directors’ qualifying shares and except as otherwise set forth in the Pricing
Prospectus) are owned directly or indirectly by the Company, free and clear of
all liens, encumbrances, equities or claims except as would not have a Material
Adverse Effect;

(j) The unissued Securities to be issued and sold by the Company to the
Underwriters hereunder have been duly and validly authorized and, when issued
and delivered against payment therefor as provided herein, will be duly and
validly issued and fully paid and non-assessable and will conform to the
description of the Securities contained in the Prospectus;

(k) The issue and sale of the Securities and the compliance by the Company with
this Agreement and the consummation of the transactions herein contemplated will
not: (1) conflict with or result in a breach or violation of any of the terms or
provisions of, or constitute a default under, any indenture, mortgage, deed of
trust, loan agreement or other agreement or instrument to which the Company or
any of its subsidiaries is a party or by which the Company or any of its
subsidiaries is bound or to which any of the property or assets of the Company
or any of its subsidiaries is subject, (2) result in any violation of the
provisions of the Certificate of Incorporation or By-laws of the Company or
(3) result in any violation of any statute or any order, rule or regulation of
any court or governmental agency or body having jurisdiction over the Company or
any of its subsidiaries or any of their properties; except in the case of clause
(1) and (3) for any violation that would not, individually or in the aggregate,
have a Material Adverse Effect and would not materially and adversely affect the
consummation of the transactions contemplated herein; and no consent, approval,
authorization, order, registration or qualification of or with any such court or
governmental agency or body is required for the issue and sale of the Securities
or the consummation by the Company of the transactions contemplated by this
Agreement except such as have been obtained under the Act and such consents,
approvals, authorizations, registrations or qualifications as would not have a
Material Adverse Effect or as may be required under state securities or Blue Sky
laws in connection with the purchase and distribution of the Securities by the
Underwriters;

(l) Neither the Company nor any of its subsidiaries is (1) in violation of its
Certificate of Incorporation or By-laws or (2) in default in the performance or
observance of any material obligation, covenant or condition contained in any
indenture, mortgage, deed of trust, loan agreement, lease or other agreement or
instrument to which it is a party or by which it or any of its properties may be
bound;

(m) The statements set forth in the Pricing Prospectus and Prospectus under the
caption “Description of Capital Stock”, insofar as they purport to constitute a
summary of the terms of the Stock, under the captions “Certain Material United
States Federal Income Tax Consequences to Non-U.S. Holders” and “Underwriting”,
insofar as they purport to describe the provisions of the laws and documents
referred to therein, are accurate, complete and fair in all material respects;

(n) Other than as set forth in the Pricing Prospectus, there are no legal or
governmental proceedings pending to which the Company or any of its subsidiaries
is a party or of which any property of the Company or any of its subsidiaries is
the subject which, if determined adversely to the Company or any of its
subsidiaries, would, individually or in the aggregate, have a Material Adverse
Effect; and, other than as set forth in the Pricing Prospectus, to the Company’s
knowledge, no such proceedings are threatened or contemplated by governmental
authorities or threatened by others;

(o) The Company is not and, after giving effect to the offering and sale of the
Securities and the application of the proceeds thereof, will not be an
“investment company”, as such term is defined in the Investment Company Act of
1940, as amended (the “Investment Company Act”);

(p) (A) (i) At the time of filing the Registration Statement, (ii) at the time
of the most recent amendment thereto, if any, for the purposes of complying with
Section 10(a)(3) of the Act (whether such amendment was by post-effective
amendment, incorporated report filed pursuant to Section 13 or 15(d) of the
Exchange Act or form of prospectus), and (iii) at the time the Company or any
person acting on its behalf (within the meaning, for this clause only, of Rule
163(c) under the Act) made any offer relating to the Securities in reliance on
the exemption of Rule 163 under the Act, the Company was a “well-known seasoned
issuer” as defined in Rule 405 under the Act; and (B) at the earliest time after
the filing of the Registration Statement that the Company or another offering
participant made a bona fide offer (within the meaning of Rule 164(h)(2) under
the Act) of the Securities, the Company was not an “ineligible issuer” as
defined in Rule 405 under the Act;

(q) PricewaterhouseCoopers LLP, who have audited certain financial statements of
the Company and its subsidiaries, and have audited the Company’s internal
control over financial reporting and management’s assessment thereof are
independent registered public accountants as required by the Act and the rules
and regulations of the Commission thereunder;

(r) The Company maintains a system of internal control over financial reporting
(as such term is defined in Rule 13a-15(f) under the Exchange Act) that complies
with the requirements of the Exchange Act and has been designed by the Company’s
principal executive officer and principal financial officer, or under their
supervision, to provide reasonable assurance regarding the reliability of
financial reporting and the preparation of financial statements for external
purposes in accordance with generally accepted accounting principles. As of the
date of the latest audited financial statements included in the Pricing
Prospectus, the Company’s internal control over financial reporting is effective
and the Company is not aware of any material weaknesses in its internal control
over financial reporting;

(s) Since the date of the latest audited financial statements incorporated by
reference in the Pricing Prospectus, there has been no change in the Company’s
internal control over financial reporting that has materially affected, or is
reasonably likely to materially affect, the Company’s internal control over
financial reporting;

(t) The Company maintains disclosure controls and procedures (as such term is
defined in Rule 13a-15(e) under the Exchange Act) that comply with the
requirements of the Exchange Act; such disclosure controls and procedures have
been designed to ensure that material information relating to the Company and
its subsidiaries is made known to the Company’s principal executive officer and
principal financial officer by others within those entities; and such disclosure
controls and procedures are effective;

(u) The Company and its subsidiaries have all necessary consents,
authorizations, approvals, clearances, orders, certificates and permits of and
from, and have made all required declarations and filings with, all federal,
state, local and other governmental authorities (including, without limitation,
the Nuclear Regulatory Commission (“NRC”), the Department of Energy (“DOE”) and
the Occupational Safety and Health Administration (“OSHA”), all self-regulatory
organizations and all courts and other tribunals, to own, lease, license and use
their respective properties and assets, as applicable, and to conduct their
respective businesses in the manner described in the Pricing Prospectus; except
such consents, authorizations, approvals, clearances, orders, certificates,
permits, declarations and filings the failure of which to have would not,
individually or in the aggregate, have a Material Adverse Effect;

