Document:

EX-4.1

EXHIBIT 4.1

USEC INC.

AND

WELLS FARGO BANK, N.A.

Trustee

______________

Indenture

Dated as of September 28, 2007

3.0% Convertible Senior Notes due 2014

1

Certain Sections of this Indenture relating to Sections 310 through 318

of the Trust Indenture Act of 1939:

	 	 	 	 	 
	Trust Indenture	 	 	 	 
	Act Section

	 	Indenture Section

	§ 310(a)(1)

	 	 	609	 
	(a)(2)

	 	 	609	 
	(a)(3)

	 	Not Applicable

	(a)(4)

	 	Not Applicable

	(b)

	 	 	608	 
	
 
	 	 	610	 
	§ 311(a)

	 	 	613	 
	(b)

	 	 	613	 
	§ 312(a)

	 	 	701	 
	
 
	 	 	702	(a)
	(b)

	 	 	702	(b)
	(c)

	 	 	702	(c)
	§ 313(a)

	 	 	703	(a)
	(a)(4)

	 	 	101	 
	
 
	 	 	703	(a)
	(b)

	 	 	703	(a)
	(c)

	 	 	703	(a)
	(d)

	 	 	703	(a)
	§ 314(a)

	 	 	704	 
	(b)

	 	Not Applicable

	(c)(1)

	 	 	102	 
	(c)(2)

	 	 	102	 
	(c)(3)

	 	Not Applicable

	(d)

	 	Not Applicable

	(e)

	 	 	102	 
	§ 315(a)

	 	 	601	 
	(b)

	 	 	602	 
	(c)

	 	 	601	 
	(d)

	 	 	601	 
	(e)

	 	 	514	 
	§ 316(a)

	 	 	101	 
	(a)(1)(A)

	 	 	502	 
	
 
	 	 	512	 
	(a)(1)(B)

	 	 	513	 
	(a)(2)

	 	Not Applicable

	(b)

	 	 	508	 
	(c)

	 	 	104	(c)
	§ 317(a)(1)

	 	 	503	 
	(a)(2)

	 	 	504	 
	(b)

	 	 	1003	 
	§ 318(a)

	 	 	107	 

     

Note: This reconciliation and tie shall not, for any purpose, be deemed to be a part of the
Indenture.

	 	 	 	 	 	 	 	 	 
	Parties
	 		1		 	sc>

	recitals of the company
	 	 	 	 	 		1	
	ARTICLE ONE Definitions and Other Provisions of General Application
	 	 	 	 
	SECTION 101.
	 	Definitions.
	 	 	 	 
	SECTION 102.
	 	Compliance Certificates and Opinions.
	 	 	 	 
	SECTION 103.
	 	Form of Documents Delivered to Trustee.
	 	 	 	 
	SECTION 104.
	 	Acts of Holders; Record Dates.
	 	 	 	 
	SECTION 105.
	 	Notices, Etc., to Trustee and Company.
	 	 	 	 
	SECTION 106.
	 	Notice to Holders; Waiver.
	 	 	 	 
	SECTION 107.
	 	Conflict with Trust Indenture Act.
	 	 	 	 
	SECTION 108.
	 	Effect of Headings and Table of Contents.
	 	 	 	 
	SECTION 109.
	 	Successors and Assigns.
	 	 	 	 
	SECTION 110.
	 	Separability Clause.
	 	 	 	 
	SECTION 111.
	 	Benefits of Indenture.
	 	 	 	 
	SECTION 112.
	 	Governing Law.
	 	 	 	 
	SECTION 113.
	 	Legal Holidays.
	 	 	 	 
	SECTION 114.
	 	Indenture and Securities Solely Corporate Obligations.
	 	 	 	 
	SECTION 115.
	 	Indenture May be Executed in Counterparts.
	 	 	 	 
	SECTION 116.
	 	Acceptance of Trust.
	 	 	 	 

	 	 	 
	ARTICLE TWO Security Forms

	SECTION 201.

SECTION 202.

SECTION 203.

SECTION 204.

SECTION 205.

SECTION 206.

SECTION 207.

SECTION 208.

	 	Forms Generally.

Form of Face of Security.

Form of Reverse of Security.

Form of Legend for Global Securities

Form of Notice of Conversion

Form of Assignment.

Form of Trustee’s Certificate of Authentication.

Form of Fundamental Change Repurchase Notice.

	 	 	 
	ARTICLE THREE The Securities

	SECTION 301.

SECTION 302.

SECTION 303.

SECTION 304.

SECTION 305.

SECTION 306.

SECTION 307.

SECTION 308.

SECTION 309.

SECTION 310.

SECTION 311.

SECTION 312.

SECTION 313.

	 	Title and Terms; Principal and Interest.

Denominations.

Global Securities; Non-Global Securities; Book-entry Provisions.

Execution, Authentication, Delivery and Dating.

Temporary Securities.

Registrar, Registration of Transfer and Exchange; Paying Agent.

Mutilated, Destroyed, Lost and Stolen Securities.

Payment of Interest; Interest Rights Preserved.

Persons Deemed Owners.

Cancellation.

CUSIP Numbers.

Computation of Interest.

Special Record Date.

	 	 	 
	ARTICLE FOUR Satisfaction and Discharge

	SECTION 401.

SECTION 402.

	 	Satisfaction and Discharge of Indenture.

Application of Trust Money.

	 	 	 
	ARTICLE FIVE Remedies

	SECTION 501.

SECTION 502.

SECTION 503.

SECTION 504.

SECTION 505.

SECTION 506.

SECTION 507.

SECTION 508.

SECTION 509.

SECTION 510.

SECTION 511.

SECTION 512.

SECTION 513.

SECTION 514.

SECTION 515.

	 	Events of Default.

Acceleration of Maturity; Rescission and Annulment.

Collection of Indebtedness and Suits for Enforcement by Trustee.

Trustee May File Proofs of Claim.

Trustee May Enforce Claims Without Possession of Securities.

Application of Money Collected.

Limitation on Suits.

Unconditional Right of Holders to Receive Principal and Interest

and to Convert

Restoration of Rights and Remedies.

Rights and Remedies Cumulative.

Delay or Omission Not Waiver.

Control by Holders.

Waiver of Past Defaults.

Undertaking for Costs.

Waiver of Stay or Extension Laws.

	 	 	 
	ARTICLE SIX The Trustee

	SECTION 601.

SECTION 602.

SECTION 603.

SECTION 604.

SECTION 605.

SECTION 606.

SECTION 607.

SECTION 608.

SECTION 609.

SECTION 610.

SECTION 611.

SECTION 612.

SECTION 613.

SECTION 614.

	 	Certain Duties and Responsibilities.

Notice of Defaults.

Certain Rights of Trustee.

Not Responsible for Recitals or Issuance of Securities.

May Hold Securities.

Money Held in Trust.

Compensation and Reimbursement.

Disqualification; Conflicting Interests.

Corporate Trustee Required; Eligibility.

Resignation and Removal; Appointment of Successor.

Acceptance of Appointment by Successor.

Merger, Conversion, Consolidation or Succession to Business.

Preferential Collection of Claims Against Company.

Appointment of Authenticating Agent.

	 	 	 
	ARTICLE SEVEN Holders’ Lists and Reports by Trustee and Company

	SECTION 701.

SECTION 702.

SECTION 703.

SECTION 704.

	 	Company to Furnish Trustee Names and Addresses of Holders.

Preservation of Information; Communications to Holders.

Reports by Trustee.

Reports by Company.

	 	 	 
	ARTICLE EIGHT Consolidation, Merger, Conveyance, Transfer or Lease

	SECTION 801.

SECTION 802.

	 	Company May Consolidate, Etc., Only on Certain Terms.

Successor Substituted.

	 	 	 
	ARTICLE NINE Modification and Amendment

	SECTION 901.

SECTION 902.

SECTION 903.

SECTION 904.

SECTION 905.

SECTION 906.

ARTICLE TEN Covenants

SECTION 1001.

SECTION 1002.

SECTION 1003.

SECTION 1004.

SECTION 1005.

SECTION 1006.

SECTION 1007.

SECTION 1008.

SECTION 1009.

	 	Supplemental Indentures Without Consent of Holders.

Supplemental Indentures with Consent of Holders.

Execution of Supplemental Indentures.

Effect of Supplemental Indentures.

Conformity with Trust Indenture Act.

Reference in Securities to Supplemental Indentures.

Payment of Principal and Interest.

Maintenance of Office or Agency.

Money for Security Payments to Be Held in Trust.

Statement by Officers as to Default.

Existence.

Maintenance of Properties.

Payment of Taxes and Other Claims.

[Reserved]

Waiver of Certain Covenants.

	 	 	 
	ARTICLE ELEVEN Repurchase at Option of the Holder

	SECTION 1101.

	 	Repurchase at the Option of the Holder Upon a

Fundamental Change.

	 	 	 
	ARTICLE TWELVE Conversion of Securities

	SECTION 1201.

SECTION 1202.

SECTION 1203.

SECTION 1204.

SECTION 1205.

SECTION 1206.

SECTION 1207.

SECTION 1208.

SECTION 1209.

SECTION 1210.

SECTION 1211.

SECTION 1212.

Signatures

Schedule A

	 	Conversion Privilege and Conversion Rate.

Exercise of Conversion Privilege.

Fractions of Shares.

Adjustment of Conversion Rate.

Notice of Adjustments of Conversion Rate.

Company to Reserve Common Stock.

Taxes on Conversions.

Certain Covenants.

Cancellation of Converted Securities.

Provision in Case of Effect of Reclassification,

Consolidation, Merger or Sale.

Responsibility of Trustee for Conversion Provisions.

Right to Set-off Withholding Taxes.

2

INDENTURE, dated as of September 28, 2007, between USEC INC., a Delaware corporation
(the “Company”), having its principal office at 2 Democracy Center, 6903 Rockledge Drive, Bethesda,
Maryland 20817 and Wells Fargo Bank, N.A., a national banking association, as Trustee (herein
called the “Trustee”).

RECITALS OF THE COMPANY

The Company has duly authorized the creation of an issue of its 3.0% Convertible Senior Notes
due 2014 (herein called the “Initial Securities” and together with any Additional Securities, the
“Securities”) of substantially the tenor and amount hereinafter set forth, and to provide the terms
and conditions upon which the Securities are to be authenticated, issued and delivered, the Company
has duly authorized the execution and delivery of this Indenture.

All things necessary to make the Securities, when executed by the Company and authenticated
and delivered as provided herein and duly issued by the Company, the valid obligations of the
Company, and to make this Indenture a valid agreement of the Company, in accordance with their and
its terms, have been done.

NOW, THEREFORE, THIS INDENTURE WITNESSETH:

For and in consideration of the premises and the purchase of the Securities by the Holders
thereof, it is mutually agreed, for the equal and proportionate benefit of all Holders of the
Securities, as follows:

ARTICLE ONE

Definitions and Other Provisions of General Application

	 	 	SECTION 101. Definitions.

For all purposes of this Indenture, except as otherwise expressly provided or unless the
context otherwise requires:

(1) the terms defined in this Article have the meanings assigned to them in this
Article and include the plural as well as the singular;

(2) all other terms used herein which are defined in the Trust Indenture Act, either
directly or by reference therein, have the meanings assigned to them therein;

(3) all accounting terms not otherwise defined herein have the meanings assigned to
them in accordance with generally accepted accounting principles, and, except as otherwise
herein expressly provided, the term “generally accepted accounting principles” in the
United States with respect to any computation required or permitted hereunder shall mean
such accounting principles as are generally accepted at the date of this Indenture; and

(4) the words “herein”, “hereof” and “hereunder” and other words of similar import
refer to this Indenture as a whole and not to any particular Article, Section or other
subdivision.

“Act”, when used with respect to any Holder, has the meaning specified in Section 104.

“Additional Securities” means an unlimited maximum aggregate principal amount of Securities
(other than the Initial Securities) issued under this Indenture.

“Affiliate” of any specified Person means any other Person directly or indirectly controlling
or controlled by or under direct or indirect common control with such specified Person. For the
purposes of this definition, “control” when used with respect to any specified Person means the
power to direct or cause the direction of the management and policies of such Person, directly or
indirectly, whether through the ownership of voting securities, by contract or otherwise; and the
terms “controlling” and “controlled” have meanings correlative to the foregoing.

“Agent Member” means any member of, or participant in, the Depositary.

“Applicable Procedures” with respect to any transfer or transaction involving a Global
Security or beneficial interest therein, the rules and procedures of DTC or any successor
Depositary, in each case to the extent applicable to such transaction and as in effect from time to
time.

“Authenticating Agent” means any Person authorized by the Trustee pursuant to Section 614 to
act on behalf of the Trustee to authenticate Securities.

“Board of Directors” means either the board of directors of the Company or any duly authorized
committee of that board.

“Board Resolution” means a copy of a resolution certified by the Secretary or an Assistant
Secretary of the Company to have been duly adopted by the Board of Directors and to be in full
force and effect on the date of such certification, and delivered to the Trustee.

“Business Day” means each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day
on which banking institutions in the City of New York are authorized or obligated by law,
regulation or executive order to close.

“Capital Stock” means, for any entity, any and all shares, interests, rights to purchase,
warrants, options, participations or other equivalents of or interests in (however designated)
stock issued by that entity.

“Commission” or “SEC” means the Securities and Exchange Commission, as from time to time
constituted, created under the Exchange Act, or, if at any time after the execution of this
Indenture such Commission is not existing and performing the duties now assigned to it under the
Trust Indenture Act, then the body performing such duties at such time.

“Common Stock” includes any stock of any class of the Company which has no preference in
respect of dividends or of amounts payable in the event of any voluntary or involuntary
liquidation, dissolution or winding-up of the Company and which is not subject to redemption by the
Company. However, subject to the provisions of Section 1210, shares issuable on conversion of
Securities shall include only shares of the class designated as Common Stock of the Company at the
date of this Indenture or shares of any class or classes resulting from any reclassification or
reclassifications thereof and which have no preference in respect of dividends or of amounts
payable in the event of any voluntary or involuntary liquidation, dissolution or winding-up of the
Company and which are not subject to redemption by the Company; provided that if at any time there
shall be more than one such resulting class, the shares of each such class then so issuable shall
be substantially in the proportion which the total number of shares of such class resulting from
all such reclassifications bears to the total number of shares of all such classes resulting from
all such reclassifications.

“Company” means the Person named as the “Company” in the first paragraph of this Indenture
until a successor Person shall have become such pursuant to the applicable provisions of this
Indenture, and thereafter “Company” shall mean such successor Person.

“Company Request” or “Company Order” means a written request or order signed in the name of
the Company by the principal executive, financial or accounting officer of the Company.

“Conversion Agent” means the person authorized by the Company to convert Securities in
accordance with Article Twelve.

“Conversion Date” means the date on which a holder complies with the conversion requirements
in Section 1202.

“Conversion Price” means at any time the amount equal to $1,000 divided by the then applicable
Conversion Rate.

“Conversion Rate” has the meaning specified in Section 1201.

“Corporate Trust Office” means the principal office of the Trustee at which at any particular
time its corporate trust business shall be administered or the office of the Trustee located at 625
Marquette Ave., Minneapolis, Minnesota 55479, as applicable.

“corporation” means a corporation, association, company, joint-stock company or business
trust.

“Defaulted Interest” has the meaning specified in Section 308.

“DTC” means The Depository Trust Company, a New York corporation, or any successor.

“Effective Date” means the date on which a Make-Whole Fundamental Change occurs or becomes
effective.

“Event of Default” has the meaning specified in Section 501.

“Exchange Act” means the Securities Exchange Act of 1934, as amended.

“Ex-date” means, with respect to any issuance or distribution on the Common Stock, the first
date on which the shares of the Common Stock trade on the relevant exchange or in the relevant
market, regular way, without the right to receive such issuance or distribution.

“Fundamental Change” will be deemed to have occurred if any of the following occurs after the
Securities are originally issued:

(1) any Person acquires beneficial ownership directly or indirectly, through a
purchase, merger or other acquisition transaction or series of transactions, of shares of
the Company’s Capital Stock entitling the Person to exercise 50% or more of the total
voting power of all shares of the Company’s Capital Stock entitled to vote generally in
elections of directors, other than an acquisition by the Company, any of the Company’s
Subsidiaries or any of the Company’s employee benefit plans (for purposes of this clause
(1), whether a Person is a “beneficial owner” shall be determined in accordance with Rule
13d-3 under the Exchange Act, and “Person” shall include any syndicate or group that would
be deemed to be a “person” under Section 13(d)(3) of the Exchange Act); or

(2) the Company (i) merges or consolidates with or into any other Person (other than a
Subsidiary), another Person merges with or into the Company, or the Company conveys, sells,
transfers or leases all or substantially all of the Company’s assets to another Person or
(ii) engages in any recapitalization, reclassification or other transaction in which all or
substantially all of the Common Stock is exchanged for or converted into cash, securities
or other property, in each case other than a merger or consolidation:

(a) that does not result in a reclassification, conversion, exchange or
cancellation of the Company’s outstanding Common Stock;

(b) which is effected solely to change the Company’s jurisdiction of
incorporation and results in a reclassification, conversion or exchange of
outstanding shares of the Company’s Common Stock solely into shares of common stock
of the surviving entity; or

(c) pursuant to which the consideration received by the holders of the
Company’s Common Stock immediately prior to the transaction entitles such holders
to exercise, directly or indirectly, 50% or more of the voting power of all shares
of Capital Stock entitled to vote generally in the election of directors of the
continuing or surviving corporation immediately following such merger or
consolidation; or

(3) the Company is liquidated or dissolved or holders of the Common Stock approve any
plan or proposal for the Company’s liquidation or dissolution; or

(4) shares of Common Stock, or shares of any other Capital Stock or American
Depositary Receipts in respect of shares of Capital Stock into which the Securities are
convertible pursuant to the terms of this Indenture, are not listed for trading on any of
the New York Stock Exchange, the American Stock Exchange, the NASDAQ Global Market or the
NASDAQ Global Select Market (or any of their respective successors).

“Fundamental Change Expiration Time” has the meaning specified in Section 1101.

“Fundamental Change Repurchase Date” has the meaning specified in Section 1101.

“Fundamental Change Repurchase Notice” has the meaning specified in Section 1101.

“Fundamental Change Repurchase Price” has the meaning specified in Section 1101.

“Global Security” means a Security that is registered in the Security Register in the name of
a Depositary or a nominee thereof.

“Holder” means a Person in whose name a Security is registered in the Security Register.

“Indenture” means this instrument as originally executed or as it may from time to time be
supplemented or amended by one or more indentures supplemental hereto entered into pursuant to the
applicable provisions hereof, including, for all purposes of this instrument and any such
supplemental indenture, the provisions of the Trust Indenture Act that are deemed to be a part of
and govern this instrument and any such supplemental indenture, respectively.

“Initial Securities” has the meaning specified in the Recitals.

“Interest Payment Date” means the Stated Maturity of an installment of interest on the
Securities.

“Issue Date” with respect to the Initial Securities shall mean September 28, 2007, and with
respect to any Additional Securities, the date of original issuance of such Additional Securities.

“Last Reported Sale Price” means, with respect to the Common Stock or any other security for
which a Last Reported Sale Price must be determined, on any date, the closing sale price per share
of the Common Stock or unit of such other security (or, if no closing sale price is reported, the
average of the last bid and last ask prices or, if more than one in either case, the average of the
average last bid and the average last ask prices) on such date as reported in composite
transactions for the principal United States national or regional securities exchange on which it
is then traded, if any. If the Common Stock or such other security is not listed for trading on a
United States national or regional securities exchange on the relevant date, the Last Reported Sale
Price shall be the average of the last quoted bid and ask prices per share of Common Stock or such
other security in the over-the-counter market on the relevant date, as reported by the National
Quotation Bureau or similar organization. In the absence of such quotation, the Last Reported Sale
Price shall be the average of the mid-point of the last bid and ask prices for the Common Stock or
such other security on the relevant date from each of at least three nationally recognized
independent investment banking firms, which may include the Underwriters, selected from time to
time by the Company for that purpose. The Last Reported Sale Price shall be determined without
reference to extended or after hours trading. Any such determination shall be made by the Company
and shall be conclusive absent manifest error.

“Make-Whole Fundamental Change” means any transaction or event that constitutes a Fundamental
Change.

“Make-Whole Reference Date” shall have the meaning in Section 1201.

“Market Capitalization” means the fair market value of the Common Stock, multiplied by the
number of shares of the Common Stock then outstanding on the date of the repurchase triggering the
adjustment immediately prior to such repurchase.

“Market Disruption Event” means the occurrence or existence on any Scheduled Trading Day for
the Common Stock of any suspension or limitation imposed on trading (by reason of movements in
price exceeding limits permitted by the stock exchange or otherwise) in the Common Stock or in any
options contracts or futures contracts relating to the Common Stock, and such suspension or
limitation occurs or exists at any time within the 30 minutes prior to the closing time of the
relevant exchange on such day.

“Maturity”, when used with respect to any Security, means the date on which the principal of
such Security becomes due and payable as therein or herein provided, whether at the Stated Maturity
or by declaration of acceleration, required repurchase or otherwise.

“Maturity Date” means October 1, 2014.

“Measurement Period” has the meaning specified in Section 1201.

“Notice of Conversion” has the meaning specified in Section 1202.

“Officer” means the Chairman of the Board, a Vice Chairman of the Board, the Chief Executive
Officer, the President, any Vice President, the Chief Financial Officer, the Treasurer, an
Assistant Treasurer, the Secretary or any Assistant Secretary.

“Officers’ Certificate” means a certificate signed by the principal executive officer,
principal accounting officer or principal financial officer of the Company and delivered to the
Trustee.

“Opinion of Counsel” means a written opinion of counsel, who may be counsel for, or an
employee of, the Company, and who shall be reasonably acceptable to the Trustee.

“Outstanding”, when used with respect to Securities, means, as of the date of determination,
all Securities theretofore authenticated and delivered under this Indenture, except:

(i) Securities theretofore cancelled by the Trustee or delivered to the Trustee for
cancellation;

(ii) Securities for whose payment or redemption money in the necessary amount has been
theretofore deposited with the Trustee or any Paying Agent (other than the Company) in
trust or set aside and segregated in trust by the Company (if the Company shall act as its
own Paying Agent) for the Holders of such Securities; provided that, if such
Securities are to be redeemed, notice of such redemption has been duly given pursuant to
this Indenture or provision therefor satisfactory to the Trustee has been made; and

(iii) Securities which have been paid pursuant to Section 306 or in exchange for or in
lieu of which other Securities have been authenticated and delivered pursuant to this
Indenture, other than any such Securities in respect of which there shall have been
presented to the Trustee proof satisfactory to it that such Securities are held by a bona
fide purchaser in whose hands such Securities are valid obligations of the Company;

provided, however, that in determining whether the Holders of the requisite
principal amount of the Outstanding Securities have given any request, demand, authorization,
direction, notice, consent or waiver hereunder, Securities owned by the Company or any other
obligor upon the Securities or any Affiliate of the Company or of such other obligor shall be
disregarded and deemed not to be Outstanding, except that, in determining whether the Trustee shall
be protected in relying upon any such request, demand, authorization, direction, notice, consent or
waiver, only Securities which the Trustee knows to be so owned shall be so disregarded. Securities
so owned which have been pledged in good faith may be regarded as Outstanding if the pledgee
establishes to the satisfaction of the Trustee the pledgee’s right so to act with respect to such
Securities and that the pledgee is not the Company or any other obligor upon the Securities or any
Affiliate of the Company or of such other obligor.

“Paying Agent” means any Person authorized by the Company to pay the principal of or interest
on any Securities on behalf of the Company, and shall initially be the Trustee.

“Person” means any individual, corporation, limited liability company, partnership, joint
venture, trust, unincorporated organization or government or any agency or political subdivision
thereof.

“Predecessor Security” of any particular Security means every previous Security evidencing all
or a portion of the same debt as that evidenced by such particular Security; and, for the purposes
of this definition, any Security authenticated and delivered under Section 307 in exchange for or
in lieu of a mutilated, destroyed, lost or stolen Security shall be deemed to evidence the same
debt as the mutilated, destroyed, lost or stolen Security.

“Regular Record Date” for the interest payable on any Interest Payment Date means the March 15
or September 15 (whether or not a Business Day), as the case may be, next preceding such Interest
Payment Date.

