AMENDMENT NO. 9 dated as of October 9, 2009 (this “ Amendment ”), to the CREDIT AGREEMENT dated as of August 2, 2004, as amended pursuant to that certain Incremental Term Loan Assumption Agreement and Amendment No. 1 dated as of April 1, 2005, that certain Incremental Term Loan Assumption Agreement and Amendment No. 2 dated as of March 24, 2006, as amended as of April 21, 2006, that certain Incremental Term Loan Assumption Agreement and Amendment No. 3 dated as of June 30, 2006, that certain Amendment No. 4 dated as of February 6, 2007, that certain Amendment No. 5 dated as of September 30, 2008, that certain Amendment No. 6 dated as of July 29, 2009, that certain Amendment No. 7 dated as of September 25, 2009 and that certain Amendment No. 8 dated as of October 9, 2009 (as so amended, the “ Credit Agreement ”), among ALION SCIENCE AND TECHNOLOGY CORPORATION (the “ Borrower ”), the Subsidiary Guarantors listed on the signature pages hereto, the lenders from time to time party to the Credit Agreement (the “ Lenders ”) and CREDIT SUISSE (formerly known as Credit Suisse First Boston), as administrative agent (in such capacity, the “ Administrative Agent ”) and as collateral agent for the Lenders.

A. Pursuant to the Credit Agreement, the Lenders have extended, and have agreed to extend, credit to the Borrower.

B. The Borrower has requested certain amendments to the Credit Agreement as set forth herein, and the Lenders party hereto have agreed to such request on and subject to the terms and conditions of this Amendment.

Accordingly, in consideration of the mutual agreements herein contained and other good and valuable consideration, the sufficiency and receipt of which are hereby acknowledged, the parties hereto agree as follows:

SECTION 1. Defined Terms; Interpretation; Etc . Capitalized terms used and not defined herein shall have the meanings assigned to such terms in the Credit Agreement. The rules of construction set forth in Section 1.02 of the Credit Agreement shall apply equally to this Amendment. This Amendment shall be a “Loan Document” for all purposes of the Credit Agreement and the other Loan Documents.

SECTION 2. Amendments to Credit Agreement . (a) Section 1.01 of the Credit Agreement is hereby amended as follows:

(i) The following new defined terms are inserted in the appropriate alphabetical order:

“ Incremental Revolving Credit Assumption Agreement ” shall mean an Incremental Revolving Credit Assumption Agreement in form and substance reasonably satisfactory to the Administrative Agent, among the Borrower, the Administrative Agent and one or more Incremental Revolving Credit Lenders.

“ Incremental Revolving Credit Commitment ” shall mean any increased Revolving Credit Commitment provided pursuant to Section 2.24.

“ Incremental Revolving Credit Lender ” shall mean a Lender with an Incremental Revolving Credit Commitment.

“ Incremental Revolving Loan Amount ” shall mean, at any time, the excess, if any, of (a) $25,000,000 over (b) the aggregate amount of all Incremental Revolving Credit Commitments established prior to such time.

“ Liquidity Condition ” shall mean the effectiveness of Incremental Revolving Credit Commitments or other revolving credit commitments available to the Borrower and reasonably acceptable to the Administrative Agent such that the aggregate amount of Revolving Credit Commitments (and such other revolving credit commitments, if any) is at least $35,000,000.

“ Liquidity Condition Date ” shall mean February 1, 2010.

“ Target Leverage Condition ” shall mean, as of the Target Leverage Condition Date, that the Senior Secured Leverage Ratio is less than or equal to 2.75 to 1.00.

“ Target Leverage Condition Date ” shall mean June 30, 2010.

(ii) The following definitions are hereby amended and restated in their entirety as follows:

“ Interest Coverage Ratio ” shall mean, for any period, the ratio of (a) Consolidated EBITDA for such period to (b) Consolidated Interest Expense for such period payable in cash.

“ Revolving Credit Maturity Date ” shall mean September 30, 2010, or such later date as may be agreed to in writing by the Borrower and all the Revolving Credit Lenders.

(iii) The definition of “Loans” is hereby amended by inserting at the end thereof the words “, including any Loans made as a result of the accrual of interest paid in kind pursuant to Section 2.06(d) or (e)”.

(iv) The definition of “Revolving Credit Commitment” is hereby amended by inserting the words “or Incremental Revolving Credit Assumption Agreement” immediately after the words “Assignment and Acceptance” thereof.

(v) The definition of “Revolving Loans” is hereby amended by replacing the reference to “(a)(iii)” therein with “(c)”.

(b) Section 2.06 ( Interest on Loans ) is hereby amended by inserting the following new paragraphs (d) and (e) at the end thereof:

“(d) Subject to the provisions of Section 2.07, if the Borrower has not satisfied the Liquidity Condition by the Liquidity Condition Date, then, from and including the Liquidity Condition Date to but excluding the date on which the Liquidity Condition has been satisfied, all Loans outstanding under this Agreement shall accrue interest at (i) the rate otherwise applicable to such Loan pursuant to this Section 2.06 (as the same may be increased pursuant to paragraph (e) below) plus (ii) 1.00% per annum. The amount of interest accrued pursuant to clause (ii) of this paragraph (d) shall not be payable in cash but be capitalized and added to the principal amount of the Loans outstanding on each Interest Payment Date for such Loans, on the date on which the Liquidity Condition is satisfied and on the date on which such Loans are repaid or prepaid.

(e) Subject to the provisions of this Section 2.07, if the Borrower has not satisfied the Target Leverage Condition by the Target Leverage Condition Date, then, from and including October 1, 2009, to but excluding the date on which the Target Leverage Condition has been satisfied, all Loans outstanding under this Agreement shall accrue interest at (i) the rate otherwise applicable to such Loan pursuant to this Section 2.06 (as the same may be increased pursuant to paragraph (d) above) plus (ii) 1.00% per annum, increasing by 0.50% on the first day of each calendar quarter ending after the Target Leverage Condition Date if the Target Leverage Condition has not been satisfied on such date. The amount of interest accrued pursuant to clause (ii) of this paragraph (f) shall not be payable in cash but be capitalized and added to the principal amount of the Loans outstanding on each Interest Payment Date for such Loans (whether occurring prior to or after the Target Leverage Condition Date), on the date on which the Target Leverage Condition is satisfied and on the date on which such Loans are repaid or prepaid.”

(c) Section 2.23(b) ( Letters of Credit ) is hereby amended by replacing the reference to “$40,000,000” therein with “$20,000,000”.

(d) Section 2.24.