(v) The Company or its subsidiaries own, or have the right to use, or can
acquire on reasonable terms, all material patents, patent rights, intellectual
property licenses, inventions, copyrights, know-how (including trade secrets and
other unpatented and/or unpatentable proprietary or confidential information,
systems or procedures), trademarks, service marks and trade names currently
employed by the Company and its subsidiaries in connection with the business now
operated by the Company and its subsidiaries except as would not, individually
or in the aggregate, have a Material Adverse Effect and neither the Company nor
any of its subsidiaries has received any notice of infringement of or conflict
with asserted rights of others with respect to any of the foregoing that if
resolved against the Company or its subsidiaries, would, individually or in the
aggregate, have a Material Adverse Effect;

(w) Except as set forth in the Pricing Prospectus, the Company and its
subsidiaries (1) are and have been in compliance with all applicable federal,
state and local laws, including common law, and regulations, relating to the
protection of human health and safety, the environment or hazardous or toxic
substances or wastes, pollutants or contaminants (“Environmental Laws”),
(2) have received all permits, licenses or other approvals required of them
under applicable Environmental Laws to conduct their respective businesses and
(3) are in compliance with all terms and conditions of any such permit, license
or approval, except in the case of each of clauses (1), (2) and (3), to the
extent that the failure to so comply or receive, as applicable, would not,
individually or in the aggregate, have a Material Adverse Effect;

(x) Except as set forth in the Pricing Prospectus, there are no costs or
liabilities associated with Environmental Laws (including, without limitation,
any capital or operating expenditures required for clean-up, closure of
properties or compliance with Environmental Laws or any permit, license or
approval, any related constraints on operating activities and any potential
liabilities to third parties) that would, after taking into account existing
indemnities from the DOE and after giving effect to the Privatization Act,
Chapter 1, Title 3 of Public Law 104-134, and the Energy Policy Act of 1992,
Public Law 102-486, individually or in the aggregate, have a Material Adverse
Effect;

(y) Other than as disclosed in the Pricing Prospectus, no labor dispute with the
employees of the Company or any of its subsidiaries exists, or, to the knowledge
of the Company, is imminent, which would, individually or in the aggregate, have
a Material Adverse Effect; and

(z) Except as would not, individually or in the aggregate have a Material
Adverse Effect, (1) the Company and its subsidiaries comply with the Employee
Retirement Income Security Act of 1974, as amended (“ERISA”), the Internal
Revenue Code of 1986, as amended (the “Code”) and the terms of each plan, if and
to the extent applicable, with respect to each “pension plan” (as defined in
Section 3(2) of ERISA) maintained by the Company or any of its subsidiaries and
(2) none of the Company or its subsidiaries has incurred, or expects to incur,
any liability (other than contributions made in accordance with the terms of
applicable plans) under Title IV of ERISA with respect to any ongoing, frozen or
terminated “pension plan” that is subject to Title IV of ERISA and is, or was,
maintained by the Company, its subsidiaries or any other person or entity that,
together with the Company and its subsidiaries, is treated as a single employer
under Section 414 of the Code.

2. Subject to the terms and conditions herein set forth, (a) the Company agrees
to issue and sell to each of the Underwriters, and each of the Underwriters
agrees, severally and not jointly, to purchase from the Company, at a purchase
price per share of $9.32, the number of Firm Securities set forth opposite the
name of such Underwriter in Schedule I hereto, and (b) in the event and to the
extent that the Underwriters shall exercise the election to purchase Optional
Securities as provided below, the Company agrees to issue and sell to each of
the Underwriters, and each of the Underwriters agrees, severally and not
jointly, to purchase from the Company, at the purchase price per share set forth
in clause (a) of this Section 2, that portion of the number of Optional
Securities as to which such election shall have been exercised (to be adjusted
by you so as to eliminate fractional shares) determined by multiplying such
number of Optional Securities by a fraction, the numerator of which is the
maximum number of Optional Securities which such Underwriter is entitled to
purchase as set forth opposite the name of such Underwriter in Schedule I hereto
and the denominator of which is the maximum number of Optional Securities that
all of the Underwriters are entitled to purchase hereunder.

The Company hereby grants to the Underwriters the right to purchase at their
election up to 3 million Optional Securities, at the purchase price per share
set forth in the paragraph above, for the sole purpose of covering sales of
shares in excess of the number of Firm Securities, provided that the purchase
price per Optional Share shall be reduced by an amount per share equal to any
dividends or distributions declared by the Company and payable on the Firm
Securities but not payable on the Optional Securities. Any such election to
purchase Optional Securities may be exercised only by written notice from you to
the Company, given within a period of 30 calendar days after the date of this
Agreement, setting forth the aggregate number of Optional Securities to be
purchased and the date on which such Optional Securities are to be delivered, as
determined by you but in no event earlier than the First Time of Delivery (as
defined in Section 4 hereof) or, unless you and the Company otherwise agree in
writing, earlier than two or later than ten business days after the date of such
notice.

3. Upon the authorization by you of the release of the Firm Securities, the
several Underwriters propose to offer the Firm Securities for sale upon the
terms and conditions set forth in the Prospectus.

4. (a) The Securities to be purchased by each Underwriter hereunder, in
definitive form, and in such authorized denominations and registered in such
names as Goldman, Sachs & Co. may request upon at least forty-eight hours’ prior
notice to the Company shall be delivered by or on behalf of the Company to
Goldman, Sachs & Co., through the facilities of the Depository Trust Company
(“DTC”), for the account of such Underwriter, against payment by or on behalf of
such Underwriter of the purchase price therefor by wire transfer of Federal
(same-day) funds to the account specified by the Company to Goldman, Sachs & Co.
at least forty-eight hours in advance. The Company will cause the certificates
representing the Securities to be made available for checking and packaging at
least twenty-four hours prior to the Time of Delivery (as defined below) with
respect thereto at the office of DTC or its designated custodian (the
“Designated Office”). The time and date of such delivery and payment shall be,
with respect to the Firm Shares, 9:30 a.m., New York City time, on September 28,
2007 or such other time and date as Goldman, Sachs & Co. and the Company may
agree upon in writing, and, with respect to the Optional Shares, 9:30 a.m., New
York City time, on the date specified by Goldman, Sachs & Co. in the written
notice given by Goldman, Sachs & Co. of the Underwriters’ election to purchase
such Optional Shares, or such other time and date as Goldman, Sachs & Co. and
the Company may agree upon in writing. Such time and date for delivery of the
Firm Shares is herein called the “First Time of Delivery”, such time and date
for delivery of the Optional Shares, if not the First Time of Delivery, is
herein called the “Second Time of Delivery”, and each such time and date for
delivery is herein called a “Time of Delivery”.