“Responsible Officer”, when used with respect to the Trustee, means the chairman or any
vice-chairman of the board of directors, the chairman or any vice-chairman of the executive
committee of the board of directors, the chairman of the trust committee, the president, any vice
president, the secretary, any assistant secretary, the treasurer, any assistant treasurer, the
cashier, any assistant cashier, any trust officer or assistant trust officer, the controller or any
assistant controller or any other officer of the Trustee customarily performing functions similar
to those performed by any of the above designated officers and also means, with respect to a
particular corporate trust matter, any other officer to whom such matter is referred because of his
knowledge of and familiarity with the particular subject.

“Scheduled trading day” means a day that is scheduled to be a trading day on the principal
U.S. national or regional securities exchange or market on which our common stock is listed or
admitted for trading or, if our common stock is not listed or admitted for trading on any exchange
or market, a Business Day.

“Security” and “Securities” have the meaning specified in the Recitals and include the Initial
Securities and any Additional Securities. The Initial Securities and Additional Securities shall
be treated as a single class for all purposes under this Indenture.

“Security Register” and “Security Registrar” have the respective meanings specified in Section
306.

“Significant Subsidiaries” means any direct or indirect Subsidiary of the Company within the
meaning of Section 1-02(w) of Regulation S-X as promulgated by the Commission.

“Special Record Date” for the payment of any Defaulted Interest means a date fixed by the
Trustee pursuant to Section 308.

“Stated Maturity”, when used with respect to any Security or any installment of interest
thereon, means the date specified in such Security as the fixed date on which the principal of such
Security or such installment of interest is due and payable.

“Stock Price” means the price paid per share of Common Stock in connection with a Make-Whole
Fundamental Change pursuant to which Additional Shares shall be added to the Conversion Rate as set
forth in Article Twelve, which shall be equal to (i) if holders of Common Stock receive only cash
in such Make-Whole Fundamental Change, the cash amount paid per share of Common Stock and (ii) in
all other cases, the average of the Last Reported Sale Prices of the Common Stock over the ten
consecutive Trading Day period ending on the Trading Day preceding the date on which such
Fundamental Change occurs or becomes effective.

“Subsidiary” means a corporation more than 50% of the outstanding voting stock of which is
owned, directly or indirectly, by the Company or by one or more other Subsidiaries, or by the
Company and one or more other Subsidiaries. For the purposes of this definition, “voting stock”
means stock which ordinarily has voting power for the election of directors, whether at all times
or only so long as no senior class of stock has such voting power by reason of any contingency.

“Trading day” means a day during which (i) trading in the Common Stock generally occurs and
(ii) there is no Market Disruption Event.

“Trading Price” with respect to any Securities, on any date of determination, means the
average of the secondary market bid quotations obtained by the Trustee for $1.0 million principal
amount of such Securities at approximately 3:30 p.m., New York City time, on such determination
date from three independent nationally recognized securities dealers (which may include the
Underwriters) selected by the Company; provided that if three such bids cannot reasonably be
obtained by the Trustee, but two such bids are obtained, then the average of the two bids shall be
used, and if only one such bid can reasonably be obtained by the Trustee, that one bid shall be
used. Any such determination by the Trustee shall be conclusive absent manifest error.

“Trustee” means the Person named as the “Trustee” in the first paragraph of this Indenture
until a successor Trustee shall have become such pursuant to the applicable provisions of this
Indenture, and thereafter “Trustee” shall mean such successor Trustee.

“Trust Indenture Act” means the Trust Indenture Act of 1939 as in force at the date as of
which this Indenture was executed; provided, however, that in the event the Trust
Indenture Act of 1939 is amended after such date, “Trust Indenture Act” means, to the extent
required by any such amendment, the Trust Indenture Act of 1939 as so amended.

“Underwriters” means Goldman, Sachs & Co. and Wachovia Capital Markets, LLC, as
representatives of the several underwriters.

“Vice President”, when used with respect to the Company or the Trustee, means any vice
president, whether or not designated by a number or a word or words added before or after the title
“vice president”.

This Indenture is subject to the mandatory provisions of the Trust Indenture Act, which are
incorporated by reference in and made a part of this Indenture. The following Trust Indenture Act
terms have the following meanings:

“Indenture Securities” means the Securities.

“Indenture Security Holder” means a Holder.

“Indenture to be Qualified” means this Indenture.

“Indenture Trustee” or “Institutional Trustee” means the Trustee.

All other terms in this Indenture that are defined by the Trust Indenture Act, defined by it
by reference to another statute or defined by SEC rule have the meanings assigned to them by such
definitions. If any provision hereof limits, qualifies or conflicts with another provision hereof
which is required to be included in this Indenture by the Trust Indenture Act, such required
provision shall control.

	 	 	SECTION 102. Compliance Certificates and Opinions.

Upon any application or request by the Company to the Trustee to take any action under any
provision of this Indenture, the Company shall furnish to the Trustee such certificates and
opinions as may be required under the Trust Indenture Act. Each such certificate or opinion shall
be given in the form of an Officers’ Certificate, if to be given by an officer of the Company, or
an Opinion of Counsel, if to be given by counsel, and shall comply with the requirements of the
Trust Indenture Act and any other requirement set forth in this Indenture.

Every certificate or opinion with respect to compliance with a condition or covenant provided
for in this Indenture shall include

(1) a statement that each individual signing such certificate or opinion has read such
covenant or condition and the definitions herein relating thereto;

(2) a brief statement as to the nature and scope of the examination or investigation
upon which the statements or opinions contained in such certificate or opinion are based;

(3) a statement that, in the opinion of each such individual, he has made such
examination or investigation as is necessary to enable him to express an informed opinion
as to whether or not such covenant or condition has been complied with; and

(4) a statement as to whether, in the opinion of each such individual, such condition
or covenant has been complied with.

	 	 	SECTION 103. Form of Documents Delivered to Trustee.

In any case where several matters are required to be certified by, or covered by an opinion
of, any specified Person, it is not necessary that all such matters be certified by, or covered by
the opinion of, only one such Person, or that they be so certified or covered by only one document,
but one such Person may certify or give an opinion with respect to some matters and one or more
other such Persons as to other matters, and any such Person may certify or give an opinion as to
such matters in one or several documents.

Any certificate or opinion of an officer of the Company may be based, insofar as it relates to
legal matters, upon a certificate or opinion of, or representations by, counsel, unless such
officer knows, or in the exercise of reasonable care should know, that the certificate or opinion
or representations with respect to the matters upon which his certificate or opinion is based are
erroneous. Any such certificate or opinion of counsel may be based, insofar as it relates to
factual matters, upon a certificate or opinion of, or representations by, an officer or officers of
the Company stating that the information with respect to such factual matters is in the possession
of the Company, unless such counsel knows, or in the exercise of reasonable care should know, that
the certificate or opinion or representations with respect to such matters are erroneous. Any such
certificate or opinion of counsel may be based, insofar as it relates to accounting matters, upon a
certificate or opinion of, or representations by, an accountant (who may be an employee of the
Company) or firm of accountants, unless such counsel knows, or in the exercise of reasonable care
should know, that the certificate or opinion or representations with respect to such matters are
erroneous.

Where any Person is required to make, give or execute two or more applications, requests,
consents, certificates, statements, opinions or other instruments under this Indenture, they may,
but need not, be consolidated and form one instrument.

	 	 	SECTION 104. Acts of Holders; Record Dates.

(a) Any request, demand, authorization, direction, notice, consent, waiver or other action
provided or permitted by this Indenture to be given, made or taken by Holders may be embodied in
and evidenced by one or more instruments of substantially similar tenor signed by such Holders in
person or by agent duly appointed in writing; and, except as herein otherwise expressly provided,
such action shall become effective when such instrument or instruments are delivered to the Trustee
and, where it is hereby expressly required, to the Company. The Trustee shall promptly deliver to
the Company copies of all such instruments or instruments and records delivered to the Trustee.
Such instrument or instruments (and the action embodied therein and evidenced thereby) are herein
sometimes referred to as the “Act” of the Holders signing such instrument or instruments. Proof of
execution of any such instrument or of a writing appointing any such agent shall be sufficient for
any purpose of this Indenture and (subject to Section 601) conclusive in favor of the Trustee and
the Company, if made in the manner provided in this Section.

(b) The fact and date of the execution by any Person of any such instrument or writing may be
proved by the affidavit of a witness of such execution or by a certificate of a notary public or
other officer authorized by law to take acknowledgments of deeds, certifying that the individual
signing such instrument or writing acknowledged to him the execution thereof. Where such execution
is by a signer acting in a capacity other than his individual capacity, such certificate or
affidavit shall also constitute sufficient proof of his authority. The fact and date of the
execution of any such instrument or writing, or the authority of the Person executing the same, may
also be proved in any other manner which the Trustee deems sufficient.

(c) The Company may, in the circumstances permitted by the Trust Indenture Act, fix any day as
the record date for the purpose of determining the Holders entitled to give or take any request,
demand, authorization, direction, notice, consent, waiver or other action, or to vote on any
action, authorized or permitted to be given or taken by Holders. If not set by the Company prior
to the first solicitation of a Holder made by any Person in respect of any such action, or, in the
case of any such vote, prior to such vote, the record date for any such action or vote shall be the
30th day (or, if later, the date of the most recent list of Holders required to be provided
pursuant to Section 701) prior to such first solicitation or vote, as the case may be. With regard
to any record date, only the Holders on such date (or their duly designated proxies) shall be
entitled to give or take, or vote on, the relevant action.

(d) The ownership of Securities shall be proved by the Security Register.

(e) Any request, demand, authorization, direction, notice, consent, waiver or other Act of the
Holder of any Security shall bind every future Holder of the same Security and the Holder of every
Security issued upon the registration of transfer thereof or in exchange therefor or in lieu
thereof in respect of anything done, omitted or suffered to be done by the Trustee or the Company
in reliance thereon, whether or not notation of such action is made upon such Security.

	 	 	SECTION 105. Notices, Etc., to Trustee and Company.

Any request, demand, authorization, direction, notice, consent, waiver or Act of Holders or
other document provided or permitted by this Indenture to be made upon, given or furnished to, or
filed with,

(1) the Trustee by any Holder or by the Company shall be sufficient for every purpose
hereunder if made, given, furnished or filed in writing (or by facsimile transmission to
(860) 704-6219, provided that oral confirmation of receipt shall have been received) to or
with the Trustee at its Corporate Trust Office, or such other means reasonably acceptable
to the Trustee, or

(2) the Company by the Trustee or by any Holder shall be sufficient for every purpose
hereunder (unless otherwise herein expressly provided) if in writing and mailed,
first-class postage prepaid, to the Company addressed to it at the address of its principal
office specified in the first paragraph of this Indenture or at any other address
previously furnished in writing to the Trustee by the Company, Attention: Chief Financial
Officer, with a copy to the Secretary or such other means reasonably acceptable to the
Company.

	 	 	SECTION 106. Notice to Holders; Waiver.

Where this Indenture provides for notice to Holders of any event, such notice shall be
sufficiently given (unless otherwise herein expressly provided) if in writing and mailed,
first-class postage prepaid, to each Holder affected by such event, at his address as it appears in
the Security Register, or by such other means reasonably acceptable to the Holder, in each case not
later than the latest date (if any), and not earlier than the earliest date (if any), prescribed
for the giving of such notice. In any case where notice to Holders is given by mail, neither the
failure to mail such notice, nor any defect in any notice so mailed, to any particular Holder shall
affect the sufficiency of such notice with respect to other Holders. Where this Indenture provides
for notice in any manner, such notice may be waived in writing by the Person entitled to receive
such notice, either before or after the event, and such waiver shall be the equivalent of such
notice. Waivers of notice by Holders shall be filed with the Trustee, but such filing shall not be
a condition precedent to the validity of any action taken in reliance upon such waiver.

In case by reason of the suspension of regular mail service or by reason of any other cause it
shall be impracticable to give such notice by mail, then such notification as shall be made with
the approval of the Trustee shall constitute a sufficient notification for every purpose hereunder.

	 	 	SECTION 107. Conflict with Trust Indenture Act.

If any provision hereof limits, qualifies or conflicts with a provision of the Trust Indenture
Act that is required under such Act to be a part of and govern this Indenture, the latter provision
shall control. If any provision of this Indenture modifies or excludes any provision of the Trust
Indenture Act that may be so modified or excluded, the latter provision shall be deemed to apply to
this Indenture as so modified or to be excluded, as the case may be.

	 	 	SECTION 108. Effect of Headings and Table of Contents.

The Article and Section headings herein and the Table of Contents are for convenience only and
shall not affect the construction hereof.

	 	 	SECTION 109. Successors and Assigns.

All covenants and agreements in this Indenture by the Company shall bind its successors and
assigns, whether so expressed or not.

	 	 	SECTION 110. Separability Clause.

In case any provision in this Indenture or in the Securities shall be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.

	 	 	SECTION 111. Benefits of Indenture.

Nothing in this Indenture or in the Securities, express or implied, shall give to any Person,
other than the parties hereto and their successors hereunder and the Holders of Securities, any
benefit or any legal or equitable right, remedy or claim under this Indenture.

	 	 	SECTION 112. Governing Law.

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

	 	 	SECTION 113. Legal Holidays.

In any case where any Interest Payment Date, Fundamental Change Repurchase Date, Stated
Maturity, or the last date on which a Holder has the right to convert his Securities, shall not be
a Business Day, then (notwithstanding any other provision of this Indenture or of the Securities)
payment of interest or principal or conversion of the Securities need not be made on such date, but
may be made on the next succeeding Business Day with the same force and effect as if made on the
Interest Payment Date, Fundamental Change Repurchase Date, the Stated Maturity, or on such last day
for conversion, provided that no interest shall accrue for the period from and after such
Interest Payment Date, Fundamental Change Repurchase Date or Stated Maturity, as the case may be.

	 	 	SECTION 114. Indenture and Securities Solely Corporate Obligations.

None of the Company’s past, present or future directors, officers, employees or stockholders,
as such, shall have any liability for any of the Company’s obligations under this Indenture or the
Securities or for any claim based on, or in respect or by reason of, such obligations or their
creation. By accepting a Security, each Holder waives and releases all such liability.

This waiver and release is part of the consideration for the issuance of the Securities.

	 	 	SECTION 115. Indenture May be Executed in Counterparts.

This Indenture may be executed in any number of counterparts, each of which shall be an
original, but such counterparts shall together constitute one and the same instrument.

	 	 	SECTION 116. Acceptance of Trust.

Wells Fargo Bank, N.A., the Trustee named herein, hereby accepts the trusts in this Indenture
declared and provided, upon the terms and conditions set forth herein.

ARTICLE TWO

Security Forms

	 	 	SECTION 201. Forms Generally.

The Securities and the Trustee’s certificates of authentication shall be in substantially the
forms set forth in this Article, with such appropriate insertions, omissions, substitutions and
other variations as are required or permitted by this Indenture, and may have such letters, numbers
or other marks of identification and such legends or endorsements placed thereon as may be required
to comply with the rules of any securities exchange or any depositary therefore or as may,
consistently herewith, be determined by the officers executing such Securities, as evidenced by
their execution of the Securities.

Notices of Conversion shall be in substantially the form set forth in Section 205.

The definitive Securities shall be printed, lithographed or engraved or produced by any
combination of these methods on steel engraved borders or may be produced in any other manner
permitted by the rules of any securities exchange on which the Securities may be listed, all as
determined by the officers executing such Securities, as evidenced by their execution of such
Securities.

	 	 	SECTION 202. Form of Face of Security.

USEC Inc.

3.0% Convertible Senior Note due 2014

No.      $

CUSIP No. 90333EAC2

ISIN No. US90333EAC21

USEC Inc., a corporation duly organized and existing under the laws of the State of Delaware
(herein called the “Company”, which term includes any successor Person under the Indenture
hereinafter referred to), for value received, hereby promises to pay to      , or
registered assigns, the principal sum [of      Dollars] [IF THIS NOTE IS A GLOBAL
SECURITY, THEN INSERT — set forth on the Principal Schedule attached to this Security] on October
1, 2014, and to pay interest thereon from September 28, 2007 or from the most recent Interest
Payment Date to which interest has been paid or duly provided for to but excluding the next
Interest Payment Date, semi-annually on April 1 and October 1 in each year, commencing April 1,
2008, at the rate of 3.0% per annum, until the principal hereof is paid or made available for
payment. The interest so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security
(or one or more Predecessor Securities) is registered at the close of business on the Regular
Record Date for such interest, which shall be the March 15 or September 15 (whether or not a
Business Day), as the case may be, next preceding such Interest Payment Date. Any such interest
not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on
such Regular Record Date and may either be paid to the Person in whose name this Security (or one
or more Predecessor Securities) is registered at the close of business on a Special Record Date for
the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to
Holders of Securities not less than 10 days prior to such Special Record Date, or be paid at any
time in any other lawful manner not inconsistent with the requirements of any securities exchange
on which the Securities may be listed, and upon such notice as may be required by such exchange,
all as more fully provided in said Indenture. Payment of the principal of and interest on this
Security will be made at the office or agency of the Company maintained for that purpose, which
shall initially be the office of Wells Fargo Bank N.A., Corporate Trust Services, 625 Marquette
Avenue, Minneapolis, Minnesota, 55479, in such coin or currency of the United States of America as
at the time of payment is legal tender for payment of public and private debts; provided,
however, that at the option of the Company payment of interest may be made by check mailed
to the address of the Person entitled thereto as such address shall appear in the Security
Register.

Reference is hereby made to the further provisions of this Security set forth on the reverse
hereof, which further provisions shall for all purposes have the same effect as if set forth at
this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to
on the reverse hereof by manual signature, this Security shall not be entitled to any benefit under
the Indenture or be valid or obligatory for any purpose.

IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed

Dated:

USEC INC.

By:     

Name:

Title:

	 	 	SECTION 203. Form of Reverse of Security.

This Security is one of a duly authorized issue of Securities of the Company designated as its
3.0% Convertible Senior Notes due 2014 (herein called the “Initial Securities”), initially limited
in aggregate principal amount to $575,000,000, issued and to be issued under an Indenture, dated as
of September 28, 2007 (herein called the “Indenture”), between the Company and Wells Fargo
Bank, N.A., as Trustee (herein called the “Trustee”, which term includes any

successor trustee under the Indenture), to which Indenture and all indentures supplemental thereto
reference is hereby made for a statement of the respective rights, limitations of rights, duties
and immunities thereunder of the Company, the Trustee and the Holders of the Securities and of the
terms upon which the Securities are, and are to be, authenticated and delivered. The Company may
from time to time, without notice to or the consent of the Holders of the Securities, create and
issue further Securities (the “Additional Securities”, and together with the Initial Securities,
the “Securities”) having the same terms and ranking equally and ratably with the Initial
Securities, as part of one series, in all respects and with the same CUSIP number as the Initial
Securities, or in all respects except for payment of interest accruing prior to the Issue Date of
such Initial Securities. Any Additional Securities shall be consolidated and form a single series
with the Initial Securities and shall have the same terms as to status, redemption, and otherwise
as the Initial Securities; provided that the Company shall not create or issue such Additional
Securities unless (a) underwriters of the Additional Securities sell a “substantial portion” of the
Additional Securities (within the meaning of Treasury Regulation Section 1.1273-2(a)) to persons
other than “bond houses, brokers or similar persons” (within the meaning of Treasury Regulation
Section 1.1273-2(f)); (b) the price at which such underwriters resell any such Additional
Securities exceeds (i) the principal amount of such Additional Securities minus (ii) (A) 1/4 of 1%
of the principal amount of such Additional Securities, multiplied by (B) the number of full,
complete years to maturity of such Additional Securities; and (c) the Initial Securities were
issued with no more than a de minimis amount of original issue discount for U.S. federal income tax
purposes, as defined in Section 1273 of the Internal Revenue Code of 1986, as amended, and the
Treasury regulations promulgated thereunder. Any Additional Securities may be issued pursuant to
authorization provided by a resolution of the Board of Directors of the Company, a supplement to
the Indenture, or under an Officer’s Certificate pursuant to the Indenture. No Additional
Securities may be issued if an Event of Default has occurred and is continuing with respect to the
Initial Securities.

In any case where the due date for the payment of the principal of or interest on any Security
or the last day on which a Holder of a Security has a right to convert his Security shall be, at
any Place of Payment or Place of Conversion, as the case may be, a day on which banking
institutions at such Place of Payment or Place of Conversion are authorized or obligated by law or
executive order to close, then payment of principal, interest or delivery for conversion of such
Security need not be made on or by such date at such place but may be made on or by the next
succeeding day at such place which is not a day on which banking institutions are authorized or
obligated by law, regulation or executive order to close, with the same force and effect as if made
on the date for such payment or the date fixed for redemption or repurchase, or by such last day
for conversion, and no interest shall accrue on the amount so payable for the period after such
date.

Subject to the provisions of the Indenture, upon the occurrence of a Fundamental Change, the
Holder has the right, at such Holder’s option, to require the Company to repurchase all of such
Holder’s Securities or any portion thereof (in principal amounts of $1,000 or integral multiples
thereof) on the Fundamental Change Repurchase Date at a price equal to 100% of the principal amount
of the Securities such Holder elects to require the Company to repurchase, together with accrued
and unpaid interest to but excluding the Fundamental Change Repurchase Date, unless such
Fundamental Change Repurchase Date falls after a Regular Record Date and on or prior to the
corresponding Interest Payment Date, in which case the Company shall instead pay the full amount of
accrued and unpaid interest payable on such Interest Payment Date to the Holder of record at the
close of business on the corresponding Regular Record Date. The Company or, at the written request
of the Company, the Trustee shall mail to all Holders of record of the Securities a notice of the
occurrence of a Fundamental Change and of the repurchase right arising as a result thereof after
the occurrence of any Fundamental Change, but on or before the 10th calendar day following such
occurrence.

Subject to and upon compliance with the provisions of the Indenture, the Holder of this
Security is entitled, at his option, on or after August 1, 2014, or earlier upon the occurrence of
certain conditions specified in the Indenture, and prior to the close of business on the Scheduled
Trading Day immediately preceding the Maturity Date, to convert this Security (or any portion of
the principal amount hereof which is $1,000 or an integral multiple thereof), at the principal
amount hereof, or of such portion, into fully paid and non-assessable shares (calculated as to each
conversion to the nearest 1/100 of a share) of Common Stock of the Company at the Conversion Rate
specified in the Indenture, by surrender of this Security together with a Notice of Conversion, a
form of which is set forth in Section 205, as provided in the Indenture and this Note, duly
endorsed or assigned to the Company or in blank, to the Company at its office or agency, which
shall be initially Wells Fargo Bank N.A., Corporate Trust Services, 625 Marquette Avenue,
Minneapolis, Minnesota, 55479, and, unless the shares of Common Stock issuable on conversion are to
be issued in the same name as this Note, duly endorsed by, or accompanied by instruments of
transfer in form satisfactory to the Company or its agent duly executed by, the Holder or by his
duly authorized attorney, or if less than the entire principal amount hereof is to be converted,
the portion hereof to be converted, and, in case such surrender shall be made during the period
from the close of business on any Regular Record Date next preceding any Interest Payment Date to
the opening of business on such Interest Payment Date, also accompanied by payment in dollars of an
amount equal to the interest payable on such Interest Payment Date on the principal amount of this
Security then being converted. Subject to the aforesaid requirement for payment and, in the case
of a conversion after the Regular Record Date next preceding any Interest Payment Date and on or
before such Interest Payment Date, to the right of the Holder of this Security (or any Predecessor
Security) of record at such Regular Record Date to receive an installment of interest (with certain
exceptions provided in the Indenture), no payment or adjustment is to be made on conversion for
interest accrued hereon or for dividends on the Common Stock issued on conversion. No fractions of
shares or scrip representing fractions of shares will be issued on conversion, but instead of any
fractional interest the Company shall pay a cash adjustment as provided in the Indenture. The
conversion rate is subject to adjustment as provided in the Indenture. In addition, the Indenture
provides that in case of certain consolidations or mergers to which the Company is a party or the
transfer of substantially all of the assets of the Company, the Indenture shall be amended, without
the consent of any Holders of Securities, so that this Security, if then outstanding, will be
convertible thereafter, during the period this Security shall be convertible as specified above, by
reference to the kind and amount of cash, securities and other property or assets that a holder of
a number of shares of Common Stock equal to the Conversion Rate immediately prior to such
transaction would have owned or been entitled to receive.

No sinking fund is provided for the Securities and the Securities are not subject to
redemption at the option of the Company.

