PUT OPTION AGREEMENT

EXHIBIT 10.3

PUT OPTION AGREEMENT

     This PUT OPTION AGREEMENT (this “ Agreement ”) is made and entered into on October 13, 2006 (the “ Effective Date ”), between Nuclear Energy Holdings, L.L.C., a Delaware limited liability company (“ NEH ”), and Toshiba Corporation, a Japanese corporation (“ Toshiba ”). NEH and Toshiba are also referred to herein together as the “ Parties ” and individually as a “ Party ”.

RECITALS

     A. Subject to the terms and conditions set forth in an Investment Agreement, dated as of October 4, 2006, among Toshiba, NEH and The Shaw Group Inc., NEH has directly agreed to acquire 280 shares of Class A Stock of TOSHIBA NUCLEAR ENERGY HOLDINGS (UK) LIMITED , a company incorporated in England (“ UK HoldCo ”), for a consideration of $280,000,000 and representing, as of the Effective Date, twenty percent (20.0%) of the outstanding shares in the capital of UK HoldCo (the “ Shares ”).

     B. On or about the date of this Agreement, NEH proposes to issue up to JPY50,980,000,000 aggregate principal amount of 2.20% Fixed Rate Bonds due 2013 and JPY78,000,000,000 aggregate principal amount of Floating Rate Bonds due 2013 (the “ Bonds ”), the proceeds of which will be used to fund the acquisition of the Shares by NEH. NEH’s obligations with respect to the Notes will be secured in favor of the holders of the Notes, inter alia , by a security assignment of NEH’s rights, title and interest under this Agreement and a pledge, charge or other security interest over the Shares.

     C. It is a condition to NEH’s agreement to directly acquire the Shares that Toshiba provide a put option with respect to the Shares, on the terms and conditions set forth herein.

     NOW, THEREFORE, the Parties, in consideration of the foregoing premises and the terms, covenants and conditions set forth below, hereby agree as follows:

AGREEMENT

1. DEFINITIONS; INTERPRETATION.

     1.1. Terms Defined in this Agreement . The following terms when used in this Agreement shall have the following definitions:

     “ Bankruptcy Law ” means any Law of any jurisdiction relating to bankruptcy, insolvency, corporate reorganization, company arrangement, civil rehabilitation, special liquidation, moratorium, readjustment of debt, appointment of a conservator ( hozen kanrinin ), trustee ( kanzai nin ), supervisor ( kantoku i’in ), inspector ( chousa i’in ), or receiver, or similar debtor relief, including hasan under Hasan Ho (law No. 75, 2004 as amended) , minji saisei under Minji Saisei Ho (law No. 225, 1999 as amended) , kaisha kousei under Kaisha Kousei Ho (law No. 154, 2000 as amended) , tokubetsu seisan under Kaisha Ho (law No. 86, 2005 as amended) and tokutei choutei under Tokuteisaimuto no Chosei no Sokushin no tameno Tokuteichoutei ni kansuru Houritsu (law No.158, 1999 as amended).

     “ Business Day ” means any day other than those that are bank holidays in Tokyo.

     “ Competitor ” means any Person who by itself or through or together with any of its Subsidiaries, is substantially engaged in the provision of nuclear power plant technology and/or nuclear fuel supply.

     “ Consolidated Net Worth ” means, as of any date, total shareholders’ equity, being the sum of stated capital, additional paid-in capital, legal reserves and retained earnings less any treasury stock, which would appear on a consolidated balance sheet of Toshiba and its consolidated Subsidiaries as of such date in accordance with US GAAP; provided that for the purpose of calculating Consolidated Net Worth, the effect, if any, of all GAAP Statement of Financial Accounting Standards No. 87 pension-related non-cash charge shall be excluded;

     “ Debt-to-Equity Ratio ” means ratio of total Financial Debt to Consolidated Net Worth.

     “ Financial Debt ” means every obligation for money borrowed or evidenced by notes, bonds, debentures, security instruments and other similar instruments which incur interest expense and which would, in accordance with US GAAP, be shown on a consolidated balance sheet of Toshiba.

     “ Government Authority ” means any: (a) nation, principality, state, commonwealth, province, territory, county, municipality, district or other jurisdiction of any nature; (b) federal, state, local, municipal, foreign or other government; (c) governmental or quasi governmental authority of any nature (including any governmental division, subdivision, department, agency, bureau, branch, office, commission, council, board, instrumentality, officer, official, representative, organization, unit, body or Person and any court or other tribunal); or (d) individual, Person or body exercising, or entitled to exercise, any executive, legislative, judicial, administrative, regulatory, police, military or taxing authority or power of any nature.

     “ JPY ” means Japanese Yen.