(b) The documents to be delivered at each Time of Delivery by or on behalf of
the parties hereto pursuant to Section 8 hereof, including the cross-receipt for
the Securities and any additional documents requested by the Underwriters
pursuant to Section 8(k) hereof, will be delivered at the offices of Sullivan &
Cromwell LLP, 1701 Pennsylvania Ave. N.W., Washington, D.C. 20006 (the “Closing
Location”), and the Securities will be delivered at the Designated Office, all
at the Time of Delivery. A meeting will be held at the Closing Location at 5:00
p.m., New York City time, on the New York Business Day next preceding such Time
of Delivery, at which meeting the final drafts of the documents to be delivered
pursuant to the preceding sentence will be available for review by the parties
hereto. For the purposes of this Section 4, “New York Business Day” shall mean
each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which
banking institutions in New York City are generally authorized or obligated by
law or executive order to close.

5. The Company agrees with each of the Underwriters:

(a) To prepare the Prospectus in a form approved by you and to file such
Prospectus pursuant to Rule 424(b) under the Act not later than the Commission’s
close of business on the second business day following the date of this
Agreement; to make no further amendment or any supplement to the Registration
Statement, the Basic Prospectus or the Prospectus prior to such Time of Delivery
which shall be disapproved by you promptly after reasonable notice thereof; to
advise you, promptly after it receives notice thereof, of the time when any
amendment to the Registration Statement has been filed or becomes effective or
any amendment or supplement to the Prospectus has been filed and to furnish you
with copies thereof; to file promptly all other material required to be filed by
the Company with the Commission pursuant to Rule 433(d) under the Act; to file
promptly all reports and any definitive proxy or information statements required
to be filed by the Company with the Commission pursuant to Section 13(a), 13(c),
14 or 15(d) of the Exchange Act subsequent to the date of the Prospectus and for
so long as the delivery of a prospectus (or in lieu thereof, the notice referred
to in Rule 173(a) under the Act) is required in connection with the offering or
sale of the Securities; to advise you, promptly after it receives notice
thereof, of the issuance by the Commission of any stop order or of any order
preventing or suspending the use of any Preliminary Prospectus or other
prospectus in respect of the Securities, of any notice of objection of the
Commission to the use of the Registration Statement or any post-effective
amendment thereto pursuant to Rule 401(g)(2) under the Act, of the suspension of
the qualification of the Securities for offering or sale in any jurisdiction, of
the initiation or threatening of any proceeding for any such purpose, or of any
request by the Commission for the amending or supplementing of the Registration
Statement or the Prospectus or for additional information; and, in the event of
the issuance of any stop order or of any order preventing or suspending the use
of any Preliminary Prospectus or other prospectus or suspending any such
qualification, to promptly use its best efforts to obtain the withdrawal of such
order; and in the event of any such issuance of a notice of objection, promptly
to take such steps including, without limitation, amending the Registration
Statement or filing a new registration statement, at its own expense, as may be
necessary to permit offers and sales of the Securities by the Underwriters
(references herein to the Registration Statement shall include any such
amendment or new registration statement);

(b) If required by Rule 430B(h) under the Act, to prepare a form of prospectus
in a form approved by you, and to file such form of prospectus pursuant to Rule
424(b) under the Act not later than may be required by Rule 424(b) under the
Act; and to make no further amendment or supplement to such form of prospectus
which shall be disapproved by you promptly after reasonable notice therereof;

(c) If by the third anniversary (the “Renewal Deadline”) of the initial
effective date of the Registration Statement, any of the Securities remain
unsold by the Underwriters, the Company will file, if it has not already done so
and is eligible to do so, a new automatic shelf registration statement relating
to the Securities, in a form reasonably satisfactory to you. If at the Renewal
Deadline the Company is no longer eligible to file an automatic shelf
registration statement, the Company will, if it has not already done so, file a
new shelf registration statement relating to the Securities, in a form
satisfactory to you and will use its best efforts to cause such registration
statement to be declared effective within 180 days after the Renewal Deadline.
The Company will take all other action necessary or appropriate to permit the
public offering and sale of the Securities to continue as contemplated in the
expired registration statement relating to the Securities. References herein to
the Registration Statement shall include such new automatic shelf registration
statement or such new shelf registration statement, as the case may be;

(d) Promptly from time to time to take such action as you may reasonably request
to qualify the Securities for offering and sale under the securities laws of
such jurisdictions as you may request and to comply with such laws so as to
permit the continuance of sales and dealings therein in such jurisdictions for
as long as may be necessary to complete the distribution of the Securities,
provided that in connection therewith the Company shall not be required to
qualify as a foreign corporation or to file a general consent to service of
process in any jurisdiction;