In the event of conversion of this Security in part only, a new Security or Securities for
the unconverted portion hereof will be issued in the name of the Holder hereof upon the
cancellation hereof.

If an Event of Default shall occur and be continuing, the principal of all the Securities may
be declared due and payable in the manner and with the effect provided in the Indenture.

The Indenture permits, with certain exceptions as therein provided, the amendment thereof and
the modification of the rights and obligations of the Company and the rights of the Holders of the
Securities under the Indenture at any time by the Company and the Trustee with the consent of the
Holders of at least a majority in aggregate principal amount of the Securities at the time
Outstanding. The Indenture also contains provisions permitting the Holders of specified
percentages in aggregate principal amount of the Securities at the time Outstanding, on behalf of
the Holders of all the Securities, to waive compliance by the Company with certain provisions of
the Indenture and certain past defaults under the Indenture and their consequences. Any such
consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder
and upon all future Holders of this Security and of any Security issued upon the registration of
transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent
or waiver is made upon this Security.

No reference herein to the Indenture and no provision of this Security or of the Indenture
shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay
the principal of and interest on this Security at the times, place and rate, and in the coin or
currency, herein prescribed or to convert this Security as provided in the Indenture.

As provided in the Indenture and subject to certain limitations therein set forth, the
transfer of this Security is registrable in the Security Register, upon surrender of this Security
for registration of transfer at the office or agency of the Company in any place where the
principal of and any premium and interest on this Security are payable, duly endorsed by, or
accompanied by a written instrument of transfer in form satisfactory to the Company and the
Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing,
and thereupon one or more new Securities, of authorized denominations and for the same aggregate
principal amount, will be issued to the designated transferee or transferees.

The Securities are issuable only in registered form without coupons in denominations of $1,000
and any integral multiple thereof. As provided in the Indenture and subject to certain limitations
therein set forth, Securities are exchangeable for a like aggregate principal amount of Securities
of a different authorized denomination, provided that such denomination is a minimum of $1,000 or
an integral multiple thereof, as requested by the Holder surrendering the same.

No service charge shall be made for any such registration of transfer or exchange, but the
Company may require payment of a sum sufficient to cover any tax or other governmental charge
payable in connection therewith.

Prior to due presentment of this Security for registration of transfer, the Company, the
Trustee and any agent of the Company or the Trustee may treat the Person in whose name this
Security is registered as the owner hereof for all purposes, whether or not this Security be
overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the
contrary.

THE INDENTURE AND THIS SECURITY SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
OF THE STATE OF NEW YORK.

All terms used in this Security which are defined in the Indenture shall have the meanings
assigned to them in the Indenture.

[INCLUDE IN GLOBAL SECURITIES ONLY]

PRINCIPAL SCHEDULE

USEC INC.

3.0% Convertible Senior Notes due 2014

No.      

The initial principal amount of this Global Security is $575,000,000. The following decreases
or increases in this Global Security have been made:

	 	 	 	 	 	 	 
	Date of decrease or

increase

	 	Amount of decrease

in principal amount

of this Global

Security
	 	Amount of increase

in principal amount

of this Global

Security
	 	Principal amount of

this Global

Security following

such increase or

decrease
	 

	 	 
	 	 
	 	 

	 	 	SECTION 204. Form of Legend for Global Securities

Unless otherwise specified as contemplated by Section 301 for the Securities evidenced
thereby, every Global Security authenticated and delivered hereunder shall bear a legend in
substantially the following form:

THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND
IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED
IN WHOLE OR IN PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART
MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE THEREOF,
EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

	 	 	SECTION 205. Form of Notice of Conversion

Conversion notices shall be in substantially the following form:

NOTICE OF CONVERSION

The undersigned Holder of this Security hereby irrevocably exercises the option to convert
this Security, or any portion of the principal amount hereof (which is U.S. $1,000 or an integral
multiple of U.S. $1,000 in excess thereof, provided that the unconverted portion of such principal
amount is U.S. $1,000 or any integral multiple of U.S. $1,000 in excess thereof) below designated,
into shares of Common Stock or Reference Property, as applicable in accordance with the terms of
the Indenture referred to in this Security, and directs that such shares, if any, together with a
check in payment for any fractional share and any Securities representing any unconverted principal
amount hereof, be delivered to and be registered in the name of the undersigned unless a different
name has been indicated below. If shares of Common Stock, Reference Property or Securities are to
be registered in the name of a Person other than the undersigned, the undersigned shall pay all
transfer taxes payable with respect thereto.

Dated:     Signature(s):     

If shares or Securities are to be registered in the name of a Person other than the Holder,
please print such Person’s name and address:

     

(Name)

     

     

(Address)

     

Social Security or other

Identification Number, if any

If only a portion of the Securities are to be converted, please indicate:

1. Principal amount to be converted: U.S. $      

2. Principal amount and denomination of Securities representing unconverted principal amount to be
issued:

Amount: U.S. $     Denominations: U.S. $     

(U.S. $1,000 or any integral multiple of U.S. $1,000 in excess thereof, provided that the
unconverted portion of such principal amount is U.S. $1,000 or any integral multiple of U.S. $1,000
in excess thereof)

	 	 	SECTION 206. Form of Assignment.

ASSIGNMENT

For value received,      hereby sell(s), assign(s) and transfer(s) unto
     (Please insert Social Security or other identifying number of assignee) the within
Security, and hereby irrevocably constitutes and appoints      as attorney to
transfer the said Security on the books of the Company, with full power of substitution in the
premises.

Dated:     Signature(s):     

Signature(s) must be guaranteed by an Eligible Guarantor Institution with membership in an
approved signature guarantee program pursuant to Rule 17Ad-15 under the Securities Exchange Act of
1934.

     

Signature Guaranteed

	 	 	SECTION 207. Form of Trustee’s Certificate of Authentication.

This is one of the Securities referred to in the within-mentioned Indenture.

Dated: __________________________

WELLS FARGO BANK, N.A., as Trustee

By: ________________________________

Authorized Officer

	 	 	SECTION 208. Form of Fundamental Change Repurchase Notice.

To: USEC Inc.

The undersigned registered owner of this Security hereby acknowledges receipt of a notice from
USEC Inc. (the “Company”) as to the occurrence of a Fundamental Change with respect to the Company
and hereby directs the Company to pay, or cause the Trustee to pay,      an amount in
cash equal to 100% of the entire principal amount, or the portion thereof (which is $1,000
principal amount or an integral multiple thereof) below designated, to be repurchased plus
interest accrued to, but excluding, the Fundamental Change Repurchase Date, except as provided in
the Indenture.

Dated:      

     

Signature

Principal amount to be repurchased (at least $1,000 or an integral multiple of $1,000 in excess
thereof):      

Remaining principal amount following such repurchase:      

By:      

Authorized signatory

ARTICLE THREE

The Securities

	 	 	SECTION 301. Title and Terms; Principal and Interest.

The aggregate principal amount of Initial Securities which may be authenticated and delivered
under this Indenture is limited to $575,000,000 and the aggregate amount of Additional Securities
is unlimited, except for Securities authenticated and delivered upon registration of transfer of,
or in exchange for, or in lieu of, other Securities pursuant to Section 304, 305, 306, 906 or 1202.

The Initial Securities and the Additional Securities, if any, shall be known and designated as
the “3.0% Convertible Senior Notes due 2014” of the Company.

The Securities shall mature on October 1, 2014,

The Securities shall bear interest at the rate of 3.0% per annum, from September 28, 2007 or
from the most recent Interest Payment Date to which interest has been paid or duly provided for, as
the case may be, payable semi-annually in arrears on April 1 and October 1, commencing April 1,
2008, until the principal thereof is paid or made available for payment.

If any Interest Payment Date falls on a day that is not a Business Day, the interest payment
due on such Interest Payment Date shall be paid on the next succeeding Business Day and no interest
on such payment will accrue for the period from the Interest Payment Date to such next succeeding
Business Day. If the Stated Maturity date falls on a day that is not a Business Day, the required
payment of interest, if any, and principal (and Additional Interest, if any), shall be postponed to
the next succeeding Business Day and no interest on such payment will accrue for the period from
and after the Stated Maturity date to such next succeeding Business Day. If a Fundamental Change
Repurchase Date would fall on a day that is not a Business Day, the Company will purchase the
Securities tendered for purchase on the next succeeding Business Day and no interest or Additional
Interest on such Securities will accrue for the period from and after the earlier Fundamental
Change Repurchase Date to such next succeeding Business Day. The Company will pay the Fundamental
Change Repurchase Price promptly following the later of (i) such next succeeding Business Day or
(ii) the time of book entry transfer or the delivery of the notes as set forth in Section 1101
hereof.

A Holder of any Security after 5:00 p.m., New York City time, on a Regular Record Date shall
be entitled to receive interest (including any Additional Interest), on such Security on the
corresponding interest payment date. Holders of Securities at 5:00 p.m., New York City time, on a
Regular Record Date will receive payment of interest (including any Additional Interest) payable on
the corresponding Interest Payment Date notwithstanding the conversion of such Securities at any
time after 5:00 p.m., New York City time on such Regular Record Date. Securities surrendered for
conversion during the period after 5:00 p.m., New York City time, on any Regular Record Date to
9:00 a.m., New York City time, on the corresponding Interest Payment Date must be accompanied by
payment of an amount equal to the interest (including any Additional Interest) that the Holder is
to receive on the Securities. Notwithstanding the foregoing, no such payment of interest
(including any Additional Interest) need be made by any converting Holder (i) for conversions with
a Conversion Date on or after August 1, 2014, (ii) if the Company has specified a Fundamental
Change Repurchase Date that is after a Regular Record Date and on or prior to the corresponding
interest payment date, or (iii) to the extent of any overdue interest (including any overdue
Additional Interest) existing at the time of conversion of such Security. Except where Securities
surrendered for conversion must be accompanied by payment as described above, no interest or
Additional Interest on converted Securities will be payable by the Company on any interest payment
date subsequent to the Conversion Date and delivery of the cash and shares of Common Stock, if
applicable, pursuant to Article Twelve hereunder, together with any cash payment for any fractional
share, upon conversion will be deemed to satisfy the Company’s obligation to pay the principal
amount of the Securities and accrued and unpaid interest and Additional Interest, if any, to, but
not including, the related Conversion Date.

Principal of and interest on, Global Securities shall be payable to DTC in immediately
available funds.

Principal on definitive Securities shall be payable at the office or agency of the Company
maintained for such purpose, initially the agency of the Trustee at 625 Marquette Ave.,
Minneapolis, Minnesota 55479 (such office and city in which the Paying Agent is located being
herein after called the “Place of Payment”). Interest, on definitive Securities will be payable
(i) to each Holder of Securities having an aggregate principal amount of $5,000,000 or less, by
check mailed to such Holder and (ii) to each Holder of Securities having an aggregate principal
amount of more than $5,000,000, either by check mailed to such Holder or, upon application by such
Holder to the Registrar not later than the relevant Regular Record Date, by wire transfer in
immediately available funds to that Holder’s account within the United States, which application
shall remain in effect until the Holder notifies, in writing, the Registrar to the contrary.

The Securities shall be convertible as provided in Article Twelve (any city in which the
Conversion Agent is located being herein after called the “Place of Conversion”).

	 	 	SECTION 302. Denominations.

The Securities shall be issuable only in registered form without coupons and only in
denominations of $1,000 and any integral multiple thereof.

	 	 	SECTION 303. Global Securities; Non-Global Securities; Book-entry Provisions.

The Securities may be issued in Global or Non-Global (Definitive) Form as provided in this
Indenture.

(a) Global Securities

(i) Each Global Security authenticated under this Indenture shall be registered in the
name of, and delivered to, Cede & Co., as nominee of DTC (the “Depositary”). Each such
Global Security shall constitute a single Security for all purposes of this Indenture.

(ii) Except for exchanges of Global Securities for definitive, non-Global Securities
at the sole discretion of the Company, no Global Securities may be exchanged in whole or in
part for Securities registered, and no transfer of a Securities in whole or in part may be
registered, in the name of any Person other than the Depositary for such Global Security or
a nominee thereof unless (A) such Depositary (i) has notified the Company that it is
unwilling or unable to continue as Depositary for such Global Security or (ii) has ceased
to be a clearing agency registered as such under the Exchange Act or announces an intention
permanently to cease business or does in fact do so or (B) there shall have occurred and be
continuing an Event of Default with respect to such Global Security. In such event, if a
successor Depositary for such Global Security is not appointed by the Company within 90
calendar days after the Company receives such notice or becomes aware of such
ineligibility, the Company shall execute, and the Trustee, upon receipt of an Officers’
Certificate directing the authentication and delivery of non-Global Securities, shall
authenticate and deliver, non-Global Securities, in any authorized denominations in an
aggregate principal amount equal to the principal amount of such Global Security in
exchange for such Global Security.

(iii) If any Global Security is to be exchanged for other Securities or canceled in
whole, it shall be surrendered by or on behalf of the Depositary or its nominee to the
Trustee, as Registrar, for exchange or cancellation, as provided in this Article. If any
Global Security is to be exchanged for other Securities or canceled in part, or if another
Security is to be exchanged in whole or in part for a beneficial interest in any Global
Security, in each case, as provided in Article Two of this Indenture, then either (A) such
Global Security shall be so surrendered for exchange or cancellation, as provided in this
Article, or (B) the principal amount thereof shall be reduced or increased by an amount
equal to the portion thereof to be so exchanged or canceled, or equal to the principal
amount of such other Security to be so exchanged for a beneficial interest therein, as the
case may be, by means of an appropriate adjustment made on the records of the Trustee, as
Registrar, whereupon the Trustee, in accordance with the Applicable Procedures, shall
instruct the Depositary or its authorized representative to make a corresponding adjustment
to its records. Upon any such surrender or adjustment of a Global Security, the Trustee
shall, subject to this Article, authenticate and deliver any Securities issuable in
exchange for such Global Security (or any portion thereof) to or upon the order of, and
registered in such names as may be directed by, the Depositary or its authorized
representative. The Trustee shall be entitled to receive from the Depositary the names,
addresses and tax identification numbers of the Persons in whose name the Securities are to
be registered prior to such authentication and delivery. Upon the request of the Trustee in
connection with the occurrence of any of the events specified in the preceding paragraph,
the Company shall promptly make available to the Trustee a reasonable supply of Securities
that are not in the form of Global Securities. The Trustee shall be entitled to rely upon
any order, direction or request of the Depositary or its authorized representative which is
given or made pursuant to this Article if such order, direction or request is given or made
in accordance with the Applicable Procedures (to the extent such procedures are applicable
to such direction or request).

(iv) Every Security authenticated and delivered upon registration of transfer of, or
in exchange for or in lieu of, a Global Security or any portion thereof, whether pursuant
to this Article or otherwise, shall be authenticated and delivered in the form of, and
shall be, a registered Global Security, unless such Security is registered in the name of a
Person other than the Depositary for such Global Security or a nominee thereof, in which
case such Security shall be authenticated and delivered in accordance with clause (b) of
this Section 303.

(v) The Depositary or its nominee, as registered owner of a Global Security, shall be
the Holder of such Global Security for all purposes under this Indenture and the
Securities, and owners of beneficial interests in a Global Security shall hold such
interests pursuant to the Applicable Procedures. Accordingly, any such owner’s beneficial
interest in a Global Security shall be shown only on, and the transfer of such interest
shall be effected only through, records maintained by the Depositary or its nominee or its
Agent Members and such owners of beneficial interests in a Global Security shall not be
considered the owners or holders thereof.

(b) Non-Global Securities. Securities issued upon the events described in Section 303(a)(ii)
shall be in definitive, fully registered form, without interest coupons.

	 	 	SECTION 304. Execution, Authentication, Delivery and Dating.

The Securities shall be executed on behalf of the Company by its Chairman of the Board, Vice
Chairman of the Board, Chief Executive Officer, Chief Financial Officer, President or one of its
Vice Presidents, Treasurer or Assistant Treasurer. The signature of any of these officers on the
Securities may be manual or facsimile.

Securities bearing the manual or facsimile signatures of individuals who were at any time the
proper officers of the Company shall bind the Company, notwithstanding that such individuals or any
of them have ceased to hold such offices prior to the authentication and delivery of such
Securities or did not hold such offices at the date of such Securities.

At any time and from time to time after the execution and delivery of this Indenture, the
Company may deliver Securities executed by the Company to the Trustee for authentication, together
with a Company Order for the authentication and delivery of such Securities; and the Trustee in
accordance with such Company Order shall authenticate and deliver such Securities as in this
Indenture provided and not otherwise.

Each Security shall be dated the date of its authentication.

No Security shall be entitled to any benefit under this Indenture or be valid or obligatory
for any purpose unless there appears on such Security a certificate of authentication substantially
in the form provided for herein executed by the Trustee by manual signature, and such certificate
upon any Security shall be conclusive evidence, and the only evidence, that such Security has been
duly authenticated and delivered hereunder. Notwithstanding the foregoing, if any Security shall
have been authenticated and delivered hereunder but never issued and sold by the Company, and the
Company shall deliver such Security to the Trustee for cancellation as provided in Section 310, for
all purposes of this Indenture such Security shall be deemed never to have been authenticated and
delivered hereunder and shall never be entitled to the benefits of this Indenture.

The Company may, subject to Article Ten of this Indenture and applicable law, issue under this
Indenture Additional Securities; provided, however, that the Company may not issue
Additional Securities if an Event of Default with respect to any Outstanding Securities shall have
occurred and be continuing at the time of such issuance. All Securities issued under this
Indenture shall be treated as a single class for all purposes under this Indenture; provided
further that the Company shall not issue such Additional Securities unless (a) underwriters sell a
“substantial portion” of the Additional Securities (within the meaning of Treasury Regulation
Section 1.1273-2(a)) to persons other than “bond houses, brokers or similar persons” (within the
meaning of Treasury Regulation Section 1.1273-2(f)); (b) the price at which such underwriters
resell any such Additional Securities exceeds (i) the principal amount of such Additional
Securities minus (ii) (A) 1/4 of 1% of the principal amount of such Additional Securities,
multiplied by (B) the number of full, complete years to maturity of such Additional Securities; and
(c) the Initial Securities were issued with no more than a de minimis amount of original issue
discount for U.S. federal income tax purposes, as defined in Section 1273 of the Internal Revenue
Code of 1986, as amended, and the Treasury regulations promulgated thereunder.

	 	 	SECTION 305. Temporary Securities.

Pending the preparation of definitive Securities, the Company may execute, and upon Company
Order the Trustee shall authenticate and deliver, temporary Securities which are printed,
lithographed, typewritten, mimeographed or otherwise produced, in any authorized denomination,
substantially of the tenor of the definitive Securities in lieu of which they are issued and with
such appropriate insertions, omissions, substitutions and other variations as the officers
executing such Securities may determine, as evidenced by their execution of such Securities.

If temporary Securities are issued, the Company will cause definitive Securities to be
prepared without unreasonable delay. After the preparation of definitive Securities, the temporary
Securities shall be exchangeable for definitive Securities upon surrender of the temporary
Securities at any office or agency of the Company designated pursuant to Section 1002, without
charge to the Holder. Upon surrender for cancellation of any one or more temporary Securities the
Company shall execute and the Trustee shall authenticate and deliver in exchange therefor a like
principal amount of definitive Securities of authorized denominations. Until so exchanged the
temporary Securities shall in all respects be entitled to the same benefits under this Indenture as
definitive Securities.

	 	 	SECTION 306. Registrar, Registration of Transfer and Exchange; Paying Agent.

(a) Registrar. The Company shall cause to be kept at the Corporate Trust Office of the
Trustee a register (the register maintained in such office and in any other office or agency
designated pursuant to Section 1002 being herein sometimes collectively referred to as the
“Security Register”) in which, subject to such reasonable regulations as it may prescribe, the
Company shall provide for the registration of Securities and for the transfers or exchange of
Securities. Such Security Register shall distinguish between Initial Securities and Additional
Securities. The Trustee is hereby appointed “Security Registrar” for the purpose of registering
Securities and transfers and exchanges of Securities as herein provided. The Company may change
the Security Registrar without notice to any Holder. The Company or any of its Subsidiaries may act
as Security Registrar.

Upon surrender for registration of transfer of any Security at an office or agency of the
Company designated pursuant to Section 1002 for such purpose, the Company shall execute, and the
Trustee shall authenticate and deliver, in the name of the designated transferee or transferees,
one or more new Securities of any authorized denomination, provided that such denomination is a
minimum of $1,000 or an integral multiple thereof, and of a like aggregate principal amount.

At the option of the Holder, Securities may be exchanged for other Securities of any
authorized denominations and of a like tenor and aggregate principal amount, upon surrender of the
Securities to be exchanged at such office or agency. Whenever any Securities are so surrendered
for exchange, the Company shall execute, and the Trustee shall authenticate and deliver, the
Securities which the Holder making the exchange is entitled to receive.

All Securities issued upon any registration of transfer or exchange of Securities shall be the
valid obligations of the Company, evidencing the same debt, and entitled to the same benefits under
this Indenture, as the Securities surrendered upon such registration of transfer or exchange.

Every Security presented or surrendered for registration of transfer or for exchange shall (if
so required by the Company or the Trustee) be duly endorsed, or be accompanied by a written
instrument of transfer in form satisfactory to the Company and the Security Registrar duly
executed, by the Holder thereof or his attorney duly authorized in writing.

No service charge shall be made for any registration of transfer or exchange of Securities,
but the Company may require payment of a sum sufficient to cover any tax or other governmental
charge that may be imposed in connection with any registration of transfer or exchange of
Securities, other than exchanges pursuant to Section 304, 906 or 1202 not involving any transfer.

(b) Paying Agent. The Company shall maintain an office or agency where Securities may be
presented for payment (the “Paying Agent”). The Company initially appoints the Trustee as Paying
Agent for the Securities. The Company may have one or more additional paying agents and the term
“Paying Agent” shall include any such additional paying agent.

The Company shall enter into an appropriate agency agreement with any Paying Agent not a party
to this Indenture, which shall incorporate the terms of the Trust Indenture Act, except in the case
of a Paying Agent that acts as Paying Agent solely in connection with an offer to purchase the
Securities pursuant to Article Ten of this Indenture. The agreement shall implement the provisions
of this Indenture that relate to such agent. The Company shall notify the Trustee of the name and
address of each such agent. If the Company fails to maintain a Paying Agent, the Trustee shall act
as such and shall be entitled to appropriate compensation therefor pursuant to Section 607. The
Company or any Subsidiaries may act as Paying Agent.

The Company may remove any Paying Agent upon written notice to such Paying Agent and to the
Trustee; provided, however, that no such removal shall become effective until (i)
acceptance of any appointment by a successor as evidenced by an appropriate agreement entered into
by the Company and such successor Paying Agent, as the case may be, and delivered to the Trustee or
(ii) notification to the Trustee that the Trustee or the Company shall serve as Paying Agent until
the appointment of a successor in accordance with clause (i) above. The Paying Agent may resign at
any time upon written notice to the Company and the Trustee.

(c) Paying Agent to Hold Money in Trust. By no later than 11:00 a.m., New York City time, on
the date on which any principal of or interest and Additional Interest, if any, on any Security is
due and payable, the Company shall deposit with the Paying Agent a sum sufficient in immediately
available funds to pay such principal or interest (including any Additional Interest), when due.
The Company shall require each Paying Agent (other than the Trustee) to agree in writing that such
Paying Agent shall hold in trust for the benefit of Security holders or the Trustee all money held
by such Paying Agent for the payment of principal of or interest (including any Additional
Interest), on the Securities and shall notify the Trustee in writing of any default by the Company
in making any such payment. If the Company or a Subsidiary acts as Paying Agent, it shall
segregate the money held by it as Paying Agent and hold it as a separate trust fund. The Company
at any time may require a Paying Agent (other than the Trustee) to pay all money held by it to the
Trustee and to account for any funds disbursed by such Paying Agent. Upon complying with this
Section 306, the Paying Agent (if other than the Company or a Subsidiary) shall have no further
liability for the money delivered to the Trustee. Upon any bankruptcy, reorganization or similar
proceeding with respect to the Company, the Trustee shall serve as Paying Agent for the Securities.

(d) Custodian. The Company hereby appoints the Trustee as Custodian with respect to any
Global Securities.

	 	 	SECTION 307. Mutilated, Destroyed, Lost and Stolen Securities.

