JOINDER AND REAFFIRMATION AGREEMENT

Exhibit 4.3

Execution Version

JOINDER AND REAFFIRMATION AGREEMENT

This JOINDER AND REAFFIRMATION AGREEMENT (as amended, restated, supplemented or otherwise modified from time to time, this “Agreement”) dated as of August 6, 2010 among THE BABCOCK & WILCOX COMPANY, a Delaware corporation (the “New Borrower”), BABCOCK & WILCOX INVESTMENT COMPANY, a Delaware corporation (the “Original Borrower”), BABCOCK & WILCOX INDIA HOLDINGS, INC., a Delaware corporation (the “New Subsidiary” and, together with the Original Borrower, the “New Guarantors” and, together with the New Borrower, the “New Loan Parties”), the other Guarantors party hereto and BANK OF AMERICA, N.A., in its capacity as Administrative Agent (the “Administrative Agent”) under that certain Credit Agreement, dated as of May 3, 2010 (as amended, restated, supplemented or otherwise modified from time to time, the “Credit Agreement”), among the Borrower, the Lenders party thereto, the Administrative Agent, the Swing Line Lender and each L/C Issuer (each as defined therein). All capitalized terms used and not defined herein shall have the meanings given thereto in the Credit Agreement or the applicable Loan Document referred to herein.

The Original Borrower has informed the Administrative Agent that the consummation of the Spinoff occurred on July 30, 2010.

Accordingly, pursuant to Section 6.24 of the Credit Agreement, the New Loan Parties and the other Guarantors hereby agree as follows:

1. Joinder as the Borrower. The New Borrower, by execution of this Agreement, hereby represents, warrants, acknowledges and agrees that:

(a) from and after the effective time of the consummation of the Spinoff (i) the New Borrower, as provided in Section 6.24 of the Credit Agreement, is and shall be the Borrower (as defined in the Credit Agreement) under the Credit Agreement as if a signatory thereof on the Closing Date, in substitution of the Original Borrower, and (ii) each reference to the “Borrower” in the Credit Agreement and the other Loan Documents shall be a reference to the New Borrower as described in clause(b) of the definition of Borrower in the Credit Agreement;

(b) as the Borrower, it shall comply with, and be subject to, and have the benefit of, all of the terms, conditions, covenants, agreements and obligations set forth in the Credit Agreement; and

(c) each of the representations and warranties of (i) the Borrower contained in Article V of the Credit Agreement and (ii) each Loan Party contained in each other Loan Document, is true and correct in all material respects on and as of the date hereof, except to the extent that such representations and warranties specifically refer to an earlier date, in which case they are true and correct in all material respects as of such earlier date, and except that the representations and warranties contained in subsections (a) and (b) of Section 5.04 of the Credit Agreement shall be deemed to refer to the most recent statements furnished pursuant to clauses (a) and (b), respectively, of Section 6.01 of the Credit Agreement.

2. Joinder as a Guarantor. Each New Guarantor, by execution of this Agreement, hereby represents, warrants, acknowledges and agrees that:

(a) from and after the date hereof (i) it is a Guarantor (as defined in the Guaranty), as provided in Section 19 of the Guaranty, under the Guaranty as if a signatory thereof on the Closing Date, and (ii) each reference to a “Guarantor” or the “Guarantors” in the Guaranty and the other Loan Documents shall include such New Guarantor as a “Guarantor”;

(b) it shall comply with, and be subject to, and have the benefit of, all of the terms, conditions, covenants, agreements and obligations set forth in the Guaranty; and

(c) each of the representations and warranties of such Guarantor contained in the Guaranty, in the Collateral Agreement or in any other Loan Document is true and correct in all material respects on and as of the date hereof, except to the extent that such representations and warranties specifically refer to an earlier date, in which case they are true and correct in all material respects as of such earlier date.

Without limiting the generality of the foregoing terms of this paragraph 2, each New Guarantor hereby, jointly and severally together with the other Guarantors, guarantees to the Administrative Agent, for the benefit of the Guaranteed Parties, to the extent provided in Section 2 of the Guaranty, the prompt payment and performance of the Guaranteed Obligations in full when due (whether at stated maturity, as a mandatory prepayment, by acceleration or otherwise) strictly in accordance with the terms of the Guaranty.