(e) Prior to 10:00 a.m., New York City time, on the New York Business Day next
succeeding the date of this Agreement and from time to time, to furnish the
Underwriters with written and electronic copies of the Prospectus in New York
City in such quantities as you may reasonably request, and, if the delivery of a
prospectus (or in lieu thereof, the notice referred to in Rule 173(a) under the
Act) is required at any time prior to the expiration of nine months after the
time of issue of the Prospectus in connection with the offering or sale of the
Securities and if at such time any event shall have occurred as a result of
which the Prospectus as then amended or supplemented would include an untrue
statement of a material fact or omit to state any material fact necessary in
order to make the statements therein, in the light of the circumstances under
which they were made when such Prospectus (or in lieu thereof, the notice
referred to in Rule 173(a) under the Act) is delivered, not misleading, or, if
for any other reason it shall be necessary during such same period to amend or
supplement the Prospectus or to file under the Exchange Act any document
incorporated by reference in the Prospectus in order to comply with the Act or
the Exchange Act, to notify you and upon your request to file such document and
to prepare and furnish without charge to each Underwriter and to any dealer in
securities as many written and electronic copies as you may from time to time
reasonably request of an amended Prospectus or a supplement to the Prospectus
which will correct such statement or omission or effect such compliance; and in
case any Underwriter is required to deliver a prospectus (or in lieu thereof,
the notice referred to in Rule 173(a) under the Act) in connection with sales of
any of the Securities at any time nine months or more after the time of issue of
the Prospectus, upon your request but at the expense of such Underwriter, to
prepare and deliver to such Underwriter as many written and electronic copies as
you may request of an amended or supplemented Prospectus complying with
Section 10(a)(3) of the Act;

(f) To make generally available to its securityholders as soon as practicable,
but in any event not later than sixteen months after the effective date of the
Registration Statement (as defined in Rule 158(c) under the Act), an earnings
statement of the Company and its subsidiaries (which need not be audited)
complying with Section 11(a) of the Act and the rules and regulations of the
Commission thereunder (including, at the option of the Company, Rule 158);

(g) During the period beginning from the date hereof and continuing to and
including the date 90 days after the date of the Prospectus (the “Lock-Up
Period”), not to offer, sell, contract to sell, pledge, grant any option to
purchase, make any short sale or otherwise dispose, except as provided
hereunder, of any securities of the Company that are substantially similar to
the Securities, including but not limited to any options or warrants to purchase
shares of Stock or any securities that are convertible into or exchangeable for,
or that represent the right to receive, Stock or any such substantially similar
securities (other than (1) the offer and sale of Securities pursuant to this
Agreement, (2) the offer and sale of 3.0% senior convertible notes by the
Company pursuant to the Underwriting Agreement, dated the date hereof, between
the Company, Goldman, Sachs & Co., and Wachovia Capital Markets, LLC, as
representatives of the several Underwriters named therein relating to the common
stock of the Company, which shall occur concurrently with this offer and sale of
Securities, which shall occur concurrently with this offer and sale of
Securities, (3) the grant of stock options, restricted stocks, restricted stock
units or other equity awards pursuant to the USEC Inc. 1999 Equity Incentive
Plan, as amended, (4) issuances pursuant to the Dividend Reinvestment Direct
Stock Purchase Plan, USEC Inc. 1999 Employee Stock Purchase Plan, as amended,
(5) the issuance of Stock pursuant to the exercise of such options or settlement
of such equity awards or (6) upon the conversion or exchange of convertible or
exchangeable securities outstanding as of the date of this Agreement), without
your prior written consent; provided, however, that (1) if during the last
17 days of the initial Lock-Up Period, the Company releases earnings results or
announces material news or a material event or (2) prior to the expiration of
the initial Lock-Up Period, the Company announces that it will release earnings
results during the 15-day period following the last day of the initial Lock-Up
Period, then in each case the Lock-Up Period will be automatically extended
until the expiration of the 18-day period beginning on the date of release of
the earnings results or the announcement of the material news or material event,
as applicable, unless each of the Representatives waives, in writing, such
extension; provided, further, the Company will provide each of the
Representatives and each stockholder subject to the Lock-Up Period pursuant to
the letters described in Section 8(j) with prior notice of any such announcement
that gives rise to an extension of the Lock-up Period;

(h) To pay the required Commission filing fees relating to the Securities within
the time required by Rule 456(b)(1) under the Act without regard to the proviso
therein and otherwise in accordance with Rules 456(b) and 457(r) under the Act;

(i) To use the net proceeds received by it from the sale of the Securities
pursuant to this Agreement in the manner specified in the Pricing Prospectus
under the caption “Use of Proceeds”; and

(j) To use its commercially reasonable efforts to list, subject to notice of
issuance, the Securities on the New York Stock Exchange (the “Exchange).

6.

(a) (i) The Company represents and agrees that without the prior consent of
Goldman, Sachs & Co., it has not made and will not make any offer relating to
the Securities that would constitute a “free writing prospectus” as defined in
Rule 405 under the Act;

(ii) Each Underwriter represents and agrees that, without the prior consent of
each of the Company and the Representatives, it has not made and will not make
any offer relating to the Securities that would constitute a free writing
prospectus; and

(iii) The Company and the Underwriters agree that any such free writing
prospectus described in clauses (i) and (ii) of this Section 6(a), the use of
which has been consented to by the Company and Goldman, Sachs & Co., is listed
on Schedule II(a) and Schedule II(b) hereto;

(b) The Company has complied and will comply with the requirements of Rule 433
under the Act applicable to any Issuer Free Writing Prospectus, including timely
filing with the Commission or retention where required and legending; and

(c) The Company agrees that if at any time following issuance of an Issuer Free
Writing Prospectus any event occurred or occurs as a result of which such Issuer
Free Writing Prospectus would conflict with the information in the Registration
Statement, the Pricing Prospectus or the Prospectus or would include an untrue
statement of a material fact or omit to state any material fact necessary in
order to make the statements therein, in the light of the circumstances then
prevailing, not misleading, the Company will give prompt notice thereof to
Goldman, Sachs & Co. and, if requested by Goldman, Sachs & Co., will prepare and
furnish without charge to each Underwriter an Issuer Free Writing Prospectus or
other document that will correct such conflict, statement or omission; provided,
however, that this representation and warranty shall not apply to any statements
or omissions in an Issuer Free Writing Prospectus made in reliance upon and in
conformity with information furnished in writing to the Company by an
Underwriter through Goldman, Sachs & Co. expressly for use therein.