If any mutilated Security is surrendered to the Trustee, the Company shall execute and the
Trustee shall authenticate and deliver in exchange therefor a new Security of like tenor and
principal amount and bearing a number not contemporaneously outstanding.

If there shall be delivered to the Company and the Trustee (i) evidence to their satisfaction
of the destruction, loss or theft of any Security and (ii) such security or indemnity as may be
required by them to save each of them and any agent of either of them harmless, then, in the
absence of notice to the Company or the Trustee that such Security has been acquired by a bona fide
purchaser, the Company shall execute and the Trustee shall authenticate and deliver, in lieu of any
such destroyed, lost or stolen Security, a new Security of like tenor and principal amount and
bearing a number not contemporaneously outstanding.

In case any such mutilated, destroyed, lost or stolen Security has become or is about to
become due and payable, the Company in its discretion may, instead of issuing a new Security, pay
such Security.

Upon the issuance of any new Security under this Section, the Company may require the payment
of a sum sufficient to cover any tax or other governmental charge that may be imposed in relation
thereto and any other expenses (including the fees and expenses of the Trustee) connected
therewith.

Every new Security issued pursuant to this Section in lieu of any destroyed, lost or stolen
Security shall constitute an original additional contractual obligation of the Company, whether or
not the destroyed, lost or stolen Security shall be at any time enforceable by anyone, and shall be
entitled to all the benefits of this Indenture equally and proportionately with any and all other
Securities duly issued hereunder.

The provisions of this Section are exclusive and shall preclude (to the extent lawful) all
other rights and remedies with respect to the replacement or payment of mutilated, destroyed, lost
or stolen Securities.

	 	 	SECTION 308. Payment of Interest; Interest Rights Preserved.

Interest on any Security which is payable, and is punctually paid or duly provided for, on any
Interest Payment Date shall be paid to the Person in whose name that Security (or one or more
Predecessor Securities) is registered at the close of business on the Regular Record Date for such
interest.

In the case of Securities represented by a Global Security registered in the name of or held
by a Depository or its nominee, payment of principal, premium, if any, and interest, if any, will
be made to the Depository or its nominee, as the case may be, as the registered owner or Holder of
such Global Security. None of the Company, the Trustee and the Paying Agent, any Authenticating
Agent or the Security Registrar for such Securities will have any responsibility or liability for
any aspect of the records relating to or payments made on account of a beneficial ownership
interest in a Global Security or maintaining, supervising or reviewing any records relating to such
beneficial ownership interests.

Any interest on any Security which is payable, but is not punctually paid or duly provided
for, on any Interest Payment Date (herein called “Defaulted Interest”) shall forthwith cease to be
payable to the Holder on the relevant Regular Record Date by virtue of having been such Holder, and
such Defaulted Interest may be paid by the Company, at its election in each case, as provided in
Clause (1) or (2) below:

(1) The Company may elect to make payment of any Defaulted Interest to the Persons in
whose names the Securities (or their respective Predecessor Securities) are registered at
the close of business on a Special Record Date for the payment of such Defaulted Interest,
which shall be fixed in the following manner. The Company shall notify the Trustee in
writing of the amount of Defaulted Interest proposed to be paid on each Security and the
date of the proposed payment, and at the same time the Company shall deposit with the
Trustee an amount of money equal to the aggregate amount proposed to be paid in respect of
such Defaulted Interest or shall make arrangements satisfactory to the Trustee for such
deposit prior to the date of the proposed payment, such money when deposited to be held in
trust for the benefit of the Persons entitled to such Defaulted Interest as in this Clause
provided. Thereupon the Trustee shall fix a Special Record Date for the payment of such
Defaulted Interest which shall be not more than 15 days and not less than 10 days prior to
the date of the proposed payment and not less than 10 days after the receipt by the Trustee
of the notice of the proposed payment. The Trustee shall promptly notify the Company of
such Special Record Date and, in the name and at the expense of the Company, shall cause
notice of the proposed payment of such Defaulted Interest and the Special Record Date
therefor to be mailed, first-class postage prepaid, to each Holder at his address as it
appears in the Security Register, not less than 10 days prior to such Special Record Date.
Notice of the proposed payment of such Defaulted Interest and the Special Record Date
therefor having been so mailed, such Defaulted Interest shall be paid to the Persons in
whose names the Securities (or their respective Predecessor Securities) are registered at
the close of business on such Special Record Date and shall no longer be payable pursuant
to the following Clause (2).

(2) The Company may make payment of any Defaulted Interest in any other lawful manner
not inconsistent with the requirements of any securities exchange on which the Securities
may be listed, and upon such notice as may be required by such exchange, if, after notice
given by the Company to the Trustee of the proposed payment pursuant to this Clause, such
manner of payment shall be deemed practicable by the Trustee.

Subject to the foregoing provisions of this Section, each Security delivered under this
Indenture upon registration of transfer of or in exchange for or in lieu of any other Security
shall carry the rights to interest accrued and unpaid, and to accrue, which were carried by such
other Security.

Subject to the provisions of Article Twelve hereof, in the case of any Security which is
converted after any Regular Record Date and on or prior to the next succeeding Interest Payment
Date (other than any Security whose Maturity is prior to such Interest Payment Date), interest
whose Stated Maturity is on such Interest Payment Date shall be payable on such Interest Payment
Date notwithstanding such conversion, and such interest (whether or not punctually paid or duly
provided for) shall be paid to the Person in whose name that Security (or one or more Predecessor
Securities) is registered at the close of business on such Regular Record Date. Except as
otherwise expressly provided in the immediately preceding sentence or in Article Twelve hereof, in
the case of any Security (or any part thereof) which is converted, interest whose Stated Maturity
is after the date of conversion of such Security (or any part thereof) shall not be payable.

	 	 	SECTION 309. Persons Deemed Owners.

Prior to due presentment of a Security for registration of transfer, the Company, the Trustee
and any agent of the Company or the Trustee may treat the Person in whose name such Security is
registered as the owner of such Security for the purpose of receiving payment of principal of and
(subject to Section 308) interest on such Security and for all other purposes whatsoever, whether
or not such Security be overdue, and neither the Company, the Trustee nor any agent of the Company
or the Trustee shall be affected by notice to the contrary.

In the case of a Global Security, so long as the Depository for such Global Security, or its
nominee, is the registered owner of such Global Security, such Depository or such nominee, as the
case may be, will be considered the sole owner or Holder of the Securities represented by such
Global Security for all purposes under this Indenture. Except as provided in Section 306, owners of
beneficial interests in a Global Security will not be entitled to have Securities that are
represented by such Global Security registered in their names, will not receive or be entitled to
receive physical delivery of such Securities in definitive form and will not be considered the
owners or Holders thereof under this Indenture.

Notwithstanding the foregoing, with respect to any Global Security, nothing herein shall (a)
prevent the Company, the Trustee, or any agent of the Company or the Trustee, from giving effect to
any written certification, proxy or other authorization furnished by a Depository or (b) impair, as
between a Depository and holders of beneficial interest in any Global Security, the operation of
customary practices governing the exercise of the rights of the Depository as Holder of such Global
Security.

	 	 	SECTION 310. Cancellation.

All Securities surrendered for payment, redemption, registration of transfer or exchange or
conversion shall, if surrendered to any Person other than the Trustee, be delivered to the Trustee
and shall be promptly cancelled by it. The Company may at any time deliver to the Trustee for
cancellation any Securities previously authenticated and delivered hereunder which the Company may
have acquired in any manner whatsoever, and may deliver to the Trustee (or to any other Person for
delivery to the trustee) for cancellation any Securities previously authenticated hereunder which
the Company has not issued and sold, and all Securities so delivered shall be promptly cancelled by
the Trustee. No Securities shall be authenticated in lieu of or in exchange for any Securities
cancelled as provided in this Section, except as expressly permitted by this Indenture. All
cancelled Securities held by the Trustee shall be disposed of in accordance with its customary
procedures. Copies of all cancelled Securities shall be provided to the Company by the Trustee,
promptly following cancellation of such Securities.

	 	 	SECTION 311. CUSIP Numbers.

The Company in issuing the Securities may use “CUSIP” numbers (if then generally in use), and,
if so, the Trustee shall use CUSIP numbers in all notices to Holders as a convenience to Holders of
the Securities; provided, that any such notice may state that no representation is made as to the
correctness of such numbers either as printed on the Securities or on such notice and that reliance
may be placed only on the other identification numbers printed on the Securities. The Company will
promptly notify the Trustee in writing of any change in the CUSIP numbers.

	 	 	SECTION 312. Computation of Interest.

Interest on the Securities shall be computed on the basis of a 360-day year of twelve 30-day
months.

	 	 	SECTION 313. Special Record Date.

Any interest on any Security that is payable but not punctually paid or duly provided for on
any Interest Payment Date (“Defaulted Interest”) shall forthwith cease to be payable to the Holder
on the relevant Regular Record Date by virtue of his, her or its having been such a Holder, and
such Defaulted Interest may be paid by the Company, at its election in each case, as provided in
clause (a) or (b) below:

(a) The Company may elect to make payment of any Defaulted Interest to Holders in whose names
the Securities are registered at the close of business on a special record date for the payment of
such Defaulted Interest (a “Special Record Date”), which shall be fixed in the following manner.
The Company shall notify the Trustee in writing of the Defaulted Interest proposed to be paid on
each Security and the date of the proposed payment, and at the same time the Company shall deposit
with the Trustee an amount of money equal to the aggregate amount proposed to be paid in respect of
such Defaulted Interest or shall make arrangements satisfactory to the Trustee for such deposit
prior to the date of the proposed payment, such money when deposited to be held in trust for the
benefit of the Holders entitled to such Defaulted Interest as in this clause provided. Thereupon
the Trustee shall fix a Special Record Date for the payment of such Defaulted Interest which shall
be not more than 15 calendar days and not less than 10 calendar days prior to the date of the
proposed payment and not less than 10 calendar days after the receipt by the Trustee of the notice
of the proposed payment. The Trustee shall promptly notify the Company of such Special Record Date
and, in the name and at the expense of the Company, shall cause notice of the proposed payment of
such Defaulted Interest and the Special Record Date therefor to be mailed, first-class postage
prepaid, to the Holders of the Securities at their addresses as they appear in the Note Register,
or by such other means reasonably acceptable to such Holders, not less than 10 calendar days prior
to such Special Record Date. Notice of the proposed payment of such Defaulted Interest and the
Special Record Date therefor having been mailed as aforesaid, such Defaulted Interest shall be paid
to the Persons in whose names the Securities (or their predecessor Securities) are registered at
the close of business on such Special Record Date and shall no longer be payable pursuant to the
following clause (b).

(b) The Company may make payment of any Defaulted Interest on the Securities in any other
lawful manner not inconsistent with the requirements of any automated quotation system or
securities exchange on which the Securities may be listed, and upon such notice as may be required
by such exchange, if, after notice given by the Company to the Trustee of the proposed payment
pursuant to this clause, such manner of payment shall be deemed practicable by the Trustee.

ARTICLE FOUR

Satisfaction and Discharge

	 	 	SECTION 401. Satisfaction and Discharge of Indenture.

This Indenture shall cease to be of further effect (except as to any surviving rights of
conversion, registration of transfer or exchange of Securities herein expressly provided for), and
the Trustee, on demand of and at the expense of the Company, shall execute proper instruments
acknowledging satisfaction and discharge of this Indenture, when

(1) either

(A) all Securities theretofore authenticated and delivered (other than (i)
Securities which have been destroyed, lost or stolen and which have been replaced
or paid as provided in Section 307 and (ii) Securities for whose payment money has
theretofore been deposited in trust or segregated and held in trust by the Company
and thereafter repaid to the Company or discharged from such trust, as provided in
Section 1003) have been delivered to the Trustee for cancellation; or

(B) all such Securities not theretofore delivered to the Trustee for
cancellation

(i) have become due and payable, or

(ii) will become due and payable at their Stated Maturity within one
year, or

(iii) the Company, in the case of (i) or (ii) above, has deposited or
caused to be deposited with the Trustee as trust funds in trust for the
purpose, lawful money of the United States or U.S. Government Obligations
which through the payment of interest and principal in respect thereof in
accordance with their terms will provide lawful money not later than the
due dates of principal or interest, or any combination thereof in an
amount sufficient to pay and discharge the entire indebtedness on such
Securities not theretofore delivered to the Trustee for cancellation, for
principal (and premium, if any) and interest to the date of such deposit
(in the case of Securities which have become due and payable) or to the
Stated Maturity or Fundamental Change Repurchase Date, as the case may be;

(2) the Company has paid or caused to be paid all other sums payable hereunder by the
Company; and

(3) the Company has delivered to the Trustee an Officers’ Certificate and an Opinion
of Counsel, each stating that all conditions precedent herein provided for relating to the
satisfaction and discharge of this Indenture have been complied with.

Notwithstanding the satisfaction and discharge of this Indenture, the obligations of the Company to
the Trustee under Section 607, the obligations of the Trustee to any Authenticating Agent under
Section 614 and, if money shall have been deposited with the Trustee pursuant to subclause (B) of
Clause (1) of this Section, the obligations of the Trustee under Section 402 and the last paragraph
of Section 1003 shall survive.

	 	 	SECTION 402. Application of Trust Money.

Subject to the provisions of the last paragraph of Section 1003, all funds or U.S. Government
Obligations deposited with the Trustee pursuant to Section 401 shall be held in trust and applied
by it, in accordance with the provisions of the Securities and this Indenture, to the payment,
either directly or through any Paying Agent (including the Company acting as its own Paying Agent)
as the Trustee may determine, to the Persons entitled thereto, of the principal and interest for
whose payment such funds or U.S. Government Obligations have been deposited with the Trustee. Upon
termination of the trust established pursuant to Section 401, all funds and/or U.S. Government
Obligations deposited with the Trustee pursuant to Section 401 (and held by it or any
Paying Agent) for the payment of Securities subsequently converted shall promptly be returned to
the Company upon Company Request.

ARTICLE FIVE

Remedies

	 	 	SECTION 501. Events of Default.

“Event of Default”, wherever used herein, means any one of the following events (whatever the
reason for such Event of Default and whether it shall be voluntary or involuntary or be effected by
operation of law or pursuant to any judgment, decree or order of any court or any order, rule or
regulation of any administrative or governmental body):

(1) default in the payment of any interest upon any Security when it becomes due and
payable, and continuance of such default for a period of 30 days; or

(2) default in the payment of the principal of any Security when due and payable at
its Stated Maturity, upon required repurchase, upon acceleration or otherwise; or

(3) failure by the Company to comply with its obligation to convert the Securities
into shares of Common Stock upon exercise of a Holder’s conversion right, and, in the case
of the Company’s failure to convert the Securities into shares of Common Stock, such
failure continues for five days; or;

(4) failure by the Company to comply with its obligations under Article Eight; or

(5) failure by the Company to issue a Fundamental Change Repurchase Right Notice in
accordance with Section 1101 or comply with its notice requirements under Sections
1201(b)-(d) when due; or

(6) failure by the Company for 60 days after written notice from the Trustee or the
Holders of at least 25% principal amount of the Outstanding Securities has been received by
the Company to comply with any of its other agreements contained in the Securities or
Indenture; or

(7) default by the Company or any Subsidiary of the Company with respect to any
mortgage, agreement or other instrument under which there may be outstanding, or by which
there may be secured or evidenced, any debt for money borrowed in excess of $35,000,000 in
the aggregate of the Company and/or any subsidiary of the Company, whether such debt now
exists or shall hereafter be created, which default shall have resulted (i) in such debt
becoming or being declared due and payable or (ii) from a failure to pay the principal of
any such debt when due and payable at its Stated Maturity, upon required repurchase, upon
declaration or otherwise, and in any such case of (i) or (ii), without such debt having
been paid or discharged within a period of 30 days after the occurrence of such
indebtedness becoming or being declared due and payable or the failure to pay, as the case
may be; or

(8) failure by the Company or any of its Subsidiaries, within 60 days, to pay, bond or
otherwise discharge any judgments or orders for the payment of money the total uninsured
amount of which for the Company or any of its Subsidiaries exceeds in the aggregate
$15,000,000, which are not stayed on appeal; or

(9) the Company or any of its Significant Subsidiaries shall commence a voluntary case
or other proceeding seeking liquidation, reorganization or other relief with respect to
itself or its debts under any bankruptcy, insolvency or other similar law now or hereafter
in effect or seeking the appointment of a trustee, receiver, liquidator, custodian or other
similar official of the Company or any of its Significant Subsidiaries or any substantial
part of its respective property, or shall consent to any such relief or to the appointment
of or taking possession by any such official in an involuntary case or other proceeding
commenced against it, or shall make a general assignment for the benefit of creditors, or
shall fail generally to pay its debts as they become due; or

(10) an involuntary case or other proceeding shall be commenced against the Company or
any of its Significant Subsidiaries seeking liquidation, reorganization or other relief
with respect to it or its debts under any bankruptcy, insolvency or other similar law now
or hereafter in effect or seeking the appointment of a trustee, receiver, liquidator,
custodian or other similar official of the Company or any of its Significant Subsidiaries
or any substantial part of its respective property, and such involuntary case or other
proceeding shall remain undismissed and unstayed for a period of sixty (60) consecutive
calendar days.

	 	 	SECTION 502. Acceleration of Maturity; Rescission and Annulment.

If an Event of Default occurs and is continuing, then and in every such case except as
provided below, the Trustee or the Holders of not less than 25% in principal amount of the
Outstanding Securities may declare the principal of all the Securities to be due and payable
immediately, by a notice in writing to the Company (and to the Trustee if given by Holders), and
upon any such declaration such principal shall become immediately due and payable. However, upon
an Event of Default arising out of 501(9) or (10) (except with respect to any Significant
Subsidiaries) the principal of all the Securities, plus accrued and unpaid interest to the
acceleration date, shall be due and payable immediately without notice from the Trustee or Holders.

Notwithstanding the foregoing, at the election of the Company, the sole remedy for the failure
by the Company to comply with its obligations under Section 314(a)(1) of the Trust Indenture Act,
shall for the first 90 calendar days after the occurrence of such an Event of Default consist
exclusively of the right (the “Extension Right”) to receive additional interest on the Securities
at an annual rate equal to 0.50% of the principal amount of the Securities (the “Additional
Interest”). If the Company so elects, the Additional Interest shall be payable on all Outstanding
Securities on the date on which the Event of Default relating to a failure to comply with the
requirements of Section 314(a)(1) of the Trust Indenture Act first occurs to but not including the
90th day thereafter (or such earlier date on which the Event of Default relating to the
reporting obligations shall have been cured or waived) and shall be payable on each relevant
Interest Payment Date to Holders of record on the relevant Regular Record Date immediately
preceding that Interest Payment Date. If such Event of Default has not been cured or waived prior
to such 91st calendar day, then the Trustee or the Holders of not less than 25% in principal amount
of the Outstanding Securities may declare the principal of and accrued and unpaid interest on all
such Securities to be due and payable immediately.

If the Company elects to pay the Additional Interest as the sole remedy for the failure by the
Company to comply with the requirements of Section 314(a)(1) of the Trust Indenture Act, the
Company shall notify in writing the Holders, the Paying Agent and the Trustee of such election at
any time on or before the close of business on the first Business Day following the date on which
such Event of Default first occurs.

If the Company fails to give timely notice or pay the Additional Interest, then the Trustee or
the Holders of not less than 25% in principal amount of the outstanding Securities may declare the
principal of and accrued and unpaid interest on all such Securities to be due and payable
immediately. If any Additional Interest is payable under this Section 502, the Company shall
deliver to the Trustee a certificate to that effect stating (i) the amount of such Additional
Interest that is payable and (ii) the date on which such Additional Interest is payable. Unless and
until a Responsible Officer of the Trustee receives at the Corporate Trust Office such a
certificate, the Trustee may assume without inquiry that the Additional Interest is not payable. If
the Additional Interest has been paid by the Company directly to the persons entitled to it, the
Company shall deliver to the Trustee a certificate setting forth the particulars of such payment.

Notwithstanding the foregoing paragraph, if an Event of Default occurs under any series of the
Company’s debt securities (other than the Securities ) issued subsequent to the Issue Date
resulting from the Company’s failure to comply with the requirements of Section 314(a)(1) of the
Trust Indenture Act, and such Event of Default is not subject to extension on terms similar to
those set forth in the foregoing paragraph and results in the principal amount of such debt
securities becoming due and payable, then the Extension Right shall no longer apply and the
Securities shall be subject to acceleration as provided in the first paragraph of this Section 502.

This Section 502, however, is subject to the conditions that if, at any time after the
principal of the Securities shall have been so declared due and payable, and before any judgment or
decree for the payment of the monies due shall have been obtained or entered as hereinafter
provided, the Company shall pay or shall deposit with the Trustee a sum sufficient to pay
installments of accrued and unpaid interest upon all Securities and the principal of any and all
Securities that shall have become due otherwise than by acceleration (with interest on overdue
installments of accrued and unpaid interest (to the extent that payment of such interest is
enforceable under applicable law) and on such principal at the rate borne by the Securities during
the period of such Default), and if (1) rescission would not conflict with any judgment or decree
of a court of competent jurisdiction and (2) any and all Events of Default under this Indenture
with respect to such Securities, other than the nonpayment of principal of and accrued and unpaid
interest on such Securities or failure to deliver amounts due upon conversion that shall have
become due solely by such acceleration, shall have been cured or waived pursuant to Section 513,
then and in every such case the Holders of a majority in aggregate principal amount of the
Outstanding Securities, by written notice to the Company and to the Trustee, may waive all Defaults
or Events of Default with respect to the Securities and rescind and annul such declaration and its
consequences and such Default shall cease to exist, and any Event of Default arising therefrom
shall be deemed to have been cured for every purpose of this Indenture; but no such waiver or
rescission and annulment shall extend to or shall affect any subsequent Default or Event of
Default, or shall impair any right consequent thereon. No rescission or annulment referred to above
shall affect any subsequent Default or impair any right consequent thereon.

	 	 	SECTION 503. Collection of Indebtedness and Suits for Enforcement by Trustee.

The Company covenants that if

(1) default is made in the payment of any interest on any Security when such interest
becomes due and payable and such default continues for a period of 30 days, or

(2) default is made in the payment of the principal of any Security at the Maturity
thereof,

the Company will, upon demand of the Trustee, pay to it, for the benefit of the Holders of such
Securities, the whole amount then due and payable on such Securities for principal and interest,
and, to the extent that payment of such interest shall be legally enforceable, interest on any
overdue principal and on any overdue interest, at the rate borne by the Securities, and, in
addition thereto, such further amount as shall be sufficient to cover the costs and expenses of
collection, including the reasonable compensation, expenses, disbursements and advances of the
Trustee, its agents and counsel.

If an Event of Default occurs and is continuing, the Trustee may in its discretion proceed to
protect and enforce its rights and the rights of the Holders by such appropriate judicial
proceedings as the Trustee shall deem most effectual to protect and enforce any such rights,
whether for the specific enforcement of any covenant or agreement in this Indenture or in aid of
the exercise of any power granted herein, or to enforce any other proper remedy.

	 	 	SECTION 504. Trustee May File Proofs of Claim.

In case of any judicial proceeding relative to the Company (or any other obligor upon the
Securities), its property or its creditors, the Trustee shall be entitled and empowered, by
intervention in such proceeding or otherwise, to take any and all actions authorized under the
Trust Indenture Act in order to have claims of the Holders and the Trustee allowed in any such
proceeding. In particular, the Trustee shall be authorized to collect and receive any moneys or
other property payable or deliverable on any such claims and to distribute the same; and any
custodian, receiver, assignee, trustee, liquidator, sequestrator or other similar official in any
such judicial proceeding is hereby authorized by each Holder to make such payments to the Trustee
and, in the event that the Trustee shall consent to the making of such payments directly to the
Holders, to pay to the Trustee any amount due it for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, and any other amounts due the
Trustee under Section 607.

No provision of this Indenture shall be deemed to authorize the Trustee to authorize or
consent to or accept or adopt on behalf of any Holder any plan of reorganization, arrangement,
adjustment or composition affecting the Securities or the rights of any Holder thereof or to
authorize the Trustee to vote in respect of the claim of any Holder in any such proceeding.

	 	 	SECTION 505. Trustee May Enforce Claims Without Possession of Securities.