3. Joinder as a Grantor. Each of the New Subsidiary and the New Borrower (together, the “New Grantors”), by execution of this Agreement, hereby represents, warrants, acknowledges and agrees that:

(a) from and after the date hereof (i) it is a Grantor (as defined in the Collateral Agreement), as provided in Section 7.12 of the Collateral Agreement, under the Collateral Agreement as if a signatory thereof on the Closing Date, (ii) each reference to a “Grantor” or the “Grantors” in the Collateral Agreement and the other Loan Documents shall include such New Grantor, and (iii) each reference to the “Collateral” in the Collateral Agreement and the other Loan Documents shall include all Collateral (as defined in the Collateral Agreement) of each New Grantor (other than any Excluded Assets of a New Grantor); and

(b) it shall comply with, and be subject to, and have the benefit of, all of the terms, conditions, covenants, agreements and obligations set forth in the Collateral Agreement

Without limiting the generality of the foregoing terms of this paragraph 3, each New Grantor hereby, to the extent set forth in Section 2.1 of the Collateral Agreement grants to the Administrative Agent, for the ratable benefit of the Secured Parties, a continuing security interest in, and, to the extent set forth in Section 7.6 of the Collateral Agreement, a right of setoff against, any and all right, title and interest, whether now or hereafter owned or acquired, of each New Grantor in and to the Collateral of such New Grantor.

4. Reaffirmation. Each Loan Party (including the New Loan Parties):

(a) acknowledges, agrees and consents to the transactions set forth in paragraphs 1 through 3 of this Agreement (collectively, the “Joinder Transactions”);

(b) confirms and reaffirms its obligations under the Credit Agreement, as applicable, and each other Loan Document to which it is a party, after giving effect to the Joinder Transactions;

(c) acknowledges and agrees that each reference to the “Credit Agreement,” to the “Guaranty” or to the “Collateral Agreement” as used in any Loan Document shall mean the Credit Agreement, the Guaranty, and the Collateral Agreement, respectively, as supplemented hereby (including by the Joinder Transactions) and as otherwise amended, restated, supplemented or otherwise modified prior to the date hereof; and

(d) agrees that after giving effect to this Agreement and the Joinder Transactions, the Credit Agreement, the Guaranty, the Collateral Agreement and each other Loan Document to which it is a party remain in full force and effect, and each are hereby ratified and confirmed by such Loan Party.

5. Schedules. Attached hereto as Annex A is a supplement to Schedule 5.03 of the Credit Agreement and to each of the Schedules to the Collateral Agreement to the extent such Schedules have changed since the Closing Date or will change as a result of the execution and delivery hereof (which supplements include, as of the date hereof, all information required to be provided therein with respect to the New Loan Parties), in each case as of the date hereof.

6. Notices. All notices and communications to any New Loan Party shall be given to the address of the Borrower set forth in, and otherwise made in accordance with, Section 10.02 of the Credit Agreement, Section 7.2 of the Collateral Agreement and Section 15 of the Guaranty, as applicable.

7. Waiver. Each New Guarantor hereby waives acceptance by the Administrative Agent and the Guaranteed Parties of the guarantee by such New Loan Party under the Guaranty.

8. Advice of Counsel. Each Loan Party (including each New Loan Party) hereby acknowledges that (a) it has been advised by counsel in the negotiation, execution and delivery of this Agreement and the other Loan Documents to which it is a party and (b) it has received a copy of the Credit Agreement and the other Loan Documents and has reviewed and understands the same.

9. Counterparts; Etc. This Agreement may be executed in counterparts (and by different parties hereto in different counterparts), each of which shall constitute an original, but all of which when taken together shall constitute a single contract. Delivery of an executed counterpart of a signature page of this Agreement by telecopy or other electronic imaging means shall be effective as delivery of a manually executed counterpart of this Agreement.

10. Governing Law. This Agreement shall be governed by and construed and interpreted in accordance with the laws of the State of New York.

[Signature Pages Follow]

IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to be duly executed as of the date first above written.

Babcock & Wilcox

Joinder and Reaffirmation Agreement

Babcock & Wilcox

Joinder and Reaffirmation Agreement

Babcock & Wilcox

Joinder and Reaffirmation Agreement

Babcock & Wilcox

Joinder and Reaffirmation Agreement

ANNEX A

Supplemental Schedules

[Attached Hereto]

Schedule 5.03

Ownership of Subsidiaries

SCHEDULE 3.3

TO PLEDGE AND SECURITY AGREEMENT

PERFECTED FIRST PRIORITY LIENS

UCC Filings

A UCC1 Financing Statement listing each Grantor, as debtor, and the Collateral Agent, as secured party, should be filed in the applicable governmental offices set forth below.

Schedule 3.3 – Page 1

To perfect the Lien in Fixtures, a UCC1 Financing Statement listing the applicable Grantor, as debtor, and the Collateral Agent, as secured party, should be filed in the real property records of the county in which such Fixtures are located. Each such UCC1 Financing Statement will need to include a legal description of the real property upon which such Fixtures are located.