7. The Company covenants and agrees with the several Underwriters that the
Company will pay or cause to be paid the following: (i) the fees, disbursements
and expenses of the Company’s counsel and accountants in connection with the
registration of the Securities under the Act and all other expenses in
connection with the preparation, printing, reproduction and filing of the
Registration Statement, the Basic Prospectus, any Preliminary Prospectus, any
Issuer Free Writing Prospectus and the Prospectus and amendments and supplements
thereto and the mailing and delivering of copies thereof to the Underwriters and
dealers; (ii) the cost of printing or producing any Agreement among
Underwriters, this Agreement, the Blue Sky Memorandum, closing documents
(including any compilations thereof) and any other documents in connection with
the offering, purchase, sale and delivery of the Securities; (iii) all expenses
in connection with the qualification of the Securities for offering and sale
under state securities laws as provided in Section 5(d) hereof, including the
fees and disbursements of counsel for the Underwriters in connection with such
qualification and in connection with the Blue Sky survey; (iv) all fees and
expenses in connection with listing the Securities on the Exchange; (v) the cost
of preparing the Securities; (vi) the cost and charges of any transfer agent or
registrar; and (vii) all other costs and expenses incident to the performance of
its obligations hereunder which are not otherwise specifically provided for in
this Section. It is understood, however, that, except as provided in this
Section, and Sections 9 and 12 hereof, the Underwriters will pay all of their
own costs and expenses, including the fees of their counsel, transfer taxes on
resale of any of the Securities by them, and any advertising expenses connected
with any offers they may make.

8. The obligations of the Underwriters hereunder, as to the Securities to be
delivered at each Time of Delivery, shall be subject, in their discretion, to
the condition that all representations and warranties and other statements of
the Company herein are, at and as of such Time of Delivery, true and correct,
the condition that the Company shall have performed all of its obligations
hereunder theretofore to be performed, and the following additional conditions:

(a) The Prospectus shall have been filed with the Commission pursuant to Rule
424(b) under the Act within the applicable time period prescribed for such
filing by the rules and regulations under the Act and in accordance with Section
5(a) hereof; all material required to be filed by the Company pursuant to Rule
433(d) under the Act shall have been filed with the Commission within the
applicable time period prescribed for such filings by Rule 433; no stop order
suspending the effectiveness of the Registration Statement or any part thereof
shall have been issued and no proceeding for that purpose shall have been
initiated or threatened by the Commission and no notice of objection of the
Commission to the use of the Registration Statement or any post-effective
amendment thereto pursuant to Rule 401(g)(2) under the Act shall have been
received; no stop order suspending or preventing the use of the Prospectus or
any Issuer Free Writing Prospectus shall have been initiated or threatened by
the Commission; and all requests for additional information on the part of the
Commission shall have been complied with to your reasonable satisfaction;

(b) Sullivan & Cromwell LLP, counsel for the Underwriters, shall have furnished
to you such written opinion or opinions, dated such Time of Delivery, in form
and substance reasonably satisfactory to you, with respect to such matters as
you may reasonably request, and such counsel shall have received such papers and
information as they may reasonably request to enable them to pass upon such
matters;

(c) Latham & Watkins LLP, counsel for the Company, shall have furnished to you
their written opinions in form and substance substantially in the forms attached
as Annexes II(a) and (b) hereto, dated such Time of Delivery;

(d) Allen Lear, Interim General Counsel of the Company, shall have furnished to
you his written opinion in form and substance substantially in the form attached
as Annex II(c) hereto, dated such Time of Delivery;

(e) Morgan, Lewis & Bockius LLP, regulatory counsel for the Company, shall have
furnished to you their written opinion in form and substance substantially in
the form attached as Annex II(d) hereto, dated such Time of Delivery;

(f) On the date of the Prospectus at a time prior to the execution of this
Agreement, at 9:30 a.m. (New York City time) on the effective date of any post
effective amendment to the Registration Statement filed subsequent to the date
of this Agreement and also at each Time of Delivery, PricewaterhouseCoopers LLP
shall have furnished to you a letter or letters, dated the respective dates of
delivery thereof, in form and substance reasonably satisfactory to you and which
PricewaterhouseCoopers LLP is willing to perform and report upon, to the effect
set forth in Annex I hereto;

(g) (i) Neither the Company nor any of its subsidiaries shall have sustained
since the date of the latest audited financial statements incorporated by
reference in the Pricing Prospectus any loss or interference with its business
from fire, explosion, flood or other calamity, whether or not covered by
insurance, or from any labor dispute or court or governmental action, order or
decree, otherwise than as set forth or contemplated in the Pricing Prospectus,
and (ii) since the respective dates as of which information is given in the
Pricing Prospectus there shall not have been any change in the capital stock
(except for de minimis issuances pursuant to the Company’s Direct Stock Purchase
Plan and 1999 Employee Stock Purchase Plan and de minimis issuances of common
stock upon the exercise of options outstanding on the date hereof) or long term
debt of the Company or any of its subsidiaries or any change, or any development
involving a prospective change, in or affecting the general affairs, management,
financial position, stockholders’ equity or results of operations of the Company
and its subsidiaries, taken as a whole, otherwise than as set forth or
contemplated in the Pricing Prospectus, the effect of which, in any such case
described in clause (i) or (ii), is in your opinion so material and adverse as
to make it impracticable or inadvisable to proceed with the public offering or
the delivery of the Securities being delivered at such Time of Delivery on the
terms and in the manner contemplated in the Prospectus;

(h) On or after the Applicable Time (i) no downgrading shall have occurred in
the rating accorded the Company’s debt securities by any “nationally recognized
statistical rating organization”, as that term is defined by the Commission for
purposes of Rule 436(g)(2) under the Act, and (ii) no such organization shall
have publicly announced that it has under surveillance or review, with possible
negative implications, its rating of any of the Company’s debt securities;

(i) On or after the Applicable Time there shall not have occurred any of the
following: (i) a suspension or material limitation in trading in securities
generally on the Exchange; (ii) a suspension or material limitation in trading
in the Company’s securities on the Exchange; (iii) a general moratorium on
commercial banking activities declared by either Federal or New York State
authorities or a material disruption in commercial banking or securities
settlement or clearance services in the United States; (iv) the outbreak or
escalation of hostilities involving the United States or the declaration by the
United States of a national emergency or war or (v) the occurrence of any other
calamity or crisis or any change in financial, political or economic conditions
in the United States or elsewhere, if the effect of any such event specified in
clause (iv) or (v) in the judgment of the Representatives makes it impracticable
or inadvisable to proceed with the public offering or the delivery of the
Securities being delivered at such Time of Delivery on the terms and in the
manner contemplated in the Prospectus;