All rights of action and claims under this Indenture or the Securities may be prosecuted and
enforced by the Trustee without the possession of any of the Securities or the production thereof
in any proceeding relating thereto, and any such proceeding instituted by the Trustee shall be
brought in its own name as trustee of an express trust, and any recovery of judgment shall, after
provision for the payment of the reasonable compensation, expenses, disbursements and advances of
the Trustee, its agents and counsel, be for the ratable benefit of the Holders of the Securities in
respect of which such judgment has been recovered.

	 	 	SECTION 506. Application of Money Collected.

Subject to Article Twelve, any money or property money collected by the Trustee pursuant to
this Article shall be applied in the following order, at the date or dates fixed by the Trustee
and, in case of the distribution of such money on account of principal or interest, upon
presentation of the Securities and the notation thereon of the payment if only partially paid and
upon surrender thereof if fully paid:

FIRST: To the payment of all amounts due the Trustee under Section 607;

SECOND: To the payment of the amounts then due and unpaid for principal of and
interest on the Securities in respect of which or for the benefit of which such money has
been collected, ratably, without preference or priority of any kind, according to the
amounts due and payable on such Securities for principal and interest, respectively; and

THIRD: The balance, if any, to the Company or an other Person or Persons entitled
thereto.

	 	 	SECTION 507. Limitation on Suits.

No Holder of any Security shall have any right to institute any proceeding, judicial or
otherwise, with respect to this Indenture, or for the appointment of a receiver or trustee, or for
any other remedy hereunder, unless

(1) such Holder has previously given written notice to the Trustee of a continuing
Event of Default;

(2) the Holders of not less than 25% in principal amount of the Outstanding Securities
shall have made written request to the Trustee to institute proceedings in respect of such
Event of Default in its own name as Trustee hereunder;

(3) such Holder or Holders have offered to the Trustee reasonable indemnity against
the costs, expenses and liabilities to be incurred in compliance with such request;

(4) the Trustee for 60 days after its receipt of such notice, request and offer of
indemnity has failed to institute any such proceeding; and

(5) no direction inconsistent with such written request has been given to the Trustee
during such 60-day period by the Holders of a majority in principal amount of the
Outstanding Securities;

it being understood and intended that no one or more Holders shall have any right in any manner
whatever by virtue of, or by availing of, any provision of this Indenture to affect, disturb or
prejudice the rights of any other Holders, or to obtain or to seek to obtain priority or preference
over any other Holders or to enforce any right under this Indenture, except in the manner herein
provided and for the equal and ratable benefit of all the Holders.

	 	 	SECTION 508. Unconditional Right of Holders to Receive Principal and Interest and to
Convert

Notwithstanding any other provision in this Indenture, the Holder of any Security shall have
the right, which is absolute and unconditional, to receive payment of the principal of and (subject
to Section 308) interest on such Security on the respective Stated Maturities expressed in such
Security and to convert such Security in accordance with Article Twelve and to institute suit for
the enforcement of any such payment and right to convert, and such rights shall not be impaired
without the consent of such Holder.

	 	 	SECTION 509. Restoration of Rights and Remedies.

If the Trustee or any Holder has instituted any proceeding to enforce any right or remedy
under this Indenture and such proceeding has been discontinued or abandoned for any reason, or has
been determined adversely to the Trustee or to such Holder, then and in every such case, subject to
any determination in such proceeding, the Company, the Trustee and the Holders shall be restored
severally and respectively to their former positions hereunder and thereafter all rights and
remedies of the Trustee and the Holders shall continue as though no such proceeding had been
instituted.

	 	 	SECTION 510. Rights and Remedies Cumulative.

Except as otherwise provided with respect to the replacement or payment of mutilated,
destroyed, lost or stolen Securities in the last paragraph of Section 307, no right or remedy
herein conferred upon or reserved to the Trustee or to the Holders is intended to be exclusive of
any other right or remedy, and every right and remedy shall, to the extent permitted by law, be
cumulative and in addition to every other right and remedy given hereunder or now or hereafter
existing at law or in equity or otherwise. The assertion or employment of any right or remedy
hereunder, or otherwise, shall not prevent the concurrent assertion or employment of any other
appropriate right or remedy.

	 	 	SECTION 511. Delay or Omission Not Waiver.

No delay or omission of the Trustee or of any Holder of any Security to exercise any right or
remedy accruing upon any Event of Default shall impair any such right or remedy or constitute a
waiver of any such Event of Default or an acquiescence therein. Every right and remedy given by
this Article or by law to the Trustee or to the Holders may be exercised from time to time, and as
often as may be deemed expedient, by the Trustee (subject to the limitations contained in this
Indenture) or by the Holders, as the case may be.

	 	 	SECTION 512. Control by Holders.

The Holders of a majority in principal amount of the Outstanding Securities shall have the
right to direct the time, method and place of conducting any proceeding for any remedy available to
the Trustee or exercising any trust or power conferred on the Trustee, provided that

(1) such direction shall not be in conflict with any rule of law or with this
Indenture, and

(2) the Trustee may take any other action deemed proper by the Trustee which is not
inconsistent with such direction or this Indenture.

	 	 	SECTION 513. Waiver of Past Defaults.

The Holders of not less than a majority in principal amount of the Outstanding Securities may
on behalf of the Holders of all the Securities waive any past default hereunder and its
consequences, except a default

(1) in the payment of the principal of or interest on any Security, or

(2) in respect of a covenant or provision hereof which under Article Nine cannot be
modified or amended without the consent of the Holder of each Outstanding Security
affected.

Upon any such waiver, such default shall cease to exist, and any Event of Default arising
therefrom shall be deemed to have been cured, for every purpose of this Indenture; but no such
waiver shall extend to any subsequent or other default or impair any right consequent thereon.

	 	 	SECTION 514. Undertaking for Costs.

In any suit for the enforcement of any right or remedy under this Indenture, or in any suit
against the Trustee for any action taken, suffered or omitted by it as Trustee, a court may require
any party litigant in such suit to file an undertaking to pay the costs of such suit, and may
assess costs against any such party litigant, in the manner and to the extent provided in the Trust
Indenture Act; provided, that neither this Section nor the Trust Indenture Act shall be
deemed to authorize any court to require such an undertaking or to make such an assessment in any
suit instituted by the Company or in any suit for the enforcement of the right to convert any
Security in accordance with Article Twelve.

	 	 	SECTION 515. Waiver of Stay or Extension Laws.

The Company covenants (to the extent that it may lawfully do so) that it will not at any time
insist upon, or plead, or in any manner whatsoever claim or take the benefit or advantage of, any
usury, stay or extension law wherever enacted, now or at any time hereafter in force, which may
affect the covenants or the performance of this Indenture; and the Company (to the extent that it
may lawfully do so) hereby expressly waives all benefit or advantage of any such law and covenants
that it will not hinder, delay or impede the execution of any power herein granted to the Trustee,
but will suffer and permit the execution of every such power as though no such law had been
enacted.

ARTICLE SIX

The Trustee

	 	 	SECTION 601. Certain Duties and Responsibilities.

The duties and responsibilities of the Trustee shall be as provided by the Trust Indenture
Act. Notwithstanding the foregoing, no provision of this Indenture shall require the Trustee to
expend or risk its own funds or otherwise incur any financial liability in the performance of any
of its duties hereunder, or in the exercise of any of its rights or powers, if it shall have
reasonable grounds for believing that repayment of such funds or adequate indemnity against such
risk or liability is not reasonably assured to it. Whether or not therein expressly so provided,
every provision of this Indenture relating to the conduct or affecting the liability of or
affording protection to the Trustee shall be subject to the provisions of this Section. No
provision of this Indenture shall be construed to relieve the Trustee from liability for its own
negligent action, its own negligent failure to act or its own willful misconduct, subject to
Section 603.

	 	 	SECTION 602. Notice of Defaults.

The Trustee shall give the Holders notice of any default known to the Trustee that has
occurred and is continuing hereunder within 90 days after such default has occurred. Except in the
case of the default in the payment of principal of or interest on any Security or conversion
default, the Trustee need not deliver the notice if and so long as a committee of trust officers of
the Trustee in good faith determines that withholding the notice is in the interests of Holders.
In addition, the Trustee shall give the Holders of Securities notice of any default actually known
to it as and to the extent provided by the Trust Indenture Act. For the purpose of this Section,
the term “default” means any event which is, or after notice or lapse of time or both would become,
an Event of Default.

	 	 	SECTION 603. Certain Rights of Trustee.

Subject to the provisions of Section 601:

(a) the Trustee may rely and shall be protected in acting or refraining from acting upon any
resolution, certificate, statement, instrument, opinion, report, notice, request, direction,
consent, order, bond, debenture, note, other evidence of indebtedness or other paper or document
believed by it to be genuine and to have been signed or presented by the proper party or parties;

(b) any request or direction of the Company mentioned herein shall be sufficiently evidenced
by a Company Request or Company Order and any resolution of the Board of Directors may be
sufficiently evidenced by a Board Resolution;

(c) whenever in the administration of this Indenture the Trustee shall deem it desirable that
a matter be proved or established prior to taking, suffering or omitting any action hereunder, the
Trustee (unless other evidence be herein specifically prescribed) may, in the absence of bad faith
on its part, rely upon an Officers’ Certificate;

(d) the Trustee may consult with counsel and the written advice of such counsel or any Opinion
of Counsel shall be full and complete authorization and protection in respect of any action taken,
suffered or omitted by it hereunder in good faith and in reliance thereon;

(e) the Trustee shall be under no obligation to exercise any of the rights or powers vested in
it by this Indenture at the request or direction of any of the Holders pursuant to this Indenture,
unless such Holders shall have offered to the Trustee reasonable security or indemnity against the
costs, expenses and liabilities which might be incurred by it in compliance with such request or
direction;

(f) the Trustee shall not be bound to make any investigation into the facts or matters stated
in any resolution, certificate, statement, instrument, opinion, report, notice, request, direction,
consent, order, bond, debenture, note, other evidence of indebtedness or other paper or document,
but the Trustee, in its discretion, may make such further inquiry or investigation into such facts
or matters as it may see fit, and, if the Trustee shall determine to make such further inquiry or
investigation, it shall be entitled to examine the books, records and premises of the Company,
personally or by agent or attorney; and

(g) the Trustee may execute any of the trusts or powers hereunder or perform any duties
hereunder either directly or by or through agents or attorneys and the Trustee shall not be
responsible for any misconduct or negligence on the part of any agent or attorney appointed with
due care by it hereunder.

	 	 	SECTION 604. Not Responsible for Recitals or Issuance of Securities.

The recitals contained herein and in the Securities, except the Trustee’s certificates of
authentication, shall be taken as the statements of the Company, and the Trustee assumes no
responsibility for their correctness. The Trustee makes no representations as to the validity or
sufficiency of this Indenture or of the Securities. The Trustee shall not be accountable for the
use or application by the Company of Securities or the proceeds thereof.

	 	 	SECTION 605. May Hold Securities.

The Trustee, any Authenticating Agent, any Paying Agent, any Security Registrar or any other
agent of the Company, in its individual or any other capacity, may become the owner or pledgee of
Securities and, subject to Sections 608 and 613, may otherwise deal with the Company with the same
rights it would have if it were not Trustee, Authenticating Agent, Paying Agent, Security Registrar
or such other agent.

	 	 	SECTION 606. Money Held in Trust.

Money held by the Trustee in trust hereunder need not be segregated from other funds except to
the extent required by law. The Trustee shall be under no liability for interest on any money
received by it hereunder except as otherwise agreed with the Company.

	 	 	SECTION 607. Compensation and Reimbursement.

The Company agrees

(1) to pay to the Trustee from time to time reasonable compensation as shall be
agreed in writing between the Company and the Trustee for all services rendered by it
hereunder (which compensation shall not be limited by any provision of law in regard to the
compensation of a trustee of an express trust);

(2) except as otherwise expressly provided herein, to reimburse the Trustee upon its
request for all reasonable expenses, disbursements and advances incurred or made by the
Trustee in accordance with any provision of this Indenture (including the reasonable
compensation and the expenses and disbursements of its agents and counsel), except any such
expense, disbursement or advance as may be attributable to its negligence or bad faith; and

(3) to indemnify the Trustee for, and to hold it harmless against, any loss, liability
or expense incurred without negligence or bad faith on its part, arising out of or in
connection with the acceptance or administration of this trust, including the costs and
expenses of defending itself against any claim or liability in connection with the exercise
or performance of any of its powers or duties hereunder.

	 	 	SECTION 608. Disqualification; Conflicting Interests.

If the Trustee has or shall acquire a conflicting interest within the meaning of the Trust
Indenture Act, the Trustee shall either eliminate such interest or resign, to the extent and in the
manner provided by, and subject to the provisions of, the Trust Indenture Act and this Indenture.

	 	 	SECTION 609. Corporate Trustee Required; Eligibility.

There shall at all times be a Trustee hereunder which shall be a Person that is eligible
pursuant to the Trust Indenture Act to act as such and has a combined capital and surplus of at
least $50,000,000. If such Person publishes reports of condition at least annually, pursuant to
law or to the requirements of said supervising or examining authority, then for the purposes of
this Section, the combined capital and surplus of such Person shall be deemed to be its combined
capital and surplus as set forth in its most recent report of condition so published. If at any
time the Trustee shall cease to be eligible in accordance with the provisions of this Section, it
shall resign immediately in the manner and with the effect hereinafter specified in this Article.

	 	 	SECTION 610. Resignation and Removal; Appointment of Successor.

(a) No resignation or removal of the Trustee and no appointment of a successor Trustee
pursuant to this Article shall become effective until the acceptance of appointment by the
successor Trustee under Section 611.

(b) The Trustee may resign at any time by giving written notice thereof to the Company. If an
instrument of acceptance by a successor Trustee shall not have been delivered to the Trustee within
30 days after the giving of such notice of resignation, the resigning Trustee may petition any
court of competent jurisdiction for the appointment of a successor Trustee.

(c) The Trustee may be removed at any time by Act of the Holders of a majority in principal
amount of the Outstanding Securities, delivered to the Trustee and to the Company.

(d) If at any time:

(1) the Trustee shall fail to comply with Section 608 after written request therefor
by the Company or by any Holder who has been a bona fide Holder of a Security for at least
six months, or

(2) the Trustee shall cease to be eligible under Section 609 and shall fail to resign
after written request therefor by the Company or by any such Holder, or

(3) the Trustee shall become incapable of acting or shall be adjudged a bankrupt or
insolvent or a receiver of the Trustee or of its property shall be appointed or any public
officer shall take charge or control of the Trustee or of its property or affairs for the
purpose of rehabilitation, conservation or liquidation,

then, in any such case, (i) the Company by a Board Resolution may remove the Trustee, or
(ii) subject to Section 514, any Holder who has been a bona fide Holder of a Security for at least
six months may, on behalf of himself and all others similarly situated, petition any court of
competent jurisdiction for the removal of the Trustee and the appointment of a successor Trustee.

(e) If the Trustee shall resign, be removed or become incapable of acting, or if a vacancy
shall occur in the office of Trustee for any cause, the Company, by a Board Resolution, shall
promptly appoint a successor Trustee. If, within one year after such resignation, removal or
incapability, or the occurrence of such vacancy, a successor Trustee shall be appointed by Act of
the Holders of a majority in principal amount of the Outstanding Securities delivered to the
Company and the retiring Trustee, the successor Trustee so appointed shall, forthwith upon its
acceptance of such appointment, become the successor Trustee and supersede the successor Trustee
appointed by the Company. If no successor Trustee shall have been so appointed by the Company or
the Holders and accepted appointment in the manner hereinafter provided, any Holder who has been a
bona fide Holder of a Security for at least six months may, on behalf of himself and all others
similarly situated, petition any court of competent jurisdiction for the appointment of a successor
Trustee. Notwithstanding replacement of the Trustee pursuant to this Section 610, the Company’s
obligations under Section 607 hereof shall continue for the benefit of the retiring Trustee.

(f) The Company shall give notice of each resignation and each removal of the Trustee and each
appointment of a successor Trustee to all Holders in the manner provided in Section 106. Each
notice shall include the name of the successor Trustee and the address of its Corporate Trust
Office.

	 	 	SECTION 611. Acceptance of Appointment by Successor.

In case of the appointment hereunder of a successor Trustee, such successor Trustee shall
execute, acknowledge and deliver to the Company and to the retiring Trustee an instrument accepting
such appointment, and thereupon the resignation or removal of the retiring Trustee shall become
effective and such successor Trustee, without any further act, deed or conveyance, shall become
vested with all the rights, powers, trusts and duties of the retiring Trustee; but, on request of
the Company or the successor Trustee, such retiring Trustee shall, upon payment of its charges,
execute and deliver an instrument transferring to such successor Trustee all the rights, powers and
trusts of the retiring Trustee and shall duly assign, transfer and deliver to such successor
Trustee all property and money held by such retiring Trustee hereunder. Upon the reasonable
written request of any such successor Trustee, the Company shall execute any and all instruments
for more fully and certainly vesting in and confirming to such successor Trustee all such rights,
powers and trusts.

No successor Trustee shall accept its appointment unless at the time of such acceptance such
successor Trustee shall be qualified and eligible under this Article.

	 	 	SECTION 612. Merger, Conversion, Consolidation or Succession to Business.

Any corporation into which the Trustee may be merged or converted or with which it may be
consolidated, or any corporation resulting from any merger, conversion or consolidation to which
the Trustee shall be a party, or any corporation succeeding to all or substantially all the
corporate trust business of the Trustee, shall be the successor of the Trustee hereunder, provided
such corporation shall be otherwise qualified and eligible under this Article, without the
execution or filing of any paper or any further act on the part of any of the parties hereto. In
case any Securities shall have been authenticated, but not delivered, by the Trustee then in
office, any successor by merger, conversion or consolidation to such authenticating Trustee may
adopt such authentication and deliver the Securities so authenticated with the same effect as if
such successor Trustee had itself authenticated such Securities.

	 	 	SECTION 613. Preferential Collection of Claims Against Company.

If and when the Trustee shall be or become a creditor of the Company (or any other obligor
upon the Securities), the Trustee shall be subject to the provisions of the Trust Indenture Act
regarding the collection of claims against the Company (or any such other obligor).

	 	 	SECTION 614. Appointment of Authenticating Agent.

The Trustee may appoint an Authenticating Agent or Agents which shall be authorized to act on
behalf of the Trustee to authenticate Securities issued upon original issue and upon exchange,
registration of transfer, partial conversion or pursuant to Section 306, and Securities so
authenticated shall be entitled to the benefits of this Indenture and shall be valid and obligatory
for all purposes as if authenticated by the Trustee hereunder. Wherever reference is made in this
Indenture to the authentication and delivery of Securities by the Trustee or the Trustee’s
certificate of authentication, such reference shall be deemed to include authentication and
delivery on behalf of the Trustee by an Authenticating Agent and a certificate of authentication
executed on behalf of the Trustee by an Authenticating Agent. Each Authenticating Agent shall be
acceptable to the Company and shall at all times be a corporation organized and doing business
under the laws of the United States of America, any State thereof or the District of Columbia,
authorized under such laws to act as Authenticating Agent, having a combined capital and surplus of
not less than $50,000,000 and subject to supervision or examination by Federal or State authority.
If such Authenticating Agent publishes reports of condition at least annually, pursuant to law or
to the requirements of said supervising or examining authority, then for the purposes of this
Section, the combined capital and surplus of such Authenticating Agent shall be deemed to be its
combined capital and surplus as set forth in its most recent report of condition so published. If
at any time an Authenticating Agent shall cease to be eligible in accordance with the provisions of
this Section, such Authenticating Agent shall resign immediately in the manner and with the effect
specified in this Section.

Any corporation into which an Authenticating Agent may be merged or converted or with which it
may be consolidated, or any corporation resulting from any merger, conversion or consolidation to
which such Authenticating Agent shall be a party, or any corporation succeeding to all or
substantially all the corporate agency or corporate trust business of an Authenticating Agent,
shall continue to be an Authenticating Agent, provided such corporation shall be otherwise eligible
under this Section, without the execution or filing of any paper or any further act on the part of
the Trustee or the Authenticating Agent.

An Authenticating Agent may resign at any time by giving written notice thereof to the Trustee
and to the Company. The Trustee may at any time terminate the agency of an Authenticating Agent by
giving written notice thereof to such Authenticating Agent and to the Company. Upon receiving such
a notice of resignation or upon such a termination, or in case at any time such Authenticating
Agent shall cease to be eligible in accordance with the provisions of this Section, the Trustee may
appoint a successor Authenticating Agent which shall be acceptable to the Company and shall deliver
written notice of such appointment by first-class mail, postage prepaid, to all Holders as their
names and addresses appear in the Security Register, or by such other means reasonably acceptable
to such Holders. Any successor Authenticating Agent upon acceptance of its appointment hereunder
shall become vested with all the rights, powers and duties of its predecessor hereunder, with like
effect as if originally named as an Authenticating Agent. No successor Authenticating Agent shall
be appointed unless eligible under the provisions of this Section.

The Trustee agrees to pay to each Authenticating Agent from time to time reasonable
compensation for its services under this Section, and the Trustee shall be entitled to be
reimbursed for such payments, subject to the provisions of Section 607.

If an appointment is made pursuant to this Section, the Securities may have endorsed thereon,
in addition to the Trustee’s certificate of authentication, an alternative certificate of
authentication in the following form:

This is one of the Securities described in the within-mentioned Indenture.

     

WELLS FARGO BANK, N.A.

As Trustee

By:      

As Authenticating Agent

By:      

Authorized Officer

ARTICLE SEVEN

Holders’ Lists and Reports by Trustee and Company

	 	 	SECTION 701. Company to Furnish Trustee Names and Addresses of Holders.

The Company will furnish or cause to be furnished to the Trustee

(a) semi-annually, not more than 15 days after each Regular Record Date, a list, in such form
as the Trustee may reasonably require, of the names and addresses of the Holders as of such Regular
Record Date, and

(b) at such other times as the Trustee may request in writing, within 30 days after the
receipt by the Company of any such request, a list of similar form and content as of a date not
more than 15 days prior to the time such list is furnished;

excluding from any such list names and addresses received by the Trustee in its capacity as
Security Registrar.

	 	 	SECTION 702. Preservation of Information; Communications to Holders.

(a) The Trustee shall preserve, in as current a form as is reasonably practicable, the names
and addresses of Holders contained in the most recent list furnished to the Trustee as provided in
Section 701 and the names and addresses of Holders received by the Trustee in its capacity as
Security Registrar. The Trustee may destroy any list furnished to it as provided in Section 701
upon receipt of a new list so furnished.

(b) The rights of Holders to communicate with other Holders with respect to their rights under
this Indenture or under the Securities, and the corresponding rights and duties of the Trustee,
shall be as provided by the Trust Indenture Act.

(c) Every Holder of Securities, by receiving and holding the same, agrees with the Company and
the Trustee that neither the Company nor the Trustee nor any agent of either of them shall be held
accountable by reason of any disclosure of information as to names and addresses of Holders made
pursuant to the Trust Indenture Act.

	 	 	SECTION 703. Reports by Trustee.

(a) The Trustee shall transmit to Holders such reports concerning the Trustee and its actions
under this Indenture as may be required pursuant to the Trust Indenture Act at the times and in the
manner provided pursuant thereto.

(b) A copy of each such report shall, at the time of such transmission to Holders, be filed by
the Trustee with each stock exchange upon which the Securities are listed, with the Commission and
with the Company. The Company will notify the Trustee when the Securities are listed on any stock
exchange.

	 	 	SECTION 704. Reports by Company.

The Company shall file with the Commission information, documents or reports required to be
filed with the Commission pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
and shall file with the Trustee within 15 days after the same is so required to be filed with the
Commission and shall otherwise comply with the requirements of Trust Indenture Act Section 314(a);
provided that any such information, documents or reports filed or furnished with the Commission
pursuant to its Electronic Data Gathering, Analysis and Retrieval (or EDGAR) system shall be deemed
to be filed with the Trustee as of the time such information, documents or reports are filed or
furnished via EDGAR.

If at any time the Company is not subject to Sections 13 or 15(d) of the Exchange Act, the
Company shall, so long as any of the Securities shall, at such time, constitute “Restricted
Securities” within the meaning of Rule 144(a)(3) under the Securities Act, promptly provide to the
Trustee and shall, upon written request, provide to any holder, beneficial owner or prospective
purchaser of such Securities, the information required to be delivered pursuant to Rule 144A(d)(4)
under the Securities Act to facilitate the resale of such Securities pursuant to Rule 144A under
the Securities Act. The Company shall take such further action as any holder or beneficial owner of
such Securities may reasonably request to the extent required from time to time to enable such
holder or beneficial holder to sell such Securities in accordance with Rule 144A under the
Securities Act, as such rule may be amended from time to time.