     “ Law ” means any federal, state, local, municipal, foreign or other law, statute, legislation, constitution, principle of common law, resolution, ordinance, code, order, edict, decree, proclamation, treaty, convention, rule, regulation, permit, ruling, directive, pronouncement, requirement (licensing or otherwise), specification, determination, decision, opinion or interpretation that is, has been or may in the future be issued, enacted, adopted, passed, approved, promulgated, made, implemented or otherwise put into effect by or under the authority of any Government Authority.

     “ Person ” means any individual, firm, company, corporation, limited liability company, unincorporated association, partnership, trust, joint venture, governmental authority or other entity, and shall include any successor (by merger or otherwise) of such entity.

     “ Put Price ” means, with respect to any exercise of the Put Option, the per Share price, expressed in Japanese Yen, of any Share subject to any Put Exercise Notice (as defined in Section 2.3). The Put Price:

     (a) for each Share subject to the Put Exercise Notice up to and including sixty-seven percent (67%) of the Shares shall be JPY119,425,926 per Share; and

     (b) for each Share subject to the Put Exercise Notice in excess of sixty-seven percent (67%) of the Shares shall be the product of (x) JPY119,425,926 per Share multiplied by (y) 0.90; provided that, in the event that a Put Exercise Notice is delivered by NEH following the occurrence of a Toshiba Event, the number in the foregoing clause (y) shall be 1.00.

     “ Subsidiary ” means a Person (other than an individual) (a) more than fifty percent (50%) of whose outstanding shares or securities (representing the right to vote for the election of directors or other managing authority) are, now or hereafter, owned or controlled, directly or indirectly, by another Person; or (b) which does not have outstanding shares or securities, as may be the case in a partnership, joint venture or unincorporated association, but more than fifty percent (50%) of whose ownership interest representing the right to make the decisions for such corporation, company or other entity is, now or hereafter, owned or controlled, directly or indirectly, by another Person.

     “ Toshiba Event ” means any of the following:

     (a) Toshiba shall fail to have a minimum Consolidated Net Worth of JPY800,000,000,000;

     (b) Toshiba’s Debt-to-Equity Ratio (determined quarterly based on Toshiba’s consolidated quarterly financial statements) shall exceed 2.4 to 1.0;

     (c) Toshiba generally becomes unable to pay its debts as such debts become due ( shiharai funou ), admits to a creditor its inability to pay its debts generally as such debts become due ( shiharai teishi ) or makes a general assignment or settlement for the benefit of creditors ( nin’i seiri );

     (d) a petition (i) for the commencement of a proceeding against Toshiba under any applicable Bankruptcy Law or similar law now or hereafter in effect, (ii) for the appointment of a receiver, liquidator, assignee, custodian, trustee, sequestrator, conservator ( hozen kanrinin ), trustee ( kanzai nin ), supervisor ( kantoku i’in ), inspector ( chousa i’in ) or similar official of all or for any substantial part of Toshiba’s property, or (iii) for the winding up or liquidation of Toshiba’s affairs, is filed by any third party other than Toshiba;

     (e) Toshiba files a petition for the commencement of a proceeding under any applicable Bankruptcy Law or similar law now or hereafter in effect, or consents to or makes no objection against the filing of or the entry of an order for relief in an involuntary proceeding under any such law, or applies for, consents to or otherwise acquiesces in the appointment of or taking possession by a receiver, liquidator, assignee, custodian, sequestrator, conservator ( hozen kanrinin ), trustee ( kanzai nin ), supervisor ( kantoku i’in ), inspector ( chosa i’in ) or similar official of Toshiba of all or any substantial part of the property thereof, or makes any general assignment or settlement for the benefit of the creditors thereof;

     (f) Toshiba’s assets, such as its bank accounts, are subject to the issuance of an order or a notice of provisional attachment ( kari sashiosae ), temporary attachment order ( hozen sashiosae ) or permanent attachment ( sashiosae ), and, with respect to a provisional attachment and temporary attachment order only, such attachment or order remains unstayed and in effect for a period of thirty (30) consecutive days;

     (g) Toshiba ceases, or through an official action of its board of directors threatens to cease, to carry on all or substantially all of its business;

     (h) the clearing house takes procedures for suspension of Toshiba’s transactions with banks or other financial institutions ( torihiki teishi shobun );

     (i) Toshiba has materially breached any of its covenants herein, and does not cure such breach within 30 days after notice from NEH advising Toshiba of such breach; or

     (j) the receipt by NEH of a notice of acceptance or any other similar notice delivered by Toshiba or any Shareholder(s) (as defined in either Shareholders Agreement (defined herein)) obligating Toshiba or such Shareholder(s) to purchase, and obligating NEH to sell, all or any portion of (i) the Shares pursuant to, and in accordance with, Section 7.06 of the Shareholders Agreement dated October 4, 2006, among Toshiba, NEH, UK HoldCo, and its other shareholders (the “ UK Shareholders Agreement ”), or (ii) the shares owned by NEH in Toshiba Nuclear Energy Holdings (US) Inc., a Delaware corporation (“ US HoldCo ” and, together with UK HoldCo, the “ HoldCos ”), pursuant to, and in accordance with, Section 7.06 of the Shareholders Agreement dated October 4, 2006, among Toshiba, NEH, US HoldCo, and its other shareholders (the “ US Shareholders Agreement ”; and, together with the UK Shareholders Agreement, the “ Shareholders Agreements ”) (such notice, a “ Call Option Exercise Notice ”).