(j) The Company shall have complied with the provisions of Section 5(e) hereof
with respect to the furnishing of prospectuses on the New York Business Day next
succeeding the date of this Agreement;

(k) Any actions required for the Securities to be duly listed for quotation on
the Exchange shall have been taken;

(l) The Company has obtained and delivered to the Underwriters executed copies
of an agreement from each of the stockholders listed on Annex III hereto,
substantially to the effect set forth in Section 5(g) hereof in form and
substance satisfactory to you;

(m) The Company shall have furnished or caused to be furnished to you at such
Time of Delivery certificates of officers of the Company reasonably satisfactory
to the Representatives as to the accuracy of the representations and warranties
of the Company herein at and as of such time, as to the performance by the
Company of all of its obligations hereunder to be performed at or prior to such
time, as to the matters set forth in subsections (a) and (e) of this Section and
as to such other matters as the Representatives may reasonably request; and

(m) The sale of the 3.0% convertible senior notes by the Company pursuant to the
underwriting agreement, dated the date hereof, between the Company and Goldman,
Sachs & Co. and Wachovia Capital Markets, LLC, as representatives of the
underwriters named therein, shall have occurred prior to or concurrently with
the sale of the Securities hereunder.

9. (a) The Company will indemnify and hold harmless each Underwriter against any
losses, claims, damages or liabilities, joint or several, to which such
Underwriter may become subject, under the Act or otherwise, insofar as such
losses, claims, damages or liabilities (or actions in respect thereof) arise out
of or are based upon an untrue statement or alleged untrue statement of a
material fact contained in the Registration Statement, the Basic Prospectus, any
Preliminary Prospectus, the Pricing Prospectus or the Prospectus, or any
amendment or supplement thereto, any Issuer Free Writing Prospectus or any
“issuer information” filed or required to be filed pursuant to Rule 433(d) under
the Act, or arise out of or are based upon the omission or alleged omission to
state therein a material fact required to be stated therein or necessary to make
the statements therein not misleading, and will reimburse each Underwriter for
any legal or other expenses reasonably incurred by such Underwriter in
connection with investigating or defending any such action or claim as such
expenses are incurred; provided, however, that the Company shall not be liable
in any such case to the extent that any such loss, claim, damage or liability
arises out of or is based upon an untrue statement or alleged untrue statement
or omission or alleged omission made in the Registration Statement, the Basic
Prospectus, any Preliminary Prospectus, the Pricing Prospectus or the
Prospectus, or any amendment or supplement thereto, or any Issuer Free Writing
Prospectus, in reliance upon and in conformity with written information
furnished to the Company by any Underwriter through the Representatives
expressly for use therein.

(b) Each Underwriter will indemnify and hold harmless the Company against any
losses, claims, damages or liabilities to which the Company may become subject,
under the Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon an
untrue statement or alleged untrue statement of a material fact contained in the
Registration Statement, the Basic Prospectus, any Preliminary Prospectus, the
Pricing Prospectus or the Prospectus, or any amendment or supplement thereto, or
any Issuer Free Writing Prospectus, or arise out of or are based upon the
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, in
each case to the extent, but only to the extent, that such untrue statement or
alleged untrue statement or omission or alleged omission was made in the
Registration Statement, the Basic Prospectus, any Preliminary Prospectus, the
Pricing Prospectus or the Prospectus or any such amendment or supplement
thereto, or any Issuer Free Writing Prospectus, in reliance upon and in
conformity with written information furnished to the Company by such Underwriter
through the Representatives expressly for use therein; and will reimburse the
Company for any legal or other expenses reasonably incurred by the Company in
connection with investigating or defending any such action or claim as such
expenses are incurred.

(c) Promptly after receipt by an indemnified party under subsection (a) or
(b) above of notice of the commencement of any action, such indemnified party
shall, if a claim in respect thereof is to be made against the indemnifying
party under such subsection, notify the indemnifying party in writing of the
commencement thereof; but the omission so to notify the indemnifying party shall
not relieve it from any liability which it may have to any indemnified party
otherwise than under such subsection. In case any such action shall be brought
against any indemnified party and it shall notify the indemnifying party of the
commencement thereof, the indemnifying party shall be entitled to participate
therein and, to the extent that it shall wish, jointly with any other
indemnifying party similarly notified, to assume the defense thereof, with
counsel satisfactory to such indemnified party (who shall not, except with the
consent of the indemnified party, be counsel to the indemnifying party), and,
after notice from the indemnifying party to such indemnified party of its
election so to assume the defense thereof, the indemnifying party shall not be
liable to such indemnified party under such subsection for any legal expenses of
other counsel or any other expenses, in each case subsequently incurred by such
indemnified party, in connection with the defense thereof other than reasonable
costs of investigation. No indemnifying party shall, without the written consent
of the indemnified party, effect the settlement or compromise of, or consent to
the entry of any judgment with respect to, any pending or threatened action or
claim in respect of which indemnification or contribution may be sought
hereunder (whether or not the indemnified party is an actual or potential party
to such action or claim) unless such settlement, compromise or judgment
(i) includes an unconditional release of the indemnified party from all
liability arising out of such action or claim and (ii) does not include a
statement as to or an admission of fault, culpability or a failure to act, by or
on behalf of any indemnified party.