Delivery of such reports, information and documents to the Trustee is for informational
purposes only, and the Trustee’s receipt of such shall not constitute constructive notice of any
information contained therein or determinable from information contained therein, including the
Company’s compliance with any of its covenants hereunder (as to which the Trustee is entitled to
conclusively rely exclusively on an Officers’ Certificate).

ARTICLE EIGHT

Consolidation, Merger, Conveyance, Transfer or Lease

	 	 	SECTION 801. Company May Consolidate, Etc., Only on Certain Terms.

The Company shall not consolidate with or merge into any other Person or convey, transfer or
lease its properties and assets substantially as an entirety to any Person, unless:

(1) in case the Company shall consolidate with or merge into another Person or convey,
transfer or lease its properties and assets substantially as an entirety to any Person
(whereby the Company is not the surviving Person), the Person formed by such consolidation
or into which the Company is merged or the Person which acquires by conveyance or transfer,
or which leases, the properties and assets of the Company substantially as an entirety
shall be a corporation, partnership or trust, shall be organized and validly existing under
the laws of the United States of America, any State thereof or the District of Columbia and
such Person (if not the Company) shall expressly assume, by an indenture supplemental
hereto, executed and delivered to the Trustee, in form satisfactory to the Trustee, the due
and punctual payment of the principal of and interest on all the Securities and the
performance or observance of every covenant of this Indenture on the part of the Company to
be performed or observed and shall have provided for conversion rights in accordance with
Section 1201;

(2) immediately after giving effect to such transaction and treating any indebtedness
which becomes an obligation of the Company or a Subsidiary as a result of such transaction
as having been incurred by the Company or such Subsidiary at the time of such transaction,
no Event of Default, and no event which, after notice or lapse of time or both, would
become an Event of Default, shall have happened and be continuing; and

(3) the Company has delivered to the Trustee an Officers’ Certificate and an Opinion
of Counsel, each stating that such consolidation, merger, conveyance, transfer or lease
and, if a supplemental indenture is required in connection with such transaction, such
supplemental indenture comply with this Article and that all conditions precedent herein
provided for relating to such transaction have been complied with.

	 	 	SECTION 802. Successor Substituted.

Upon any consolidation of the Company with, or merger of the Company into, any other Person or
any conveyance, transfer or lease of the properties and assets of the Company substantially as an
entirety in accordance with Section 801, the successor Person formed by such consolidation or into
which the Company is merged or to which such conveyance, transfer or lease is made shall succeed
to, and be substituted for, and may exercise every right and power of, the Company under this
Indenture with the same effect as if such successor Person had been named as the Company herein,
and thereafter, except in the case of a lease, the predecessor Person shall be relieved of all
obligations and covenants under this Indenture and the Securities.

ARTICLE NINE

Modification and Amendment

	 	 	SECTION 901. Supplemental Indentures Without Consent of Holders.

Without the consent of any Holders, the Company, when authorized by a Board Resolution, and
the Trustee, at any time and from time to time, may enter into one or more indentures supplemental
hereto, in form satisfactory to the Trustee, for any of the following purposes:

(1) to evidence the succession of another Person to the Company and the assumption by
any such successor of the covenants of the Company herein and in the Securities; or

(2) to add to the covenants of the Company for the benefit of the Holders, or to
surrender any right or power herein conferred upon the Company; or

(3) to add guarantees with respect to the Securities; or

(4) to secure the Securities pursuant to the requirements of Section 1003 or
otherwise; or

(5) to make provision with respect to the conversion rights of Holders pursuant to the
requirements of Section 1201; or

(6) to increase the conversion rate of the Securities; or

(7) to provide for conversion of the Securities; or

(8) to provide for the issuance of additional Securities, to the extent that the
Company and the Trustee deem such amendment necessary or advisable in connection with such
issuance; provided however, that no such amendment or supplement may impair the rights or
interests of any holder of outstanding Securities; or

(9) to cure any ambiguity, manifest error or defect or omission or to correct or
supplement any provision herein which may be inconsistent with any other provision herein,
or to make any other provisions with respect to matters or questions arising under this
Indenture which shall not be inconsistent with the provisions of this Indenture,
provided that such action pursuant to this Section 901 shall not adversely affect
the interests of the Holders in any material respect; or

(10) to make any change that does not adversely affect the rights of any Holder in any
material respect; provided that any amendment to conform the terms of this Indenture or the
Securities to the “Description of Notes” section of the Company’s final prospectus
supplement dated September 24, 2007, filed with the SEC relating to the offering of the
Securities will not be deemed to be adverse to any holder; or

(11) to comply with any requirement of the SEC in connection with the qualification of
the Indenture under the Trust Indenture Act; or

(12) to provide for a successor trustee in accordance with the terms of this Indenture
of to otherwise comply with any requirements of this Indenture.

	 	 	SECTION 902. Supplemental Indentures with Consent of Holders.

With the consent of the Holders of not less than a majority in principal amount of the
Outstanding Securities, by Act of said Holders delivered to the Company and the Trustee, the
Company, when authorized by a Board Resolution, and the Trustee may enter into an indenture or
indentures supplemental hereto for the purpose of adding any provisions to or changing in any
manner or eliminating any of the provisions of this Indenture or of modifying in any manner the
rights of the Holders under this Indenture; provided, however, that no such
supplemental indenture shall, without the consent of the Holder of each Outstanding Security
affected thereby,

(1) extend the Stated Maturity of the principal of, or any installment of interest on,
any Security; or

(2) reduce the principal amount or the rate of interest on any Security; or

(3) change the place of payment where, or the coin or currency in which, any the
principal of, interest on or additional interest, in respect of any Security is payable; or

(4) impair the right to institute suit for the enforcement of any such payment on or
after the Stated Maturity thereof; or

(5) adversely affect the right to convert any Security as provided in Article Twelve
(except as permitted by Section 901(5)); or

(6) reduce the Fundamental Change Repurchase Price of any Security or amend or modify
in any manner adverse to Holder the Company’s obligation to make such payment, whether
through amendment or waiver of provisions of the Indenture; or

(7) adversely affect the ranking of the Securities as senior unsecured indebtedness of
the Company; or

(8) reduce the percentage in principal amount of the Outstanding Securities, the
consent of whose Holders is required for any such supplemental indenture, or the consent of
whose Holders is required for any waiver (of compliance with certain provisions of this
Indenture or certain defaults hereunder and their consequences) provided for in this
Indenture; or

(9) modify any of the provisions of this Section or Section 513, except to increase
any such percentage or to provide that certain other provisions of this Indenture cannot be
modified or waived without the consent of the Holder of each Outstanding Security affected
thereby; provided, however, that this clause shall not be deemed to require the consent of
any Holder with respect to changes in the references to “the Trustee” and concomitant
changes in this Section, or the deletion of this proviso, in accordance with the
requirements of Sections 611 and 901(8).

It shall not be necessary for any Act of Holders under this Section to approve the particular
form of any proposed supplemental indenture, but it shall be sufficient if such Act shall approve
the substance thereof.

	 	 	SECTION 903. Execution of Supplemental Indentures.

In executing, or accepting the additional trusts created by, any supplemental indenture
permitted by this Article or the modifications thereby of the trusts created by this Indenture, the
Trustee shall be entitled to receive, and (subject to Section 601) shall be fully protected in
relying upon, an Opinion of Counsel and an Officers’ Certificate stating that the execution of such
supplemental indenture is authorized or permitted by this Indenture. The Trustee may, but shall
not be obligated to, enter into any such supplemental indenture which affects the Trustee’s own
rights, duties or immunities under this Indenture or otherwise.

	 	 	SECTION 904. Effect of Supplemental Indentures.

Upon the execution of any supplemental indenture under this Article, this Indenture shall be
modified in accordance therewith, and such supplemental indenture shall form a part of this
Indenture for all purposes; and every Holder of Securities theretofore or thereafter authenticated
and delivered hereunder shall be bound thereby.

	 	 	SECTION 905. Conformity with Trust Indenture Act.

Every supplemental indenture executed pursuant to this Article shall conform to the
requirements of the Trust Indenture Act.

	 	 	SECTION 906. Reference in Securities to Supplemental Indentures.

Securities authenticated and delivered after the execution of any supplemental indenture
pursuant to this Article may, and shall if required by the Trustee, bear a notation in form
approved by the Trustee as to any matter provided for in such supplemental indenture. If the
Company shall so determine, new Securities so modified as to conform, in the opinion of the Trustee
and the Company, to any such supplemental indenture may be prepared and executed by the Company and
authenticated and delivered by the Trustee in exchange for Outstanding Securities.

ARTICLE TEN

Covenants

	 	 	SECTION 1001. Payment of Principal and Interest.

The Company will duly and punctually pay the principal of and interest on the Securities in
accordance with the terms of the Securities and this Indenture.

	 	 	SECTION 1002. Maintenance of Office or Agency.

The Company will maintain an office or agency (which shall be initially the Trustee’s
Corporate Trust Office) where Securities may be presented or surrendered for payment, where
Securities may be surrendered for registration of transfer or exchange, where Securities may be
surrendered for conversion and where notices and demands to or upon the Company in respect of the
Securities and this Indenture may be served. The Company will give prompt written notice to the
Trustee of any change in the location of such office or agency. If at any time the Company shall
fail to maintain any such required office or agency or shall fail to furnish the Trustee with the
address thereof, such presentations, surrenders, notices and demands may be made or served at the
Corporate Trust Office of the Trustee, and the Company hereby appoints the Trustee as its agent to
receive all such presentations, surrenders, notices and demands.

The Company may also from time to time designate one or more other offices or agencies where
the Securities may be presented or surrendered for any or all such purposes and may from time to
time rescind such designations; provided, however, that no such designation or
rescission shall in any manner relieve the Company of its obligation to maintain an office or
agency for such purposes as provided above. The Company will give prompt written notice to the
Trustee of any such designation or rescission and of any change in the location of any such other
office or agency.

	 	 	SECTION 1003. Money for Security Payments to Be Held in Trust.

If the Company shall at any time act as its own Paying Agent, it will, on or before each due
date of the principal of or interest on any of the Securities, segregate and hold in trust for the
benefit of the Persons entitled thereto a sum sufficient to pay the principal or interest so
becoming due until such sums shall be paid to such Persons or otherwise disposed of as herein
provided and will promptly notify the Trustee of its action or failure so to act.

Whenever the Company shall have one or more Paying Agents, it will, prior to each due date of
the principal of or interest on any Securities, deposit with a Paying Agent a sum sufficient to pay
such amount, such sum to be held as provided by the Trust Indenture Act, and (unless such Paying
Agent is the Trustee) the Company will promptly notify the Trustee of its action or failure so to
act.

The Company will cause each Paying Agent other than the Trustee to execute and deliver to the
Trustee an instrument in which such Paying Agent shall agree with the Trustee, subject to the
provisions of this Section, that such Paying Agent will (i) comply with the provisions of the Trust
Indenture Act applicable to it as a Paying Agent and (ii) during the continuance of any default by
the Company (or any other obligor upon the Securities) in the making of any payment in respect of
the Securities, upon the written request of the Trustee, forthwith pay to the Trustee all sums held
in trust by such Paying Agent as such.

The Company may at any time, for the purpose of obtaining the satisfaction and discharge of
this Indenture or for any other purpose, pay, or by Company Order direct any Paying Agent to pay,
to the Trustee all sums held in trust by the Company or such Paying Agent, such sums to be held by
the Trustee upon the same trusts as those upon which such sums were held by the Company or such
Paying Agent; and, upon such payment by any Paying Agent to the Trustee, such Paying Agent shall be
released from all further liability with respect to such money.

Subject to any applicable abandoned property law, any money deposited with the Trustee or any
Paying Agent, or then held by the Company, in trust for the payment of the principal of or interest
on any Security and remaining unclaimed for two years after such principal or interest has become
due and payable shall be paid to the Company on Company Request, or (if then held by the Company)
shall be discharged from such trust; and the Holder of such Security shall thereafter, as an
unsecured general creditor, look only to the Company for payment thereof, and all liability of the
Trustee or such Paying Agent with respect to such trust money, and all liability of the Company as
trustee thereof, shall thereupon cease; provided, however, that the Trustee or such
Paying Agent, before being required to make any such repayment, may at the expense of the Company
cause to be published once, in a newspaper published in the English language, customarily published
on each Business Day and of general circulation in New York, New York, notice that such money
remains unclaimed and that, after a date specified therein, which shall not be less than 30 days
from the date of such publication, any unclaimed balance of such money then remaining will be
repaid to the Company.

	 	 	SECTION 1004. Statement by Officers as to Default.

The Company will deliver to the Trustee, within 120 days after the end of each fiscal year of
the Company ending after the date hereof, an Officers’ Certificate, stating whether or not to the
best knowledge of the signers thereof the Company is in default in the performance and observance
of any of the terms, provisions and conditions of this Indenture (without regard to any period of
grace or requirement of notice provided hereunder) and, if the Company shall be in default,
specifying all such defaults and the nature and status thereof of which they may have knowledge.

In addition, the Company will deliver to the Trustee, within 30 days after the occurrence
thereof, written notice of any events that would constitute an Event of Default, the status of
those events and what action the Company is taking or propose to take in respect thereof.

	 	 	SECTION 1005. Existence.

Subject to Article Eight, the Company will do or cause to be done all things necessary to
preserve and keep in full force and effect its existence, rights (charter and statutory) and
franchises; provided, however, that the Company shall not be required to preserve
any such right or franchise if the Board of Directors shall determine that the preservation thereof
is no longer desirable in the conduct of the business of the Company and that the loss thereof is
not disadvantageous in any material respect to the Holders.

	 	 	SECTION 1006. Maintenance of Properties.

The Company will cause all properties used or useful in the conduct of its business or the
business of any Subsidiary to be maintained and kept in good condition, repair and working order
and supplied with all necessary equipment and will cause to be made all necessary repairs,
renewals, replacements, betterments and improvements thereof, all as in the judgment of the Company
may be necessary so that the business carried on in connection therewith may be properly and
advantageously conducted at all times; provided, however, that nothing in this
Section shall prevent the Company from discontinuing the operation or maintenance of any of such
properties if such discontinuance is, in the judgment of the Company, desirable in the conduct of
its business or the business of any Subsidiary and not disadvantageous in any material respect to
the Holders.

	 	 	SECTION 1007. Payment of Taxes and Other Claims.

The Company will pay or discharge or cause to be paid or discharged, before the same shall
become delinquent, (1) all taxes, assessments and governmental charges levied or imposed upon the
Company or any Subsidiary or upon the income, profits or property of the Company or any Subsidiary,
and (2) all lawful claims for labor, materials and supplies which, if unpaid, might by law become a
lien upon the property of the Company or any Subsidiary; provided, however, that
the Company shall not be required to pay or discharge or cause to be paid or discharged any such
tax, assessment, charge or claim whose amount, applicability or validity is being contested in good
faith by appropriate proceedings.

	 	 	 
	SECTION 1008.

	 	[Reserved]
	
 
	 	 
	SECTION 1009.

	 	Waiver of Certain Covenants.
	
 
	 	 

The Company may omit in any particular instance to comply with any covenant or condition set
forth in second and third paragraph of Section 704, if before the time for such compliance, the
Holders of at least a majority in principal amount of the Outstanding Securities shall, by Act of
such Holders, either waive such compliance in such instance or generally waive compliance with such
covenant or condition, but no such waiver shall extend to or affect such covenant or condition
except to the extent so expressly waived, and, until such waiver shall become effective, the
obligations of the Company and the duties of the Trustee in respect of any such covenant or
condition shall remain in full force and effect.

ARTICLE ELEVEN

Repurchase at Option of the Holder

	 	 	SECTION 1101. Repurchase at the Option of the Holder Upon a Fundamental Change.

(a) If a Fundamental Change occurs at any time, then each Holder shall have the right, at such
Holder’s option, to require the Company to repurchase all of such Holder’s Securities or any
portion thereof that is a multiple of $1,000 principal amount, for cash on the date (“the
Fundamental Change Repurchase Date”) specified by the Company that is not less than 20 calendar
days and not more than 35 calendar days after the date of the Fundamental Change Repurchase Right
Notice at a repurchase price equal to 100% of the principal amount thereof, together with accrued
and unpaid interest thereon to, but excluding, the Fundamental Change Repurchase Date, unless such
Fundamental Change Repurchase Date falls after a Regular Record Date and on or prior to the
corresponding Interest Payment Date, in which case the Company shall instead pay the full amount of
accrued and unpaid interest payable on such Interest Payment Date to the Holder of record at the
close of business on the corresponding Regular Record Date (the “Fundamental Change Repurchase
Price”).

However, notwithstanding the foregoing, Holders shall not have the right to require the
Company to repurchase any Securities (and the Company shall not be required to deliver the
Fundamental Change Repurchase Right Notice incidental thereto) if a Fundamental Change under
clauses (1) or (2) of the definition of Fundamental Change occurs and at least 90% of the
consideration paid for the Company’s Common Stock (excluding cash payments for fractional shares
and, cash payments made pursuant to dissenter’s appraisal rights and cash dividends) in the case of
a Fundamental Change under clause (2) of the definition of Fundamental Change consists of shares of
common equity or American Depositary Receipts in respect of shares of common equity traded on any
of the New York Stock Exchange, the American Stock Exchange, the NASDAQ Global Select Market or the
NASDAQ Global Market (or any of their respective successors) (or will be so traded immediately
following the completion of the merger or consolidation or such other transaction) and, as a result
of such transaction or transactions, the Securities become convertible into such shares of Common
Stock or such American Depositary Receipts.

Repurchases of Securities under this Section 1101 shall be made, at the option of the Holder
thereof, upon:

(i) if the Securities are held in certificated form, delivery to the Trustee (or other
Paying Agent appointed by the Company) by a Holder of a duly completed notice (the
“Fundamental Change Repurchase Notice”) in the form set forth on the reverse of the
Security or, if the Securities are held in global form, a notice that complies with the
Applicable Procedures, prior to the close of business on the Business Day immediately
preceding the Fundamental Change Repurchase Date; and

(ii) delivery or book-entry transfer of the Securities to the Trustee (or other Paying
Agent appointed by the Company) at any time after delivery of the Fundamental Change
Repurchase Notice (together with all necessary endorsements) at the Corporate Trust Office
of the Trustee (or other Paying Agent appointed by the Company), such delivery being a
condition to receipt by the Holder of the Fundamental Change Repurchase Price therefor;
provided that such Fundamental Change Repurchase Price shall be so paid pursuant to this
Section 1101 only if the Security so delivered to the Trustee (or other Paying Agent
appointed by the Company) shall conform in all respects to the description thereof in the
related Fundamental Change Repurchase Notice.

The Fundamental Change Repurchase Notice shall state:

(A) if certificated, the certificate numbers of Securities to be delivered for repurchase;

(B) the portion of the principal amount of Securities to be repurchased, which must be $1,000
or an integral multiple thereof; and

(C) that the Securities are to be repurchased by the Company pursuant to the applicable
provisions of the Securities and this Indenture.

Any purchase by the Company contemplated pursuant to the provisions of this Section 1101 shall
be consummated by the delivery of the consideration to be received by the Holder promptly following
the later of the Fundamental Change Repurchase Date and the time of the book-entry transfer or
delivery of the Security.

The Trustee (or other Paying Agent appointed by the Company) shall promptly notify the Company
of the receipt by it of any Fundamental Change Repurchase Notice or written notice of withdrawal
thereof in accordance with the provisions of subsection (c) of this Section 1101.

Any Security that is to be repurchased only in part shall be surrendered to the Trustee (with,
if the Company or the Trustee so requires, due endorsement by, or a written instrument of transfer
in form satisfactory to the Company and the Trustee duly executed by the Holder thereof or his
attorney duly authorized in writing), and the Company shall execute, and the Trustee shall
authenticate and make available for delivery to the Holder of such Security without service charge,
a new Security or Securities, containing identical terms and conditions, each in an authorized
denomination in aggregate principal amount equal to and in exchange for the unrepurchased portion
of the principal of the Security so surrendered.

(b) After the occurrence of a Fundamental Change, but on or before the 10th
calendar day after the Effective Date of such Fundamental Change, the Company shall provide to all
Holders of record of the Securities and the Trustee and Paying Agent a notice (the “Fundamental
Change Repurchase Right Notice”) of the occurrence of such Fundamental Change and of the repurchase
right, if any, at the option of the Holders arising as a result thereof. Such mailing shall be by
first class mail. Simultaneously with providing such Fundamental Change Repurchase Right Notice,
the Company shall publish a notice containing the information included therein in a newspaper of
general circulation in the City of New York or on the Company’s website or through such other
public medium as the Company may use at such time.

Each Fundamental Change Repurchase Right Notice shall specify (if applicable):

(a) the events causing the Fundamental Change;

(b) the date of the Fundamental Change;

(c) the last date on which a Holder may exercise its repurchase rights under
Section 1101, if applicable;

(d) the Fundamental Change Repurchase Price, if applicable;

(e) the Fundamental Change Repurchase Date, if applicable;

(f) the name and address of the Paying Agent and the Conversion Agent, if
applicable;

(g) the applicable Conversion Rate and any adjustments to the applicable
Conversion Rate;

(h) that the Securities with respect to which a Fundamental Change Purchase
Notice has been delivered by a Holder may be converted only if the Holder withdraws
the Fundamental Change Repurchase Notice in accordance with the terms of this
Indenture; and

(i) the procedures the Holder must follow to require the Company to purchase
its Securities under Section 1101, if applicable.

No failure of the Company to give the foregoing notices and no defect therein shall limit the
Holders’ repurchase rights or affect the validity of the proceedings for the repurchase of the
Securities pursuant to this Section 1101.

(c) A Fundamental Change Repurchase Notice may be withdrawn by means of a written notice of
withdrawal delivered to the Paying Agent in accordance with the Fundamental Change Repurchase Right
Notice at any time prior to the close of business on the Business Day prior to the Fundamental
Change Repurchase Date (the “Fundamental Change Expiration Time”), specifying:

(i) the principal amount of the withdrawn Securities and, if certificated Securities
have been issued, the certificate numbers of the withdrawn Securities,

(ii) the principal amount of the Security with respect to which such notice of
withdrawal is being submitted, and

(iii) the principal amount, if any, of such Security that remains subject to the
original Fundamental Change Repurchase Notice, which portion must be in principal amounts
of $1,000 or an integral multiple of $1,000;

provided, however, that if the Securities are not in certificated form, the notice must comply
with the Applicable Procedures.

(d) On or prior to 11:00 a.m., New York City time, on the Business Day on the Fundamental
Change Repurchase Date, the Company shall deposit with the Trustee (or other Paying Agent appointed
by the Company or if the Company is acting as its own Paying Agent, set aside, segregate and hold
in trust as provided in Section 606) an amount of money sufficient to repurchase on the Fundamental
Change Repurchase Date all of the Securities to be repurchased on such date at the Fundamental
Change Repurchase Price. Subject to receipt of funds and/or Securities by the Trustee (or other
Paying Agent appointed by the Company), payment for Securities surrendered for repurchase (and not
withdrawn) prior to the Fundamental Change Expiration Time shall be made promptly after the later
of (x) the Fundamental Change Repurchase Date with respect to such Security (provided the Holder
has satisfied the conditions to the payment of the Fundamental Change Repurchase Price in this
Section 1101), and (y) the time of book-entry transfer or the delivery of such Security to the
Trustee (or other Paying Agent appointed by the Company) by the Holder thereof in the manner
required by this Section 1101 by mailing checks for the amount payable to the Holders of such
Securities entitled thereto as they shall appear in the Register; provided, however, that all
payments shall be subject to Section 1101(a) and payments to the Depositary shall be made by wire
transfer of immediately available funds to the account of the Depositary or its nominee. The
Trustee shall, promptly after such payment and upon written demand by the Company, return to the
Company any funds in excess of the Fundamental Change Repurchase Price.

(e) If the Trustee (or other Paying Agent appointed by the Company) holds money sufficient to
repurchase on the Fundamental Change Repurchase Date all the Securities or portions thereof that
are to be purchased as of the Business Day following the Fundamental Change Repurchase Date, then
on and after the Fundamental Change Repurchase Date (i) such Securities shall cease to be
outstanding, (ii) interest shall cease to accrue on such Securities, and (iii) all other rights of
the Holders of such Securities shall terminate, whether or not book-entry transfer of the
Securities has been made or the Securities have been delivered to the Trustee or Paying Agent,
other than the right to receive the Fundamental Change Repurchase Price upon delivery or transfer
of the Securities.