     “ US GAAP ” means generally accepted accounting principles in the United States as in effect on the date of application thereof.

1.2. Interpretation .

     (a)  Certain Terms . The words “hereof,” “herein,” “hereunder” and similar words refer to this Agreement as a whole and not to any particular provision of this Agreement. The term “including” is not limited and means “including without limitation.”

     (b)  Section References; Titles and Subtitles . Unless otherwise noted, all references to Sections herein are to Sections of this Agreement. The titles, captions and headings of this Agreement are inserted for convenience of reference only and are not intended to be a part of or to affect the meaning or interpretation of this Agreement.

     (c)  Reference to Entities, Agreements, Statutes . Unless otherwise expressly provided herein, (i) references to a Person include its successors and permitted assigns, (ii) references to agreements (including this Agreement) and other contractual instruments shall be deemed to include all subsequent amendments, restatements and other modifications thereto or supplements thereof and (iii) references to any statute or regulation are to be

construed as including all statutory and regulatory provisions consolidating, amending, replacing, supplementing or interpreting such statute or regulation.

2. PUT RIGHT.

     2.1. Put Right . NEH shall have the right and option to sell to Toshiba or its permitted assignee, and upon the exercise of such right and option Toshiba or its permitted assignee shall have the obligation to purchase from NEH, all of the Shares identified in the Put Exercise Notice (as defined below) (the “ Put Right ”). NEH and Toshiba hereby agree that the Put Right may be exercised by NEH on one occasion only.

     2.2. Put Period . The Put Right shall be exercisable by NEH by delivering a Put Exercise Notice (defined below) at any time during the period (the “ Exercise Period ”) commencing on (and including) the earlier of (i) March 31, 2010 and (ii) the occurrence of a Toshiba Event, and ending on the earlier of (x) the date that is 30 days after receipt by NEH of the consolidated financial statements (prepared in accordance with US GAAP) of the HoldCos for the period ending September 30, 2012 and (y) February 28, 2013 (such earlier date, the “ Exercise Period End Date ”). For the avoidance of doubt, if the Put Exercise Notice is not delivered on or before the Exercise Period End Date, the Exercise Period shall automatically expire, and the Put Right shall thereafter be of no further force or effect, at 11:59:59 p.m. on Exercise Period End Date. Once the Put Right is exercised, NEH shall have no Put Right on the remaining Shares, if any.

     2.3. Exercise Process . In order to exercise the Put Right during the Exercise Period, NEH shall deliver to Toshiba a written notice of such exercise substantially in the form attached hereto as Appendix A (a “ Put Exercise Notice ”) to such address and marked for such attention as is specified in Section 5.4. The Put Exercise Notice shall indicate the number of Shares as to which NEH is then exercising its Put Right, the aggregate Put Price and the closing date for the purchase (the “ Put Closing Date ”), which date shall be 90 days after the date on which the Put Exercise Notice is first delivered by NEH to Toshiba; provided that, in the event that a Toshiba Event (other than a Toshiba Event described in clause (j) of the definition thereof) has occurred, such date shall be 30 days after the date on which the Put Exercise Notice is delivered by NEH, in each case subject to Section 2.5. For the avoidance of doubt, the date of exercise of the Put Right shall be earlier of (a) the date upon which Toshiba receives such Put Exercise Notice and (b) two Business Days after NEH sends such Put Exercise Notice by internationally recognized courier service subject to next-day or second-day delivery. Where the Put Closing Date would otherwise fall on a day that is not a Business Day, the Put Closing Date shall be the next following Business Day falling thereafter.

     2.4. Put Price . If the Put Right is exercised pursuant to this Section 2, as payment for the Shares to be purchased by Toshiba pursuant to the Put Right, on the Put Closing Date Toshiba shall pay the aggregate Put Price to NEH, or to the order of NEH, by electronic transfer of immediately available funds to a financial institution and account number specified by NEH to Toshiba as soon as practicable prior to the Put Closing Date.

     2.5. Sale of Shares .

          (a) Against payment of the Put Price by Toshiba, and as soon as practicable thereafter, NEH shall sell and deliver to Toshiba (or

its designee), and Toshiba (or its designee) shall receive and purchase from NEH, the Shares as to which NEH is exercising the Put Right. In connection therewith, NEH shall (i) deliver to Toshiba or its designee certificates representing the Shares and a duly executed stock transfer form in respect thereof transferring the Shares to Toshiba (or its designee), (ii) deliver