(d) If the indemnification provided for in this Section 9 is unavailable to or
insufficient to hold harmless an indemnified party under subsection (a) or
(b) above in respect of any losses, claims, damages or liabilities (or actions
in respect thereof) referred to therein, then each indemnifying party shall
contribute to the amount paid or payable by such indemnified party as a result
of such losses, claims, damages or liabilities (or actions in respect thereof)
in such proportion as is appropriate to reflect the relative benefits received
by the Company on the one hand and the Underwriters on the other from the
offering of the Securities. If, however, the allocation provided by the
immediately preceding sentence is not permitted by applicable law or if the
indemnified party failed to give the notice required under subsection (c) above,
then each indemnifying party shall contribute to such amount paid or payable by
such indemnified party in such proportion as is appropriate to reflect not only
such relative benefits but also the relative fault of the Company on the one
hand and the Underwriters on the other in connection with the statements or
omissions which resulted in such losses, claims, damages or liabilities (or
actions in respect thereof), as well as any other relevant equitable
considerations. The relative benefits received by the Company on the one hand
and the Underwriters on the other shall be deemed to be in the same proportion
as the total net proceeds from the offering (before deducting expenses) received
by the Company bear to the total underwriting discounts and commissions received
by the Underwriters, in each case as set forth in the table on the cover page of
the Prospectus. The relative fault shall be determined by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission or alleged omission to state a material fact relates to
information supplied by the Company on the one hand or the Underwriters on the
other and the parties’ relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. The Company and
the Underwriters agree that it would not be just and equitable if contribution
pursuant to this subsection (d) were determined by pro rata allocation (even if
the Underwriters were treated as one entity for such purpose) or by any other
method of allocation which does not take account of the equitable considerations
referred to above in this subsection (d). The amount paid or payable by an
indemnified party as a result of the losses, claims, damages or liabilities (or
actions in respect thereof) referred to above in this subsection (d) shall be
deemed to include any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. Notwithstanding the provisions of this subsection (d), no Underwriter
shall be required to contribute any amount in excess of the amount by which the
total price at which the Securities underwritten by it and distributed to the
public were offered to the public exceeds the amount of any damages which such
Underwriter has otherwise been required to pay by reason of such untrue or
alleged untrue statement or omission or alleged omission. No person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. The Underwriters’ obligations in this subsection
(d) to contribute are several in proportion to their respective underwriting
obligations and not joint.

(e) The obligations of the Company under this Section 9 shall be in addition to
any liability which the Company may otherwise have and shall extend, upon the
same terms and conditions, to each person, if any, who controls any Underwriter
within the meaning of the Act and each broker-dealer affiliate of any
Underwriter; and the obligations of the Underwriters under this Section 9 shall
be in addition to any liability which the respective Underwriters may otherwise
have and shall extend, upon the same terms and conditions, to each officer and
director of the Company and to each person, if any, who controls the Company
within the meaning of the Act.

10. (a) If any Underwriter shall default in its obligation to purchase the
Securities that it has agreed to purchase hereunder, you may in your discretion
arrange for you or another party or other parties to purchase such Securities on
the terms contained herein. If within 36 hours after such default by any
Underwriter you do not arrange for the purchase of such Securities, then the
Company shall be entitled to a further period of 36 hours within which to
procure another party or other parties reasonably satisfactory to you to
purchase such Securities on such terms. In the event that, within the respective
prescribed periods, you notify the Company that you have so arranged for the
purchase of such Securities, or the Company notifies you that it has so arranged
for the purchase of such Securities, you or the Company shall have the right to
postpone such Time of Delivery for a period of not more than seven days, in
order to effect whatever changes may thereby be made necessary in the
Registration Statement or the Prospectus, or in any other documents or
arrangements, and the Company agrees to file promptly any amendments or
supplements to the Registration Statement or the Prospectus that in your opinion
may thereby be made necessary. The term “Underwriter” as used in this Agreement
shall include any person substituted under this Section with like effect as if
such person had originally been a party to this Agreement with respect to such
Securities.

(b) If, after giving effect to any arrangements for the purchase of the
Securities of a defaulting Underwriter or Underwriters by you and the Company as
provided in subsection (a) above, the aggregate number of such Securities which
remains unpurchased does not exceed one eleventh of the aggregate number of all
the Securities to be purchased, then the Company shall have the right to require
each non-defaulting Underwriter to purchase the number of shares which such
Underwriter agreed to purchase hereunder at such Time of Delivery and, in
addition, to require each non-defaulting Underwriter to purchase its pro rata
share (based on the number of Securities which such Underwriter agreed to
purchase hereunder) of the Securities of such defaulting Underwriter or
Underwriters for which such arrangements have not been made; but nothing herein
shall relieve a defaulting Underwriter from liability for its default.

(c) If, after giving effect to any arrangements for the purchase of the
Securities of a defaulting Underwriter or Underwriters by you and the Company as
provided in subsection (a) above, the aggregate number of such Securities which
remains unpurchased exceeds one eleventh of the aggregate number of all the
Securities to be purchased at such Time of Delivery, or if the Company shall not
exercise the right described in subsection (b) above to require non-defaulting
Underwriters to purchase Securities of a defaulting Underwriter or Underwriters,
then this Agreement (or, with respect to the Second Time of Delivery, the
obligations of the Underwriters to purchase and of the Company to sell the
Optional Securities) shall thereupon terminate, without liability on the part of
any non-defaulting Underwriter or the Company, except for the expenses to be
borne by the Company and the Underwriters as provided in Section 7 hereof and
the indemnity and contribution agreements in Section 9 hereof; but nothing
herein shall relieve a defaulting Underwriter from liability for its default.

11. The respective indemnities, agreements, representations, warranties and
other statements of the Company and the several Underwriters, as set forth in
this Agreement or made by or on behalf of them, respectively, pursuant to this
Agreement, shall remain in full force and effect, regardless of any
investigation (or any statement as to the results thereof) made by or on behalf
of any Underwriter or any controlling person of any Underwriter, or the Company,
or any officer or director or controlling person of the Company, and shall
survive delivery of and payment for the Securities.

12. If this Agreement shall be terminated pursuant to Section 10 hereof, the
Company shall not then be under any liability to any Underwriter except as
provided in Sections 7 and 9 hereof; but, if for any other reason, the
Securities are not delivered by or on behalf of the Company as provided herein,
the Company will reimburse the Underwriters through you for all out of pocket
expenses approved in writing by you, including fees and disbursements of
counsel, reasonably incurred by the Underwriters in making preparations for the
purchase, sale and delivery of the Securities, but the Company shall then be
under no further liability to any Underwriter except as provided in Sections 7
and 9 hereof.

13. In all dealings hereunder, you shall act on behalf of each of the
Underwriters, and the parties hereto shall be entitled to act and rely upon any
statement, request, notice or agreement on behalf of any Underwriter made or
given by you jointly as Representatives or by Goldman, Sachs & Co. on behalf of
you as the Representatives.