(f) No Securities may be repurchased at the option of Holders upon a Fundamental Change if the
principal amount of the Securities has been accelerated, and such acceleration has not been
rescinded on or prior to such date.

ARTICLE TWELVE

Conversion of Securities

	 	 	SECTION 1201. Conversion Privilege and Conversion Rate.

(a) General. Solely upon the occurrence of any of the conditions described in clause (i),
(ii), and (iii) below, and upon compliance with the provisions of this Article, a Holder shall have
the right, at such Holder’s option, to convert all or any portion (if the portion to be converted
is $1,000 principal amount or an integral multiple thereof) of such Security at any time prior to
the close of business on the Scheduled Trading Day immediately preceding August 1, 2014, at a rate
(the “Conversion Rate”) of 83.6400 shares of Common Stock (subject to adjustment by the Company as
provided in Section 1204 and Section 1201(e)) per $1,000 principal amount of the Security (the
“Conversion Obligation”) under the circumstances and during the periods set forth below. On and
after August 1, 2014, regardless of the conditions described in clause (i), (ii) and (iii) below,
and upon compliance with the provisions of this Article, a Holder shall have the right, at such
Holder’s option, to convert all or any portion (if the portion to be converted is $1,000 principal
amount or an integral multiple thereof) of Securities at the Applicable Conversion Rate at any time
prior to the close of business on the Scheduled Trading Day immediately preceding the Stated
Maturity.

(i) Conversion Upon Satisfaction of Trading Price Condition. The Securities shall be
convertible prior to August 1, 2014, during the five Business Day period immediately after
any five consecutive Trading Day period (the “Measurement Period”) in which the Trading
Price per $1,000 principal amount of the Securities for each Trading Day of such
Measurement Period was less than 98% of the product of the Last Reported Sale Price of the
Common Stock on such Trading Day and the applicable Conversion Rate in effect on such
Trading Day (the “Trading Price Condition”) as determined as set forth below.

The Trustee shall have no obligation to determine the Trading Price unless the Company has
requested such determination; and the Company shall have no obligation to make such request unless
a Holder provides the Company with reasonable evidence that the Trading Price per $1,000 in
principal amount of the Securities would be less than ninety eight percent (98%) of the product of
the Last Reported Sale Price of the Common Stock and the Applicable Conversion Rate. Upon receipt
of such evidence, the Company shall instruct the Trustee to determine the Trading Price of the
Securities in the manner described below beginning on the next Trading Day and on each successive
Trading Day until the Trading Price per $1,000 in principal amount of the Securities is greater
than or equal to 98% of the product of the Last Reported Sale Price of the Common Stock and the
Applicable Conversion Rate. The Trustee’s sole duty in respect of such determination shall consist
of requesting and receiving and, if applicable, averaging the quotations provided by this Indenture
nationally recognized securities dealers referred to in the definition of “trading price.”
Notwithstanding the foregoing, if the Trustee cannot reasonably obtain at least one bid for $1.0
million principal amount of the Securities from a nationally recognized securities dealer selected
by the Board of Directors of the Company for the purpose of the determining the Trading Price on
any Trading Day, then the Trading Price per $1,000 principal amount of Securities shall be deemed
to be less than 98% of the product of (a) the then-applicable Conversion Rate of the Securities and
(b) the Last Reported Sale Price on such date (any such determination by the Trustee shall be
conclusive absent manifest error). Furthermore, if the Company does not, when obligated to do so,
make a request to the Trustee to determine the Trading Price of the Securities, or if the Company
so instructs the Trustee, but the Trustee does not make such determination, then the Trading Price
per $1,000 in principal amount of the Securities will be deemed to be less than 98% of the product
of the Last Reported Sale Price of the Common Stock and the Applicable Conversion Rate.

If the Trading Price Condition has been met, the Company will promptly notify the Holders of
the Securities and the Trustee. If, at any time after the Trading Price Condition has been met,
the Trading Price per $1,000 in principal amount of the Securities is greater than 98% of the
product of the Last Reported Sale Price of the Company’s Common Stock and the Applicable Conversion
Rate for such date, the Company will promptly notify the Holders of the Securities.

(ii) Conversion Based on Common Stock Price. The Securities shall be convertible
prior to August 1, 2014, during any calendar quarter after the calendar quarter ending
September 30, 2007 (and only during such calendar quarter), if the Last Reported Sale Price
of the Common Stock for twenty (20) or more Trading Days in a period of thirty (30)
consecutive Trading Days ending on the last Trading Day of the immediately preceding
calendar quarter exceeds one hundred twenty percent (120%) of the applicable Conversion
Price in effect on the last Trading Day of the immediately preceding calendar quarter.

(iii) Conversion Upon Occurrence of Certain Corporate Transactions. The Securities
shall be convertible prior to August 1, 2014, as provided in subsections (b), (c) and (d)
of this Section 1201.

(b) In the event that the Company elects to:

(i) distribute to all or substantially all holders of the Common Stock any rights or
warrants (other than rights distributed pursuant to a shareholder rights plan) entitling
them, for a period of not more than 45 calendar days after the date of such distribution,
to subscribe for or purchase the Common Stock at a price per share less than the average of
the Last Reported Sale Prices of the Common Stock for the ten (10) Trading Days immediately
preceding the declaration date of such distribution; or

(ii) distribute to all or substantially all holders of the Common Stock, assets
(including cash) or debt securities of the Company or rights to purchase the Company’s
securities, which distribution has a per share value (as determined by the Board of
Directors) exceeding 15% of the Last Reported Sale Price of the Common Stock on the Trading
Day immediately preceding the date of declaration of such distribution,

then, in either case, Holders may surrender the Securities for conversion at any time on and
after the date that the Company provides the notice referred to in the next sentence to such
Holders and the Trustee until the earlier of 5:00 p.m., New York City time, on the Business Day
immediately preceding the Ex-Date for such distribution or the date the Company announces that such
distribution will not take place. The Company shall notify Holders and the Trustee of any
distribution referred to in either clause (i) or clause (ii) above and of the resulting conversion
right no later than the 25th Scheduled Trading Day prior to the Ex-Date for such distribution. A
Holder may not exercise this right if such Holder is permitted to participate (as a result of
holding the Securities, and at the same time as holders of the Common Stock participate) in any
distribution referred to in clause (i) or clause (ii) above as if such Holder held a number of
shares of Common Stock equal to the then-applicable Conversion Rate, multiplied by the principal
amount (expressed in thousands) of Securities held by such Holder, without having to convert its
Securities.

(c) If the Company is a party to a combination, merger, recapitalization, reclassification,
binding share exchange or other similar transaction or sale or conveyance of all or substantially
all of its properties and assets, in each case pursuant to which the Common Stock would be
converted into cash, securities and/or other property, then the Holders shall have the right to
convert Securities at any time beginning on the effective date of the transaction and until and
including the date that is 25 Scheduled Trading Days after the date that is the effective date of
such transaction; provided such transaction does not otherwise constitute a Fundamental Change to
which the provisions of subsections (d) of this Section shall apply. The Company shall notify
Holders and the Trustee and issue a Press Release on the Effective Date of such transaction. The
Board of Directors shall determine the anticipated effective date of the transaction, and such
determination shall be conclusive and binding on the Holders.

(d) If a Fundamental Change occurs, the Company shall notify each of the Holders and the
Trustee of the occurrence of any such event or transaction on the Effective Date of such event or
transaction or, if later, within three Trading Days after the Company has knowledge of such event
or transaction. A Holder may surrender Securities for conversion at any time from and after the
Effective Date of such event or transaction until (i) the Fundamental Change Repurchase Date for
such event or transaction or (ii) if there is no such Fundamental Change Repurchase Date, 25
Scheduled Trading Days following the Effective Date of such Fundamental Change.

(e) If a Holder elects to convert Securities in connection with a Make-Whole Fundamental
Change that occurs prior to the Maturity Date, the Conversion Rate applicable to each $1,000
principal amount of Securities so converted shall be increased by an additional number of shares of
Common Stock (the “Additional Shares”) as described below; provided, however, that in the case of a
Fundamental Change described in clause (4) under the definition of Fundamental Change, no increase
will be made unless the shares of the Common Stock are not listed for trading for a period in
excess of thirty (30) calendar days; provided further that no increase shall be made in the case of
a Fundamental Change described in clause (2) of the definition of Fundamental Change if at least
90% of the consideration paid for the Company’s Common Stock (excluding cash payments for
fractional shares and cash payments made pursuant to dissenters’ appraisal rights) in such
transaction consists of shares of common equity or American Depositary Receipts in respect of
shares of common equity traded on any of the New York Stock Exchange, the American Stock Exchange,
the NASDAQ Global Market or the NASDAQ Global Select Market (or any of their respective successors)
(or that will be so traded immediately following the transaction) and as a result of such
transaction or transactions the Securities become convertible into such shares of such common
equity or such American Depositary Receipts (in respect of the principal portion of the Securities)
and such shares of such common equity or such American Depositary Receipts). For purposes of this
subsection (e), a conversion shall be deemed to be in connection with a Make-Whole Fundamental
Change if such conversion occurs on or after the Effective Date of a Fundamental Change described
in clauses (1) or (2), of such definition, in each case until the related Fundamental Change
Repurchase Date or, if there is no Fundamental Change Repurchase Date, 25 Scheduled Trading Days
following the Effective Date of such Fundamental Change, as applicable (regardless of whether the
provisions of clause (a)(i), (a)(ii), (b) or (c) of this Section shall apply to such conversion).

(i) The number of Additional Shares by which the Conversion Rate will be increased
shall be determined by the Company by reference to the table attached as Schedule A hereto,
based on the date on which the Make-Whole Fundamental Change occurs or becomes effective
(the “Make-Whole Reference Date”) and the Stock Price at the time of such Make-Whole
Fundamental Change; provided that if the actual Stock Price is between two Stock Price
amounts in the table or the Make-Whole Reference Date is between two Make-Whole Reference
Dates in the table, the number of Additional Shares shall be determined by a straight-line
interpolation between the number of Additional Shares set forth for the next higher and
next lower Stock Price amounts and the two nearest Effective Dates, as applicable, based on
a 365-day year; provided further that if (1) the Stock Price is greater than $100.00 per
share of Common Stock (subject to adjustment in the same manner as set forth in Section
1204), no Additional Shares shall be added to the Conversion Rate, and (2) the Stock Price
is less than $9.76 per share (subject to adjustment in the same manner as set forth in
Section 1204), no Additional Shares shall be added to the Conversion Rate. Notwithstanding
the foregoing, in no event shall the Conversion Rate exceed $102.4590 per $1,000 principal
amount of Securities (subject to adjustment in the same manner as set forth in Section
1204).

(ii) The Stock Prices set forth in the first column of the table in Schedule A hereto
(i.e., the row headers) shall be adjusted by the Company as of any date on which the
Conversion Rate of the Securities is adjusted. The adjusted Stock Prices shall equal the
Stock Prices applicable immediately prior to such adjustment, multiplied by a fraction, the
numerator of which is the applicable Conversion Rate in effect immediately prior to the
adjustment giving rise to the Stock Price adjustment and the denominator of which is the
Conversion Rate as so adjusted. The number of Additional Shares within the table shall be
adjusted in the same manner as the Conversion Rate as set forth in Section 1204.

	 	 	SECTION 1202. Exercise of Conversion Privilege.

(a) Subject to subsection (b) below, the Company shall satisfy the Conversion Obligation with
respect to each $1,000 principal amount of Securities tendered for conversion in shares of fully
paid Common Stock by delivering on the third Business Day following the relevant Conversion Date a
number of shares of Common Stock equal to (i) (A) the aggregate principal amount of Securities to
be converted, divided by (B) 1,000, multiplied by (ii) the Conversion Rate in effect on the
relevant Conversion Date; provided that the Company will deliver cash in lieu of fractional shares
of Common Stock as provided in Section 1203.

(b) Before any Holder of a Securities shall be entitled to convert the same as set forth
above, such Holder shall (1) in the case of a Global Securities, comply with the procedures of the
Depositary in effect at that time and, if required, pay funds equal to interest payable on the next
Interest Payment Date as set forth in subsection (h) of this Section 1202 and, if required, pay all
taxes or duties, if any, and (2) in the case of a Security issued in certificated form, (A)
complete and manually sign and deliver an irrevocable written notice to the Conversion Agent in the
form set forth under Section 205 (or a facsimile thereof) (a “Notice of Conversion”) at the office
of the Conversion Agent and shall state in writing therein the principal amount of Securities to be
converted and the name or names (with addresses) in which such Holder wishes the certificate or
certificates for any shares of Common Stock, if any, to be delivered upon settlement of the
Conversion Obligation to be registered, (B) surrender such Securities, duly endorsed to the Company
or in blank (and accompanied by appropriate endorsement and transfer documents), at the office of
the Conversion Agent, (C) if required, pay funds equal to interest payable on the next Interest
Payment Date to which such Holder is not entitled as set forth in subsection (h) of this Section
1202, (D) if required, pay all taxes or duties, if any and (E) if required, furnish appropriate
endorsements and transfer document. A Security shall be deemed to have been converted immediately
prior to the close of business on the date (the “Conversion Date”) that the Holder has complied
with the requirements set forth in this subsection (b).

No Notice of Conversion with respect to any Securities may be tendered by a Holder thereof if
such Holder has also tendered a Fundamental Change Repurchase Notice and not validly withdrawn such
Fundamental Change Repurchase Notice in accordance with the applicable provisions of Section 1101.

If more than one Security shall be surrendered for conversion at one time by the same Holder,
the Conversion Obligation with respect to such Securities, if any, that shall be payable upon
conversion shall be computed on the basis of the aggregate principal amount of the Securities (or
specified portions thereof to the extent permitted thereby) so surrendered.

(c) Delivery of the amounts owing in satisfaction of the Conversion Obligation shall be made
by the Company in no event later than the date specified in subsections (a) or (b), as applicable,
of this Section 1202. The Company shall make such delivery by paying the cash amount owed, if any,
to the Holder of the Security surrendered for conversion, or such Holder’s nominee or nominees,
and/or by issuing, or causing to be issued, and delivering to such Holder, or such Holder’s nominee
or nominees, certificates or a book-entry transfer through the Depositary for the number of full
shares of Common Stock, if any, to which such Holder shall be entitled as part of such Conversion
Obligation (together with any cash in lieu of fractional shares).

(d) In case any Security shall be surrendered for partial conversion, the Company shall
execute and the Trustee shall, as provided in a Company Order, authenticate and deliver to or upon
the written order of the Holder of the Security so surrendered, without charge to such Holder, a
new Security or Securities in authorized denominations in an aggregate principal amount equal to
the unconverted portion of the surrendered Securities.

(e) If a Holder submits a Security for conversion, the Company shall pay all stamp and other
duties, if any, which may be imposed by the United States or any political subdivision thereof or
taxing authority thereof or therein with respect to the issuance of shares of Common Stock, if any,
upon the conversion. However, the Holder shall pay any such tax which is due because the Holder
requests any shares of Common Stock to be issued in a name other than the Holder’s name. The
Company may refuse to deliver the certificates representing the shares of Common Stock being issued
in a name other than the Holder’s name until the Company receives a sum sufficient to pay any tax
which will be due because the shares are to be issued in a name other than the Holder’s name.
Nothing herein shall preclude any tax withholding required by law or regulations.

(f) Except as provided in Section 1204, no adjustment shall be made for dividends on any
shares issued upon the conversion of any Security as provided in this Article.

(g) Upon the conversion of an interest in a Global Security, the Trustee, or the custodian at
the direction of the Trustee, shall make a notation on such Global Security as to the reduction in
the principal amount represented thereby. The Company shall notify the Trustee in writing of any
conversion of Securities effected through any Conversion Agent other than the Trustee.

(h) Upon conversion, a Holder shall not receive any separate cash payment for accrued and
unpaid interest except as set forth below. The Company’s settlement of the Conversion Obligation as
described above shall be deemed to satisfy its obligation to pay the principal amount of the
Security and accrued and unpaid interest to, but not including, the Conversion Date. As a result,
accrued and unpaid interest to, but not including, the Conversion Date shall be deemed to be paid
in full rather than cancelled, extinguished or forfeited. Notwithstanding the preceding sentence,
if Securities are converted after 5:00 p.m., New York City time, on a Record Date, Holders of such
Securities as of 5:00 p.m., New York City time, on the Record Date shall receive the interest
payable on such Securities on the corresponding Interest Payment Date notwithstanding the
conversion. Securities surrendered for conversion during the period from 5:00 p.m., New York City
time, on any Regular Record Date to 9:00 a.m., New York City time, on the corresponding Interest
Payment Date must be accompanied by payment of an amount equal to the interest payable on the
Securities so converted; provided, however, that no such payment need be made (i) if the Company
has specified a Fundamental Change Repurchase Date that is after a Record Date and on or prior to
the corresponding Interest Payment Date; (ii) to the extent of any overdue interest existing at the
time of conversion with respect to such Security; or (iii) with respect to any Conversion Date that
occurs during the period from the close of business on the Regular Record Date immediately
preceding the Stated Maturity to the Stated Maturity. Except as described above, no payment or
adjustment shall be made for accrued interest on converted Securities.

	 	 	SECTION 1203. Fractions of Shares.

No fractional shares of Common Stock shall be issued upon conversion of any Security or
Securities. If more than one Security shall be surrendered for conversion at one time by the same
Holder, the number of full shares which shall be issuable upon conversion thereof shall be computed
on the basis of the aggregate principal amount of the Securities (or specified portions thereof) so
surrendered. Instead of any fractional share of Common Stock that would otherwise be issuable upon
conversion of any Security or Securities (or specified portions thereof), the Company shall
calculate and pay a cash adjustment in respect of such fraction (calculated to the nearest 1/100th
of a share) based on the Last Reported Sale Price of the Common Stock on the Conversion Date or if
the Conversion Date is not on a Trading Day, the next following Trading Day.

	 	 	SECTION 1204. Adjustment of Conversion Rate.

The Conversion Rate shall be adjusted from time to time by the Company as follows; provided
that the Company shall not make any adjustments to the Conversion Rate if Holders (as a result of
holding the Securities, and at the same time as common stockholders) participate in any of the
transactions described below as if such Holders held a number of shares of Common Stock equal to
the then-applicable Conversion Rate, multiplied by the principal amount (expressed in thousands) of
Securities held by such Holders, without having to convert their Securities:

(a) In case the Company shall issue shares of Common Stock as a dividend or distribution on
shares of the Common Stock, or the Company shall effect a share split or share combination, the
Conversion Rate shall be adjusted based on the following formula:

CR’ = CR0 x (OS’ / OS0)

where,

CR0 = the Conversion Rate in effect on the record date for such dividend or
distribution or the effective date of such share split or combination, as the case may be;

CR’ = the Conversion Rate in effect immediately after the record date for such
dividend or distribution or immediately after the effective date of such share split or
combination, as the case may be;

OS0 = the number of shares of Common Stock that will be outstanding on the
record date such dividend or distribution or on the effective date of such share split or
combination, as the case may be; and

OS’ = the number of shares of Common Stock outstanding as of the record date for such
dividend or distribution and immediately after giving effect to such dividend or
distribution or immediately after the effective date of such share split or combination, as
the case may be.

Any adjustment made pursuant to this subsection (a) shall become effective on the date that is
immediately after (x) the record date fixed for such dividend or distribution, or (y) the effective
date of such share split or share combination. If any dividend or distribution of the type
described in this Section 1204(a) is declared but not paid or made or the outstanding shares of
Common Stock are not split or combined, as the case may be, the Conversion Rate shall be
readjusted, effective as of the date the Board of Directors determines not to pay such dividend or
distribution, or split or combine the outstanding shares of Common Stock, as the case may be, to
the Conversion Rate that would then be in effect if such dividend, distribution, share split or
share combination had not been declared.

(b) In case the Company shall distribute to all or substantially all holders of Common Stock
any rights or warrants (other than, as described below, rights distributed pursuant to a
shareholder rights plan) entitling them for a period of not more than 45 days after the date of
such distribution to subscribe for or purchase shares of Common Stock at a price per share less
than the average of Last Reported Sale Prices of the Common Stock on the ten Trading Days
immediately preceding the time of announcement of such distribution, the Conversion Rate shall be
adjusted based on the following formula:

CR’ = CR0 x ((OS0 + X) / (OS0 + Y))

where,

CR0 = the Conversion Rate in effect on the record date for such
distribution;

CR’ = the Conversion Rate in effect immediately after the record date for such
distribution;

OS0 = the number of shares of Common Stock outstanding on the record date
for such distribution;

X = the total number of shares of Common Stock issuable pursuant to such rights or
warrants; and

Y = the number of shares of Common Stock equal to the aggregate price payable to
exercise such rights or warrants divided by the average of the Last Reported Sale Prices of
the Common Stock over the 10 consecutive Trading Day period ending on the Trading Day
immediately preceding the date of public announcement for the issuance of such rights and
warrants.

Such adjustment shall be successively made whenever any such rights or warrants are
distributed and shall become effective immediately after the opening of business on the record date
for such distribution. To the extent that shares of Common Stock are not delivered after the
expiration of such rights or warrants, the Conversion Rate shall be readjusted to the Conversion
Rate that would then be in effect had the adjustments made upon the issuance of such rights or
warrants been made on the basis of delivery of only the number of shares of Common Stock actually
delivered. If such rights or warrants are not so issued, the Conversion Rate shall again be
adjusted to be the Conversion Rate that would then be in effect if such record date for such
distribution had not been fixed.

For purposes of this subsection (b), in determining whether any rights or warrants entitle the
holders to subscribe for or purchase shares of Common Stock at less than such Last Reported Sale
Price, and in determining the aggregate exercise or conversion price of such shares of Common
Stock, there shall be taken into account any consideration received by the Company for such rights
or warrants and any amount payable on exercise or conversion thereof, the value of such
consideration, if other than cash, to be determined by the Board of Directors.

(c) In case the Company shall distribute to shares of any class of Capital Stock of the
Company, evidences of its indebtedness or other assets or property of the Company to all or
substantially all holders of Common Stock (but excluding dividends or distributions referred to in
subsection (a) or (b) of this Section 1204, dividends or distributions paid exclusively in cash
referred to in subsection (d) of this Section 1204, and distributions described below in this
subsection (c) with respect to Spin-Offs) (any of such shares of Capital Stock, indebtedness, or
other asset or property hereinafter in this subsection (c) called the “Distributed Property”),
then, in each such case the Conversion Rate shall be adjusted based on the following formula:

CR’ = CR0 x (SP0 / (SP0 – FMV))

where,

CR0 = the Conversion Rate in effect on the record date for such
distribution;

CR’ = the Conversion Rate in effect immediately after the record date for such
distribution;

SP0 = the average of the Last Reported Sale Prices of Common Stock over the
10 consecutive Trading Day period ending on the Trading Day immediately preceding the
Ex-Date for such distribution; and

FMV = the fair market value of the shares of Capital Stock, evidences of indebtedness,
assets or property distributed with respect to each outstanding share of Common Stock on
the Ex-Date for such distribution, as determined by the Board of Directors.

An adjustment to the conversion rate pursuant to this subsection (c) shall become effective on
the record date for such distribution.

With respect to an adjustment pursuant to this subsection (c) where there has been a payment
of a dividend or other distribution to all or substantially all holders of the Common Stock in
shares of Capital Stock of any class or series, or similar equity interest, of or relating to a
Subsidiary or other Company business unit (a “Spin-Off”), the Conversion Rate in effect immediately
before 5:00 p.m., New York City time, on the 10th Trading Day immediately following, and including,
the effective date of the Spin-Off shall be increased based on the following formula:

CR’ = CR0 x ((FMV0 + MP0) / MP0)

where,

CR0 = the Conversion Rate in effect on the 10th Trading Day immediately
following the effective date of the Spin-Off;

CR’ = the Conversion Rate in effect immediately after the 10th Trading Day immediately
following the effective date of the Spin-Off;

FMV0 = the average of the Last Reported Sale Prices of the Capital Stock or
similar equity interest distributed to holders of Common Stock applicable to one share of
Common Stock over the first 10 consecutive Trading Day period immediately following the
effective date of the Spin-Off; and

MP0 = the average of the Last Reported Sale Prices of the Common Stock over
the first 10 consecutive Trading Day period immediately following the effective date of the
Spin-Off.