Actions with respect to Pledged Securities

The original of all Pledged Securities evidence by either a Certificated Security or Instrument should be delivered to the Collateral Agent, together with an undated stock or note power, as applicable, duly executed in blank by the applicable Grantor.

Actions with respect to Patents and Trademarks

For Collateral consisting of Patents and Trademarks, the applicable Grantors should execute an Intellectual Property Security Agreement, and such agreement should be recorded with the United States Patent and Trademark Office.

Actions with respect to Copyrights

For Collateral consisting of Copyrights, the applicable Grantors should execute an Intellectual Property Security Agreement, and such agreement should be recorded with the United States Copyright Office.

Schedule 3.3 – Page 2

SCHEDULE 3.4

TO PLEDGE AND SECURITY AGREEMENT

NAME; JURISDICTION OF ORGANIZATION, ETC.

Schedule 3.4 – Page 1

Schedule 3.4 – Page 2

Prior Names during last 5 years:

On November 20, 2007, The Babcock & Wilcox Company changed its name to Babcock & Wilcox Power Generation Group, Inc.

On November 20, 2007, The Babcock & Wilcox Companies changed its name to The Babcock & Wilcox Company, and then on March 8, 2010, changed its name to Babcock & Wilcox Investment Company

On April 20, 2010, McDermott Technology, Inc. changed its name to Babcock & Wilcox Technology, Inc.

On April 29, 2010, Babcock & Wilcox Nuclear Power Generation Group, Inc. changed its name to Babcock & Wilcox Nuclear Energy, Inc.

Schedule 3.4 – Page 3

Prior Addresses during last 5 years:

The former chief executive office of Americon Equipment Services, Inc. was located at: 3333 Copley Road, Copley, OH 44321.

The former chief executive office of the following entities was located at 90 E. Tuscarawas Ave., Barberton, OH 44203:

Americon, Inc.

Babcock & Wilcox Construction Co., Inc.

The former chief executive office of the following entities was located at 1450 Poydras Street, New Orleans, LA 70112:

Babcock & Wilcox Equity Investments, Inc.

Babcock & Wilcox Holdings, Inc.

Babcock & Wilcox International Sales and Service Corporation

Babcock & Wilcox International, Inc.

Babcock & Wilcox Investment Company

Babcock & Wilcox Power Generation Group, Inc.

The former chief executive office of the following entities was located at 1415 Louisiana Street, Suite 3500, Houston, TX 77002:

Delta Power Services, LLC

DPS Cadillac, LLC

DPS Florida, LLC

DPS Mojave, LLC

The former chief executive office of the following entities was located at 67 Park Place East, Morristown, NJ 07960:

DPS Berkeley, LLC

DPS Michigan, LLC

The former chief executive office of the following entities was located at 7022 Wild Violet Drive, Humble, TX 77346:

DPS Gregory, LLC

DPS Mecklenburg, LLC

The former chief executive office of DPS Lowell Cogen, LLC was located at: 282 Western Avenue, Lowell, MA 01852

The former chief executive office of DPS Sabine, LLC was located at: 4647 FM1006 at: 4647 FM 1006 at Lanxess Plant, Orange, TX

The former chief executive office of Babcock & Wilcox Investment Company was located at: 800 Main Street, Lynchburg, VA, 25404

Schedule 3.4 – Page 4

SCHEDULE 3.7

TO PLEDGE AND SECURITY AGREEMENT

INVESTMENT PROPERTY

Pledged Stock:

Schedule 3.7 – Page 1

Schedule 3.7 – Page 2

Schedule 3.7 – Page 3

Schedule 3.7 – Page 4

Footnotes

Schedule 3.7 – Page 5

Schedule 3.7 – Page 6

Pledged LLC Interests:

Schedule 3.7 – Page 7

Pledged Partnership Interests:

Babcock & Wilcox Ebensburg Power, Inc. owns a 49.5% general partnership interest in Ebensburg Power Company (which general partnership interest is uncertificated). Babcock & Wilcox Ebensburg Power, Inc. owns a 1% general partnership interest in Ebensburg Investors Limited Partnership (an unaffiliated third party), which in turn owns the other 50.5% general partnership interest in Ebensburg Power Company.

Pledged Trust Interests:

None.

Pledged Notes:

Amended and Restated Global Intercompany Note dated as of August 6, 2010, payable by the New Borrower and certain of its Subsidiaries to the order of New Borrower, as applicable, and certain of its Subsidiaries extending credit thereunder

Pledged Commodities Contracts:

None.

Schedule 3.7 – Page 8