All statements, requests, notices and agreements hereunder shall be in writing,
and if to the Underwriters shall be delivered or sent by mail or facsimile
transmission to you as the representatives in care of Goldman, Sachs & Co., 85
Broad Street, 23rd Floor, New York, New York 10004, Attention: Registration
Department; and if to the Company shall be delivered or sent by mail, telex or
facsimile transmission to the address of the Company set forth in the
Registration Statement, Attention: Secretary; with a copy to Latham & Watkins
LLP, 555 Eleventh Street, NW, Suite 1000, Washington, DC 20004, Attention: Scott
C. Herlihy, facsimile number (202) 637-2201; provided, however, that any notice
to an Underwriter pursuant to Section 9(c) hereof shall be delivered or sent by
mail, telex or facsimile transmission to such Underwriter at its address set
forth in its Underwriters’ Questionnaire which address will be supplied to the
Company by you upon request. Any such statements, requests, notices or
agreements shall take effect upon receipt thereof.

In accordance with the requirements of the USA Patriot Act (Title III of Pub. L.
107-56 (signed into law October 26, 2001)), the underwriters are required to
obtain, verify and record information that identifies their respective clients,
including the Company, which information may include the name and address of
their respective clients, as well as other information that will allow the
underwriters to properly identify their respective clients.

14. This Agreement shall be binding upon, and inure solely to the benefit of,
the Underwriters, the Company and, to the extent provided in Sections 9 and 11
hereof, the officers and directors of the Company and each person who controls
the Company or any Underwriter, and their respective heirs, executors,
administrators, successors and assigns, and no other person shall acquire or
have any right under or by virtue of this Agreement. No purchaser of any of the
Securities from any Underwriter shall be deemed a successor or assign by reason
merely of such purchase.

15. Time shall be of the essence of this Agreement. As used herein, the term
“business day” shall mean any day when the Commission’s office in Washington,
D.C. is open for business.

16. The Company acknowledges and agrees that (i) the purchase and sale of the
Securities pursuant to this Agreement is an arm’s-length commercial transaction
between the Company, on the one hand, and the several Underwriters, on the
other, (ii) in connection therewith and with the process leading to such
transaction each Underwriter is acting solely as a principal and not the agent
or fiduciary of the Company, (iii) no Underwriter has assumed an advisory or
fiduciary responsibility in favor of the Company with respect to the offering
contemplated hereby or the process leading thereto (irrespective of whether such
Underwriter has advised or is currently advising the Company on other matters)
or any other obligation to the Company except the obligations expressly set
forth in this Agreement and (iv) the Company has consulted its own legal and
financial advisors to the extent it deemed appropriate. The Company agrees that
it will not claim that the Underwriters, or any of them, has rendered advisory
services of any nature or respect, or owes a fiduciary or similar duty to the
Company, in connection with such transaction or the process leading thereto.

17. This Agreement supersedes all prior agreements and understandings (whether
written or oral) between the Company and the Underwriters, or any of them, with
respect to the subject matter hereof.

18. This Agreement shall be governed by and construed in accordance with the
laws of the State of New York.

19. The Company and each of the Underwriters hereby irrevocably waives, to the
fullest extent permitted by applicable law, any and all right to trial by jury
in any legal proceeding arising out of or relating to this Agreement or the
transactions contemplated hereby.

20. This Agreement may be executed by any one or more of the parties hereto in
any number of counterparts, each of which shall be deemed to be an original, but
all such respective counterparts shall together constitute one and the same
instrument.

21. Notwithstanding anything herein to the contrary, the Company (and the
Company’s employees, representatives and other agents) are authorized to
disclose to any persons the U.S. federal and state income tax treatment and tax
structure of the potential transaction and all materials of any kind (including
tax opinions and other tax analyses) provided to the Company relating to that
treatment and structure, without the Underwriters’ imposing any limitation of
any kind. However, any information relating to the tax treatment and tax
structure shall remain confidential (and the foregoing sentence shall not apply)
to the extent necessary to enable any person to comply with securities laws. For
this purpose, “tax structure” is limited to any facts that may be relevant to
that treatment.

1

If the foregoing is in accordance with your understanding, please sign and
return to us five counterparts hereof, and upon the acceptance hereof by you, on
behalf of each of the Underwriters, this letter and such acceptance hereof shall
constitute a binding agreement between each of the Underwriters and the Company.
It is understood that your acceptance of this letter on behalf of each of the
Underwriters is pursuant to the authority set forth in a form of Agreement among
Underwriters, the form of which shall be submitted to the Company for
examination upon request, but without warranty on your part as to the authority
of the signers thereof.

Very truly yours,

USEC Inc.

     
By:
  /s/ John C. Barpoulis
 
   
 
  Name: John C. Barpoulis
Title: Senior Vice President &
Chief Financial Officer

Accepted as of the date hereof on

behalf of each of the Underwriters:

Goldman, Sachs & Co.

By: /s/ Goldman, Sachs & Co.

(Goldman, Sachs & Co.)
Merrill Lynch, Pierce, Fenner & Smith

    Incorporated

By:/s/ Jeff Kulik
Name: Jeff Kulik
Title: Managing Director

                  SCHEDULE I                         Number of Optional        
    Securities to be     Total Number of   Purchased if     Firm Securities  
Maximum Option     to be Purchased   Exercised Underwriter                
Goldman, Sachs & Co.
    8,600,000       1,290,000  
Merrill Lynch, Pierce, Fenner & Smith Incorporated
    5,600,000       840,000  
Wachovia Capital Markets, LLC
    3,100,000       465,000  
Jefferies & Company, Inc.
    1,350,000       202,500  
Natexis Bleichroeder Inc.
    1,350,000       202,500  
Total
    20,000,000       23,000,000  

2

SCHEDULE II

(a) Issuer Free Writing Prospectuses Not Included in the Pricing Disclosure
Package:

(i) Press Release, dated September 14, 2007

(ii) Electronic Roadshow

(iii) Press Release, dated September 24, 2007

(b) Issuer Free Writing Prospectuses Included in the Pricing Disclosure Package:

(i) Pricing Term Sheet

(c) Additional Documents Incorporated by Reference:

3