Such adjustment shall occur on the 10th Trading Day from the effective date of the Spin-Off;
provided that in respect of any conversion within the 10 Trading Days immediately following, and
including, the effective date of any Spin-Off, references in this subsection (c) with respect to
the Spin-Off to 10 Trading Days shall be deemed replaced with such lesser number of Trading Days as
have elapsed between the effective date of such Spin-Off and the Conversion Date in determining the
applicable Conversion Rate.

If any such dividend or distribution described in this subsection (c) is declared but not paid
or made, the Conversion Rate shall be readjusted to be the Conversion Rate that would then be in
effect if such dividend or distribution had not been declared.

Rights or warrants distributed by the Company to all holders of Common Stock, entitling the
holders thereof to subscribe for or purchase shares of the Company’s Capital Stock, including
Common Stock (either initially or under certain circumstances), which rights or warrants, until the
occurrence of a specified event or events (“Trigger Event”): (i) are deemed to be transferred with
such shares of Common Stock; (ii) are not exercisable; and (iii) are also issued in respect of
future issuances of Common Stock, shall be deemed not to have been distributed for purposes of this
Section 1204 (and no adjustment to the Conversion Rate under this Section 1204 shall be required)
until the occurrence of the earliest Trigger Event, whereupon such rights and warrants shall be
deemed to have been distributed and an appropriate adjustment (if any is required) to the
Conversion Rate shall be made under this subsection (c). If any such rights or warrants are subject
to events, upon the occurrence of which such rights or warrants become exercisable to purchase
different securities, evidences of indebtedness or other assets, then the date of the occurrence of
any and each such event shall be deemed to be the date of distribution and record date with respect
to new rights or warrants with such rights (and a termination or expiration of the existing rights
or warrants without exercise by any of the holders thereof). In addition, in the event of any
distribution (or deemed distribution) of rights or warrants, or any Trigger Event or other event
(of the type described in the preceding sentence) with respect thereto that was counted for
purposes of calculating a distribution amount for which an adjustment to the Conversion Rate under
this Section 1204 was made, (1) in the case of any such rights or warrants that shall all have been
redeemed or repurchased without exercise by any holders thereof, the Conversion Rate shall be
readjusted upon such final redemption or repurchase to give effect to such distribution or Trigger
Event, as the case may be, as though it were a cash distribution, equal to the per share redemption
or repurchase price received by a holder or holders of Common Stock with respect to such rights or
warrants (assuming such holder had retained such rights or warrants), made to all holders of Common
Stock as of the date of such redemption or repurchase, and (2) in the case of such rights or
warrants that shall have expired or been terminated without exercise by any holders thereof, the
Conversion Rate shall be readjusted as if such rights and warrants had not been issued.

(d) In case the Company shall pay any cash dividends or distributions to all or substantially
all holders of its Common Stock, the Conversion Rate shall be adjusted based on the following
formula:

CR’ = CR0 x (SP0 / (SP0 – C))

where,

CR0 = the Conversion Rate in effect on the record date for such
distribution;

CR’ = the Conversion Rate in effect immediately after the record date for such
distribution;

SP0 = the Last Reported Sale Price of the Common Stock on the Trading Day
immediately preceding the Ex-Date for such distribution;

C = the amount in cash per share the Company distributes to holders of Common Stock in
such distribution.

Such adjustment shall become effective immediately after the opening of business on the record
date for such dividend or distribution. If any such dividend or distribution is not so paid or
made, the Conversion Rate shall again be adjusted to be the Conversion Rate that would then be in
effect if such dividend or distribution had not been declared.

(e) In case the Company or any of its Subsidiaries make a payment in respect of a tender offer
or exchange offer for Common Stock, to the extent that the cash and value of any other
consideration included in the payment per share of Common Stock exceeds the Last Reported Sale
Price of the Common Stock on the Trading Day next succeeding the last date on which tenders or
exchanges may be made pursuant to such tender or exchange offer (as it may be amended), the
Conversion Rate shall be increased based on the following formula:

CR’ = CR0 x ((AC + (SP’ x OS’)) / (OS0 x SP’))

where,

CR0 = the Conversion Rate in effect on the first day immediately following
the date such tender or exchange offer expires;

CR’ = the Conversion Rate in effect on the second day immediately following the date
such tender or exchange offer expires;

AC = the aggregate value of all cash and any other consideration as determined by the
Board of Directors paid or payable for shares purchased in such tender or exchange offer;

OS0 = the number of shares of Common Stock outstanding immediately prior to
the date such tender or exchange offer expires;

OS’ = the number of shares of Common Stock outstanding immediately after the date such
tender or exchange offer expires (after giving effect to such tender offer or exchange
offer); and

SP’ = the Last Reported Sale Price of Common Stock on the Trading Day next succeeding
the date such tender or exchange offer expires.

Such adjustment shall become effective immediately after close of business on the Trading Day
next succeeding the date such tender or exchange offer expires.

(f) No adjustment to the Conversion Rate shall be made if the application of any of the
formulas set forth in this Section 1204 (other than in connection with a share combination) would
result in a decrease in the Conversion Rate.

For purposes of this Section 1204 the term “Record Date” shall mean, with respect to any
dividend, distribution or other transaction or event in which the holders of Common Stock have the
right to receive any cash, securities or other property or in which the Common Stock (or other
applicable security) is exchanged for or converted into any combination of cash, securities or
other property, the date fixed for determination of shareholders entitled to receive such cash,
securities or other property (whether such date is fixed by the Board of Directors or by statute,
contract or otherwise).

In addition to any increases to the Conversion Rate required by subsections (a), (b), (c),
(d), and (e) of this Section 1204, and to the extent permitted by applicable law and the rules of
the New York Stock Exchange or any other securities exchange on which the Common Stock is then
listed, the Company from time to time may increase the Conversion Rate by any amount for a period
of at least 20 calendar days if the Board of Directors determines that such increase would be in
the Company’s best interest. Whenever the Conversion Rate is increased pursuant to the preceding
sentence, the Company shall mail to the Holder of each Security at his last address appearing on
the register provided for in Section 701 and the Trustee a notice of the increase at least 15
calendar days prior to the date the increased Conversion Rate takes effect, and such notice shall
state the increased Conversion Rate and the period during which it will be in effect. In addition,
the Company may also (but is not required to) increase the Conversion Rate to avoid or diminish any
income tax to holders of Common Stock or rights to purchase Common Stock in connection with any
dividend or distribution of shares (or rights to acquire shares) or similar event.

(g) Without limiting the foregoing, no adjustment to the Conversion Rate will be made:

(i) upon the issuance of any shares of Common Stock pursuant to any present or future
plan providing for the reinvestment of dividends or interest payable on securities of the
Company and the investment of additional optional amounts in shares of Common Stock under
any plan;

(ii) upon the issuance of any shares of Common Stock or options or rights to purchase
or acquire shares of Common Stock pursuant to any present or future employee, director or
consultant benefit plan or program of or assumed by the Company or any of its Subsidiaries;

(iii) except as stated in this Indenture, upon the issuance of any shares of Common
Stock or any securities convertible into or exchangeable for any shares of Common Stock or
the right to purchase shares of Common Stock or such convertible or exchangeable
securities;

(iv) upon the issuance of any shares of Common Stock pursuant to any option, warrant,
right, or exercisable, exchangeable or convertible security not described in clause (ii)
above and outstanding as of the date of this Indenture;

(v) for a change in the par value of the Common Stock; or

(vi) for accrued and unpaid interest.

(vii) All calculations and other determinations under this Article shall be made by
the Company and shall be made to the nearest cent or to the nearest one-ten thousandth
(1/10,000) of a share, as the case may be.

(h) In any case in which this Section 1204 provides that an adjustment shall become effective
immediately after (1) the Record Date for an event or (2) the last date on which tenders or
exchanges may be made pursuant to any tender or exchange offer pursuant to subsection (e) of this
Section (each an “Adjustment Determination Date”), the Company may elect to defer until the
occurrence of the applicable Adjustment Event (as hereinafter defined) (x) issuing to the Holder of
any Note converted after such Adjustment Determination Date and before the occurrence of such
Adjustment Event, the additional shares of Common Stock or other securities issuable upon such
conversion by reason of the adjustment required by such Adjustment Event over and above the amounts
deliverable upon such conversion before giving effect to such adjustment and (y) paying to such
Holder any amount in cash in lieu of any fraction pursuant to Section 1203. For purposes of this
subsection (h), the term “Adjustment Event” shall mean:

(i) in any case referred to in clause (1) hereof, the date any dividend or
distribution of Common Stock, shares of Capital Stock, evidences of indebtedness, other
assets or property or cash is paid or made, the effective date of any share split or
combination or the date of expiration of any rights or warrants, and

(ii) in any case referred to in clause (2) hereof, the date a sale or exchange of
Common Stock pursuant to such tender or exchange offer is consummated and becomes
irrevocable.

(i) For purposes of this Section 1204, the number of shares of Common Stock at any time
outstanding shall not include shares held in the treasury of the Company but shall include shares
issuable in respect of scrip certificates issued in lieu of fractions of shares of Common Stock.

(j) For the avoidance of doubt, if a Holder converts Securities prior to the Effective Date of
a Make-Whole Fundamental Change, and the Fundamental Change does not occur, the Holder shall not be
entitled to Additional Shares in connection with such conversion.

(k) With respect to a conversion of Securities pursuant to this Article, at and after the
close of business on the Conversion Date (each such day the “Relevant Date”), the Person in whose
name any certificate representing any shares of Common Stock issuable upon such conversion is
registered shall be treated as a stockholder of record of the Company on such Relevant Date;
provided, however, that if any such shares of Common Stock constitute Additional Shares, then the
Relevant Date with respect to such shares that constitute Additional Shares shall instead be deemed
to be the later of (i) the Conversion Date and (ii) the Effective Date of the Fundamental Change
resulting in the Additional Shares. On and after the Conversion Date with respect to a conversion
of Securities pursuant hereto, all rights of the Holders of such Securities shall terminate, other
than the right to receive the consideration deliverable upon conversion of such Securities as
provided herein. A Holder of a Note is not entitled, as such, to any rights of a holder of Common
Stock until, if such Holder converts such Note and is entitled pursuant hereto to receive shares of
Common Stock in respect of such conversion, the close of business on the Relevant Date or
respective Relevant Dates, as the case may be, with respect to such conversion.

(l) Notwithstanding the foregoing, no adjustment to the Conversion Rate will be required
unless the adjustment would require an increase or decrease of at least 1% of the Conversion Rate.
However, the Company will carry forward any adjustments that are less than 1% of the Conversion
Rate that the Company elects not to make and make them upon the earliest of (1) any conversion of
Securities upon a Fundamental Change, (2) such time as all adjustments that have not been made
prior thereto would have the effect of adjusting the Conversion Rate by at least 1%, and (3) each
applicable day from and including the 25th scheduled Trading Day prior to the Maturity Date and (4)
each anniversary of the first date of issuance of the Securities.

	 	 	SECTION 1205. Notice of Adjustments of Conversion Rate.

Whenever the Conversion Rate is adjusted as herein provided:

(a) the Company shall compute the adjusted Conversion Rate in accordance with Section 1204 and
shall prepare a certificate signed by the Chief Financial Officer of the Company setting forth the
adjusted Conversion Rate and showing in reasonable detail the facts upon which such adjustment is
based, and such certificate shall promptly be filed with the Trustee and with each Conversion Agent
(if other than the Trustee); and

(b) upon each such adjustment, a notice stating that the Conversion Rate has been adjusted and
setting forth the adjusted Conversion Rate shall be required, such notice shall be provided by the
Company to all Holders in accordance with Section 106.

Neither the Trustee nor any Conversion Agent shall be under any duty or responsibility with
respect to any such certificate or the information and calculations contained therein, except to
exhibit the same to any Holder of Securities desiring inspection thereof at its office during
normal business hours.

	 	 	SECTION 1206. Company to Reserve Common Stock.

The Company shall at all times reserve and keep available, free from preemptive rights, out of
its authorized but unissued Common Stock, for the purpose of effecting the conversion of
Securities, the full number of shares of Common Stock then issuable upon the conversion of all
Outstanding Securities.

	 	 	SECTION 1207. Taxes on Conversions.

Except as provided in the next sentence, the Company shall pay all documentary, stamp or
similar issue or transfer tax due that may be payable in respect of the issue or delivery of shares
of Common Stock on conversion of Securities pursuant hereto. The Company shall not, however, be
required to pay any tax or duty that may be payable in respect of (i) income of the Holder, or (ii)
any transfer involved in the issue and delivery of shares of Common Stock in a name other than that
of the Holder of the Security or Securities to be converted, and no such issue or delivery shall be
made unless and until the Person requesting such issue has paid to the Company the amount of any
such tax or duty, or has established to the satisfaction of the Company that such tax or duty has
been paid.

	 	 	SECTION 1208. Certain Covenants.

Before taking any action which would cause an adjustment reducing the Conversion Rate below
the then par value, if any, of the shares of Common Stock issuable upon conversion of the
Securities, the Company shall take all corporate action which it reasonably determines may be
necessary in order that the Company may validly and legally issue shares of such Common Stock at
such adjusted Conversion Rate.

The Company covenants that all shares of Common Stock issued upon conversion of Securities
shall be fully paid and non-assessable by the Company and free from all taxes, liens and charges
with respect to the issue thereof.

The Company further covenants that if at any time the Common Stock shall be listed for trading
on any other national securities exchange the Company shall, if permitted and required by the rules
of such exchange, list and keep listed, so long as the Common Stock shall be so listed on such
exchange, all Common Stock issuable upon conversion of the Securities.

	 	 	SECTION 1209. Cancellation of Converted Securities.

All Securities surrendered for the purpose of payment, repurchase, conversion or registration
of transfer, shall, if surrendered to the Company or any Paying Agent or any Security Registrar, be
surrendered to the Trustee and promptly canceled by it, or, if surrendered to the Trustee, shall be
promptly canceled by it, and no Securities shall be issued in lieu thereof except as expressly
permitted by any of the provisions of this Indenture. The Trustee shall dispose of canceled
Securities in accordance with its customary procedures and shall promptly provide copies of all
cancelled certificates to the Company. If the Company shall acquire any of the Securities, such
acquisition shall not operate as satisfaction of the debt represented by such Securities unless and
until the same are delivered to the Trustee for cancellation.

	 	 	SECTION 1210. Provision in Case of Effect of Reclassification, Consolidation, Merger or
Sale.

If any of the following events occur, namely (i) any Fundamental Change described in clause
(2) of the definition of Fundamental Change, (ii) any reclassification or change of the outstanding
shares of Common Stock (other than a change in par value, or from par value to no par value, or
from no par value to par value, or as a result of a split, subdivision or combination), (iii) any
consolidation, binding share exchange, recapitalization, reclassification, merger, combination or
other similar event of the Company with another Person or (iv) any sale, transfer or conveyance of
all or substantially all of the property and assets of the Company to any other Person, in each
case as a result of which holders of Common Stock shall be entitled to receive cash, securities or
other property or assets with respect to or in exchange for such Common Stock (any such event
described in clauses (i) through (iv) a “Merger Event”), then:

(a) the Company or the successor or purchasing Person, as the case may be, shall execute with
the Trustee a supplemental indenture (which shall comply with the Trust Indenture Act as in force
at the date of execution of such supplemental indenture if such supplemental indenture is then
required to so comply) permitted under Section 901(5) providing for the conversion and settlement
of the Securities as set forth in this Indenture. Such supplemental indenture shall provide for
adjustments which shall be as nearly equivalent as may be practicable to the adjustments provided
for in this Article and the Trustee may conclusively rely on the determination by the Company of
the equivalency of such adjustments. If, in the case of any Merger Event, the Reference Property
includes shares of stock or other securities and assets of a company other than the successor or
purchasing company, as the case may be, in such change of control, consolidation, binding share
exchange, recapitalization, reclassification, merger, combination, sale, transfer or conveyance or
Fundamental Change described in clause (2) of the definition of Fundamental Change, then such
supplemental indenture shall also be executed by such other company and shall contain such
additional provisions to protect the interests of the Holders of the Securities as the Board of
Directors shall reasonably consider necessary by reason of the foregoing.

In the event a supplemental indenture is executed pursuant to this Section 1210, the Company
shall promptly file with the Trustee an Officers’ Certificate briefly stating the reasons
therefore, the kind or amount of cash, securities or property or assets that will constitute the
Reference Property after any such Merger Event, any adjustment to be made with respect thereto and
that all conditions precedent have been complied with, and shall promptly mail notice thereof to
all Holders.

If any securities to be provided for the purpose of conversion of Securities hereunder require
registration with or approval of any governmental authority under any federal or state law before
such securities may be validly issued upon conversion, each supplemental indenture executed
pursuant to this Section shall provide that the Company or the successor or the purchasing Person,
as the case may be, or if the Reference Property includes shares of stock or other securities and
assets of a company other than the successor or purchasing company, as the case may be, then such
company, shall use all commercially reasonable efforts, to the extent then permitted by the rules
and interpretations of the SEC (or any successor thereto), to secure such registration or approval
in connection with the conversion of Securities.

(b) Notwithstanding the provisions of Section 1202(a) to (b), and subject to the provisions of
Section 1201, at the effective time of such Merger Event, the right to convert each $1,000
principal amount of Securities shall be changed to a right to convert such Securities by reference
to the kind and amount of cash, securities or other property or assets that a holder of a number of
shares of Common Stock equal to the Conversion Rate immediately prior to such transaction would
have owned or been entitled to receive (the “Reference Property”). For purposes of determining the
constitution of Reference Property, the type and amount of consideration that a holder of Common
Stock would have been entitled to in the case of changes of control, consolidations, binding share
exchanges, recapitalizations, reclassifications, mergers, combinations, sales or transfers of
assets or Fundamental Changes described in clause (2) of the definition of Fundamental Change or
other transactions that cause the Common Stock to be converted into the right to receive more than
a single type of consideration (determined, based in part upon any form of stockholder election)
shall be deemed to be the (i) weighted average of the types and amounts of consideration received
by the holders of Common Stock that affirmatively make such an election or (ii) if no holders of
Common Stock affirmatively make such election, the types and amounts of consideration actually
received by such holders. None of the foregoing provisions shall affect any right of a Holder of
Securities to convert its Securities in accordance with the provisions of this Article prior to the
effective date.

(c) The Company shall cause notice of the execution of a supplemental indenture required by
this Section 1210 to be mailed to each Holder, at his address appearing on the register provided
for in Section 701, or by such other means reasonably acceptable to such Holder, within 20 calendar
days after execution thereof. Failure to deliver such notice shall not affect the legality or
validity of such supplemental indenture.

(d) The above provisions of this Section shall similarly apply to successive Merger Events.

	 	 	SECTION 1211. Responsibility of Trustee for Conversion Provisions.

The Trustee and any Conversion Agent shall not at any time be under any duty or responsibility
to any Holder of Securities to determine whether any facts exist which may require any adjustment
of the Conversion Rate, or with respect to the nature or extent of any such adjustment when made,
or with respect to the method employed, herein or in any supplemental indenture provided to be
employed, in making the same, or whether a supplemental indenture need be entered into. Neither the
Trustee nor any Conversion Agent shall be accountable with respect to the validity or value (or the
kind or amount) of any Common Stock, or of any other securities or property or cash, which may at
any time be issued or delivered upon the conversion of any Securities; and it or they do not make
any representation with respect thereto. Neither the Trustee nor any Conversion Agent shall be
responsible for any failure of the Company to make or calculate any cash payment or to issue,
transfer or deliver any shares of Common Stock or share certificates or other securities or
property or cash upon the surrender of any Note for the purpose of conversion; and the Trustee and
any Conversion Agent shall not be responsible for any failure of the Company to comply with any of
the covenants of the Company contained in this Article.

	 	 	SECTION 1212. Right to Set-off Withholding Taxes.

The Company may, at its option, set-off withholding taxes due with respect to Securities
against delivery of Common Stock on the Securities. In the case of any such set-off against Common
Stock delivered upon conversion of the Notes, such Common Stock shall be valued based on the
arithmetic average of the Trading Price of the Common Stock in the 5 Trading Days immediately
preceding the conversion.

This instrument may be executed in any number of counterparts, each of which so executed shall
be deemed to be an original, but all such counterparts shall together constitute but one and the
same instrument.

3

IN WITNESS WHEREOF, the parties hereto have caused this Indenture to be duly executed
as of the day and year first above written.

USEC INC.

By: /s/ John C. Barpoulis

Name: John C. Barpoulis

Title: Senior Vice President &

Chief Financial Officer

WELLS FARGO BANK, N.A.,

as Trustee

By: /s/ Joseph P. O’Donnell

Name: Joseph P. O’Donnell

Title: Vice President

4

Schedule A

	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 
	 	 	Make-whole Reference Date
	Stock

Price

	 	

Sept- 24-07
	 	

1-Oct-08
	 	

1-Oct-09
	 	

1-Oct-10
	 	

1-Oct-11
	 	

1-Oct-12
	 	

1-Oct-13
	 	

1-Oct-14

	$9.76

	 	 	18.8190	 	 	 	18.6104	 	 	 	18.3468	 	 	 	18.1478	 	 	 	17.9674	 	 	 	17.7831	 	 	 	17.5062	 	 	 	18.8190	 
	$10.50

	 	 	16.6974	 	 	 	16.4533	 	 	 	16.0523	 	 	 	15.6520	 	 	 	15.1774	 	 	 	14.5381	 	 	 	13.4454	 	 	 	11.5981	 
	$12.00

	 	 	13.5384	 	 	 	13.1546	 	 	 	12.5935	 	 	 	11.9552	 	 	 	11.1352	 	 	 	9.9764	 	 	 	8.0107	 	 	 	0.0000	 
	$13.50

	 	 	11.2676	 	 	 	10.8217	 	 	 	10.1962	 	 	 	9.4582	 	 	 	8.4981	 	 	 	7.1504	 	 	 	4.9680	 	 	 	0.0000	 
	$15.00

	 	 	9.5731	 	 	 	9.1074	 	 	 	8.4688	 	 	 	7.7058	 	 	 	6.7150	 	 	 	5.3502	 	 	 	3.2685	 	 	 	0.0000	 
	$16.50

	 	 	8.2691	 	 	 	7.8068	 	 	 	7.1825	 	 	 	6.4337	 	 	 	5.4685	 	 	 	4.1690	 	 	 	2.3082	 	 	 	0.0000	 
	$18.00

	 	 	7.2394	 	 	 	6.7930	 	 	 	6.1968	 	 	 	5.4823	 	 	 	4.5695	 	 	 	3.3693	 	 	 	1.7507	 	 	 	0.0000	 
	$20.00

	 	 	6.1666	 	 	 	5.7504	 	 	 	5.2007	 	 	 	4.5447	 	 	 	3.7173	 	 	 	2.6607	 	 	 	1.3304	 	 	 	0.0000	 
	$22.50

	 	 	5.1555	 	 	 	4.7818	 	 	 	4.2928	 	 	 	3.7136	 	 	 	2.9935	 	 	 	2.1020	 	 	 	1.0471	 	 	 	0.0000	 
	$25.00

	 	 	4.3902	 	 	 	4.0578	 	 	 	3.6259	 	 	 	3.1181	 	 	 	2.4943	 	 	 	1.7398	 	 	 	0.8794	 	 	 	0.0000	 
	$35.00

	 	 	2.5916	 	 	 	2.3859	 	 	 	2.1203	 	 	 	1.8158	 	 	 	1.4496	 	 	 	1.0215	 	 	 	0.5402	 	 	 	0.0000	 
	$50.00

	 	 	1.3969	 	 	 	1.2901	 	 	 	1.1488	 	 	 	0.9905	 	 	 	0.7975	 	 	 	0.5693	 	 	 	0.3044	 	 	 	0.0000	 
	$75.00

	 	 	0.5786	 	 	 	0.5376	 	 	 	0.4782	 	 	 	0.4139	 	 	 	0.3306	 	 	 	0.2318	 	 	 	0.1216	 	 	 	0.0000	 
	$100.00

	 	 	0.2348	 	 	 	0.2187	 	 	 	0.1908	 	 	 	0.1633	 	 	 	0.1234	 	 	 	0.0749	 	 	 	0.0321	 	 	 	0.0000	 

0

5EX-10.1

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

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